Two classes of channel-specific toxins from funnel web spider venom

Abstract

The paralytic effects and neuromuscular actions ofAgelenopsis aperta venom on insects were analyzed biochemically and electrophysiologically. Paralysis caused byAgelenopsis venom is correlated with two effects on neuromuscular transmission: postsynaptic inhibition and presynaptic excitation. These effects are explained by the actions of two classes of toxins purified by RPLC, theα- and μ-agatoxins. Theα-agatoxins are low molecular weight, acylpolyamines which cause rapid, reversible paralysis correlated with use-dependent postsynaptic block of EPSPs and ionophoretic glutamate potentials. The μ-agatoxins are cysteine-rich polypeptides which cause irreversible paralysis and repetitive action potentials originating in presynaptic axons or nerve terminals. The joint actions of theα- and μ-agatoxins lead to significantly higher rates of paralysis than are obtained by either toxin class alone, and this may relate to enhancement by excitatory μ-agatoxins of use-dependent block caused byα-agatoxins.