Neural Substrate Essential for Suppression of Vasopressin Secretion and Excretion of a Water Load

Abstract

Suppression of vasopressin secretion to very low levels is essential for the excretion of excess water. To investigate a role for the preoptic brain region in the suppression of vasopressin secretion and the excretion of a water load, lesions were made in the vicinity of the lamina terminalis in ewes (LTX-sheep) and responses to water-loading or reduction of cerebrospinal fluid NaCl by i.c.v. isotonic mannitol solution were investigated. In normal conscious sheep, intraruminal water-loading resulted in the urine flow rate increasing and urine osmolality decreasing within 1 h, such that renal free water clearance (CH2O) increased from -1.02 ± 0.16 ml/min (mean ± SEM) to a maximum of +4.99 ± 0..