INHIBITORY-ACTION OF N(OMEGA)-NITRO-L-ARGININE METHYL-ESTER ON IN-VIVO LONG-TERM POTENTIATION IN THE RAT DENTATE GYRUS

Recent in vitro observations have led to the suggestion that nitric oxide (NO) plays a modulatory role in the expression of long-term potentiation (LTP). We investigated whether an NO synthesis inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME), affects the generation of LTP in anesthetized rats in vivo. Administration of L-NAME (0.1 and 1 nmol, i.c.v.) suppressed the magnitude of LTP dose dependently in the dentate gyrus of anesthetized rats. Co-injection of L-arginine, which interferes with the inhibitory action of L-NAME on NO synthesis, reversed these effects, whereas there was no reversal in rats that received co-administration with D-arginine. These results provide further support for the hypothesis that NO plays a modulatory role in the expression of synaptic potentiation.