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 ileum, rat vas deferens and toad heart, were used to investigate the physiological activity of Huwentoxin-I, a neurotoxin from the venom of the spider Selenocosmia huwena. The twitch response of isolated guinea pig ileum induced by electrical stimulus can be inhibited by HWTX-I. After blockage, contraction of the ileum can be induced by exogenously applied acetylcholine. HWTX-I caused the inhibition of the twitch response to electrical nerve stimulation in the rat vas deferens. After the twitch was completely inhibited, noradrenaline triggered rhythmic contraction of the vas deferens. The inhibitory effect on heart of toad induced by stimulating sympathetic-vagus nerve can be reversed by HWTX-I, although exogenously applied acetylcholine still acts as an effective inhibitor. All of these results support the conclusion that HWTX-I has the presynaptic activity that effects the release of neurotransmitter from the nerve endings of both the cholinergic synapse and the adrenergic synapse.