Progesterone reduces immobility in rats forced to swim.
BACKGROUND
Among its behavioral actions, 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 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.


RESULTS
Ovariectomy 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.


CONCLUSIONS
From these results, it is concluded that progesterone may possess some anti-depressant-like activity.
Martínez-Mota
L
L
Laboratorio de Neurofarmacología, Universidad Veracruzana, Xalapa, Veracruz, Mexico.
Contreras
C M
CM
Saavedra
M
M
D000818:Animals; D000928:Antidepressive Agents / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D007103:Immobilization; D010052:Ovariectomy; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013550:Swimming
D000928:Antidepressive Agents; D011374:Progesterone