Anxiolytic and Antidepressant Effects of a Leaf Extract of Palisota hirsuta K. Schum. (Commelinaceae) in Mice

The effect of a 70% (v/v) ethanolic leaf extract of Palisota hirsuta, a traditional West African plant used for CNS disorders and pain, in animal models of anxiety and depression-the open field test, the light/dark box, the Elevated plus Maze (EPM), the Forced Swimming Test (FST) and Tail Suspension Test (TST) has been reported. P. hirsuta (30-300 mg kg(-1)) treated mice exhibited anxiolytic activity in all the anxiety models used by significantly increasing the percentage of center entries and the percentage time spent in the center of the open field. P. hirsuta also significantly increased the time spent in the lit area in comparison to the time spent in the dark area of the light/dark box. In the EPM, it significantly increased open arm activity which was completely reversed by flumazenil (3 mg kg(-1)), a specific antagonist of the GABA(A) benzodiazepine receptor complex. In the antidepressant test, the extract also dose-dependently reduced the duration of immobility in both the FST (ED50: 114.55 +/- 72.69 mg kg(-1)) and TST (70.42 +/- 0.06 mg kg(-1)). Pretreatment with a-methydopa (400 mg kg(-1); 3 h; p.o.), reserpine (1 mg kg(-1); 24 h; s.c.) or a combination of the two drugs attenuated the anti-immobility effects of both imipramime and the extract but not fluoxetine. Neither the extract nor the standard drugs used modified motor performance on the rotarod test at all doses tested. These results suggest that the extract has anxiolytic and antidepressant-like effects in the models employed possibly by GABAergic activation and/or effect on monoamine levels in the CNS.