title: Presynaptic inhibitory effect of geographutoxin II, a new peptide toxin from Conus geographus venom, in the guinea-pig vas deferens.
abstract: Geographutoxin II (GTX II), a new peptide toxin, isolated from Conus geographus venom, caused a dose-dependent inhibition of the contractile response of the guinea-pig vas deferens to transmural stimulation at concentrations of 3 X 10(-8) to 10(-6) M. The dose-response curves for noradrenaline, acetylcholine and KCl was not affected by GTX II (2 X 10(-7) to 10(-6) M). The release of noradrenaline induced by veratridine was strongly inhibited by GTX II. These results suggest that the GTX II-induced inhibition of the vas deferens may be a presynaptic effect causing a decrease of transmitter release.
mesh_terms: D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D004558:Electric Stimulation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008978:Mollusk Venoms / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000187:drug effects*; D010456:Peptides, Cyclic; D011189:Potassium Chloride / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects*; D014649:Vas Deferens / Q000187:drug effects; D014701:Veratridine / Q000494:pharmacology
chemical_list: D008978:Mollusk Venoms; D010456:Peptides, Cyclic; D011189:Potassium Chloride; D014701:Veratridine; C038094:geographutoxin II; D003000:Clonidine