Chronopharmacological study of moclobemide effect on the rat pineal melatonin biosynthesis

The chronopharmacological hypothesis of the mechanism of the antidepressant effect of MAO-A inhibitors predicts that clinical efficacy depends upon the time of the day at which the drugs are administered. In the present study moclobemide (10 mg/kg, s.c.) injected at the end of the light phase advanced the onset of the nighttime increase of the rat pineal melatonin biosynthesis while the same dose of drug injected at the end of the dark phase delayed the daytime decrease of melatonin biosynthesis. The results obtained suggest that the timing of MAO-A inhibitor administration should be considered in clinical practice.