SITES OF ACTION OF LEAD ON SPONTANEOUS TRANSMITTER RELEASE FROM MOTOR-NERVE TERMINALS

Abstract

Pb ions have potent neurotoxic activities. At the neuromuscular junction, they depress the neurally evoked release, but they strongly facilitate the spontaneous release of transmitter quanta from motor nerve terminals. The mechanisms underlying the latter action of Pb were studied in the isolated frog neuromuscular preparation. Evidence was consistent with the hypothesis that Pb ions inhibited some membranal and intracellular Ca regulatory mechanisms, producing an increase in the intraterminal concentration of ionized Ca and spontaneous transmitter release.