THE ROLE OF MONOAMINE-OXIDASE AND CATECHOL O-METHYLTRANSFERASE IN DOPAMINERGIC NEUROTRANSMISSION

The action of dopamine (DA) released in the synaptic cleft is mainly t erminated by its reuptake and catabolism by the enzymes monoamine oxid ase (MAO) and catechol O-methyltransferase (COMT). Preclinical data sh ow that the reduction of the catabolism of DA elicited by MAO and COMT inhibitors leads to an enhancement of DA neurotransmission. Moreover, there is evidence suggesting that MAO-B inhibition might protect DA n eurons from oxidative stress. Nevertheless, due to differences in enzy me localization and activity between man and rodents, results obtained in experimental animals might not reflect the actual situation in hum ans. Today the availability of potent and selective MAO and COMT inhib itors makes it feasible for the clinician to test whether the blockade of catabolic enzymes would result in a symptomatic improvement in Par kinsonian patients, and whether MAO-B inhibition might additionally ex ert a neuroprotective effect.