stimulatory effect of carum copt/cum on β2 adrenoceptors of isolated guinea pig tracheal chains

the β2-adrenergic effects of macerated extract, aqueous extract, ethanol extract, and essential oil of carum copticum, 5 nm propranolol, and saline were tested by performing cumulative log concentration-response curves of isoprenaline-induced relaxation of precontracted isolated guinea pig tracheal chains in three different conditions including: non-incubated (group 1, n=9) incubated with 1 µm chlorpheniramine and 1 µm atropine (group 2, n=8) and incubated with 1 µm chlorpheniramine (group 3, n=6). the effective concentration of isoprenaline, causing 50% of maximum response (ec50), the maximum response, and the slope of isoprenaline curves obtained in the presence of extracts, essential oil, and propranolol were compared with those of saline. the results showed clear leftward shifts in isoprenaline curves obtained in the presence of only the ethanol extract compared with those of saline in group 1. in groups 2 and 3 the same finding was observed, although the effect of ethanol extract was tested in the presence of propranolol. the ec50 and maximum response obtained in the presence of ethanol extract were similar to those of saline in all three sets of experiments. however, the maximum response obtained in the presence of other extracts, essential oil, and even propranolol were lower than those for saline in all sets of experiments (p<0.05 to p<0.001). the ec50s obtained in the presence of essential oil, macerated and aqueous extracts, and even propranolol were greater than those obtained in the presence of saline in the two last sets of experiments (p<0.05 to p<0.001). the maximum response obtained in the presence of only ethanol extract in group 3 compared to group 2 was reduced (p<0.05). the results of this study indicate a stimulatory effect of only the ethanol extract of carum copticum on β2-adrenoceptors.