Faculty Bibliography

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

Long-term potentiation (LTP) in the hippocampus is a long lasting enhancement of the postsynaptic evoked response following high frequency, repetitive stimulation of afferents. The extracellularly recorded action potential (population spike) can be reversibly blocked, without affecting the extracellularly recorded excitatory postsynaptic potential, by focal application of gamma-aminobutyric acid, tetrodotoxin, or pentobarbital, to the CA1 pyramidal cells of the hippocampal slice. When the population spike is blocked during repetitive stimulation, LTP does not occur. It appears that postsynaptic firing of action potentials during repetitive stimulation is necessary to produce LTP