This study determined whether an odor that was paired with injections of CCK octapeptide would later come to inhibit independent feeding in neonatal rats. An odor so paired in rats that were not food or maternally deprived later reduced feeding during the infants' first independent feeding experience. Devazepide, the CCKA receptor antagonist, blocked the reduced intake when injected prior to the feeding test. These studies demonstrate that CCK is an effective unconditioned stimulus even when the animal is not eating during the conditioning process. Furthermore, the conditioned stimulus (the odor) causes behavioral change either by sensitizing a system that includes the CCKA receptor, by causing the release of endogenous CCK, or by changing some non-CCK system that enhances the processing of CCKA receptor-mediated information.