A comparison of the central and peripheral effects of atropine on force lever performance

The central and peripheral effects of atropine, a muscarinic antagonist, on motor control were tested in a force lever apparatus. Three rhesus monkeys were trained to extend their arms through a tube and press a manipulandum with between 25 and 40 grams of force for 3 continuous seconds. Responding was maintained by the delivery of 1.5 ml of water. Single injections of atropine sulfate or atropine methylnitrate (a quaternary derivative) of atropine which does not cross the blood brain barrier) were given 30 min prior to the session. Atropine sulfate disrupted force lever performance in a dose related fashion. Atropine methylnitrate had little or no effect on responding. The effects of atropine on motor control as measured in this procedure, therefore, appear to be centrally mediated.