title: Human plasma melatonin is elevated during treatment with the monoamine oxidase inhibitors clorgyline and tranylcypromine but not deprenyl.
abstract: Melatonin was measured in plasma collected between 8:00 and 8:30 a.m. from 27 depressed patients studied before and after 21- to 24-day treatment with three monoamine oxidase (MAO) inhibitors. Baseline plasma melatonin concentrations determined by radioimmunoassay were 4.0 +/- SD 4.7 pg/ml. Tranylcypromine, a nonselective MAO inhibitor given in doses of 20-40 mg/day for 3 weeks, significantly elevated plasma melatonin to 10.6 +/- SD 2.0 pg/ml. Clorgyline, given in doses of 15-30 mg/day for 3 weeks, produced a significant, approximately three-fold increase in plasma melatonin (13.6 +/- SD 13.5 pg/ml). This clorgyline dose was selective for MAO type A inhibition, as MAO-B activity measured in platelets from the same blood samples was unaffected by clorgyline. In contrast, the selective MAO-B inhibitor deprenyl (10-30 mg/day for 3 weeks) led to a 96 +/- 4% inhibition of platelet MAO-B activity but no significant change in plasma melatonin (5.1 +/- SD 4.2 pg/ml). As both serotonin and norepinephrine are preferentially metabolized by MAO-A rather than MAO-B, an increased availability of serotonin (the precursor of melatonin) or enhanced noradrenergic function might mediate the melatonin changes observed to follow MAO-A but not MAO-B inhibition.
mesh_terms: D001792:Blood Platelets / Q000187:drug effects; D003010:Clorgyline / Q000627:therapeutic use; D003866:Depressive Disorder / Q000188:drug therapy* / Q000201:enzymology; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000097:blood*; D008995:Monoamine Oxidase / Q000097:blood; D008996:Monoamine Oxidase Inhibitors / Q000627:therapeutic use*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects; D012642:Selegiline / Q000627:therapeutic use; D014191:Tranylcypromine / Q000627:therapeutic use
chemical_list: D008996:Monoamine Oxidase Inhibitors; D011943:Receptors, Adrenergic, beta; D012642:Selegiline; D014191:Tranylcypromine; D008995:Monoamine Oxidase; D008550:Melatonin; D003010:Clorgyline