Ca(2+) homeostasis, Ca(2+) signalling and somatodendritic vasopressin release in adult rat supraoptic nucleus neurones.
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.
University of Occupational and Environmental Health School of Medicine, Kitakyushu 807-8555, Japan.
Yoko
Y
Komori
Megumi
M
Tanaka
Motoko
M
Kuba
Masahiro
M
Ishii
Maiko
M
Abe
Naoki
N
Kitamura
Alexei
A
Verkhratsky
Izumi
I
Shibuya
Govindan
G
Dayanithi
D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000031:analogs & derivatives / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003712:Dendrites / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D006706:Homeostasis; D066298:In Vitro Techniques; D007811:Lanthanum / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013495:Supraoptic Nucleus / Q000378:metabolism*; D014475:Uncoupling Agents / Q000494:pharmacology
D014475:Uncoupling Agents; D001127:Arginine Vasopressin; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D007811:Lanthanum; D000252:Calcium-Transporting ATPases; D002118:Calcium