Medial hypothalamic lesions in Syrian hamsters: characterization of hyperphagia and weight gain

Syrian golden hamsters (Mesocricetus auratus) received bilateral lesions aimed at the ventromedial hypothalamus (VMH) or a sham lesion. In the first study, some of the animals in each surgical group were housed in standard sedentary conditions while others had free access to running wheels. The lesions produced a 30% increase in the daily intake of chow, and this was accomplished exclusively by increased meal sizes. As a result, lesioned hamsters gained body weight relative to controls both on the chow diet and in a subsequent high fat diet phase. The effects were comparable in both sedentary and exercising groups. The lesions produced increases in body length and fat content. In the second study, lesions were made in the VMH or in adjacent nuclei and, after an initial period on chow, the hamsters were then given a choice between chow and high fat diet. The lesioned hamsters showed no unusual preference for the high fat diet but, as before, those with damage to the VMH or paraventricular nucleus (PVN) showed exaggerated body weight gain. Hamsters with these lesions were hyperinsulinemic in both fed and fasted conditions at the end of the study.