gamma-Aminobutyrate sensitivity does not change during long-term potentiation in rat hippocampal slices

Long-term potentiation is a long-lasting enhancement of synaptic efficacy following brief, high-frequency, repetitive stimulation of a monosynaptic input. Intracellular recordings have shown that the inhibitory postsynaptic potential changes in amplitude during long-term potentiation. Yet how this may occur is unclear. To test for a possible alteration in postsynaptic sensitivity to the recurrent inhibitory transmitter gamma-aminobutyrate, we have examined the effect of gamma-aminobutyrate, focally applied to the hippocampal CA1 cell-body layer, on the extracellular recorded action potential (population spike). We found that the degree, duration, dose-dependence and time-course of inhibition produced by gamma-aminobutyrate are unchanged during long-term potentiation. This suggests that a change in sensitivity of CA1 pyramidal cells to the transmitter gamma-aminobutyrate is not the reason for the alteration in the inhibitory postsynaptic potential during long-term potentiation.