Response of growth-retarded, hypophagic-hypodipsic rats with dorsomedial hypothalamic lesions to a diet in liquid and powder forms.
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Weanling rats with dorsomedial hypothalamic lesions (DMNL rats) and sham-operated controls exhibited significantly reduced food intake and ponderal and linear growth during an 11-day post-operative period on lab chow. For 28 days, a synthetic liquid diet (Liquid) was fed to one DMNL and one control group; a second DMNL and control group received the same diet in a powder form (Powder). DMNL rats remained hypophagic on either diet but DMNL and control rats fed Liquid ate significantly more than their counterparts fed Powder. Total fluid intake pattern was identical to caloric intake. For 27 days all groups again received lab chow. They reverted to the caloric intake pattern shown during the 11-day post-operative period. Body weight gains paralleled the caloric and fluid intake patterns except that during the synthetic diet period the Liquid-fed controls outgained all other groups and that there was no difference between DMNL rats on Liquid and Powder. At sacrifice, plasma glucose, glycerol, free fatty acids and total protein were similar in all groups but carcass protein was higher in the DMNL rats formerly fed Liquid. DMNL rats behave in accordance with extensive previous data that led to the formulation of a "resetting" hypothesis.