Long-term potentiation in the perirhinal-hippocampal pathway is NMDA dependent

The putative memory mechanism known as long-term potentiation (LTP) has been described in both NMDA-dependent and non-NMDA-dependent forms. The aim of the present study was to determine which of these forms described the LTP generated between perirhinal cortex (PRC) and hippocampus, two structures which have previously been implicated in learning and memory processes. In urethane-anaesthetized rats, high-frequency stimulation of the PRC induced a significant potentiation of PRC-hippocampal field potentials which was blocked by the NMDA receptor antagonist, MK-801. These data demonstrate that perirhinal-hippocampal LTP is NMDA-dependent and, moreover, that hippocampal-dependent learning which occurs during blockade of the NMDA receptor cannot be attributed to LTP of this pathway.