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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Zaelzer C, Gizowski C, Salmon CK, Murai KK, Bourque CW. Detection of activity-dependent vasopressin release from neuronal dendrites and axon terminals using sniffer cells. J Neurophysiol 2018; 120:1386-1396. [PMID: 29975164 DOI: 10.1152/jn.00467.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Our understanding of neuropeptide function within neural networks would be improved by methods allowing dynamic detection of peptide release in living tissue. We examined the usefulness of sniffer cells as biosensors to detect endogenous vasopressin (VP) release in rat hypothalamic slices and from isolated neurohypophyses. Human embryonic kidney cells were transfected to express the human V1a VP receptor (V1aR) and the genetically encoded calcium indicator GCaMP6m. The V1aR couples to Gq11, thus VP binding to this receptor causes an increase in intracellular [Ca2+] that can be detected by a rise in GCaMP6 fluorescence. Dose-response analysis showed that VP sniffer cells report ambient VP levels >10 pM (EC50 = 2.6 nM), and this effect could be inhibited by the V1aR antagonist SR 49059. When placed over a coverslip coated with sniffer cells, electrical stimulation of the neurohypophysis provoked a reversible, reproducible, and dose-dependent increase in VP release using as few as 60 pulses delivered at 3 Hz. Suspended sniffer cells gently plated over a slice adhered to the preparation and allowed visualization of VP release in discrete regions. Electrical stimulation of VP neurons in the suprachiasmatic nucleus caused significant local release as well as VP secretion in distant target sites. Finally, action potentials evoked in a single magnocellular neurosecretory cell in the supraoptic nucleus provoked significant VP release from the somatodendritic compartment of the neuron. These results indicate that sniffer cells can be used for the study of VP secretion from various compartments of neurons in living tissue. NEW & NOTEWORTHY The specific functional roles of neuropeptides in neuronal networks are poorly understood due to the absence of methods allowing their real-time detection in living tissue. Here, we show that cultured "sniffer cells" can be engineered to detect endogenous release of vasopressin as an increase in fluorescence.
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Affiliation(s)
- Cristian Zaelzer
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre , Montréal, Québec , Canada
| | - Claire Gizowski
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre , Montréal, Québec , Canada
| | - Christopher K Salmon
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre , Montréal, Québec , Canada
| | - Keith K Murai
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre , Montréal, Québec , Canada
| | - Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre , Montréal, Québec , Canada
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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: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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Farmer WT, Abrahamsson T, Chierzi S, Lui C, Zaelzer C, Jones EV, Bally BP, Chen GG, Théroux JF, Peng J, Bourque CW, Charron F, Ernst C, Sjöström PJ, Murai KK. Neurons diversify astrocytes in the adult brain through sonic hedgehog signaling. Science 2016; 351:849-54. [PMID: 26912893 DOI: 10.1126/science.aab3103] [Citation(s) in RCA: 182] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Astrocytes are specialized and heterogeneous cells that contribute to central nervous system function and homeostasis. However, the mechanisms that create and maintain differences among astrocytes and allow them to fulfill particular physiological roles remain poorly defined. We reveal that neurons actively determine the features of astrocytes in the healthy adult brain and define a role for neuron-derived sonic hedgehog (Shh) in regulating the molecular and functional profile of astrocytes. Thus, the molecular and physiological program of astrocytes is not hardwired during development but, rather, depends on cues from neurons that drive and sustain their specialized properties.
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Affiliation(s)
- W Todd Farmer
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Therése Abrahamsson
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Sabrina Chierzi
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Christopher Lui
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Cristian Zaelzer
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Emma V Jones
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Blandine Ponroy Bally
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Gary G Chen
- Department of Psychiatry, McGill University, Montreal, Quebec, Canada. McGill Group for Suicide Studies, Douglas Hospital, Montreal, Quebec, Canada
| | - Jean-Francois Théroux
- Department of Psychiatry, McGill University, Montreal, Quebec, Canada. McGill Group for Suicide Studies, Douglas Hospital, Montreal, Quebec, Canada
| | - Jimmy Peng
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal, Department of Medicine, University of Montreal, Montreal, Quebec, Canada. Department of Biology, McGill University, Montreal, Quebec, Canada
| | - Charles W Bourque
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Frédéric Charron
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal, Department of Medicine, University of Montreal, Montreal, Quebec, Canada. Department of Biology, McGill University, Montreal, Quebec, Canada
| | - Carl Ernst
- Department of Psychiatry, McGill University, Montreal, Quebec, Canada. McGill Group for Suicide Studies, Douglas Hospital, Montreal, Quebec, Canada. Department of Human Genetics, McGill University, Montreal, Quebec, Canada. Douglas Hospital Research Institute, Verdun, Quebec, Canada
| | - P Jesper Sjöström
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Keith K Murai
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Abstract
The high conductance voltage- and Ca(2+)-activated K(+) channel is one of the most broadly expressed channels in mammals. This channel is named BK for 'big K' because of its single-channel conductance that can be as large as 250 pS in 100 mm symmetrical K(+). BK channels increase their activity by membrane depolarization or an increase in cytosolic Ca(2+). One of the key features that defines the behaviour of BK channels is that neither Ca(2+) nor voltage is strictly necessary for channel activation. This and several other observations led to the idea that both Ca(2+) and voltage increase the open probability by an allosteric mechanism. In this type of mechanism, the processes of voltage sensor displacement, Ca(2+) binding and pore opening are independent equilibria that interact allosterically with each other. These allosteric interactions in BK channels reside in the structural characteristics of the BK channel in the sense that voltage and Ca(2+) sensors and the pore need to be contained in different structures or 'modules'. Through electrophysiological, mutagenesis, biochemical and fluorescence studies these modules have been identified and, more important, some of the interactions between them have been unveiled. In this review, we have covered the main advances achieved during the last few years in the elucidation of the structure of the BK channel and how this is related with its function as an allosteric protein.
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Affiliation(s)
- Ramon Latorre
- Universidad de Valparaiso, Centro de Neurociencia, Gran Bretana 1111, Playa Ancha, Valparaiso, V 2340000, Chile.
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