Adipsia in Sheep Caused by Cerebral Lesions

Abstract

During the past decade it has been recognized that several structures in the anterior wall of the third ventricle (A3V) are involved in the regulation of water intake. With regard to these structures, the subfornical organ (SFO) is a probable receptor site for angiotensin to induce water drinking¹, while ablation of the organum vasculosum of the lamina terminalis (OVLT) and the antero-ventral third ventricle wall region (AV3V) disrupts osmoregulatory water intake^2,3. Destruction of the preoptic medianus nucleus (PMN) also reduces water drinking in rats⁴ while in goats ablation of most of the A3V results in adipsia⁵. In view of the likelihood that most of the A3V is involved in the regulation of thirst, we decided to study the effects of either individual or combined ablation of some of these regions in the sheep. The anterior commissure (AC), which courses horizontally across the A3V, provides a convenient boundary for division of the A3V into dorsal and ventral regions. The antero-dorsal wall of the third ventricle (AD3V) contains the SFO, dorsal part of the PMN, and the medial septum, while the anteroventral wall of the third ventricle (AV3V) encompasses the ventral PMN, the OVLT and preoptic periventricular tissue (Figure 1).