Cirsium japonicum elicits endothelium-dependent relaxation via histamine H1-receptor in rat thoracic aorta

Cirsium japonicum De Candole is widely used in traditional herbal medicine for the treatment of hemorrhage, hypertension or blood circulation in Korea. In this work, we investigated the vasorelaxant activity of an aqueous extract of C. japonicum whole plant (CjEx) and its possible mechanism in isolated rat thoracic aortic rings constricted with norepinephrine (NE; 300 nmol/l). CjEx elicited an acute relaxation in endothelium-intact rings in a concentration-dependent manner (0.1–1.0 mg/ml). This relaxation was eliminated by the removal of the endothelium and pretreatment with NG-nitro-L-arginine (10 μmol/l), methylene blue (1 μmol/l) or diphenylhydramine (10 μmol/l), but indomethacin (10 μmol/l) atropine (100 nmol/l), [D-Pro2, D-Trp7,9] substance P (5 μmol/l) or HOE-140 (10 nmol/l) did not affect the relaxation. The results indicate that the response to CjEx involves enhancement of the nitric oxide-cyclic guanosine monophosphate system, and that it occurs via histamine H1-receptor. Our findings may contribute to better understanding of the potential link between the clinical use and its beneficial effects on vascular health.