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1PsychoGenics, Inc., Paramus, NJ, USA

Social withdrawal and impaired cognitive function have been associated with the negative symptoms of schizophrenia. Individuals with schizophrenia and depression show evident deficits in social interaction and social recognition. The social recognition or social memory task is an ethologically relevant learning and memory test used in lab animals, especial in rodents. This test is mostly based on the rat’s olfactory discriminative capacities and it takes advantage of animal’s innate desire to investigate its conspecifics. In rodents, social recognition has been used to evaluate the efficacy of antidepressants and antipsychotics.

Rats treated with the NMDA receptor antagonist Phencyclidine (PCP) showed deficits in social interaction and social recognition. In the reciprocal social interaction paradigm, atypical antipsychotic treatments showed efficacy in reversing PCP-induced deficits and increased interaction time following acute administration. In the social recognition test in which rats were given 4 trials of exploration of a familiar stimulant rat and a 5th trial where they are exposed to a novel stimulant rat, PCP-treated rats showed no recognition of the novel rat and their interaction time was significantly reduced compared to saline-treated rats. Treatment with either clozapine or olanzapine significantly reversed PCP-induced deficit of recognition memory. These results confirm that assays can serve preclinical models for the negative symptoms of schizophrenia and can be used to screen novel therapeutics.