Evidence for a Hypothalamic Control of Renal Sodium Excretion

Abstract

Slow infusions (7.5 μl/min) of hypertonic NaCl into the 3rd brain ventricle of goats maintained on a NaCl‐supplemented diet provoked natriuresis reaching maximum about 70 min after onset of the infusions. The natriuresis was less pronounced in animals receiving no dietary NaCl‐supplementation. The magnitude of the natriuretic response was dependent on the molarity of the NaCl infused and on infusion duration. A much smaller relative increase in K excretion, reaching peak values 20 min before maximum natriuresis, also occurred. Aldosterone treatment did not prevent the natriuretic response and it could be elicited in diabetes insipidus animals, showing that release of posterior pituitary hormones was not essential. Determinations of inulin clearance (CIn) indicated that glomerular filtration rat (GFR) increased and that relative reabsorption of Na+ decreased during the natriuresis. Similar intraventricular infusions of hypertonic NH4Cl resulted in greatly diminished renal Na+ excretion lasting for about 2 hrs. Such infusions also delayed by 90 min the normal natriuretic response to an intravenous NaCl load. CIn determinations indicated that a diminished GFR may have contributed to this reduction in renal Na+ excretion. The results indicate that renal Na+ excretion is under hypothalamic control in the goat. Possible mechanisms for this control are discussed.

Chronic cerebroventricular infusion of hypertonic sodium chloride in rats reduces hypothalamic sympatho-inhibition and elevates blood pressure.

“…In conscious goats, icv infusions of hypertonic saline increased renal sodium excretion (Andersson et al, 1969), and the resulting negative sodium balance could contribute to the effects described here. In some rats, we found body weight substantially reduced while 24-hour water intake and urine volume were increased during icv infusions of hypertonic NaCl (unpublished data), but whether or not these changes are related to the blood pressure elevation is unknown.…”

Altered renal sodium handling in spontaneously hypertensive rats (SHR) after hypertonic saline intracerebroventricular injection: Role of renal nerves

“…Many investigators, studying mammalian species, have demonstrated that administration of hyperosmotic saline into the cerebral ventricles elicit a large increase in renal sodium excretion (Andersson et al, 1969;Dorn et al, 1969;Chiu and Sawyer, 1974;Rohmeiss et al, 1995). This effect has been construed as evidence of cerebral control of sodium excretion.…”

Natriuretic Hormone

“…One technique used to study cranial Na receptors has been the intraventricular injection. Anderson et al [3] injected hypertonic saline into the third ventricle of goats and demonstrated large increases in Na excre tion. Similar results have recently been reported in dogs [30].…”