A study of permanent adipsia induced by medial forebrain lesions

Cerebral lesions involving most of the anterior wall of the ventricle, and the medial part of the septal region, induced a permanent loss of thirst in two goats. The ventral part of the lamina terminalis remained intact in one of the animals. Pronounced dehydration (10--13% loss of b.wt.) developed during periods (3--7 days) when water supplementation was omitted. Determinations of plasma arginine vasopressin in one of the animals revealed that the dehydration did not cause any significant increase in the secretion of antidiuretic hormone. However, the water deficit induced a considerable rise in plasma renin activity and tachycardia. If anything, the caroitid blood pressure became slightly elevated towards the end of 7 d dehydration periods. The lesions obviously inactivated a cerebral sensory mechanism controlling water balance. It may have been due mainly to destruction of juxtaventricular receptors in the anterior hypothalamic region, but perhaps also to a disruption of afferents from such receptors located posterior to this cerebral level.