Nucleus basalis injections of N-methyl-D-aspartate enhance memory of rats in the double Y-maze.

N-methyl-D-aspartate (NMDA) receptors have been implicated in learning and memory. Many findings show that NMDA receptor antagonists impair memory. Few studies, however, have investigated the role of NMDA receptor agonists in mnemonic function. The present study examined the effects of nucleus basalis magnocellularis (nbm) injections of NMDA on memory. Rats were trained in a two-component double Y-maze task consisting of a spatial discrimination and a delayed alternation. Rats (n = 7) were surgically implanted with bilateral cannulae in the nbm prior to maze training. Once trained, animals received bilateral nbm injections (0.5 microl) of saline (0.9%), NMDA (50, 75, and 100 ng/side), and the benzodiazepine receptor partial inverse agonist N-methyl-beta-carboline-3-carboxamide (FG 7142; 200 ng/side), in a counterbalanced order. During testing, delays (0, 30, 60 s) were introduced. Nbm FG 7142 or NMDA (50 ng/side) produced an improvement in the delayed alternation task. Results support the hypothesis that nbm NMDA receptors are involved in cognitive processes mediating memory.