The immediate development of behavioral and biochemical changes following ventromedial hypothalamic lesions in rats

Abstract

The purpose of this investigation was to measure the changes in food intake and metabolic activity immediately following bilateral VMH lesions. Preoperative measures of serum glucose and epinephrine stimulated lipolysis were made on all S s. Both sham and lesioned S s were sacrificed at 2 hr, 8 hr, 24 hr, 3 days, 6 days, 12 days following surgery at which time measures were made of serum glucose, epinephrine stimulated lipolysis and carcass content. Food intake measures were made at 2, 4, 6, 8, 24 hr postoperative and at daily intervals thereafter for 12 days. The hyperphagia observed was clearly two-staged. The first stage began immediately following surgery and was characterized by 4–6 hr of continuous eating. Following a return to control levels the second stage began approximately 3 days following surgery and was characterized by discrete meals. The metabolic measures showed the lesioned S s to be hypoglycemic and to have a decreased epinephrine stimulated mobilization of free fatty acids at 3 days postoperative. The increase in body weight in the lesioned S s was found to be solely attributable to an increase in fat. These results were thought to indicate that the initial stage of hyperphagia is a function of irritation of areas surrounding the VMH while the second stage was thought to represent an attempt to restore the energy deficit created by the decreased lipolysis and increased lipogenesis.