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The effects of food restriction on wheel running in rats

By Vanessa M. Lopak

Abstract

The impact of food restriction and refeeding on wheel running was examined in 3 groups of rats: 55 day old male rats in Experiment 1; 140 day old male rats in Experiment 2; and 180 day old female rats in Experiment 3. After a baseline period of 24 to 40 days wheel experience with ad lib food access half of the animals were food restricted for 16 days by being given a limited amount of food daily to reduce (and maintain) their body weight at 85% of their baseline weight. After food restriction the rats were returned to ad lib food access and running was observed for another 16 days. Running performed by the food-restricted rats was compared to the running performed by the continuously ad lib fed control rats. There were pronounced differences in the baseline running between the 3 groups of rats. The 55 day old males and 180 day old females showed high baseline levels of running while the 140 day old males showed low levels of running. Food restriction increased total wheel running by 70% from the high baseline levels in the 55 day old male group and by 112% from the low baseline levels in the 140 day old male group, but did not increase running in the female group. The food restriction induced increase in male running occurred only when the rats were decreasing in body weight; running returned to baseline levels for animals maintained at 85% baseline body weight. Baseline levels of running did not predict the increase in running for any of the rats. When ad lib food access reinstated the high baseline running food-restricted 55 day old males showed a decrease in wheel running to below their baseline and control group levels. This decrease in running was negatively correlated with baseline levels of running, suggested that all runners were approaching a floor level of running. The low baseline running food-restricted 140 day old male rats did not show a decrease in wheel running at refeeding; instead their running gradually declined to baseline levels over about 3 days. After ad lib food access was reinstated there were no long-term consequences of food restriction on wheel running. These results indicate that food restriction induced changes in wheel running are not influenced by age (or some covariate of age, such as body weight) in male rats, but are affected by gender, by baseline levels of running, and are controlled by a separate mechanism than that which causes the individual differences in baseline wheel running

Topics: Behavior and Behavior Mechanisms
Publisher: Scholars Commons @ Laurier
Year: 2002
OAI identifier: oai:scholars.wlu.ca:etd-1728
Provided by: Scholars Commons

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