The central nervous control of food and water intake

It has been suggested that food and water consumption in the rat may be co-ordinated by the hypothalamus, as closely contiguous hypothalamic centres control these functions (Strominger 1947). This possibility has been investigated by a study of the effect of damaging each of the centres in turn. Lesions of the tuberal nuclei caused obesity, and in such animals the effect of reduction of water intake on food consumption was increased. Similarly, in diabetes insipidus caused by lesions in the supra-optic region, the effect of diet on water exchange was exaggerated. Variation of the chemical composition of the diet showed that the rat could maintain a constant calorie intake while varying its water consumption widely. Adolph (1947) showed that when food and water were given to the rat together as milk, the intake was governed by calorie content alone, even though this involved drinking an excess of fluid. In rats with diabetes insipidus, it has been shown that calorie content was still the determinant of the amount of milk drunk, although in severe cases the associated fluid was inadequate to prevent dehydration. If the lesion causing diabetes insipidus was extended so as to damage in addition the tuberal centre controlling food intake, limitation of milk intake did not occur, and dehydration was prevented. These experiments provide additional evidence of the activity of a hypothalamic satiety centre. It is suggested that the hypothalamic control of food and water acceptance depends on different, though normally related, features of the diet, food acceptance on the calorie content and water acceptance ultimately on the demands imposed by the renal excretion of the products of metabolism. The apparent correlation of food and water intake in the rat does not imply central co-ordination.