Relaxant Effects of Carvacrol on Guinea Pig Tracheal Chains and Its Possible Mechanisms

The bronchodilatory effects of three cumulative volumes (0.02, 0.04, and 0.08 ml) of 1/100 diluted carvacrol were examined by their relaxant effects on tracheal chains of guinea pigs precontracted by 60 mM KCl (group 1) and 10 microM methacholine in two different conditions including: non-incubated tissues (group 2) and incubated tissues with 1 microM propranolol and 1 microM chlorpheniramine (group 3), (for each group, n = 5). The relaxant effects of all three volumes of carvacrol were significantly higher than those of ethanol and even theophylline in all three groups of experiments (p < 0.05 to p < 0.001). There were positive correlations between the relaxant effect of carvacrol and incremental volume (p < 0.05 to p < 0.001). These results indicated that carvacrol has a potent relaxant effect on tracheal chains of guinea pigs which is not due to beta2-adrenergic stimulatory, histamine H1, and muscarinic blocking effect.