Increased impulsivity is characteristic of several disease states, and the delay discounting task provides a measure of impulsive behavior (impulsive choice). Delay discounting measures a subject’s preference to select a large reward delivered at variable delays (0 s, 10 s, 20 s and 40 s) compared to immediate delivery of a small reward. Typically, when the delay is very short, the animal selects the large reward. As the delay increases, the animal is less likely to select the large, delayed reward. Compounds that are known to attenuate impulsive choice in humans have been shown to attenuate impulsive choice in rodents in the delay discounting task, for example methylphenidate (Ritalin®).
Administration of methylphenidate dose-dependently increased preference for the large reward at intermediate delays. Asterisks indicate significant difference from vehicle at specific delays. Administration of d-amphetamine exhibited a similar profile to methylphenidate.
Administration of atomoxetine (Strattera®) failed to alter impulsive choice. Nonetheless, it was effective in an assay of impulsive action (see 5-choice serial reaction time test. 5-CSRTT).
Similar to methylphenidate (Ritalin), d-amphetamine was highly efficacious.