Effect of Posterior Hypothalamic Lesions on Renal Function in the Rat

Abstract

Female Wistar rats were infused with an isotonic solution (110 mM NaCl + 25 mM NaHCO3) containing 5 mU of Pitressin per milliliter, at a nonexpanding rate of 0.016 ml/min. Per-corten (1.25 mg i.m.) was given 1 h before the experiment. Urine flow rate, sodium and potassium excretion, and creatinine clearance were measured over 20-min periods. After the control values were obtained, bilateral electrolytic lesions were made in the posterior hypothalamus or the lateral hypothalamic area. Another group of rats was sham operated, and in controls an equivalent current was passed through the body. Posterior hypothalamic lesions were immediately followed by significant increases in the urine flow rate, UNa, and UNaV. Creatinine clearance increased insignificantly. However, the significant decrease of the fractional sodium reabsorption indicated that the natriuresis was mainly of tubular origin. This diuresis and natriuresis were not associated with significant changes in the arterial blood pressure. Changes were still detectable 60 min after lesioning, but were returning to control levels. No changes in renal function followed lesions in the lateral hypothalamus, sham operation, or application of electric current. The role of the posterior hypothalamus in the renal excretion of sodium is discussed.