The Role of Corticosterone in Deprivation-Induced Hyperactivity of Rats Selectively Bred for Saccharin Intake


Alison Williams

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Many humans, particularly young women, affected by anorexia nervosa regularly over-exercise. This symptom is counterintuitive; as the body adjusts for lack of nutrition, it should conserve energy instead of over-expending. Furthermore, not all affected individuals over-exercise. Similarly, food-deprived rats over-exercise, some more than others. Occidental High (HiS) and Low (LoS) Saccharin-Consuming rats differ in vulnerability to this phenomenon, known as deprivation induced hyperactivity (DIH). Both lines increase wheel-running activity in food-deprivation conditions; however LoS rats, which score higher than HiS rats on tests of emotionality, increase their activity more than HiS rats (Dess et al., 2000). This project investigated the role of corticosterone, a stress-related glucocorticoid hormone, on DIH in HiS vs. LoS rats. Wheel running activity of LoS and HiS rats was measured during food deprivation and compared to regular feeding periods. Ketoconazole, a drug that blocks the synthesis of corticosterone, decreased DIH in both the HiS and LoS rats. The results indicate that corticosterone influences DIH, but do not support a differential involvement of the hormone between the two lines. However, LoS rats have higher plasma corticosterone levels than HiS rats (VanderWeele et. al, 2002). Hypercorticosteronemia may increase hyperactivity in LoS rats. Accordingly, the level of circulating cortisol, the human equivalent of corticosterone, may exacerbate the vulnerability of anorexic humans to over-exercise.


Nancy Dess




Howard Hughes Medical Institute Undergraduate Science Education Grant

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