The Paradoxical Effects of Ritalin on Food Deprivation-Induced Hyperactivity in HiS and LoS Rats


Ian McLaughlin

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An important aspect of ADHD stimulant medication may be found examining ADHD?s comorbidity with anorexia (Gillberg et al., 2007). A valid experimental model of anorexia is a food-deprivation induced hyperactivity (DIH) treatment; where laboratory animals given access to a running wheel and restricted food increase hyperactivity, gauged by voluntary running. In a previous study (McLaughlin, Dess & Chapman, unpublished), we found a paradoxical effect of Ritalin among randomly bred rats who were food deprived. Ritalin suppressed running in those rats especially vulnerable to DIH, but further increased running in those moderately affected by DIH. Occidental LoS and HiS rats, selectively bred for saccharin taste preferences, differ in their vulnerability to food-deprivation. Dess et al. (2000) has found LoS females run much more than HiS females when food deprived. The present study examined the effects of Ritalin on food-deprivation induced hyperactivity in either HiS or LoS male rats. We tested 20 HiS and 20 LoS male rats in a running wheel for two hours a day under four different conditions: normal, drug only, food deprived only, and food deprived and drugged. Every rat ran more when food deprived, but vulnerability to food deprivation did not differ between lines. However, Ritalin did increase running in HiS but decrease running in LoS regardless of whether the rats were food deprived. This study is evidence of the importance to monitor the use of drugs with possible paradoxical effects like Ritalin due to the large role individual differences may play in the drug?s outcome.


Nancy Dess




Norris Scholars Program

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