Anterior third ventricle (A3V) lesions and homeostasis regulation

Small electrolytic lesions of A3V including the organum vasculosum lamina terminalis (OVLT) made in adult male rats resulted in 50% inhibition of 1.8% NaCl solution intake induced by peritoneal dialysis and significant enhancement of water-deprivation induced thirst. However water intake induced by hypertonic saline was unchanged. Daily water intake fell in the first post-lesion day, increasing thereafter; marked hyperdipsia was seen in some animals. Daily urinary output exceeded water intake. Further, these animals became hypernatremic. Following 24 h water deprivation, urinary excretion of a gastric water load was 18% greater in lesioned than in control animals. These results suggest that A3V lesioned animals fall to regulate fluids and electrolyte homeostasis, perhaps by disruption of an inhibitory feed back loop between the OVLT and other circumventricular structures.