Effect of Subchronic Administration of Aqueous Artemisia annua Extract on a1-Adrenoceptor Agonist-Induced Contraction of Isolated Aorta in Rat

Artemisia species, growing in almost all the northern hemisphere, is used in folk medicine of some countries as a remedy for hypertension. Since some cardiovascular disorders including hypertension are accompanied with altered responsiveness of vascular alpha-adrenergic receptors, the effect of aqueous Artemisia annua extract (100 and 200 mg kg-1) on a1-adrenoceptor agonist-induced contraction of rat aorta was investigsted. After 4 weeks, the contraction and endothelium-dependent and -independent relaxation response of extract-treated rats were recorded. The results showed that the contractile response of aortic rings with endothelium to phenylephrine in extract-treated rats decreases (P<0.01-0.0001) and their endothelium-dependent relaxation response to acetylcholine increases (P<0.01-0.001) significantly in comparison with controls. Endothelium-denuded aortic rings from extract-treated rats also showed a significant decrease (P<0.05) in contractile response, but there was no considerable difference in their endothelium-independent relaxation response to isosorbide dinitrate. These data suggest that the aqueous extract of Artemisia annua could attenuate contractile response and enhance the endothelium-dependent relaxation response of aortic rings from normal rats