Analgesic Activity of the Methanol Leaf Extract of Delonix Regia

The analgesic activity of the methanolic leaf extract of Delonix regia in albino Wistar mice using acetic acid –induced writhing reflex, tail immersion and hot plate experimental models was evaluated. Three test doses (200, 400 and 800 mg/kg body weight) of the extract were used while 400 mg/kg of acetylsalicyclic acid (aspirin) was used as reference drug all administered by gastric gavage. In acetic acid-induced writhing reflex model, the extract and acetylsalicyclic acid dose dependently and significantly (p< 0.0001) decreased the abdominal constriction or writhing. The extract also increased the percentage inhibition of abdominal constriction from 0% in the negative group to 80% in the highest dose of the extract (800 mg/kg) treated group. In the tail immersion model, the extract at the doses of 400 and 800 mg/kg significantly (p<0.03) increased the pain reaction time (PRT) while in the hot plate model there was no significant difference in the pre-drug pain reaction time (PRT) but the extract at the dose of 800 mg/kg significantly (p< 0.05) increased the post- drug PRT. In the tail immersion and the hot plate models, the extract at the dose of 200 mg/kg had no analgesic effect. In conclusion, the methanolic leaf extract of Delonix regia demonstrated significant analgesic activity that may be mediated through peripheral and central mechanisms.Keywords: Delonix regia, analgesic, aspirin, writhing, hot plateNigerian Veterinary Journal, VOL:33 (2) 515-52