Acetic acid induced writhing test
The method of Collier et al (18) was adopted with slight modification. Adult Balb/c
albino mice weighing 20-30 g were used in this study. Animals were first pretreated with
either control (5% ethanol) or the extracts; PIL (10, 30, 100 and 300 mg/kg) via
peritoneum administration whilst for the standard drug, indomethacin was given
intraperitoneally at 10 mg/kg. Extract were administered 30 minutes before the
intraperitoneal injection of 0.15 ml/10 g body weight of 0.6% acetic acid to induce the
typical stretching response. Control animals received similar volume of the vehicle. As
described by Collier et al. (18) and Santos et al. (19), abdominal constriction known as
writhing reflex was induced by 0.6% acetic acid was observed on the abdominal muscle
together with a stretching of hind limb.
After induction, pairs of mice were placed in separate boxes and the writhings or
stretchings per animal were counted for a period of 5 minutes under a double blind
observation for the duration of 15 minutes. The antinociceptive effect was measured by
calculating the mean reduction in the number of abdominal constriction for each extract
as compared with the control group. The evaluation of antinociceptive activity was
expressed as inhibition or reduction percentage of the number of total abdominal writhes