Monoamine oxidase (MAO) exists in two forms distinguishable by substrate specificity. Inhibition of MA 0 A is believed to be responsible for the antidepressant activity of MA0 inhibitors. A group of N-arylacetamides are highly specific inhibitors of MA0 A, some with ICs0 values in the 10-100 nM range. The requirements for high activity and specificity include a nearly linear tricyclic aromatic portion but a larger and a smaller central ring ...