Chronic cocaine treatment induces dysregulation in the circadian pattern of rats' feeding behavior

The effects of protracted cocaine administration (15 mg/kg i.p., twice a da y for 9 days) on the circadian pattern of feeding behavior was studied in i ndividually housed male Sprague-Dawley rats, maintained under a 12:12 light :dark cycle. Water and food were available ad libitum and food intake was m easured twice a day before, during and after withdrawal of cocaine (or sali ne) treatment. Neither total 24-h food intake, nor body mass at the end of the experiment, was significantly different between cocaine-treated and con trol animals. However, cocaine administration affected the temporal distrib ution of food consumption. During the dark (activity) phase, rats receiving cocaine injections consumed significantly less food than control animals, and this effect persisted for up to 3 days of cocaine withdrawal. During th e light (rest) phase, cocaine administration promoted food consumption and a significantly higher food intake was also observed during the first five cocaine withdrawal days. Continuous monitoring of locomotor activity did no t reveal significant changes in the circadian pattern of activity between t he two experimental groups during different treatment periods. except for a n acute increase in locomotion within an hour after daytime cocaine injecti on. The results of this study demonstrate that sub-chronic cocaine administ ration alters the circadian pattern of rats' feeding behavior. (C) 2000 Els evier Science B.V. All rights reserved.