The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform
Charles W. Bourque - One of the best experts on this subject based on the ideXlab platform.
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Cell-Specific Retrograde Signals Mediate Antiparallel Effects of Angiotensin II on Osmoreceptor Afferents to Vasopressin and Oxytocin Neurons
Cell reports, 2014Co-Authors: Tevye J. Stachniak, Eric Trudel, Charles W. BourqueAbstract:Homeostatic control of extracellular fluid osmolality in rats requires a parallel excitation of vasopressin (VP) and oxytocin (OT) neurosecretory neurons by Osmoreceptor afferents to regulate the amount of water and sodium in the urine under normal conditions. However, during decreased blood volume (hypovolemia), natriuresis is suppressed, whereas osmotically driven antidiuresis is enhanced to promote retention of isotonic fluid. Because Angiotensin II (Ang II) is released centrally to indicate hypovolemia, we hypothesized that Ang II can evoke a state-dependent switch in circuit function. Here, we show that Ang II, a neuropeptide released centrally during hypovolemia, suppresses Osmoreceptor-mediated synaptic excitation of OT neurons while potentiating excitation of VP neurons. Ang II does this by inducing cell-autonomous release of nitric oxide by VP neurons and endocannabinoids by OT neurons to respectively enhance and reduce glutamate release by Osmoreceptor afferents. These findings indicate that peptide modulators such as Ang II can regulate synaptic communication to achieve a state-dependent and target-specific modulation of circuit activity.
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TRPV1Δ1-283: A Candidate Osmoreceptor Channel
Biophysical Journal, 2011Co-Authors: Cristian Zaelzer, Sorana Ciura, Pierce Hua, Maria Prager-khoutorsky, Suk Hee Lee, Wolfgang Liedtke, Charles W. BourqueAbstract:Mammalian osmosensory neurons exposed to hypertonicity display a shrinking-induced increase in non-selective cation conductance. That causes membrane depolarization and excitation triggering homeostatic responses such as thirst and antidiuretic hormone release. The molecular identity of the Osmoreceptor channel is not known, but appears to involve a capsaicin-insensitive N-terminal variant of the transient receptor potential vanilloid type 1 (TRPV1) channel (Ciura and Bourque, 2006; Sharif-Naeini et al., 2006). Here, we report that heterologous expression of TRPV1 variant Δ1-283, which lacks exons 1-5, confers osmosensory characteristics similar to those found in native osmosensory neurons. Whole cell voltage clamp recordings were used to examine the effects of hyperosmolality (+mannitol) on human embryonic kidney (HEK293) cells expressing Δ1-283 TRPV1, GFP or wild type TRPV1. Dynamic imaging confirmed that all HEK cells exposed to hypertonicity underwent visible shrinking. However in contrast to GFP (n = 10) and TRPV1 (n = 32) transfected cells, which were unresponsive, ∼41% (84/206) of cells transfected with Δ1-283 TRPV1 showed a progressive and sustained increase in non-selective cation current and membrane conductance when exposed to a hyperosmotic stimuli lasting 2-5 minutes. The effects of osmolality were dose-dependent (+5 to +80 mosmol/kg), mimicked by suction induced cell shrinking (n=6), and were abolished by Ruthenium Red. Moreover, addition of capsaicin caused robust responses in cells expressing TRPV1, but had no effect on those expressing Δ1-283 TRPV1. Imaging experiments on cells loaded with Fura-2 revealed that ∼21% of the cells transfected with Δ1-283 TRPV1 display reversible increases in intracellular [Ca2+], whereas ∼17% shown an increase without reversion when exposed to a +40 mosmol/kg hyperosmotic stimulus. These results suggest Δ1-283 TRPV1 channels could mediate mechanically-induced increases in cation current associated with hypertonicity-induced shrinking in osmosensory neurons.
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Transient Receptor Potential Vanilloid 1 Is Required for Intrinsic Osmoreception in Organum Vasculosum Lamina Terminalis Neurons and for Normal Thirst Responses to Systemic Hyperosmolality
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2006Co-Authors: Sorana Ciura, Charles W. BourqueAbstract: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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COINCIDENT DETECTION OF CSF NA+ AND OSMOTIC PRESSURE IN OSMOREGULATORY NEURONS OF THE SUPRAOPTIC NUCLEUS
Neuron, 1999Co-Authors: Daniel L. Voisin, Yassar Chakfe, Charles W. BourqueAbstract:Behavioral and neuroendocrine responses underlying systemic osmoregulation are under the concerted control of centrally located Osmoreceptors and cerebrospinal fluid (CSF) Na+ concentration ([Na+]) detectors. Although the process underlying osmoreception is understood, the mechanism by which [Na+] is detected and integrated with cellular information derived from Osmoreceptors is unknown. Here, we show that shifts in extracellular [Na+] ([Na+]0) cause proportional changes in the relative Na+ permeability of mechanosensitive cation channels responsible for signal transduction in the osmosensory neurons of the supraoptic nucleus. This effect causes the generation of Na+ specific receptor potentials under isotonic conditions and modulates Osmoreceptor potentials and electrical responsiveness during osmotic perturbation. These results provide a cellular basis for Na+-sensing and for the coordinated detection of CSF [Na+] and osmolality in central osmoregulatory neurons.
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OsmoreceptorS IN THE CENTRAL NERVOUS SYSTEM
Annual review of physiology, 1997Co-Authors: Charles W. Bourque, Stéphane H. R. OlietAbstract:Osmoreceptors regulate sodium and water balance in a manner that maintains the osmotic pressure of the extracellular fluid (ECF) near an ideal set point. In rats, the concerted release of oxytocin and vasopressin, which is determined by the firing rate of magnocellular neurosecretory cells (MNCs), plays a key role in osmoregulation through the effects of natriuresis and diuresis. Changes in excitatory synaptic drive, derived from osmosensitive neurons in the organum vasculosum lamina terminalis (OVLT), combine with endogenously generated Osmoreceptor potentials to modulate the firing rate of MNCs. The cellular basis for Osmoreceptor potentials has been characterized using patch-clamp recordings and morphometric analysis in MNCs isolated from the supraoptic nucleus of the adult rat. In these cells, stretch-inactivated cationic channels transduce osmotically evoked changes in cell volume into functionally relevant changes in membrane potential. The experimental details of these mechanisms are reviewed in their physiological context.
Stéphane H. R. Oliet - One of the best experts on this subject based on the ideXlab platform.
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OsmoreceptorS IN THE CENTRAL NERVOUS SYSTEM
Annual review of physiology, 1997Co-Authors: Charles W. Bourque, Stéphane H. R. OlietAbstract:Osmoreceptors regulate sodium and water balance in a manner that maintains the osmotic pressure of the extracellular fluid (ECF) near an ideal set point. In rats, the concerted release of oxytocin and vasopressin, which is determined by the firing rate of magnocellular neurosecretory cells (MNCs), plays a key role in osmoregulation through the effects of natriuresis and diuresis. Changes in excitatory synaptic drive, derived from osmosensitive neurons in the organum vasculosum lamina terminalis (OVLT), combine with endogenously generated Osmoreceptor potentials to modulate the firing rate of MNCs. The cellular basis for Osmoreceptor potentials has been characterized using patch-clamp recordings and morphometric analysis in MNCs isolated from the supraoptic nucleus of the adult rat. In these cells, stretch-inactivated cationic channels transduce osmotically evoked changes in cell volume into functionally relevant changes in membrane potential. The experimental details of these mechanisms are reviewed in their physiological context.
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Gadolinium Uncouples Mechanical Detection and Osmoreceptor Potential in Supraoptic Neurons
Neuron, 1996Co-Authors: Stéphane H. R. Oliet, Charles W. BourqueAbstract:Stretch-sensitive ion channels are ubiquitous, yet evidence of their role in mechanotransduction remains scarce. The presence of stretch-inactivated cation channels in supraoptic neurons is consistent with the Osmoreceptor potentials regulating vasopressin release. However, whether osmosensitivity depends on mechanical gating and ion flux through stretch-inactivated channels is unknown. Here we report that changes in channel open probability associated either with modification of pipette pressure or with external osmolality selectivity result from variations in closed time. While channel mechanosensitivity and osmotically evoked changes in cell volume are not affected by gadolinium, similar concentrations of the lanthanide inhibit cation permeation through the single channels and macroscopic Osmoreceptor potentials. Mechanotransduction through stretch-inactivated channels is therefore necessary for osmoreception in supraoptic neurons.
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Osmoreception in magnocellular neurosecretory cells: from single channels to secretion
Trends in Neurosciences, 1994Co-Authors: Stéphane H. R. Oliet, Charles W. BourqueAbstract:Abstract Recognizing that osmotic pressure is a principal factor controlling antidiuresis, Verney introduced the term ‘Osmoreceptor' to designate the mysterious cerebral structures that regulate vasopressin release from the posterior pituitary. While hormone secretion from the neurohypophysis is influenced by synaptic inputs from other osmoresponsive neurons, magnocellular neurosecretory cells currently provide our most comprehensive model of signal detection in an Osmoreceptor.
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Osmoreceptors, osmoreception, and osmoregulation.
Frontiers in neuroendocrinology, 1994Co-Authors: Charles W. Bourque, Stéphane H. R. Oliet, Dominique RichardAbstract:Mammals have evolved sophisticated behavioral and physiological responses to oppose changes in the osmolality of their extracellular fluid. The behavioral approach consists of regulating the intake of salt and water through changes in sodium appetite and thirst. The physiological approach comprises adjustments of renal excretion of water and sodium which are achieved through changes in the release of antidiuretic and natriuretic hormones. Individually, these osmoregulatory responses are controlled by "Osmoreceptors": groups of specialized nerve cells capable of transducing changes in external osmotic pressure into meaningful electrical signals. Some of these sensors are located in the region of the hepatic portal vein, a strategic site allowing early detection of the osmotic impact of ingested foods and fluids. Changes in systemic osmolality, however, are detected centrally, within regions that include the medial preoptic area, the median preoptic nucleus, the organum vasculosum lamina terminalis (OVLT), the subfornical organ, and the supraoptic nucleus (SON). While studies have indicated that these central and peripheral Osmoreceptors participate in the control of osmoregulatory responses, little is known of the mechanisms by which this is achieved. One notable exception, however, consists of the osmotic control of electrical activity in SON neurons which, in the rat, contributes to the regulation of natriuresis and diuresis through effects on the secretion of oxytocin and vasopressin. Previous studies have shown that these cells are respectively excited and inhibited by hypertonic and hypotonic conditions. Experiments in vitro indicate that these responses result from both the endogenous osmosensitivity of these cells and changes in synaptic drive. Patch-clamp analysis has revealed that SON neurons are respectively depolarized and hyperpolarized by increases and decreases in external osmolality and that these intrinsic responses result from changes in the activity of mechanosensitive cationic channels. Moreover, intracellular recordings in hypothalamic explants have shown that changes in electrical activity are associated with proportional changes in the frequency of glutamatergic excitatory postsynaptic potentials derived from osmosensitive OVLT neurons. Both of these mechanisms, therefore, may participate in the osmotic regulation of neurohypophysial hormone release in situ.
Celia D. Sladek - One of the best experts on this subject based on the ideXlab platform.
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Role of non-NMDA receptors in vasopressin and oxytocin release from rat hypothalamo-neurohypophysial explants.
American journal of physiology. Regulatory integrative and comparative physiology, 2001Co-Authors: Delmore J. Morsette, Hanna E. Sidorowicz, Celia D. SladekAbstract:Glutamate is recognized as a prominent excitatory transmitter in the supraoptic nucleus (SON) and is involved in transmission of osmoregulatory information from the Osmoreceptors to the vasopressin...
Michael G. Ross - One of the best experts on this subject based on the ideXlab platform.
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Osmotic threshold and sensitivity for vasopressin release and Fos expression by hypertonic NaCl in ovine fetus
American journal of physiology. Endocrinology and metabolism, 2000Co-Authors: Calvario Glenda, Linda Day, Jiaming Yao, Michael G. RossAbstract:In adults, hyperosmolality stimulates central Osmoreceptors, resulting in arginine vasopressin (AVP) secretion. Near-term fetal sheep have also developed mechanisms to respond to intravascular hype...
Dominique Richard - One of the best experts on this subject based on the ideXlab platform.
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Osmoreceptors, osmoreception, and osmoregulation.
Frontiers in neuroendocrinology, 1994Co-Authors: Charles W. Bourque, Stéphane H. R. Oliet, Dominique RichardAbstract:Mammals have evolved sophisticated behavioral and physiological responses to oppose changes in the osmolality of their extracellular fluid. The behavioral approach consists of regulating the intake of salt and water through changes in sodium appetite and thirst. The physiological approach comprises adjustments of renal excretion of water and sodium which are achieved through changes in the release of antidiuretic and natriuretic hormones. Individually, these osmoregulatory responses are controlled by "Osmoreceptors": groups of specialized nerve cells capable of transducing changes in external osmotic pressure into meaningful electrical signals. Some of these sensors are located in the region of the hepatic portal vein, a strategic site allowing early detection of the osmotic impact of ingested foods and fluids. Changes in systemic osmolality, however, are detected centrally, within regions that include the medial preoptic area, the median preoptic nucleus, the organum vasculosum lamina terminalis (OVLT), the subfornical organ, and the supraoptic nucleus (SON). While studies have indicated that these central and peripheral Osmoreceptors participate in the control of osmoregulatory responses, little is known of the mechanisms by which this is achieved. One notable exception, however, consists of the osmotic control of electrical activity in SON neurons which, in the rat, contributes to the regulation of natriuresis and diuresis through effects on the secretion of oxytocin and vasopressin. Previous studies have shown that these cells are respectively excited and inhibited by hypertonic and hypotonic conditions. Experiments in vitro indicate that these responses result from both the endogenous osmosensitivity of these cells and changes in synaptic drive. Patch-clamp analysis has revealed that SON neurons are respectively depolarized and hyperpolarized by increases and decreases in external osmolality and that these intrinsic responses result from changes in the activity of mechanosensitive cationic channels. Moreover, intracellular recordings in hypothalamic explants have shown that changes in electrical activity are associated with proportional changes in the frequency of glutamatergic excitatory postsynaptic potentials derived from osmosensitive OVLT neurons. Both of these mechanisms, therefore, may participate in the osmotic regulation of neurohypophysial hormone release in situ.