Time Course and Extent of Carotid Sinus Baroreceptor Threshold Resetting in Rats with Renovascular Hypertension

Abstract

To study the extent and time course of arterial baroreceptor threshold resetting to increases in blood pressure, renal hypertension was induced in young normotensive male Wistar rats by unilateral renal artery constriction. At different intervals after operation the extent of baroreceptor threshold resetting in the carotid sinus was examined. Experiments were performed 7, 14 and 25 days after renal artery clipping to enable baroreceptor resetting to be correlated with the rate and extent of cardiovascular changes in rats which had renovascular hypertension of identical durations. Baroreceptor thresholds in the carotid sinuses were established by progressive clamping of both carotid arteries after partial vascular isolation of the sinuses. The results show that after 1 wk of hypertension baroreceptor resetting is only just apparent but by two weeks resetting is gross and seems to be largely completed. This parallels the adaptive changes in the hindquarters of renal hypertensive rats and it is concluded that baroreceptor resetting is a secondary phenomenon related to the structural changes induced in the vessels by the elevated blood pressure.