INHIBITION OF MAO-B BY (-)-DEPRENYL ALTERS DOPAMINE METABOLISM IN THEMACAQUE (MACACA-FASCICULARIS) BRAIN

The present study has examined whether MAO-B has a role in DA metaboli sm in the primate CNS in situ. Eleven macaques (macaca facicularis) we re used in this study to examine the effects of (-)-deprenyl (1 mg/kg, i.v., 2 and 24 hours). (-)-Deprenyl administration completely and sel ectively blocked MAO-B activity and blocked DA metabolism in the cauda te nucleus and frontal cortex. DA metabolism in the substantia nigra w as not affected by MAO-B inhibition. Changes in DA metabolism were acc ompanied by changes in 5-hydroxytryptamine (5HT) turnover: 5-hydroxyin dole acetic acid (5HIAA) levels increased in the caudate and decreased in the frontal cortex. Levels of 2-phenylethylamine (PE), a putative modulator of dopaminergic transmission, were increased by MAO-B inhibi tion in all three brain regions examined. It is concluded that in some regions of the primate brain, in contrast to the rat, MAO-B has an im portant role in DA metabolism.