BRONCHODILATORY AND ANTICHOLINERGIC EFFECTS OF CARUM CARVI ON ISOLATED GUINEA PIG TRACHEAL CHAINS

Carum carvi (CC) is a grassy plant which is believed to have several therapeutic effects, including anti-asthmatic properties. We have therefore studied the bronchodilatory and anticholinergic effects of this plant. The bronchodilatory effects of the aqueous extract (AE), macerated extract (ME), essential oil (EO), and 4µM theophylline (T) in comparison with saline (S) were examined by their relaxant effects on precontracted [by 10 µM methacholine (M)] isolated tracheal chains of guinea pigs (n=1O). The anticholinergic effects of AE, ME, EO, and 5 nM atropine (A) were tested by comparing the cumulative Log concentration-response curves (LCRCs) of Minduced contraction of tracheal chains and the effective concentration of M causing 50% of maximum response (EC50) in the presence of AE, ME, EO, and A with that of S. Although the bronchodilatory effects of AE, ME, and EO were lower than that Of T (p<0.001 for all cases), they were significantly higher than the effect of S (p< 0.05 for AE, p<0.01 for ME, and p<0.005 for EO). There were also clear nonparallel right-ward shifts in LCRCs obtained in the presence of AE, ME, and EO, but a parallel shift in the presence of A compared to the curve obtained in the presence of S. The slope of LCRCs obtained in the presence of AE, ME, and EO were significantly lower than that of S (p<O.OI for AE, p<0.05 for ME, and p<0.001 for EO). The ECso obtained in the presence of AE (p<0.005), ME (p=O.005), EO (p<0.02), and A (p<0.001) were significantly higher than that of S. However, the EC50 values obtained in the presence of AE, ME, EO and dose ratio (DR-I) produced by ME were not significantly different from that of A. The LCRCs obtained in the presence of EO on incubated tracheal chains with 1µM propranolol and 1 µM chlorpheniramine also showed a clear non-parallel rightward shift comparing with that of S. However, the slope of this curve was significantly higher than that of non-incubated experiments (p<0.05). The results of this study indicated that the bronchodilatory effect of Carum carvi is mainly due to the non-competitive antagonistic property of this plant at muscarinic receptors. The β stimulatory effect and/or anti-histaminic effect of EO might be contributed to its non-competitive property. The variation between anticholinergic behaviours of different extracts is probably due to the variation of methods used, leading to extraction of different substances or destruction of some substances due to high temperature.