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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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2
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Zhang L, Liu N, Shao J, Gao D, Liu Y, Zhao Y, Han C, Chen D, Wang L, Lu WW, Yang F. Bidirectional control of parathyroid hormone and bone mass by subfornical organ. Neuron 2023; 111:1914-1932.e6. [PMID: 37084721 DOI: 10.1016/j.neuron.2023.03.030] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 11/02/2022] [Accepted: 03/23/2023] [Indexed: 04/23/2023]
Abstract
Parathyroid hormone (PTH) is one of the most important hormones for bone turnover and calcium homeostasis. It is unclear how the central nervous system regulates PTH. The subfornical organ (SFO) lies above the third ventricle and modulates body fluid homeostasis. Through retrograde tracing, electrophysiology, and in vivo calcium imaging, we identified the SFO as an important brain nucleus that responds to serum PTH changes in mice. Chemogenetic stimulation of GABAergic neurons in SFO induces decreased serum PTH followed by a decrease in trabecular bone mass. Conversely, stimulation of glutamatergic neurons in the SFO promoted serum PTH and bone mass. Moreover, we found that the blockage of different PTH receptors in the SFO affects peripheral PTH levels and the PTH's response to calcium stimulation. Furthermore, we identified a GABAergic projection from the SFO to the paraventricular nucleus, which modulates PTH and bone mass. These findings advance our understanding of the central neural regulation of PTH at cellular and circuit level.
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Affiliation(s)
- Lu Zhang
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China; Department of Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong SAR, China
| | - Nian Liu
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China; Department of Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong SAR, China; Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Jie Shao
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Dashuang Gao
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Yunhui Liu
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Yingzi Zhao
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Chuanliang Han
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Di Chen
- Faculty of Pharmaceutical Sciences, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Liping Wang
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China; The Guangdong Provincial Key Laboratory of Brain Connectome and Behavior, Shenzhen, Guangdong, China; CAS Key Laboratory of Brain Connectome and Manipulation, Shenzhen, Guangdong, China; Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, Guangdong, China
| | - William Weijia Lu
- Department of Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong SAR, China; Faculty of Pharmaceutical Sciences, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China.
| | - Fan Yang
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China; The Guangdong Provincial Key Laboratory of Brain Connectome and Behavior, Shenzhen, Guangdong, China; CAS Key Laboratory of Brain Connectome and Manipulation, Shenzhen, Guangdong, China; Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, Guangdong, China.
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3
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Sudbury JR, Zaelzer C, Trudel E, Bumagin A, Bourque CW. Synaptic control of rat magnocellular neurosecretory cells by warm-sensing neurons in the organum vasculosum lamina terminalis. J Neuroendocrinol 2022; 34:e13214. [PMID: 36426844 DOI: 10.1111/jne.13214] [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: 04/22/2022] [Revised: 10/07/2022] [Accepted: 10/27/2022] [Indexed: 11/11/2022]
Abstract
Increases in core body temperature cause secretion of vasopressin (vasopressin, antidiuretic hormone) to promote water reabsorption and blunt water losses incurred through homeostatic evaporative cooling. Subtypes of transient receptor potential vanilloid (Trpv) channels have been shown to contribute to the intrinsic regulation of vasopressin-releasing magnocellular neurosecretory cells (MNCs) in the supraoptic nucleus (SON) and paraventricular nucleus (PVN). However, MNCs in vivo can also be excited by local heating of the adjacent preoptic area, indicating they receive thermosensory information from other areas. Here, we investigated whether neurons in the organum vasculosum lamina terminalis (OVLT) contribute to this process using in vitro electrophysiological approaches in male rats. We found that the majority of OVLT neurons are thermosensitive in the physiological range (36-39°C) and that this property is retained under conditions blocking synaptic transmission. A subset of these neurons could be antidromically activated by electrical stimulation in the SON. Whole cell recordings from SON MNCs revealed that heating significantly increases the rate of spontaneous excitatory postsynaptic currents (sEPCSs), and that this response is abolished by lesions targeting the OVLT, but not by bilateral lesions placed in the adjacent preoptic area. Finally, local heating of the OVLT caused a significant excitation of MNCs in the absence of temperature changes in the SON, and this effect was blocked by inhibitors of ionotropic glutamate receptors. These findings indicate that the OVLT serves as an important thermosensory nucleus and contributes to the activation of MNCs during physiological heating.
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Affiliation(s)
- Jessica R Sudbury
- Brain Repair and Integrative Neuroscience Program, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - Cristian Zaelzer
- Brain Repair and Integrative Neuroscience Program, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - Eric Trudel
- Brain Repair and Integrative Neuroscience Program, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - Anna Bumagin
- Brain Repair and Integrative Neuroscience Program, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - Charles W Bourque
- Brain Repair and Integrative Neuroscience Program, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
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4
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Zhang F, Mak SOK, Liu Y, Ke Y, Rao F, Yung WH, Zhang L, Chow BKC. Secretin receptor deletion in the subfornical organ attenuates the activation of excitatory neurons under dehydration. Curr Biol 2022; 32:4832-4841.e5. [PMID: 36220076 DOI: 10.1016/j.cub.2022.09.037] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 07/22/2022] [Accepted: 09/19/2022] [Indexed: 11/06/2022]
Abstract
In mammals, thirst is strongly influenced by the subfornical organ (SFO), a forebrain structure that integrates circulating signals including osmotic pressure and sodium contents. Secretin (SCT), a classical gastrointestinal hormone, has been implicated as a humoral factor regulating body-fluid homeostasis. However, the neural mechanism of secretin in the central nervous system in managing thirst remains unclear. In this study, we report that the local ablation of SCT receptor (SCTR) in the SFO reduces water but not salt intake in dehydrated mice and this effect could not be rescued by exogenous SCT administration. Electrophysiology with single-cell RT-PCR indicates that SCT elicits inward currents in the SFO neuronal nitric oxide synthase (SFOnNOS) neurons via SCTR in the presence of glutamate receptor antagonists. We further show that the SCTR in the SFO permits the activation of SFOnNOS neurons under distinct thirst types. Projection-specific gene deletion of SCTR in SFO to the median preoptic nucleus (MnPO) pathway also reduces water intake in dehydrated animals. SCT signaling thus plays an indispensable role in driving thirst. These data not only expand the functional boundaries of SCTR but also provide insights into the central mechanisms of homeostatic regulation.
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Affiliation(s)
- Fengwei Zhang
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Sarah O K Mak
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Yuchu Liu
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Ya Ke
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong, China; Gerald Choa Neuroscience Centre, The Chinese University of Hong Kong, Hong Kong, China
| | - Feng Rao
- School of Life Sciences, Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Wing Ho Yung
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong, China; Gerald Choa Neuroscience Centre, The Chinese University of Hong Kong, Hong Kong, China.
| | - Li Zhang
- Key Laboratory of CNS Regeneration (Ministry of Education), GHM Institute of CNS Regeneration, Jinan University, Guangzhou, China; Neuroscience and Neurorehabilitation Institute, University of Health and Rehabilitation Sciences, Qingdao, China.
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5
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Porcari CY, Cambiasso MJ, Mecawi AS, Caeiro XE, Antunes-Rodrigues J, Vivas LM, Godino A. Molecular neurobiological markers in the onset of sodium appetite. Sci Rep 2022; 12:14224. [PMID: 35987984 PMCID: PMC9392805 DOI: 10.1038/s41598-022-18220-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 08/08/2022] [Indexed: 12/02/2022] Open
Abstract
Sodium appetite is a motivational state involving homeostatic behavior, seeking the ingest of salty substances after sodium loss. There is a temporal dissociation between sodium depletion (SD) and the appearance of sodium appetite. However, the responsible mechanisms for this delay remain poorly elucidated. In the present study, we measured the temporal changes at two and 24 h after SD in the gene expression of key elements within excitatory, inhibitory, and sensory areas implicated in the signaling pathways involved in the onset of sodium appetite. In SD rats, we observed that the expression of critical components within the brain control circuit of sodium appetite, including Angiotensin-type-1 receptor (Agtr1a), Oxytocin-(OXT-NP)-neurophysin-I, and serotonergic-(5HT)-type-2c receptor (Htr2c) were modulated by SD, regardless of time. However, we observed reduced phosphorylation of mitogen-activated protein kinases (MAPK) at the paraventricular nucleus (PVN) and increased oxytocin receptor (Oxtr) mRNA expression at the anteroventral of the third ventricle area (AV3V), at two hours after SD, when sodium appetite is inapparent. At twenty-four hours after SD, when sodium appetite is released, we observed a reduction in the mRNA expression of the transient receptor potential channel 1gene (Trpv1) and Oxtr in the AV3V and the dorsal raphe nucleus, respectively. The results indicate that SD exerts a coordinated timing effect, promoting the appearance of sodium appetite through changes in MAPK activity and lower Trpv1 channel and Oxtr expression that trigger sodium consumption to reestablish the hydroelectrolytic homeostasis.
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Affiliation(s)
- Cintia Y Porcari
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC-CONICET-Universidad Nacional de Córdoba), Friuli 2434, Barrio Parque Vélez Sarsfield, Casilla de Correo, 389-5000, 5016, Córdoba, Provincia de Córdoba, Argentina
| | - María J Cambiasso
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC-CONICET-Universidad Nacional de Córdoba), Friuli 2434, Barrio Parque Vélez Sarsfield, Casilla de Correo, 389-5000, 5016, Córdoba, Provincia de Córdoba, Argentina
- Departamento de Biología Bucal, Facultad de Odontología, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - André S Mecawi
- Laboratory of Molecular Neuroendocrinology, Department of Biophysics, Paulista Medical School, Federal University of São Paulo, São Paulo, Brazil
| | - Ximena E Caeiro
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC-CONICET-Universidad Nacional de Córdoba), Friuli 2434, Barrio Parque Vélez Sarsfield, Casilla de Correo, 389-5000, 5016, Córdoba, Provincia de Córdoba, Argentina
| | - José Antunes-Rodrigues
- Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Sao Paulo, Brazil
| | - Laura M Vivas
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC-CONICET-Universidad Nacional de Córdoba), Friuli 2434, Barrio Parque Vélez Sarsfield, Casilla de Correo, 389-5000, 5016, Córdoba, Provincia de Córdoba, Argentina
- Facultad de Ciencias Exactas Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Andrea Godino
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC-CONICET-Universidad Nacional de Córdoba), Friuli 2434, Barrio Parque Vélez Sarsfield, Casilla de Correo, 389-5000, 5016, Córdoba, Provincia de Córdoba, Argentina.
- Facultad de Psicología, Universidad Nacional de Córdoba, Córdoba, Argentina.
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6
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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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7
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Kollmann P, Elfers K, Maurer S, Klingenspor M, Schemann M, Mazzuoli-Weber G. Submucosal enteric neurons of the cavine distal colon are sensitive to hypoosmolar stimuli. J Physiol 2020; 598:5317-5332. [PMID: 32880976 DOI: 10.1113/jp280309] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 08/24/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Neurons of the enteric submucous plexus are challenged by osmolar fluctuations during digestion and absorption of nutrients. Central neurons are very sensitive to changes in osmolality but knowledge on that issue related to enteric neurons is sparse. The present study focuses on investigation of osmosensitivity of submucosal neurons including potential molecular mediating mechanisms. Results show that submucosal neurons respond to hypoosmolar stimuli with increased activity which is partially mediated by the transient receptor potential vanilloid 4 channel. We provided important information on osmosensitive properties of enteric neurons. These data are fundamental to better explain the nerve-mediated control of the gastrointestinal functions during physiological and pathophysiological (diarrhoea) conditions. ABSTRACT Enteric neurons are located inside the gut wall, where they are confronted with changes in osmolality during (inter-) digestive periods. In particular, neurons of the submucous plexus (SMP), located between epithelial cells and blood vessels may sense and respond to osmotic shifts. The present study was conducted to investigate osmosensitivity of enteric submucosal neurons and the potential role of the transient receptor potential vanilloid 4 channel (TRPV4) as a mediator of enteric neuronal osmosensitivity. Therefore, freshly dissected submucosal preparations from guinea pig colon were investigated for osmosensitivity using voltage-sensitive dye and Ca2+ imaging. Acute hypoosmolar stimuli (final osmolality reached at ganglia of 94, 144 and 194 mOsm kg-1 ) were applied to single ganglia using a local perfusion system. Expression of TRPV4 in the SMP was quantified using qRT-PCR, and GSK1016790A and HC-067047 were used to activate or block the receptor, respectively, revealing its relevance in enteric osmosensitivity. On average, 11.0 [7.0/17.0] % of submucosal neurons per ganglion responded to the hypoosmolar stimulus. The Ca2+ imaging experiments showed that glia responded to the hypoosmolar stimulus, but with a delay in comparison with neurons. mRNA expression of TRPV4 could be shown in the SMP and blockade of the receptor by HC-067047 significantly decreased the number of responding neurons (0.0 [0.0/6.3] %) while the TRPV4 agonist GSK1016790A caused action potential discharge in a subpopulation of osmosensitive enteric neurons. The results of the present study provide insight into the osmosensitivity of submucosal enteric neurons and strongly indicate the involvement of TRPV4 as an osmotransducer.
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Affiliation(s)
- Patrick Kollmann
- Chair of Human Biology, Technical University of Munich, Freising, Germany
| | - Kristin Elfers
- Institute for Physiology and Cell Biology, University of Veterinary Medicine, Foundation, Hannover, Germany
| | - Stefanie Maurer
- Chair of Molecular Nutritional Medicine, Else Kröner-Fresenius Center for Nutritional Medicine & ZIEL Institute for Food & Health, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Martin Klingenspor
- Chair of Molecular Nutritional Medicine, Else Kröner-Fresenius Center for Nutritional Medicine & ZIEL Institute for Food & Health, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Michael Schemann
- Chair of Human Biology, Technical University of Munich, Freising, Germany
| | - Gemma Mazzuoli-Weber
- Institute for Physiology and Cell Biology, University of Veterinary Medicine, Foundation, Hannover, Germany
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8
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Ueno H, Sanada K, Miyamoto T, Baba K, Tanaka K, Nishimura H, Nishimura K, Sonoda S, Yoshimura M, Maruyama T, Oginosawa Y, Araki M, Sonoda S, Onaka T, Otsuji Y, Ueta Y. Oxytocin-monomeric red fluorescent protein 1 synthesis in the hypothalamus under osmotic challenge and acute hypovolemia in a transgenic rat line. Physiol Rep 2020; 8:e14558. [PMID: 32914562 PMCID: PMC7507703 DOI: 10.14814/phy2.14558] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 07/18/2020] [Accepted: 07/20/2020] [Indexed: 12/29/2022] Open
Abstract
We generated a transgenic rat line that expresses oxytocin (OXT)-monomeric red fluorescent protein 1 (mRFP1) fusion gene to visualize the dynamics of OXT. In this transgenic rat line, hypothalamic OXT can be assessed under diverse physiological and pathophysiological conditions by semiquantitative fluorometry of mRFP1 fluorescence intensity as a surrogate marker for endogenous OXT. Using this transgenic rat line, we identified the changes in hypothalamic OXT synthesis under various physiological conditions. However, few reports have directly examined hypothalamic OXT synthesis under hyperosmolality or hypovolemia. In this study, hypothalamic OXT synthesis was investigated using the transgenic rat line after acute osmotic challenge and acute hypovolemia induced by intraperitoneal (i.p.) administration of 3% hypertonic saline (HTN) and polyethylene glycol (PEG), respectively. The mRFP1 fluorescence intensity in the paraventricular (PVN) and supraoptic nuclei (SON) was significantly increased after i.p. administration of HTN and PEG, along with robust Fos-like immunoreactivity (co-expression). Fos expression showed neuronal activation in the brain regions that are associated with the hypothalamus and/or are involved in maintaining water and electrolyte homeostasis in HTN- and PEG-treated rats. OXT and mRFP1 gene expressions were dramatically increased after HTN and PEG administration. The plasma OXT level was extremely increased after HTN and PEG administration. Acute osmotic challenge and acute hypovolemia induced upregulation of hypothalamic OXT in the PVN and SON. These results suggest that not only endogenous arginine vasopressin (AVP) but also endogenous OXT has a key role in maintaining body fluid homeostasis to cope with hyperosmolality and hypovolemia.
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Affiliation(s)
- Hiromichi Ueno
- Department of the Second Department of Internal MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
- PhysiologySchool of MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Kenya Sanada
- Department of the Second Department of Internal MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
- PhysiologySchool of MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Tetsu Miyamoto
- Department of the Second Department of Internal MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Kazuhiko Baba
- PhysiologySchool of MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Kentaro Tanaka
- PhysiologySchool of MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Haruki Nishimura
- PhysiologySchool of MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Kazuaki Nishimura
- PhysiologySchool of MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Satomi Sonoda
- PhysiologySchool of MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Mitsuhiro Yoshimura
- PhysiologySchool of MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Takashi Maruyama
- PhysiologySchool of MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Yasushi Oginosawa
- Department of the Second Department of Internal MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Masaru Araki
- Department of the Second Department of Internal MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Shinjo Sonoda
- Department of the Second Department of Internal MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Tatsushi Onaka
- Division of Brain and NeurophysiologyDepartment of PhysiologyJichi Medical UniversityShimotsukeJapan
| | - Yutaka Otsuji
- Department of the Second Department of Internal MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
| | - Yoichi Ueta
- PhysiologySchool of MedicineUniversity of Occupational and Environmental HealthKitakyushuJapan
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9
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Ciura S, Prager-Khoutorsky M, Thirouin ZS, Wyrosdic JC, Olson JE, Liedtke W, Bourque CW. Trpv4 Mediates Hypotonic Inhibition of Central Osmosensory Neurons via Taurine Gliotransmission. Cell Rep 2019; 23:2245-2253. [PMID: 29791836 DOI: 10.1016/j.celrep.2018.04.090] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Revised: 01/15/2018] [Accepted: 04/19/2018] [Indexed: 12/21/2022] Open
Abstract
The maintenance of hydromineral homeostasis requires bidirectional detection of changes in extracellular fluid osmolality by primary osmosensory neurons (ONs) in the organum vasculosum laminae terminalis (OVLT). Hypertonicity excites ONs in part through the mechanical activation of a variant transient receptor potential vanilloid-1 channel (dn-Trpv1). However, the mechanism by which local hypotonicity inhibits ONs in the OVLT remains unknown. Here, we show that hypotonicity can reduce the basal activity of dn-Trpv1 channels and hyperpolarize acutely isolated ONs. Surprisingly, we found that mice lacking dn-Trpv1 maintain normal inhibitory responses to hypotonicity when tested in situ. In the intact setting, hypotonicity inhibits ONs through a non-cell-autonomous mechanism that involves glial release of the glycine receptor agonist taurine through hypotonicity activated anion channels (HAAC) that are activated subsequent to Ca2+ influx through Trpv4 channels. Our study clarifies how Trpv4 channels contribute to the inhibition of OVLT ONs during hypotonicity in situ.
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Affiliation(s)
- Sorana Ciura
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, 1650 Cedar Avenue, Montreal, QC H3G1A4, Canada.
| | - Masha Prager-Khoutorsky
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, 1650 Cedar Avenue, Montreal, QC H3G1A4, Canada
| | - Zahra S Thirouin
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, 1650 Cedar Avenue, Montreal, QC H3G1A4, Canada
| | - Joshua C Wyrosdic
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, 1650 Cedar Avenue, Montreal, QC H3G1A4, Canada
| | - James E Olson
- Department of Emergency Medicine/Department of Neuroscience, Cell Biology and Physiology, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA
| | - Wolfgang Liedtke
- Centre for Translational Neuroscience, 201G Bryan Research Bldg. Box 2900, Duke University Medical Centre, Durham, NC 27710, USA
| | - Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, 1650 Cedar Avenue, Montreal, QC H3G1A4, Canada.
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McKinley MJ, Denton DA, Ryan PJ, Yao ST, Stefanidis A, Oldfield BJ. From sensory circumventricular organs to cerebral cortex: Neural pathways controlling thirst and hunger. J Neuroendocrinol 2019; 31:e12689. [PMID: 30672620 DOI: 10.1111/jne.12689] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 01/20/2019] [Accepted: 01/21/2019] [Indexed: 01/14/2023]
Abstract
Much progress has been made during the past 30 years with respect to elucidating the neural and endocrine pathways by which bodily needs for water and energy are brought to conscious awareness through the generation of thirst and hunger. One way that circulating hormones influence thirst and hunger is by acting on neurones within sensory circumventricular organs (CVOs). This is possible because the subfornical organ and organum vasculosum of the lamina terminalis (OVLT), the sensory CVOs in the forebrain, and the area postrema in the hindbrain lack a normal blood-brain barrier such that neurones within them are exposed to blood-borne agents. The neural signals generated by hormonal action in these sensory CVOs are relayed to several sites in the cerebral cortex to stimulate or inhibit thirst or hunger. The subfornical organ and OVLT respond to circulating angiotensin II, relaxin and hypertonicity to drive thirst-related neural pathways, whereas circulating amylin, leptin and possibly glucagon-like peptide-1 act at the area postrema to influence neural pathways inhibiting food intake. As a result of investigations using functional brain imaging techniques, the insula and anterior cingulate cortex, as well as several other cortical sites, have been implicated in the conscious perception of thirst and hunger in humans. Viral tracing techniques show that the anterior cingulate cortex and insula receive neural inputs from thirst-related neurones in the subfornical organ and OVLT, with hunger-related neurones in the area postrema having polysynaptic efferent connections to these cortical regions. For thirst, initially, the median preoptic nucleus and, subsequently, the thalamic paraventricular nucleus and lateral hypothalamus have been identified as likely sites of synaptic links in pathways from the subfornical organ and OVLT to the cortex. The challenge remains to identify the links in the neural pathways that relay signals originating in sensory CVOs to cortical sites subserving either thirst or hunger.
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Affiliation(s)
- Michael J McKinley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
- Department of Physiology, University of Melbourne, Parkville, Victoria, Australia
| | - Derek A Denton
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
- Office of the Dean of Medicine, University of Melbourne, Parkville, Victoria, Australia
| | - Philip J Ryan
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Song T Yao
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Aneta Stefanidis
- Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Brian J Oldfield
- Department of Physiology, Monash University, Clayton, Victoria, Australia
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12
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Ueno H, Yoshimura M, Tanaka K, Nishimura H, Nishimura K, Sonoda S, Motojima Y, Saito R, Maruyama T, Miyamoto T, Serino R, Tamura M, Onaka T, Otsuji Y, Ueta Y. Upregulation of hypothalamic arginine vasopressin by peripherally administered furosemide in transgenic rats expressing arginine vasopressin-enhanced green fluorescent protein. J Neuroendocrinol 2018; 30:e12603. [PMID: 29682811 DOI: 10.1111/jne.12603] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 04/17/2018] [Indexed: 11/30/2022]
Abstract
Furosemide, which is used worldwide as a diuretic agent, inhibits sodium reabsorption in the Henle's loop, resulting in diuresis and natriuresis. Arginine vasopressin (AVP) is synthesized in the supraoptic nucleus (SON), paraventricular nucleus (PVN), and suprachiasmatic nucleus (SCN) of the hypothalamus. The synthesis AVP in the magnocellular neurons of SON and PVN physiologically regulated by plasma osmolality and blood volume and contributed water homeostasis by increasing water reabsorption in the collecting duct. Central AVP dynamics after peripheral administration of furosemide remain unclear. Here, we studied the effects of intraperitoneal (i.p.) administration of furosemide (20 mg/kg) on hypothalamic AVP by using transgenic rats expressing AVP-enhanced green fluorescent protein (eGFP) under the AVP promoter. The i.p. administration of furosemide did not affect plasma osmolality in the present study; however, eGFP in the SON and magnocellular divisions of the PVN (mPVN) were significantly increased after furosemide administration compared to the control. Immunohistochemical analysis revealed Fos-like immunoreactivity (IR) in eGFP-positive neurons in the SON and mPVN 90 min after i.p. administration of furosemide, and AVP heteronuclear (hn) RNA and eGFP mRNA levels were significantly increased. These furosemide-induced changes were not observed in the suprachiasmatic AVP neurons. Furthermore, furosemide induced a remarkable increase in Fos-IR in the organum vasculosum laminae terminals (OVLT), median preoptic nucleus (MnPO), subfornical organ (SFO), locus coeruleus (LC), nucleus of the solitary tract (NTS), and rostral ventrolateral medulla (RVLM) after i.p. administration of furosemide. In conclusion, we were able to visualize and quantitatively evaluate AVP-eGFP synthesis and neuronal activations after peripheral administration of furosemide, using the AVP-eGFP transgenic rats. The results of this study may provide new insights into the elucidation of physiological mechanisms underlying body fluid homeostasis induced by furosemide. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Hiromichi Ueno
- Department of Physiology
- The Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, 807-8555, Japan
| | | | | | | | | | | | | | | | | | - Tetsu Miyamoto
- The Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, 807-8555, Japan
| | - Ryota Serino
- Department of Nephrology, Yoshino Hospital, Kitakyushu, 808-0034, Japan
| | - Masahito Tamura
- The Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, 807-8555, Japan
| | - Tatsushi Onaka
- Division of Brain and Neurophysiology, Department of Physiology, Jichi Medical University, Shimotsuke, 329-0498, Japan
| | - Yutaka Otsuji
- The Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, 807-8555, Japan
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Gizowski C, Zaelzer C, Bourque CW. Activation of organum vasculosum neurons and water intake in mice by vasopressin neurons in the suprachiasmatic nucleus. J Neuroendocrinol 2018; 30. [PMID: 29405459 DOI: 10.1111/jne.12577] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Accepted: 01/27/2018] [Indexed: 01/24/2023]
Abstract
Previous studies have shown that mice housed under 12:12 h light-dark conditions display a pronounced increase in water intake during a 2-hour anticipatory period (AP) near the end of their active period (Zeitgeber Time ZT; ZT21.5-ZT23.5) compared to the preceding basal period (BP, ZT19.5-ZT21.5). This increased water intake during the AP is not associated with physiological stimuli for thirst, such as food intake, hyperosmolality, hyperthermia, or hypovolemia. Denying mice the water intake supplement during the AP causes them to be dehydrated at wake time. These observations suggest that this form of thirst may be driven by the circadian clock and serve to mitigate the dehydrating effect of absence of water intake during sleep. Here we review recent findings showing that this behavior is mediated by vasopressin (VP) containing neurons in the suprachiasmatic nucleus (SCN). SCN VP neurons project to the organum vasculosum lamina terminalis (OVLT) where the activity dependent release of VP causes excitation of thirst-promoting neurons. SCN VP neurons increase their electrical activity during the AP and the resultant release of VP causes an increase in the action potential firing rate of OVLT neurons. Experiments involving optogenetic control of VP release from the axon terminals of SCN neurons indicate that this network mechanism is necessary and sufficient to mediate pre-sleep water intake in mice. These findings provide insight into the output mechanisms that are used by the central clock to generate circadian rhythms, and reveal that the regulation of water intake contributes to osmoregulatory homeostasis during sleep. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Claire Gizowski
- Centre for Research in Neuroscience, Research Institute, of the McGill University Health Centre, Montreal Ge neral Hospital, 1650 Cedar Avenue, Montreal, QC, Canada, H3G1A4
| | - Cristian Zaelzer
- Centre for Research in Neuroscience, Research Institute, of the McGill University Health Centre, Montreal Ge neral Hospital, 1650 Cedar Avenue, Montreal, QC, Canada, H3G1A4
| | - Charles W Bourque
- Centre for Research in Neuroscience, Research Institute, of the McGill University Health Centre, Montreal Ge neral Hospital, 1650 Cedar Avenue, Montreal, QC, Canada, H3G1A4
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14
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Abstract
Water intake is one of the most basic physiological responses and is essential to sustain life. The perception of thirst has a critical role in controlling body fluid homeostasis and if neglected or dysregulated can lead to life-threatening pathologies. Clear evidence suggests that the perception of thirst occurs in higher-order centres, such as the anterior cingulate cortex (ACC) and insular cortex (IC), which receive information from midline thalamic relay nuclei. Multiple brain regions, notably circumventricular organs such as the organum vasculosum lamina terminalis (OVLT) and subfornical organ (SFO), monitor changes in blood osmolality, solute load and hormone circulation and are thought to orchestrate appropriate responses to maintain extracellular fluid near ideal set points by engaging the medial thalamic-ACC/IC network. Thirst has long been thought of as a negative homeostatic feedback response to increases in blood solute concentration or decreases in blood volume. However, emerging evidence suggests a clear role for thirst as a feedforward adaptive anticipatory response that precedes physiological challenges. These anticipatory responses are promoted by rises in core body temperature, food intake (prandial) and signals from the circadian clock. Feedforward signals are also important mediators of satiety, inhibiting thirst well before the physiological state is restored by fluid ingestion. In this Review, we discuss the importance of thirst for body fluid balance and outline our current understanding of the neural mechanisms that underlie the various types of homeostatic and anticipatory thirst.
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Affiliation(s)
- Claire Gizowski
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre and Montreal General Hospital, 1650 Cedar Avenue, Montreal H3G1A4, Canada
| | - Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre and Montreal General Hospital, 1650 Cedar Avenue, Montreal H3G1A4, Canada
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Prager-Khoutorsky M, Choe KY, Levi DI, Bourque CW. Role of Vasopressin in Rat Models of Salt-Dependent Hypertension. Curr Hypertens Rep 2017; 19:42. [PMID: 28451854 DOI: 10.1007/s11906-017-0741-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
PURPOSE OF REVIEW Dietary salt intake increases both plasma sodium and osmolality and therefore increases vasopressin (VP) release from the neurohypophysis. Although this effect could increase blood pressure by inducing fluid reabsorption and vasoconstriction, acute activation of arterial baroreceptors inhibits VP neurons via GABAA receptors to oppose high blood pressure. Here we review recent findings demonstrating that this protective mechanism fails during chronic high salt intake in rats. RECENT FINDINGS Two recent studies showed that chronic high sodium intake causes an increase in intracellular chloride concentration in VP neurons. This effect causes GABAA receptors to become excitatory and leads to the emergence of VP-dependent hypertension. One study showed that the increase in intracellular chloride was provoked by a decrease in the expression of the chloride exporter KCC2 mediated by local secretion of brain-derived neurotrophic factor and activation of TrkB receptors. Prolonged high dietary salt intake can cause pathological plasticity in a central homeostatic circuit that controls VP secretion and thereby contribute to peripheral vasoconstriction and hypertension.
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Affiliation(s)
- Masha Prager-Khoutorsky
- Department of Physiology, McGill University, McIntyre Medical Sciences Bldg., 3655 Promenade Sir-William Osler, Montreal, QC, H3G 1Y6, Canada
| | - Katrina Y Choe
- 2309 Gonda Neuroscience and Genetics Research Center, UCLA Department of Neurology, 695 Charles E. Young Dr. South, Los Angeles, CA, 90095, USA
| | - David I Levi
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Center, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC, H3G 1A4, Canada
| | - Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Center, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC, H3G 1A4, Canada.
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Kinsman BJ, Browning KN, Stocker SD. NaCl and osmolarity produce different responses in organum vasculosum of the lamina terminalis neurons, sympathetic nerve activity and blood pressure. J Physiol 2017; 595:6187-6201. [PMID: 28678348 DOI: 10.1113/jp274537] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2017] [Accepted: 06/21/2017] [Indexed: 01/12/2023] Open
Abstract
KEY POINTS Changes in extracellular osmolarity stimulate thirst and vasopressin secretion through a central osmoreceptor; however, central infusion of hypertonic NaCl produces a greater sympathoexcitatory and pressor response than infusion of hypertonic mannitol/sorbitol. Neurons in the organum vasculosum of the lamina terminalis (OVLT) sense changes in extracellular osmolarity and NaCl. In this study, we discovered that intracerebroventricular infusion or local OVLT injection of hypertonic NaCl increases lumbar sympathetic nerve activity, adrenal sympathetic nerve activity and arterial blood pressure whereas equi-osmotic mannitol/sorbitol did not alter any variable. In vitro whole-cell recordings demonstrate the majority of OVLT neurons are responsive to hypertonic NaCl or mannitol. However, hypertonic NaCl stimulates a greater increase in discharge frequency than equi-osmotic mannitol. Intracarotid or intracerebroventricular infusion of hypertonic NaCl evokes a greater increase in OVLT neuronal discharge frequency than equi-osmotic sorbitol. Collectively, these novel data suggest that subsets of OVLT neurons respond differently to hypertonic NaCl versus osmolarity and subsequently regulate body fluid homeostasis. These responses probably reflect distinct cellular mechanisms underlying NaCl- versus osmo-sensing. ABSTRACT Systemic or central infusion of hypertonic NaCl and other osmolytes readily stimulate thirst and vasopressin secretion. In contrast, central infusion of hypertonic NaCl produces a greater increase in arterial blood pressure (ABP) than equi-osmotic mannitol/sorbitol. Although these responses depend on neurons in the organum vasculosum of the lamina terminalis (OVLT), these observations suggest OVLT neurons may sense or respond differently to hypertonic NaCl versus osmolarity. The purpose of this study was to test this hypothesis in Sprague-Dawley rats. First, intracerebroventricular (icv) infusion (5 μl/10 min) of 1.0 m NaCl produced a significantly greater increase in lumbar sympathetic nerve activity (SNA), adrenal SNA and ABP than equi-osmotic sorbitol (2.0 osmol l-1 ). Second, OVLT microinjection (20 nl) of 1.0 m NaCl significantly raised lumbar SNA, adrenal SNA and ABP. Equi-osmotic sorbitol did not alter any variable. Third, in vitro whole-cell recordings demonstrate that 50% (18/36) of OVLT neurons display an increased discharge to both hypertonic NaCl (+7.5 mm) and mannitol (+15 mm). Of these neurons, 56% (10/18) displayed a greater discharge response to hypertonic NaCl vs mannitol. Fourth, in vivo single-unit recordings revealed that intracarotid injection of hypertonic NaCl produced a concentration-dependent increase in OVLT cell discharge, lumbar SNA and ABP. The responses to equi-osmotic infusions of hypertonic sorbitol were significantly smaller. Lastly, icv infusion of 0.5 m NaCl produced significantly greater increases in OVLT discharge and ABP than icv infusion of equi-osmotic sorbitol. Collectively, these findings indicate NaCl and osmotic stimuli produce different responses across OVLT neurons and may represent distinct cellular processes to regulate thirst, vasopressin secretion and autonomic function.
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Affiliation(s)
- Brian J Kinsman
- Department of Medicine, Division of Renal-Electrolyte, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA.,Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, PA, 17033, USA
| | - Sean D Stocker
- Department of Medicine, Division of Renal-Electrolyte, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
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17
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Abstract
Thirst motivates animals to find and consume water. More than 40 years ago, a set of interconnected brain structures known as the lamina terminalis was shown to govern thirst. However, owing to the anatomical complexity of these brain regions, the structure and dynamics of their underlying neural circuitry have remained obscure. Recently, the emergence of new tools for neural recording and manipulation has reinvigorated the study of this circuit and prompted re-examination of longstanding questions about the neural origins of thirst. Here, we review these advances, discuss what they teach us about the control of drinking behaviour and outline the key questions that remain unanswered.
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Affiliation(s)
- Christopher A Zimmerman
- Department of Physiology, the Kavli Institute for Fundamental Neuroscience and the Neuroscience Graduate Program, University of California San Francisco, San Francisco, California 94158, USA
| | - David E Leib
- Department of Physiology, the Kavli Institute for Fundamental Neuroscience and the Neuroscience Graduate Program, University of California San Francisco, San Francisco, California 94158, USA
| | - Zachary A Knight
- Department of Physiology, the Kavli Institute for Fundamental Neuroscience and the Neuroscience Graduate Program, University of California San Francisco, San Francisco, California 94158, USA
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18
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Chronic high-sodium diet intake after weaning lead to neurogenic hypertension in adult Wistar rats. Sci Rep 2017; 7:5655. [PMID: 28720883 PMCID: PMC5515999 DOI: 10.1038/s41598-017-05984-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 06/06/2017] [Indexed: 02/07/2023] Open
Abstract
In this study, we investigated some mechanisms involved in sodium-dependent hypertension of rats exposed to chronic salt (NaCl) intake from weaning until adult age. Weaned male Wistar rats were placed under high (0.90% w/w, HS) or regular (0.27% w/w, Cont) sodium diets for 12 weeks. Water consumption, urine output and sodium excretion were higher in HS rats compared to control. Blood pressure (BP) was directly measured by the arterial catheter and found 13.8% higher in HS vs Cont rats. Ganglionic blockade with hexamethonium caused greater fall in the BP of HS rats (33%), and central antagonism of AT1 receptors (losartan) microinjected into the lateral ventricle reduced BP level of HS, but not of Cont group. Heart rate variability analysis revealed sympathetic prevalence on modulation of the systolic interval. HS diet did not affect creatinine clearance. Kidney histological analysis revealed no significant change in renal corpuscle structure. Sodium and potassium concentrations in CSF were found higher in HS rats despite no change in plasma concentration of these ions. Taken together, data suggest that animals exposed to chronic salt intake to a level close to that reported for human' diet since weaning lead to hypertension, which appears to rely on sodium-driven neurogenic mechanisms.
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Zaelzer C, Hua P, Prager-Khoutorsky M, Ciura S, Voisin D, Liedtke W, Bourque C. ΔN-TRPV1: A Molecular Co-detector of Body Temperature and Osmotic Stress. Cell Rep 2015; 13:23-30. [DOI: 10.1016/j.celrep.2015.08.061] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 07/25/2015] [Accepted: 08/21/2015] [Indexed: 10/23/2022] Open
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20
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Graebner AK, Iyer M, Carter ME. Understanding how discrete populations of hypothalamic neurons orchestrate complicated behavioral states. Front Syst Neurosci 2015; 9:111. [PMID: 26300745 PMCID: PMC4523943 DOI: 10.3389/fnsys.2015.00111] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Accepted: 07/16/2015] [Indexed: 01/01/2023] Open
Abstract
A major question in systems neuroscience is how a single population of neurons can interact with the rest of the brain to orchestrate complex behavioral states. The hypothalamus contains many such discrete neuronal populations that individually regulate arousal, feeding, and drinking. For example, hypothalamic neurons that express hypocretin (Hcrt) neuropeptides can sense homeostatic and metabolic factors affecting wakefulness and orchestrate organismal arousal. Neurons that express agouti-related protein (AgRP) can sense the metabolic needs of the body and orchestrate a state of hunger. The organum vasculosum of the lamina terminalis (OVLT) can detect the hypertonicity of blood and orchestrate a state of thirst. Each hypothalamic population is sufficient to generate complicated behavioral states through the combined efforts of distinct efferent projections. The principal challenge to understanding these brain systems is therefore to determine the individual roles of each downstream projection for each behavioral state. In recent years, the development and application of temporally precise, genetically encoded tools has greatly improved our understanding of the structure and function of these neural systems. This review will survey recent advances in our understanding of how these individual hypothalamic populations can orchestrate complicated behavioral states due to the combined efforts of individual downstream projections.
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Affiliation(s)
- Allison K Graebner
- Program in Neuroscience, Department of Biology, Williams College Williamstown, MA, USA
| | - Manasi Iyer
- Program in Neuroscience, Department of Biology, Williams College Williamstown, MA, USA
| | - Matthew E Carter
- Program in Neuroscience, Department of Biology, Williams College Williamstown, MA, USA
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21
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de Souza Mecawi A, Ruginsk SG, Elias LLK, Varanda WA, Antunes‐Rodrigues J. Neuroendocrine Regulation of Hydromineral Homeostasis. Compr Physiol 2015; 5:1465-516. [DOI: 10.1002/cphy.c140031] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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22
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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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23
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Prager-Khoutorsky M, Bourque CW. Anatomical organization of the rat organum vasculosum laminae terminalis. Am J Physiol Regul Integr Comp Physiol 2015; 309:R324-37. [PMID: 26017494 DOI: 10.1152/ajpregu.00134.2015] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 05/26/2015] [Indexed: 11/22/2022]
Abstract
The organum vasculosum of the laminae terminalis (OVLT) is a circumventricular organ located along the ventral part of the anterior wall of the third ventricle. Because it lacks a complete blood-brain barrier (BBB), blood-borne signals detected in the OVLT provide the brain with information from the periphery and contribute to the generation of centrally mediated responses to humoral feedback and physiological stressors. Experimental studies on the rat OVLT are hindered by a poor understanding of its precise anatomical dimensions and cellular organization. In this study, we use histological techniques to characterize the spatial outline of the rat OVLT and to examine the location of neurons, astrocytes, tanycytes, and ependymocytes within its confines. Our data reveal that OVLT neurons are embedded in a dense network of tanycyte processes. Immunostaining against the neuronal marker NeuN revealed that neurons are distributed throughout the OVLT, except for a thick midline septum, which comprises densely packed cells of unknown function or lineage. Moreover, the most ventral aspect of the OVLT is devoid of neurons and is occupied by a dense network of glial cell processes that form a thick layer between the neurons and the pial surface on the ventral aspect of the nucleus. Lastly, combined detection of NeuN and c-Fos protein following systemic injection of hypertonic NaCl revealed that neurons responsive to this stimulus are located along the entire midline core of the OVLT, extending from its most anterior ventral aspect to the more caudally located "dorsal cap" region.
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Affiliation(s)
- Masha Prager-Khoutorsky
- Center for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - Charles W Bourque
- Center for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
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Mecawi AS, Macchione AF, Nuñez P, Perillan C, Reis LC, Vivas L, Arguelles J. Developmental programing of thirst and sodium appetite. Neurosci Biobehav Rev 2015; 51:1-14. [DOI: 10.1016/j.neubiorev.2014.12.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 12/05/2014] [Accepted: 12/09/2014] [Indexed: 01/17/2023]
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Abstract
Alterations in water homeostasis can disturb cell size and function. Although most cells can internally regulate cell volume in response to osmolar stress, neurons are particularly at risk given a combination of complex cell function and space restriction within the calvarium. Thus, regulating water balance is fundamental to survival. Through specialized neuronal "osmoreceptors" that sense changes in plasma osmolality, vasopressin release and thirst are titrated in order to achieve water balance. Fine-tuning of water absorption occurs along the collecting duct, and depends on unique structural modifications of renal tubular epithelium that confer a wide range of water permeability. In this article, we review the mechanisms that ensure water homeostasis as well as the fundamentals of disorders of water balance.
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Affiliation(s)
- John Danziger
- Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts
| | - Mark L Zeidel
- Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts
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26
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Gagnon A, Walsh M, Okuda T, Choe KY, Zaelzer C, Bourque CW. Modulation of spike clustering by NMDA receptors and neurotensin in rat supraoptic nucleus neurons. J Physiol 2014; 592:4177-86. [PMID: 25063824 DOI: 10.1113/jphysiol.2014.275602] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Magnocellular neurosecretory cells (MNCs) in the rat supraoptic nucleus display clustered firing during hyperosmolality or dehydration. This response is beneficial because this type of activity potentiates vasopressin secretion from axon terminals in the neurohypophysis and thus promotes homoeostatic water reabsorption from the kidney. However, the mechanisms which lead to the generation of clustering activity in MNCs remain unknown. Previous work has shown that clustered firing can be induced in these neurons through the pharmacological activation of NMDA receptors (NMDARs) and that silent pauses observed during this activity are mediated by apamin-sensitive calcium activated potassium (SK) channels. However, it remains unknown if clustered firing can be induced in situ by endogenous glutamate release from axon terminals. Here we show that electrical stimulation of glutamatergic osmosensory afferents in the organum vasculosum lamina terminalis (OVLT) can promote clustering in MNCs via NMDARs and apamin-sensitive channels.We also show that the rate of spike clustering induced by NMDA varies as a bell-shaped function of voltage, and that partial inhibition of SK channels can increase cluster duration and reduce the rate of clustering. Finally,we show that MNCs express neurotensin type 2 receptors, and that activation of these receptors can simultaneously depolarize MNCs and suppress clustered firing induced by bath application of NMDA or by repetitive stimulation of glutamate afferents. These studies reveal that spike clustering can be induced in MNCs by glutamate release from afferent nerve terminals and that that this type of activity can be fine-tuned by neuromodulators such as neurotensin.
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Affiliation(s)
- Ariane Gagnon
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal QC, Canada H3G 1A4
| | - Michael Walsh
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal QC, Canada H3G 1A4
| | - Tika Okuda
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal QC, Canada H3G 1A4
| | - Katrina Y Choe
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal QC, Canada H3G 1A4
| | - Cristian Zaelzer
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal QC, Canada H3G 1A4
| | - Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal QC, Canada H3G 1A4
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Grafe LA, Takacs AE, Yee DK, Flanagan-Cato LM. The role of the hypothalamic paraventricular nucleus and the organum vasculosum lateral terminalis in the control of sodium appetite in male rats. J Neurosci 2014; 34:9249-60. [PMID: 25009258 PMCID: PMC4087205 DOI: 10.1523/jneurosci.3979-13.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 05/16/2014] [Accepted: 06/05/2014] [Indexed: 11/21/2022] Open
Abstract
Angiotensin II (AngII) and aldosterone cooperate centrally to produce a robust sodium appetite. The intracellular signaling and circuitry that underlie this interaction remain unspecified. Male rats pretreated with both deoxycorticosterone (DOC; a synthetic precursor of aldosterone) and central AngII exhibited a marked sodium intake, as classically described. Disruption of inositol trisphosphate signaling, but not extracellular-regulated receptor kinase 1 and 2 signaling, prevented the cooperativity of DOC and AngII on sodium intake. The pattern of expression of the immediate early gene product cFos was used to identify key brain regions that may underlie this behavior. In the paraventricular nuclei (PVN) of the hypothalamus, DOC pretreatment diminished both AngII-induced cFos induction and neurosecretion of oxytocin, a peptide expressed in the PVN. Conversely, in the organum vasculosum lateral terminalis (OVLT), DOC pretreatment augmented cFos expression. Immunohistochemistry identified a substantial presence of oxytocin fibers in the OVLT. In addition, when action potentials in the PVN were inhibited with intraparenchymal lidocaine, AngII-induced sodium ingestion was exaggerated. Intriguingly, this treatment also increased the number of neurons in the OVLT expressing AngII-induced cFos. Collectively, these results suggest that the behavioral cooperativity between DOC and AngII involves the alleviation of an inhibitory oxytocin signal, possibly relayed directly from the PVN to the OVLT.
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Affiliation(s)
| | | | | | - Loretta M Flanagan-Cato
- Neuroscience Graduate Group, Departments of Psychology and the Mahoney Institute of Neurological Sciences, University of Pennsylvania, Philadelphia Pennsylvania 19104
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28
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Dine J, Ducourneau VRR, Fénelon VS, Fossat P, Amadio A, Eder M, Israel JM, Oliet SHR, Voisin DL. Extracellular signal-regulated kinase phosphorylation in forebrain neurones contributes to osmoregulatory mechanisms. J Physiol 2014; 592:1637-54. [PMID: 24492838 DOI: 10.1113/jphysiol.2013.261008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Vasopressin secretion from the magnocellular neurosecretory cells (MNCs) is crucial for body fluid homeostasis. Osmotic regulation of MNC activity involves the concerted modulation of intrinsic mechanosensitive ion channels, taurine release from local astrocytes as well as excitatory inputs derived from osmosensitive forebrain regions. Extracellular signal-regulated protein kinases (ERK) are mitogen-activated protein kinases that transduce extracellular stimuli into intracellular post-translational and transcriptional responses, leading to changes in intrinsic neuronal properties and synaptic function. Here, we investigated whether ERK activation (i.e. phosphorylation) plays a role in the functioning of forebrain osmoregulatory networks. We found that within 10 min after intraperitoneal injections of hypertonic saline (3 m, 6 m) in rats, many phosphoERK-immunopositive neurones were observed in osmosensitive forebrain regions, including the MNC containing supraoptic nuclei. The intensity of ERK labelling was dose-dependent. Reciprocally, slow intragastric infusions of water that lower osmolality reduced basal ERK phosphorylation. In the supraoptic nucleus, ERK phosphorylation predominated in vasopressin neurones vs. oxytocin neurones and was absent from astrocytes. Western blot experiments confirmed that phosphoERK expression in the supraoptic nucleus was dose dependent. Intracerebroventricular administration of the ERK phosphorylation inhibitor U 0126 before a hyperosmotic challenge reduced the number of both phosphoERK-immunopositive neurones and Fos expressing neurones in osmosensitive forebrain regions. Blockade of ERK phosphorylation also reduced hypertonically induced depolarization and an increase in firing of the supraoptic MNCs recorded in vitro. It finally reduced hypertonically induced vasopressin release in the bloodstream. Altogether, these findings identify ERK phosphorylation as a new element contributing to the osmoregulatory mechanisms of vasopressin release.
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Affiliation(s)
- Julien Dine
- Inserm, U862, Neurocentre Magendie, Université de Bordeaux, 146 Rue Léo-Saignat, F-33077 Bordeaux, France.
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29
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Antunes-Rodrigues J, Ruginsk SG, Mecawi AS, Margatho LO, Cruz JC, Vilhena-Franco T, Reis WL, Ventura RR, Reis LC, Vivas LM, Elias LLK. Mapping and signaling of neural pathways involved in the regulation of hydromineral homeostasis. Braz J Med Biol Res 2013; 46:327-38. [PMID: 23579631 PMCID: PMC3854407 DOI: 10.1590/1414-431x20132788] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Accepted: 02/05/2013] [Indexed: 11/22/2022] Open
Abstract
Several forebrain and brainstem neurochemical circuitries interact with
peripheral neural and humoral signals to collaboratively maintain both the
volume and osmolality of extracellular fluids. Although much progress has been
made over the past decades in the understanding of complex mechanisms underlying
neuroendocrine control of hydromineral homeostasis, several issues still remain
to be clarified. The use of techniques such as molecular biology, neuronal
tracing, electrophysiology, immunohistochemistry, and microinfusions has
significantly improved our ability to identify neuronal phenotypes and their
signals, including those related to neuron-glia interactions. Accordingly,
neurons have been shown to produce and release a large number of chemical
mediators (neurotransmitters, neurohormones and neuromodulators) into the
interstitial space, which include not only classic neurotransmitters, such as
acetylcholine, amines (noradrenaline, serotonin) and amino acids (glutamate,
GABA), but also gaseous (nitric oxide, carbon monoxide and hydrogen sulfide) and
lipid-derived (endocannabinoids) mediators. This efferent response, initiated
within the neuronal environment, recruits several peripheral effectors, such as
hormones (glucocorticoids, angiotensin II, estrogen), which in turn modulate
central nervous system responsiveness to systemic challenges. Therefore, in this
review, we shall evaluate in an integrated manner the physiological control of
body fluid homeostasis from the molecular aspects to the systemic and integrated
responses.
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Affiliation(s)
- J Antunes-Rodrigues
- Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
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30
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Gabor A, Leenen FHH. Cardiovascular effects of angiotensin II and glutamate in the PVN of Dahl salt-sensitive rats. Brain Res 2012; 1447:28-37. [PMID: 22356885 DOI: 10.1016/j.brainres.2012.01.060] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 01/23/2012] [Accepted: 01/24/2012] [Indexed: 11/28/2022]
Abstract
Several models of chronic sympathetic hyperactivity are associated with an increase in excitatory angiotensinergic and glutamatergic activity, and a decrease in GABAergic activity in the PVN. The present study evaluated whether activation of glutamate and AT1 receptors in the PVN contributes to the maintenance of resting BP in Dahl salt sensitive (S) rats on regular or high salt diet for 4-6 weeks. Candesartan and kynurenate were infused bilaterally into the PVN and BP and heart rate (HR) were recorded. Both candesartan and kynurenate in the PVN did not change MAP and HR in normotensive Dahl salt resistant (R) and S rats on regular salt diet or in R rats on high salt diet. In hypertensive Dahl S rats on high salt diet, candesartan decreased MAP (-14±2 mm Hg), and tended to increase HR (22±5 bpm). Kynurenate decreased both MAP (-22±3 mm Hg) and HR (-42±7 bpm) in these rats. At the peak BP decrease by candesartan, kynurenate in the PVN further decreased BP by ~50% (-14±2 mm Hg), whereas candesartan did not further decrease BP at the peak BP response to kynurenate (-4±2 mm Hg). These results indicate that activation of glutamate and AT1-receptors in the PVN contributes to the maintenance of BP in hypertensive Dahl S rats, but not normotensive Dahl S and R rats. The increased BP response to AT1-receptor activation in the PVN of hypertensive Dahl S appears to be mediated by enhanced local glutamate receptor activation, but another mechanism(s) appears to further enhance glutamate responses.
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Affiliation(s)
- Alexander Gabor
- Hypertension Unit, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
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31
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Hypertonicity sensing in organum vasculosum lamina terminalis neurons: a mechanical process involving TRPV1 but not TRPV4. J Neurosci 2011; 31:14669-76. [PMID: 21994383 DOI: 10.1523/jneurosci.1420-11.2011] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Primary osmosensory neurons in the mouse organum vasculosum lamina terminalis (OVLT) transduce hypertonicity via the activation of nonselective cation channels that cause membrane depolarization and increased action potential discharge, and this effect is absent in mice lacking expression of the transient receptor potential vanilloid 1 (Trpv1) gene (Ciura and Bourque, 2006). However other experiments have indicated that channels encoded by Trpv4 also contribute to central osmosensation in mice (Liedtke and Friedman, 2003; Mizuno et al., 2003). At present, the mechanism by which hypertonicity modulates cation channels in OVLT neurons is unknown, and it remains unclear whether Trpv1 and Trpv4 both contribute to this process. Here, we show that physical shrinking is necessary and sufficient to mediate hypertonicity sensing in OVLT neurons isolated from adult mice. Steps coupling progressive decreases in cell volume to increased neuronal activity were quantitatively equivalent whether shrinking was evoked by osmotic pressure or mechanical aspiration. Finally, modulation of OVLT neurons by tonicity or mechanical stimulation was unaffected by deletion of trpv4 but was abolished in cells lacking Trpv1 or wild-type neurons treated with the TRPV1 antagonist SB366791. Thus, hypertonicity sensing is a mechanical process requiring Trpv1, but not Trpv4.
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32
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Dalmasso C, Amigone JL, Vivas L. Serotonergic system involvement in the inhibitory action of estrogen on induced sodium appetite in female rats. Physiol Behav 2011; 104:398-407. [DOI: 10.1016/j.physbeh.2011.04.029] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 04/20/2011] [Accepted: 04/22/2011] [Indexed: 11/29/2022]
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Sinke AP, Deen PMT. The physiological implication of novel proteins in systemic osmoregulation. FASEB J 2011; 25:3279-89. [PMID: 21737616 DOI: 10.1096/fj.11-188433] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Maintenance of the osmobalance is important for life. In this process, in which brain and kidney act in concert, mammals have to cope with significant deviations as drinking water reduces plasma osmolality, whereas salty food increases it. To restore homeostasis, specialized nuclei within the hypothalamus play a pivotal role in detecting changes in plasma osmolality and initiating appropriate responses. These responses are accomplished by either changing the intake of water or the excretion of water by the kidney. In the past decade, several novel findings have made significant contributions to our insights in the process of systemic osmoregulation. Novel proteins have been identified in the brain as well as in the kidney that are fulfilling important roles in the process of systemic osmoregulation. In this review, recent evidence of the involvement of TRPV channels (TRPV1, TRPV2, and TRPV4) and proteins, such as sodium channels NALCN and Na(x), in neuronal osmoregulation, as well as; e.g., the purinergic P2Y2 receptor in renal osmoregulation, are discussed, and integrated with existing knowledge of systemic osmoregulation.
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Affiliation(s)
- Anne P Sinke
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Sisó S, Jeffrey M, González L. Sensory circumventricular organs in health and disease. Acta Neuropathol 2010; 120:689-705. [PMID: 20830478 DOI: 10.1007/s00401-010-0743-5] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 08/17/2010] [Accepted: 08/22/2010] [Indexed: 02/07/2023]
Abstract
Circumventricular organs (CVOs) are specialized brain structures located around the third and fourth ventricles. They differ from the rest of the brain parenchyma in that they are highly vascularised areas that lack a blood-brain barrier. These neurohaemal organs are classified as "sensory", when they contain neurons that can receive chemical inputs from the bloodstream. This review focuses on the sensory CVOs to describe their unique structure, and their functional roles in the maintenance of body fluid homeostasis and cardiovascular regulation, and in the generation of central acute immune and febrile responses. In doing so, the main neural connections to visceral regulatory centres such as the hypothalamus, the medulla oblongata and the endocrine hypothalamic-pituitary axis, as well as some of the relevant chemical substances involved, are described. The CVOs are vulnerable to circulating pathogens and can be portals for their entry in the brain. This review highlights recent investigations that show that the CVOs and related structures are involved in pathological conditions such as sepsis, stress, trypanosomiasis, autoimmune encephalitis, systemic amyloidosis and prion infections, while detailed information on their role in other neurodegenerative diseases such as Alzheimer's disease or multiple sclerosis is lacking. It is concluded that studies of the CVOs and related structures may help in the early diagnosis and treatment of such disorders.
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Affiliation(s)
- Sílvia Sisó
- Department of Pathology, Pentlands Science Park, Penicuik, Midlothian, Scotland, UK.
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35
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Central clock excites vasopressin neurons by waking osmosensory afferents during late sleep. Nat Neurosci 2010; 13:467-74. [PMID: 20190744 DOI: 10.1038/nn.2503] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Accepted: 01/08/2010] [Indexed: 02/08/2023]
Abstract
Osmoregulated vasopressin release is facilitated during the late sleep period (LSP) to prevent dehydration and enuresis. Previous work has shown that clock neurons in the suprachiasmatic nucleus (SCN) have low firing rates during the LSP, but it is not known how this reduced activity enhances vasopressin release. We found that synaptic excitation of rat supraoptic nucleus neurons by osmosensory afferents is facilitated during the LSP. Stimulation of the SCN at this time inhibited excitatory synaptic currents induced in supraoptic neurons by activation of osmosensory afferents. This effect was associated with an increased rate of synaptic failures and occurred without changes in frequency facilitation, quantal size or in the ratio of postsynaptic responses mediated by AMPA and NMDA receptors. We conclude that clock neurons mediate an activity-dependent presynaptic silencing of osmosensory afferent synapses onto vasopressin neurons and that osmoregulatory gain is enhanced by removal of this effect during late sleep.
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36
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Godino A, Margatho LO, Caeiro XE, Antunes-Rodrigues J, Vivas L. Activation of lateral parabrachial afferent pathways and endocrine responses during sodium appetite regulation. Exp Neurol 2010; 221:275-84. [DOI: 10.1016/j.expneurol.2009.11.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Revised: 10/05/2009] [Accepted: 11/03/2009] [Indexed: 11/29/2022]
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Maejima S, Yamada T, Hamada T, Matsuda K, Uchiyama M. Effects of hypertonic stimuli and arginine vasotocin (AVT) on water absorption response in Japanese treefrog, Hyla japonica. Gen Comp Endocrinol 2008; 157:196-202. [PMID: 18555070 DOI: 10.1016/j.ygcen.2008.04.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2008] [Revised: 04/09/2008] [Accepted: 04/28/2008] [Indexed: 10/22/2022]
Abstract
Anuran amphibians do not drink orally but absorb water osmotically through the highly permeable ventral skin. In this cutaneous water absorption, roles of the putative cerebral osmoreceptors and functions of arginine vasotocin (AVT) were examined in the central nervous system of the Japanese treefrog, Hyla japonica. Intracerebroventricular (ICV) or intralymphatic sac (ILS) administration of various hypertonic solutions (NaCl, mannitol and urea) significantly extended the residence time in water in a dose-dependent manner, suggesting facilitation of water absorption in frogs. ICV injection of AVT also increased significantly the residence time in a dose-dependent manner. The water absorption effect of AVT was significantly inhibited by pretreatment of ICV OPC-21268, a vasopressin V(1) receptor antagonist. But pre-ICV injection of OPC-31260, a vasopressin V(2) receptor antagonist, did not block the water absorption effect of AVT. Extension of the residence time induced by hyperosmotic NaCl (1000 mOsm) ICV injection was significantly inhibited by pretreatment of ICV OPC-21268. The present results showed that increases of osmotic pressure in plasma and/or cerebrospinal fluid stimulate water absorption response, suggesting that osmoreceptors are certainly present in the central nervous system and AVT may directly stimulate water absorption in the treefrog. It is also suggested that AVT activates cellular mechanisms via V(1)-like but not V(2)-like receptors in the central nervous system and facilitates water absorption response in the treefrog.
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Affiliation(s)
- Sho Maejima
- Department of Biological Science, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 9308555, Japan
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38
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Abstract
Systemic osmoregulation is a vital process whereby changes in plasma osmolality, detected by osmoreceptors, modulate ingestive behaviour, sympathetic outflow and renal function to stabilize the tonicity and volume of the extracellular fluid. Furthermore, changes in the central processing of osmosensory signals are likely to affect the hydro-mineral balance and other related aspects of homeostasis, including thermoregulation and cardiovascular balance. Surprisingly little is known about how the brain orchestrates these responses. Here, recent advances in our understanding of the molecular, cellular and network mechanisms that mediate the central control of osmotic homeostasis in mammals are reviewed.
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Affiliation(s)
- Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Room L7-216, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec, H3G 1A4, Canada.
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Sharif-Naeini R, Ciura S, Zhang Z, Bourque C. Contribution of TRPV channels to osmosensory transduction, thirst, and vasopressin release. Kidney Int 2008; 73:811-5. [DOI: 10.1038/sj.ki.5002788] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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40
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Caeiro X, Vivas L. β-Endorphin in the median preoptic nucleus modulates the pressor response induced by subcutaneous hypertonic sodium chloride. Exp Neurol 2008; 210:59-66. [DOI: 10.1016/j.expneurol.2007.09.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2007] [Revised: 09/25/2007] [Accepted: 09/28/2007] [Indexed: 11/26/2022]
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41
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Badauê-Passos D, Godino A, Johnson AK, Vivas L, Antunes-Rodrigues J. Dorsal raphe nuclei integrate allostatic information evoked by depletion-induced sodium ingestion. Exp Neurol 2007; 206:86-94. [PMID: 17544397 DOI: 10.1016/j.expneurol.2007.04.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2006] [Revised: 03/16/2007] [Accepted: 04/07/2007] [Indexed: 11/17/2022]
Abstract
Structures of the lamina terminalis (LT) sense and integrate information reflecting the state of body water and sodium content. Output from the LT projects into a neural network that regulates body fluid balance. Serotonin (5-HT) and the dorsal raphe nuclei (DRN) have been implicated in the inhibitory control of salt intake (i.e., sodium appetite). Signals arriving from the LT evoked by fluid depletion-induced sodium ingestion interact with this inhibitory serotonergic system. We investigated the role of neurons along the LT that directly project to the DRN. We analyzed the pattern of immunoreactivity (ir) of LT cells double-labeled for Fos (a marker of neural activity) and Fluorogold (FG; a retrograde tracer) following sodium depletion-induced sodium intake. Seven days after injection of FG into the DRN, sodium appetite was induced by furosemide injection and overnight access to only a low sodium diet (Furo-LSD) and distilled water. Twenty-four hours later, access to 0.3 M NaCl was given to depleted or sham-depleted rats and sodium intake was measured over the following 60 min. Ninety minutes after the termination of the intake test, the animals were perfused and their brains were processed for immunohistochemical detection of Fos and FG. Compared to sham-depleted animals there was a significantly greater number of Fos-/FG-ir double-labeled cells in the subfornical organ, the organum vasculosum of the lamina terminalis and the median preoptic nucleus in rats that ingested NaCl. Projections from the LT cells may contribute to inhibitory mechanisms involving 5-HT neurons in the DRN that limit the intake of sodium and prevent excess volume expansion.
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Affiliation(s)
- Daniel Badauê-Passos
- Departmento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Brazil.
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Bourque CW, Ciura S, Trudel E, Stachniak TJE, Sharif-Naeini R. Neurophysiological characterization of mammalian osmosensitive neurones. Exp Physiol 2007; 92:499-505. [PMID: 17350993 PMCID: PMC5021534 DOI: 10.1113/expphysiol.2006.035634] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In mammals, the osmolality of the extracellular fluid is maintained near a predetermined set-point through a negative feedback regulation of thirst, diuresis, salt appetite and natriuresis. This homeostatic control is believed to be mediated by osmosensory neurones which synaptically regulate the electrical activity of command neurones that mediate each of these osmoregulatory effector responses. Our present understanding of the molecular, cellular and network basis that underlies the central control of osmoregulation is largely derived from studies on primary osmosensory neurones in the organum vasculosum lamina terminalis (OVLT) and effector neurones in the supraoptic nucleus (SON), which release hormones that regulate diuresis and natriuresis. Primary osmosensory neurones in the OVLT exhibit changes in action potential firing rate that vary in proportion with ECF osmolality. This effect results from the intrinsic depolarizing receptor potential which these cells generate via a molecular transduction complex that may comprise various members of the transient receptor potential vanilloid (TRPV) family of cation channel proteins, notably TRPV1 and TRPV4. Osmotically evoked changes in the firing rate of OVLT neurones then regulate the electrical activity of downstream neurones in the SON through graded changes in glutamate release.
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Affiliation(s)
- Charles W Bourque
- Centre for Research in Neuroscience, Montreal General Hospital and McGill University, 1650 Cedar Avenue, Montreal QC, Canada H3G 1A4.
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Ho JM, Zierath DK, Savos AV, Femiano DJ, Bassett JE, McKinley MJ, Fitts DA. Differential effects of intravenous hyperosmotic solutes on drinking latency and c-Fos expression in the circumventricular organs and hypothalamus of the rat. Am J Physiol Regul Integr Comp Physiol 2006; 292:R1690-8. [PMID: 17194726 DOI: 10.1152/ajpregu.00547.2006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hyperosmotic intravenous infusions of NaCl are more potent for inducing drinking and vasopressin (AVP) secretion than equally osmotic solutions of glucose or urea. The fact that all three solutes increased cerebrospinal fluid osmolality and sodium concentration led the investigators to conclude that critical sodium receptors or osmoreceptors for stimulating drinking and AVP secretion were outside the blood-brain barrier (BBB) in the circumventricular organs (CVOs). We tested an obvious prediction of this hypothesis: that all three solutes should increase c-Fos-like immunoreactivity (Fos-ir) inside the BBB, but that only NaCl should increase Fos-ir in the CVOs. We gave intravenous infusions of 3.0 Osm/l NaCl, glucose, or urea to rats for 11 or 22 min at 0.14 ml/min and perfused the rats for assay of Fos-ir at 90 min. Controls received isotonic NaCl at the same volume. Drinking latency was measured, but water was then removed. Drinking consistently occurred with short latency during hyperosmotic NaCl infusions only. Fos-ir in the forebrain CVOs, the subfornical organ, and organum vasculosum laminae terminalis was consistently elevated only by hyperosmotic NaCl. However, all three hyperosmotic solutes potently stimulated Fos-ir in the supraoptic and paraventricular nuclei of the hypothalamus inside the BBB. Hyperosmotic NaCl greatly elevated Fos-ir in the area postrema, but even glucose and urea caused moderate elevations that may be related to volume expansion rather than osmolality. The data provide strong support for the conclusion that the osmoreceptors controlling drinking are located in the CVOs.
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Affiliation(s)
- Jacqueline M Ho
- Department of Psychology, University of Washington, Box 351525, Seattle, WA 98195-1525, USA
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McKinley MJ, Denton DA, Oldfield BJ, De Oliveira LB, Mathai ML. Water intake and the neural correlates of the consciousness of thirst. Semin Nephrol 2006; 26:249-57. [PMID: 16713498 DOI: 10.1016/j.semnephrol.2006.02.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Thirst and resultant water drinking can arise in response to deficits in both the intracellular and extracellular fluid compartments. Inhibitory influences mediating the satiation of thirst also are necessary to prevent overhydration. The brain regions that underpin the generation or inhibition of thirst in these circumstances can be categorized as sensory, integrative, or cortical effector sites. The anterior cingulate cortex and insula are activated in thirsty human beings as shown by functional brain-imaging techniques. It is postulated that these sites may be cortical effector regions for thirst. A major sensory site for generating thirst is the lamina terminalis in the forebrain. Osmoreceptors within the organum vasculosum of the lamina terminalis and subfornical organ detect systemic hypertonicity. The subfornical organ mediates the dipsogenic actions of circulating angiotensin II and relaxin. Major integrative sites are the nucleus of the tractus solitarius, the lateral parabrachial nucleus, the midbrain raphé nuclei, the median preoptic nucleus, and the septum. Despite these advances, most of the neural pathways and neurochemical mechanisms subserving the genesis of thirst remain to be elucidated.
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Affiliation(s)
- Michael J McKinley
- Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Australia.
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Ciura S, Bourque CW. Transient receptor potential vanilloid 1 is required for intrinsic osmoreception in organum vasculosum lamina terminalis neurons and for normal thirst responses to systemic hyperosmolality. J Neurosci 2006; 26:9069-75. [PMID: 16943565 PMCID: PMC6675338 DOI: 10.1523/jneurosci.0877-06.2006] [Citation(s) in RCA: 194] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Recent studies have indicated that members of the transient receptor potential vanilloid (TRPV) family of cation channels are required for the generation of normal osmoregulatory responses, yet the mechanism of osmosensory transduction in primary osmoreceptor neurons of the CNS remains to be defined. Indeed, despite ample evidence suggesting that the organum vasculosum lamina terminalis (OVLT) serves as the primary locus of the brain for the detection of osmotic stimuli, evidence that neurons in the OVLT are intrinsically osmosensitive has remained elusive. Here we show that murine OVLT neurons are intrinsically sensitive to increases in the osmolality of the extracellular fluid. Hypertonic conditions provoked increases in membrane cation conductance that resulted in the generation of an inward current, depolarizing osmoreceptor potentials, and enhanced action potential discharge. Moreover, we found that this osmosensory signal transduction cascade was absent in OVLT neurons from TRPV1 knock-out (TRPV1-/-) mice and that responses of wild type (WT) OVLT neurons could be blocked by ruthenium red, an inhibitor of TRPV channels. Finally, TRPV1-/- mice showed significantly attenuated water intake in response to systemic hypertonicity compared with WT controls. These findings indicate that OVLT neurons act as primary osmoreceptors and that a product of the trpv1 gene is required for osmosensory transduction.
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Affiliation(s)
- Sorana Ciura
- Centre for Research in Neuroscience, Montreal General Hospital and McGill University, Montreal, Quebec, Canada, H3G 1A4
| | - Charles W. Bourque
- Centre for Research in Neuroscience, Montreal General Hospital and McGill University, Montreal, Quebec, Canada, H3G 1A4
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Kato K, Chu CP, Kannan H, Ishida Y, Nishimori T, Nose H. Regional differences in the expression of Fos-like immunoreactivity after central salt loading in conscious rats: modulation by endogenous vasopressin and role of the area postrema. Brain Res 2006; 1022:182-94. [PMID: 15353228 DOI: 10.1016/j.brainres.2004.02.082] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/05/2004] [Indexed: 11/19/2022]
Abstract
In this study, we examined the quantitative relationship between centrally administered hypertonic saline (HS) concentrations and the expression of Fos-like immunoreactivity (FLI) in brain regions involved in the homeostasis of body fluids. The regions examined were the organum vasculosum laminae terminalis (OVLT), the median preoptic nucleus (MnPO), the subfornical organ (SFO), the paraventricular nucleus (PVN), the supraoptic nucleus of the hypothalamus, the nucleus of the solitary tract (NTS), and the area postrema (AP). The experiments were performed in conscious rats with attention to the actual changes in central [Na(+)]. Hypertonic saline (0.3, 0.67, or 1.0 M) was delivered at 1 microl/min for 20 min. The changes in cerebrospinal fluid [Na(+)] during i.c.v. administration of 0.3 M hypertonic saline were compatible with those expected for thermal dehydration. FLI increased in a dose-dependent manner in the dorsomedial cap of the PVN and NTS. Although the pressor responses during central salt loading were not significantly affected by pretreatment with the peripheral vasopressin V(1) receptor antagonist OPC-21268, FLI expression in the PVN was significantly augmented. In addition, in AP-lesioned rats, FLI expression in the lateral magnocellular part of the PVN and NTS was significantly enhanced after central salt loading. These results suggest that the peripheral vasopressin system participates in negative feedback to modulate neuronal activities in the PVN, probably through the AP or direct action at the PVN in response to central osmotic and/or Na(+) stimulation.
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Affiliation(s)
- Kazuo Kato
- Department of Physiology, Miyazaki Medical College, 5200 Kihara, Kiyotake-cho, Miyazaki-gun, Miyazaki 889-1692, Japan
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Cottrell GT, Ferguson AV. Sensory circumventricular organs: central roles in integrated autonomic regulation. ACTA ACUST UNITED AC 2004; 117:11-23. [PMID: 14687696 DOI: 10.1016/j.regpep.2003.09.004] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Circumventricular organs (CVO) play a critical role as transducers of information between the blood, neurons and the cerebral spinal fluid (CSF). They permit both the release and sensing of hormones without disrupting the blood-brain barrier (BBB) and as a consequence of such abilities the CVOs are now well established to have essential regulatory actions in diverse physiological functions. The sensory CVOs are essential signal transducers located at the blood-brain interface regulating autonomic function. They have a proven role in the control of cardiovascular function and body fluid regulation, and have significant involvement in central immune response, feeding behavior and reproduction, the extent of which is still to be determined. This review will attempt to summarize the research on these topics to date. The complexities associated with sensory CVO exploration are intense, but should continue to result in valuable contributions to our understanding of brain function.
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Affiliation(s)
- G Trevor Cottrell
- Department of Physiology, Queen's University, Botterell Hall, 4th Floor, Kingston, ON, Canada K7L 3N6
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Trudel E, Bourque CW. A rat brain slice preserving synaptic connections between neurons of the suprachiasmatic nucleus, organum vasculosum lamina terminalis and supraoptic nucleus. J Neurosci Methods 2003; 128:67-77. [PMID: 12948549 DOI: 10.1016/s0165-0270(03)00149-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The organum vasculosum lamina terminalis (OVLT), the suprachiasmatic nucleus (SCN) and the supraoptic nucleus (SON) are three hypothalamic structures involved in the osmotic and circadian control of neurohypophysial secretion. Recent experiments have suggested that interactions between osmotic and circadian factors may be important for homeostasis. The existence of an in vitro slice preparation retaining these nuclei and their interconnections would therefore be useful for the analysis of synaptic interactions. In the rat, the OVLT, SCN and SON are found at increasingly ventral and lateral positions along the rostro-caudal axis, such that conventional 400 microm slices taken in the pure coronal or horizontal planes do not retain all three nuclei. Here we show that horizontal slices cut at angles of 38-42 degrees relative to the dorsal surface of the cortex retain large fractions of the three nuclei. Intracellular recordings revealed membrane properties consistent with those previously published for OVLT, SCN and SON neurons. Moreover, antidromic and synaptic responses evoked by electrical stimulation revealed that extensive axonal projections are retained between these nuclei. Finally, chemical and osmotic stimulation of the OVLT exerted powerful influences on the rate of spontaneous synaptic events in SON neurons. We therefore conclude that angled horizontal hypothalamic slices represent a useful preparation for the analysis of physiological interactions between the OVLT, SCN and SON.
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Affiliation(s)
- Eric Trudel
- Centre for Research in Neuroscience, Montreal General Hospital and McGill University, 1650 Cedar Avenue, Montreal, QC, Canada H3G 1A4
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Bourque CW, Richard D. Axonal projections from the organum vasculosum lamina terminalis to the supraoptic nucleus: functional analysis and presynaptic modulation. Clin Exp Pharmacol Physiol 2001; 28:570-4. [PMID: 11458884 DOI: 10.1046/j.1440-1681.2001.03488.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- C W Bourque
- Centre for Research in Neuroscience, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec H3G 1A4, Canada.
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Abstract
Na(v)2/NaG is a putative sodium channel, whose physiological role has long been an enigma. We generated Na(v)2 gene-deficient mice by inserting the lacZ gene. Analysis of the targeted mice allowed us to identify Na(v)2-producing cells by examining the lacZ expression. Besides in the lung, heart, dorsal root ganglia, and Schwann cells in the peripheral nervous system, Na(v)2 was expressed in neurons and ependymal cells in restricted areas of the CNS, particularly in the circumventricular organs, which are involved in body-fluid homeostasis. Under water-depleted conditions, c-fos expression was markedly elevated in neurons in the subfornical organ and organum vasculosum laminae terminalis compared with wild-type animals, suggesting a hyperactive state in the Na(v)2-null mice. Moreover, the null mutants showed abnormal intakes of hypertonic saline under both water- and salt-depleted conditions. These findings suggest that the Na(v)2 channel plays an important role in the central sensing of body-fluid sodium level and regulation of salt intake behavior.
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