ABSTRACT
Background: The leaves of Origanum are widely used in herbal medicine hence of having many beneficial ingredients, one of these important compounds is Carvacrol. The inhibitory effect of Carvacrol was the core of this study by applying different kinds of stimulants to smooth muscles in the wall of thoracic aorta in rats. Aim: To investigate the pharmacological effects of Carvacrol, the main active ingredient present in the medicinal plant Origanum, on the contractile activity and morphology of the smooth muscle of the rat thoracic aorta. Materials and Methods: After the thoracic aorta arteries were isolated and prepared for the experiments, each thoracic aorta was cut into 5-mm ring segments; different stimulants were used (Potassium Chloride, Norepinephrine, U46619, and α,ß-methylene ATP) in the presence and absence of Carvacrol on four groups of rats. The isolated rings were placed and connected to a force transducer which in turn linked to a data acquisition system via an amplifier to record the effect of each stimulant. GraphPad Prism version 5.02 for Windows, one-way analysis of variance followed by Dunnett's multiple comparison test. Results: It was found out that Carvacrol obstructs the contractile responses elicited by exogenous NA, KCl, U46619, and α,ß-methylene ATP in a concentration dependent manner. Conclusion: The addition of Carvacrol in the experimental rats showed an increase in the thickness of tunica media as evident by the number of smooth muscle layers and laminae of elastic fibers. It was found that Carvacrol reduced the vascular smooth muscle contractility in the rat thoracic aorta. The mechanism of action is presumed to be achieved through interfering with the mobilization of both intracellular and extracellular Ca2+ through different receptors. Furthermore, it might be suggested that Carvacrol in high doses stimulates smooth muscles in the wall of aorta leading to an increase in the thickness of tunica media layer.
