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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 leaves of Cassia tora Linn. (Family: Caesalpiniaceae) were soxhlet extracted with methanol. The spasmogenic effects of the extract were evaluated on guinea pig ileum, rabbit jejunum and mice intestinal transit. Antinociceptive activity of the extract was also evaluated in the mice. The LD(50) values of the extract in mice were >2000 mg/kg i.p. and p.o. The extract contracted smooth muscles of guinea pig ileum and rabbit jejunum in a concentration-dependent manner. Atropine reversibly blocked this activity. Mepyramine also reduced the contractile amplitude due to the extract in a concentration-dependent manner. The extract increased intestinal transit in mice dose dependently. C. tora extract significantly (P<0.05) reduced the number of acetic acid induced abdominal constrictions in mice and the effect was comparable to that of aspirin (150 mg/kg i.p.). The extract also significantly (P<0.05) reduced the nociceptive response of mice to increased force (g). The effects were dose-dependent. The studies suggest that the use of C. tora, traditionally, as a purgative and in the treatment of other ailments is justifiable.