Brain involvement in the regulation of renal sodium excretion.

The aim of the present work was to study some aspects of the brain involvement in renal sodium excretion from the point of view of renal regulation of the extracellular fluid volume and composition. It was found on the basis of experiments on conscious sheep that sodium concentration in the cerebrospinal fluid may be of importance for the mechanism of the extracellular fluid volume regulation. Higher concentrations potentiate a homeostatically effective natriuresis during extracellular fluid volume expansion and lower concentrations impair natriuresis. It was also found in sheep with lesions of the anterior third cerebral ventricle that this brain region is of crucial importance for the mechanism of natriuresis evoked by an i.v. hypertonic saline load but the regulation of the extracellular fluid volume is undisturbed provided the sheep is kept in water balance. Finally it was demonstrated in anesthetized dogs that the heart atrial natriuretic system may be under control of both the extracellular fluid volume and plasma osmolality (and/or plasma sodium concentration) and a circumstantial evidence was provided that it may also be under the control of a cerebral function.