Reflex Control of Blood Pressure by the Right Subclavian Baroreceptor in Experimental Renal Hypertension of Rabbit

Abstract

The reflex control of systemic blood pressure by the right subclavian baroreceptor was studied in normal and hypertensive rabbits anesthetized with α-chloralose, and the following findings were obtained.
(1) In both normal and hypertensive rabbits, a relationship between raising perfusion pressure and decrease in systemic blood pressure, showing sigmoid blood pressure to perfusion pressure-response curve, was obtained.
(2) In control rabbits, the threshold of the vasodepressor response was 20.0±8.2mm.Hg; the perfusion pressure at the upper limit and the middle point of the maximum sensitivity area of the curve were 118.2±13.6mm.Hg and 81.3±11.2mm.Hg respectively; and the maximum fall of systemic blood pressure was 24.4±8.4mm.Hg. The average mean systemic pressure of control rabbits was 86.6±10.6mm.Hg, and thus nearly coincident with the perfusion pressure of the middle point.
(5) The curves obtained during infusion of angiotensin II was nearly coincident with that obtained before infusion.
(4) In 4 cases of renal hypertensive rabbits within 2 weeks, the curves shifted to lower pressure levels in parallel with that of control rabbit. In 6 cases from 3 to 4 weeks' duration, the curves were found at control level. In 4 cases of 5 weeks, the curves shifted to higher levels than control. In 6 cases over 5 weeks' duration of hypertension, the curves shifted to more higher pressure levels and the middle point of the maximum sensitivity area was nearly coincident with the average mean systemic pressure of hypertensive phase. In 4 treated cases without hypertension, the curves were found at control level.
In conclusion, the right subclavian baroreceptor was reset at higher arterial pressure levels over 4 weeks' duration in experimental renal hypertension of rabbit.