Zataria multiflora Boiss and Carvacrol Affect β2‐Adrenoceptors of Guinea Pig Trachea

The stimulatory effect of Zataria multiflora Boiss (Labiatae) and carvacrol on β-adrenoceptors was examined on guinea pig trachea. The effects of three concentrations of aqueous-ethanolic extract, carvacrol, and propranolol (β-receptor antagonist) on β-adrenoceptors were tested in nonincubated (group 1, n = 8) and incubated tracheal chains with 1 μM chlorpheniramine (histamine H1 receptor antagonist) (group 2, n = 5). Isoprenaline (β-receptor agonist) curves obtained in the presence of all concentrations of the extract and carvacrol showed leftward shifts compared with that of saline in both groups. In both groups, the EC50 (the effective concentration of isoprenaline, causing 50% of maximum response) obtained in the presence of all concentrations of the extract and carvacrol was significantly lower compared to that of saline (P < .01 to P < .001). All values of (CR-1: (EC50 in the presence of active substances/EC50 obtained in the presence of saline)-1) obtained in the presence of concentrations of the extract and carvacrol in both groups were negative and significantly different from that of propranolol (P < .001 for all cases). The results indicated a stimulatory effect of Zataria multiflora Boiss extract on β(2)-adrenoceptors which is perhaps due to its constituent, carvacrol.