Effect of aging on dopamine metabolism in the rat cerebral cortex: a regional analysis

Age-related changes in the levels of dopamine (DA) and its metabolites were measured in seven cerebral cortical areas and in the striatum of 3, 10 and 27 month-old Sprague-Dawley rats. An age-related increase in DA levels was observed in the somatomotor (SM) cortex. In contrast, a decrease was observed in the temporal (T) cortex. Decreases in homovanillic acid (HVA) levels were observed in prelimbic (PL), pyriform (PY) and T cortex of aged rats, whereas significant increases in the levels of 3-methoxytyramine (3-MT) were observed in PL, prefrontal (PF), cingulate (C) as well as in T cortex. In the striatum, DA and HVA were decreased but the level of 3-MT remained unchanged. Norepinephrine (NE) levels increased in rats from 3 to 27 months in all the cortical areas. The increase in the levels of the DA extraneuronal metabolite, 3-MT, confirms our previous results showing that the release of DA might be increased with age in some cortical areas. The present results show that there is no general age-related decrease in the level of monoamines and of their metabolites in the rat cerebral cortex and that the changes display a complex, area-specific pattern.