[Attenuation of the effect of imizin on the dynamics of forced swimming and the circadian rhythm of mobility in rats chronically administered melatonin].

Imizine (10 mg/kg, 14 days) was shown to change the temporal dynamics of forced swimming in rats and to decrease the biorhythmical index of depression. The antidepressant also produced reorganization of the circadian rest-activity rhythm with the acrophase shift for the late night hours. A pineal hormone melatonin (1 and 10 mg/kg, 7 days) administered in combination with imizine attenuated the main rhythmic indices of its action and precipitated the occurrence of tolerance.