一氧化氮及去内皮对颈动脉窦压力感受器活动的影响

EFFECTS OF NO AND ENDOTHELIUM ON CAROTID BARORECEPTOR ACTIVITY

本实验应用自制的颈动脉窦（CS）窦内脉动灌流-窦外表面灌流的双重灌流装置，研究了外源性一氧化氮（NO）及内皮对家兔离休CS压力感受器活动（BRA）的影响，并进一步探讨其作用机制。实验表明：（1）在脉动式灌流的条件下，卖神经（CSN）传入纤维基础放电中的高幅值放电呈现显著的对脉动式灌流的依赖性和对灌流压（平均压）依赖性，而对经典的化学感受器刺激无反应，这些放电特征证明其来自CS压力感受器；（2）去除血管内皮后，压力感受器活动减少；（3）外源性NO（L-精氨酸）可明显增加压力感受纤维的放电，这种作用可被NO合成抑制剂或去除内皮所阻断；（4）鸟苷酸环化酶（GC）抑制剂亚甲蓝不仅对基础条件下的BRA没有影响，也不影响外源性NO对BRA的兴奋作用。结果证明：外源性NO对CS-BRA有明显的兴奋作用，这种作用有赖于内皮的完整性，其作用不是由cGMP介导的。

The present study was undertaken to examine the effects of endothelium and exogenous NO on the baroreceptor discharge of the carotid sinus. The baroreceptor activity (BRA) was recorded from the rabbit carotid sinus-sinus nerve (CS-CSN) preparation using a chamber for superfusing and perfusing the tissue. The results are as follows. (1)The CSN hasal discharge could be divided into two components, a low-amplitude component and a high-amplitude one. The high-amplitude discharge was dependent on pulsatory perfusing pressure, but did not respond to classical chemoreceptor stimulants,indicating its baroreceptive origin. (2) The BRA was decreased after removal of the endothelium. (3 ) L-arginine (L-arg), as exogenous NO, initiated BRA in a dosedependent manner, which was prevented by precedent inhibition of NO synthase or by removalof the endothelium. (4) Inhibition of guanine nucleotide cyclase with methylene blue effected neither the hasal BRA nor the response of BRA to L-arg. These results indicate that stimulation of BRA by exogenous NO may be mediated by the endothelium,but cGMP dose not seem to be involved.