EFFECT OF PARASYMPATHETIC DRUGS ON THE CONDITIONED RESPONSE

Abstract

The effect of increased intrinsic acetylcholine on the C.N.S. was studied by means of the conditioned response. Eserine, prostigmine, pilocarpine, atropine, and MgSO4 were administered to cats having a well-developed conditioned response. Two types of conditioned responses were used: 1) simple flexor withdrawal response, and 2) global response, i.e., trained to jump from one side of a cage to the other by shocking all 4 feet. Eserine abolished the conditioned response for as long as 2 hrs., presumably due to the increased acetylcholine in the brain while prostigmine had a lesser effect which seemed to be due mainly to the discomfort produced by increased intestinal activity. The differences in the action of the 2 anticholinesterases were explained by the inability of prostigmine to enter the brain cells while eserine permits an increase of brain acetylcholine. Atropine and MgSO4 each prevent the action of eserine. Pilo.carpine exerts a transitory depression and later may facilitate the conditioned response. The mechanism of the central action of acetylcholine, atropine, and Mg remains obscure.