| Abstract No.: | B-G2187 |
| Country: | Canada |
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| Title: | THE EFFECT OF INITIAL WEIGHT ON THE WHEEL INDUCED FEEDING SUPPRESSION |
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| Authors/Affiliations: | 1 Amanda Hertel*; 1 Graham Parfeniuk; 1 Laura Botzang; 1 Roelof Eikelboom;
1 Wilfrid Laurier University, Waterloo, ON, Canada.
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| Content: | Adult rats show a feeding suppression lasting for 6-10 days when a running wheel is first accessible (wheel induced feeding suppression; WIFS) (Alfonso & Eikelboom, 2003). The rats also show a reduced weight (relative to no wheel controls) that is maintained throughout wheel access. This is suggested to be a good animal model of aspects of Anorexia Nervosa (AN), as approximately 40-80% of patients display hyperactivity during an acute phase of their disorder, exhibiting a pathological pattern of behaviors where a decrease in feeding is coupled with an increase in physical activity. In WIFS it is unclear whether the feeding suppression is responsible for the weight change, or whether a change in the weight “set point” is responsible for the feeding suppression. Objectives: Over a series of three experiments, the effect of differences in the initial weights of the animals on the presence and/or magnitude of the WIFS was examined to determine the nature of the cause/effect relationship between reduced feeding and lowered weight occurring at wheel introduction. Materials and Methods: A total of 176 male rats were used over the three experiments. In the first phase of each experiment, half of the rats were food restricted (to approximately half the food of ad-lib feeding animals) for 8, 9 or 16 days to reduce their body weight to approximately 80% of non-restricted rats (a level below the weight reduction that wheel access has been shown to induce) when the wheel was introduced. At phase 2, all rats were returned to ad lib food. Zero, one or four days later, half of the reduced weight and half the control rats were given ad lib wheel access. Body weight, food intake, and wheel running were monitored daily throughout the experiment. Results: Over the three experiments, for the 8 days in the wheel phase, prior food restriction elevated and wheel access suppressed feeding. These two effects did not interact suggesting that the WIFS was just as strong in the weight reduced and control rats. The WIFS was not apparent on the first day of wheel access when wheel access and ad-lib food were given on the same day (Experiment 1) or when wheel access was given 1 day after ad-lib food access (Experiment 2). This finding is possibly due to a ceiling effect of binge eating that occurs when animals are returned to ad lib food. However, the WIFS was apparent on the first day of wheel access when wheel introduction occurred 4 days after return to ad lib food, when feeding levels in previously deprived animals had returned to a level approaching normal (Experiment 3). Conclusions: The present studies suggest that the wheel induced decrease in feeding is primary and responsible for the prolonged weight change induced by the wheel introduction. It is also noted that the WIFS is not present when the wheel is introduced during the binge feeding episode that occurs when previously restricted animals are returned to ad-lib food access. |
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