Effects of imipramine on circadian rhythms in the golden hamster

The effects of the antidepressant imipramine on circadian organization were studied in wild-type and tau-mutant golden hamsters. Chronic imipramine treatment in doses ranging from 0-50 mg kg-1.day-1 depressed general activity and body temperature and caused a reduction in body weight but had no significant effect on circadian organization. Imipramine treatment did not affect the rate of reentrainment after a 6-h advance in the light-dark cycle, did not alter the advanced-phase angle of entrainment of tau-mutant hamsters, did not affect the free-running period of wild type hamsters, and did not alter the phase-response curve to light pulses. Because imipramine, a clinically effective antidepressant, did not have any measurable effect on the circadian system in these experiments, our results do not provide support for the hypothesis that the antidepressant action of imipramine is mediated by alterations in the circadian system.