Progesterone Reduces Immobility in Rats Forced to Swim

Background its behavioral actions, progesterone reduces anxiety in several species including humans; however, any antidepressant-like properties remain to be explored. s 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 antidepressants regularly reduce immobility and exert few or no actions 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 intrasubject design. s ctomy did not modify immobility in the forced swim test as compared to control tests practiced before surgery. A dose of 0.80 mg/kg strongly reduced the total time of immobility in forced swim test (p <0.001), but did not modify locomotor activity. In a drug-free control test applied 1 week after the last injection of progesterone, immobility returned to the higher values observed in the control tests. sions hese results, it is concluded that progesterone may possess some antidepressant-like activity.