The Localization of Hypothalamic Structures in the Rat Influencing Water Consumption ‡

Hyperphagia and obesity occur following bilateral destruction of the ventromedial region of the hypothalamus.4" On the other hand, bilateral destruction in the lateral area leads to anorexia and death."2 In the rat, the ventromedial lesions also produce a reduced water/food intake ratio, a delayed excretion of a water load, increased tubular reabsorption of water,14 and a small but significant increase in serum sodium.'5 These signs were considered "reflections of a chronic state of relative dehydration. The low water/food intake ratio implies a deficit in the neural mechanism responsible for thirst and its alleviation."' This "hypothalamic hypodipsia" can appear following such lesions, regardless of the presence or absence of hyperphagia and the development of obesity"4,"; it, like hypothalamic hyperphagia and diabetes insipidus, is not fatal to the animal. That the hypothalamus influences thirst has been confirmed by the induction of thirst in goats upon injection of hypertonic saline into the medial portion of the hypothalamus.8 The purpose of the present study was to locate more precisely that area of the hypothalamus the destruction of which produces chronic "hypodipsia."