Cholecystokinin octapeptide and lithium produce different effects on feeding and taste aversion learning

The strengths of taste aversion induced by sulphated cholecystokinin 26–33 (CCK-8; 1,2,4 and 8 μg/kg IP) and lithium chloride (LiCl; 7.5, 15, 30 and 60 mg/kg IP) were determined in order to assess the relative aversiveness of the two compounds. All doses of LiCl induced strong aversion, but only the highest dose of CCK-8 induced aversion, which was mild. Effects of CCK-8 and LiCl on food intake were then compared in the hour (hr) following 8 hr of food deprivation; rats were on this food deprivation schedule for a relatively long time (78 days) throughout testing. All doses of CCK-8 reduced food intake significantly. Most doses of LiCl either did not affect or significantly increased food intake. Although 60 mg/kg LiCl did not affect food intake when administered 15 or 30 min before food presentation, it significantly increased food intake when administered 1, 2 or 3 hr before food presentation. Overeating of solid food may be an illness-induced behavior. Although a very high dose of LiCl (120 mg/kg) decreased food intake markedly, the rats were obviously distressed, not satiated. Failure of CCK-8 to affect feeding behavior like LiCl is indirect evidence that the reduction of food intake by CCK-8 is not merely the result of aversiveness, but is an extremely potent and specific behavioral effect.