Comparison of actions of cardiotoxin-like principles from venow of bungarus fasciatus on excitable tissues

Toxin A (TA) and toxin B (TB) were isolated from venom of Bungarus fasciatus in Guangdong Province. TB was more potent than TA. TB decreased the direct muscle twitch only mildly after abolishing completely the indirect muscle twitch on frog nerve-muscle preparations. It simultaneously abolished the direct and indirect muscle twitches in rat nervemuscle prepartions. TA and TB markedly decreased the membrane potentials of Sartorius and myocardium in frogs. The change-rate of membrane potential in frog sartorius muscle wasfaster than that in myocardium. In view of the facts that the cardiac muscles were more resistant to “cardiotoxins” than skeletal muscles and that the toxins selectively blocked neuromuscular transmission in most cases, the name of “neurotoxin-like” principle would be more suitable than that of “cardiotoxin-like”principle.