Postsynaptic firing during repetitive stimulation is required for long-term potentiation in hippocampus.

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.