Environmental enrichment and cafeteria diet attenuate the response to chronic variable stress in rats

Exposure to an enriched environment (EE) or the intake of a highly palatable diet may reduce the response to chronic stress in rodents. To further explore the relationships between EE, dietary intake and stress, male Sprague-Dawley rats were fed one of two diets for 5 weeks: high carbohydrate (HC) or "cafeteria" (CAF) (Standard HC plus a choice of highly palatable cafeteria foods: chocolate, biscuits, and peanut butter). In addition, they were either housed in empty cages or cages with EE. After the first two weeks, half of the animals from each group were stressed daily using a chronic variable stress (CVS) paradigm, while the other half were kept undisturbed. Rats were sacrificed at the end of the 5-week period. The effects of stress, enrichment and dietary intake on animal adiposity, serum lipids, and stress hormones were analyzed. Results showed an increase in intra-abdominal fat associated with the CAF diet and an increase in body weight gain associated with both the CAF diet and EE. Furthermore, the increase in ACTH associated with CVS was attenuated in the presence of EE and the CAF diet independently while the stress-induced increase in corticosterone was reduced by the combination of EE and CAF feeding. The present study provides evidence that the availability of a positive environment combined to a highly palatable diet increases resilience to the effects of CVS in rats. These results highlight the important place of palatable food and supportive environments in reducing central stress responses.