Reversal of excitatory postsynaptic potential spike potentiation in the CA1 area of the rat hippocampus

In the CA1 area of the hippocampus, low frequency and tetanic conditioning stimuli are known to trigger long-term depression and potentiation of synaptic responses respectively and to produce irreversible excitatory postsynaptic potential/spike potentiation, i.e. an increase of the probability of discharge of the neurons. Using simultaneous extracellular recordings in stratum radiatum and stratum pyramidale in the CA1 area of the rat hippocampus, brief application of the K+ channel blocker tetraethylammonium resulted both in long-term potentiation of synaptic responses and in excitatory postsynaptic potential/spike potentiation that could be reversed by subsequent low frequency or tetanic stimuli. Excitatory postsynaptic potential/spike potentiation and its subsequent reversal by an electrical conditioning stimulus were found to have an N-methyl-D-aspartate receptor-independent component. We conclude that the reversal of excitatory poslsynaptic potential/spike potentiation can occur and that it does not require the induction of long-term modification of synaptic responses. (C) 1998 IBRO. Published by Elsevier Science Ltd.