Third ventricular injection of hypertonic NaCl: effect of renal denervation on natriuresis

The natriuretic response to administration of various hypertonic solutions into the third cerebral ventricle of anesthetized dogs was investigated. Injection or infusion of hypertonic (0.85 M) NaCl into the third ventricle induced a moderate and transient natriuresis as well as an increase in the percent filtered load of Na⁺ excreted. There was an acute elevation of 10-20 mm Hg in mean arterial blood pressure following injection of hypertonic NaCl into the third ventricle. Following unilateral renal denervation, injection of hypertonic NaCl resulted in similar increases in sodium excretion and in the percent filtered load of Na⁺ excreted in both innervated and denervated kidneys. Isotonic NaCl, hypertonic choline chloride, and hypertonic glucose were without effect, indicating that the natriuresis was a specific response to the increased concentration of Na⁺ in cerebrospinal fluid.