Effect of uncoupling agents of oxidative phosphorylation on the spontaneous release of transmitter from insect motor nerve terminals.

1. The effect of uncoupling agents of oxidative phosphorylation, potassium warfarin and carbonylcyanide-p-trifluoromethoxy-phenylhydrazone (p-CCP), on the spontaneous release of transmitter was studied at the neuromuscular junction of cockroach muscles. 2. The agents produced a large increase in the frequency of occurrence of miniature excitatory postsynaptic potentials (MEPSPs). This increase also was observed in calcium-free saline. 3. The results may be explained on the hypothesis that the increase in the spontaneous release is due to the increase in free calcium concentration derived from an intracellular origin in the terminal. The mitochondria may play an important role in regulating the intracellular calcium concentration in the nerve terminals of insect muscles.