EFFECTS OF METHYLPHENIDATE ON FOOD AND WATER-CONSUMPTION AT DIFFERENT BODY WEIGHTS

The effects of intraperitoneally administered methylphenidate at 0, 1.5, 3.0, 6.0, and 12.0 mg/kg were studied in two experiments. Experiment 1 determined the effects of methylphenidate on 0.5, 1.0, 2.0, and 24 hr post injection food and water consumption in rats at ad lib feeding body weights. Experiment 2 determined the post injection effects of methylphenidate on 0.5, 1.0 and 2.0 hr food and water and 24 hr water consumption in rats maintained at 80% ad lib feeding body weight due to partial food deprivation. The results of Experiment 1 indicate that when animals are feeding ad lib at normal body weight food and water consumption is decreased for 2 hr following the administration of the lowest 1.5 mg/kg dose of methylphenidate. Methylphenidate in doses as high as 12.0 mg/kg has no effect on 24 hr food and water consumption under these conditions. The results of Experiment 2 indicate that when animals are maintained at reduced body weight due to partial food deprivation, food consumption for 2 hr is significantly decreased by the highest, 12.0 mg/kg, dose of methylphenidate. These effects are observed within the first 30 min post injection when methylphenidate decreases food consumption in a dose dependent manner. Methylphenidate has no effect on water consumption under these conditions. The effects of methylphenidate on ingestive behavior are discussed in terms of previous experiments and the possible differential effects on motor activity at different body weights under different stimulus conditions. © 1979.