title: Effect of a reversible and selective MAO-A inhibitor (cimoxatone) on diurnal variation in plasma prolactin level in man.
abstract: Prolactin (PRL) secretion is stimulated by serotonin (5-HT) and inhibited by dopamine (DA). 5-HT is generally recognized as a substrate for type A monoamine oxidase (MAO), whereas DA is considered as a substrate for either A or B, or both forms of MAO, depending on the species and tissues used. The effect of cimoxatone, a reversible, selective MAO-A inhibitor, on diurnal variation in plasma PRL level was investigated in healthy adults after a single 40 mg oral dose, as an indirect approach to investigating whether DA is preferentially a substrate for Type A or B MAO in man. The circadian rhythm in PRL, stress conditions and diet were taken into account in the present study, which was placebo-controlled. There was a slight but significant reduction in circulating PRL in the six subjects, which persisted for at least 9 h after cimoxatone. However, the duration of the decrease in plasma PRL was shorter than the inhibition of MAO-A. The results are not inconsistent with the presence of both forms of MAO in the human hypothalamus and with DA as a substrate for both forms in this region, if it is assumed that the hypothalamic concentrations of the drug during the period 0-9 hours was sufficiently high to inhibit DA deamination by both forms of MAO.
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000187:drug effects*; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives / Q000652:urine; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology*; D010080:Oxazoles / Q000378:metabolism / Q000494:pharmacology*; D023303:Oxazolidinones; D011388:Prolactin / Q000097:blood*
chemical_list: D008996:Monoamine Oxidase Inhibitors; D010080:Oxazoles; D023303:Oxazolidinones; C030284:3-methoxy-4-hydroxyphenylglycol sulfate; D008734:Methoxyhydroxyphenylglycol; C038383:MD 770222; D011388:Prolactin; C026234:cimoxatone; D006854:Hydrocortisone