Effects of NMDA receptor-related agonists on learning and memory impairment in olfactory bulbectomized mice.

A significant impairment of learning and memory-related behavior was induced in mice on the 7th and 14th days after olfactory bulbectomy (OBX), as measured by a passive avoidance task. The involvement of the N-methyl-D-aspartate (NMDA) receptor ion-channel complex for learning and memory-related behavior impairment was examined by the intracerebroventricular administration of several NMDA receptor-related agonists and in combination with antagonists. The NMDA receptor agonist NMDA (1 ng/mouse) and the polyamine site agonist spermidine (1 micro g/mouse) improved learning and memory-related behavior impairment. In contrast, the glycine agonist D-cycloserine (0.2, 1 and 5 micro g/mouse) had no effect on learning and memory-related behavior impairment. The improved effects by NMDA and spermidine were reversed by the coadministration of D-APV, a competitive NMDA receptor antagonist, MK-801, an NMDA ion-channel blocker and ifenprodil, a polyamine site antagonist, respectively. These results suggest that the degeneration of NMDA receptors and polyamine sites in the NMDA receptor ion-channel complex may be involved in the OBX-induced impairment of learning and memory-related behavior.