Involvement of striatal cholinergic receptors in reaction time and fixed-interval responding in rats.

In the present study the effects of intrastriatal scopolamine injections (0, 3, and 10 microg) were evaluated in two operant tasks. The first task tested the reaction time performance of rats, while the other task measured responding in a temporal discrimination test (fixed-interval 30 s). In the reaction time task, in which the rats had to hold down a lever during a variable interval, blockade of striatal muscarinic receptors resulted in a decrease in the total number of trials that the rats completed. Scopolamine also decreased the proportion of anticipatory responses, i.e., premature releases of the lever. The reaction time was not affected after scopolamine infusions. In the temporal discrimination task, the number of emitted responses was decreased after scopolamine infusions. However, the number of trials completed in the fixed interval task was not affected by scopolamine. It was concluded that the striatal cholinergic neurons are involved in organization of motor responses.