Two satiety systems revealed by hypothalamic knife cuts in hypophysectomized rats

When pituitaries are intact, hypothalamic knife cuts produce obesity in adult rats but not in weanlings. Knife cut weanling females do not usually begin to become obese until after they are 7 weeks old. When pituitaries are removed, symmetrical or asymmetrical knife cuts produce obesity promptly in both adults and weanlings. Obesity indices that correct for stunted linear growth reveal that in adults the degree of obesity is independent of the presence or absence of the pituitary. Based on these findings we speculate that there may be two appetite regulating systems, a juvenile one involving the pituitary, and an adult one involving the hypothalamus.