Analgesic modulation of tramadol, amitriptyline and gabapentin in male and female wistar rats

The central and peripheral analgesic response of tramadol, amitriptyline and gabapentin in male and female Wistar rats was measured using hot plate, tail-flick and acetic acid-induced writhing tests. In the first two methods withdrawal latency was measured at baseline and after administration of either tramadol (10 mg/kg, i.p.) ,amitriptyline (10 mg/kg, i.p.) or gabapentin (50 mg/kg, i.p.) at 15, 30, 60 and 120 minutes. In acetic acid induced writhing method, same drugs were given to both sex groups and then after 30 minutes, 2% acetic acid (2ml/kg, i.p.) was given and after 10 minutes number of writhes were counted.Tramadol showed significantly higher pain threshold in male rats than the female rats in response to hot plate test, tail-flick test and acetic acid induced writhing test. Amitriptyline treated male rats showed significantly higher pain threshold than the female rats in response to tail-flick method only. There was less number of writhing movements in gabapentin treated male rats as compared to female rats.The three drugs show different response in male and female rats. However, in some models there was no gender difference.