Metering of intravenously infused nutrients in VMH lesioned rats

Rats were chronically implanted with lesioning electrodes in the ventromedial hypothalamus and with intracardiac catheters. The effects on ad lib oral food intake of a continuous intravenous infusion of glucose were studied both before and after lesioning. Before the lesion oral food intake was reduced by an average of 0.59 kcal per kcal infused. Postlesion the reduction of oral intake was correlated with the caloric value of the infusion, with a mean of 0.92 kcal per kcal. Rats with ventromedial hypothalamic lesions thus adjust their oral intakes in accordance with a systemically infused supplement. Further, the metering of systemically infused substrates actually appears to be more adequate after the lesion. This may be due to an exaggerated insulin release to systemic inputs which have bypassed the orogastric route and are thus unable to elicit preabsorptive endocrine reflexes.