Sucrose preference and LiCl illness-induced aversion as a function of drug dose and phase of the illumination cycle

To assess the influence of circadian rhythmicity on conditioned taste aversion in rats, two vivaria (with the illumination cycle in one vivarium phase shifted 12 hours with respect to the other) were used to permit dissociation of rhythmic environmental (laboratory) activity from the influence of the illumination cycle. Also included were controls for change in baseline taste preference across phases of the illumination cycle. Across both vivaria: (1) Sucrose preference was significantly higher for Dark Phase than Light Phase animals. (2) Strength of the illness-induced taste aversion was greater during the Light than Dark Phase of the illumination cycle. These findings were discussed in terms of circadian alterations in metabolism that may modulate both sucrose preference and sensitivity to the consequences of LiCl. It was further demonstrated that inclusion of a circadian rhythmic factor in a conditioning model enables one to predict more accurately the magnitude of an acquired taste aversion.