beta-Agkistrodotoxin inhibits fast and Ca2+-activated K+ currents recordedfrom mouse motor nerve terminals

beta-Agkistrodotoxin (beta-AgTx), a polypeptide purified from the venom of Agkistrodon blomhoffii brevicaudus, is a presynaptic blocker acting on neur otransmitter release. In this work, perineural recording technique was empl oyed to study the effects of beta-AgTx on sodium, potassium and calcium cur rents of mouse motor nerve terminals. The results showed that beta-AgTx sel ectively inhibited Ca2+-dependent. (I-K,I-Ca) and fast (I-K,I-f) K+ current s, but did not affect slow K+ current (I-K,I-s), sodium and calcium current s. However there are other components in A. blomhoffii brevicaudus venom wh ich inhibit perineural sodium current. The present data have provided addit ional evidence that the site of action of beta-AgTx is different from that of beta-bungarotoxin. (C) 1999 Elsevier Science Ltd. All rights reserved.