Analysis of hemodynamic variability after sinoaortic denervation in the conscious rat.

The present study was undertaken to determine the regional hemodynamic basis for increased mean arterial pressure (MAP) variability produced by sinoaortic baroreceptor denervation (SAD) in the conscious rat. Sinoaortic-denervated and intact rats were instrumented chronically with a catheter placed in the femoral artery and pulsed-Doppler flow probes positioned on the renal and superior mesenteric arteries and the lower abdominal aorta to determine MAP, heart rate, and regional vascular resistance. Each cardiovascular variable was sampled once per minute during a 1-h recording period. Compared with control animals, baroreceptor-denervated animals exhibited greater variability of MAP and mesenteric, renal, and hindquarter resistances 7-9 days after SAD. The variability of heart rate was similar when animals from the two groups were compared. The pattern of significant correlation for the relationship of MAP to vascular resistance in the different beds was not consistent for individual SAD and intact animals. Finally, a wider distribution of mean values was observed for the individuals within the SAD group for MAP, heart rate, and hindquarter and renal vascular resistances. We conclude that SAD produces greater fluctuation of vascular resistance in several beds which contributes to the increased lability of MAP; however, there is no predictable pattern of vascular resistance lability which underlies the variability of arterial pressure.