Neuropharmacological evaluation of methanolic extract of Costus speciosus Linn. rhizome in Swiss albino mice

Objective: To evaluate the neuropharmacological properties of Costus speciosus (C. speciosus) rhizome using different experimental mouse models. Methods: The anxiolytic effect was investigated by hole-board test, elevated plus maze and light/dark test, while central nervous system (CNS) depressant effect was evaluated by thiopental sodium-induced sleep test. Finally, antidepressant effect was evaluated by forced swimming test and tail suspension test. Results: In both elevated plus maze and hole board test, 400 mg/kg C. speciosus showed more significant CNS depressant effect than 1 mg/kg diazepam. Both 200 mg/kg and 400 mg/kg C. speciosus extract produced a significant dose-dependent decrease in onset of sleep. In forced swimming test, C. speciosus rhizome showed a decrease in duration of immobility in a dose-dependent manner. Imipramine (10 mg/kg) and C. speciosus extract at 400 mg/kg dose exhibited a significant reduction in duration of immobility in tail suspension test which provided additional evidence of antidepressant effect of C. speciosus rhizome. Conclusions: Our study indicates that C. speciosus rhizome possesses CNS depressant, anxiolytic and antidepressant-like activities. Further studies are warranted determine the exact phytoconstituents and mechanism of action responsible for the neuropharmacological effect.