Study on Vasorelaxant Mechanism induced by Extract of Zanthoxylium piperitum Leaves

Abstract

A methanol extract of Zanthoxylium piperitum (MZP) Leaves relaxed vascular smooth muscle in rats. Therefore, the aim of the present study was to define the mechanism of the MZP‐induced vascular relaxation in rat thoracic aorta. Among the four solvent partitions of MZP, n‐butanol (BZP) and water extract (WZP) of Zanthoxylium piperitum Leaves induced relaxation of the phenylephrine‐precontracted rat aorta in a dose‐dependent manner, respectively, and its effects were both abolished by the removal of functional endothelium. Pretreatment of the endothelium‐intact aortic tissues with NG‐nitro‐L‐arginine methyl ester (L‐NAME) and 1H‐[1,2,4]‐oxadiazole‐[4,3‐α]‐quinoxalin‐1‐one (ODQ) inhibited the relaxation induced by BZP and WZP, respectively. On the other hand, vascular relaxation induced by BZP or WZP were not blocked by several inhibitors including indomethacin, atropine, propranolol, tetraethylammonium (TEA), glibenclamide, verapamil, and diltiazem, respectively. In addition, phenylephrine or epinephrine‐induced aortic contraction was also blocked by treated with BZP and WZP, respectively. These results suggest that BZP and WZP dilate vascular smooth muscle via endothelium‐dependent nitric oxide/cGMP signaling pathway.