Activation of N-methyl-D-aspartate receptors contributes to the EPSP at perforant path synapses in the rat dentate gyrus in vitro.

The excitatory postsynaptic potential (EPSP) evoked in the granule cells of the rat dentate gyrus following low frequency stimulation of the perforant path has been investigated using intracellular recording. The EPSP was reduced by low microM concentrations of the non-N-methyl-D-aspartate (NMDA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). A small CNQX-resistant component of the EPSP remained. This could be blocked by the NMDA receptor antagonist (+/-)-2-amino-5-phosphonovalerate, was enhanced in Mg2+-free medium and showed a potential-dependency characteristic of the activation of NMDA ionophores. These results demonstrate that NMDA receptors contribute to the EPSP in the granule cell.