Antianxiety-like activity of gallic acid in unstressed and stressed mice: possible involvement of nitriergic system.

The aim of present study was to evaluate antianxiety-like activity of gallic acid in Swiss young male albino mice; and to explore the possible underlying mechanisms for this activity. Gallic acid (5, 10, 20 mg/kg, i.p.) and alprazolam (0.25 mg/kg, i.p.) were administered for 10 successive days to separate groups of mice. On 10th day, 45 min after the drug administration, stress was produced by immobilization of mice for 150 min and these mice were called as stressed mice. Anxiolytic activity was evaluated using elevated plus maze and light-dark test. The plasma nitrite and corticosterone levels were also estimated in unstressed and stressed mice. Effects of 7-nitroindazole (neuronal NOS inhibitor) and aminoguanidine (inducible NOS inhibitor) on antianxiety-like activity of gallic acid were also evaluated. Gallic acid (10 and 20 mg/kg) and alprazolam per se significantly showed antianxiety-like activity in both unstressed and stressed mice. The drugs did not show any significant effect on locomotor activity of the mice. Gallic acid significantly decreased the plasma nitrite levels in both unstressed and stressed mice. 7-nitroindazole and aminoguanidine significantly enhanced antianxiety-like activity and plasma nitrite decreasing effect of gallic acid in unstressed and stressed mice respectively. Plasma corticosterone levels were significantly decreased by gallic acid in stressed mice as compared to its control. Thus, gallic acid showed antianxiety-like activity in unstressed mice probably by inhibition of nNOS. On the other hand, antianxiety-like activity in stressed mice might be through inhibition of iNOS and reduction of plasma corticosterone levels.