Quantal mechanism of long-term synaptic potentiation.

Intracellular recordings were used to demonstrate the occurrence and to analyze the microphysiology of long-term synaptic potentiation (LTP) in the crayfish opener neuromuscular synapse. Brief stimulation of the single excitor motor axon enhanced the amplitudes of subsequent postsynaptic potentials for several hours. Three methods of quantal analysis were used to evaluate the mechanism responsible for LTP. The results of all three methods supported predictions of the hypothesis that LTP results from a presynaptic mechanism that increases the average of neurotransmitter quanta evoked by nerve impulses in the excitor axon.