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Li D, Liu H, Wang H, Jia S, Wang X, Ling S, Chen G, Liu X, Wang YF. Astrocytic Hydrogen Sulfide Regulates Supraoptic Cellular Activity in the Adaptive Response of Lactating Rats to Chronic Social Stress. ASN Neuro 2021; 13:17590914211043087. [PMID: 34579557 PMCID: PMC8642056 DOI: 10.1177/17590914211043087] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Maternal social stress among breastfeeding women can be adapted in chronic process.
However, neuroendocrine mechanisms underlying such adaptation remain to be identified.
Here, we report the effects of 2 hr/day unfamiliar male rat invasion (UMI) stress on
maternal behaviors in lactating rats during postpartum day 8 (UMI8) to postpartum day 12
(UMI12). Rat dams at UMI8 presented signs of maternal anxiety, depression, and attacks
toward male intruder. These changes partially reversed at UMI12 except the sign of
anxiety. In the supraoptic nucleus (SON), UMI12 but not UMI8 significantly increased the
expression of c-Fos and phosphorylated extracellular signal-regulated protein kinase 1/2.
At UMI8 but not UMI12, length of glial fibrillary acidic protein (GFAP, astrocytic
cytoskeletal element) filaments around oxytocin (OT) neurons was significantly longer than
that of their controls; the amount of GFAP fragments at UMI12 was significantly less than
that at UMI8. Expression of cystathionine β-synthase (CBS, enzyme for H2S
synthesis) at UMI12 was significantly higher than that at UMI8. CBS expression did not
change significantly in the somatic zone of the SON but decreased significantly at the
ventral glia lamina at UMI8. In brain slices of the SON, aminooxyacetate (a CBS blocker)
significantly increased the expression of GFAP proteins that were molecularly associated
with CBS. Aminooxyacetate also reduced the firing rate of OT neurons whereas
Na2S, a donor of H2S, increased it. The adaptation during chronic
social stress is possibly attributable to the increased production of H2S by
astrocytes and the subsequent retraction of astrocytic processes around OT neurons.
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Affiliation(s)
- Dongyang Li
- Department of Physiology, 12455Hainan Medical University, Haikou, China.,Department of Physiology, School of Basic Medical Sciences, 34707Harbin Medical University, Harbin, China
| | - Haitao Liu
- Department of Physiology, School of Basic Medical Sciences, 34707Harbin Medical University, Harbin, China
| | - Hongyang Wang
- Department of Physiology, School of Basic Medical Sciences, 34707Harbin Medical University, Harbin, China
| | - Shuwei Jia
- Department of Physiology, School of Basic Medical Sciences, 34707Harbin Medical University, Harbin, China
| | - Xiaoran Wang
- Department of Physiology, School of Basic Medical Sciences, 34707Harbin Medical University, Harbin, China
| | - Shuo Ling
- Department of Physiology, School of Basic Medical Sciences, 34707Harbin Medical University, Harbin, China
| | - Guichuan Chen
- Department of Physiology, School of Basic Medical Sciences, 34707Harbin Medical University, Harbin, China
| | - Xiaoyu Liu
- Department of Physiology, School of Basic Medical Sciences, 34707Harbin Medical University, Harbin, China
| | - Yu-Feng Wang
- Department of Physiology, School of Basic Medical Sciences, 34707Harbin Medical University, Harbin, China
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Brown CH, Ludwig M, Tasker JG, Stern JE. Somato-dendritic vasopressin and oxytocin secretion in endocrine and autonomic regulation. J Neuroendocrinol 2020; 32:e12856. [PMID: 32406599 PMCID: PMC9134751 DOI: 10.1111/jne.12856] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 03/29/2020] [Accepted: 04/11/2020] [Indexed: 12/29/2022]
Abstract
Somato-dendritic secretion was first demonstrated over 30 years ago. However, although its existence has become widely accepted, the function of somato-dendritic secretion is still not completely understood. Hypothalamic magnocellular neurosecretory cells were among the first neuronal phenotypes in which somato-dendritic secretion was demonstrated and are among the neurones for which the functions of somato-dendritic secretion are best characterised. These neurones secrete the neuropeptides, vasopressin and oxytocin, in an orthograde manner from their axons in the posterior pituitary gland into the blood circulation to regulate body fluid balance and reproductive physiology. Retrograde somato-dendritic secretion of vasopressin and oxytocin modulates the activity of the neurones from which they are secreted, as well as the activity of neighbouring populations of neurones, to provide intra- and inter-population signals that coordinate the endocrine and autonomic responses for the control of peripheral physiology. Somato-dendritic vasopressin and oxytocin have also been proposed to act as hormone-like signals in the brain. There is some evidence that somato-dendritic secretion from magnocellular neurosecretory cells modulates the activity of neurones beyond their local environment where there are no vasopressin- or oxytocin-containing axons but, to date, there is no conclusive evidence for, or against, hormone-like signalling throughout the brain, although it is difficult to imagine that the levels of vasopressin found throughout the brain could be underpinned by release from relatively sparse axon terminal fields. The generation of data to resolve this issue remains a priority for the field.
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Affiliation(s)
- Colin H. Brown
- Department of Physiology, Brain Health Research Centre, Centre for Neuroendocrinology, University of Otago, Dunedin, New Zealand
| | - Mike Ludwig
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
- Department of Immunology, Centre for Neuroendocrinology, University of Pretoria, Pretoria, South Africa
| | - Jeffrey G. Tasker
- Department of Cell and Molecular Biology, Brain Institute, Tulane University, New Orleans, LA, USA
| | - Javier E. Stern
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
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Lemos JR, Custer EE, Ortiz-Miranda S. Purinergic receptor types in the hypothalamic-neurohypophysial system. J Neuroendocrinol 2018; 30:10.1111/jne.12588. [PMID: 29512852 PMCID: PMC6128781 DOI: 10.1111/jne.12588] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 02/28/2018] [Indexed: 11/27/2022]
Abstract
Many different types of purinergic receptors are present in the Hypothalamic-Neurohypophysial System (HNS), which synthesizes and releases vasopressin and oxytocin. The specific location of purinergic receptor subtypes has important functional repercussions for neuronal activity and synaptic output. Yet, until the advent of receptor KOs, this had been hindered by the low selectivity of the available pharmacological tools. The HNS offers an excellent opportunity to differentiate the functional properties of these purinergic receptors in cell bodies vs. terminals of the same physiological system. P2X2, P2X3, P2X4 and P2X7 receptors are present in vasopressin terminals while oxytocin terminals exclusively express the P2X7 subtype. The latter is not functional in the cell bodies of the HNS. These purinergic receptor subtypes are permeable to sodium vs. calcium in varying amounts and this could play an important role in the release of vasopressin vs. oxytocin during bursting activity. Endogenous ATP and its metabolite, adenosine, have autocrine and paracrine modulatory effects on the release of these neuropeptides during physiological stimulation. Finally, we hypothesize that during such action potential bursts, ATP potentiates the release of vasopressin but not of oxytocin, and that adenosine, via A1 receptors, inhibits the release of both neuropeptides. This article is protected by copyright. All rights reserved.
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Affiliation(s)
| | | | - Sonia Ortiz-Miranda
- Neurobiology Depts. & Prog. Neurosci., Univ. Mass. Med. School, Worcester, MA 01605
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Clasadonte J, Prevot V. The special relationship: glia-neuron interactions in the neuroendocrine hypothalamus. Nat Rev Endocrinol 2018; 14:25-44. [PMID: 29076504 DOI: 10.1038/nrendo.2017.124] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Natural fluctuations in physiological conditions require adaptive responses involving rapid and reversible structural and functional changes in the hypothalamic neuroendocrine circuits that control homeostasis. Here, we discuss the data that implicate hypothalamic glia in the control of hypothalamic neuroendocrine circuits, specifically neuron-glia interactions in the regulation of neurosecretion as well as neuronal excitability. Mechanistically, the morphological plasticity displayed by distal processes of astrocytes, pituicytes and tanycytes modifies the geometry and diffusion properties of the extracellular space. These changes alter the relationship between glial cells of the hypothalamus and adjacent neuronal elements, especially at specialized intersections such as synapses and neurohaemal junctions. The structural alterations in turn lead to functional plasticity that alters the release and spread of neurotransmitters, neuromodulators and gliotransmitters, as well as the activity of discrete glial signalling pathways that mediate feedback by peripheral signals to the hypothalamus. An understanding of the contributions of these and other non-neuronal cell types to hypothalamic neuroendocrine function is thus critical both to understand physiological processes such as puberty, the maintenance of bodily homeostasis and ageing and to develop novel therapeutic strategies for dysfunctions of these processes, such as infertility and metabolic disorders.
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Affiliation(s)
- Jerome Clasadonte
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Centre, U1172, Bâtiment Biserte, 1 Place de Verdun, 59045, Lille, Cedex, France
- University of Lille, FHU 1000 days for Health, School of Medicine, Lille 59000, France
| | - Vincent Prevot
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Centre, U1172, Bâtiment Biserte, 1 Place de Verdun, 59045, Lille, Cedex, France
- University of Lille, FHU 1000 days for Health, School of Medicine, Lille 59000, France
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5
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Abstract
The posterior pituitary gland secretes oxytocin and vasopressin (the antidiuretic hormone) into the blood system. Oxytocin is required for normal delivery of the young and for delivery of milk to the young during lactation. Vasopressin increases water reabsorption in the kidney to maintain body fluid balance and causes vasoconstriction to increase blood pressure. Oxytocin and vasopressin secretion occurs from the axon terminals of magnocellular neurons whose cell bodies are principally found in the hypothalamic supraoptic nucleus and paraventricular nucleus. The physiological functions of oxytocin and vasopressin depend on their secretion, which is principally determined by the pattern of action potentials initiated at the cell bodies. Appropriate secretion of oxytocin and vasopressin to meet the challenges of changing physiological conditions relies mainly on integration of afferent information on reproductive, osmotic, and cardiovascular status with local regulation of magnocellular neurons by glia as well as intrinsic regulation by the magnocellular neurons themselves. This review focuses on the control of magnocellular neuron activity with a particular emphasis on their regulation by reproductive function, body fluid balance, and cardiovascular status. © 2016 American Physiological Society. Compr Physiol 6:1701-1741, 2016.
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Affiliation(s)
- Colin H Brown
- Brain Health Research Centre, Centre for Neuroendocrinology and Department of Physiology, University of Otago, Dunedin, New Zealand
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Brown CH, Bains JS, Ludwig M, Stern JE. Physiological regulation of magnocellular neurosecretory cell activity: integration of intrinsic, local and afferent mechanisms. J Neuroendocrinol 2013; 25:678-710. [PMID: 23701531 PMCID: PMC3852704 DOI: 10.1111/jne.12051] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Revised: 05/08/2013] [Accepted: 05/20/2013] [Indexed: 01/12/2023]
Abstract
The hypothalamic supraoptic and paraventricular nuclei contain magnocellular neurosecretory cells (MNCs) that project to the posterior pituitary gland where they secrete either oxytocin or vasopressin (the antidiuretic hormone) into the circulation. Oxytocin is important for delivery at birth and is essential for milk ejection during suckling. Vasopressin primarily promotes water reabsorption in the kidney to maintain body fluid balance, but also increases vasoconstriction. The profile of oxytocin and vasopressin secretion is principally determined by the pattern of action potentials initiated at the cell bodies. Although it has long been known that the activity of MNCs depends upon afferent inputs that relay information on reproductive, osmotic and cardiovascular status, it has recently become clear that activity depends critically on local regulation by glial cells, as well as intrinsic regulation by the MNCs themselves. Here, we provide an overview of recent advances in our understanding of how intrinsic and local extrinsic mechanisms integrate with afferent inputs to generate appropriate physiological regulation of oxytocin and vasopressin MNC activity.
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Affiliation(s)
- C H Brown
- Department of Physiology and Centre for Neuroendocrinology, University of Otago, Dunedin, New Zealand.
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7
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Zanos P, Wright SR, Georgiou P, Yoo JH, Ledent C, Hourani SM, Kitchen I, Winsky-Sommerer R, Bailey A. Chronic methamphetamine treatment induces oxytocin receptor up-regulation in the amygdala and hypothalamus via an adenosine A2A receptor-independent mechanism. Pharmacol Biochem Behav 2013; 119:72-9. [PMID: 23680573 DOI: 10.1016/j.pbb.2013.05.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 04/30/2013] [Accepted: 05/03/2013] [Indexed: 12/12/2022]
Abstract
There is mounting evidence that the neuropeptide oxytocin is a possible candidate for the treatment of drug addiction. Oxytocin was shown to reduce methamphetamine self-administration, conditioned place-preference, hyperactivity and reinstatement in rodents, highlighting its potential for the management of methamphetamine addiction. Thus, we hypothesised that the central endogenous oxytocinergic system is dysregulated following chronic methamphetamine administration. We tested this hypothesis by examining the effect of chronic methamphetamine administration on oxytocin receptor density in mice brains with the use of quantitative receptor autoradiographic binding. Saline (4ml/kg/day, i.p.) or methamphetamine (1mg/kg/day, i.p.) was administered daily for 10 days to male, CD1 mice. Quantitative autoradiographic mapping of oxytocin receptors was carried out with the use of [(125)I]-vasotocin in brain sections of these animals. Chronic methamphetamine administration induced a region specific upregulation of oxytocin receptor density in the amygdala and hypothalamus, but not in the nucleus accumbens and caudate putamen. As there is evidence suggesting an involvement of central adenosine A2A receptors on central endogenous oxytocinergic function, we investigated whether these methamphetamine-induced oxytocinergic neuroadaptations are mediated via an A2A receptor-dependent mechanism. To test this hypothesis, autoradiographic oxytocin receptor binding was carried out in brain sections of male CD1 mice lacking A2A receptors which were chronically treated with methamphetamine (1mg/kg/day, i.p. for 10 days) or saline. Similar to wild-type animals, chronic methamphetamine administration induced a region-specific upregulation of oxytocin receptor binding in the amygdala and hypothalamus of A2A receptor knockout mice and no genotype effect was observed. These results indicate that chronic methamphetamine use can induce profound neuroadaptations of the oxytocinergic receptor system in brain regions associated with stress, emotionality and social bonding and that these neuroadaptations are independent on the presence of A2A receptors. These results may at least partly explain some of the behavioural consequences of chronic methamphetamine use.
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Affiliation(s)
- Panos Zanos
- Sleep, Chronobiology & Addiction Group, Department of Biochemistry & Physiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, Surrey, UK
| | - Sherie R Wright
- Sleep, Chronobiology & Addiction Group, Department of Biochemistry & Physiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, Surrey, UK
| | - Polymnia Georgiou
- Sleep, Chronobiology & Addiction Group, Department of Biochemistry & Physiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, Surrey, UK
| | - Ji Hoon Yoo
- Sleep, Chronobiology & Addiction Group, Department of Biochemistry & Physiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, Surrey, UK
| | - Catherine Ledent
- Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Université Libre de Bruxelles, B-1070, Belgium
| | - Susanna M Hourani
- Sleep, Chronobiology & Addiction Group, Department of Biochemistry & Physiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, Surrey, UK
| | - Ian Kitchen
- Sleep, Chronobiology & Addiction Group, Department of Biochemistry & Physiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, Surrey, UK
| | - Raphaelle Winsky-Sommerer
- Sleep, Chronobiology & Addiction Group, Department of Biochemistry & Physiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, Surrey, UK
| | - Alexis Bailey
- Sleep, Chronobiology & Addiction Group, Department of Biochemistry & Physiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, Surrey, UK.
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Li DP, Chen SR, Pan HL. Adenosine inhibits paraventricular pre-sympathetic neurons through ATP-dependent potassium channels. J Neurochem 2010; 113:530-42. [PMID: 20096091 DOI: 10.1111/j.1471-4159.2010.06618.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Adenosine produces cardiovascular depressor effects in various brain regions. However, the cellular mechanisms underlying these effects remain unclear. The pre-sympathetic neurons in the hypothalamic paraventricular nucleus (PVN) play an important role in regulating arterial blood pressure and sympathetic outflow through projections to the spinal cord and brainstem. In this study, we performed whole-cell patch-clamp recordings on retrogradely labeled PVN neurons projecting to the intermediolateral cell column of the spinal cord in rats. Adenosine (10-100 microM) decreased the firing activity in a concentration-dependent manner, with a marked hyperpolarization in 12 of 26 neurons tested. Blockade of A(1) receptors with the adenosine A(1) receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine or intracellular dialysis of guanosine 5'-O-(2-thodiphosphate) eliminated the inhibitory effect of adenosine on labeled PVN neurons. Immunocytochemical labeling revealed that A(1) receptors were expressed on spinally projecting PVN neurons. Also, blocking ATP-dependent K(+) (K(ATP)) channels with 100 microM glibenclamide or 200 microM tolbutamide, but not the G protein-coupled inwardly rectifying K(+) channels blocker tertiapin-Q, abolished the inhibitory effect of adenosine on the firing activity of PVN neurons. Furthermore, glibenclamide or tolbutamide significantly decreased the adenosine-induced outward currents in labeled neurons. The reversal potential of adenosine-induced currents was close to the K(+) equilibrium potential. In addition, adenosine decreased the frequency of both spontaneous and miniature glutamatergic excitatory post-synaptic currents and GABAergic inhibitory post-synaptic currents in labeled neurons, and these effects were also blocked by 8-cyclopentyl-1,3-dipropylxanthine. Collectively, our findings suggest that adenosine inhibits the excitability of PVN pre-sympathetic neurons through A(1) receptor-mediated opening of K(ATP) channels.
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Affiliation(s)
- De-Pei Li
- Department of Critical Care, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
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Wang YF, Hamilton K. Chronic vs. acute interactions between supraoptic oxytocin neurons and astrocytes during lactation: role of glial fibrillary acidic protein plasticity. ScientificWorldJournal 2009; 9:1308-20. [PMID: 19936568 PMCID: PMC3548440 DOI: 10.1100/tsw.2009.148] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
In this article, we review studies of astrocytic-neuronal interactions and their effects on the activity of oxytocin (OXT) neurons within the magnocellular hypothalamo-neurohypophysial system. Previous work over several decades has shown that withdrawal of astrocyte processes increases OXT neuron excitability in the hypothalamic supraoptic nucleus (SON) during lactation. However, chronically disabling astrocyte withdrawal does not significantly affect the functioning of OXT neurons during suckling. Nevertheless, acute changes in a cytoskeletal element of astrocytes, glial fibrillary acidic protein (GFAP), occur in concert with changes in OXT neuronal activity during suckling. Here, we compare these changes in GFAP and related proteins with chronic changes that persist throughout lactation. During lactation, a decrease in GFAP levels accompanies retraction of astrocyte processes surrounding OXT neurons in the SON, resulting from high extracellular levels of OXT. During the initial stage of suckling, acute increases in OXT levels further strengthen this GFAP reduction and facilitate the retraction of astrocyte processes. This change, in turn, facilitates burst discharges of OXT neurons and leads to a transient increase in excitatory neurochemicals. This transient neurochemical surge acts to reverse GFAP expression and results in postburst inhibition of OXT neurons. The acute changes in astrocyte GFAP levels seen during suckling likely recur periodically, accompanied by rhythmic changes in glutamate metabolism, water transport, gliotransmitter release, and spatial relationships between astrocytes and OXT neurons. In the neurohypophysis, astrocyte retraction and reversal with accompanying GFAP plasticity also likely occur during lactation and suckling, which facilitates OXT release coordinated with its action in the SON. These studies of the dynamic interactions that occur between astrocytes and OXT neurons mediated by GFAP extend our understanding of astrocyte functions within the central nervous system.
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Affiliation(s)
- Yu-Feng Wang
- Department of Cellular Biology and Anatomy, Louisiana State University Health Sciences Center, Shreveport, USA.
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Ruan M, Brown CH. Feedback inhibition of action potential discharge by endogenous adenosine enhancement of the medium afterhyperpolarization. J Physiol 2009; 587:1043-56. [PMID: 19139041 DOI: 10.1113/jphysiol.2008.167239] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Phasic activity in supraoptic nucleus vasopressin neurones is characterized by alternating periods of activity (bursts) and silence. During bursts, activation of a medium afterhyperpolarization induces spike frequency adaptation. Antagonism of A1 adenosine receptors within the supraoptic nucleus decreases spike frequency adaptation and prolongs phasic bursts in vivo, indicating that endogenous adenosine contributes to spike frequency adaptation. Here we used sharp electrode intracellular recordings from supraoptic nucleus neurones in hypothalamic explants to show that endogenous adenosine increases medium afterhyperpolarization amplitude to enhance spike frequency adaptation during phasic bursts. Superfusion of the A1 receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine (CPT, 10 microM) increased intraburst firing rate of phasic neurones (by 2.0 +/- 0.7 spikes s(-1), P = 0.03) and burst duration (by 141 +/- 113 s, P = 0.03). The CPT-induced increase in intraburst firing rate developed over the first few seconds of firing and persisted thereafter. In a separate series of experiments, CPT reduced the amplitude of the medium afterhyperpolarization evoked by a 1 s 20 Hz spike train (by 0.8 +/- 0.3 mV, P < 0.001) in supraoptic nucleus neurones; this inhibition was not prevented by 3 mM CsCl (0.8 +/- 0.1 mV decrease, P < 0.01) to block the afterdepolarization (which overlaps temporally with the medium afterhyperpolarization). In the presence of apamin to block the medium afterhyperpolarization, CPT did not alter afterdepolarization amplitude. Taken together, these data show that endogenous adenosine enhances medium afterhyperpolarization amplitude to contribute to spike frequency adaptation in phasic supraoptic nucleus neurones.
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Affiliation(s)
- Ming Ruan
- Centre for Neuroendocrinology and Department of Physiology, University of Otago, Dunedin 9054, New Zealand
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