Repeated inescapable stress produces a neuroleptic-like effect on the conditioned avoidance response

Abstract

This study tests the hypothesis that the dopaminergic system mediates a restitutive response by decreasing its own activity in the face of events like persistent inescapable stress that threaten to interrupt organized mental activity. It is well established that neuroleptic drugs inhibit the conditioned avoidance response (CAR), but not the escape response, probably via a reduction in subcortical dopaminergic activity. We trained rats to perform the CAR and then subjected them to acute and chronic stress to determine whether this would result in inhibition of the CAR. Rats subjected to twice daily tailshock stress for 8 days showed inhibition of the CAR and a reduction in dopamine (DA) utilization in the nucleus accumbens. These findings are compatible with the hypothesis that an endogenous DA-dependent mechanism exists that mimics neuroleptic effects in the face of repeated stress. In humans this response may serve as a protection against psychotic decompensation from chronic endogenous or exogenous insult.