Weight loss, slower growth and lower fasting heat production rates following LH lesions in female rats.

Lesions in the lateral hypothalamus (LH) can result in a permanent loss of body weight and slower growth in female rats, but do not do so invariably. Weight and growth rate changes were always accompanied by lower rates of fasting heat production (FHP) independent of changes in activity. The thyroids of these animals were significantly below normal in size. None of the traditional deficits of the "LH syndrome" were present: the animals ate when deprived of water: drank when deprived of food (although less than the control animals) and increased their food intakes when injected systemically with insulin, at least on the initial test. With repeated tests the food intake following insulin-induced hypoglycemia declined both in the animals with lesions and in the animals whose body compositions and weights had been lowered to the same levels.