THE EFFECTS OF MONOAMINE-OXIDASE-B INHIBITION ON DOPAMINE METABOLISM IN RATS WITH NIGRO-STRIATAL LESIONS

The purpose of this study was to examine whether monoamine oxidase typ e B (MAO-B) has a role in striatal dopamine metabolism in animals with a unilateral lesion of the medial forebrain bundle, and whether 2-phe nylethylamine (PE) could have a role in amplification of dopamine (DA) responses in DA depleted striatum. Inhibition of MAO-B did not alter DA metabolism in lesioned striata. PE accumulation decreased with loss of DA as long as there was no DA dysfunction. In lesioned striata wit h dysfunction of DA transmission at the synaptic level, PE accumulatio n increased, suggesting a compensatory increase in PE synthesis. This increase in PE levels does not appear to be mediated by an increase in the total striatal aromatic L-amino acid decarboxylase (AADC) activit y. We conclude that inhibition of MAO-B has no effect on DA metabolism in the hemi-parkinsonian rat striatum and that PE could be involved i n the antiparkinsonian action of MAO-B inhibitors.