Vasorelaxation effect of oxysophoridine on isolated thoracicc aorta rings of rats

Oxysophoridine (OSR) is a main active alkaloid extracted from Sophora alopecuroides, which is a traditional Chinese herbal medicine that has been used widely. In this study, we used thoracic aorta rings isolated from Sprague-Dawley rats to explore the vasodilative activity of OSR and its potential mechanisms. The isolated rat thoracic aorta rings were used to observe the effects of different concentrations of OSR (0.4-2.0 g·L-1) on the resting normal rings and the phenylephrine precontracted endothelium-intact or endothelium-denudedisolated thoracic aorta rings, respectively. The interactions among OSR and barium chloride (BaCl2), tetraethylamine, 4-aminopyridine, glibenclamide (Gli), L-nitroarginine methyl ester (L-NAME), and cyclooxygenase (COX) inhibitor indomethacin (INDO) were evaluated. The experimental results show that OSR had no effect on the tension of resting vascular rings, but the vasodilating effect could be confirmed in a concentration-dependent manner on both endothelium-intact and endothelium-denuded vascular rings. This vasodilation effect of OSR on thoracic aorta vascular rings could be inhibited significantly by potassium channel blockers glibenclamide (Gli, 10 μmol·L-1) and 4-aminopyridine (4-AP, 5 mmol·L-1). In addition, vasodilatory effects of OSR were not inhibited in the presence of potassium channel blockers barium chloride (BaCl2, 1 mmol·L-1) and tetraethylamine (TEA, 10 mmol·L-1), nitric oxide synthase inhibitor (L-NAME, 0.1 mmol·L-1) and COX inhibitor (INDO, 10 μmol·L-1). In conclusion, the vasodilatory effects of OSR on thoracic aorta rings is associated with KV and KATP.