Synthetic omega-conotoxin: a potent calcium channel blocking neurotoxin.
The Ca2+ channel blocking action of synthetic omega-conotoxin (omega CTX) was studied on isolated frog dorsal root ganglion neurons using a 'concentration clamp' technique which enabled internal perfusion and rapid external solution change. At 100 nM, omega CTX showed a time-dependent depression of Ca2+ current (ICa). At higher concentrations, omega CTX exhibited a dose-dependent depression of ICa amplitude without changing the current-voltage relationship. Increases in external Ca2+ concentration partly overcame the inhibitory action of omega CTX on the ICa amplitude. At 10 microM omega CTX totally blocked ICa without effect on the Na+ current. It was likely that omega CTX had high selectivity for the Ca2+ channel.
Department of Physiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Y
Y
Oyama
Y
Y
Tsuda
S
S
Sakakibara
N
N
Akaike
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002121:Calcium Channel Blockers; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008978:Mollusk Venoms / Q000633:toxicity*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009498:Neurotoxins / Q000633:toxicity*; D010477:Perfusion; D020866:omega-Conotoxin GVIA
D002121:Calcium Channel Blockers; D008978:Mollusk Venoms; D009498:Neurotoxins; D020866:omega-Conotoxin GVIA; D002118:Calcium