Ca(2+) homeostasis, Ca(2+) signalling and somatodendritic vasopressin release in adult rat supraoptic nucleus neurones |
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Authors: | Komori Yoko Tanaka Megumi Kuba Motoko Ishii Masahiro Abe Maiko Kitamura Naoki Verkhratsky Alexei Shibuya Izumi Dayanithi Govindan |
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Affiliation: | a Department of Veterinary Physiology, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan;b University of Occupational and Environmental Health School of Medicine, Kitakyushu 807-8555, Japan;c Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic v.v.i., Videnska 1083, 142 20 Prague 4, Czech Republic;d Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester M13 9PT, UK |
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Abstract: | Multiple mechanisms that maintain Ca(2+) homeostasis and provide for Ca(2+) signalling operate in the somatas and neurohypophysial nerve terminals of supraoptic nucleus (SON) neurones. Here, we examined the Ca(2+) clearance mechanisms of SON neurones from adult rats by monitoring the effects of the selective inhibition of different Ca(2+) homeostatic molecules on cytosolic Ca(2+) ([Ca(2+)](i)) transients in isolated SON neurones. In addition, we measured somatodendritic vasopressin (AVP) release from intact SON tissue in an attempt to correlate it with [Ca(2+)](i) dynamics. When bathing the cells in a Na(+)-free extracellular solution, thapsigargin, cyclopiazonic acid (CPA), carbonyl cyanide 3-chlorophenylhydrazone (CCCP), and the inhibitor of plasma membrane Ca(2+)-ATPase (PMCA), La(3+), all significantly slowed down the recovery of depolarisation (50 mM KCl)-induced [Ca(2+)](i) transients. The release of AVP was stimulated by 50 mM KCl, and the decline in the peptide release was slowed by Ca(2+) transport inhibitors. In contrast to previous reports, our results show that in the fully mature adult rats: (i) all four Ca(2+) homeostatic pathways, the Na(+)/Ca(2+) exchanger, the endoplasmic reticulum Ca(2+) pump, the plasmalemmal Ca(2+) pump and mitochondria, are complementary in actively clearing Ca(2+) from SON neurones; (ii) somatodendritic AVP release closely correlates with intracellular [Ca(2+)](i) dynamics; (iii) there is (are) Ca(2+) clearance mechanism(s) distinct from the four outlined above; and (iv) Ca(2+) homeostatic systems in the somatas of SON neurones differ from those expressed in their terminals. |
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Keywords: | Hypothalamus Cell bodies Nerve terminals Neuropeptides Ca2+ signalling Ca2+ clearance Ca2+ stores Mitochondria Na+/Ca2+ exchangers Plasma membrane Endoplasmic reticulum Calcium pumps Transgenic rats Stimulus-secretion coupling |
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