Effects of atipamezole, an alpha 2-adrenoceptor antagonist, on the performance of rats in a five-choice serial reaction time task.

The present study investigates whether pharmacological activation of the noradrenergic system improves attention. The effects of atipamezole, a potent alpha 2-adrenoceptor antagonist, on the performance of adult male rats in the five-choice serial reaction time task were studied. Before drug testings, food-deprived rats were trained to detect and respond to brief flashes of light presented randomly by the computer in one of five spatially diverse locations until a stable level of performance had been reached (about 3 months). Single-dose administration of atipamezole (0.03-3.0 mg/kg) slightly increased the number of premature and perseverative responses during the intertrial interval and slightly decreased the reaction times to incorrect responses, indicating increased behavioral activation. Atipamezole did not affect discriminative accuracy. However, in a subpopulation of rats with the poorest discriminative accuracy according to pretest performance seven of eight rats improved their discriminative accuracy when treated with 0.3 mg/kg atipamezole as compared to controls. At the other doses tested, no improvement was found. The present results suggest that acute administration of atipamezole, and alpha 2-adrenoceptor antagonist, slightly increases behavioral activation, although the effects on baseline performance in the task measuring selective attention are modest.