Beta-agkistrodotoxin inhibits fast and Ca2+-activated K+ currents recorded from mouse motor nerve terminals

Beta-agkistrodotoxin (beta-AgTx), a polypeptide purified from the venom of Agkistrodon blomhoffii brevicaudus, is a presynaptic blocker acting on neurotransmitter release. In this work, perineural recording technique was employed to study the effects of beta-AgTx on sodium, potassium and calcium currents of mouse motor nerve terminals. The results showed that beta-AgTx selectively inhibited Ca2+-dependent (I(K,Ca)) and fast (I(K,f) K+ currents, but did not affect slow K+ current (I(K,s)), sodium and calcium currents. However there are other components in A. blomhoffii brevicaudus venom which inhibit perineural sodium current. The present data have provided additional evidence that the site of action of beta-AgTx is different from that of beta-bungarotoxin.