Role of conditioned taste aversion in the development of activity anorexia

Activity anorexia (AA) occurs when rats are restricted to one meal period (60-90 min) each day and have unlimited access to a running wheel the rest of the time. This AA procedure also contains the conditions necessary for conditioned taste aversion (CTA). The food eaten during the meal period is the conditioned stimulus paired with the unconditioned stimulus produced by wheel running. Thus, CTA to food may account in part for the decreased eating in AA. To test this possibility, male rats were subjected to the AA procedure. They had daily 90-min exposures to their familiar chow and spent the rest of the day in running wheels (experimental condition) or home cages (control condition). A second, concurrent experiment had the same procedure except that novel, rather than familiar, food was used. In both experiments, AA occurred; the rats allowed to wheel run ate less than those in the control condition. Several days after AA training, a two-food preference test assessed whether CTA occurred. Wheel running induced CTA when food was novel but not when it was familiar. Since AA is typically studied with procedures using familiar food, the present findings indicate that CTA plays little or no role in AA.