The presynaptic activity of huwentoxin-I, a neurotoxin from the venom of the Chinese bird spider Selenocosmia huwena

Three different types of isolated nerve-synapse preparations, guinea pig il eum, rat vas deferens and toad heart, were used to investigate the physiolo gical activity of Huwentoxin-I, a neurotoxin from the venom of the spider S elenocosmia huwena. The twitch response of isolated guinea pig ileum induce d by electrical stimulus can be inhibited by HWTX-I. After blockage, contra ction of the ileum can be induced by exogenously applied acetylcholine. HWT X-I caused the inhibition of the twitch response to electrical nerve stimul ation in the rat vas deferens. After the twitch was completely inhibited, n oradrenaline triggered rhythmic contraction of the vas deferens. The inhibi tory effect on heart of toad induced by stimulating sympathetic-vagus nerve can be reversed by HWTX-I, although exogenously applied acetylcholine stil l acts as an effective inhibitor. All of these results support the conclusi on that HWTX-I has the presynaptic activity that effects the release of neu rotransmitter from the nerve endings of both the cholinergic synapse and th e adrenergic synapse, (C) 2000 Elsevier Science Ltd. All rights reserved.