Glutamate receptor subunits expression in memory-associated brain structures: Regional variations and effects of aging

We investigated regional variations and the effects of aging on the expression of the N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) receptor subunits in several memory-associated structures using Western blotting. In young adult rats, NR1, NR2A, and GluR2 levels varied between the hippocampus and parahippocampal region and between the subregions of the hippocampus. When a comparison was made between young (4-month-old) and aged (24-month-old) rats, significant decreases in NR1 expression were found in the aged ventral hippocampus and the entorhinal and postrhinal cortices. There were significant decreases in NR2A expression in the aged parahippocampal region, but not in the hippocampus. The expression of the G1uR2 subunit was significantly reduced in the ventral hippocampus and the postrhinal cortex. A dramatic decrease in NR1 and G1uR2 expression was found in the aged CA2/3 and CA1, respectively, but there were no significant age-related changes in NR2A expression. All three subunits were expressed at a similar level in the two age groups in the prefrontal cortex. These results suggest differential expression and effects of aging on NMDA and AMPA receptor subunits in memory-associated brain structures.