RT Journal Article
SR Electronic
T1 Mechanism of the excitatory action of palytoxin and N-acetylpalytoxin in the isolated guinea-pig vas deferens.
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 209
OP 212
VO 214
IS 1
A1 Ohizumi, Y
A1 Shibata, S
YR 1980
UL http://jpet.aspetjournals.org/content/214/1/209.abstract
AB Palytoxin (PTX), one of the most well known potent toxic substances among marine toxins, caused a slow phasic contraction of the isolated guinea-pig vas deferens (second component) followed by the first rapid phasic contraction (first component) at concentrations above 3 x 10(-9) M. N-acetylpalytoxin, one of its derivatives, also produced similar actions but its potency was about 1/100 of that of PTX. The second component of PTX-induced contraction, but not the first component, was markedly inhibited by treatments with phentolamine, reserpine and 6-hydroxydopamine, but remained unaffected by atropine and mecamylamine pretreatment. Tetrodotoxin partially inhibited the second component, whereas the second component was markedly inhibited by solutions low in Na+ (85.2 mM) or containing verapamil (10(-6) M). Both components were completely abolished by high Mg++ or Ca++-free medium. It is concluded that the first component was the result of a direct action of PTX on smooth muscle sites, whereas the second phase was the result of an indirect action mediated through the norephinephrine release from the adrenergic nerve terminals.