Cholecystokinin reduces sucrose palatability in rats: evidence in support of a satiety effect

To investigate the hypothesis that peripherally administered cholecystokinin (CCK) reduces food intake by the production of aversive internal cues, we examined the effects of the sulfated, octapeptide form of CCK on taste reactivity responses to oral sucrose infusions in male rats implanted with intraoral cannulas. After injection of CCK (4, 8, or 16 micrograms/kg ip) or 0.15 M saline (1 ml/kg ip), a series of brief (30 s) intraoral infusions of a 0.30 M sucrose solution was administered at 2-min intervals for 10 min. All doses of CCK were found to significantly decrease ingestive responding during the first and subsequent sucrose infusions without promoting a significant increase in aversive responses relative to controls. The lack of a gradual, conditioned shift in taste reactivity responses, from an ingestive to an aversive pattern (which is typically observed after LiCl administration), suggests that the production of nausea-like aversive internal cues was likely not responsible for the observed CCK-induced alterations in taste reactivity responses. It appears that the unconditioned, satiogenic effects of CCK contributed to the selective reduction in ingestive responses observed in the present study.