Age-related changes in the glutamate metabolism of cerebral cortical slices from rats.

The glutamate metabolism in cerebral cortical slices from young (12 weeks) and aged (100 weeks) rats was studied. A highly significant reduction of low affinity glutamate uptake and its metabolism in the aged rats by 14.5% of the amount of the young rats was observed (P less than 0.001). When the ratio of the radioactivity of respective metabolite divided by the sum total radioactivity of overall glutamate metabolites was compared, the incorporation to aspartate was significantly small (P less than 0.01), while that of the CO2 liberated and the GABA synthesized were increased (P less than 0.05). These results support the hypothesis that in cerebral cortical slices from aged rats the transamination of glutamate is suppressed and its decarboxylation is enhanced despite markedly reduced low affinity glutamate uptake into the cerebral cortex. The difference could be explained by the fact that cerebral cortical slices from aged rats are more vulnerable to anoxia than those from young rats when exposed during slice preparation.