Effects of continuous D-amphetamine and phencyclidine administration on social behaviour, stereotyped behaviour, and locomotor activity in rats.

D-amphetamine (AMPH) and phencyclidine (PCP) can induce a model psychosis that mimic the positive symptoms of schizophrenia, but only PCP also mimics the negative symptoms. Recent studies in the rat social interaction test have shown that PCP, and not AMPH, induce social withdrawal following single and repeated injections, and this effect may, therefore, be used to model negative symptoms. However, an AMPH psychosis is usually only seen after a prolonged period of repeated injections or continuous administration for 3-5 days of high doses of AMPH. It is, therefore, possible that in these studies, AMPH was administered at insufficient levels in rats, and this may explain its lack of effect. The present study has determined the effects of continuous administration of AMPH (23 to 94 mumol/kg/day; 4.2 to 17 mg/kg/day) and PCP (18 to 107 mumol/kg/day; 5.0 to 30 mg/kg/day) in rats after five days of infusion in the social interaction test and after 6-7 days in standard activity cages. The study found that AMPH and PCP dose-dependently induced stereotyped behaviour and locomotor hyperactivity, behaviours believed to be related to positive symptoms, and that only PCP induced social withdrawal. These findings confirm previous studies that only PCP and not AMPH induce deficits in the social behaviour of rats.