EFFECTS OF LOCAL APPLICATION OF DOPAMINERGIC DRUGS INTO THE MEDIAL PREFRONTAL CORTEX OF RATS ON LATENT INHIBITION

The involvement of the dopamine (DA) innervation of the medial prefron tal cortex (PFC) in attention was studied in a latent inhibition (LI) paradigm in rats. LI becomes evident by a retardation of conditioning to a stimulus after nonreinforced preexposure to that stimulus. LI is thought to reflect an animal's ability not to attend to irrelevant sti muli and is often used as an animal paradigm modeling schizophreniclik e attentional deficits, In the present study the effects of bilateral infusions of the DA receptor agonist apomorphine (APO, 9.0 mu g/side) and the DA receptor antagonist cis-flupenthixol (FLU, 12.0 mu g/side) into the medial PFC on LI were assessed. Although in comparison with v ehicle both APO and FLU infusions attenuated response suppression in n onpreexposed animals, the drugs differentially affected LI in preexpos ed animals. After infusions of APO animals failed to show conditioned suppression, whereas FLU-treated animals displayed as much suppression of responding as nonpreexposed animals. The abolition of LI induced b y FLU infusions into the medial PFC suggests that prefrontal DA is inv olved in attentional processes in a way opposite to the established ro le of subcortical DA systems in these processes. (C) 1996 Society of B iological Psychiatry