Determination of levels of biogenic amines and their metabolites and both forms of monoamine oxidase in prefrontal cortex of aged rats.

Levels of dopamine, noradrenaline and serotonin and their metabolites and the activities of monoamine oxidase A and B, have been determined in the prefrontal cortex of the rat during ageing. Serotonin turnover rate has been measured as 5-hydroxytryptophan accumulation rate after central decarboxylase inhibition. The major changes were an increase of dopamine and noradrenaline levels and a decrease of serotonin in aged animals compared with control animals. A decrease of the MAO-A to MAO-B ratio was found in aged rats.