BRONCHODILATOR ACTIVITY OF AN AQUEOUS FRACTION OF AN ETHANOL EXTRACT OF THE LEAVES OF CISSAMPELOS-SYMPODIALIS EICHL. (MENISPERMACEAE) IN THE GUINEA-PIG

The bronchodilator activity of an aqueous fraction (AF) of a 70% hydro alcoholic extract of the leaves of Cissampelos sympodialis Eichl. was evaluated in the guinea-pig. The AF inhibited the spontaneous tone of the trachea (IC50, 13.9 mu g/ml), which was potentiated (IC50, 4.6 mu g/ml) by 3-isobutyl-1-methylxanthine, blocked by beta(2) adrenoceptor blocking agent timolol, but unaffected by removal of epithelium or add ition of N-G-Nitro-L-arginine methyl ester or methylene blue. The AF a lso antagonized contractions induced by carbachol, capsaicin and arach idonic acid in normal trachea and by ovalbumin in trachea obtained fro m sensitized guinea-pigs. The IC50-values in these experiments varied from 34.1-70.5 mu g/ml. Further, the AF (100 mg/kg) by the more effect ive i.p. route increased the preconvulsive time of animals exposed to an aerosol of histamine to 63.5 +/- 5 s 1 h after administration compa red to 28 +/- 1 s in the untreated group. In addition, the AF at 100 m g/kg i.p. or i.G. protected the sensitized guinea-pigs against anaphyl actic shock induced by ovalbumin aerosol by 78.6 and 86.7% respectivel y.