Antidepressant-like effect of different estrogenic compounds in the forced swimming test

The present study evaluated the possible antidepressant-like action of the natural estrogen 17beta-estradiol (E2, 2.5-10 mug/rat), the synthetic steroidal estrogen ethinyl-estr-adiol (EE2, 1.25-10.0 mug/rat), and the nonsteroidal synthetic estrogen, diethyl-stillbestrol (DES, 0.25-1.0 mg/ rat) in ovariectomized adult female Wistar rats using the forced swimming test (FST). The behavioral profile induced by the estrogens was compared with that induced by the antidepressants fluoxetine (FLX, 2.5-10 mg/kg) and desipramine (DMI, 2.5-10 mg/kg). In addition, the temporal course of the antidepressant-like action of the estrogenic compounds was analyzed. FLX and DMI induced an antidepressant-like effect characterized by a reduced immobility and increased swimming for FLX and decreased immobility and increased climbing for DMI. Both E2 and EE2 produced a decrease in immobility and an increase in swimming, suggesting an antidepressant-like action. DES did not affect the responses in this animal model of depression at any dose tested. The time course analysis of the actions of E2 (10 mug/rat) and EE2 (5 mug/rat) showed that both compounds induced an antidepressant-like effect observed I h after their injection lasting for 2-3 days.