The purpose of this investigation was to characterize the putative anxiolytic-like activity of methanolic, ethyl acetate extract and alkaloid rich fraction prepared from the stem-bark of Mitragyna parvifolia (Roxb.) Korth (Rubiaceae) using the elevated plus maze (EPM) and marble burying test (MBT) in mice. The extracts increased the time spent on and the number of entries into the open arms of the EPM in doses of 200 and 400 mg/kg p.o., respectively. This effect was comparable to that of negative control group treated with 0.5 % CMC and positive control the benzodiazepine diazepam (1.0 mg/kg p.o.) was used as a standard. When evaluated by MBT the number of marbles buried by mice was decreased significantly as compared to control group CMC 0.5 %. Fluoxetine (10 mg/kg p.o.) was used as a standard for comparison. These results indicate that all the extract were effective in dose dependent manner and proved statistically significant at higher doses but alkaloid rich fraction was found to be more potent in producing anxiolytic effects by both test. It suggest that the anxiolytic-like activities of this plant are mainly mediated via the GABAergic system. Neither diazepam nor the test extracts produced any overt behavioral change or motor dysfunction in the performed tests.
