Further nutritional characterization of dorsomedial hypothalamic hypophagia in rats: diet consistency, finickiness, self-selection of diets, starvation and realimentation and "stress eating".
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Young-mature male Sprague-Dawley rats received bilateral lesions in the dorsomedial hypothalamic nuclei (DMNL); sham-operated rats served as controls. After 30 days of a pelleted commercial laboratory diet, they received a powdered lab diet for 10 days. Both groups of rats reduced food intake for the duration of the test. Thus, although grossly hypophagic under ad libitum feeding conditions, DMNL do not impair adaptation to a diet of different consistency. Both DMNL and controls were significantly hypophagic when fed a quinine-adulterated powdered diet, but only on the first of a 9-day regimen. Thus, they show only transitory finickiness. During a 16-day self-selection test with three equicaloric diets with different amounts of the three macronutrients in each (HCD: high carbohydrate, HFD: high fat, and HPD: high protein diet), DMNL rats ate in absolute terms (g/day) the same amount of HCD, significantly less HFD and during two of seven measuring periods, significantly less HPD. However, their intake in percent of total consumption was similar to that of the controls., After a 48-hour fast, DMNL rats lost and regained body though these rats showed hypophagia during the 48-hour realimentation period, their efficiency of food utilization was similar to the controls. Thus, DMNL rats have not lost the capacity to regulate body weight and food intake after fast-induced weight loss. During eight tail pinch (TP) sessions (11 days), DMNL rats were hyperphagic and preferred HCD and HFD in comparison with controls. In their home cages (lab diet) DMNL rats were hypophagic and over 11 days showed a decline in food intake while the controls displayed an increase. In contrast to previous findings, the challenges of the present study unmasked some deficits in energy homeostasis in the DMNL rat.