DIET-INDEPENDENT SUPPRESSION OF INGESTIVE BEHAVIOR BY CHOLECYSTOKININ-OCTAPEPTIDE AND AMINO-ACIDS

Male rats consumed much more of an intraorally administered mixed prot ein, fat and carbohydrate solution than of a carbohydrate solution. In jection of cholecystokinin octapeptide (CCK-8, 0.6-5.0 mu g) suppresse d intake of both solutions, but the CCK-A receptor antagonist L-364,71 8 (20-40 mu g) facilitated only carbohydrate intake. Blood levels of C CK-8 were higher after intake of the carbohydrate than the mixed solut ion. Blood levels of isoleucine, leucine, lysine, threonine, valine, a nd tryptophan increased only after intake of the mixed solution. Injec tion of these amino acids suppressed intake of both solutions. Blood l evels of amino acids were also less after the seventh than after the f irst session ingesting the mixed solution. Treatment with CCK-8 or ami no acids inhibits intake of any diet, but when secreted endogenously, these signals may terminate the meal in a diet-dependent manner.