Transient water diuresis and syndrome of inappropriate antidiuretic hormone secretion (SIADH) induced by forebrain lesions of different location.

Inhibition of ADH-secretion and transient water diuresis was observed as acute effects of radio-frequency lesions in the septal region of goats. The water diuresis was not compensated for by drinking and therefore rapidly induced pronounced hypernatremia and hypovolemia. The development of hypovolemia was accompanied by a rise in plasma renin activity. Lesions of the same kind, but extending into the preoptic region near the medial portion of the supraoptic nuclei induced the inability to excrete excessive water characteristic of SIADH. Determinations of plasma arginine vasopressin suggested that the lesions causing SIADH did not produce any noticeable increase in basic ADH-secretion. The results suggest that impulses from juxtaventricular receptors regulating ADH-release and water intake to a considerable extent are transmitted via the septal region, and that elimination of this impulse traffic is sufficient to turn water balance to the negative side. However, reflex volumetric inhibition of the ADH-secretion does not seem to be mediated by pathways passing through the septal region.