Modulation of the carotid baroreflex function during volume expansion

Publisher Website
Google Scholar
Abstract
In anesthetized rabbits, the carotid sinuses were vascularly isolated to obtain the open-loop relationship between intrasinus pressure (ISP) and systemic arterial pressure (SAP). The ISP-SAP curve was divided into 2 portions: ISP of 50-100 and 100-150 mm Hg. The values of carotid baroreflex (CBR) loop gain (.DELTA.SAP.DELTA.ISP) calculated from these 2 components were denoted Gain50-100 and Gain100-150, respectively. The effects of volume expansion (VE) and the respective role of vagal afferents (VA) and aortic nerves (AN) on the CBR sensitivity were evaluated by comparing the values of gain determined under different conditions. In aortic-denervated and atropinized rabbits, tonic VA activity did not affect the CBR Gain100-150, but reduced the Gain50-100 by 15.8%. VE, sufficient to raise the right atrial pressure by 10 cmH2O, also did not change the CBR Gain100-150, but reduced the Gain50-100 by 52.1%. The attenuation effect of VE on the CBR Gain50-100 was abolished after cervical vagotomy. In another group of vagotomized rabbits, AN in the absence of VE reduced the CBR Gain50-100 and Gain100-150 by 49.6% and 18.9%, respectively. VE did not alter the AN effect on Gain50-100. A 3-fold increase in the AN effect on the Gain100-150 was observed during VE. The vagal and aortic afferents are apparently responsible for the modulatory effect of volume expansion on the carotid baroreflex function within different range of the ISP-SAP curve.