Sodium sensitivity of baroreceptors mediates reflex changes of blood pressure and urine flow

Abstract

CARDIOVASCULAR baroreceptors are sensitive to vascular pressures and their input to the central nervous system is essential for the regulation of arterial blood pressure. They also contribute to the regulation of extracellular fluid volume, because their reflex effects upon arterial pressure and renal blood flow have marked consequences for urine flow^1,2. Since they are mechanoreceptors their properties may be affected by sodium and potassium ions^3–5. Lowering extracellular Na⁺ (Na_o⁺) increases the threshold pressure at which arterial baroreceptors begin to discharge and reduces their sensitivity to suprathreshold pressures^6,7. We therefore investigated the reflex effects upon arterial blood pressure and urine flow elicited by lowering the Na_o⁺ of carotid sinus baroreceptors. We report that reductions in Na_o⁺ of as little as 5% increase arterial blood pressure and urine flow. We propose that the sodium sensitivity of baroreceptors is important for their function as regulators of arterial blood pressure and body fluid volume.