[Characteristics of the combined action of melatonin and imizin on the structure of forced swimming and the circadian rhythm].

Acute administration of melatonin (10 mg/kg) produced a depressed effect on the mice behavior. But it's injection after chronic imipramine (10 mg/kg/day, 2 weeks) potentiated antidepressant ability and shortened the duration of immobility in the structure of swimming. In rats, which had a high amplitude of circadian rest-activity rhythm, melatonin produced imipramine effect on circadian mobility, but potentiated antidepressant action in animals with low initial level of locomotor activity.