BRAIN REGIONAL DISTRIBUTIONS OF MONOAMINE-OXIDASE ACTIVITIES IN POSTNATAL-DEVELOPMENT IN NORMAL AND CHRONICALLY MANGANESE-TREATED RATS

To investigate the hypothesis that manganese toxicity may affect the d evelopment of the monoamine oxidases (MAOs) in brain, the regional dis tributions of the A (serotonin-oxidizing) and B (benzylamine-oxidizing ) forms of MAO were determined in manganese-treated (1 mg or 10 mg of MnCl2.4H2O per ml of drinking water from conception onwards until the rats were used for experiments) and untreated male rats during various stages of postnatal development. The age-related variations in region al MAO-A activities (especially in pons and medulla and in cerebellum) were more marked than those in regional MAO-B activities. The MAO-A:M AO-B activity ratios decreased in all regions during development. Chro nic manganese treatment (at the specified doses) did not significantly alter the age-related changes in regional MAO-A and MAO-B activities; nor were the A:B activity ratios affected. The results suggest that t here is differential expression of MAO isoforms in various brain regio ns during postnatal development but the expression is not affected by chronic manganese toxicity.