The latent inhibition model dissociates between clozapine, haloperidol, and ritanserin

Latent inhibition (LI), i.e., retarded conditioning to a stimulus following its nonreinforced preexposure, is impaired in some subsets of schizophrenia patients and in amphetamine-treated rats. Typical and atypical antipsychotic drugs (APD's) potentiate LI, but to date the model has not dissociated between them. This study demonstrates such a dissociation using haloperidol (0.1 mg/kg), clozapine (5 mg/kg), and ritanserin (0.6 mg/kg) administered in preexposure and/or conditioning. Under conditions which did not yield LI in vehicle controls (40 preexposures and five conditioning trials), both haloperidol and clozapine, but not ritanserin, led to LI when administered in conditioning. Under conditions which led to LI in vehicle controls (40 preexposures and two conditioning trials), clozapine and ritanserin, but not haloperidol, abolished LI when administered in preexposure. It is suggested that LI potentiation via conditioning detects the "typical" action of APD's whereas LI disruption via preexposure detects the "atypical" action of APD's.