Gastric emptying and control of ingestion in preweanling rat pups

In adult rats, the rate of gastric emptying is modulated by properties of the diet, including its caloric content and osmotic properties. In developing pups, there is little known about the modulation of gastric emptying, despite evidence that volume of gastric contents may play a significant role in modulating intake in young rats. The present experiments examined gastric emptying of oral infusions of corn oil emulsions or glucose solutions in pups aged 6 or 15 days of age and their effects on independent ingestion. The results demonstrated that pups as young as 6 days of age modulate the rate of gastric emptying in response to changes in the concentration of a corn oil or glucose diet. However, oral infusions of corn oil emulsions failed to produce differences in subsequent intake of a milk diet, while oral infusions of a glucose diet did suppress subsequent intake. Taken together, the results support different ontogenetic courses for the development of mechanisms modulating gastric emptying of lipid versus carbohydrate diets, and suggest that gastric fill plays a limited role in modulation of intake in young pups.