A crotamine-like toxin (horridus-crotamine) was isolated from the venom of Crotalus h. horridus and its effects on the neuromuscular transmission of skeletal muscle were studied. In the baby chick biventer cervicis muscle and the phrenic nerve-diaphragm preparations of mice and rats, the toxin augmented the contractile force of muscle elicited either indirectly or directly and produced repetitive irregular twitchings even in the absence of electrical stimulation at concentrations of 1-10 μg per ml. In the chick muscle, this stimulatory effect was completely abolished or prevented by high Ca2+, high Mg2+, high K+, tetrodotoxin, D-tubocurarine and β-bungarotoxin, whereas in the mouse or rat diaphragm, the contractile augmentation was still observed after pretreatment with D-tubocurarine or β-bungarotoxin and also after denervation. After washing, the stimulatory effect including spontaneous twitchings reappeared in the muscle preparations pretreated with high Ca2+, high Mg2+ and D-tubocurarine, but did not resume in those pretreated with high K+ and tetrodotoxin. From these results, it is concluded that in the chick muscle, the site of action of this toxin is pre-synaptic rather than postsynaptic, whereas in the mammalian skeletal muscle, this toxin appears to act mainly, if not entirely, on the muscle itself.
|頁（從 - 到）||833-842|
|期刊||Journal of the Formosan Medical Association|
|出版狀態||Published - 1982|