A central osmosensitive receptor for renal sodium excretion.

1. The effect on renal Na and water excretion of increasing the NaCl concentration of blood supplying the brain was investigated in conscious water-loaded sheep. Intracarotid infusion ot 4 M-NACl at 0-8 ml./min for 60 min was compared with equivalent intrajugular infusion. 2. A more rapid increase in renal Na excretion and urine osmolality occurred with the intracarotid infusions than with intrajugular infusions. 3. Intracarotid infusions of 2 M sucrose or fructose at 1-6 ml./min for greater increase in renal Na excretion, urine osmolality and a decrease in urine flow rate. 4. The results suggest that there are receptors in the brain sensitive to changes in extracellular tonicity which influence renal Na excretion. It is possible that changes in ADH secretion alone mediate the early natriuresis seen with intracarotid hypertonic infusions although an alternative concurrent mechanism cannot be ruled out.