A comparison of cholecystokinin-induced changes in gastric emptying and feeding in rats

We have compared the abilities of the cholecystokinin octapeptide (CCK-8) to delay gastric emptying and to influence feeding under similar experimental conditions in the rat. The effect of CCK-8 on gastric emptying was assessed in 6-h-deprived rats receiving 10-ml intragastric test loads of 0.15 M saline or 15% (wt/vol) sucrose. Analysis of half-emptying times indicated that intraperitoneal administration of CCK-8 in doses of 1.4-22.4 micrograms/kg produced a dose-dependent retardation of emptying of both saline and nutrient. Lower doses of CCK-8, 0.01 and 0.1 micrograms/kg, had no effect on gastric emptying. The effect of CCK-8 on feeding was assessed in normally feeding rats tested under the same experimental conditions used in the gastric emptying studies. Doses of CCK-8 capable of retarding gastric emptying also suppressed eating in a dose-dependent manner. These findings provide necessary correlational support for the hypothesis that the satiety produced by CCK-8 may be mediated by inhibition of gastric emptying. However, a further quantitative analysis of the correspondence of the gastric emptying and feeding effects of CCK-8 suggest that retardation of emptying cannot account entirely for the satiety effect of the peptide.