The calcium channel antagonist omega-conotoxin inhibits secretion from peptidergic nerve terminals.
The binding of omega-conotoxin to isolated rat neurohypophysial nerve terminals, its effect on the depolarization-induced increase of cytoplasmic Ca2+ and on the potassium and electrically-induced release of vasopressin (AVP) have been studied. The results show that isolated neurosecretory nerve endings have calcium channels with a high affinity for omega-CgTx and that this toxin inhibits neurohormone release at very low concentration (IC50 = 0. 1nM). Although secretion of vasopressin is inhibited to a great extent by the toxin it is shown that a small but significant amount of the depolarization-induced AVP release is insensitive to omega-CgTx and to the dihydropyridine molecule nicardipine.
Dayanithi
G
G
Centre de Neurochimie, Strasbourg, France.
Martin-Moutot
N
N
Barlier
S
S
Colin
D A
DA
Kretz-Zaepfel
M
M
Couraud
F
F
Nordmann
J J
JJ
D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002462:Cell Membrane / Q000502:physiology; D004095:Dihydropyridines / Q000494:pharmacology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008978:Mollusk Venoms / Q000378:metabolism / Q000494:pharmacology*; D009411:Nerve Endings / Q000187:drug effects / Q000502:physiology*; D009529:Nicardipine / Q000494:pharmacology; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012016:Reference Values; D014700:Verapamil / Q000031:analogs & derivatives / Q000494:pharmacology; D020866:omega-Conotoxin GVIA
D002121:Calcium Channel Blockers; D004095:Dihydropyridines; D008978:Mollusk Venoms; D001127:Arginine Vasopressin; C038806:1,4-dihydropyridine; D020866:omega-Conotoxin GVIA; C043184:4-desmethoxyverapamil; D014700:Verapamil; D009529:Nicardipine; D011188:Potassium