Progesterone reduces immobility in rats forced to swim

RESUMO

Background. Among its behavioral action, progesterone reduces anxiety in several species including humans; however, any antidepressant-like properties remain to be explored. Methods. In the present study, Wistar rats received injections (i.p.) of progesterone (0.20-3.0 mg/kg) 24 and 2 h before being submitted to the forced swim, a test in which antidespressants regulary reduce immobility and exert few or on action on locomotor activity. In order to discard the cumulative effects of progesterone and a possible effect from the repetition of the swimming test, all animals received one of several progesterone doses in a different sequence following a completely randomized experimental intrasubjects design. Results. Ovariectomy did not modify immobility in the forced swin test as compared to control test practiced before surgery- A dose of 0.80 mg/kg strongly reduced the total time of immobility in forced swin test (p< 0.001), but did not modify locomotor activity. In a drug-free control test applied 1 week after the injection of progesterone, immobility returned to the higher values observed in the control tests. Conclusions. From these results, it is concluded that progesterone may possess some antidepressant-like activity