Osmoregulatory thirst in rats after lateral preoptic lesions.

In confirmation of previous observations, lesions of the lateral preoptic area in rats abolished water ingestion during a 4-hr test following an intraperitoneal injection of hypertonic NaCl solution. However, it was observed that these animals increased their water intakes when tests were prolonged to 24 hr and drank almost exactly what they needed for osmoregulation. Furthermore, they increased their water intakes normally when NaCl was given in their diet, when NaCl was administered intravenously, or when they were water deprived and given preloads of isotonic saline to remove hypovolemia. These findings indicate that rats with lateral preoptic lesions do experience osmoregulatory thirst, and consequently, they raise new doubts about whether osmoreceptors located in the lateral preoptic area mediate thirst following the administration of osmotic loads.