Aripiprazole ameliorates phencyclidine-induced impairment of recognition memory through dopamine D₁ and serotonin 5-HT_1A receptors

Rationale: Cognitive deficits, including memory impairment, are regarded as a core feature of schizophrenia. Aripiprazole, an atypical antipsychotic drug, has been shown to improve disruption of prepulse inhibition and social interaction in an animal model of schizophrenia induced by phencyclidine (PCP); however, the effects of aripiprazole on recognition memory remain to be investigated. Objectives: In this study, we examined the effect of aripiprazole on cognitive impairment in mice treated with PCP repeatedly. Materials and methods: Mice were repeatedly administered PCP at a dose of 10mg/kg for 14days, and their cognitive function was assessed using a novel-object recognition task. We investigated the therapeutic effects of aripiprazole (0.01-1.0mg/kg) and haloperidol (0.3 and 1.0mg/kg) on cognitive impairment in mice treated with PCP repeatedly. Results: Single (1.0mg/kg) and repeated (0.03 and 0.1mg/kg, for 7days) treatment with aripiprazole ameliorated PCP-induced impairment of recognition memory, although single treatment significantly decreased the total exploration time during the training session. In contrast, both single and repeated treatment with haloperidol (0.3 and 1.0mg/kg) failed to attenuate PCP-induced cognitive impairment. The ameliorating effect of aripiprazole on recognition memory in PCP-treated mice was blocked by co-treatment with a dopamine D₁ receptor antagonist, SCH23390, and a serotonin 5-HT _1A receptor antagonist, WAY100635; however, co-treatment with a D₂ receptor antagonist raclopride had no effect on the ameliorating effect of aripiprazole. Conclusions: These results suggest that the ameliorative effect of aripiprazole on PCP-induced memory impairment is associated with dopamine D₁ and serotonin 5-HT_1A receptors.