LONG-TERM POTENTIATION AT THE LATERAL PERFORANT PATH NUCLEUS-ACCUMBENS SYNAPSE IN THE RAT IN-VIVO

The nucleus accumbens (NAcb), a basal forebrain structure implicated i n drug-mediated reward, receives afferents from a variety of limbic an d cortical structures, including the prefrontal cortex, the amygdala, the entorhinal cortex, and the subicular complex. In the present study , monosynaptic projections from the lateral entorhinal cortex (lateral perforant path) to the NAcb are shown to display sustained increases in field EPSP magnitudes following high-frequency stimulation of the p erforant path in anesthetized rats. By contrast, stimulation of the me dial aspect of the perforant path, although capable of evoking respons es in the dentate gyrus, produced no observable synaptic responses wit hin the nucleus accumbens. Intra-accumbens administration of P(-3-(2-c arboxypiperazin-4-yl)-propyl-1-phosphonic acid), a selective competiti ve NMDA-receptor antagonist, blocked both short-term potentiation and long-term potentiation (LTP). Thus afferents from the entorhinal corte x to the NAcb display NMDA-receptor-dependent synaptic potentiation th at appears similar to NMDA-receptor-dependent LTP observed at other ta rgets of the perforant path, such as the hippocampal formation.