NMDA receptor antagonists block norepinephrine-induced long-lasting potentiation and long-term potentiation in rat dentate gyrus.

In the in vitro rat dentate gyrus, norepinephrine-induced long-lasting potentiation (NELLP) and long-term potentiation (LTP) of responses to perforant path stimulation were blocked by the N-methyl-D-aspartate (NMDA) receptor antagonists, D(-)-2-amino-5-phosphonovaleric acid (D(-)APV) and 3-[(+/-)-2-carboxypiperazin-4-yl]propyl-1-phosphonic acid (CPP). CPP and D(-)APV, but not L(+)APV, also depressed the orthodromic population spike but not the antidromic spike, which suggests that these receptors may function in low-frequency evoked activity of granule cells. We conclude that NELLP, like LTP in the dentate gyrus, requires NMDA receptor activation.