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AGE EFFECTS IN SPRAGUE-DAWLEY RATS FED A CAFETERIA DIET
Institute of Pharmacology and Toxicology, School of Veterinary Medicine, Free University Berlin, Koserstr. 20, 14195 Berlin, Germany
Introduction: Obesity influences a wide-ranging level of the population. Animal models are suitable to study mechanisms of obesity as they are particularly helpful to clarify the involvement of single neurotransmitters and hormones, as for example leptin (e.g. Zucker-rat, ZDF-rat).
Aim: Our purpose was not to use an obese animal model which is based on a genetic defect but on the manipulation of the diet. Such a model takes into account the important part of the environment for the development of human obesity. Since differences in age often result in contradictory outcomes of equally conducted tests, we investigated metabolic as well as behavioral changes induced by a so called Cafeteria Diet in juvenile and adult male Sprague-Dawley rats.
Method: In addition to standard chow, a choice of human food items with high caloric content (e.g. sausage, cheese, cake) was offered over a period of 4 weeks to 6-week-old and 12-month-old rats. Control groups received only standard chow. Water and food consumption, energy intake and body weight development were documented daily. After 4 weeks of observation rats were tested for their anxiety-related behavior and motor activity in the Elevated Plus-Maze Test (EPM) and Open Field Test (OF). Rats were decapitated and fat tissue was dissected at the end of the study.
Results: In comparison to the control groups body weights only of the adult animals were significantly higher after 4 weeks of observation. An elevated caloric intake was shown in both age groups fed the Cafeteria Diet and resulted mainly from a higher average consumption of fat. Visceral and subcutaneous fat mass were significantly enlarged in the Cafeteria groups of both ages. Upon behavioral testing, adult male Cafeteria fed rats were not different from controls in the OF, but showed significantly more grooming and less entries into the open arms of the EPM. Within juvenile males the Cafeteria Diet had no effect on behavioral testing.
Conclusion: The results show that although all animals were from the same strain and stock, age differences could be documented. The outcome indicate that comparisons of own results with findings in the literature can not easily be implemented when animals are in different age stages.
Correspondence: Wiebke Warneke, Free University Berlin, School of Veterinary Medicine, Dept. of Pharmacology and Toxicology, Koserstr. 20, 14195 Berlin, Germany. Tel.: +49 (0)30 / 838 532 24.
Acknowledgement: This study is supported by the ?Stiftung der Deutschen Wirtschaft? (sdw).