Effect of a quinine-adulterated diet upon body weight maintenance in male rats with ventromedial hypothalamic lesions.

Male rats offered a quinine-adulterated diet after receiving either ventromedial hypothalamic or sham lesions displayed nearly identical periods of anorexia before maintaining their body weight at a stable but reduced level. When starved prior to surgery to a body weight below this reduced maintenance level, both ventromedial hypothalamic and control animals displayed an intial period of rapid weight gain on the quinine-adulterated diet. When subsequently offered only this diet for an 8-wk period, both groups, after castration, maintained the same reduced level of body weight. Thus, ventromedial hypothalamic animals overeat and become obese on palatable diets, but defend the same lower weight level as controls when challenged with unpalatable diets. Impairment of a mechanism setting the upper, but not the lower, weight limits is responsible for the greatly expanded range of body weights generated in the ventromedial hypothalamic animal by manipulation of diet palatability.