Effects of scopolamine on components of delayed response performance in the rat

The effects of scopolamine and methyl scopolamine on working memory processes were investigated in a paired trial, go-no go delayed response procedure in which rats initiated their own trials. Drug effects were examined concurrently on performance at three delays--no, 0, and 2.5 sec. Scopolamine disrupted no-delay (discrimination) performance in a dose-related manner. Scopolamine also progressively reduced performance at 0-delay and 2.5 sec delay more than at no-delay, but only at the highest administered dose (0.5 mg/kg). Scopolamine affected sensitivity, but not response bias. Although both scopolamine and methyl scopolamine reduced the probability of trial initiation, only scopolamine disrupted accuracy of performance on the initiated trials.