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Yamaguchi J, Andrade MA, Truong TT, Toney GM. Glutamate Spillover Dynamically Strengthens Gabaergic Synaptic Inhibition of the Hypothalamic Paraventricular Nucleus. J Neurosci 2024; 44:e1851222023. [PMID: 38154957 PMCID: PMC10869154 DOI: 10.1523/jneurosci.1851-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 12/16/2023] [Accepted: 12/20/2023] [Indexed: 12/30/2023] Open
Abstract
The hypothalamic paraventricular nucleus (PVN) is strongly inhibited by γ-aminobutyric acid (GABA) from the surrounding peri-nuclear zone (PNZ). Because glutamate mediates fast excitatory transmission and is substrate for GABA synthesis, we tested its capacity to dynamically strengthen GABA inhibition. In PVN slices from male mice, bath glutamate applied during ionotropic glutamate receptor blockade increased PNZ-evoked inhibitory postsynaptic currents (eIPSCs) without affecting GABA-A receptor agonist currents or single-channel conductance, implicating a presynaptic mechanism(s). Consistent with this interpretation, bath glutamate failed to strengthen IPSCs during pharmacological saturation of GABA-A receptors. Presynaptic analyses revealed that glutamate did not affect paired-pulse ratio, peak eIPSC variability, GABA vesicle recycling speed, or readily releasable pool (RRP) size. Notably, glutamate-GABA strengthening (GGS) was unaffected by metabotropic glutamate receptor blockade and graded external Ca2+ when normalized to baseline amplitude. GGS was prevented by pan- but not glial-specific inhibition of glutamate uptake and by inhibition of glutamic acid decarboxylase (GAD), indicating reliance on glutamate uptake by neuronal excitatory amino acid transporter 3 (EAAT3) and enzymatic conversion of glutamate to GABA. EAAT3 immunoreactivity was strongly localized to presumptive PVN GABA terminals. High bath K+ also induced GGS, which was prevented by glutamate vesicle depletion, indicating that synaptic glutamate release strengthens PVN GABA inhibition. GGS suppressed PVN cell firing, indicating its functional significance. In sum, PVN GGS buffers neuronal excitation by apparent "over-filling" of vesicles with GABA synthesized from synaptically released glutamate. We posit that GGS protects against sustained PVN excitation and excitotoxicity while potentially aiding stress adaptation and habituation.
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Affiliation(s)
- Junya Yamaguchi
- Department of Cellular & Integrative Physiology, University of Texas Health San Antonio, San Antonio 78229-3900, Texas
| | - Mary Ann Andrade
- Department of Cellular & Integrative Physiology, University of Texas Health San Antonio, San Antonio 78229-3900, Texas
| | - Tamara T Truong
- Department of Cellular & Integrative Physiology, University of Texas Health San Antonio, San Antonio 78229-3900, Texas
| | - Glenn M Toney
- Department of Cellular & Integrative Physiology, University of Texas Health San Antonio, San Antonio 78229-3900, Texas
- Center for Biomedical Neuroscience, University of Texas Health San Antonio, San Antonio 78229-3900, Texas
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2
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Zsombok A, Desmoulins LD, Derbenev AV. Sympathetic circuits regulating hepatic glucose metabolism: where we stand. Physiol Rev 2024; 104:85-101. [PMID: 37440208 PMCID: PMC11281813 DOI: 10.1152/physrev.00005.2023] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 06/12/2023] [Accepted: 07/10/2023] [Indexed: 07/14/2023] Open
Abstract
The prevalence of metabolic disorders, including type 2 diabetes mellitus, continues to increase worldwide. Although newer and more advanced therapies are available, current treatments are still inadequate and the search for solutions remains. The regulation of energy homeostasis, including glucose metabolism, involves an exchange of information between the nervous systems and peripheral organs and tissues; therefore, developing treatments to alter central and/or peripheral neural pathways could be an alternative solution to modulate whole body metabolism. Liver glucose production and storage are major mechanisms controlling glycemia, and the autonomic nervous system plays an important role in the regulation of hepatic functions. Autonomic nervous system imbalance contributes to excessive hepatic glucose production and thus to the development and progression of type 2 diabetes mellitus. At cellular levels, change in neuronal activity is one of the underlying mechanisms of autonomic imbalance; therefore, modulation of the excitability of neurons involved in autonomic outflow governance has the potential to improve glycemic status. Tissue-specific subsets of preautonomic neurons differentially control autonomic outflow; therefore, detailed information about neural circuits and properties of liver-related neurons is necessary for the development of strategies to regulate liver functions via the autonomic nerves. This review provides an overview of our current understanding of the hypothalamus-ventral brainstem-liver pathway involved in the sympathetic regulation of the liver, outlines strategies to identify organ-related neurons, and summarizes neuronal plasticity during diabetic conditions with a particular focus on liver-related neurons in the paraventricular nucleus.
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Affiliation(s)
- Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana, United States
- Tulane Brain Institute, Tulane University, New Orleans, Louisiana, United States
| | - Lucie D Desmoulins
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana, United States
| | - Andrei V Derbenev
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana, United States
- Tulane Brain Institute, Tulane University, New Orleans, Louisiana, United States
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3
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Kirchner MK, Althammer F, Donaldson KJ, Cox DN, Stern JE. Changes in neuropeptide large dense core vesicle trafficking dynamics contribute to adaptive responses to a systemic homeostatic challenge. iScience 2023; 26:108243. [PMID: 38026155 PMCID: PMC10654599 DOI: 10.1016/j.isci.2023.108243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 08/28/2023] [Accepted: 10/16/2023] [Indexed: 12/01/2023] Open
Abstract
Neuropeptides are packed into large dense core vesicles (LDCVs) that are transported from the soma out into their processes. Limited information exists regarding mechanisms regulating LDCV trafficking, particularly during challenges to bodily homeostasis. Addressing this gap, we used 2-photon imaging in an ex vivo preparation to study LDCVs trafficking dynamics in vasopressin (VP) neurons, which traffic and release neuropeptide from their dendrites and axons. We report a dynamic bidirectional trafficking of VP-LDCVs with important differences in speed and directionality between axons and dendrites. Acute, short-lasting stimuli known to alter VP firing activity and axonal/dendritic release caused modest changes in VP-LDCVs trafficking dynamics. Conversely, chronic/sustained systemic osmotic challenges upregulated VP-LDCVs trafficking dynamic, with a larger effect in dendrites. These results support differential regulation of dendritic and axonal LDCV trafficking, and that changes in trafficking dynamics constitute a novel mechanism by which peptidergic neurons can efficiently adapt to conditions of increased hormonal demand.
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Affiliation(s)
- Matthew K. Kirchner
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA 30303, USA
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
| | - Ferdinand Althammer
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA 30303, USA
- Institute of Human Genetics, Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Kevin J. Donaldson
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
- Center for Neuromics, Georgia State University, Atlanta, GA 30303, USA
| | - Daniel N. Cox
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
- Center for Neuromics, Georgia State University, Atlanta, GA 30303, USA
| | - Javier E. Stern
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA 30303, USA
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
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4
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O’Brien F, Feetham CH, Staunton CA, Hext K, Barrett-Jolley R. Temperature modulates PVN pre-sympathetic neurones via transient receptor potential ion channels. Front Pharmacol 2023; 14:1256924. [PMID: 37920211 PMCID: PMC10618372 DOI: 10.3389/fphar.2023.1256924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 10/03/2023] [Indexed: 11/04/2023] Open
Abstract
The paraventricular nucleus (PVN) of the hypothalamus plays a vital role in maintaining homeostasis and modulates cardiovascular function via autonomic pre-sympathetic neurones. We have previously shown that coupling between transient receptor potential cation channel subfamily V Member 4 (Trpv4) and small-conductance calcium-activated potassium channels (SK) in the PVN facilitate osmosensing, but since TRP channels are also thermosensitive, in this report we investigated the temperature sensitivity of these neurones. Methods: TRP channel mRNA was quantified from mouse PVN with RT-PCR and thermosensitivity of Trpv4-like PVN neuronal ion channels characterised with cell-attached patch-clamp electrophysiology. Following recovery of temperature-sensitive single-channel kinetic schema, we constructed a predictive stochastic mathematical model of these neurones and validated this with electrophysiological recordings of action current frequency. Results: 7 thermosensitive TRP channel genes were found in PVN punches. Trpv4 was the most abundant of these and was identified at the single channel level on PVN neurones. We investigated the thermosensitivity of these Trpv4-like channels; open probability (Po) markedly decreased when temperature was decreased, mediated by a decrease in mean open dwell times. Our neuronal model predicted that PVN spontaneous action current frequency (ACf) would increase as temperature is decreased and in our electrophysiological experiments, we found that ACf from PVN neurones was significantly higher at lower temperatures. The broad-spectrum channel blocker gadolinium (100 µM), was used to block the warm-activated, Ca2+-permeable Trpv4 channels. In the presence of gadolinium (100 µM), the temperature effect was largely retained. Using econazole (10 µM), a blocker of Trpm2, we found there were significant increases in overall ACf and the temperature effect was inhibited. Conclusion: Trpv4, the abundantly transcribed thermosensitive TRP channel gene in the PVN appears to contribute to intrinsic thermosensitive properties of PVN neurones. At physiological temperatures (37°C), we observed relatively low ACf primarily due to the activity of Trpm2 channels, whereas at room temperature, where most of the previous characterisation of PVN neuronal activity has been performed, ACf is much higher, and appears to be predominately due to reduced Trpv4 activity. This work gives insight into the fundamental mechanisms by which the body decodes temperature signals and maintains homeostasis.
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Affiliation(s)
| | | | | | | | - Richard Barrett-Jolley
- Department of Musculoskeletal Ageing Science, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, United Kingdom
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5
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Ruyle BC, Lima-Silveira L, Martinez D, Cummings KJ, Heesch CM, Kline DD, Hasser EM. Paraventricular nucleus projections to the nucleus tractus solitarii are essential for full expression of hypoxia-induced peripheral chemoreflex responses. J Physiol 2023; 601:4309-4336. [PMID: 37632733 DOI: 10.1113/jp284907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 07/13/2023] [Indexed: 08/28/2023] Open
Abstract
The hypothalamic paraventricular nucleus (PVN) is essential to peripheral chemoreflex neurocircuitry, but the specific efferent pathways utilized are not well defined. The PVN sends dense projections to the nucleus tractus solitarii (nTS), which exhibits neuronal activation following a hypoxic challenge. We hypothesized that nTS-projecting PVN (PVN-nTS) neurons contribute to hypoxia-induced nTS neuronal activation and cardiorespiratory responses. To selectively target PVN-nTS neurons, rats underwent bilateral nTS nanoinjection of retrogradely transported adeno-associated virus (AAV) driving Cre recombinase expression. We then nanoinjected into PVN AAVs driving Cre-dependent expression of Gq or Gi designer receptors exclusively activated by designer drugs (DREADDs) to test the degree that selective activation or inhibition, respectively, of the PVN-nTS pathway affects the hypoxic ventilatory response (HVR) of conscious rats. We used immunohistochemistry for Fos and extracellular recordings to examine how DREADD activation influences PVN-nTS neuronal activation by hypoxia. Pathway activation enhanced the HVR at moderate hypoxic intensities and increased PVN and nTS Fos immunoreactivity in normoxia and hypoxia. In contrast, PVN-nTS inhibition reduced both the HVR and PVN and nTS neuronal activation following hypoxia. To further confirm selective pathway effects on central cardiorespiratory output, rats underwent hypoxia before and after bilateral nTS nanoinjections of C21 to activate or inhibit PVN-nTS terminals. PVN terminal activation within the nTS enhanced tachycardic, sympathetic and phrenic (PhrNA) nerve activity responses to hypoxia whereas inhibition attenuated hypoxia-induced increases in nTS neuronal action potential discharge and PhrNA. The results demonstrate the PVN-nTS pathway enhances nTS neuronal activation and is necessary for full cardiorespiratory responses to hypoxia. KEY POINTS: The hypothalamic paraventricular nucleus (PVN) contributes to peripheral chemoreflex cardiorespiratory responses, but specific PVN efferent pathways are not known. The nucleus tractus solitarii (nTS) is the first integration site of the peripheral chemoreflex, and the nTS receives dense projections from the PVN. Selective GqDREADD activation of the PVN-nTS pathway was shown to enhance ventilatory responses to hypoxia and activation (Fos immunoreactivity (IR)) of nTS neurons in conscious rats, augmenting the sympathetic and phrenic nerve activity (SSNA and PhrNA) responses to hypoxia in anaesthetized rats. Selective GiDREADD inhibition of PVN-nTS neurons attenuates ventilatory responses, nTS neuronal Fos-IR, action potential discharge and PhrNA responses to hypoxia. These results demonstrate that a projection from the PVN to the nTS is critical for full chemoreflex responses to hypoxia.
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Affiliation(s)
- Brian C Ruyle
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
| | - Ludmila Lima-Silveira
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - Diana Martinez
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - Kevin J Cummings
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - Cheryl M Heesch
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - David D Kline
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, USA
| | - Eileen M Hasser
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, USA
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6
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Althammer F. Heralding a new era of oxytocinergic research: New tools, new problems? J Neuroendocrinol 2023; 35:e13333. [PMID: 37621199 DOI: 10.1111/jne.13333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 08/10/2023] [Accepted: 08/10/2023] [Indexed: 08/26/2023]
Abstract
According to classic neuroendocrinology, hypothalamic oxytocin cells can be categorized into parvo- and magnocellular neurons. However, research in the last decade provided ample evidence that this black-and-white model of oxytocin neurons is most likely oversimplified. Novel genetic, functional and morphological studies indicate that oxytocin neurons might be organized in functional modules and suggest the existence of five or more distinct oxytocinergic subpopulations. However, many of these novel, automated high-throughput techniques might be inherently biased and interpretation of acquired data needs to be approached with caution to enable drawing sound and reliable conclusions. In addition, the recent finding that astrocytes in various brain regions express functional oxytocin receptors represents a paradigm shift and challenges the view that oxytocin primarily acts as a direct peptidergic neurotransmitter. This review highlights the latest technical advances in oxytocinergic research, puts recent studies on the oxytocin system into context and formulates various provocative ideas based on novel findings that challenges various prevailing hypotheses and dogmas about oxytocinergic modulation.
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Affiliation(s)
- Ferdinand Althammer
- Institute of Human Genetics, Heidelberg University Hospital, Heidelberg, Germany
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7
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Molinas AJR, Desmoulins LD, Davis RK, Gao H, Satou R, Derbenev AV, Zsombok A. High-Fat Diet Modulates the Excitability of Neurons within the Brain-Liver Pathway. Cells 2023; 12:1194. [PMID: 37190103 PMCID: PMC10137256 DOI: 10.3390/cells12081194] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 04/14/2023] [Accepted: 04/16/2023] [Indexed: 05/17/2023] Open
Abstract
Stimulation of hepatic sympathetic nerves increases glucose production and glycogenolysis. Activity of pre-sympathetic neurons in the paraventricular nucleus (PVN) of the hypothalamus and in the ventrolateral and ventromedial medulla (VLM/VMM) largely influence the sympathetic output. Increased activity of the sympathetic nervous system (SNS) plays a role in the development and progression of metabolic diseases; however, despite the importance of the central circuits, the excitability of pre-sympathetic liver-related neurons remains to be determined. Here, we tested the hypothesis that the activity of liver-related neurons in the PVN and VLM/VMM is altered in diet-induced obese mice, as well as their response to insulin. Patch-clamp recordings were conducted from liver-related PVN neurons, VLM-projecting PVN neurons, and pre-sympathetic liver-related neurons in the ventral brainstem. Our data demonstrate that the excitability of liver-related PVN neurons increased in high-fat diet (HFD)-fed mice compared to mice fed with control diet. Insulin receptor expression was detected in a population of liver-related neurons, and insulin suppressed the firing activity of liver-related PVN and pre-sympathetic VLM/VMM neurons in HFD mice; however, it did not affect VLM-projecting liver-related PVN neurons. These findings further suggest that HFD alters the excitability of pre-autonomic neurons as well as their response to insulin.
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Affiliation(s)
- Adrien J. R. Molinas
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA 70130, USA; (A.J.R.M.); (L.D.D.); (R.K.D.); (R.S.); (A.V.D.)
| | - Lucie D. Desmoulins
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA 70130, USA; (A.J.R.M.); (L.D.D.); (R.K.D.); (R.S.); (A.V.D.)
| | - Roslyn K. Davis
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA 70130, USA; (A.J.R.M.); (L.D.D.); (R.K.D.); (R.S.); (A.V.D.)
| | - Hong Gao
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA 70130, USA; (A.J.R.M.); (L.D.D.); (R.K.D.); (R.S.); (A.V.D.)
| | - Ryousuke Satou
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA 70130, USA; (A.J.R.M.); (L.D.D.); (R.K.D.); (R.S.); (A.V.D.)
| | - Andrei V. Derbenev
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA 70130, USA; (A.J.R.M.); (L.D.D.); (R.K.D.); (R.S.); (A.V.D.)
- Tulane Brain Institute, Tulane University, New Orleans, LA 70130, USA
| | - Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA 70130, USA; (A.J.R.M.); (L.D.D.); (R.K.D.); (R.S.); (A.V.D.)
- Tulane Brain Institute, Tulane University, New Orleans, LA 70130, USA
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8
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Korogod SM, Stern JE, Cymbalyuk GS. Microgeometrical dendritic factors predict electrical decoupling between somatic and dendritic compartments in magnocellular neurosecretory neurons. Front Cell Neurosci 2023; 17:1125029. [PMID: 37032839 PMCID: PMC10081025 DOI: 10.3389/fncel.2023.1125029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 03/06/2023] [Indexed: 04/11/2023] Open
Abstract
It is generally assumed that dendritic release of neuropeptides from magnocellular neurosecretory neurons (MNNs), a critical process involved in homeostatic functions, is an activity-dependent process that requires backpropagating action potentials (APs). Still, growing evidence indicates that dendritic release can occur in the absence of APs, and axonal APs have been shown to fail to evoke dendritic release. These inconsistencies strongly suggest that APs in MNNs may fail to backpropagating into dendrites. Here we tested whether simple factors of electrical signal attenuation could lead to effective decoupling between cell's body and dendritic release site within typical geometrical characteristics of MNN. We developed a family of linear mathematical models of MNNs and evaluated whether the somato-dendritic transfer of electrical signals is influenced by the geometrical characteristics. We determined the prerequisites for critically strong dendritic attenuation of the somatic input which are sufficient to explain the failure of APs initiated in the soma to backpropagating into dendritic compartments. Being measured in 100 μm from soma voltage attenuations down to 0.1 and 0.01 of the input value were chosen as the markers of electrical decoupling of dendritic sites from the soma, considering 0.1 insufficient for triggering dendritic spikes and 0.01 indistinguishable from background noise. The tested micro-geometrical factors were the dendritic stem diameter, varicosities, and size of peri-dendritic space limited by glial sheath wrapping. Varicosities increased the attenuation along homogeneous proximal dendrites by providing an increased current leak at the junction with the proximal dendritic section. The glial sheath wrapping a dendrite section promoted greater attenuation by increasing longitudinal resistance of the interstitial peri-dendritic space thus playing the insulating role. These decoupling effects were strengthened in the case of the dendritic stems with thinner diameters of and/or increased conductivity of the membrane. These micro-geometrical factors are biophysically realistic and predict electrical decoupling between somatic and dendritic compartments in MNNs.
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Affiliation(s)
- Sergiy M. Korogod
- The Neuroscience Institute, Georgia State University, Atlanta, GA, United States
- Department of Molecular Biophysics, O. O. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine
| | - Javier E. Stern
- The Neuroscience Institute, Georgia State University, Atlanta, GA, United States
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA, United States
| | - Gennady S. Cymbalyuk
- The Neuroscience Institute, Georgia State University, Atlanta, GA, United States
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA, United States
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9
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Jiang Y, Rezai-Zadeh K, Desmoulins LD, Muenzberg H, Derbenev AV, Zsombok A. GABAergic leptin receptor-expressing neurons in the dorsomedial hypothalamus project to brown adipose tissue-related neurons in the paraventricular nucleus of mice. Auton Neurosci 2023; 245:103058. [PMID: 36538864 PMCID: PMC9899324 DOI: 10.1016/j.autneu.2022.103058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 11/14/2022] [Accepted: 12/08/2022] [Indexed: 12/15/2022]
Abstract
Brown adipose tissue (BAT) contributes to energy homeostasis via nonshivering thermogenesis. The BAT is densely innervated by the sympathetic nervous system (SNS) and activity of pre-autonomic neurons modulates the sympathetic outflow. Leptin, an adipocyte hormone, alters energy homeostasis and thermogenesis of BAT via several neuronal circuits; however, the cellular effects of leptin on interscapular BAT (iBAT)-related neurons in the hypothalamus remain to be determined. In this study, we used pseudorabies virus (PRV) to identify iBAT-related neurons in the paraventricular nucleus (PVN) of the hypothalamus and test the hypothesis that iBAT-related PVN neurons are modulated by leptin. Inoculation of iBAT with PRV in leptin receptor reporter mice (Lepr:EGFP) demonstrated that a population of iBAT-related PVN neurons expresses Lepr receptors. Our electrophysiological findings revealed that leptin application caused hyperpolarization in some of iBAT-related PVN neurons. Bath application of leptin also modulated excitatory and inhibitory neurotransmission to most of iBAT-related PVN neurons. Using channel rhodopsin assisted circuit mapping we found that GABAergic and glutamatergic Lepr-expressing neurons in the dorsomedial hypothalamus/dorsal hypothalamic area (dDMH/DHA) project to PVN neurons; however, connected iBAT-related PVN neurons receive exclusively inhibitory signals from Lepr-expressing dDMH/DHA neurons.
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Affiliation(s)
- Yanyan Jiang
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA, United States of America; Neuroscience Program, Tulane Brain Institute, Tulane University, New Orleans, LA, United States of America
| | - Kavon Rezai-Zadeh
- Central Leptin Signaling, Pennington Biomedical Research Center, LSU System, Baton Rouge, LA, United States of America
| | - Lucie D Desmoulins
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA, United States of America
| | - Heike Muenzberg
- Central Leptin Signaling, Pennington Biomedical Research Center, LSU System, Baton Rouge, LA, United States of America
| | - Andrei V Derbenev
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA, United States of America; Neuroscience Program, Tulane Brain Institute, Tulane University, New Orleans, LA, United States of America
| | - Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA, United States of America; Neuroscience Program, Tulane Brain Institute, Tulane University, New Orleans, LA, United States of America.
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10
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Deng Y, Dickey JE, Saito K, Deng G, Singh U, Jiang J, Toth BA, Zhu Z, Zingman LV, Resch JM, Grobe JL, Cui H. Elucidating the role of Rgs2 expression in the PVN for metabolic homeostasis in mice. Mol Metab 2022; 66:101622. [PMID: 36307046 PMCID: PMC9638802 DOI: 10.1016/j.molmet.2022.101622] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 10/09/2022] [Accepted: 10/21/2022] [Indexed: 11/06/2022] Open
Abstract
OBJECTIVE RGS2 is a GTPase activating protein that modulates GPCR-Gα signaling and mice lacking RGS2 globally exhibit metabolic alterations. While RGS2 is known to be broadly expressed throughout the body including the brain, the relative contribution of brain RGS2 to metabolic homeostasis remains unknown. The purpose of this study was to characterize RGS2 expression in the paraventricular nucleus of hypothalamus (PVN) and test its role in metabolic homeostasis. METHODS We used a combination of RNAscope in situ hybridization (ISH), immunohistochemistry, and bioinformatic analyses to characterize the pattern of Rgs2 expression in the PVN. We then created mice lacking Rgs2 either prenatally or postnatally in the PVN and evaluated their metabolic consequences. RESULTS RNAscope ISH analysis revealed a broad but regionally enriched Rgs2 mRNA expression throughout the mouse brain, with the highest expression being observed in the PVN along with several other brain regions, such as the arcuate nucleus of hypothalamus and the dorsal raphe nucleus. Within the PVN, we found that Rgs2 is specifically enriched in CRH+ endocrine neurons and is further increased by calorie restriction. Functionally, although Sim1-Cre-mediated prenatal deletion of Rgs2 in PVN neurons had no major effects on metabolic homeostasis, AAV-mediated adult deletion of Rgs2 in the PVN led to significantly increased food intake, body weight (both fat and fat-free masses), body length, and blood glucose levels in both male and female mice. Strikingly, we found that prolonged postnatal loss of Rgs2 leads to neuronal cell death in the PVN, while rapid body weight gain in the early phase of viral-mediated PVN Rgs2 deletion is independent of PVN neuronal loss. CONCLUSIONS Our results provide the first evidence to show that PVN Rgs2 expression is not only sensitive to metabolic challenge but also critically required for PVN endocrine neurons to function and maintain metabolic homeostasis.
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Affiliation(s)
- Yue Deng
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Jacob E Dickey
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Kenji Saito
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Guorui Deng
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Uday Singh
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Jingwei Jiang
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Brandon A Toth
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Zhiyong Zhu
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Leonid V Zingman
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, United States; Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Jon M Resch
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, United States; Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, Iowa City, IA, United States; F.O.E. Diabetes Research Center, University of Iowa Carver College of Medicine, Iowa City, IA, United States
| | - Justin L Grobe
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA; Comprehensive Rodent Metabolic Phenotyping Core, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Huxing Cui
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA, United States; Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, Iowa City, IA, United States; F.O.E. Diabetes Research Center, University of Iowa Carver College of Medicine, Iowa City, IA, United States.
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11
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Herrera Moro Chao D, Kirchner MK, Pham C, Foppen E, Denis RGP, Castel J, Morel C, Montalban E, Hassouna R, Bui LC, Renault J, Mouffle C, García-Cáceres C, Tschöp MH, Li D, Martin C, Stern JE, Luquet SH. Hypothalamic astrocytes control systemic glucose metabolism and energy balance. Cell Metab 2022; 34:1532-1547.e6. [PMID: 36198294 PMCID: PMC9615252 DOI: 10.1016/j.cmet.2022.09.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 06/23/2022] [Accepted: 09/02/2022] [Indexed: 01/29/2023]
Abstract
The hypothalamus is key in the control of energy balance. However, strategies targeting hypothalamic neurons have failed to provide viable options to treat most metabolic diseases. Conversely, the role of astrocytes in systemic metabolic control has remained largely unexplored. Here, we show that obesity promotes anatomically restricted remodeling of hypothalamic astrocyte activity. In the paraventricular nucleus (PVN) of the hypothalamus, chemogenetic manipulation of astrocytes results in bidirectional control of neighboring neuron activity, autonomic outflow, glucose metabolism, and energy balance. This process recruits a mechanism involving the astrocytic control of ambient glutamate levels, which becomes defective in obesity. Positive or negative chemogenetic manipulation of PVN astrocyte Ca2+ signals, respectively, worsens or improves metabolic status of diet-induced obese mice. Collectively, these findings highlight a yet unappreciated role for astrocytes in the direct control of systemic metabolism and suggest potential targets for anti-obesity strategy.
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Affiliation(s)
| | - Matthew K Kirchner
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA; Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA 30302, USA
| | - Cuong Pham
- Institute of Biology Paris Seine, Neuroscience Paris Seine, CNRS UMR8246, INSERM U1130, Sorbonne Universite, Paris 75005, France
| | - Ewout Foppen
- Université Paris Cité, CNRS, Unité de Biologie Fonctionnelle et Adaptative, Paris, France
| | - Raphael G P Denis
- Université Paris Cité, CNRS, Unité de Biologie Fonctionnelle et Adaptative, Paris, France; Institut Cochin, Université Paris Cité, INSERM U1016, CNRS UMR 8104, 75014 Paris, France
| | - Julien Castel
- Université Paris Cité, CNRS, Unité de Biologie Fonctionnelle et Adaptative, Paris, France
| | - Chloe Morel
- Université Paris Cité, CNRS, Unité de Biologie Fonctionnelle et Adaptative, Paris, France
| | - Enrica Montalban
- Université Paris Cité, CNRS, Unité de Biologie Fonctionnelle et Adaptative, Paris, France
| | - Rim Hassouna
- Université Paris Cité, CNRS, Unité de Biologie Fonctionnelle et Adaptative, Paris, France
| | - Linh-Chi Bui
- Université Paris Cité, CNRS, Unité de Biologie Fonctionnelle et Adaptative, Paris, France
| | - Justine Renault
- Université Paris Cité, CNRS, Unité de Biologie Fonctionnelle et Adaptative, Paris, France
| | - Christine Mouffle
- Institute of Biology Paris Seine, Neuroscience Paris Seine, CNRS UMR8246, INSERM U1130, Sorbonne Universite, Paris 75005, France
| | - Cristina García-Cáceres
- Helmholtz Diabetes Center (HDC) & German Center for Diabetes Research (DZD), Helmholtz Zentrum München, Neuherberg, 85764, Germany; Division of Metabolic Diseases, Technische Universität München, Munich, 80333, Germany; Medizinische Klinik and Poliklinik IV, Klinikum der Universität, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Matthias H Tschöp
- Helmholtz Diabetes Center (HDC) & German Center for Diabetes Research (DZD), Helmholtz Zentrum München, Neuherberg, 85764, Germany; Division of Metabolic Diseases, Technische Universität München, Munich, 80333, Germany
| | - Dongdong Li
- Institute of Biology Paris Seine, Neuroscience Paris Seine, CNRS UMR8246, INSERM U1130, Sorbonne Universite, Paris 75005, France
| | - Claire Martin
- Université Paris Cité, CNRS, Unité de Biologie Fonctionnelle et Adaptative, Paris, France
| | - Javier E Stern
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA; Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA 30302, USA
| | - Serge H Luquet
- Université Paris Cité, CNRS, Unité de Biologie Fonctionnelle et Adaptative, Paris, France.
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12
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Oxytocin-based therapies for treatment of Prader-Willi and Schaaf-Yang syndromes: evidence, disappointments, and future research strategies. Transl Psychiatry 2022; 12:318. [PMID: 35941105 PMCID: PMC9360032 DOI: 10.1038/s41398-022-02054-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 06/23/2022] [Accepted: 07/01/2022] [Indexed: 11/09/2022] Open
Abstract
The prosocial neuropeptide oxytocin is being developed as a potential treatment for various neuropsychiatric disorders including autism spectrum disorder (ASD). Early studies using intranasal oxytocin in patients with ASD yielded encouraging results and for some time, scientists and affected families placed high hopes on the use of intranasal oxytocin for behavioral therapy in ASD. However, a recent Phase III trial obtained negative results using intranasal oxytocin for the treatment of behavioral symptoms in children with ASD. Given the frequently observed autism-like behavioral phenotypes in Prader-Willi and Schaaf-Yang syndromes, it is unclear whether oxytocin treatment represents a viable option to treat behavioral symptoms in these diseases. Here we review the latest findings on intranasal OT treatment, Prader-Willi and Schaaf-Yang syndromes, and propose novel research strategies for tailored oxytocin-based therapies for affected individuals. Finally, we propose the critical period theory, which could explain why oxytocin-based treatment seems to be most efficient in infants, but not adolescents.
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13
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Bi Q, Wang C, Cheng G, Chen N, Wei B, Liu X, Li L, Lu C, He J, Weng Y, Yin C, Lin Y, Wan S, Zhao L, Xu J, Wang Y, Gu Y, Shen XZ, Shi P. Microglia-derived PDGFB promotes neuronal potassium currents to suppress basal sympathetic tonicity and limit hypertension. Immunity 2022; 55:1466-1482.e9. [PMID: 35863346 DOI: 10.1016/j.immuni.2022.06.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 04/05/2022] [Accepted: 06/22/2022] [Indexed: 12/18/2022]
Abstract
Although many studies have addressed the regulatory circuits affecting neuronal activities, local non-synaptic mechanisms that determine neuronal excitability remain unclear. Here, we found that microglia prevented overactivation of pre-sympathetic neurons in the hypothalamic paraventricular nucleus (PVN) at steady state. Microglia constitutively released platelet-derived growth factor (PDGF) B, which signaled via PDGFRα on neuronal cells and promoted their expression of Kv4.3, a key subunit that conducts potassium currents. Ablation of microglia, conditional deletion of microglial PDGFB, or suppression of neuronal PDGFRα expression in the PVN elevated the excitability of pre-sympathetic neurons and sympathetic outflow, resulting in a profound autonomic dysfunction. Disruption of the PDGFBMG-Kv4.3Neuron pathway predisposed mice to develop hypertension, whereas central supplementation of exogenous PDGFB suppressed pressor response when mice were under hypertensive insult. Our results point to a non-immune action of resident microglia in maintaining the balance of sympathetic outflow, which is important in preventing cardiovascular diseases.
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Affiliation(s)
- Qianqian Bi
- Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China; Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Chao Wang
- Center of Stem Cell and Regenerative Medicine and Department of Neurology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China; NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Science & Brain-Machine Integration, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Guo Cheng
- Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China; Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Ningting Chen
- Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China; Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Bo Wei
- Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China; Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Xiaoli Liu
- Department of Neurology, Affiliated Zhejiang Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Li Li
- Department of Pharmacy, Affiliated Zhejiang Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310013, China
| | - Cheng Lu
- Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China; Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Jian He
- Department of Physiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Yuancheng Weng
- Department of Physiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Chunyou Yin
- Department of Physiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Yunfan Lin
- Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Haining, Zhejiang 314400, China
| | - Shu Wan
- Brain Center, Affiliated Zhejiang Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Li Zhao
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Jiaxi Xu
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, Xi'an, Shanxi 710061, China
| | - Yi Wang
- Department of Pharmacology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Yan Gu
- Center of Stem Cell and Regenerative Medicine and Department of Neurology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China; NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Science & Brain-Machine Integration, Zhejiang University, Hangzhou, Zhejiang 310058, China.
| | - Xiao Z Shen
- Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China; Department of Physiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China.
| | - Peng Shi
- Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China; Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China.
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14
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Roy RK, Ferreira-Neto HC, Felder RB, Stern JE. Angiotensin II inhibits the A-type K + current of hypothalamic paraventricular nucleus neurons in rats with heart failure: role of MAPK-ERK1/2 signaling. Am J Physiol Regul Integr Comp Physiol 2022; 322:R526-R534. [PMID: 35319903 PMCID: PMC9076419 DOI: 10.1152/ajpregu.00308.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 03/03/2022] [Accepted: 03/18/2022] [Indexed: 11/22/2022]
Abstract
Angiotensin II (ANG II)-mediated sympathohumoral activation constitutes a pathophysiological mechanism in heart failure (HF). Although the hypothalamic paraventricular nucleus (PVN) is a major site mediating ANG II effects in HF, the precise mechanisms by which ANG II influences sympathohumoral outflow from the PVN remain unknown. ANG II activates the ubiquitous intracellular MAPK signaling cascades, and recent studies revealed a key role for ERK1/2 MAPK signaling in ANG II-mediated sympathoexcitation in HF rats. Importantly, ERK1/2 was reported to inhibit the transient outward potassium current (IA) in hippocampal neurons. Given that IA is a critical determinant of the PVN neuronal excitability, and that downregulation of IA in the brain has been reported in cardiovascular disease states, including HF, we investigated here whether ANG II modulates IA in PVN neurons via the MAPK-ERK pathway, and, whether these effects are altered in HF rats. Patch-clamp recordings from identified magnocellular neurosecretory neurons (MNNs) and presympathetic (PS) PVN neurons revealed that ANG II inhibited IA in both PVN neuronal types, both in sham and HF rats. Importantly, ANG II effects were blocked by inhibiting MAPK-ERK signaling as well as by inhibiting epidermal growth factor receptor (EGFR), a gateway to MAPK-ERK signaling. Although no differences in basal IA magnitude were found between sham and HF rats under normal conditions, MAPK-ERK blockade resulted in significantly larger IA in both PVN neuronal types in HF rats. Taken together, our studies show that ANG II-induced ERK1/2 activity inhibits IA, an effect expected to increase the excitability of presympathetic and neuroendocrine PVN neurons, contributing in turn to the neurohumoral overactivity that promotes progression of the HF syndrome.
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Affiliation(s)
- Ranjan K Roy
- Neuroscience Institute, Georgia State University, Atlanta, Georgia
| | | | - Robert B Felder
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa
| | - Javier E Stern
- Neuroscience Institute, Georgia State University, Atlanta, Georgia
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15
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Savić B, Murphy D, Japundžić-Žigon N. The Paraventricular Nucleus of the Hypothalamus in Control of Blood Pressure and Blood Pressure Variability. Front Physiol 2022; 13:858941. [PMID: 35370790 PMCID: PMC8966844 DOI: 10.3389/fphys.2022.858941] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 02/15/2022] [Indexed: 12/26/2022] Open
Abstract
The paraventricular nucleus (PVN) is a highly organized structure of the hypothalamus that has a key role in regulating cardiovascular and osmotic homeostasis. Functionally, the PVN is divided into autonomic and neuroendocrine (neurosecretory) compartments, both equally important for maintaining blood pressure (BP) and body fluids in the physiological range. Neurosecretory magnocellular neurons (MCNs) of the PVN are the main source of the hormones vasopressin (VP), responsible for water conservation and hydromineral balance, and oxytocin (OT), involved in parturition and milk ejection during lactation. Further, neurosecretory parvocellular neurons (PCNs) take part in modulation of the hypothalamic–pituitary–adrenal axis and stress responses. Additionally, the PVN takes central place in autonomic adjustment of BP to environmental challenges and contributes to its variability (BPV), underpinning the PVN as an autonomic master controller of cardiovascular function. Autonomic PCNs of the PVN modulate sympathetic outflow toward heart, blood vessels and kidneys. These pre-autonomic neurons send projections to the vasomotor nucleus of rostral ventrolateral medulla and to intermediolateral column of the spinal cord, where postganglionic fibers toward target organs arise. Also, PVN PCNs synapse with NTS neurons which are the end-point of baroreceptor primary afferents, thus, enabling the PVN to modify the function of baroreflex. Neuroendocrine and autonomic parts of the PVN are segregated morphologically but they work in concert when the organism is exposed to environmental challenges via somatodendritically released VP and OT by MCNs. The purpose of this overview is to address both neuroendocrine and autonomic PVN roles in BP and BPV regulation.
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Affiliation(s)
- Bojana Savić
- Laboratory for Cardiovascular Pharmacology and Toxicology, Faculty of Medicine, Institute of Pharmacology, Clinical Pharmacology and Toxicology, University of Belgrade, Belgrade, Serbia
| | - David Murphy
- Molecular Neuroendocrinology Research Group, Bristol Medical School, Translational Health Sciences, University of Bristol, Bristol, United Kingdom
| | - Nina Japundžić-Žigon
- Laboratory for Cardiovascular Pharmacology and Toxicology, Faculty of Medicine, Institute of Pharmacology, Clinical Pharmacology and Toxicology, University of Belgrade, Belgrade, Serbia
- *Correspondence: Nina Japundžić-Žigon,
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16
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Rønnekleiv OK, Qiu J, Kelly MJ. Hypothalamic Kisspeptin Neurons and the Control of Homeostasis. Endocrinology 2022; 163:bqab253. [PMID: 34953135 PMCID: PMC8758343 DOI: 10.1210/endocr/bqab253] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Indexed: 12/27/2022]
Abstract
Hypothalamic kisspeptin (Kiss1) neurons provide indispensable excitatory transmission to gonadotropin-releasing hormone (GnRH) neurons for the coordinated release of gonadotropins, estrous cyclicity, and ovulation. But maintaining reproductive functions is metabolically demanding so there must be a coordination with multiple homeostatic functions, and it is apparent that Kiss1 neurons play that role. There are 2 distinct populations of hypothalamic Kiss1 neurons, namely arcuate nucleus (Kiss1ARH) neurons and anteroventral periventricular and periventricular nucleus (Kiss1AVPV/PeN) neurons in rodents, both of which excite GnRH neurons via kisspeptin release but are differentially regulated by ovarian steroids. Estradiol (E2) increases the expression of kisspeptin in Kiss1AVPV/PeN neurons but decreases its expression in Kiss1ARH neurons. Also, Kiss1ARH neurons coexpress glutamate and Kiss1AVPV/PeN neurons coexpress gamma aminobutyric acid (GABA), both of which are upregulated by E2 in females. Also, Kiss1ARH neurons express critical metabolic hormone receptors, and these neurons are excited by insulin and leptin during the fed state. Moreover, Kiss1ARH neurons project to and excite the anorexigenic proopiomelanocortin neurons but inhibit the orexigenic neuropeptide Y/Agouti-related peptide neurons, highlighting their role in regulating feeding behavior. Kiss1ARH and Kiss1AVPV/PeN neurons also project to the preautonomic paraventricular nucleus (satiety) neurons and the dorsomedial nucleus (energy expenditure) neurons to differentially regulate their function via glutamate and GABA release, respectively. Therefore, this review will address not only how Kiss1 neurons govern GnRH release, but how they control other homeostatic functions through their peptidergic, glutamatergic and GABAergic synaptic connections, providing further evidence that Kiss1 neurons are the key neurons coordinating energy states with reproduction.
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Affiliation(s)
- Oline K Rønnekleiv
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR 97239, USA
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR 97006, USA
| | - Jian Qiu
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR 97239, USA
| | - Martin J Kelly
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR 97239, USA
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR 97006, USA
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17
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Roy RK, Althammer F, Seymour AJ, Du W, Biancardi VC, Hamm JP, Filosa JA, Brown CH, Stern JE. Inverse neurovascular coupling contributes to positive feedback excitation of vasopressin neurons during a systemic homeostatic challenge. Cell Rep 2021; 37:109925. [PMID: 34731601 PMCID: PMC9488983 DOI: 10.1016/j.celrep.2021.109925] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 08/09/2021] [Accepted: 10/12/2021] [Indexed: 01/03/2023] Open
Abstract
Neurovascular coupling (NVC), the process that links neuronal activity to cerebral blood flow changes, has been mainly studied in superficial brain areas, namely the neocortex. Whether the conventional, rapid, and spatially restricted NVC response can be generalized to deeper and functionally diverse brain regions remains unknown. Implementing an approach for in vivo two-photon imaging from the ventral surface of the brain, we show that a systemic homeostatic challenge, acute salt loading, progressively increases hypothalamic vasopressin (VP) neuronal firing and evokes a vasoconstriction that reduces local blood flow. Vasoconstrictions are blocked by topical application of a VP receptor antagonist or tetrodotoxin, supporting mediation by activity-dependent, dendritically released VP. Salt-induced inverse NVC results in a local hypoxic microenvironment, which evokes positive feedback excitation of VP neurons. Our results reveal a physiological mechanism by which inverse NVC responses regulate systemic homeostasis, further supporting the notion of brain heterogeneity in NVC responses.
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Affiliation(s)
- Ranjan K Roy
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | | | | | - Wenting Du
- Department of Physiology, Augusta University, Augusta, GA, USA
| | - Vinicia C Biancardi
- Department of Anatomy, Physiology and Pharmacology, Auburn University, Auburn, AL, USA
| | - Jordan P Hamm
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | | | - Colin H Brown
- Department of Physiology, University of Otago, Dunedin, New Zealand
| | - Javier E Stern
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA.
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18
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Francis N, Borniger JC. Cancer as a homeostatic challenge: the role of the hypothalamus. Trends Neurosci 2021; 44:903-914. [PMID: 34561122 PMCID: PMC9901368 DOI: 10.1016/j.tins.2021.08.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 08/16/2021] [Accepted: 08/30/2021] [Indexed: 02/08/2023]
Abstract
The initiation, progression, and metastatic spread of cancer elicits diverse changes in systemic physiology. In this way, cancer represents a novel homeostatic challenge to the host system. Here, we discuss how the hypothalamus, a critical brain region involved in homeostasis senses, integrates and responds to cancer-induced changes in physiology. Through this lens, cancer-associated changes in behavior (e.g., sleep disruption) and physiology (e.g., glucocorticoid dysregulation) can be viewed as the result of an inability to re-establish homeostasis. We provide examples at each level (receptor sensing, integration of systemic signals, and efferent regulatory pathways) of how homeostatic organization becomes disrupted across different cancers. Finally, we lay out predictions of this hypothesis and highlight outstanding questions that aim to guide further work in this area.
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Affiliation(s)
- Nikita Francis
- Cold Spring Harbor Laboratory, One Bungtown Rd., Cold Spring Harbor, NY 11724
| | - Jeremy C Borniger
- Cold Spring Harbor Laboratory, One Bungtown Rd., Cold Spring Harbor, NY 11724,Correspondence:
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19
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Caba M, Meza E, Escobar C, Jiménez A, Caba-Flores MD, Moreno-Cortés ML, Melo AI. Oxytocinergic cells of the posterior hypothalamic paraventricular nucleus participate in the food entrained clock. Sci Rep 2021; 11:19957. [PMID: 34620909 PMCID: PMC8497610 DOI: 10.1038/s41598-021-99266-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 09/22/2021] [Indexed: 12/17/2022] Open
Abstract
The mechanisms underlying food anticipatory activity are still poorly understood. Here we explored the role of oxytocin (OT) and the protein c-Fos in the supraoptic nucleus (SON), medial (PVNm) and posterior (PVNp) regions of the paraventricular hypothalamic nucleus. Adult rats were assigned to one of four groups: scheduled restricted feeding (RF), ad libitum (AL), fasting after restricted feeding (RF-F), to explore the possible persistence of oscillations, or ad libitum fasted (AL-F). In the SON and in the PVNm, OT cells were c-Fos positive after food intake; in contrast, OT cells in the PVNp showed c-Fos activation in anticipation to food access, which persisted in RF-F subjects. We conclude that OT and non-OT cells of the SON and PVNm may play a role as recipients of the entraining signal provided by food intake, whereas those of the PVNp which contain motor preautonomic cells that project to peripheral organs, may be involved in the hormonal and metabolic anticipatory changes in preparation for food presentation and thus, may be part of a link between central and peripheral oscillators. In addition, due to their persistent activation they may participate in the neuronal network for the clock mechanism that leads to food entrainment.
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Affiliation(s)
- Mario Caba
- Centro de Investigaciones Biomédicas, Universidad Veracruzana, Xalapa, Ver., Mexico.
| | - Enrique Meza
- Centro de Investigaciones Biomédicas, Universidad Veracruzana, Xalapa, Ver., Mexico
| | - Carolina Escobar
- Facultad de Medicina, Universidad Nacional Autónoma de México, CDMX, Mexico
| | - Angeles Jiménez
- Centro de Investigación en Reproducción Animal, CINVESTAV-UAT, Tlaxcala, Tlax, Mexico
| | | | | | - Angel I Melo
- Centro de Investigación en Reproducción Animal, CINVESTAV-UAT, Tlaxcala, Tlax, Mexico
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20
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Arcuate and Preoptic Kisspeptin Neurons Exhibit Differential Projections to Hypothalamic Nuclei and Exert Opposite Postsynaptic Effects on Hypothalamic Paraventricular and Dorsomedial Nuclei in the Female Mouse. eNeuro 2021; 8:ENEURO.0093-21.2021. [PMID: 34281980 PMCID: PMC8354717 DOI: 10.1523/eneuro.0093-21.2021] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 06/21/2021] [Accepted: 07/11/2021] [Indexed: 01/24/2023] Open
Abstract
Kisspeptin (Kiss1) neurons provide indispensable excitatory input to gonadotropin-releasing hormone (GnRH) neurons, which is important for the coordinated release of gonadotropins, estrous cyclicity and ovulation. However, Kiss1 neurons also send projections to many other brain regions within and outside the hypothalamus. Two different populations of Kiss1 neurons, one in the arcuate nucleus (Kiss1ARH) and another in the anteroventral periventricular nucleus (AVPV) and periventricular nucleus (PeN; Kiss1AVPV/PeN) of the hypothalamus are differentially regulated by ovarian steroids, and are believed to form direct contacts with GnRH neurons as well as other neurons. To investigate the projection fields from Kiss1AVPV/PeN and Kiss1ARH neurons in female mice, we used anterograde projection analysis, and channelrhodopsin-assisted circuit mapping (CRACM) to explore their functional input to select target neurons within the paraventricular (PVH) and dorsomedial (DMH) hypothalamus, key preautonomic nuclei. Cre-dependent viral (AAV1-DIO-ChR2 mCherry) vectors were injected into the brain to label the two Kiss1 neuronal populations. Immunocytochemistry (ICC) for mCherry and neuropeptides combined with confocal microscopy was used to determine the projection-fields of both Kiss1 neuronal groups. Whole-cell electrophysiology and optogenetics were used to elucidate the functional input to the PVH and DMH. Our analysis revealed many common but also several clearly separate projection fields between the two different populations of Kiss1 neurons. In addition, optogenetic stimulation of Kiss1 projections to PVH prodynorphin, Vglut2 and DMH CART-expressing neurons, revealed excitatory glutamatergic input from Kiss1ARH neurons and inhibitory GABAergic input from Kiss1AVPV/PeN neurons. Therefore, these steroid-sensitive Kiss1 neuronal groups can differentially control the excitability of target neurons to coordinate autonomic functions with reproduction.
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Ferreira-Neto HC, Antunes VR, Stern JE. Purinergic P2 and glutamate NMDA receptor coupling contributes to osmotically driven excitability in hypothalamic magnocellular neurosecretory neurons. J Physiol 2021; 599:3531-3547. [PMID: 34053068 DOI: 10.1113/jp281411] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 05/28/2021] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Purinergic and glutamatergic signalling pathways play a key role in regulating the activity of hypothalamic magnocellular neurosecretory neurons (MNNs). However, the precise cellular mechanisms by which ATP and glutamate act in concert to regulate osmotically driven MNN neuronal excitability remains unknown. Here, we report that ATP acts on purinergic P2 receptors in MNNs to potentiate in a Ca2+ -dependent manner extrasynaptic NMDAR function. The P2-NMDAR coupling is engaged in response to an acute hyperosmotic stimulation, contributing to osmotically driven firing activity in MNNs. These results help us to better understand the precise mechanisms contributing to the osmotic regulation of firing activity and hormone release from MNNs. ABSTRACT The firing activity of hypothalamic magnocellular neurosecretory neurons (MNNs) located in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) is coordinated by the combined, fine-tuned action of intrinsic membrane properties, synaptic and extrasynaptic signalling. Among these, purinergic and glutamatergic signalling pathways have been shown to play a key role regulating the activity of MNNs. However, the precise cellular mechanisms by which ATP and glutamate act in concert to regulate osmotically driven MNN neuronal excitability remains unknown. Whole-cell patch-clamp recordings obtained from MNNs showed that ATP (100 μM) induced an increase in firing rate, an effect that was blocked by either 4-[[4-formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl]2-pyridinyl]azo]1,3-benzenedisulfonic acid tetrasodium salt (PPADS) (10 μM) or kynurenic acid (1 mm). While ATP did not affect the frequency or magnitude of glutamatergic excitatory postsynaptic currents (EPSCs), it induced an inward shift in the holding current that was prevented by PPADS or kynurenic acid treatment, suggesting that ATP enhances a tonic extrasynaptic glutamatergic excitatory current. We observed that ATP-potentiated glutamatergic receptor-mediated currents were evoked by focal application of L-glu (1 mm) and NMDA (50 μM), but not AMPA (50 μM). ATP potentiation of NMDA-evoked currents was blocked by PPADS (10 μM) and by chelation of intracellular Ca2+ with BAPTA (10 mm). Finally, we report that a hyperosmotic stimulus (mannitol 1%, +55 mOsm/kgH2 O) potentiated NMDA-evoked currents and increased MNN firing activity, effects that were blocked by PPADS. Taken together, our data support a functional excitatory coupling between P2 and extrasynaptic NMDA receptors in MNNs, which is engaged in response to an acute hyperosmotic stimulus.
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Affiliation(s)
- H C Ferreira-Neto
- Neuroscience Institute, Georgia State University, Atlanta, Georgia, USA
| | - V R Antunes
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - J E Stern
- Neuroscience Institute, Georgia State University, Atlanta, Georgia, USA
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Danan D, Todder D, Zohar J, Cohen H. Is PTSD-Phenotype Associated with HPA-Axis Sensitivity? Feedback Inhibition and Other Modulating Factors of Glucocorticoid Signaling Dynamics. Int J Mol Sci 2021; 22:ijms22116050. [PMID: 34205191 PMCID: PMC8200046 DOI: 10.3390/ijms22116050] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 05/27/2021] [Accepted: 05/28/2021] [Indexed: 01/12/2023] Open
Abstract
Previously, we found that basal corticosterone pulsatility significantly impacts the vulnerability for developing post-traumatic stress disorder (PTSD). Rats that exhibited PTSD-phenotype were characterized by blunted basal corticosterone pulsatility amplitude and a blunted corticosterone response to a stressor. This study sought to identify the mechanisms underlining both the loss of pulsatility and differences in downstream responses. Serial blood samples were collected manually via jugular vein cannula at 10-min intervals to evaluate suppression of corticosterone following methylprednisolone administration. The rats were exposed to predator scent stress (PSS) after 24 h, and behavioral responses were assessed 7 days post-exposure for retrospective classification into behavioral response groups. Brains were harvested for measurements of the glucocorticoid receptor, mineralocorticoid receptor, FK506-binding protein-51 and arginine vasopressin in specific brain regions to assess changes in hypothalamus–pituitary–adrenal axis (HPA) regulating factors. Methylprednisolone produced greater suppression of corticosterone in the PTSD-phenotype group. During the suppression, the PTSD-phenotype rats showed a significantly more pronounced pulsatile activity. In addition, the PTSD-phenotype group showed distinct changes in the ventral and dorsal CA1, dentate gyrus as well as in the paraventricular nucleus and supra-optic nucleus. These results demonstrate a pre-trauma vulnerability state that is characterized by an over-reactivity of the HPA and changes in its regulating factors.
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Affiliation(s)
- Dor Danan
- Anxiety and Stress Research Unit, Beer-Sheva Mental Health Center, Ministry of Health, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84170, Israel; (D.D.); (D.T.)
| | - Doron Todder
- Anxiety and Stress Research Unit, Beer-Sheva Mental Health Center, Ministry of Health, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84170, Israel; (D.D.); (D.T.)
| | - Joseph Zohar
- Post-Trauma Center, Sheba Medical Center, Tel Aviv 52621, Israel;
| | - Hagit Cohen
- Anxiety and Stress Research Unit, Beer-Sheva Mental Health Center, Ministry of Health, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84170, Israel; (D.D.); (D.T.)
- Correspondence: ; Tel.: +972-544-369106
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Elsaafien K, Kirchner MK, Mohammed M, Eikenberry SA, West C, Scott KA, de Kloet AD, Stern JE, Krause EG. Identification of Novel Cross-Talk between the Neuroendocrine and Autonomic Stress Axes Controlling Blood Pressure. J Neurosci 2021; 41:4641-4657. [PMID: 33858944 PMCID: PMC8260250 DOI: 10.1523/jneurosci.0251-21.2021] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 04/01/2021] [Accepted: 04/05/2021] [Indexed: 11/21/2022] Open
Abstract
The hypothalamic paraventricular nucleus (PVN) controls neuroendocrine axes and the autonomic nervous system to mount responses that cope with the energetic burdens of psychological or physiological stress. Neurons in the PVN that express the angiotensin Type 1a receptor (PVNAgtr1a) are implicated in neuroendocrine and autonomic stress responses; however, the mechanism by which these neurons coordinate activation of neuroendocrine axes with sympathetic outflow remains unknown. Here, we use a multidisciplinary approach to investigate intra-PVN signaling mechanisms that couple the activity of neurons synthesizing corticotropin-releasing-hormone (CRH) to blood pressure. We used the Cre-Lox system in male mice with in vivo optogenetics and cardiovascular recordings to demonstrate that excitation of PVNAgtr1a promotes elevated blood pressure that is dependent on the sympathetic nervous system. Next, neuroanatomical experiments found that PVNAgtr1a synthesize CRH, and intriguingly, fibers originating from PVNAgtr1a make appositions onto neighboring neurons that send projections to the rostral ventrolateral medulla and express CRH type 1 receptor (CRHR1) mRNA. We then used an ex vivo preparation that combined optogenetics, patch-clamp electrophysiology, and Ca2+ imaging to discover that excitation of PVNAgtr1a drives the local, intra-PVN release of CRH, which activates rostral ventrolateral medulla-projecting neurons via stimulation of CRHR1(s). Finally, we returned to our in vivo preparation and found that CRH receptor antagonism specifically within the PVN lowered blood pressure basally and during optogenetic activation of PVNAgtr1a Collectively, these results demonstrate that angiotensin II acts on PVNAgtr1a to conjoin hypothalamic-pituitary-adrenal axis activity with sympathetically mediated vasoconstriction in male mice.SIGNIFICANCE STATEMENT The survival of an organism is dependent on meeting the energetic demands imposed by stressors. This critical function is accomplished by the CNS's ability to orchestrate simultaneous activities of neurosecretory and autonomic axes. Here, we unveil a novel signaling mechanism within the paraventricular nucleus of the hypothalamus that links excitation of neurons producing corticotropin-releasing-hormone with excitation of neurons controlling sympathetic nervous system activity and blood pressure. The implication is that chronic stress exposure may promote cardiometabolic disease by dysregulating the interneuronal cross-talk revealed by our experiments.
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Affiliation(s)
- Khalid Elsaafien
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, Florida 32611
- Center of Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, Florida 32611
| | - Matthew K Kirchner
- Neuroscience Institute, Georgia State University, Atlanta, Georgia 30302
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, Georgia 30302
| | - Mazher Mohammed
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, Florida 32611
| | - Sophia A Eikenberry
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, Florida 32611
| | - Chloe West
- Neuroscience Institute, Georgia State University, Atlanta, Georgia 30302
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, Georgia 30302
| | - Karen A Scott
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, Florida 32611
- Center of Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, Florida 32611
| | - Annette D de Kloet
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, Florida 32611
- Center of Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, Florida 32611
- McKnight Brain Institute, University of Florida, Gainesville, Florida 32611
| | - Javier E Stern
- Neuroscience Institute, Georgia State University, Atlanta, Georgia 30302
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, Georgia 30302
| | - Eric G Krause
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, Florida 32611
- Center of Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, Florida 32611
- McKnight Brain Institute, University of Florida, Gainesville, Florida 32611
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Kalsbeek A, Buijs RM. Organization of the neuroendocrine and autonomic hypothalamic paraventricular nucleus. HANDBOOK OF CLINICAL NEUROLOGY 2021; 180:45-63. [PMID: 34225948 DOI: 10.1016/b978-0-12-820107-7.00004-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A major function of the nervous system is to maintain a relatively constant internal environment. The distinction between our external environment (i.e., the environment that we live in and that is subject to major changes, such as temperature, humidity, and food availability) and our internal environment (i.e., the environment formed by the fluids surrounding our bodily tissues and that has a very stable composition) was pointed out in 1878 by Claude Bernard (1814-1878). Later on, it was indicated by Walter Cannon (1871-1945) that the internal environment is not really constant, but rather shows limited variability. Cannon named the mechanism maintaining this limited variability homeostasis. Claude Bernard envisioned that, for optimal health, all physiologic processes in the body needed to maintain homeostasis and should be in perfect harmony with each other. This is illustrated by the fact that, for instance, during the sleep-wake cycle important elements of our physiology such as body temperature, circulating glucose, and cortisol levels show important variations but are in perfect synchrony with each other. These variations are driven by the biologic clock in interaction with hypothalamic target areas, among which is the paraventricular nucleus of the hypothalamus (PVN), a core brain structure that controls the neuroendocrine and autonomic nervous systems and thus is key for integrating central and peripheral information and implementing homeostasis. This chapter focuses on the anatomic connections between the biologic clock and the PVN to modulate homeostasis according to the daily sleep-wake rhythm. Experimental studies have revealed a highly specialized organization of the connections between the clock neurons and neuroendocrine system as well as preautonomic neurons in the PVN. These complex connections ensure a logical coordination between behavioral, endocrine, and metabolic functions that helps the organism maintain homeostasis throughout the day.
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Affiliation(s)
- Andries Kalsbeek
- Department of Endocrinology and Metabolism, Amsterdam University Medical Centers (Amsterdam UMC), University of Amsterdam, Amsterdam, The Netherlands; Department of Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, an Institute of the Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands.
| | - Ruud M Buijs
- Hypothalamic Integration Mechanisms Laboratory, Department of Cellular Biology and Physiology, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad de México, Mexico
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Domingos-Souza G, Martinez D, Sinkler S, Heesch CM, Kline DD. Alpha adrenergic receptor signaling in the hypothalamic paraventricular nucleus is diminished by the chronic intermittent hypoxia model of sleep apnea. Exp Neurol 2021; 335:113517. [PMID: 33132201 PMCID: PMC7750300 DOI: 10.1016/j.expneurol.2020.113517] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 10/13/2020] [Accepted: 10/20/2020] [Indexed: 01/08/2023]
Abstract
Chronic intermittent hypoxia (CIH) is a model for obstructive sleep apnea. The paraventricular nucleus (PVN) of the hypothalamus has been suggested to contribute to CIH-induced exaggerated cardiorespiratory reflexes, sympathoexcitation and hypertension. This may occur, in part, via activation of the dense catecholaminergic projections to the PVN that originate in the brainstem. However, the contribution of norepinephrine (NE) and activation of its alpha-adrenergic receptors (α-ARs) in the PVN after CIH exposure is unknown. We hypothesized CIH would increase the contribution of catecholaminergic input. To test this notion, we determined the expression of α-AR subtypes, catecholamine terminal density, and synaptic properties of PVN parvocellular neurons in response to α-AR activation in male Sprague-Dawley normoxic (Norm) and CIH exposed rats. CIH decreased mRNA for α1d and α2b AR. Dopamine-β-hydroxylase (DβH) terminals in the PVN were similar between groups. NE and the α1-AR agonist phenylephrine (PE) increased sEPSC frequency after Norm but not CIH. Block of α1-ARs with prazosin alone did not alter sEPSCs after either Norm or CIH but did prevent agonist augmentation of sEPSC frequency following normoxia. These responses to NE were mimicked by PE during action potential block suggesting presynaptic terminal alterations in CIH. Altogether, these results demonstrate that α1-AR activation participates in neuronal responses in Norm, but are attenuated after CIH. These results may provide insight into the cardiovascular, respiratory and autonomic nervous systems alterations in obstructive sleep apnea.
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Affiliation(s)
- Gean Domingos-Souza
- Dept. of Biomedical Sciences and Dalton Cardiovascular Research Center, Univ. of Missouri, Columbia, MO 65211, United States of America
| | - Diana Martinez
- Dept. of Biomedical Sciences and Dalton Cardiovascular Research Center, Univ. of Missouri, Columbia, MO 65211, United States of America
| | - Steven Sinkler
- Dept. of Biomedical Sciences and Dalton Cardiovascular Research Center, Univ. of Missouri, Columbia, MO 65211, United States of America
| | - Cheryl M Heesch
- Dept. of Biomedical Sciences and Dalton Cardiovascular Research Center, Univ. of Missouri, Columbia, MO 65211, United States of America
| | - David D Kline
- Dept. of Biomedical Sciences and Dalton Cardiovascular Research Center, Univ. of Missouri, Columbia, MO 65211, United States of America.
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An Angiotensin-Responsive Connection from the Lamina Terminalis to the Paraventricular Nucleus of the Hypothalamus Evokes Vasopressin Secretion to Increase Blood Pressure in Mice. J Neurosci 2020; 41:1429-1442. [PMID: 33328294 DOI: 10.1523/jneurosci.1600-20.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 11/29/2020] [Accepted: 12/03/2020] [Indexed: 12/22/2022] Open
Abstract
Blood pressure is controlled by endocrine, autonomic, and behavioral responses that maintain blood volume and perfusion pressure at levels optimal for survival. Although it is clear that central angiotensin type 1a receptors (AT1aR; encoded by the Agtr1a gene) influence these processes, the neuronal circuits mediating these effects are incompletely understood. The present studies characterize the structure and function of AT1aR neurons in the lamina terminalis (containing the median preoptic nucleus and organum vasculosum of the lamina terminalis), thereby evaluating their roles in blood pressure control. Using male Agtr1a-Cre mice, neuroanatomical studies reveal that AT1aR neurons in the area are largely glutamatergic and send projections to the paraventricular nucleus of the hypothalamus (PVN) that appear to synapse onto vasopressin-synthesizing neurons. To evaluate the functionality of these lamina terminalis AT1aR neurons, we virally delivered light-sensitive opsins and then optogenetically excited or inhibited the neurons while evaluating cardiovascular parameters or fluid intake. Optogenetic excitation robustly elevated blood pressure, water intake, and sodium intake, while optogenetic inhibition produced the opposite effects. Intriguingly, optogenetic excitation of these AT1aR neurons of the lamina terminalis also resulted in Fos induction in vasopressin neurons within the PVN and supraoptic nucleus. Further, within the PVN, selective optogenetic stimulation of afferents that arise from these lamina terminalis AT1aR neurons induced glutamate release onto magnocellular neurons and was sufficient to increase blood pressure. These cardiovascular effects were attenuated by systemic pretreatment with a vasopressin-1a-receptor antagonist. Collectively, these data indicate that excitation of lamina terminalis AT1aR neurons induces neuroendocrine and behavioral responses that increase blood pressure.SIGNIFICANCE STATEMENT Hypertension is a widespread health problem and risk factor for cardiovascular disease. Although treatments exist, a substantial percentage of patients suffer from "drug-resistant" hypertension, a condition associated with increased activation of brain angiotensin receptors, enhanced sympathetic nervous system activity, and elevated vasopressin levels. The present study highlights a role for angiotensin Type 1a receptor expressing neurons located within the lamina terminalis in regulating endocrine and behavioral responses that are involved in maintaining cardiovascular homeostasis. More specifically, data presented here reveal functional excitatory connections between angiotensin-sensitive neurons in the lamina terminals and vasopressin neurons in the paraventricular nucleus of the hypothalamus, and further indicate that activation of this circuit raises blood pressure. These neurons may be a promising target for antihypertensive therapeutics.
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Social touch promotes interfemale communication via activation of parvocellular oxytocin neurons. Nat Neurosci 2020; 23:1125-1137. [PMID: 32719563 DOI: 10.1038/s41593-020-0674-y] [Citation(s) in RCA: 133] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 06/18/2020] [Indexed: 12/19/2022]
Abstract
Oxytocin (OT) is a great facilitator of social life but, although its effects on socially relevant brain regions have been extensively studied, OT neuron activity during actual social interactions remains unexplored. Most OT neurons are magnocellular neurons, which simultaneously project to the pituitary and forebrain regions involved in social behaviors. In the present study, we show that a much smaller population of OT neurons, parvocellular neurons that do not project to the pituitary but synapse onto magnocellular neurons, is preferentially activated by somatosensory stimuli. This activation is transmitted to the larger population of magnocellular neurons, which consequently show coordinated increases in their activity during social interactions between virgin female rats. Selectively activating these parvocellular neurons promotes social motivation, whereas inhibiting them reduces social interactions. Thus, parvocellular OT neurons receive particular inputs to control social behavior by coordinating the responses of the much larger population of magnocellular OT neurons.
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Chronic alcohol disrupts hypothalamic responses to stress by modifying CRF and NMDA receptor function. Neuropharmacology 2020; 167:107991. [PMID: 32059962 DOI: 10.1016/j.neuropharm.2020.107991] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 01/07/2020] [Accepted: 02/05/2020] [Indexed: 01/23/2023]
Abstract
The chronic inability of alcoholics to effectively cope with relapse-inducing stressors has been linked to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and corticotropin-releasing factor (CRF) signaling. However, the cellular mechanisms responsible for this dysregulation are yet to be identified. After exposure of male Sprague Dawley rats to chronic intermittent ethanol (CIE; 5-6 g/kg orally for 35 doses over 50 days) or water, followed by 40-60 days of protracted withdrawal, we investigated CIE effects on glutamatergic synaptic transmission, stress-induced plasticity, CRF- and ethanol-induced NMDAR inhibition using electrophysiological recordings in parvocellular neurosecretory cells (PNCs) of the paraventricular nucleus. We also assessed CIE effects on hypothalamic mRNA expression of CRF-related genes using real-time polymerase chain reaction, and on HPA axis function by measuring stress-induced increases in plasma adrenocorticotropic hormone, corticosterone, and self-grooming. In control rats, ethanol-mediated inhibition of NMDARs was prevented by CRF1 receptor (CRFR1) blockade with antalarmin, while CRF/CRFR1-mediated NMDAR blockade was prevented by intracellularly-applied inhibitor of phosphatases PP1/PP2A, okadaic acid, but not the selective striatal-enriched tyrosine protein phosphatase inhibitor, TC-2153. CIE exposure increased GluN2B subunit-dependent NMDAR function of PNCs. This was associated with the loss of both ethanol- and CRF-mediated NMDAR inhibition, and loss of stress-induced short-term potentiation of glutamatergic synaptic inputs, which could be reversed by intracellular blockade of NMDARs with MK801. CIE exposure also blunted the hormonal and self-grooming behavioral responses to repeated restraint stress. These findings suggest a cellular mechanism whereby chronic alcohol dysregulates the hormonal and behavioral responses to repetitive stressors by increasing NMDAR function and decreasing CRFR1 function.
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Dai YWE, Lee YH, Li TL, Hwang LL. Mechanisms of orexin 2 receptor-mediated depolarization in the rat paraventricular nucleus of the hypothalamus. Eur J Pharmacol 2020; 869:172802. [DOI: 10.1016/j.ejphar.2019.172802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Revised: 11/12/2019] [Accepted: 11/14/2019] [Indexed: 12/18/2022]
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Melnick I, Krishtal OA, Colmers WF. Integration of energy homeostasis and stress by parvocellular neurons in rat hypothalamic paraventricular nucleus. J Physiol 2020; 598:1073-1092. [PMID: 31952096 DOI: 10.1113/jp279387] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 01/16/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Central regulation of energy homeostasis and stress are believed to be reciprocally regulated, i.e. excessive food intake suppresses, while prolonged hunger exacerbates, stress responses in vivo. This relationship may be mediated by neuroendocrine parvocellular corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus that receive both stress- and feeding-related input. We find that hunger strongly and selectively potentiates, while re-feeding suppresses, a cellular analogue of a stress response induced by acute glucopenia in CRH neurons in rat hypothalamic slices. Neuronal activation in response to glucopenia was mediated synaptically, via the relative enhancement of glutamate over GABA input. These results illustrate how acute stress responses may be initiated in vivo and show that it is reciprocally integrated with energy balance via local hypothalamic mechanisms acting at the level of CRH neurons and their afferent terminals. ABSTRACT Increased food intake is a common response to help cope with stress, implying the existence of a previously postulated but imperfectly understood, inverse relationship between the regulation of feeding and stress. We have identified components of the neural circuitry that can integrate these homeostatic responses. Prior fasting (∼24 h) potentiates, and re-feeding suppresses, excitatory responses to acute glucopenia in about half of the corticotropin releasing hormone (CRH)-expressing, putatively neurosecretory, stress-related neurons in the paraventricular nucleus of the hypothalamus studied. Glucoprivation stress ex vivo resulted from a preferential relative increase in excitatory (glutamatergic) over inhibitory (GABAergic) inputs. Putative preautonomic cells were less sensitive to fasting, and showed a predominant inhibition to acute glucopenia. We conclude that hunger may sensitize hypothalamic stress responses by acting via local mechanisms, at the level of CRH neurons and their presynaptic inputs. Those mechanisms involve neither presynaptic ATP-sensitive potassium channels nor postsynaptic ATP levels.
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Affiliation(s)
- Igor Melnick
- Bogomoletz Institute of Physiology, Bogomoletz str 4, Kiev, 01024, Ukraine
| | - Oleg A Krishtal
- Bogomoletz Institute of Physiology, Bogomoletz str 4, Kiev, 01024, Ukraine
| | - William F Colmers
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada, T6G 2H7
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Jiang Z, Rajamanickam S, Justice NJ. CRF signaling between neurons in the paraventricular nucleus of the hypothalamus (PVN) coordinates stress responses. Neurobiol Stress 2019; 11:100192. [PMID: 31516918 PMCID: PMC6732729 DOI: 10.1016/j.ynstr.2019.100192] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 08/07/2019] [Accepted: 08/08/2019] [Indexed: 12/22/2022] Open
Abstract
The importance of a precisely coordinated neuroendocrine, autonomic, and behavioral stress response was a primary theme at the Stress Neurobiology Workshop 2018, held in the beautiful setting of Banff Provincial Park in Alberta, Canada. Much of the research featured at this meeting reinforced the importance of appropriately responding to stress in order to avoid various neuropsychiatric pathologies, including Post-Traumatic Stress Disorder (PTSD), depression, and addiction. Corticotropin-Releasing Factor (CRF) neurons in the paraventricular nucleus of the hypothalamus (PVN) are central players in the stress response, integrating both external and visceral stress-relevant information, then directing neuroendocrine, autonomic and behavioral adaptations via endocrine and neural outputs of the PVN. The PVN contains a densely packed array of neuron types that respond to stress, including CRF neurons that activate the Hypothalamic-Pituitary-Adrenal (HPA) axis. Recently, identification of a new population of neurons in the PVN that express CRF Receptor 1 (CRFR1) has suggested that CRF release in the PVN signals to neighboring CRF responsive neurons, potentially functioning in HPA axis feedback, neuroendocrine coordination, and autonomic signaling. Here, we review our recent work characterizing an intra-PVN microcircuit in which locally released CRF release activates CRFR1+ neurons that make recurrent inhibitory GABAergic synapses onto CRF neurons to dampen excitability , therebylimiting HPA axis hyperactivity in response to stress and promoting stress recovery, which we presented in a poster session at the conference. We then discuss questions that have arisen following publication of our initial characterization of the microcircuit, regarding specific features of intra-PVN CRF signaling and its potential role in coordinating neuroendocrine, autonomic, and behavioral outputs of the PVN. Our presented work, as well as many of the presentations at the Stress Neurobiology Workshop 2018 together establish intra-PVN signaling as an important regulatory node in stress response pathways, which are central to the pathogenesis of neuropsychiatric disorders.
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Affiliation(s)
- Zhiying Jiang
- The Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, McGovern Medical School, The University of Texas Health Science Center at Houston, Texas, 77030, USA
| | - Shivakumar Rajamanickam
- The Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, McGovern Medical School, The University of Texas Health Science Center at Houston, Texas, 77030, USA
| | - Nicholas J Justice
- The Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, McGovern Medical School, The University of Texas Health Science Center at Houston, Texas, 77030, USA
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Dantzler HA, Matott MP, Martinez D, Kline DD. Hydrogen peroxide inhibits neurons in the paraventricular nucleus of the hypothalamus via potassium channel activation. Am J Physiol Regul Integr Comp Physiol 2019; 317:R121-R133. [PMID: 31042419 DOI: 10.1152/ajpregu.00054.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The paraventricular nucleus (PVN) of the hypothalamus is an important homeostatic and reflex center for neuroendocrine, respiratory, and autonomic regulation, including during hypoxic stressor challenges. Such challenges increase reactive oxygen species (ROS) to modulate synaptic, neuronal, and ion channel activity. Previously, in the nucleus tractus solitarius, another cardiorespiratory nucleus, we showed that the ROS H2O2 induced membrane hyperpolarization and reduced action potential discharge via increased K+ conductance at the resting potential. Here, we sought to determine the homogeneity of influence and mechanism of action of H2O2 on PVN neurons. We recorded PVN neurons in isolation and in an acute slice preparation, which leaves neurons in their semi-intact network. Regardless of preparation, H2O2 hyperpolarized PVN neurons and decreased action potential discharge. In the slice preparation, H2O2 also decreased spontaneous excitatory postsynaptic current frequency, but not amplitude. To examine potential mechanisms, we investigated the influence of the K+ channel blockers Ba2+, Cs+, and glibenclamide on membrane potential, as well as the ionic currents active at resting potential and outward K+ currents (IK) upon depolarization. The H2O2 hyperpolarization was blocked by K+ channel blockers. H2O2 did not alter currents between -50 and -110 mV. However, H2O2 induced an outward IK at -50 mV yet, at potentials more positive to 0 mV H2O2, decreased IK. Elevated intracellular antioxidant catalase eliminated H2O2 effects. These data indicate that H2O2 alters synaptic and neuronal properties of PVN neurons likely via membrane hyperpolarization and alteration of IK, which may ultimately alter cardiorespiratory reflexes.
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Affiliation(s)
- Heather A Dantzler
- Department of Biomedical Sciences, University of Missouri , Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri , Columbia, Missouri
| | - Michael P Matott
- Department of Biomedical Sciences, University of Missouri , Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri , Columbia, Missouri
| | - Diana Martinez
- Department of Biomedical Sciences, University of Missouri , Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri , Columbia, Missouri
| | - David D Kline
- Department of Biomedical Sciences, University of Missouri , Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri , Columbia, Missouri
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Dos-Santos RC, Reis LC, Perello M, Ferguson AV, Mecawi AS. The actions of ghrelin in the paraventricular nucleus: energy balance and neuroendocrine implications. Ann N Y Acad Sci 2019; 1455:81-97. [PMID: 31008525 DOI: 10.1111/nyas.14087] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 02/28/2019] [Accepted: 03/10/2019] [Indexed: 12/15/2022]
Abstract
Ghrelin is a peptide mainly produced and secreted by the stomach. Since its discovery, the impact of ghrelin on the regulation of food intake has been the most studied function of this hormone; however, ghrelin affects a wide range of physiological systems, many of which are controlled by the hypothalamic paraventricular nucleus (PVN). Several pathways may mediate the effects of ghrelin on PVN neurons, such as direct or indirect effects mediated by circumventricular organs and/or the arcuate nucleus. The ghrelin receptor is expressed in PVN neurons, and the peripheral or intracerebroventricular administration of ghrelin affects PVN neuronal activity. Intra-PVN application of ghrelin increases food intake and decreases fat oxidation, which chronically contribute to the increased adiposity. Additionally, ghrelin modulates the neuroendocrine axes controlled by the PVN, increasing the release of vasopressin and oxytocin by magnocellular neurons and corticotropin-releasing hormone by neuroendocrine parvocellular neurons, while possibly inhibiting the release of thyrotropin-releasing hormone. Thus, the PVN is an important target for the actions of ghrelin. Our review discusses the mechanisms of ghrelin actions in the PVN, and its potential implications for energy balance, neuroendocrine, and integrative physiological control.
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Affiliation(s)
- Raoni C Dos-Santos
- Department of Physiological Sciences, Federal Rural University of Rio de Janeiro, Seropédica, Brazil
| | - Luís C Reis
- Department of Physiological Sciences, Federal Rural University of Rio de Janeiro, Seropédica, Brazil
| | - Mario Perello
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology, La Plata, Argentina
| | - Alastair V Ferguson
- Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
| | - André S Mecawi
- Laboratory of Neuroendocrinology, Department of Biophysics, Paulista Medical School, Federal University of São Paulo, São Paulo, Brazil
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Synaptic adaptations in the central amygdala and hypothalamic paraventricular nucleus associated with protracted ethanol abstinence in male rhesus monkeys. Neuropsychopharmacology 2019; 44:982-993. [PMID: 30555160 PMCID: PMC6461779 DOI: 10.1038/s41386-018-0290-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 11/25/2018] [Accepted: 11/27/2018] [Indexed: 01/06/2023]
Abstract
Alcohol use disorder is a significant global burden. Stress has been identified as an etiological factor in the initiation and continuation of ethanol consumption. Understanding adaptations within stress circuitry is an important step toward novel treatment strategies. The effects of protracted abstinence following long-term ethanol self-administration on the central nucleus of the amygdala (CeA) and the hypothalamic paraventricular nucleus (PVN) were evaluated in male rhesus monkeys. Using whole-cell patch-clamp electrophysiology, inhibitory GABAergic transmission in the CeA and excitatory glutamatergic transmission in the PVN were measured. CeA neurons from abstinent drinkers displayed an elevated baseline spontaneous inhibitory postsynaptic current (sIPSC) frequency compared with controls, indicating increased presynaptic GABA release. Application of acute ethanol significantly increased the frequency of sIPSCs in controls, but not in abstinent drinkers, suggesting a tolerance to ethanol-enhanced GABA release in abstinent rhesus monkeys with a history of chronic ethanol self-administration and repeated abstinence. In the PVN, the frequency of spontaneous excitatory postsynaptic currents (sEPSC) was elevated in abstinent drinkers compared with controls, indicating increased presynaptic glutamate release. Notably, acute ethanol decreased presynaptic glutamate release onto parvocellular PVN neurons in both controls and abstinent drinkers, suggesting a lack of tolerance to acute ethanol among PVN neurons. These results are the first to demonstrate distinct synaptic adaptations and ethanol sensitivity in both the extrahypothalamic and hypothalamic stress circuits in abstinent rhesus males. Importantly, our findings describe adaptations in stress circuitry present in the brain at a state during abstinence, just prior to relapse to ethanol drinking.
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Armstrong WE, Foehring RC, Kirchner MK, Sladek CD. Electrophysiological properties of identified oxytocin and vasopressin neurones. J Neuroendocrinol 2019; 31:e12666. [PMID: 30521104 PMCID: PMC7251933 DOI: 10.1111/jne.12666] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 11/26/2018] [Accepted: 11/29/2018] [Indexed: 12/18/2022]
Abstract
To understand the contribution of intrinsic membrane properties to the different in vivo firing patterns of oxytocin (OT) and vasopressin (VP) neurones, in vitro studies are needed, where stable intracellular recordings can be made. Combining immunochemistry for OT and VP and intracellular dye injections allows characterisation of identified OT and VP neurones, and several differences between the two cell types have emerged. These include a greater transient K+ current that delays spiking to stimulus onset, and a higher Na+ current density leading to greater spike amplitude and a more stable spike threshold, in VP neurones. VP neurones also show a greater incidence of both fast and slow Ca2+ -dependent depolarising afterpotentials, the latter of which summate to plateau potentials and contribute to phasic bursting. By contrast, OT neurones exhibit a sustained outwardly rectifying potential (SOR), as well as a consequent depolarising rebound potential, not found in VP neurones. The SOR makes OT neurones more susceptible to spontaneous inhibitory synaptic inputs and correlates with a longer period of spike frequency adaptation in these neurones. Although both types exhibit prominent Ca2+ -dependent afterhyperpolarising potentials (AHPs) that limit firing rate and contribute to bursting patterns, Ca2+ -dependent AHPs in OT neurones selectively show significant increases during pregnancy and lactation. In OT neurones, but not VP neurones, AHPs are highly dependent on the constitutive presence of the second messenger, phosphatidylinositol 4,5-bisphosphate, which permissively gates N-type channels that contribute the Ca2+ during spike trains that activates the AHP. By contrast to the intrinsic properties supporting phasic bursting in VP neurones, the synchronous bursting of OT neurones has only been demonstrated in vitro in cultured hypothalamic explants and is completely dependent on synaptic transmission. Additional differences in Ca2+ channel expression between the two neurosecretory terminal types suggests these channels are also critical players in the differential release of OT and VP during repetitive spiking, in addition to their importance to the potentials controlling firing patterns.
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Affiliation(s)
- William E Armstrong
- Department of Anatomy & Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Robert C Foehring
- Department of Anatomy & Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Matthew K Kirchner
- Department of Anatomy & Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Celia D Sladek
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado
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36
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Shen Y, Han SK, Ryu PD. Comparison of electrophysiological properties of two types of pre-sympathetic neurons intermingled in the hypothalamic paraventricular nucleus. J Vet Sci 2018; 19:483-491. [PMID: 29649859 PMCID: PMC6070595 DOI: 10.4142/jvs.2018.19.4.483] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 03/06/2018] [Accepted: 03/09/2018] [Indexed: 11/20/2022] Open
Abstract
The hypothalamic paraventricular nucleus (PVN) contains two types of neurons projecting to either the rostral ventrolateral medulla (PVNRVLM) or the intermediolateral horn (IML) of the spinal cord (PVNIML). These two neuron groups are intermingled in the same subdivisions of the PVN and differentially regulate sympathetic outflow. However, electrophysiological evidence supporting such functional differences is largely lacking. Herein, we compared the electrophysiological properties of these neurons by using patch-clamp and retrograde-tracing techniques. Most neurons (>70%) in both groups spontaneously fired in the cell-attached mode. When compared to the PVNIML neurons, the PVNRVLM neurons had a lower firing rate and a more irregular firing pattern (p < 0.05). The PVNRVLM neurons showed smaller resting membrane potential, slower rise and decay times, and greater duration of spontaneous action potentials (p < 0.05). The PVNRVLM neurons received greater inhibitory synaptic inputs (frequency, p < 0.05) with a shorter rise time (p < 0.05). Taken together, the results indicate that the two pre-sympathetic neurons differ in their intrinsic and extrinsic electrophysiological properties, which may explain the lower firing activity of the PVNRVLM neurons. The greater inhibitory synaptic inputs to the PVNRVLM neurons also imply that these neurons have more integrative roles in regulation of sympathetic activity.
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Affiliation(s)
- Yiming Shen
- Department of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute of Veterinary Science, Seoul National University, Seoul 08826, Korea
| | - Seong Kyu Han
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 54896, Korea
| | - Pan Dong Ryu
- Department of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute of Veterinary Science, Seoul National University, Seoul 08826, Korea
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Ruyle BC, Klutho PJ, Baines CP, Heesch CM, Hasser EM. Hypoxia activates a neuropeptidergic pathway from the paraventricular nucleus of the hypothalamus to the nucleus tractus solitarii. Am J Physiol Regul Integr Comp Physiol 2018; 315:R1167-R1182. [PMID: 30230933 DOI: 10.1152/ajpregu.00244.2018] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The paraventricular nucleus of the hypothalamus (PVN) contributes to both autonomic and neuroendocrine function. PVN lesion or inhibition blunts cardiorespiratory responses to peripheral chemoreflex activation, suggesting that the PVN is required for full expression of these effects. However, the role of efferent projections to cardiorespiratory nuclei and the neurotransmitters/neuromodulators that are involved is unclear. The PVN sends dense projections to the nucleus tractus solitarii (nTS), a region that displays neuronal activation following hypoxia. We hypothesized that acute hypoxia activates nTS-projecting PVN neurons. Using a combination of retrograde tracing and immunohistochemistry, we determined whether hypoxia activates PVN neurons that project to the nTS and examined the phenotype of these neurons. Conscious rats underwent 2 h normoxia (21% O2, n = 5) or hypoxia (10% O2, n = 6). Hypoxia significantly increased Fos immunoreactivity in nTS-projecting neurons, primarily in the caudal PVN. The majority of activated nTS-projecting neurons contained corticotropin-releasing hormone (CRH). In the nTS, fibers expressing the CRH receptor corticotropin-releasing factor receptor 2 (CRFR2) were colocalized with oxytocin (OT) fibers and were closely associated with hypoxia-activated nTS neurons. A separate group of animals that received a microinjection of adeno-associated virus type 2-hSyn-green fluorescent protein (GFP) into the PVN exhibited GFP-expressing fibers in the nTS; a proportion of these fibers displayed OT immunoreactivity. Thus, nTS CRFR2s appear to be located on the fibers of PVN OT neurons that project to the nTS. Taken together, our findings suggest that PVN CRH projections to the nTS may modulate nTS neuronal activation, possibly via OTergic mechanisms, and thus contribute to chemoreflex cardiorespiratory responses.
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Affiliation(s)
- Brian C Ruyle
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri
| | - Paula J Klutho
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri , Columbia, Missouri
| | - Christopher P Baines
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri , Columbia, Missouri.,Department of Medical Pharmacology and Physiology, University of Missouri , Columbia, Missouri
| | - Cheryl M Heesch
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri , Columbia, Missouri
| | - Eileen M Hasser
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri , Columbia, Missouri.,Department of Medical Pharmacology and Physiology, University of Missouri , Columbia, Missouri
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Dos-Santos RC, Grover HM, Reis LC, Ferguson AV, Mecawi AS. Electrophysiological Effects of Ghrelin in the Hypothalamic Paraventricular Nucleus Neurons. Front Cell Neurosci 2018; 12:275. [PMID: 30210300 PMCID: PMC6121211 DOI: 10.3389/fncel.2018.00275] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 08/07/2018] [Indexed: 12/05/2022] Open
Abstract
The paraventricular nucleus (PVN) is involved in the control of sympathetic tone and the secretion of hormones, both functions known to be influenced by ghrelin, suggesting direct effect of ghrelin in this nucleus. However, the effects of ghrelin on the excitability of different PVN neuronal populations have not been demonstrated. This study assessed the effects of ghrelin on the activity of PVN neurons, correlating the responses to subpopulations of PVN neurons. We used a 64 multielectrode array to examine the effects of ghrelin administration on extracellular spike frequency in PVN neurons recorded in brain slices obtained from male Sprague-Dawley rats. Bath administration of 10 nM ghrelin increased (29/97, 30%) or decreased (37/97, 38%) spike frequency in PVN neurons. The GABAA and glutamate receptors antagonists abolish the decrease in spike frequency, without changes in the proportion of increases in spike frequency (23/53, 43%) induced by ghrelin. The results indicate a direct effect of ghrelin increasing PVN neurons activity and a synaptic dependent effect decreasing PVN neurons activity. The patch clamp recordings showed similar proportions of PVN neurons influenced by 10 nM ghrelin (33/95, 35% depolarized; 29/95, 30% hyperpolarized). Using electrophysiological fingerprints to identify specific subpopulations of PVN neurons we observed that the majority of pre-autonomic neurons (11/18 -61%) were depolarized by ghrelin, while both neuroendocrine (29% depolarizations, 40% hyperpolarizations), and magnocellular neurons (29% depolarizations, 21% hyperpolarizations) showed mixed responses. Finally, to correlate the electrophysiological response and the neurochemical phenotype of PVN neurons, cell cytoplasm was collected after recordings and RT-PCR performed to assess the presence of mRNA for vasopressin, oxytocin, thyrotropin (TRH) and corticotropin (CRH) releasing hormones. The single-cell RT-PCR showed that most TRH-expressing (4/5) and CRH-expressing (3/4) neurons are hyperpolarized in response to ghrelin. In conclusion, ghrelin either directly increases or indirectly decreases the activity of PVN neurons, this suggests that ghrelin acts on inhibitory PVN neurons that, in turn, decrease the activity of TRH-expressing and CRH-expressing neurons in the PVN.
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Affiliation(s)
- Raoni C Dos-Santos
- Department of Physiological Sciences, Institute of Biological and Health Sciences, Federal Rural University of Rio de Janeiro, Seropédica, Brazil
| | - Hanna M Grover
- Centre for Neuroscience Studies, Queen's University, Kingston, ON, Canada
| | - Luís C Reis
- Department of Physiological Sciences, Institute of Biological and Health Sciences, Federal Rural University of Rio de Janeiro, Seropédica, Brazil
| | | | - André S Mecawi
- Department of Physiological Sciences, Institute of Biological and Health Sciences, Federal Rural University of Rio de Janeiro, Seropédica, Brazil.,Department of Biophysics, Paulista School of Medicine, Federal University of São Paulo, São Paulo, Brazil
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Feetham CH, O'Brien F, Barrett-Jolley R. Ion Channels in the Paraventricular Hypothalamic Nucleus (PVN); Emerging Diversity and Functional Roles. Front Physiol 2018; 9:760. [PMID: 30034342 PMCID: PMC6043726 DOI: 10.3389/fphys.2018.00760] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 05/30/2018] [Indexed: 12/11/2022] Open
Abstract
The paraventricular nucleus of the hypothalamus (PVN) is critical for the regulation of homeostatic function. Although also important for endocrine regulation, it has been referred to as the "autonomic master controller." The emerging consensus is that the PVN is a multifunctional nucleus, with autonomic roles including (but not limited to) coordination of cardiovascular, thermoregulatory, metabolic, circadian and stress responses. However, the cellular mechanisms underlying these multifunctional roles remain poorly understood. Neurones from the PVN project to and can alter the function of sympathetic control regions in the medulla and spinal cord. Dysfunction of sympathetic pre-autonomic neurones (typically hyperactivity) is linked to several diseases including hypertension and heart failure and targeting this region with specific pharmacological or biological agents is a promising area of medical research. However, to facilitate future medical exploitation of the PVN, more detailed models of its neuronal control are required; populated by a greater compliment of constituent ion channels. Whilst the cytoarchitecture, projections and neurotransmitters present in the PVN are reasonably well documented, there have been fewer studies on the expression and interplay of ion channels. In this review we bring together an up to date analysis of PVN ion channel studies and discuss how these channels may interact to control, in particular, the activity of the sympathetic system.
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Affiliation(s)
- Claire H Feetham
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Fiona O'Brien
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Richard Barrett-Jolley
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
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Local Corticotropin-Releasing Factor Signaling in the Hypothalamic Paraventricular Nucleus. J Neurosci 2018; 38:1874-1890. [PMID: 29352046 DOI: 10.1523/jneurosci.1492-17.2017] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 12/13/2017] [Accepted: 12/19/2017] [Indexed: 01/28/2023] Open
Abstract
Corticotropin-releasing factor (CRF) neurons in the hypothalamic paraventricular nucleus (PVN) initiate hypothalamic-pituitary-adrenal axis activity through the release of CRF into the portal system as part of a coordinated neuroendocrine, autonomic, and behavioral response to stress. The recent discovery of neurons expressing CRF receptor type 1 (CRFR1), the primary receptor for CRF, adjacent to CRF neurons within the PVN, suggests that CRF also signals within the hypothalamus to coordinate aspects of the stress response. Here, we characterize the electrophysiological and molecular properties of PVN-CRFR1 neurons and interrogate their monosynaptic connectivity using rabies virus-based tracing and optogenetic circuit mapping in male and female mice. We provide evidence that CRF neurons in the PVN form synapses on neighboring CRFR1 neurons and activate them by releasing CRF. CRFR1 neurons receive the majority of monosynaptic input from within the hypothalamus, mainly from the PVN itself. Locally, CRFR1 neurons make GABAergic synapses on parvocellular and magnocellular cells within the PVN. CRFR1 neurons resident in the PVN also make long-range glutamatergic synapses in autonomic nuclei such as the nucleus of the solitary tract. Selective ablation of PVN-CRFR1 neurons in male mice elevates corticosterone release during a stress response and slows the decrease in circulating corticosterone levels after the cessation of stress. Our experiments provide evidence for a novel intra-PVN neural circuit that is activated by local CRF release and coordinates autonomic and endocrine function during stress responses.SIGNIFICANCE STATEMENT The hypothalamic paraventricular nucleus (PVN) coordinates concomitant changes in autonomic and neuroendocrine function to organize the response to stress. This manuscript maps intra-PVN circuitry that signals via CRF, delineates CRF receptor type 1 neuron synaptic targets both within the PVN and at distal targets, and establishes the role of this microcircuit in regulating hypothalamic-pituitary-adrenal axis activity.
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Nicotine excites corticotropin-releasing hormone mRNA-expressing neuron in the hypothalamic paraventricular nucleus in vitro in rats. Neuroreport 2018; 27:580-6. [PMID: 27022819 DOI: 10.1097/wnr.0000000000000573] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Nicotine is known to modulate the activity of the hypothalamic-pituitary-adrenal axis by stimulating corticotropin-releasing hormone (CRH) release from the hypothalamic paraventricular nucleus (PVN). However, the mechanism by which nicotine affects the hypothalamic-pituitary-adrenal axis by modulating PVN CRH neuronal activity is currently unclear. Here, we examined the effects of nicotine on PVN CRH-mRNA-expressing neurons in vitro in rats by whole-cell patch-clamp recordings, biocytin staining, and single-cell reverse transcription-multiplex PCR techniques. Of the 146 PVN putative parvocellular neurons, 17.1% (25/146) coexpressed GAPDH mRNA and CRH mRNA. Under current-clamp recording conditions, application of nicotine (1 μM) induced excitation in 92% (23/25) PVN CRH-mRNA-expressing neurons, which showed a significant increase in the spike firing rate accompanied by a depolarization of the membrane potential. Nicotine induced an increase in the spike firing rate of PVN CRH-mRNA-expressing neurons in a concentration-dependent manner. The half-effective concentration (EC50) of nicotine for increasing the spike firing rate of PVN CRH-mRNA-expressing neurons was 1.6 μM. Extracellular application of ionotropic glutamate receptor antagonist kynurenic acid (1 mM) abolished the nicotine-induced excitation of PVN CRH-mRNA-expressing neurons. Moreover, application of nicotine induced a significant increase in the spontaneous excitatory postsynaptic currents frequency, but without significantly altering the spontaneous excitatory postsynaptic currents amplitude of the CRH-mRNA-expressing neurons. Biocytin staining confirmed that the nicotine-sensitive CRH-mRNA-expressing neurons were located in the PVN parvocellular division. These results indicated that extracellular administration of nicotine indirectly excited PVN CRH-mRNA-expressing neurons, suggesting that nicotine modulated PVN CRH secretion by enhancement of both the presynaptic action potential drive and quantal glutamate release.
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Overactivity of Liver-Related Neurons in the Paraventricular Nucleus of the Hypothalamus: Electrophysiological Findings in db/db Mice. J Neurosci 2017; 37:11140-11150. [PMID: 29038244 DOI: 10.1523/jneurosci.1706-17.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 09/11/2017] [Accepted: 10/03/2017] [Indexed: 12/11/2022] Open
Abstract
Preautonomic neurons in the paraventricular nucleus (PVN) of the hypothalamus play a large role in the regulation of hepatic functions via the autonomic nervous system. Activation of hepatic sympathetic nerves increases glucose and lipid metabolism and contributes to the elevated hepatic glucose production observed in the type 2 diabetic condition. This augmented sympathetic output could originate from altered activity of liver-related PVN neurons. Remarkably, despite the importance of the brain-liver pathway, the cellular properties of liver-related neurons are not known. In this study, we provide the first evidence of overall activity of liver-related PVN neurons. Liver-related PVN neurons were identified with a retrograde, trans-synaptic, viral tracer in male lean and db/db mice and whole-cell patch-clamp recordings were conducted. In db/db mice, the majority of liver-related PVN neurons fired spontaneously; whereas, in lean mice the majority of liver-related PVN neurons were silent, indicating that liver-related PVN neurons are more active in db/db mice. Persistent, tonic inhibition was identified in liver-related PVN neurons; although, the magnitude of tonic inhibitory control was not different between lean and db/db mice. In addition, our study revealed that the transient receptor potential vanilloid type 1-dependent increase of excitatory neurotransmission was reduced in liver-related PVN neurons of db/db mice. These findings demonstrate plasticity of liver-related PVN neurons and a shift toward excitation in a diabetic mouse model. Our study suggests altered autonomic circuits at the level of the PVN, which can contribute to autonomic dysfunction and dysregulation of neural control of hepatic functions including glucose metabolism.SIGNIFICANCE STATEMENT A growing body of evidence suggests the importance of the autonomic control in the regulation of hepatic metabolism, which plays a major role in the development and progression of type 2 diabetes mellitus. Despite the importance of the brain-liver pathway, the overall activity of liver-related neurons in control and diabetic conditions is not known. This is a significant gap in knowledge, which prevents developing strategies to improve glucose homeostasis via altering the brain-liver pathway. One of the key findings of our study is the overall shift toward excitation in liver-related hypothalamic neurons in the diabetic condition. This overactivity may be one of the underlying mechanisms of elevated sympathetic activity known in metabolically compromised patients and animal models.
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Althammer F, Grinevich V. Diversity of oxytocin neurons: beyond magno- and parvocellular cell types? J Neuroendocrinol 2017; 30. [PMID: 29024187 DOI: 10.1111/jne.12549] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 10/09/2017] [Indexed: 01/31/2023]
Abstract
The hypothalamic neuropeptide oxytocin (OT), which is evolutionarily conserved among different species throughout the animal kingdom, is a key modulator of a variety of socio-emotional behaviors such as fear, trust and empathy. OT cells in the mammalian hypothalamus have been traditionally divided into two distinct types - magnocellular (magnOT) and parvocellular (parvOT) or preautonomic neurons. This distinction is based on OT cell sizes and shapes, projections, electrophysiological activity and functions. Indeed, while neuroendocrine magnOT neurons are known to primarily project their axons to the posterior pituitary and to a number of forebrain regions, non-neuroendocrine parvOT neurons have been seen as the main source of OT innervation of the brainstem and spinal cord to control autonomic functions and pain perception. However, very recent findings demonstrated distinct genetic profiles in OT neurons, allowing discrimination of at least four types of cells expressing OT. Furthermore, unexpected axonal projections of parvOT neurons to the forebrain and magnOT neurons to the midbrain have been newly reported. In this review, we focus on the detailed analysis of methods of distinction between OT cell types, in- and output sites, morphology as well as on the direct connectivity between OT neurons and its physiological significance. At the end, we propose a hypothesis that the central OT system is composed of more than just two OT cell types, which should be further verified by the application of available genetic and anatomical techniques. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Ferdinand Althammer
- Schaller Research Group on Neuropeptides at German Cancer Research Center (DKFZ), Heidelberg, 69120, Germany
| | - Valery Grinevich
- Schaller Research Group on Neuropeptides at German Cancer Research Center (DKFZ), Heidelberg, 69120, Germany
- CellNetworks Cluster of Excellence at the, University of Heidelberg, 69120, Heidelberg, Germany
- Central Institute of Mental Health, Mannheim, 68159, Germany
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McIsaac W, Ferguson AV. Glucose concentrations modulate brain-derived neurotrophic factor responsiveness of neurones in the paraventricular nucleus of the hypothalamus. J Neuroendocrinol 2017; 29. [PMID: 28258626 DOI: 10.1111/jne.12464] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 02/07/2017] [Accepted: 02/20/2017] [Indexed: 11/30/2022]
Abstract
The hypothalamic paraventricular nucleus (PVN) is critical for normal energy balance and has been shown to contain high levels of both brain-derived neurotrophic factor (BDNF) and tropomyosin-receptor kinase B mRNA. Microinjections of BDNF into the PVN increase energy expenditure, suggesting that BDNF plays an important role in energy homeostasis through direct actions in this nucleus. The present study aimed to examine the postsynaptic effects of BDNF on the membrane potential of PVN neurones, and also to determine whether extracellular glucose concentrations modulated these effects. We used hypothalamic PVN slices from male Sprague-Dawley rats to perform whole cell current-clamp recordings from PVN neurones. BDNF was bath applied at a concentration of 2 nmol L-1 and the effects on membrane potential determined. BDNF caused depolarisations in 54% of neurones (n=25; mean±SEM, 8.9±1.2 mV) and hyperpolarisations in 23% (n=11; -6.7±1.4 mV), whereas the remaining cells were unaffected. These effects were maintained in the presence of tetrodotoxin (n=9; 56% depolarised, 22% hyperpolarised, 22% nonresponders), or the GABAa antagonist bicuculline (n=12; 42% depolarised, 17% hyperpolarised, 41% nonresponders), supporting the conclusion that these effects on membrane potential were postsynaptic. Current-clamp recordings from PVN neurones next examined the effects of BDNF on these neurones at varying extracellular glucose concentrations. Larger proportions of PVN neurones hyperpolarised in response to BDNF as the glucose concentrations decreased [10 mmol L-1 glucose 23% (n=11) of neurones hyperpolarised, whereas, at 0.2 mmol L-1 glucose, 71% showed hyperpolarising effects (n=12)]. Our findings reveal that BDNF has direct GABAA independent effects on PVN neurones, which are modulated by local glucose concentrations. The latter observation further emphasises the critical importance of using physiologically relevant conditions in an investigation of the central pathways involved in the regulation of energy homeostasis.
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Affiliation(s)
- W McIsaac
- Centre for Neuroscience, Queens University, Kingston, ON, Canada
| | - A V Ferguson
- Centre for Neuroscience, Queens University, Kingston, ON, Canada
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A Unique "Angiotensin-Sensitive" Neuronal Population Coordinates Neuroendocrine, Cardiovascular, and Behavioral Responses to Stress. J Neurosci 2017; 37:3478-3490. [PMID: 28219987 DOI: 10.1523/jneurosci.3674-16.2017] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 01/20/2017] [Accepted: 02/13/2017] [Indexed: 01/19/2023] Open
Abstract
Stress elicits neuroendocrine, autonomic, and behavioral responses that mitigate homeostatic imbalance and ensure survival. However, chronic engagement of such responses promotes psychological, cardiovascular, and metabolic impairments. In recent years, the renin-angiotensin system has emerged as a key mediator of stress responding and its related pathologies, but the neuronal circuits that orchestrate these interactions are not known. These studies combine the use of the Cre-recombinase/loxP system in mice with optogenetics to structurally and functionally characterize angiotensin type-1a receptor-containing neurons of the paraventricular nucleus of the hypothalamus, the goal being to determine the extent of their involvement in the regulation of stress responses. Initial studies use neuroanatomical techniques to reveal that angiotensin type-1a receptors are localized predominantly to the parvocellular neurosecretory neurons of the paraventricular nucleus of the hypothalamus. These neurons are almost exclusively glutamatergic and send dense projections to the exterior portion of the median eminence. Furthermore, these neurons largely express corticotrophin-releasing hormone or thyrotropin-releasing hormone and do not express arginine vasopressin or oxytocin. Functionally, optogenetic stimulation of these neurons promotes the activation of the hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid axes, as well as a rise in systolic blood pressure. When these neurons are optogenetically inhibited, the activity of these neuroendocrine axes are suppressed and anxiety-like behavior in the elevated plus maze is dampened. Collectively, these studies implicate this neuronal population in the integration and coordination of the physiological responses to stress and may therefore serve as a potential target for therapeutic intervention for stress-related pathology.SIGNIFICANCE STATEMENT Chronic stress leads to an array of physiological responses that ultimately rouse psychological, cardiovascular, and metabolic impairments. As a consequence, there is an urgent need for the development of novel therapeutic approaches to prevent or dampen deleterious aspects of "stress." While the renin-angiotensin system has received some attention in this regard, the neural mechanisms by which this endocrine system may impact stress-related pathologies and consequently serve as targets for therapeutic intervention are not clear. The present studies provide substantial insight in this regard. That is, they reveal that a distinct population of angiotensin-sensitive neurons is integral to the coordination of stress responses. The implication is that this neuronal phenotype may serve as a target for stress-related disease.
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Loewen SP, Ferguson AV. Adropin acts in the rat paraventricular nucleus to influence neuronal excitability. Am J Physiol Regul Integr Comp Physiol 2017; 312:R511-R519. [PMID: 28100478 DOI: 10.1152/ajpregu.00517.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 01/13/2017] [Accepted: 01/14/2017] [Indexed: 01/28/2023]
Abstract
Adropin is a peptide hormone with cardiovascular and metabolic roles in the periphery, including effects on glucose and lipid homeostasis. Central administration of adropin has been shown to inhibit water intake in rats; however, the site at which central adropin acts has yet to be elucidated. The hypothalamic paraventricular nucleus (PVN), a critical autonomic control center, plays essential roles in the control of fluid balance, energy homeostasis, and cardiovascular regulation, and is, therefore, a potential target for centrally acting adropin. In the present study, we used whole cell patch-clamp techniques to examine the effects of adropin on the excitability of neurons within the PVN. All three neuronal subpopulations (magnocellular, preautonomic, and neuroendocrine) in the PVN were found to be responsive to bath-application of 10 nM adropin, which elicited responses in 68% of cells tested (n = 57/84). The majority of cells (58%) depolarized (5.2 ± 0.3 mV; n = 49) in response to adropin, whereas the remaining responsive cells (10%) hyperpolarized (-3.4 ± 0.5 mV; n = 8), effects that were shown to be concentration-dependent. Additionally, responses were maintained in the presence of 1 μM TTX in 75% of cells tested (n = 9/12), and voltage-clamp analysis revealed that adropin had no effect on the amplitude or frequency of excitatory or inhibitory postsynaptic currents (EPSCs and IPSCs) in PVN neurons, suggesting the peptide exerts direct, postsynaptic actions on these neurons. Collectively, these findings suggest central adropin may exert its physiological effects through direct actions on neurons in the PVN.
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Affiliation(s)
- Spencer P Loewen
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Alastair V Ferguson
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
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Zhang Y, Yu XJ, Chen WS, Gao HL, Liu KL, Shi XL, Fan XY, Jia LL, Cui W, Zhu GQ, Liu JJ, Kang YM. Exercise training attenuates renovascular hypertension partly via RAS- ROS- glutamate pathway in the hypothalamic paraventricular nucleus. Sci Rep 2016; 6:37467. [PMID: 27881877 PMCID: PMC5121597 DOI: 10.1038/srep37467] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 10/27/2016] [Indexed: 02/05/2023] Open
Abstract
Exercise training (ExT) has been reported to benefit hypertension; however, the exact mechanisms involved are unclear. We hypothesized that ExT attenuates hypertension, in part, through the renin-angiotensin system (RAS), reactive oxygen species (ROS), and glutamate in the paraventricular nucleus (PVN). Two-kidney, one-clip (2K1C) renovascular hypertensive rats were assigned to sedentary (Sed) or treadmill running groups for eight weeks. Dizocilpine (MK801), a glutamate receptor blocker, or losartan (Los), an angiotensin II type1 receptor (AT1-R) blocker, were microinjected into the PVN at the end of the experiment. We found that 2K1C rats had higher mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA). These rats also had excessive oxidative stress and overactivated RAS in PVN. Eight weeks of ExT significantly decreased MAP and RSNA in 2K1C hypertensive rats. ExT inhibited angiotensin-converting enzyme (ACE), AT1-R, and glutamate in the PVN, and angiotensin II (ANG II) in the plasma. Moreover, ExT attenuated ROS by augmenting copper/zinc superoxide dismutase (Cu/Zn-SOD) and decreasing p47phox and gp91phox in the PVN. MK801or Los significantly decreased blood pressure in rats. Together, these findings suggest that the beneficial effects of ExT on renovascular hypertension may be, in part, through the RAS-ROS-glutamate pathway in the PVN.
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Affiliation(s)
- Yan Zhang
- Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Xi'an Jiaotong University School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University Cardiovascular Research Center, Xi'an, 710061, China
| | - Xiao-Jing Yu
- Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Xi'an Jiaotong University School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University Cardiovascular Research Center, Xi'an, 710061, China
| | - Wen-Sheng Chen
- Department of Cardiovascular Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China
| | - Hong-Li Gao
- Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Xi'an Jiaotong University School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University Cardiovascular Research Center, Xi'an, 710061, China
| | - Kai-Li Liu
- Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Xi'an Jiaotong University School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University Cardiovascular Research Center, Xi'an, 710061, China
| | - Xiao-Lian Shi
- Department of Pharmacology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, China
| | - Xiao-Yan Fan
- Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Xi'an Jiaotong University School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University Cardiovascular Research Center, Xi'an, 710061, China
| | - Lin-Lin Jia
- Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Xi'an Jiaotong University School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University Cardiovascular Research Center, Xi'an, 710061, China
| | - Wei Cui
- Department of Endocrinology and Metabolism, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, China
| | - Guo-Qing Zhu
- Key Laboratory of Cardiovascular Disease and Molecular Intervention, Department of Physiology, Nanjing Medical University, Nanjing, 210029, China
| | - Jin-Jun Liu
- Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Xi'an Jiaotong University School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University Cardiovascular Research Center, Xi'an, 710061, China
| | - Yu-Ming Kang
- Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Xi'an Jiaotong University School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an Jiaotong University Cardiovascular Research Center, Xi'an, 710061, China
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48
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Lozić M, Tasić T, Martin A, Greenwood M, Šarenac O, Hindmarch C, Paton JF, Murphy D, Japundžić-Žigon N. Over-expression of V1A receptors in PVN modulates autonomic cardiovascular control. Pharmacol Res 2016; 114:185-195. [PMID: 27810519 DOI: 10.1016/j.phrs.2016.10.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 09/07/2016] [Accepted: 10/28/2016] [Indexed: 11/29/2022]
Abstract
The hypothalamic paraventricular nucleus (PVN) is a key integrative site for the neuroendocrine control of the circulation and of the stress response. It is also a major source of the neuropeptide hormone vasopressin (VP), and co-expresses V1a receptors (V1aR). We thus sought to investigate the role of V1aR in PVN in cardiovascular control in response to stress. Experiments were performed in male Wistar rats equipped with radiotelemetric device. The right PVN was transfected with adenoviral vectors (Ads) engineered to over-express V1aR along with an enhanced green fluorescent protein (eGFP) tag. Control groups were PVN transfected with Ads expressing eGFP alone, or wild-type rats (Wt). Rats were recorded with and without selective blockade of V1aR (V1aRX) in PVN under both baseline and stressed conditions. Blood pressure (BP), heart rate (HR), their short-term variabilities, and baroreflex sensitivity (BRS) were evaluated using spectral analysis and the sequence method, respectively. Under baseline physiological conditions,V1aR rats exhibited reduced BRS and a marked increase of BP and HR variability during exposure to stress. These effects were all prevented by V1aRX pretreatment. In Wt rats, V1aRX did not modify cardiovascular parameters under baseline conditions, and prevented BP variability increase by stress. However, V1aRX pretreatment did not modify baroreflex desensitization by stress in either rat strain. It follows that increased expression of V1aR in PVN influences autonomic cardiovascular regulation and demarcates vulnerability to stress. We thus suggest a possible role of hypothalamic V1aR in cardiovascular pathology.
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Affiliation(s)
- Maja Lozić
- Institute of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine University of Belgrade, 11000 Belgrade, Serbia
| | - Tatjana Tasić
- Institute of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine University of Belgrade, 11000 Belgrade, Serbia
| | - Andrew Martin
- Molecular Neuroendocrinology Research Group, The Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol, England BS1 3NY, United Kingdom
| | - Michael Greenwood
- Molecular Neuroendocrinology Research Group, The Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol, England BS1 3NY, United Kingdom
| | - Olivera Šarenac
- Institute of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine University of Belgrade, 11000 Belgrade, Serbia; Molecular Neuroendocrinology Research Group, The Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol, England BS1 3NY, United Kingdom
| | - Charles Hindmarch
- Molecular Neuroendocrinology Research Group, The Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol, England BS1 3NY, United Kingdom; Department of Physiology, University of Malaya, University of Malaya, Kuala Lumpur 50603, Malaysia
| | - Julian F Paton
- School of Physiology and Pharmacology, University of Bristol, Bristol, England BS8 1TD, United Kingdom
| | - David Murphy
- Molecular Neuroendocrinology Research Group, The Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol, England BS1 3NY, United Kingdom; Department of Physiology, University of Malaya, University of Malaya, Kuala Lumpur 50603, Malaysia
| | - Nina Japundžić-Žigon
- Institute of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine University of Belgrade, 11000 Belgrade, Serbia.
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Pitra S, Feng Y, Stern JE. Mechanisms underlying prorenin actions on hypothalamic neurons implicated in cardiometabolic control. Mol Metab 2016; 5:858-868. [PMID: 27688999 PMCID: PMC5034613 DOI: 10.1016/j.molmet.2016.07.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 07/26/2016] [Accepted: 07/27/2016] [Indexed: 02/07/2023] Open
Abstract
Background Hypertension and obesity are highly interrelated diseases, being critical components of the metabolic syndrome. Despite the growing prevalence of this syndrome in the world population, efficient therapies are still missing. Thus, identification of novel targets and therapies are warranted. An enhanced activity of the hypothalamic renin-angiotensin system (RAS), including the recently discovered prorenin (PR) and its receptor (PRR), has been implicated as a common mechanism underlying aberrant sympatho-humoral activation that contributes to both metabolic and cardiovascular dysregulation in the metabolic syndrome. Still, the identification of precise neuronal targets, cellular mechanisms and signaling pathways underlying PR/PRR actions in cardiovascular- and metabolic related hypothalamic nuclei remain unknown. Methods and results Using a multidisciplinary approach including patch-clamp electrophysiology, live calcium imaging and immunohistochemistry, we aimed to elucidate cellular mechanisms underlying PR/PRR actions within the hypothalamic supraoptic (SON) and paraventricular nucleus (PVN), key brain areas previously involved in cardiometabolic regulation. We show for the first time that PRR is expressed in magnocellular neurosecretory cells (MNCs), and to a lesser extent, in presympathetic PVN neurons (PVNPS). Moreover, we show that while PRR activation efficiently stimulates the firing activity of both MNCs and PVNPS neurons, these effects involved AngII-independent and AngII-dependent mechanisms, respectively. In both cases however, PR excitatory effects involved an increase in intracellular Ca2+ levels and a Ca2+-dependent inhibition of a voltage-gated K+ current. Conclusions We identified novel neuronal targets and cellular mechanisms underlying PR/PRR actions in critical hypothalamic neurons involved in cardiometabolic regulation. This fundamental mechanistic information regarding central PR/PRR actions is essential for the development of novel RAS-based therapeutic targets for the treatment of cardiometabolic disorders in obesity and hypertension. PRR is expressed in SON and PVN neurosecretory and presympathetic neurons. PRR activation stimulates firing activity of SON and PVN neurons. PR/PRR effects on neurosecretory neurons are AngII-independent. PR/PRR effects on presympathetic neurons are AngII-dependent. PR inhibits a voltage-gated K+ current in a Ca2+-dependent manner.
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Affiliation(s)
- Soledad Pitra
- Department of Physiology, Medical College of Georgia, Augusta University, United States
| | - Yumei Feng
- Departments of Pharmacology, Physiology and Cell Biology, Center for Cardiovascular Research, University of Nevada School of Medicine, United States
| | - Javier E Stern
- Department of Physiology, Medical College of Georgia, Augusta University, United States.
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50
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de Kloet AD, Pitra S, Wang L, Hiller H, Pioquinto DJ, Smith JA, Sumners C, Stern JE, Krause EG. Angiotensin Type-2 Receptors Influence the Activity of Vasopressin Neurons in the Paraventricular Nucleus of the Hypothalamus in Male Mice. Endocrinology 2016; 157:3167-80. [PMID: 27267713 PMCID: PMC4967126 DOI: 10.1210/en.2016-1131] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
It is known that angiotensin-II acts at its type-1 receptor to stimulate vasopressin (AVP) secretion, which may contribute to angiotensin-II-induced hypertension. Less well known is the impact of angiotensin type-2 receptor (AT2R) activation on these processes. Studies conducted in a transgenic AT2R enhanced green fluorescent protein reporter mouse revealed that although AT2R are not themselves localized to AVP neurons within the paraventricular nucleus of the hypothalamus (PVN), they are localized to neurons that extend processes into the PVN. In the present set of studies, we set out to characterize the origin, phenotype, and function of nerve terminals within the PVN that arise from AT2R-enhanced green fluorescent protein-positive neurons and synapse onto AVP neurons. Initial experiments combined genetic and neuroanatomical techniques to determine that γ-aminobutyric acid (GABA)ergic neurons derived from the peri-PVN area containing AT2R make appositions onto AVP neurons within the PVN, thereby positioning AT2R to negatively regulate neuroendocrine secretion. Subsequent patch-clamp electrophysiological experiments revealed that selective activation of AT2R in the peri-PVN area using compound 21 facilitates inhibitory (ie, GABAergic) neurotransmission and leads to reduced activity of AVP neurons within the PVN. Final experiments determined the functional impact of AT2R activation by testing the effects of compound 21 on plasma AVP levels. Collectively, these experiments revealed that AT2R expressing neurons make GABAergic synapses onto AVP neurons that inhibit AVP neuronal activity and suppress baseline systemic AVP levels. These findings have direct implications in the targeting of AT2R for disorders of AVP secretion and also for the alleviation of high blood pressure.
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