Use of sinoaortic denervation to study the role of baroreceptors in cardiovascular regulation

To assess the role of arterial baroreceptors in cardiovascular regulation, many studies have used rats in which baroreceptor afferents have been surgically destroyed. However, interpretation of studies using sinoaortic- denervated (SAD) rats is complicated by variability in the extent of baroreceptor denervation. We have compared cardiovascular regulation in rats with total sinoaortic denervation, as assessed by the abolition of reflex changes in heart rate (HR) to increases and decreases in arterial pressure (AP), with rats that underwent the same denervation procedure but still had residual (although markedly blunted) reflex changes in HR to changes in AP. In totally SAD rats, the lability of AP was greatly exaggerated compared with sham-denervated rats, although the average AP was equivalent. In contrast, partially SAD rats had elevated AP, and although AP was more labile than in sham-denervated rats, it was less labile than in totally SAD rats. In addition, cardiovascular responses elicited by elimination of neural activity in the nucleus tractus solitarius (NTS) were qualitatively different between the two groups of rats; destruction of the NTS increased AP similarly in partially SAD rats and sham-denervated rats, whereas this treatment did not alter AP in totally SAD rats. Thus there are marked differences in SAD rats with no residual arterial baroreceptor reflex function compared with SAD rats with even a small degree of residual baroreceptor reflex function. These studies highlight the importance of carefully characterizing SAD rats used in studying the role of the baroreceptor reflex in cardiovascular regulation.