Regulation of Hippocampal Transmitter Release During Development and Long-Term Potentiation

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Abstract
Developmental changes in rat hippocampal transmitter release and synaptic plasticity were investigated. Recordings from pairs of pyramidal neurons in slices showed that an action potential in a CA3 neuron released only a single quantum of transmitter onto a CA1 neuron. Failures of synaptic transmission reflected probabilistic transmitter release. The probability of release ( P r ) was 0.9 in 4- to 8-day-old rats and decreased to less than 0.5 at 2 to 3 weeks. Long-term potentiation (LTP) in 2- to 3-week-old rats was associated with an increase in P r from a single synaptic site. The high initial P r in 4- to 8-day-old rats normally occludes the expression of LTP at this stage.