Prefrontal cortex and reversion of atropine-induced disruption of the degraded contingency effect by antipsychotic agents and N-desmethylclozapine in rats

Abstract

Interactive context processing is a cognitive ability that is altered in psychotic states, including schizophrenia. This deficit has been linked to prefrontal cortical dysfunction in humans. The degraded contingency effect (DCE) is a simple form of interactive context processing by which contextual information interferes with a target conditioned stimulus for control over conditioned responding. We have previously shown that the DCE was disrupted by the muscarinic receptor antagonist atropine and that this disruption was specifically restored by cholinergic drugs displaying an antipsychotic-like profile, such as physostigmine or xanomeline. The DCE was selectively associated with an increase in Fos immunoreactivity in the medial prefrontal cortex (mPFC), an increase that was not observed in the presence of atropine. Here, we set out to test the actions of typical, atypical and potential antipsychotics on atropine-induced disruption of the DCE and the related mPFC Fos-immunoreactivity profile. Low doses of haloperidol, olanzapine, clozapine and N-desmethylclozapine reversed atropine-induced disruption of the DCE, but with different dose-dependent curves (linear shapes for haloperidol and N-desmethylclozapine, inverted U shapes for olanzapine and clozapine). The level of Fos within the mPFC paralleled the pharmacological profile of the different drugs. Compared to contingent control groups, an increased level of Fos immunoreactivity within the mPFC was observed only with doses that reversed atropine-induced disruption of the DCE. These results suggest that the deficit of interactive context processing, which is a hallmark of psychotic states, might originate from a mere deficit of fundamental associative processes. This deficit might result from a cholinergic blockade of the PFC.