Ca2+ homeostasis, Ca2+ signalling and somatodendritic vasopressin release in adult rat supraoptic nucleus neurones

Multiple mechanisms that maintain Ca2+ homeostasis and provide for Ca2+ signalling operate in the somatas and neurohypophysial nerve terminals of supraoptic nucleus (SON) neurones Here we examined the Ca2+ clearance mechanisms of SON neurones from adult rats by monitoring the effects of the selective inhibition of different Ca2+ homeostatic molecules on cytosolic Ca2+ ([Ca2+](1)) transients in isolated SON neurones In addition we measured somatodendritic vasopressin (AVP) release from intact SON tissue in an attempt to correlate it with [Ca2+](1), 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 Ca2+-ATPase (PMCA) La3+ all significantly slowed down the recovery of depolarisation (50 mM KCl)-induced [Ca2+](1), transients The release of AVP was stimulated by 50 mM KCl and the decline in the peptide release was slowed by Ca2+ transport inhibitors In contrast to previous reports our results show that in the fully mature adult rats (i) all four Ca2+ homeostatic pathways the Na+/Ca2+ exchanger the endoplasmic reticulum Ca2+ pump the plasmalemmal Ca2+ pump and mitochondria are complementary in actively clearing Ca2+ from SON neurones (ii) somatodendritic AVP release closely correlates with intracellular [Ca2+](1), dynamics (iii) there is (are) Ca2+ clearance mechanism(s) distinct from the four outlined above and (iv) Ca2+ homeostatic systems in the somatas of SON neurones differ from those expressed in their terminals (C) 2010 Elsevier Ltd All rights reserved