Evaluation of antidepressant activity of tramadol in mice: an experimental study

Background: In spite of availability of effective antidepressant drugs, depression continues to be a major problem. Hence, great interest is being taken in development of innovative antidepressants. Tramadol (TRM) is a centrally acting opioid agonist, which is clinically effective in the treatment of moderate to severe pain. By virtue of its action of inhibiting norepinephrine and serotonin uptake, it can function as an antidepressant like venlafaxine. Hence, this study was planned to evaluate antidepressant activity of TRM in comparison and in combination with fluoxetine (FLX) in albino mice.Methods: TRM (20 and 40 mg) and FLX (20 mg) were administered i.p., alone and in combination once daily for acute (7 days) and chronic (14 days) period to Swiss albino mice of either sex. The immobility period of control and treated mice was recorded in forced swimming test (FST) and tail suspension test (TST). The open field test was also done for same period to test the locomotor activity in animal. The antidepressant effect of TRM was compared with FLX and normal saline treated group for acute and chronic study period.Results: TRM (20 and 40 mg) treated group produced significant antidepressant effect alone and in combination with FLX (20 and 40 mg) as indicated by reduction in immobility period compared with control group in FST and TST. TRM and FLX treated groups did not show significant activity in open field test when compared with control group.Conclusions: This study shows TRM has antidepressant activity in standard models of depression