GASTRIC VOLUME RATHER THAN NUTRIENT CONTENT INHIBITS FOOD-INTAKE

To evaluate the separate contributions of distension and nutrient stim ulation of the stomach to the inhibition of short-term food intake and , particularly, to reassess previous analyses based on the inflatable gastrointestinal cuff, four experiments were performed. Rats equipped with pyloric cuffs and indwelling gastric catheters consumed a liquid diet ad libitum. Their consumption during a short-term (30 min) feedin g bout was measured after gastric infusions on cuff-open and cuff-clos ed trials. Animals taking meals (similar to 5 mi) with cuffs closed im mediately after receiving intragastric infusions of 2.5, 5, 7.5, or 10 mi of normal saline exhibited both suppression at the smallest infusi on and a dose-dependent reduction across the other volumes (experiment 1). Additionally, when the test diet concentration was varied, animal s with their cuffs closed consumed a constant volume, not a constant n umber of calories (experiment 2). Furthermore, cuff-closed animals exh ibited no more suppression to 5-ml intragastric infusions of nutrients (including, on different trials, 50 and 100% Isocal diet; 10, 20, and 40% glucose; and 40% sucrose and 40% fructose) than to the same volum e of saline (experiments 3 and 4). in contrast, on cuff-open trials in which gastric contents could empty into the duodenum, these same nutr ient loads were more effective (except fructose) than saline in produc ing suppression of food intake. In summary, although both Limited gast ric distension with the pylorus occluded and intestinal nutrient stimu lation with the cuff open effectively reduced intake, cuff-closed gast ric loads of mixed macronutrients or carbohydrate solutions of 2-8 kca l, pH from 5.8 to 6.7, and osmolarities between 117 and 2,294 mosM/kg produced only the distension-based suppression generated by the same v olume of saline.