A possible mechanism for the anxiolytic-like effect of gallic acid in the rat elevated plus maze.

This work was performed to characterize the possible mechanisms involved in the anxiolytic-like activity of gallic acid (GA) in the rat elevated plus maze (EPM) test. Male Wistar rats were acutely treated with a single dose of GA (10-500 mg/kg, i.p.) or diazepam and buspirone, 30 min prior to behavioral assessment in the EPM, open-field and rotarod tests. Treatment with GA markedly produced an increase in the time spent and entries in the open arms of EPM at doses of 30 and 300 mg/kg, respectively. These effects were comparable to those of the diazepam (1 mg/kg, i.p.) and buspirone (1 mg/kg, i.p.). Pretreatment with benzodiazepine antagonist flumazenil (3 mg/kg, i.p.) partially blocked the anxiolytic-like effect of GA. However, an increase in the time spent and entries in the open arms of EPM observed with GA treatment were significantly inhibited by the 5-HT1A receptor antagonist WAY-100635 (0.5 mg/kg, i.p.). In the open-field test, only GA at a dose of 500 mg/kg decreased locomotor activity in rats. Moreover, GA (10-300 mg/kg, i.p.) or diazepam and buspirone did not alter motor coordination in the rotarod test. These results indicate that GA is an effective anxiolytic agent at low doses, while at the highest dose it has sedative effect. Also this study suggests that the anxiolytic-like activity of GA is primarily mediated by the 5-HT1A but not benzodiazepine receptors.