Ventromedial hypothalamic lesions and weight gain in rats: Absence of a static phase

Abstract

Bilateral electrolytic lesions of the ventromedial hypothalamic area of adult female rats produced not one but two abnormal stages of weight gain. A linear phase of continuous fattening, rather than a plateau of bodyweight, followed a negatively-accelerated, curvilinear phase of weight gain. Following the eleventh postoperative week, the lesioned rats maintained a steady increase in body weight at a mean rate more than double that of operated control rats of the same age ( p<0.001). Manipulation of the body weight of individual rats during this second, linear phase suggests that in addition to an immediate elevation of the “set-point” for body weight that produces the initial, curvilinear phase, such lesions also induce an additional, gradual elevation of the set-point with time (i.e., a climbing set-point). This long-term effect of ventromedial hypothalamic area lesions may be appropriate as a model for human obesity.