The effect of 6-months l-deprenyl administration on pineal MAO-A and MAO-B activity and on the content of melatonin and related indoles in aged female Fisher 344N rats.

Six months of administration of the selective MAO-B inhibitor, selegiline (l-deprenyl 0.25 mg/kg, s.c.) to aged female Fisher 344N rats suppressed MAO-A as well as MAO-B activity and increased serotonin (substrate for melatonin biosynthesis) and N-acetylserotonin (immediate melatonin precursor) levels in pineal glands taken from the animals during the night. Daytime values were unchanged by the treatment. The data suggest that stimulation of pineal melatonin biosynthesis might be one of the consequences of MAO-A inhibition contributing to life span prolongation induced by chronic selegiline treatment.