Effect of cholecystokinin, gastrin, secretin and GIP on sham feeding in the rat

The satiating potency of impure cholecystokinin (CCK) and of its synthetic octapeptide (CCK-8) were compared in sham feeding rats. The precent inhibition of sham intake and the incidence of resting behavior, a behavioral marker of postprandial satiety, were a function of the intraperitoneal dose of impure CCK and CCK-8. When the doses required to produce 50% inhibition of sham feeding were compared, impure CCK was about 5 times as potent as CCK-8. CCK-8 was about twice as potent for satiety during slow intravenous infusions than after intraperitoneal injections. This demonstrates that the satiety effect is not dependent on transient high, circulating levels that can occur after intravenous or intraperitoneal injections. Under the same test conditions, three other gut hormones, gastrin, secretin and gastric inhibitory polypeptide, had no significant satiety effect. The failure of these hormones to produce satiety demonstrates the relative specificity of the CCK satiety effect. These results are consistent with the hypothesis that intestinal CCK mediates at least part of the postprandial satiety effect of food in the small intestine.