We used the neck chamber technique to study carotid baroreceptor control of blood pressure in 18 renovascular hypertensive subjects. Carotid baroreceptors were stimulated or deactivated for 2 minutes by applying graded reductions or increases in the neck tissue pressure (NTP) outside the carotid sinuses. The sensitivity of the baroreflex was separately calculated for these two conditions by the coefficients of the linear regressions relating the changes in NTP to the resulting changes in mean arterial pressure (MAP, catheter measurement). Baroreceptor deactivation increased MAP, and the sensitivity of the baroreflex was 0.12 /+- 0.07 in an early (5 to 1 seconds) and 0.32 /+- 0.05 in a late (90 to 120 seconds) phase of the stimulus application. Baroreceptor stimulation reduced MAP, and the baroreflex sensitivity was in this instance 0.66 /+- 0.08 and 0.05 /+- 0.08 respectively. Both these sensitivities were significantly greater than those obtained for the baroreceptor deactivation. These response entirely reproduced those of essential hypertensive subjects, but differed from those of normotensive subjects in whom baroreflex sensitivity was greater for carotid baroreceptor deactivation than for stimulation. Our findings indicate that carotid baroreceptor control of blood pressure undergoes a marked resetting in renovascular hypertension. The similarity of the baroreflex between renovascular and essential hypertension suggests as secondary origin of the resetting in man.
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