The novel and reversible inhibitors are the catechol-O-methyl-transferase (COMT) inhibitors, Ro 40-7592 (3,4-dihydroxy-4'-methyl-5-nitrobenzophenone), and the monoamine oxidase type-B (MAO-B) inhibitor, Ro 19-6327 (N-(2-aminoethyl)-5-chloro-2-pyridine carboxamide HC1).