Phencyclidine-induced stereotyped behaviour and social isolation in rats: a possible animal model of schizophrenia.

Phencyclidine (PCP) can induce a model psychosis in humans that mimics the positive and negative symptoms of schizophrenia. The purpose of the present study was to determine whether PCP can induce similar behavioural effects in rats and whether these effects can be alleviated by neuroleptic drug treatment. Rats were tested in the social interaction test, and their behaviour was quantified by an automated video-tracking system and manual scorings of stereotyped behaviour and ataxia. The behavioural effects of different dose- and administration regimes of PCP were initially determined, and it was found that PCP dose-dependently induced stereotyped behaviour and social isolation in the rats. Comparison to clinical studies suggests that these behaviours correspond to certain aspects of the positive and negative symptoms, respectively, of a PCP psychosis in humans. Subsequently, the effects of 3 or 21 days of administration of the antipsychotic drugs haloperidol or clozapine on the behaviour of either vehicle- or PCP-treated rats were determined. Haloperidol did not produce a selective antagonism of PCP, whereas chronic clozapine selectively inhibited the PCP-induced stereotyped behaviour and social isolation. These effects of haloperidol and clozapine suggest that this animal model can determine the effects of neuroleptic drugs on positive and negative symptoms, onset of action, and side-effect profile, including effects on the motor system. Together these data suggest that this may be a possible animal model of the positive and negative symptoms of schizophrenia.