Behavioral effects of withdrawal from sweetened vegetable shortening in rats

This study tested the hypothesis that withdrawal from intermittent access to a sweet fat mixture would lead to an exaggerated motivation and craving for palatable food. Male Long-Evans rats were divided into three weight-matched groups based on access to sweetened vegetable shortening (SVS). Groups received 1-hour SVS access everyday (7D group), 1-hour SVS access intermittently, 3 days/week (3D group), or no SVS access (Naïve group). By the second week 3D rats began to display a disordered eating pattern. After 28 days on this feeding schedule SVS was withdrawn and anxiety was measured in an elevated plus maze. Motivation was assessed through operant performance for 10% sucrose on a progressive ratio schedule and craving was examined with a reinstatement test for lever pressing following extinction. Initial measures of anxiety and motivation found no differences among groups. However, when food was deprived overnight, there was a greater increase in lever pressing in the 3D group compared to 7D and Naïve rats. Thus a history of intermittent SVS access enhanced the reinforcing value of sucrose, but only under deprivation conditions. Interestingly, reinstatement of responding for sucrose was present only in the Naïve group. These findings suggest that a history of disordered eating may result in augmented motivation for palatable foods during a state of negative energy balance.