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Althammer F, Roy RK, Kirchner MK, Lira EC, Schimmer S, Charlet A, Grinevich V, Stern JE. Impaired oxytocin signaling in the central amygdala in rats with chronic heart failure. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.22.568271. [PMID: 38045233 PMCID: PMC10690294 DOI: 10.1101/2023.11.22.568271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Aims Heart failure (HF) patients often suffer from cognitive decline, depression, and mood impairments, but the molecular signals and brain circuits underlying these effects remain elusive. The hypothalamic neuropeptide oxytocin (OT) is critically involved in the regulation of mood, and OTergic signaling in the central amygdala (CeA) is a key mechanism controlling emotional responses including anxiety-like behaviors. Based on this, we used in this study a well-established ischemic rat HF model and aimed to study alterations in the hypothalamus-to-CeA OTergic circuit. Methods and Results To study potential HF-induced changes in the hypothalamus-to-CeA OTertic circuit, we combined patch-clamp electrophysiology, immunohistochemical analysis, RNAScope assessment of OTR mRNA, brain region-specific stereotaxic injections of viral vectors and retrograde tracing, optogenetic stimulation and OT biosensors in the ischemic HF model. We found that most of OTergic innervation of the central amygdala (CeA) originated from the hypothalamic supraoptic nucleus (SON). While no differences in the numbers of SON→CeA OTertic neurons (or their OT content) was observed between sham and HF rats, we did observe a blunted content and release of OT from axonal terminals within the CeA. Moreover, we report downregulation of neuronal and astrocytic OT receptors, and impaired OTR-driven GABAergic synaptic activity within the CeA microcircuit of rats with HF. Conclusions Our study provides first evidence that HF rats display various perturbations in the hypothalamus-to-amygdala OTergic circuit, and lays the foundation for future translational studies targeting either the OT system or GABAergic amygdala GABA microcircuit to ameliorate depression or mood impairments in rats or patients with chronic HF.
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Affiliation(s)
- Ferdinand Althammer
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA, USA
- Institute of Human Genetics, Heidelberg University, Heidelberg
| | - Ranjan K. Roy
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA, USA
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | - Matthew K. Kirchner
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA, USA
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | - Elba Campos Lira
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA, USA
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | - Stephanie Schimmer
- Department of Neuropeptide Research in Psychiatry, Central Institute of Mental Health, Heidelberg University, Mannheim, Germany
| | - Alexandre Charlet
- Centre National de la Recherche Scientifique and University of Strasbourg, Institute of Cellular and Integrative Neuroscience, Strasbourg, France
| | - Valery Grinevich
- Department of Neuropeptide Research in Psychiatry, Central Institute of Mental Health, Heidelberg University, Mannheim, Germany
| | - Javier E. Stern
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA, USA
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
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Althammer F, Roy RK, Kirchner MK, Campos-Lira E, Whitley KE, Davis S, Montanez J, Ferreira-Neto HC, Danh J, Feresin R, Biancardi VC, Zafar U, Parent MB, Stern JE. Angiotensin II-Mediated Neuroinflammation in the Hippocampus Contributes to Neuronal Deficits and Cognitive Impairment in Heart Failure Rats. Hypertension 2023; 80:1258-1273. [PMID: 37035922 PMCID: PMC10192104 DOI: 10.1161/hypertensionaha.123.21070] [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: 02/10/2023] [Accepted: 03/22/2023] [Indexed: 04/11/2023]
Abstract
BACKGROUND Heart failure (HF) is a debilitating disease affecting >64 million people worldwide. In addition to impaired cardiovascular performance and associated systemic complications, most patients with HF suffer from depression and substantial cognitive decline. Although neuroinflammation and brain hypoperfusion occur in humans and rodents with HF, the underlying neuronal substrates, mechanisms, and their relative contribution to cognitive deficits in HF remains unknown. METHODS To address this critical gap in our knowledge, we used a well-established HF rat model that mimics clinical outcomes observed in the human population, along with a multidisciplinary approach combining behavioral, electrophysiological, neuroanatomical, molecular and systemic physiological approaches. RESULTS Our studies support neuroinflammation, hypoperfusion/hypoxia, and neuronal deficits in the hippocampus of HF rats, which correlated with the progression and severity of the disease. An increased expression of AT1aRs (Ang II [angiotensin II] receptor type 1a) in hippocampal microglia preceded the onset of neuroinflammation. Importantly, blockade of AT1Rs with a clinically used therapeutic drug (Losartan), and delivered in a clinically relevant manner, efficiently reversed neuroinflammatory end points (but not hypoxia ones), resulting in turn in improved cognitive performance in HF rats. Finally, we show than circulating Ang II can leak and access the hippocampal parenchyma in HF rats, constituting a possible source of Ang II initiating the neuroinflammatory signaling cascade in HF. CONCLUSIONS In this study, we identified a neuronal substrate (hippocampus), a mechanism (Ang II-driven neuroinflammation) and a potential neuroprotective therapeutic target (AT1aRs) for the treatment of cognitive deficits in HF.
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Affiliation(s)
- Ferdinand Althammer
- Center for Neuroinflammation and Cardiometabolic Diseases,
Georgia State University, GA, USA
| | - Ranjan K. Roy
- Center for Neuroinflammation and Cardiometabolic Diseases,
Georgia State University, GA, USA
| | - Matthew K. Kirchner
- Center for Neuroinflammation and Cardiometabolic Diseases,
Georgia State University, GA, USA
| | - Elba Campos-Lira
- Center for Neuroinflammation and Cardiometabolic Diseases,
Georgia State University, GA, USA
- Neuroscience Institute, Georgia State University, GA,
USA
| | | | - Steven Davis
- Neuroscience Institute, Georgia State University, GA,
USA
| | - Juliana Montanez
- Center for Neuroinflammation and Cardiometabolic Diseases,
Georgia State University, GA, USA
| | | | - Jessica Danh
- Department of Nutrition, Georgia State University, Atlanta,
GA 30302, USA
| | - Rafaela Feresin
- Department of Nutrition, Georgia State University, Atlanta,
GA 30302, USA
| | - Vinicia Campana Biancardi
- Anatomy, Physiology, & Pharmacology, College of
Veterinary Medicine, Auburn University, Auburn, AL, USA
| | - Usama Zafar
- Center for Neuroinflammation and Cardiometabolic Diseases,
Georgia State University, GA, USA
- Neuroscience Institute, Georgia State University, GA,
USA
| | - Marise B. Parent
- Center for Neuroinflammation and Cardiometabolic Diseases,
Georgia State University, GA, USA
- Neuroscience Institute, Georgia State University, GA,
USA
- Department of Psychology, Georgia State University,
Atlanta, GA 30302, USA
| | - Javier E. Stern
- Center for Neuroinflammation and Cardiometabolic Diseases,
Georgia State University, GA, USA
- Neuroscience Institute, Georgia State University, GA,
USA
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Szczepańska-Sadowska E, Żera T. Vasopressin: a possible link between hypoxia and hypertension. EXPLORATION OF MEDICINE 2022. [DOI: 10.37349/emed.2022.00103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Cardiovascular and respiratory diseases are frequently associated with transient and prolonged hypoxia, whereas hypoxia exerts pro-hypertensive effects, through stimulation of the sympathetic system and release of pressor endocrine factors. This review is focused on the role of arginine vasopressin (AVP) in dysregulation of the cardiovascular system during hypoxia associated with cardiovascular disorders. AVP is synthesized mainly in the neuroendocrine neurons of the hypothalamic paraventricular nucleus (PVN) and supraoptic nucleus (SON), which send axons to the posterior pituitary and various regions of the central nervous system (CNS). Vasopressinergic neurons are innervated by multiple neuronal projections releasing several neurotransmitters and other regulatory molecules. AVP interacts with V1a, V1b and V2 receptors that are present in the brain and peripheral organs, including the heart, vessels, lungs, and kidneys. Release of vasopressin is intensified during hypernatremia, hypovolemia, inflammation, stress, pain, and hypoxia which frequently occur in cardiovascular patients, and blood AVP concentration is markedly elevated in cardiovascular diseases associated with hypoxemia. There is evidence that hypoxia stimulates AVP release through stimulation of chemoreceptors. It is suggested that acting in the carotid bodies, AVP may fine-tune respiratory and hemodynamic responses to hypoxia and that this effect is intensified in hypertension. There is also evidence that during hypoxia, augmentation of pro-hypertensive effects of vasopressin may result from inappropriate interaction of this hormone with other compounds regulating the cardiovascular system (catecholamines, angiotensins, natriuretic peptides, steroids, nitric oxide). In conclusion, current literature indicates that abnormal mutual interactions between hypoxia and vasopressin may significantly contribute to pathogenesis of hypertension.
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Affiliation(s)
- Ewa Szczepańska-Sadowska
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, 02-097 Warsaw, Poland
| | - Tymoteusz Żera
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, 02-097 Warsaw, Poland
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Ando S, Mizutani H, Muramatsu M, Hagihara Y, Mishima H, Kondo R, Suzuki Y, Imaizumi Y, Yamamura H. Involvement of small-conductance Ca2+-activated K+ (SKCa2) channels in spontaneous Ca2+ oscillations in rat pinealocytes. Biochem Biophys Res Commun 2022; 615:157-162. [DOI: 10.1016/j.bbrc.2022.05.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 05/14/2022] [Indexed: 11/02/2022]
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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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Aikins AO, Nguyen DH, Paundralingga O, Farmer GE, Shimoura CG, Brock C, Cunningham JT. Cardiovascular Neuroendocrinology: Emerging Role for Neurohypophyseal Hormones in Pathophysiology. Endocrinology 2021; 162:6247962. [PMID: 33891015 PMCID: PMC8234498 DOI: 10.1210/endocr/bqab082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Indexed: 11/19/2022]
Abstract
Arginine vasopressin (AVP) and oxytocin (OXY) are released by magnocellular neurosecretory cells that project to the posterior pituitary. While AVP and OXY currently receive more attention for their contributions to affiliative behavior, this mini-review discusses their roles in cardiovascular function broadly defined to include indirect effects that influence cardiovascular function. The traditional view is that neither AVP nor OXY contributes to basal cardiovascular function, although some recent studies suggest that this position might be re-evaluated. More evidence indicates that adaptations and neuroplasticity of AVP and OXY neurons contribute to cardiovascular pathophysiology.
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Affiliation(s)
- Ato O Aikins
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - Dianna H Nguyen
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
- Texas College of Osteopathic Medicine, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - Obed Paundralingga
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - George E Farmer
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - Caroline Gusson Shimoura
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - Courtney Brock
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
| | - J Thomas Cunningham
- Department of Physiology and Anatomy, Graduate School of Biomedical Sciences, UNT Health Science Center, Fort Worth, TX 76107, USA
- Correspondence: J. Thomas Cunningham Department of Physiology & Anatomy CBH 338 UNT Health Science Center 3500 Camp Bowie Blvd Fort Worth, TX 76107, USA.
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Parent MB, Ferreira-Neto HC, Kruemmel AR, Althammer F, Patel AA, Keo S, Whitley KE, Cox DN, Stern JE. Heart failure impairs mood and memory in male rats and down-regulates the expression of numerous genes important for synaptic plasticity in related brain regions. Behav Brain Res 2021; 414:113452. [PMID: 34274373 DOI: 10.1016/j.bbr.2021.113452] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 05/21/2021] [Accepted: 07/08/2021] [Indexed: 12/01/2022]
Abstract
Chronic heart failure (HF) is a serious disorder that afflicts more than 26 million patients worldwide. HF is comorbid with depression, anxiety and memory deficits that have serious implications for quality of life and self-care in patients who have HF. Still, there are few studies that have assessed the effects of severely reduced ejection fraction (≤40 %) on cognition in non-human animal models. Moreover, limited information is available regarding the effects of HF on genetic markers of synaptic plasticity in brain areas critical for memory and mood regulation. We induced HF in male rats and tested mood and anxiety (sucrose preference and elevated plus maze) and memory (spontaneous alternation and inhibitory avoidance) and measured the simultaneous expression of 84 synaptic plasticity-associated genes in dorsal (DH) and ventral hippocampus (VH), basolateral (BLA) and central amygdala (CeA) and prefrontal cortex (PFC). We also included the hypothalamic paraventricular nucleus (PVN), which is implicated in neurohumoral activation in HF. Our results show that rats with severely reduced ejection fraction recapitulate behavioral symptoms seen in patients with chronic HF including, increased anxiety and impaired memory in both tasks. HF also downregulated several synaptic-plasticity genes in PFC and PVN, moderate decreases in DH and CeA and minimal effects in BLA and VH. Collectively, these findings identify candidate brain areas and molecular mechanisms underlying HF-induced disturbances in mood and memory.
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Affiliation(s)
- Marise B Parent
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | | | | | | | - Atit A Patel
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | - Sreinick Keo
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | | | - Daniel N Cox
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
| | - Javier E Stern
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA.
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8
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Althammer F, Ferreira-Neto HC, Rubaharan M, Roy RK, Patel AA, Murphy A, Cox DN, Stern JE. Three-dimensional morphometric analysis reveals time-dependent structural changes in microglia and astrocytes in the central amygdala and hypothalamic paraventricular nucleus of heart failure rats. J Neuroinflammation 2020; 17:221. [PMID: 32703230 PMCID: PMC7379770 DOI: 10.1186/s12974-020-01892-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 07/08/2020] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Cardiovascular diseases, including heart failure, are the most common cause of death globally. Recent studies support a high degree of comorbidity between heart failure and cognitive and mood disorders resulting in memory loss, depression, and anxiety. While neuroinflammation in the hypothalamic paraventricular nucleus contributes to autonomic and cardiovascular dysregulation in heart failure, mechanisms underlying cognitive and mood disorders in this disease remain elusive. The goal of this study was to quantitatively assess markers of neuroinflammation (glial morphology, cytokines, and A1 astrocyte markers) in the central amygdala, a critical forebrain region involved in emotion and cognition, and to determine its time course and correlation to disease severity during the progression of heart failure. METHODS We developed and implemented a comprehensive microglial/astrocyte profiler for precise three-dimensional morphometric analysis of individual microglia and astrocytes in specific brain nuclei at different time points during the progression of heart failure. To this end, we used a well-established ischemic heart failure rat model. Morphometric studies were complemented with quantification of various pro-inflammatory cytokines and A1/A2 astrocyte markers via qPCR. RESULTS We report structural remodeling of central amygdala microglia and astrocytes during heart failure that affected cell volume, surface area, filament length, and glial branches, resulting overall in somatic swelling and deramification, indicative of a change in glial state. These changes occurred in a time-dependent manner, correlated with the severity of heart failure, and were delayed compared to changes in the hypothalamic paraventricular nucleus. Morphometric changes correlated with elevated mRNA levels of pro-inflammatory cytokines and markers of reactive A1-type astrocytes in the paraventricular nucleus and central amygdala during heart failure. CONCLUSION We provide evidence that in addition to the previously described hypothalamic neuroinflammation implicated in sympathohumoral activation during heart failure, microglia, and astrocytes within the central amygdala also undergo structural remodeling indicative of glial shifts towards pro-inflammatory phenotypes. Thus, our studies suggest that neuroinflammation in the amygdala stands as a novel pathophysiological mechanism and potential therapeutic target that could be associated with emotional and cognitive deficits commonly observed at later stages during the course of heart failure.
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Affiliation(s)
- Ferdinand Althammer
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, USA
| | | | | | - Ranjan K Roy
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, USA
| | - Atit A Patel
- Neuroscience Institute, Georgia State University, Atlanta, USA
| | - Anne Murphy
- Neuroscience Institute, Georgia State University, Atlanta, USA
| | - Daniel N Cox
- Neuroscience Institute, Georgia State University, Atlanta, USA
| | - Javier E Stern
- Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, USA.
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Japundžić-Žigon N, Lozić M, Šarenac O, Murphy D. Vasopressin & Oxytocin in Control of the Cardiovascular System: An Updated Review. Curr Neuropharmacol 2020; 18:14-33. [PMID: 31544693 PMCID: PMC7327933 DOI: 10.2174/1570159x17666190717150501] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 06/03/2019] [Accepted: 07/06/2019] [Indexed: 01/19/2023] Open
Abstract
Since the discovery of vasopressin (VP) and oxytocin (OT) in 1953, considerable knowledge has been gathered about their roles in cardiovascular homeostasis. Unraveling VP vasoconstrictor properties and V1a receptors in blood vessels generated powerful hemostatic drugs and drugs effective in the treatment of certain forms of circulatory collapse (shock). Recognition of the key role of VP in water balance via renal V2 receptors gave birth to aquaretic drugs found to be useful in advanced stages of congestive heart failure. There are still unexplored actions of VP and OT on the cardiovascular system, both at the periphery and in the brain that may open new venues in treatment of cardiovascular diseases. After a brief overview on VP, OT and their peripheral action on the cardiovascular system, this review focuses on newly discovered hypothalamic mechanisms involved in neurogenic control of the circulation in stress and disease.
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Affiliation(s)
| | - Maja Lozić
- Faculty of Medicine, University of Belgrade, Belgrade, Serbia
| | - Olivera Šarenac
- Faculty of Medicine, University of Belgrade, Belgrade, Serbia
| | - David Murphy
- School of Clinical Sciences, University of Bristol, Bristol, United Kingdom
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10
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Ferreira-Neto HC, Stern JE. Functional coupling between NMDA receptors and SK channels in rat hypothalamic magnocellular neurons: altered mechanisms during heart failure. J Physiol 2019; 599:507-520. [PMID: 31667845 DOI: 10.1113/jp278910] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 10/28/2019] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS Glutamatergic NMDA receptors (NMDARs) and small conductance Ca2+ -activated K+ (SK) channels are critical synaptic and intrinsic mechanisms, respectively, that regulate the activity of hypothalamic magnocellular neurosecretory neurons (MNNs). In this work, we investigated whether NMDARs and SK channels in MNNs are functionally coupled, and whether an altered coupling may contribute to exacerbated neuronal activity in this condition. We report that NMDARs and SK channels form a functional Ca2+ -dependent negative feedback loop that restrains the excitatory effect on membrane potential and firing activity evoked by NMDAR activation. The negative feedback loop between NMDARs and SK channels was blunted or absent in MNNs of heart failure (HF) rats. These results help us better understand how synaptic and intrinsic mechanisms regulate hypothalamic neuronal activity, as well as how changes in the interaction among these disparate mechanisms contribute to altered neuronal activity during prevalent neurogenic cardiovascular diseases. ABSTRACT Glutamatergic NMDA receptors (NMDARs) and small conductance Ca2+ -activated K+ (SK) channels are critical synaptic and intrinsic mechanisms, respectively, that regulate the activity of hypothalamic magnocellular neurosecretory neurons (MNNs), both under physiological and pathological states, such as lactation and heart failure (HF). However, whether NMDARs and SK channels in MNNs are functionally coupled, and whether changes in this coupling contribute to exacerbated neuronal activity during HF is at present unknown. In the present study, we addressed these questions using patch-clamp electrophysiology and confocal Ca2+ imaging in a rat model of ischaemic HF. We found that in MNNs of sham rats, blockade of SK channels with apamin (200 nM) significantly increased the magnitude of an NMDAR-evoked current (INMDA ). We also observed that blockade of SK channels potentiated NMDAR-evoked firing, and abolished spike frequency adaptation in MNNs from sham, but not HF rats. Importantly, a larger INMDA -ΔCa2+ response was observed under basal conditions in HF compared to sham rats. Finally, we found that dialysing recorded cells with the Ca2+ chelator BAPTA (10 mM) increased the magnitude of INMDA in MNNs from both sham and HF rats, and occluded the effects of apamin in the former. Together our studies demonstrate that in MNNs, NMDARs and SK channels are functionally coupled, forming a local negative feedback loop that restrains the excitatory effect evoked by NMDAR activation. Moreover, our studies also support a blunted NMDAR-SK channel coupling in MNNs of HF rats, establishing it as a pathophysiological mechanism contributing to exacerbated hypothalamic neuronal activity during this prevalent neurogenic cardiovascular disease.
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Affiliation(s)
| | - Javier E Stern
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
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11
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Exploration of Ion Channels in the Clitoris: a Review. CURRENT SEXUAL HEALTH REPORTS 2019. [DOI: 10.1007/s11930-019-00206-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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12
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Pitra S, Worker CJ, Feng Y, Stern JE. Exacerbated effects of prorenin on hypothalamic magnocellular neuronal activity and vasopressin plasma levels during salt-sensitive hypertension. Am J Physiol Heart Circ Physiol 2019; 317:H496-H504. [PMID: 31274353 DOI: 10.1152/ajpheart.00063.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Accumulating evidence supports that the brain renin-angiotensin system (RAS), including prorenin (PR) and its receptor (PRR), two newly discovered RAS players, contribute to sympathoexcitation in salt-sensitive hypertension. Still, whether PR also contributed to elevated circulating levels of neurohormones such as vasopressin (VP) during salt-sensitive hypertension, and if so, what are the precise underlying mechanisms, remains to be determined. To address these questions, we obtained patch-clamp recordings from hypothalamic magnocellular neurosecretory neurons (MNNs) that synthesize the neurohormones oxytocin and VP in acute hypothalamic slices obtained from sham and deoxycorticosterone acetate (DOCA)-salt-treated hypertensive rats. We found that focal application of PR markedly increased membrane excitability and firing responses in MNNs of DOCA-salt, compared with sham rats. This effect included a shorter latency to spike initiation and increased numbers of spikes in response to depolarizing stimuli and was mediated by a more robust inhibition of A-type K+ channels in DOCA-salt compared with sham rats. On the other hand, the afterhyperpolarizing potential mediated by the activation of Ca2+-dependent K+ channel was not affected by PR. mRNA expression of PRR, VP, and the Kv4.3 K+ channel subunit in the supraoptic nucleus of DOCA-salt hypertensive rats was increased compared with sham rats. Finally, we report a significant decrease of plasma VP levels in neuron-selective PRR knockdown mice treated with DOCA-salt, compared with wild-type DOCA-salt-treated mice. Together, these results support that activation of PRR contributes to increased excitability and firing discharge of MNNs and increased plasma levels of VP in DOCA-salt hypertension.NEW & NOTEWORTHY Our studies support that prorenin (PR) and its receptor (PRR) within the hypothalamus contribute to elevated plasma vasopressin levels in deoxycorticosterone acetate-salt hypertension, in part because of an exacerbated effect of PR on magnocellular neurosecretory neuron excitability; Moreover, our study implicates A-type K+ channels as key underlying molecular targets mediating these effects. Thus, PR/PRR stands as a novel therapeutic target for the treatment of neurohumoral activation in salt-sensitive hypertension.
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Affiliation(s)
- Soledad Pitra
- Department of Physiology, Medical College of Georgia, Augusta University, Georgia
| | - Caleb J Worker
- Department of Pharmacology, Physiology, and Cell Biology, University of Nevada, Reno, Nevada
| | - Yumei Feng
- Department of Pharmacology, Physiology, and Cell Biology, University of Nevada, Reno, Nevada
| | - Javier E Stern
- Department of Physiology, Medical College of Georgia, Augusta University, Georgia
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Shenton FC, Pyner S. Transient receptor potential vanilloid type 4 is expressed in vasopressinergic neurons within the magnocellular subdivision of the rat paraventricular nucleus of the hypothalamus. J Comp Neurol 2018; 526:3035-3044. [PMID: 30078222 PMCID: PMC6492187 DOI: 10.1002/cne.24514] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 07/19/2018] [Accepted: 07/19/2018] [Indexed: 01/28/2023]
Abstract
Changes in plasma osmolality can drive changes in the output from brain centres known to control cardiovascular homeostasis, such as the paraventricular nucleus of the hypothalamus (PVN). Within the PVN hypotonicity reduces the firing rate of parvocellular neurons, a neuronal pool known to be involved in modulating sympathetic vasomotor tone. Also present in the PVN is the transient receptor potential vanilloid type 4 (TRPV4) ion channel. Activation of TRPV4 within the PVN mimics the reduction in firing rate of the parvocellular neurons but it is unknown if these neurons express the channel. We used neuronal tracing and immunohistochemistry to investigate which neurons expressed the TRPV4 ion channel protein and its relationship with neurons known to play a role in plasma volume regulation. Spinally projecting preautonomic neurons within the PVN were labelled after spinal cord injection of FluoroGold (FG). This was followed by immunolabelling with anti‐TRPV4 antibody in combination with either anti‐oxytocin (OXT) or anti‐vasopressin (AVP). The TRPV4 ion channel was expressed on 63% of the vasopressinergic magnocellular neurosecretory cells found predominantly within the posterior magnocellular division of the PVN. Oxytocinergic neurons and FG labelled preautonomic neurons were present in the same location, but were distinct from the TRPV4/vasopressin expressing neurons. Vasopressinergic neurons within the supraoptic nucleus (SON) were also found to express TRPV4 and the fibres extending between the SON and PVN. In conclusion within the PVN, TRPV4 is well placed to respond to changes in osmolality by regulating vasopressin secretion, which in turn influences sympathetic output via preautonomic neurons.
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Affiliation(s)
- F C Shenton
- Department of Biosciences, Durham University, Durham, UK
| | - S Pyner
- Department of Biosciences, Durham University, Durham, UK
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Abstract
Hypertension is a prevalent and major health problem, involving a complex integration of different organ systems, including the central nervous system (CNS). The CNS and the hypothalamus in particular are intricately involved in the pathogenesis of hypertension. In fact, evidence supports altered hypothalamic neuronal activity as a major factor contributing to increased sympathetic drive and increased blood pressure. Several mechanisms have been proposed to contribute to hypothalamic-driven sympathetic activity, including altered ion channel function. Ion channels are critical regulators of neuronal excitability and synaptic function in the brain and, thus, important for blood pressure homeostasis regulation. These include sodium channels, voltage-gated calcium channels, and potassium channels being some of them already identified in hypothalamic neurons. This brief review summarizes the hypothalamic ion channels that may be involved in hypertension, highlighting recent findings that suggest that hypothalamic ion channel modulation can affect the central control of blood pressure and, therefore, suggesting future development of interventional strategies designed to treat hypertension.
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Affiliation(s)
- Vera Geraldes
- Instituto de Fisiologia, Universidade de Lisboa, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisbon, Portugal
| | - Sérgio Laranjo
- Instituto de Fisiologia, Universidade de Lisboa, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisbon, Portugal
| | - Isabel Rocha
- Instituto de Fisiologia, Universidade de Lisboa, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisbon, Portugal. .,Centro Cardiovascular da Universidade de Lisboa, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisbon, Portugal.
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15
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Pittman QJ. Hypothalamic neurons out of control. J Physiol 2017; 595:6375. [PMID: 28815593 DOI: 10.1113/jp274882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Quentin J Pittman
- Hotchkiss Brain Institute and Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada, T2N 4N1
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