antihistaminic effect of bunium persicum on guinea pig tracheal chains

in a previous study, the relaxant and anticholinergic (functional antagonism) effects of bunium persicum (b. persicum ) have been demonstrated on guinea pig tracheal chains. to elucidate the other mechanisms responsible for this relaxant effect, the inhibitory effect of this plant on histamine h1 receptors was examined in this study. the antihistaminic effects of aqueous and macerated extracts, essential oil, 20 nm chlorpheniramine, and saline were tested by performing the cumulative log concentration-response curves of histamine induced contraction of isolated guinea pig tracheal chains incubated with three different conditions including: 1) 1.4 µm indomethacin, 2) 1.4 µm indomethacin, 1 µm propranolol, and 10 nm atropine, and 3) 1.4 µm indomethacin and 1 µm propranolol (for each group n = 8). the results showed clear parallel rightward shifts in histamine-response curves obtained in the presence of macerated extract in group 2, aqueous extract in group 3, and essential oil in group 2 and 3 experiments compared with the curves obtained in the presence of saline. the ec50 (effective concentration of histamine causing 50% of maximum response) obtained in the presence of essential oil, extracts, and chlorpheniramine in all three sets of experiments were significantly higher than that of saline (p<0.05 to p<0.001), but maximum response to histamine obtained in the presence of essential oil and extracts were lower (p<0.01 to p<0.001). however, the maximum response obtained in the presence of aqueous extract in group 3 compared to group 1 and that of macerated extract in group 2 compared to the other two sets of experiments were improved. these results indicated a competitive antagonistic effect of b. persicum at histamine h1 receptors