Effects of repeated treatment of phencyclidine on cognition and gene expression in C57BL/6 mice

A number of studies indicate that glutamatergic N-methyl-D-aspartate (NMDA) neurotransmission is disturbed in schizophrenia partly based on the findings that NMDA receptor antagonists such as phencyclidine (PCP) can reproduce a schizophrenia-like syndrome in both humans and rodents. This study investigated whether repeated administration of low doses of PCP can induce cognitive dysfunctions in mice at doses which produce no sensorimotor disturbances. In addition, the effects on cognition were related to the expression of two genes, Arc and spinophilin, which have been related to neuronal plasticity and learning. Adult male C57Bl/6J mice received daily s.c. doses of PCP (0.5-2.0 mg/kg) or saline for 7 d. Testing was performed 24 h after the last day of treatment. Only the 2.0 mg/kg PCP dose produced a consistent impairment in spatial learning and working memory performed in the water-maze task without any apparent sensorimotor deficits. Importantly, the 2.0 mg/kg PCP dose produced no impairment in a non-spatial learning paradigm in the water-maze task. PCP treatment altered Arc mRNA levels in the hippocampus and retrosplenial agranular cortex while leaving the striatum and prefrontal cortex unaffected. The mRNA expression of spinophilin was down-regulated in striatum by repeated PCP treatment. These results demonstrate that repeated treatment with low doses of PCP in mice can produce specific cognitive deficits which are associated with alterations in gene expression in brain regions that appear to play a role in the pathophysiology of schizophrenia. These results suggest that the low-dose PCP model may have significant potential in characterizing the behavioural and molecular mechanisms underlying cognitive deficits seen in schizophrenia patients.