Medial amygdala stimulation produces a long-lasting excitatory postsynaptic potential/spike dissociation in the dentate gyrus in vivo.

We have previously found that high-frequency stimulation of the medial amygdala (MeA) induces long-term potentiation (LTP) of the population spike in the perforant path-dentate granule cell synapses of anesthetized rats. In the present study, we investigated the influence of MeA stimulation on the relationship between the population excitatory postsynaptic potential (pEPSP) and population spike in the dentate gyrus. High-frequency stimulation of the MeA produced a leftward shift of the E-S curve, in which population spike amplitude was plotted against pEPSP slope at various stimulus intensities. MeA-induced population spike LTP was also observed under blockade of GABAergic inhibition with picrotoxin. These results suggests that MeA stimulation leads to a long-lasting change in the internal firing characteristics of the dentate granule cells.