Changes in Mean Level and Stability of Arterial Blood Pressure after Bilateral Sectioning of the Carotid Sinus Nerves in Conscious Rabbits

Abstract

We previously reported the mean level and variability of mean arterial blood pressure (MAP) for 6 hrs in unanesthetized rabbits.The variability of MAP was significantly small, if MAP was in the normotensive range.This suggest that the carotid sinus and aortic arch baroreflex systems might powerfully control arterial blood pressure (AP) in a normotensive state.However, there are quantitative differences in responsiveness of the carotid sinus and aortic arch baroreceptors.The carotid sinus baroreceptor responds to change in AP above 50-60mmHg and functions most powerfully at around 100mmHg.The aortic arch baroreceptor initiates to respond to AP above 80-90mmHg and operates most strongly at 120-160mmHg. In a normotensive state, the carotid sinus baroreceptor is considered to contribute much to regulation of AP in comparison with the aortic arch baroreceptor.If the carotid sinus baroreflex does not function, AP could become unstable.
In the present study, effects of bilateral sectioning of the carotid sinus nerves on mean level and stability of MAP were examined in conscious rabbits.MAP recordings for 6 hrs were performed before and after sectioning the carotid sinus nerves.Mean value and standard deviation of MAP in carotid sinus denervated rabbits were compared with those in intact rabbits.