Evaluation of role of noradrenergic system in the antidepressant activity of tramadol using forced swim test in albino mice

Several studies have suggested that tramadol could play a role in mood improvement. The present study was undertaken to evaluate the role of noradrenergic system in the antidepressant activity of tramadol in a test predictive of antidepressant activity in mice. Animals were divided into five groups, and each group comprised of six mice. Group 1 (control group) was pretreated with normal saline (0.1 ml/10 g). Groups 2, 3 and 4 were pretreated with three different doses (10, 20, and 40 mg/kg) of tramadol. Group 5 was pretreated with imipramine at the dose of 10 mg/kg. All the drugs were given intraperitonially (0.1 ml/10 g). After 15 minutes of drug administration, mice were placed individually in the 5 L glass beakers, filled to a height of 15 cm with water (room temperature) and the duration of immobility is recorded during the last 4 minutes of a 6 minutes test. In the next stage of the study, procedure was repeated with six different groups of animalse, each group comprising of six mice. The groups of animals here included animals pretreated with 40 mg/kg of tramadol, propranolol 5mg/kg, tramadol 40mg/kg + propranolol 5mg/kg, phentolamine 10mg/kg, and phentolamine 10mg/kg + tramadol 40mg/kg. Tramadol at 40mg/kg dose on acute as well as chronic administration for 10 days significantly decreased immobility period as compared to control mice. There was no significant difference in the antidepressant activity in animals administered with tramadol 40 mg/kg and imipramine 10mg/kg. Phentolamine effectively blocked the reduction in immobility duration by tramadol where as propranolol did not have significant effect on the antidepressant like action of tramadol in forced swim test in mice.