Evaluation of analgesic activity by acetic acid-induced writhing test

The writhing test is an experimental procedure for inducing peripheral pain in mice by administering irritants such as acetic acid. The test compound’s analgesic efficacy is determined by a reduction in the number of writings.¹⁸ Twenty Swiss albino mice (weighing 20-30 g) were randomly taken and divided into four groups, each with five mice. Group I mice were given normal saline (10 mL/kg per body weight, orally), group II mice were given diclofenac sodium (50 mg/kg per body weight, orally) as a standard drug. In contrast, groups III and IV received methanolic extract (200 and 400 mg/kg per body weight, orally) as the sample. One hour after this treatment, 0.1 mL of 0.6% (v/v) acetic acid was administered intraperitoneally. The animal’s abdominal muscle writhing characterized by stretching with a twitch at the back limb was taken as writhing movement, which is an indicator of pain response. The number of writhing motions in individual mice was counted for 15 min after the acetic acid administration. The percentage inhibition of writhing was counted from the following equation:

Healthy Swiss albino mice of both sexes, 4-5 weeks old and 20-30 g weight, were used for the test. A positive control group was treated with diazepam (1 mg/kg i.p.), and the negative control group was administered with vehicle (10 mL/kg, normal saline orally). The test groups (groups II and III) received two different doses (200 and 400 mg/kg, respectively) of G. tetrandra leaf extract by oral administration. The following three methods evaluated the sedative-hypnotic activity: