شمس الدین احمدی

The possible involvement of N-methyl-D-aspartate (NMDA) receptors of the nucleus accumbens (NAc) in amnesia induced by scopolamine was investigated. An inhibitory (passive) avoidance task was used for memory assessment in male Wistar rats. The results revealed that intra nucleus accumbens (intra-NAc) administration of a nonselective muscarinic acetylcholine antagonist, scopolamine (1 and 2 µg/rat) impaired memory consolidation in the animals when tested 24 h later (as an index of amnesia). Post-training intra-NAc administration of NMDA (0.005 and 0.01 µg/rat) also impaired memory consolidation, while post-training intra-NAc administration of NMDA receptor antagonist, MK-801 (0.5, 1 and 1.5 µg/rat) caused no change in memory consolidation. Intra-NAc co-administration of an ineffective dose of NMDA with ineffective doses of scopolamine (0.25 and 0.5 µg/rat) after training caused no significant effect on memory consolidation, but intra-NAc injections of effective doses of NMDA (0.005 and 0.01 µg/rat) prevented the amnesic effect of an effective dose of scopolamine (2 µg/rat). On the other hand, intra-NAc co-administration of MK-801 (0.5, 1 and 1.5 µg/rat) along with an effective dose of scopolamine (2µg/rat) could not prevent the effect of the later drug. The data on the test day from animals which did not receive shock on the training day compared to those from shocked, drug treated animals (effective doses of scopolamine and NMDA) on the training day revealed that there was a significant effect of shock on consolidation of inhibitory avoidance memory. It can be concluded that NMDA receptors in the NAc are involved in the modulation of memory consolidation which was affected by scopolamine.