Injections of atropine into the caudate nucleus impair the acquisition and the maintenance of passive avoidance.

Two experiments were performed to test the hypotheses that cholinergic activity of the caudate nucleus (CN) is involved in the acquisition and in the maintenance of passive avoidance behavior. Rats were trained, in one trial, to avoid one of two compartments of a conditioning box and retention of the task was measured 24 hours later. Several doses of atropine were injected into the CN of independent groups of animals. In Experiment 1 the atropine was injected 2 minutes after training and in Experiment 2 it was injected 6 minutes before retention testing. In both cases a dose-dependent retention deficit was found. These results indicate that striatal cholinergic activity is indeed involved in the processes that mediate passive avoidance conditioning.