Behavioral and biochemical evidences for antidepressant-like activity of palmatine in mice subjected to chronic unpredictable mild stress.

BACKGROUND In the present study, antidepressant-like activity of palmatine was evaluated in unstressed and stressed young male Swiss albino mice. METHODS The animals were subjected to unpredictable mild stress daily for 21 successive days to induce depression-like behavior. Palmatine (0.25, 0.5, 1 mg/kg, ip) was administered for 21 successive days to unstressed and stressed mice. The antidepressant-like activity was evaluated using the tail suspension test, forced swim test and sucrose preference test. RESULTS Palmatine (0.5 and 1 mg/kg, ip) significantly decreased immobility periods of unstressed and stressed mice in the forced swim test and tail suspension test, thus indicating its significant antidepressant-like activity. Only the highest dose (1 mg/kg) of palmatine significantly reversed the stress-induced decrease in sucrose preference. There was no significant effect on locomotor activity of the mice by palmatine and fluoxetine. The antidepressant-like activity of palmatine was found to be comparable to fluoxetine (10 mg/kg) administered for successive 21 days. Palmatine (0.5 and 1 mg/kg, ip) significantly reversed the stress-induced increase in brain catalase levels, MAO-A activity, lipid peroxidation, plasma nitrite and corticosterone levels. CONCLUSIONS Palmatine showed significant antidepressant-like activity in unstressed and stressed mice probably through inhibition of MAO-A activity, decrease in plasma nitrite levels and due to its antioxidant activity. In addition, palmatine also showed antidepressant-like activity in stressed mice probably through decrease in plasma corticosterone levels.