AORTIC DISTENSIBILITY AND STRUCTURAL-CHANGES IN SINOAORTIC-DENERVATEDRATS

The purpose of the present study was to determine the effects of chron ic sinoaortic denervation on the mechanical properties and composition of the abdominal aorta in Wistar rats. We used a high-resolution echo tracking system to determine in situ under physiological conditions of blood flow and arterial wall innervation the aortic diameter-, compli ance-, and distensibility-pressure curves in 16-week-old anesthetized rats that had been denervated at 10 weeks of age for 6 weeks (n=8). Co mpared with sham-operated rats (n=8) we observed a marked reduction of baroreflex response and increase in overall mean blood pressure varia bility as measured by standard deviation and spectral analysis in sino aortic- denervated rats. Mean blood pressure was not affected by sinoa ortic denervation in both conscious and anesthetized rats. Sinoaortic denervation significantly shifted the distensibility-pressure curve to ward lower levels of distensibility, indicating a decreased aortic dis tensibility for a given level of arterial pressure. Sinoaortic denerva tion produced a significant increase of aortic wall cross-sectional ar ea and collagen content, one of the less-distensible components of the arterial wall. These results suggest that intact arterial barorecepto rs are necessary for maintaining normal functional and structural prop erties of large arteries in rats. The reduction in arterial distensibi lity in chronic sinoaortic-denervated rats may have resulted from diff erent factors, including the initial hypertensive phase, aortic wall h ypertrophy, and increase in collagen content. The changes in aortic wa ll structure and related reduction in aortic distensibility, in additi on to other mechanisms, might have been direct consequences of an incr eased blood pressure variability.