Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Cholecystokinin (CCK), a polypeptide gut-brain hormone, reduces food intake in a variety of species and across a number of experimental situations. By application of the taste reactivity test, the present thesis examined whether aversive side effects and/or alterations in palatability contribute to the anorectic effects of CCK in rats. Experiment 1 examined the ability of CCK to alter sucrose-elicited taste reactivity responses. Peripheral administration of CCK produced a dose-dependent reduction in ingestive responses without promoting an increase in aversive responses. Experiment 2 examined the ability of CCK to alter taste reactivity responses during oral water infusions. CCK treatment reduced the frequency of water-elicited ingestive responses when rats were fluid-replete, but failed to have any effect on fluid-deprived rats. Experiment 3 examined the ability of CCK to alter taste reactivity responses to oral infusions of a bittersweet solution that elicits a mixture of ingestive and aversive responses in naive rats. Similar to the results of the first study, CCK reduced ingestive responses and failed to increase aversive responses. Experiment 4 compared taste reactivity responses to a sucrose solution following multiple injections of CCK relative to a single injection of an emetic agent, lithium chloride (LiCl). An immediate, unconditioned decrease in ingestive responses, that was not accompanied by increased aversive responses, was observed in CCK treated rats. In contrast, a conditioned increase in aversive responses, and decrease in ingestive responses, was observed in LiCl treated rats. These data demonstrate that aversive gastrointestinal cues were present only in LiCl treated rats. Together, these studies provide the first demonstration that the suppressive effects of CCK are not reliant on taste cues. Furthermore, they rule out the possibility that a non-specific suppressive effect of CCK is responsible for the observed changes in taste reactivity. It also appears unlikely that injection of CCK produced any aversive gastrointestinal cues, due to the lack of aversive responding observed across a variety of conditions. It is concluded that CCK-induced changes in taste reactivity are behaviorally specific and are produced by a satiogenic mechanism of action.



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