Effects of a cafeteria diet on delay discounting in adolescent and adult rats: Alterations on dopaminergic sensitivity

Diet-induced obesity is a laboratory procedure in which nonhuman animals are chronically exposed to a high-fat, high-sugar diet (i.e. cafeteria diet), which results in weight gain, altered sensitivity to reward, and alterations in the dopamine D2 system. To date, few (if any) studies have examined age-related diet-induced obesity effects in a rat model or have used an impulsive choice task to characterize diet-induced behavioral alterations in reward processes. We exposed rats to a cafeteria-style diet for eight weeks starting at age 21 or 70 days. Following the diet exposures, the rats were tested on a delay discounting task – a measure of impulsive choice in which preference for smaller, immediate vs larger, delayed food reinforcers was assessed. Acute injections of haloperidol (0.03–0.3 mg/kg) were administered to assess the extent to which diet-induced changes in dopamine D2 influence impulsive food choice. Across both age groups, rats fed a cafeteria diet gained the most weight and consumed more calo...