By perineurial recording, the actions of toosendanin on three potassiu
m currents and two calcium currents in the nerve terminal were observe
d in the intercostal nerve triangularis stein muscle of the mouse. Too
sendanin partially blocked the voltage-dependent fast K+ current and i
rreversibly increased the voltage-dependent slow Ca2+ current. The inc
rease in the Ca2+ current of the nerve terminal accounts for the facil
itation of transmitter release and the antibotulismic effect of toosen
danin.