EFFECT OF PINELLIA-TERNATA LECTIN ON MEMBRANE CURRENTS OF MOUSE MOTOR-NERVE TERMINALS

Pinellia ternata lectin (PTL) extracted from the fresh juice of rhizom e of pinellia ternata used as a traditional Chinese medicine facilitat ed the quantal release of acetylcholine (ACh) in the mouse motor nerve terminals and formed cation channels in artificial lipid bilayer. Her e we report the action of PTL on presynaptic membrane currents of moto r nerve terminals. The experiments were performed on the intercostal n erve triangularis sterni muscle preparations. By means of the perineur ial recording, the effects of PTL on the sodium current in the preterm inal part, three potassium currents and two calcium currents generated from the nerve terminals were investigated. The results show that PTL increases voltage-dependent fast Ca2+ current (I-Ca,I-f), Na+ current (I-Na) and Ca2+-activated K+ current (I-K,I-Ca) without action on eit her the voltage-dependent fast K+ current (I-K,I-f) or the slow K+ cur rent (I-K,I-s) These effects are irreversible, but can be reversed by mannan, the specific binding sugar for PTL. The total action of PTL ca n be considered to raise [Ca2+](i) by promoting Ca2+ influx, and then facilitate the neurotransmitter release. To our knowledge, this is the first report about the influence of lectin on presynaptic membrane cu rrents at mammalian motor nerve terminals.