Effects of MK-801 on spatial memory in homing and nonhoming pigeon breeds.

Homing pigeon breeds, the product of artificial selection on the basis of navigational and spatial ability, differ from nonhoming breeds in hippocampal size and distribution of N-methyl-D-aspartate (NMDA) dependent receptors. The effects of MK-801 (0.1 mg/kg administered intraperitoneally), a noncompetitive NMDA antagonist, on spatial reference memory (RM) were compared between the 2 breeds in a radial arm maze task. MK-801 disrupted the acquisition of RM in the nonhoming group but not the homing group, which was equivalent to the 2 saline-only control groups. As in previous findings with mammals, working memory was not affected by MK-801. This behavioral dissociation, coupled with differences in NMDA-dependent long-term potentiation between breeds, suggests an exceptional opportunity to investigate the role and function of the dorsomedial telencephalon region in spatial RM, through anatomical, neurochemical, and behavioral comparisons between homing and nonhoming pigeon breeds.