ABSTRACT
Monoamine oxidase (MAO) is a complex flavin-containing enzyme found principally on the outer mitochondrial membranes. Monoamine oxidase is one of the two main enzymes involved in the oxidative deamination of monoamines (1); the other enzyme is catechol o-methyl transferase (COMT) (2). Monoamine oxidase functions via oxidative deamination to inactivate more than 15 monoamines formed in the body, some of which serve important roles as synaptic neurotransmitters or neuro modulators, e.g., epinephrine, norepinephrine, dopamine, and 5-hydroxytryptamine (5HT) (3). As a result, the con centration of endogenous epinephrine, norepinephrine, dopamine, and serotonin increases in storage sites through out the nervous system. It is thought that the increase in the concentration of monoamines in the central nervous system (CNS) is the basis for the antidepressant activity of these agents, but their exact mechanism of action is unknown. The monoamine oxidase inhibitors (MAOIs) are valuable antidepressants that have for the most part been supplanted by the tricyclic antidepressants in the treatment of endogenous depression (4).
