[Effect of cinobufagin on the guinea pig vas deferens and its mechanism of action].

Cinobufagin, one of the active principles extracted from toad venom, was studied on the isolated vas deferens of the guinea pig. The preparation was suspended in a bath containing 10 ml Krebs solution. Isometric tension of vas deferens was recorded on polygraph with a force displacement transducer. Cinobufagin caused a long lasting contraction of the vas deferens of the guinea pig at concentrations of 15-50 mumol/L. The contraction was inhibited following reserpinization and cold storage treatment. The cinobufagin induced contraction was partly blocked by pretreatment with phentolamine and verapamil. These results suggest that the cinobufagin induced contraction of vas deferens might be related to an action which promotes release of NA from the adrenergic nerve terminals.