Comparisons among experimentally induced obesity syndromes

Abstract

Numerous procedures have been developed to induce overeating and body weight gains in experimental animals. The purpose of the present experiments was to determine the extent of the similarity and difference among five obesity syndromes. In Experiment 1, female rats received either ventromedial hypo­ thalamic (VMM) lesions, parasagittal knife cuts, ventral noradrenergic bundle (VNB) lesions, ovariectomy, or 5,7-dihydroxytryptamine (5,7-DHT) injection. Measurements of food intake, diurnal patterns of intake, ovarian cycling, body weight gain, and adiposity were obtained. All treatments induced overeating, and increments in both body weight, and adiposity. Quantitatively and qualitatively, the syndromes displayed by VMH lesioned and knife cut rats were highly similar. Both groups overate during both the light and dark cycle. In contrast, VNB lesioned rats overate only during the dark cycle whereas 5,7-DHT rats overate only during the light cycle. Ovariectomized rats showed only slight increases in food consumption, body weight gain, and adiposity. In Experiment 2, female rats received either VMH lesions, knife cuts, VNB lesions, or ovariectomy and were maintained on a restricted availability feeding schedule. VMH lesioned, knife cut, and VNB lesioned rats that were not permitted to gain more body weight than control rats accumulated more fat than either ovariectomized or control rats. The results of these experiments suggest that the obesity syndromes induced by hypothalamic damage may, in part, represent dysfunctions of