Modulatory effect of ATP on the release of acetylcholine from presynaptic nerve terminals in bullfrog sympathetic ganglia.

The effect of adenosine triphosphate (ATP) on the release of acetylcholine (ACh) from presynaptic nerve terminals was investigated in bullfrog sympathetic ganglia. ATP decreased the amplitude and quantal content of fast excitatory postsynaptic potentials (fast e.p.s.p.s) calculated from the variance of fast e.p.s.p. amplitude in a low Ca2+-high Mg2+ Ringer solution. The frequency of miniature e.p.s.p.s (m.e.p.s.p.s) recorded in high K+ Ringer solution was also reduced by ATP. The amplitude of the action potential of preganglionic nerve terminals recorded with an extracellular microelectrode was reduced by ATP. ATP produced a marked depolarization of the membrane of preganglionic nerve terminals. These results suggest that the reduction of the amount of ACh released from preganglionic nerve terminals by ATP may result from a decrease in Ca2+ influx due mainly to a depolarization of the preganglionic nerve terminals.