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The antinociceptive activity of the methanolic extract of Neorautenania mitis was studied in mice and rats. Five experimental models of nociception employed were: acetic acid-induced abdominal constriction and hot-plate test in mice, formalin-induced pain, analgesy-meter and Randall-Selitto tests in rats. The antinociceptive action of the extract was tested against naloxone in the hot-plate test in a bid to further elucidate probable mechanisms of antinociception. Results showed that the extract at doses of 5, 10 and 20 mg/kg body weight caused significant (P<0.05) dose-dependent antinociceptive activity in all the nociceptive models. Naloxone (2 mg/kg), significantly (P<0.05) antagonised the antinociceptive activity at the highest dose of the extract (20 mg). The study showed that the methanolic extract of Neorautanenia mitis possesses both peripherally and centrally mediated antinociceptive activity. The peripherally mediated action may be linked partly to lipoxygenases and/or cyclo-oxygenases, while the central anti-nociception is likely to be mediated via opioid receptors in the CNS.

The methanolic extract of the stem bark of Parinari polyandra (family Rosaceae) was investigated for possible anti-nociceptive and anti-inflammatory effects in mice and rats. Three models were used to study the extracts effects on nociception which were the acetic acid-induced abdominal constriction test, hot-plate method (both in mice) and the formalin test in rats. The anti-inflammatory effects were investigated employing the albumin-induced hind-paw oedema in rats. Results of the study revealed the extract to have significant (P<0.05) anti-nociceptive effect at a dose of 200 mg/kg p.o. in mice and rats in all the models for anti-nociception while 100 mg/kg p.o. showed significant (P<0.05) effect in the acetic acid-induced abdominal constriction test and in phase I of the formalin test. The extract also exhibited anti-inflammatory effects which were found to be significant (P<0.05) at 200 mg/kg p.o. in the rats tested. Preliminary phytochemical screening of the extract showed the presence of flavonoids, tannins, and saponin glycoside. The results suggest the extract contains pharmacologically active principles. The result is in agreement with the local application of the plant in painful and inflammatory conditions.