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Salgado-Mozo S, Thirouin ZS, Wyrosdic JC, García-Hernández U, Bourque CW. Na X Channel Is a Physiological [Na +] Detector in Oxytocin- and Vasopressin-Releasing Magnocellular Neurosecretory Cells of the Rat Supraoptic Nucleus. J Neurosci 2023; 43:8306-8316. [PMID: 37783507 PMCID: PMC10711705 DOI: 10.1523/jneurosci.1203-23.2023] [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: 06/29/2023] [Revised: 09/08/2023] [Accepted: 09/25/2023] [Indexed: 10/04/2023] Open
Abstract
The Scn7A gene encodes NaX, an atypical noninactivating Na+ channel, whose expression in sensory circumventricular organs is essential to maintain homeostatic responses for body fluid balance. However, NaX has also been detected in homeostatic effector neurons, such as vasopressin (VP)-releasing magnocellular neurosecretory cells (MNCVP) that secrete VP (antidiuretic hormone) into the bloodstream in response to hypertonicity and hypernatremia. Yet, the physiological relevance of NaX expression in these effector cells remains unclear. Here, we show that rat MNCVP in males and females is depolarized and excited in proportion with isosmotic increases in [Na+]. These responses were caused by an inward current resulting from a cell-autonomous increase in Na+ conductance. The Na+-evoked current was unaffected by blockers of other Na+-permeable ion channels but was significantly reduced by shRNA-mediated knockdown of Scn7A expression. Furthermore, reducing the density of NaX channels selectively impaired the activation of MNCVP by systemic hypernatremia without affecting their responsiveness to hypertonicity in vivo These results identify NaX as a physiological Na+ sensor, whose expression in MNCVP contributes to the generation of homeostatic responses to hypernatremia.SIGNIFICANCE STATEMENT In this study, we provide the first direct evidence showing that the sodium-sensing channel encoded by the Scn7A gene (NaX) mediates cell-autonomous sodium detection by MNCs in the low millimolar range and that selectively reducing the expression of these channels in MNCs impairs their activation in response to a physiologically relevant sodium stimulus in vitro and in vivo These data reveal that NaX operates as a sodium sensor in these cells and that the endogenous sensory properties of osmoregulatory effector neurons contribute to their homeostatic activation in vivo.
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Affiliation(s)
- Sandra Salgado-Mozo
- Brain Repair and Integrative Neuroscience Program, Research Institute of McGill University Health Center, Montréal, Québec H3G1A4, Canada
- Department of Physiology, Biophysics and Neurosciences, Centre for Research and Advanced Studies, Instituto Politecnico Nacional, 07360 Mexico City, Mexico
| | - Zahra S Thirouin
- Brain Repair and Integrative Neuroscience Program, Research Institute of McGill University Health Center, Montréal, Québec H3G1A4, Canada
| | - Joshua C Wyrosdic
- Brain Repair and Integrative Neuroscience Program, Research Institute of McGill University Health Center, Montréal, Québec H3G1A4, Canada
| | - Ubaldo García-Hernández
- Department of Physiology, Biophysics and Neurosciences, Centre for Research and Advanced Studies, Instituto Politecnico Nacional, 07360 Mexico City, Mexico
| | - Charles W Bourque
- Brain Repair and Integrative Neuroscience Program, Research Institute of McGill University Health Center, Montréal, Québec H3G1A4, Canada
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Levi DI, Wyrosdic JC, Hicks AI, Andrade MA, Toney GM, Prager-Khoutorsky M, Bourque CW. High dietary salt amplifies osmoresponsiveness in vasopressin-releasing neurons. Cell Rep 2021; 34:108866. [PMID: 33730577 PMCID: PMC8049100 DOI: 10.1016/j.celrep.2021.108866] [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: 10/07/2019] [Revised: 04/13/2020] [Accepted: 02/24/2021] [Indexed: 12/28/2022] Open
Abstract
High dietary salt increases arterial pressure partly through activation of magnocellular neurosecretory cells (MNCVP) that secrete the antidiuretic and vasoconstrictor hormone vasopressin (VP) into the circulation. Here, we show that the intrinsic and synaptic excitation of MNCVP caused by hypertonicity are differentially potentiated in two models of salt-dependent hypertension in rats. One model combined salty chow with a chronic subpressor dose of angiotensin II (AngII-salt), the other involved replacing drinking water with 2% NaCl (salt loading, SL). In both models, we observed a significant increase in the quantal amplitude of EPSCs on MNCVP. However, model-specific changes were also observed. AngII-salt increased the probability of glutamate release by osmoreceptor afferents and increased overall excitatory network drive. In contrast, SL specifically increased membrane stiffness and the intrinsic osmosensitivity of MNCVP. These results reveal that dietary salt increases the excitability of MNCVP through effects on the cell-autonomous and synaptic osmoresponsiveness of MNCVP.
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Affiliation(s)
- David I Levi
- Brain Repair and Integrative Neuroscience Program, Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G1A4, Canada
| | - Joshua C Wyrosdic
- Brain Repair and Integrative Neuroscience Program, Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G1A4, Canada
| | - Amirah-Iman Hicks
- Department of Physiology, McGill University, 3644 Promenade Sir William Osler, Montreal, QC H3G1Y6, Canada
| | - Mary Ann Andrade
- Department of Cellular and Integrative Physiology, University of Texas Health Sciences Centre San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA
| | - Glenn M Toney
- Department of Cellular and Integrative Physiology, University of Texas Health Sciences Centre San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA
| | - Masha Prager-Khoutorsky
- Department of Physiology, McGill University, 3644 Promenade Sir William Osler, Montreal, QC H3G1Y6, Canada.
| | - Charles W Bourque
- Brain Repair and Integrative Neuroscience Program, Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G1A4, Canada.
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High Salt Intake Recruits Tonic Activation of NR2D Subunit-Containing Extrasynaptic NMDARs in Vasopressin Neurons. J Neurosci 2020; 41:1145-1156. [PMID: 33303677 DOI: 10.1523/jneurosci.1742-20.2020] [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: 07/06/2020] [Revised: 11/19/2020] [Accepted: 11/25/2020] [Indexed: 11/21/2022] Open
Abstract
In addition to producing a classical excitatory postsynaptic current via activation of synaptic NMDA receptors (NMDARs), glutamate in the brain also induces a tonic NMDAR current (I NMDA) via activation of extrasynaptic NMDARs (eNMDARs). However, since Mg2+ blocks NMDARs in nondepolarized neurons, the potential contribution of eNMDARs to the overall neuronal excitatory/inhibitory (E/I) balance remains unknown. Here, we demonstrate that chronic (7 d) salt loading (SL) recruited NR2D subunit-containing NMDARs to generate an Mg2+-resistant tonic I NMDA in nondepolarized [V h (holding potential) -70 mV] vasopressin (VP; but not oxytocin) supraoptic nucleus (SON) neurons in male rodents. Conversely, in euhydrated (EU) and 3 d SL mice, Mg2+-resistant tonic I NMDA was not observed. Pharmacological and genetic intervention of NR2D subunits blocked the Mg2+-resistant tonic I NMDA in VP neurons under SL conditions, while an NR2B antagonist unveiled Mg2+-sensitive tonic I NMDA but not Mg2+-resistant tonic I NMDA In the EU group VP neurons, an Mg2+-resistant tonic I NMDA was not generated by increased ambient glutamate or treatment with coagonists (e.g., d-serine and glycine). Chronic SL significantly increased NR2D expression but not NR2B expression in the SON relative to the EU group or after 3 d under SL conditions. Finally, Mg2+-resistant tonic I NMDA selectively upregulated neuronal excitability in VP neurons under SL conditions, independent of ionotropic GABAergic input. Our results indicate that the activation of NR2D-containing NMDARs constitutes a novel mechanism that generates an Mg2+-resistant tonic I NMDA in nondepolarized VP neurons, thus causing an E/I balance shift in VP neurons to compensate for the hormonal demands imposed by a chronic osmotic challenge.SIGNIFICANCE STATEMENT The hypothalamic supraoptic nucleus (SON) consists of two different types of magnocellular neurosecretory cells (MNCs) that synthesize and release the following two peptide hormones: vasopressin (VP), which is necessary for regulation of fluid homeostasis; and oxytocin (OT), which plays a major role in lactation and parturition. NMDA receptors (NMDARs) play important roles in shaping neuronal firing patterns and hormone release from the SON MNCs in response to various physiological challenges. Our results show that prolonged (7 d) salt loading generated a Mg2+-resistant tonic NMDA current mediated by NR2D subunit-containing receptors, which efficiently activated nondepolarized VP (but not OT) neurons. Our findings support the hypothesis that NR2D subunit-containing NMDARs play an important adaptive role in adult brain in response to a sustained osmotic challenge.
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Cholinergic midbrain afferents modulate striatal circuits and shape encoding of action strategies. Nat Commun 2020; 11:1739. [PMID: 32269213 PMCID: PMC7142106 DOI: 10.1038/s41467-020-15514-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 03/13/2020] [Indexed: 02/06/2023] Open
Abstract
Assimilation of novel strategies into a consolidated action repertoire is a crucial function for behavioral adaptation and cognitive flexibility. Acetylcholine in the striatum plays a pivotal role in such adaptation, and its release has been causally associated with the activity of cholinergic interneurons. Here we show that the midbrain, a previously unknown source of acetylcholine in the striatum, is a major contributor to cholinergic transmission in the striatal complex. Neurons of the pedunculopontine and laterodorsal tegmental nuclei synapse with striatal cholinergic interneurons and give rise to excitatory responses. Furthermore, they produce uniform inhibition of spiny projection neurons. Inhibition of acetylcholine release from midbrain terminals in the striatum impairs the association of contingencies and the formation of habits in an instrumental task, and mimics the effects observed following inhibition of acetylcholine release from striatal cholinergic interneurons. These results suggest the existence of two hierarchically-organized modes of cholinergic transmission in the striatum, where cholinergic interneurons are modulated by cholinergic neurons of the midbrain.
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Abstract
Fluid satiation, or quenching of thirst, is a critical homeostatic signal to stop drinking; however, its underlying neurocircuitry is not well characterized. Cutting-edge genetically encoded tools and techniques are now enabling researchers to pinpoint discrete neuronal populations that control fluid satiation, revealing that hindbrain regions, such as the nucleus of the solitary tract, area postrema, and parabrachial nucleus, primarily inhibit fluid intake. By contrast, forebrain regions such as the lamina terminalis, primarily stimulate thirst and fluid intake. One intriguing aspect of fluid satiation is that thirst is quenched tens of minutes before water reaches the circulation, and the amount of water ingested is accurately calibrated to match physiological needs. This suggests that 'preabsorptive' inputs from the oropharyngeal regions, esophagus or upper gastrointestinal tract anticipate the amount of fluid required to restore fluid homeostasis, and provide rapid signals to terminate drinking once this amount has been consumed. It is likely that preabsorptive signals are carried via the vagal nerve to the hindbrain. In this review, we explore our current understanding of the fluid satiation neurocircuitry, its inputs and outputs, and its interconnections within the brain, with a focus on recent studies of the hindbrain, particularly the parabrachial nucleus.
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Affiliation(s)
- Philip J Ryan
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
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Leng G, Russell JA. The osmoresponsiveness of oxytocin and vasopressin neurones: Mechanisms, allostasis and evolution. J Neuroendocrinol 2019; 31:e12662. [PMID: 30451331 DOI: 10.1111/jne.12662] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 10/29/2018] [Accepted: 11/15/2018] [Indexed: 12/27/2022]
Abstract
In the rat supraoptic nucleus, every oxytocin cell projects to the posterior pituitary, and is involved both in reflex milk ejection during lactation and in regulating uterine contractions during parturition. All are also osmosensitive, regulating natriuresis. All are also regulated by signals that control appetite, including the neural and hormonal signals that arise from the gut after food intake and from the sites of energy storage. All are also involved in sexual behaviour, anxiety-related behaviours and social behaviours. The challenge is to understand how a single population of neurones can coherently regulate such a diverse set of functions and adapt to changing physiological states. Their multiple functions arise from complex intrinsic properties that confer sensitivity to a wide range of internal and environmental signals. Many of these properties have a distant evolutionary origin in multifunctional, multisensory neurones of Urbilateria, the hypothesised common ancestor of vertebrates, insects and worms. Their properties allow different patterns of oxytocin release into the circulation from their axon terminals in the posterior pituitary into other brain areas from axonal projections, as well as independent release from their dendrites.
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Affiliation(s)
- Gareth Leng
- Centre for Discovery Brain Sciences, The University of Edinburgh, Edinburgh, UK
| | - John A Russell
- Centre for Discovery Brain Sciences, The University of Edinburgh, Edinburgh, UK
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8
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Yokoyama T, Terawaki K, Minami K, Miyano K, Nonaka M, Uzu M, Kashiwase Y, Yanagihara K, Ueta Y, Uezono Y. Modulation of synaptic inputs in magnocellular neurones in a rat model of cancer cachexia. J Neuroendocrinol 2018; 30:e12630. [PMID: 29944778 DOI: 10.1111/jne.12630] [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: 04/19/2017] [Accepted: 06/24/2018] [Indexed: 11/29/2022]
Abstract
In cancer cachexia, abnormal metabolism and neuroendocrine dysfunction cause anorexia, tissue damage and atrophy, which can in turn alter body fluid balance. Arginine vasopressin, which regulates fluid homeostasis, is secreted by magnocellular neurosecretory cells (MNCs) of the hypothalamic supraoptic nucleus. Arginine vasopressin secretion by MNCs is regulated by both excitatory and inhibitory synaptic activity, alterations in plasma osmolarity and various peptides, including angiotensin II. In the present study, we used whole-cell patch-clamp recordings of brain slices to determine whether hyperosmotic stimulation and/or angiotensin II potentiate excitatory synaptic input in a rat model of cancer cachexia, similar to their effects in normal (control) rats. Hyperosmotic (15 and 60 mmol L-1 mannitol) stimulation and angiotensin II (0.1 μmol L-1 ) increased the frequency, but not the amplitude, of miniature excitatory postsynaptic currents in normal rats; in model rats, both effects were significantly attenuated. These results suggest that cancer cachexia alters supraoptic MNC sensitivity to osmotic and angiotensin II stimulation.
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Affiliation(s)
- Toru Yokoyama
- Cancer Pathophysiology Division, National Cancer Center Research Institute, Tokyo, Japan
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
- Department of Anesthesiology and Critical Care Medicine, Jichi Medical University, Shimotsuke, Japan
| | - Kiyoshi Terawaki
- Cancer Pathophysiology Division, National Cancer Center Research Institute, Tokyo, Japan
- Tsumura Research Laboratories, Tsumura & Co., Ibaraki, Japan
| | - Kouichiro Minami
- Cancer Pathophysiology Division, National Cancer Center Research Institute, Tokyo, Japan
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
- Department of Anesthesiology and Critical Care Medicine, Jichi Medical University, Shimotsuke, Japan
| | - Kanako Miyano
- Cancer Pathophysiology Division, National Cancer Center Research Institute, Tokyo, Japan
| | - Miki Nonaka
- Cancer Pathophysiology Division, National Cancer Center Research Institute, Tokyo, Japan
| | - Miaki Uzu
- Cancer Pathophysiology Division, National Cancer Center Research Institute, Tokyo, Japan
| | - Yohei Kashiwase
- Cancer Pathophysiology Division, National Cancer Center Research Institute, Tokyo, Japan
- Laboratory of Molecular Pathology and Metabolic Disease, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Noda, Japan
| | - Kazuyoshi Yanagihara
- Division of Biomarker Discovery, Exploratory Oncology Research & Clinical Trial Center, National Cancer Center, Kashiwa, Japan
| | - Yoichi Ueta
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Yasuhito Uezono
- Cancer Pathophysiology Division, National Cancer Center Research Institute, Tokyo, Japan
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Zaelzer C, Gizowski C, Salmon CK, Murai KK, Bourque CW. Detection of activity-dependent vasopressin release from neuronal dendrites and axon terminals using sniffer cells. J Neurophysiol 2018; 120:1386-1396. [PMID: 29975164 DOI: 10.1152/jn.00467.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Our understanding of neuropeptide function within neural networks would be improved by methods allowing dynamic detection of peptide release in living tissue. We examined the usefulness of sniffer cells as biosensors to detect endogenous vasopressin (VP) release in rat hypothalamic slices and from isolated neurohypophyses. Human embryonic kidney cells were transfected to express the human V1a VP receptor (V1aR) and the genetically encoded calcium indicator GCaMP6m. The V1aR couples to Gq11, thus VP binding to this receptor causes an increase in intracellular [Ca2+] that can be detected by a rise in GCaMP6 fluorescence. Dose-response analysis showed that VP sniffer cells report ambient VP levels >10 pM (EC50 = 2.6 nM), and this effect could be inhibited by the V1aR antagonist SR 49059. When placed over a coverslip coated with sniffer cells, electrical stimulation of the neurohypophysis provoked a reversible, reproducible, and dose-dependent increase in VP release using as few as 60 pulses delivered at 3 Hz. Suspended sniffer cells gently plated over a slice adhered to the preparation and allowed visualization of VP release in discrete regions. Electrical stimulation of VP neurons in the suprachiasmatic nucleus caused significant local release as well as VP secretion in distant target sites. Finally, action potentials evoked in a single magnocellular neurosecretory cell in the supraoptic nucleus provoked significant VP release from the somatodendritic compartment of the neuron. These results indicate that sniffer cells can be used for the study of VP secretion from various compartments of neurons in living tissue. NEW & NOTEWORTHY The specific functional roles of neuropeptides in neuronal networks are poorly understood due to the absence of methods allowing their real-time detection in living tissue. Here, we show that cultured "sniffer cells" can be engineered to detect endogenous release of vasopressin as an increase in fluorescence.
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Affiliation(s)
- Cristian Zaelzer
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre , Montréal, Québec , Canada
| | - Claire Gizowski
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre , Montréal, Québec , Canada
| | - Christopher K Salmon
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre , Montréal, Québec , Canada
| | - Keith K Murai
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre , Montréal, Québec , Canada
| | - Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre , Montréal, Québec , Canada
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Flôr AFL, de Brito Alves JL, França-Silva MS, Balarini CM, Elias LLK, Ruginsk SG, Antunes-Rodrigues J, Braga VA, Cruz JC. Glial Cells Are Involved in ANG-II-Induced Vasopressin Release and Sodium Intake in Awake Rats. Front Physiol 2018; 9:430. [PMID: 29765330 PMCID: PMC5938358 DOI: 10.3389/fphys.2018.00430] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 04/06/2018] [Indexed: 01/28/2023] Open
Abstract
It is known that circulating angiotensin II (ANG-II) acts on the circumventricular organs (CVOs), which partially lack a normal blood-brain barrier, to stimulate pressor responses, vasopressin (AVP), and oxytocin (OT) secretion, as well as sodium and water intake. Although ANG-II type 1 receptors (AT1R) are expressed in neurons and astrocytes, the involvement of CVOs glial cells in the neuroendocrine, cardiovascular and behavioral responses induced by central ANG II remains to be further elucidated. To address this question, we performed a set of experiments combining in vitro studies in primary hypothalamic astrocyte cells (HACc) and in vivo intracerebroventricular (icv) microinjections into the lateral ventricle of awake rats. Our results showed that ANG-II decreased glutamate uptake in HACc. In addition, in vivo studies showed that fluorocitrate (FCt), a reversible glial inhibitor, increased OT secretion and mean arterial pressure (MAP) and decreased breathing at rest. Furthermore, previous FCt decreased AVP secretion and sodium intake induced by central ANG-II. Together, our findings support that CVOs glial cells are important in mediating neuroendocrine and cardiorespiratory functions, as well as central ANG-II-induced AVP release and salt-intake behavior in awake rats. In the light of our in vitro studies, we propose that these mechanisms are, at least in part, by ANG-II-induced astrocyte mediate reduction in glutamate extracellular clearance.
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Affiliation(s)
- Atalia F L Flôr
- Departamento de Biotecnologia, Centro de Biotecnologia, Universidade Federal da Paraíba, João Pessoa, Brazil
| | - José L de Brito Alves
- Departamento de Biotecnologia, Centro de Biotecnologia, Universidade Federal da Paraíba, João Pessoa, Brazil
| | - Maria S França-Silva
- Departamento de Biotecnologia, Centro de Biotecnologia, Universidade Federal da Paraíba, João Pessoa, Brazil
| | - Camille M Balarini
- Departamento de Biotecnologia, Centro de Biotecnologia, Universidade Federal da Paraíba, João Pessoa, Brazil.,Departamento de Fisiologia e Patologia, Centro de Ciências da Saúde, Universidade Federal da Paraíba, João Pessoa, Brazil
| | - Lucila L K Elias
- Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Silvia G Ruginsk
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biomédicas, Universidade Federal de Alfenas, Alfenas, Brazil
| | - José Antunes-Rodrigues
- Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Valdir A Braga
- Departamento de Biotecnologia, Centro de Biotecnologia, Universidade Federal da Paraíba, João Pessoa, Brazil
| | - Josiane C Cruz
- Departamento de Biotecnologia, Centro de Biotecnologia, Universidade Federal da Paraíba, João Pessoa, Brazil
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de Morais SDB, Shanks J, Zucker IH. Integrative Physiological Aspects of Brain RAS in Hypertension. Curr Hypertens Rep 2018; 20:10. [PMID: 29480460 DOI: 10.1007/s11906-018-0810-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
PURPOSE OF REVIEW The renin-angiotensin system (RAS) plays an important role in modulating cardiovascular function and fluid homeostasis. While the systemic actions of the RAS are widely accepted, the role of the RAS in the brain, its regulation of cardiovascular function, and sympathetic outflow remain controversial. In this report, we discuss the current understanding of central RAS on blood pressure (BP) regulation, in light of recent literature and new experimental techniques. RECENT FINDINGS Studies using neuronal or glial-specifc mouse models have allowed for greater understanding into the site-specific expression and role centrally expressed RAS proteins have on BP regulation. While all components of the RAS have been identified in cardiovascular regulatory regions of the brain, their actions may be site specific. In a number of animal models of hypertension, reduction in Ang II-mediated signaling, or upregulation of the central ACE2/Ang 1-7 pathway, has been shown to reduce BP, via a reduction in sympathetic signaling and increase parasympathetic tone, respectively. Emerging evidence also suggests that, in part, the female protective phenotype against hypertension may be due to inceased ACE2 activity within cardiovascular regulatory regions of the brain, potentially mediated by estrogen. Increasing evidence suggests the importance of a central renin-angiotensin pathway, although its localization and the mechanisms involved in its expression and regulation still need to be clarified and more precisely defined. All reported studies/experiments with human or animal subjects performed by the authors have been previously published and complied with all applicable ethical standards (including the Helsinki declaration and its amendments, institutional/national research committee standards, and international/national/institutional guidelines).
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Affiliation(s)
- Sharon D B de Morais
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, 68198-5850, USA
| | - Julia Shanks
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, 68198-5850, USA
| | - Irving H Zucker
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, 68198-5850, USA.
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Abstract
PURPOSE OF REVIEW The central nervous system plays a pivotal role in the regulation of extracellular fluid volume and consequently arterial blood pressure. Key hypothalamic regions sense and integrate neurohumoral signals to subsequently alter intake (thirst and salt appetite) and output (renal excretion via neuroendocrine and autonomic function). Here, we review recent findings that provide new insight into such mechanisms that may represent new therapeutic targets. RECENT FINDINGS Implementation of cutting edge neuroscience approaches such as opto- and chemogenetics highlight pivotal roles of circumventricular organs to impact body fluid homeostasis. Key signaling mechanisms within these areas include the N-terminal variant of transient receptor potential vannilloid type-1, NaX, epithelial sodium channel, brain electroneutral transporters, and non-classical actions of vasopressin. Despite the identification of several new mechanisms, future studies need to better define the neurochemical phenotype and molecular profiles of neurons within circumventricular organs for future therapeutic potential.
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13
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Gizowski C, Trudel E, Bourque CW. Central and peripheral roles of vasopressin in the circadian defense of body hydration. Best Pract Res Clin Endocrinol Metab 2017; 31:535-546. [PMID: 29224666 DOI: 10.1016/j.beem.2017.11.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Vasopressin is a neuropeptide synthesized by specific subsets of neurons within the eye and brain. Studies in rats and mice have shown that vasopressin produced by magnocellular neurosecretory cells (MNCs) that project to the neurohypophysis is released into the blood circulation where it serves as an antidiuretic hormone to promote water reabsorption from the kidney. Moreover vasopressin is a neurotransmitter and neuromodulator that contributes to time-keeping within the master circadian clock (i.e. the suprachiasmatic nucleus, SCN) and is also used as an output signal by SCN neurons to direct centrally mediated circadian rhythms. In this chapter, we review recent cellular and network level studies in rodents that have provided insight into how circadian rhythms in vasopressin mediate changes in water intake behavior and renal water conservation that protect the body against dehydration during sleep.
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Affiliation(s)
- Claire Gizowski
- Center for Research in Neuroscience, Research Institute of the McGill University Health Center, 1650 Cedar Avenue, Montreal, QC, H3G1A4, Canada.
| | - Eric Trudel
- Center for Research in Neuroscience, Research Institute of the McGill University Health Center, 1650 Cedar Avenue, Montreal, QC, H3G1A4, Canada.
| | - Charles W Bourque
- Center for Research in Neuroscience, Research Institute of the McGill University Health Center, 1650 Cedar Avenue, Montreal, QC, H3G1A4, Canada.
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14
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Ryan PJ, Ross SI, Campos CA, Derkach VA, Palmiter RD. Oxytocin-receptor-expressing neurons in the parabrachial nucleus regulate fluid intake. Nat Neurosci 2017; 20:1722-1733. [PMID: 29184212 PMCID: PMC5705772 DOI: 10.1038/s41593-017-0014-z] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 09/17/2017] [Indexed: 02/08/2023]
Abstract
Brain regions that regulate fluid satiation are not well characterized, yet are essential for understanding fluid homeostasis. We found that oxytocin-receptor-expressing neurons in the parabrachial nucleus of mice (OxtrPBN neurons) are key regulators of fluid satiation. Chemogenetic activation of OxtrPBN neurons robustly suppressed noncaloric fluid intake, but did not decrease food intake after fasting or salt intake following salt depletion; inactivation increased saline intake after dehydration and hypertonic saline injection. Under physiological conditions, OxtrPBN neurons were activated by fluid satiation and hypertonic saline injection. OxtrPBN neurons were directly innervated by oxytocin neurons in the paraventricular hypothalamus (OxtPVH neurons), which mildly attenuated fluid intake. Activation of neurons in the nucleus of the solitary tract substantially suppressed fluid intake and activated OxtrPBN neurons. Our results suggest that OxtrPBN neurons act as a key node in the fluid satiation neurocircuitry, which acts to decrease water and/or saline intake to prevent or attenuate hypervolemia and hypernatremia. The authors show that oxytocin-receptor-expressing neurons in the parabrachial nucleus are key regulators of fluid homeostasis that suppress fluid intake when activated, but do not decrease food intake after fasting or salt intake after salt depletion.
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Affiliation(s)
- Philip J Ryan
- Howard Hughes Medical Institute, University of Washington, Seattle, Washington, USA. .,Department of Biochemistry, University of Washington, Seattle, Washington, USA. .,The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia.
| | - Silvano I Ross
- Howard Hughes Medical Institute, University of Washington, Seattle, Washington, USA.,Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Carlos A Campos
- Howard Hughes Medical Institute, University of Washington, Seattle, Washington, USA.,Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Victor A Derkach
- Howard Hughes Medical Institute, University of Washington, Seattle, Washington, USA.,Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Richard D Palmiter
- Howard Hughes Medical Institute, University of Washington, Seattle, Washington, USA. .,Department of Biochemistry, University of Washington, Seattle, Washington, USA.
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15
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Wang X, Liu Y, Li X, Zhang Z, Yang H, Zhang Y, Williams PR, Alwahab NSA, Kapur K, Yu B, Zhang Y, Chen M, Ding H, Gerfen CR, Wang KH, He Z. Deconstruction of Corticospinal Circuits for Goal-Directed Motor Skills. Cell 2017; 171:440-455.e14. [PMID: 28942925 PMCID: PMC5679421 DOI: 10.1016/j.cell.2017.08.014] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2016] [Revised: 04/19/2017] [Accepted: 08/09/2017] [Indexed: 12/26/2022]
Abstract
Corticospinal neurons (CSNs) represent the direct cortical outputs to the spinal cord and play important roles in motor control across different species. However, their organizational principle remains unclear. By using a retrograde labeling system, we defined the requirement of CSNs in the execution of a skilled forelimb food-pellet retrieval task in mice. In vivo imaging of CSN activity during performance revealed the sequential activation of topographically ordered functional ensembles with moderate local mixing. Region-specific manipulations indicate that CSNs from caudal or rostral forelimb area control reaching or grasping, respectively, and both are required in the transitional pronation step. These region-specific CSNs terminate in different spinal levels and locations, therefore preferentially connecting with the premotor neurons of muscles engaged in different steps of the task. Together, our findings suggest that spatially defined groups of CSNs encode different movement modules, providing a logic for parallel-ordered corticospinal circuits to orchestrate multistep motor skills.
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Affiliation(s)
- Xuhua Wang
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Yuanyuan Liu
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Xinjian Li
- Unit on Neural Circuits and Adaptive Behaviors, Clinical and Translational Neuroscience Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Zicong Zhang
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Hengfu Yang
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Yu Zhang
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Philip R Williams
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Noaf S A Alwahab
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Kush Kapur
- Clinical Research Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Bin Yu
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Yiming Zhang
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Mengying Chen
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Haixia Ding
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Charles R Gerfen
- Laboratory of Systems Neuroscience, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kuan Hong Wang
- Unit on Neural Circuits and Adaptive Behaviors, Clinical and Translational Neuroscience Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Zhigang He
- F.M. Kirby Neurobiology Center, Boston Children's Hospital and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
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16
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Abstract
Osmosensory neurons are specialized cells activated by increases in blood osmolality to trigger thirst, secretion of the antidiuretic hormone vasopressin, and elevated sympathetic tone during dehydration. In addition to multiple extrinsic factors modulating their activity, osmosensory neurons are intrinsically osmosensitive, as they are activated by increased osmolality in the absence of neighboring cells or synaptic contacts. This intrinsic osmosensitivity is a mechanical process associated with osmolality-induced changes in cell volume. This review summarises recent findings revealing molecular mechanisms underlying the mechanical activation of osmosensory neurons and highlighting important roles of microtubules, actin, and mechanosensitive ion channels in this process.
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17
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Choe KY, Trudel E, Bourque CW. Effects of Salt Loading on the Regulation of Rat Hypothalamic Magnocellular Neurosecretory Cells by Ionotropic GABA and Glycine Receptors. J Neuroendocrinol 2016; 28. [PMID: 26833894 DOI: 10.1111/jne.12372] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 01/12/2016] [Accepted: 01/23/2016] [Indexed: 12/18/2022]
Abstract
Synaptic and extrasynaptic transmission mediated by ionotropic GABA and glycine receptors plays a critical role in shaping the action potential firing (spiking) activity of hypothalamic magnocellular neurosecretory cells and therefore determines the rate at which vasopressin and oxytocin are released from the neurohypophysis. The inhibitory effect of these transmitters relies on the maintenance of a low concentration of intracellular chloride ions such that, when activated by GABA or glycine, a hyperpolarisation of the neuronal membrane potential results. In this review, we highlight the various ways by which the two types of inhibitory receptors contribute to homeostasis by fine-tuning the spiking rate of vasopressin-releasing magnocellular neurosecretory cells in a manner dependent on the hydration state of the animal. In addition, we review the currently available evidence on how the strength of these inhibitory pathways can be regulated during chronic hypernatraemia via a form of activity-dependent depolarisation of the chloride reversal potential, leading to an abolition of these inhibitory pathways potentially causing sodium-dependent elevations in blood pressure.
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Affiliation(s)
- K Y Choe
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal, Canada
| | - E Trudel
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal, Canada
| | - C W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal, Canada
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18
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Sladek CD, Michelini LC, Stachenfeld NS, Stern JE, Urban JH. Endocrine‐Autonomic Linkages. Compr Physiol 2015; 5:1281-323. [DOI: 10.1002/cphy.c140028] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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19
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Prager-Khoutorsky M, Bourque CW. Mechanical basis of osmosensory transduction in magnocellular neurosecretory neurones of the rat supraoptic nucleus. J Neuroendocrinol 2015; 27:507-15. [PMID: 25712904 DOI: 10.1111/jne.12270] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 02/19/2015] [Accepted: 02/22/2015] [Indexed: 12/31/2022]
Abstract
Rat magnocellular neurosecretory cells (MNCs) release vasopressin and oxytocin to promote antidiuresis and natriuresis at the kidney. The osmotic control of oxytocin and vasopressin release at the neurohypophysis is required for osmoregulation in these animals, and this release is mediated by a modulation of the action potential firing rate by the MNCs. Under basal (isotonic) conditions, MNCs fire action potentials at a slow rate, and this activity is inhibited by hypo-osmotic conditions and enhanced by hypertonicity. The effects of changes in osmolality on MNCs are mediated by a number of different factors, including the involvement of synaptic inputs, the release of taurine by local glial cells and regulation of ion channels expressed within the neurosecretory neurones themselves. We review recent findings that have clarified our understanding of how osmotic stimuli modulate the activity of nonselective cation channels in MNCs. Previous studies have shown that osmotically-evoked changes in membrane potential and action potential firing rate in acutely isolated MNCs are provoked mainly by a modulation of nonselective cation channels. Notably, the excitation of isolated MNCs during hypertonicity is mediated by the activation of a capsaicin-insensitive cation channel that MNCs express as an N-terminal variant of the transient receptor potential vanilloid 1 (Trpv1) channel. The activation of this channel during hypertonicity is a mechanical process associated with cell shrinking. The effectiveness of this mechanical process depends on the presence of a thin layer of actin filaments (F-actin) beneath the plasma membrane, as well as a densely interweaved network of microtubules (MTs) occupying the bulk of the cytoplasm of MNCs. Although the mechanism by which F-actin contributes to Trpv1 activation remains unknown, recent data have shown that MTs interact with Trpv1 channels via binding sites on the C-terminus, and that the force mediated through this complex is required for channel gating during osmosensory transduction. Indeed, displacement of this interaction prevents channel activation during shrinking, whereas increasing the density of these interaction sites potentiates shrinking-induced activation of Trpv1. Therefore, the gain of the osmosensory transduction process can be regulated bi-directionally through changes in the organisation of F-actin and MTs.
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Affiliation(s)
- M Prager-Khoutorsky
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - C W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
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20
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Smith JA, Pati D, Wang L, de Kloet AD, Frazier CJ, Krause EG. Hydration and beyond: neuropeptides as mediators of hydromineral balance, anxiety and stress-responsiveness. Front Syst Neurosci 2015; 9:46. [PMID: 25873866 PMCID: PMC4379895 DOI: 10.3389/fnsys.2015.00046] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 03/06/2015] [Indexed: 11/13/2022] Open
Abstract
Challenges to body fluid homeostasis can have a profound impact on hypothalamic regulation of stress responsiveness. Deficiencies in blood volume or sodium concentration leads to the generation of neural and humoral signals relayed through the hindbrain and circumventricular organs that apprise the paraventricular nucleus of the hypothalamus (PVH) of hydromineral imbalance. Collectively, these neural and humoral signals converge onto PVH neurons, including those that express corticotrophin-releasing factor (CRF), oxytocin (OT), and vasopressin, to influence their activity and initiate compensatory responses that alleviate hydromineral imbalance. Interestingly, following exposure to perceived threats to homeostasis, select limbic brain regions mediate behavioral and physiological responses to psychogenic stressors, in part, by influencing activation of the same PVH neurons that are known to maintain body fluid homeostasis. Here, we review past and present research examining interactions between hypothalamic circuits regulating body fluid homeostasis and those mediating behavioral and physiological responses to psychogenic stress.
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Affiliation(s)
- Justin A. Smith
- Laboratory of Dr. Eric Krause, Department of Pharmacodynamics, College of Pharmacy, University of FloridaGainesville, FL, USA
| | - Dipanwita Pati
- Laboratory of Dr. Charles Frazier, Department of Pharmacodynamics, College of Pharmacy, University of FloridaGainesville, FL, USA
| | - Lei Wang
- Laboratory of Dr. Eric Krause, Department of Pharmacodynamics, College of Pharmacy, University of FloridaGainesville, FL, USA
| | - Annette D. de Kloet
- Laboratory of Dr. Colin Sumners, Department of Physiology and Functional Genomics, College of Medicine, University of FloridaGainesville, FL, USA
| | - Charles J. Frazier
- Laboratory of Dr. Charles Frazier, Department of Pharmacodynamics, College of Pharmacy, University of FloridaGainesville, FL, USA
| | - Eric G. Krause
- Laboratory of Dr. Eric Krause, Department of Pharmacodynamics, College of Pharmacy, University of FloridaGainesville, FL, USA
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21
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Opposite effects of oxytocin on water intake induced by hypertonic NaCl or polyethylene glycol administration. Physiol Behav 2015; 141:135-42. [PMID: 25617595 DOI: 10.1016/j.physbeh.2015.01.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 12/20/2014] [Accepted: 01/20/2015] [Indexed: 11/21/2022]
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