Age-related changes in brain biogenic monoamines and monoamine oxidase

In experiments on 2-, 10- and 22-month old rats, it was found that essential age-related changes occurred in the brain level of biogenic monoamines (BMA) and in the monoamine oxidase (MAO) activity. In 22-month old rats the levels of dopamine (DA), noradrenaline (NA) and serotonin (5-HT) markedly declined in most of the brain structures studied. 5-HT significantly decreased in the frontal cortex, striatum and hypothalamus. DA decreased in the cerebral cortex and striatum and NA in the cerebral cortex. However, the NA level in the striatum of 22-month old rats was increased as compared to that in 2-month old rats. In most cases we observed significant differences (a decrease mainly) also in the level of BMA in 22-month old rats as compared to 10-month old rats. The differences, if any, in the BMA levels between 10- and 2-month old rats were less pronounced. The level of 5-hydroxyindole acetic acid (5-HIAA) in the cerebral cortex and striatum of 22-month old rats was significantly higher as compared to that in 2-month old rats. The MAO-T and MAO-A activities in the brain structures studied were significantly higher in 22-month old rats as compared to those in 2-month old rats. The possibility that the age-related changes in brain neurotransmission might be an important element in the neurochemical basis of some behavioral changes in advanced age is considered.