Some effects of muscarinic cholinergic blocking drugs on behavior and the electrocorticogram

Results are presented for the effects of drugs with muscarinic cholinergic blocking actions, both central and peripheral (scopolamine and 1-hyoscyamine) and primarily peripheral (methyl atropine and methyl scopolamine), on conditioned avoidance behavior, spontaneous motor activity, and the ECG in the rat.Low doses of the agents with central actions retarded acquisition of conditioned avoidance, while high doses virtually abolished it. Both low and high doses were essentially ineffective in altering retention of conditioned avoidance. Agents with primarily peripheral actions had no effect on acquisition or retention.Most of the agents produced an increase in spontaneous activity although there was a definite suggestion that higher doses depress activity.All of the agents used provoked a high amplitude, slow frequency ECG. This phenomenon was dose-related; scopolamine appeared to be most effective.It is suggested that the disruption of the acquisition, but not retention, of conditioned avoidance is due to a deficit of recent memory. A possible site of action of cholinergic blocking drugs is proposed.