Abstract
1. Monoamine oxidase from the liver and brain was inhibited by chlorpromazine. This inhibition was not reversed by cysteine, glutathione or FAD.
2. Monoamine oxidase was inhibited in decreasing order by chlorproma-zinc, phenergan, promazine, dichlorpromazine, 3-chloro, 10-piperidinoacetyl phenothiazine and chlorpromazine sulfoxide. Lysergic acid diethylamide stimulated MO slightly.
3. Chlorpromazine had no effect liver MO in vivo, while it slightly decreased 5-hydroxyindole acetaldehyde formation from serotonin by brain MO.
4. Several metabolites of serotonin were found in vitro in homogenates of various organs. One of these seemed to be N-methylserotonin.
