Abstract

The effect of chlorpromazine in the cat was studied on the monosynaptic and polysynaptic reflex arcs of the spinal cord, the ascending somato-sensory system, the cerebral cortical arousal pattern following stimulation of the ascending reticular activating system, and the spontaneous and evoked discharges on the isolated cerebral cortex. Doses of chlorpromazine exceeding those which caused obvious changes in behavior of intact unanesthetized cats produced no observable changes in any of these preparations, with the exception of a limited and equivocal depression of the cortical arousal pattern following stimulation of the medial reticular formation. Therefore, the scope of study was widened by a simultaneous sampling of a number of cortical and subcortical areas by means of gangs of electrodes oriented stereotaxically. Chlorpromazine in doses exceeding the minimal effective dose for behavior changes in the intact unanesthetized animal produced a marked increase in spontaneous activity in the amygdaloid nuclear complex. With larger doses of chlorpromazine synchronized spike activity, typical of "grand-mal" type seizure discharges, appeared throughout the brain stem and cerebral cortex. The relative sensitivity of the amygdaloid spontaneous activity to chlorpromazine as compared to other cortical and brain stem areas suggests a possible mechanism of action, for the amygdaloid complex has been suggested by others to mediate an inhibitory influence over wide areas of the brain.