Two weeks after parasagittal hypothalamic knife cuts, baseline eating was elevated and 300 mg/kg 2 deoxy-D-glucose (2DG) did not further stimulate food intake. Five weeks postoperatively the food intake baseline had fallen and an eating response to 300 mg/kg 2DG was now seen (p less than 0.005). In this delayed (static) phase intake was also stimulated by 150 mg/kg 2DG (p less than 0.005). 600 mg/kg did not stimulate intake in the lesioned rats at any time, although sham-operated rats always responded positively to this high dose. In conclusion, the neural substrate damaged in hypothalamic hyperphagic rats does not appear to mediate eating in response to glucopribation. The eating response is masked by high baseline intake in the dynamic phase, but reappears in the static phase.

Animals↗

PubMedDate not supplied

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 weaning 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.

Animals↗