The Effect of Local Change in CSF [Na] in the Anterior Third Ventricle on Salt Appetite

Abstract

The physiological changes inducing salt appetite or the satiation of appetite after ingestion have been investigated in our laboratory for many years. It has been reported that this complex behaviour may be significantly altered by experimental manipulations of the cerebrospinal fluid (CSF) [Na] in sheep. When the CSF [Na] was increased by infusion of hyperosmotic artifical CSF containing 0.5 M NaCl into the lateral cerebral ventricle the salt intake of sodium deficient sheep decreased by about 70 per cent. The CSF [Na] was found to be 162 mM after 1 hour of infusion. Infusion of 0.7 M mannitol-CSF into the lateral cerebral ventricle decreased the CSF [Na] to 134 mM. Sodium intake of salt deficient sheep increased about twofold during the infusion of mannitol¹. It was postulated that sensors in the brain which are accessible from the CSF and some distance from the ventricular wall monitor the [Na] of the brain extracellular fluid (ECF) and modify in turn the salt intake of the sodium deficient animal.