银杏苦内酯B抑制麻醉大鼠颈动脉窦压力感受性反射

本研究在30只麻醉雄性Sprague-Dawley大鼠隔离灌流颈动脉窦区观察了银杏苦内酯B(ginkgolide B)对颈动脉窦压力感受性反射的影响.结果显示:(1)银杏苦内酯B(0.1,1,10 pmol/L)隔离灌流序侧颈动脉窦区,使压力感受性机能曲线向右上方移位,曲线最大斜率(peak slop,PS)减小,血压反射性下降(reflex decrease,RD)幅度减小(P<0.01),阂压(threshold pressure,TP)、平衡压(equilibrium pressure,EP)和饱和压(saturation pressure,SP)均升高(P<0.05,P<0.01).其中PS、RD、TP、EP和sP呈明显的剂量依赖性;(2)预先应用钙通道开放剂Bay K8644(500 nmol/L),可以完伞取消银杏苦内酯B的抑制作用.(3)预先应用钾通道阻断剂四乙铵(tetraethylammonium,TEA,1 mmol/L),银杏苦内酯B的上述作用也被完全取消.结果表明,银杏苦内酯B对大鼠颈动脉实压力感受性反射有抑制作用,此作用与银杏苦内酯B减少颈动脉窦压力感受器神经末梢钙离子内流和增加钾离子外流有关.

Ginkgolide B inhibits carotid sinus baroreflex in anesthetized male rats

The effects of ginkgolide B on the carotid sinus baroreflex (CSB) were studied in the perfused isolated carotid sinus of 30 anesthetized Sprague-Dawley male rats. The results were as follows. (1) By perfusing with ginkgolide B (0.1, 1, 10 mumol/L), the functional curve of the baroreflex was shifted to the right and upward. There was a marked decrease in peak slope (PS) and reflex decrease (RD) in mean arterial pressure (P<0.01), while the threshold pressure (TP), equilibrium pressure (EP) and saturation pressure (SP) were significantly increased (P<0.05, P<0.01). Among the functional parameters of CSB, the changes in PS, RD, TP, EP and SP were dose-dependent. (2) Pretreatment with Bay K8644 (500 nmol/L), an agonist of L-type calcium channel, completely eliminated the effects of ginkgolide B (1 mumol/L) on the CSB. (3) Pretreatment with tetraethylammonium (TEA, 1 mmol/L), an inhibitor of potassium channel, completely abolished the above effects of ginkgolide B (1 mumol/L) on the CSB. These results suggest that ginkgolide B inhibits the CSB in anesthetized rats, which is mediated by decreased calcium influx and increased potassium efflux in baroreceptor nerve endings.