Enhancement of transmitter release accompanying with long-term potentiation in synapses between mossy fibers and CA3 neurons in hippocampus.

This study was performed to answer the question whether long-term potentiation (LTP) in mossy fiber-CA3 synapses is accompanied by an enhanced release of transmitter. For this purpose, the relative magnitude of amplitude fluctuation (coefficient of variation, CV) of excitatory postsynaptic potentials (EPSPs) and the probability of transmission failures were examined in thin hippocampal sections from the guinea pig before and after tetanic stimulation of mossy fibers or alteration of Ca2+ concentration. The values of CV were reduced in association with increases in EPSP amplitude after tetanic stimulation or at high Ca2+ concentration. The probability of failures decreased after tetanic stimulation. These findings indicate an enhancement of release of transmitter from mossy fiber terminals after induction of LTP.