MONOAMINE-OXIDASE ISOENZYMES IN RAT-BRAIN - DIFFERENTIAL CHANGES DURING POSTNATAL-DEVELOPMENT BUT NOT AGING

Differential development of monoamine oxidase (MAO) isoenzymes in rat whole brain is described in postnatally developing Sprague-Dawley rats . Total MAO and isoenzyme activity was measured using nonspecific and specific substrates. Total MAO activity measured using tyramine, incre ased postnatally up to 24 weeks of age and attained a plateau afterwar d. The increase in total MAO activity was significant at all age group s (18 days to 36 months) investigated as compared to new born rats. MA O-A and MAO-B activities were measured using octopamine and benzylamin e respectively. We also observed a marginal increase of MAO-A activity and a significant increase of MAO-B activity upon development. Furthe rmore, at 12 weeks of age, MAO-B activity increased by 10-fold as comp ared to new born and was consistent up to 36 months of age. The qualit ative localization of the enzyme activity on non SDS-PAGE by nitroblue tetrazolium staining confirmed the increase of MAO-B during the devel opment. It is suggested that the maturational increase of total MAO ac tivity in brain is predominantly due to the increase of MAO-B isoenzym e.