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

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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.