Duodenal sucrose and glucose infusions enhance suppression by cholecystokinin of sham feeding.

In two experiments I examined whether intraduodenal sucrose and glucose would enhance inhibition of sham feeding by cholecystokinin-8 (CCK-8). In the first experiment, adult male Sprague-Dawley rats received infusions of 0.88 M (30%, wt/vol) sucrose or normal saline at 0.51 ml/min for the first 7.67 min of 30-min sham-feeding tests. Tests began 10 min after intraperitoneal injections of saline or 0.5, 1, or 2 micrograms/kg CCK-8. When sucrose was infused, all doses of CCK-8 reduced sham feeding of 0.88 M sucrose by 60% or more, but with saline infusions, only the highest dose was effective. In the second experiment, rats received 30-min infusions of 0.3 M (5.4%) or 0.6 M (10.8%) glucose or equimolar saline at 0.388 ml/min. Although 1 microgram/kg CCK-8 was ineffective in the absence of infusions, it significantly reduced intake in combination with both concentrations of glucose and hypertonic (0.6 M) saline. Behavioral observations indicated that reductions in intake were attributable primarily to decreased meal length and slower intake. These results suggest that an intestinal signal may contribute to the previously reported ability of preloads to potentiate CCK satiety.