bronchodilatory and an ticholinergic effects of carum copticum on isolated guinea pig tracheal chains

carum copticum is a grassy and annual plant which is believed to have several therapeutic effects, including anti-asthmatic properties. we have therefore studied the bronchodilatory and anticholinergic effects of 4 rnl aqueous extract (ae), 0.0 5 ml ethanol extract (ee), and 0.0 0 5 ml essential oil (eo) of carum copticum and 1 rnl of a 5 mm solution of its main ingredient, thymol (t), in comparison with 4 ml of saline (s) on isolated tracheal chains of guinea-pigs (w=500-800 g) in a 50 ml organ bath. the bronchodilatory effects of different solutions were examined by their relaxant effect on isometrically (1 g) precontracted tracheal chains by 10 µm methacholine (m). the anticholinergic effects of different solutions were tested by comparing the cumulative log concentration -response curves of tracheal chains to cumulative concentrations of m in the presence of ae, ee, eo, and t with that of s. the bronchodilatory effects of ae, ee, and eo were significantly higher than s in all cases (p<0.00 1), but t did not show any significant bronchodilatory effect. there were also significant right-ward shifts in cumulative log concentrationresponse curves obtained in the presence of ae, ee, and eo in comparison with the curve obtained in the presence of s. thymol also caused a smaller right-ward shift in the m cumulative log concentration-response curve . however, the slopes of methacholine response curves obtained in the presence of ae, ee, eo (p<0 .00 l ), and t (p<0.05) were significantly lower than that of s, indicating the functional antagonistic effects of these solutions. these data showed the presence of bronchodilatory effects of ae, ee, and eo of carum copticum which was not due to the presence of t or the existence of a competitive antagonist at the muscarinic receptors in this plant.