The effects of local inhibition of N-methyl-D-aspartate and AMPA/kainate receptors in the accessory olfactory bulb on the formation of an olfactory memory in mice.

Female mice form a memory to the pheromones of the mating male, during a critical period after mating. Previous experiments have shown that this memory is located in the accessory olfactory bulb and most likely involves changes at the mitral/granule cell reciprocal synapse. Memory formation can be prevented by local infusions of a non-selective ionotropic glutamate receptor antagonist. However, selective antagonism of N-methyl-D-aspartate receptors during the critical period did not disrupt the memory. The present study shows that memory formation is not prevented by local infusions of the AMPA/kainate receptor antagonist 6,7-dinitroquinoxaline-2,3-dione. Thus, it appears that the formation of a memory to the mating male can occur via both N-methyl-D-aspartate receptor-dependent and independent mechanisms. Far from preventing memory formation, local infusions of 6,7-dinitroquinoxaline-2,3-dione resulted in the formation of a non-selective "memory" to unfamiliar male pheromones. In addition, local infusions of 6,7-dinitroquinoxaline-2,3-dione during pheromonal exposure alone resulted in memory formation without mating having occurred. These results suggest that activity via N-methyl-D-aspartate receptors might be more effective in promoting the synaptic changes underlying memory formation, than activity via AMPA/kainate receptors.