Aluminum effects on operant performance and food motivation of mice.

Previous studies demonstrated better performance of operant tasks in mice fed excess aluminum (Al) in the diet. The current study examined whether (a) Al leads to impairment of spatial alternation after extended practice, (b) Al enhances performance of an operant task that emphasizes motor learning and ability (differential reinforcement of high rates, DRH), and (c) Al enhances food motivation as reflected in progressive ratio (PR) performance. Male Swiss Webster mice were fed purified diets containing 7 (control), 500, or 1000 microg Al/g diet. Subgroups were fed excess Al diets during development (conception to 35 days postnatal) or as adults (35 days postnatal through the end of testing). Operant training and testing were conducted at 50 days postnatal. Data indicated that extended training of developmentally exposed mice did not lead to performance deficits, that DRH performance of both developmentally and adult-exposed mice was enhanced, and that food motivation (PR task) was significantly greater in the adult-exposed group with a similar trend in the developmentally exposed group. Aluminum may bias performance of food-motivated tasks by influencing food motivation.