The involvement of distraction in memory deficits induced by NMDAR antagonism: Relevance to cognitive deficits in schizophrenia

Recognition memory, impaired in neuropsychiatric conditions and currently untreated, may be assessed by the novel object recognition (NOR) task with robust impairments induced by sub-chronic treatment with the N-methyl-d-aspartate receptor antagonist phencyclidine (PCP). The aim of the present study was to investigate how sub-chronic PCP produces its effects in this task. Forty adult female rats received vehicle or PCP (2 mg/kg i.p. twice daily for 7 days followed by 7 days washout). Rats completed a 3-min acquisition trial followed by differential inter-trial-interval (ITI) conditions (1 min in the home cage, 10 s in the home cage, 1 min in the NOR test box in the presence of an unfamiliar object or 1 min in the NOR test box completely undisturbed) followed by a 3-min retention trial. Control rats spent significantly more time exploring the novel compared with the familiar object in retention. This effect was abolished in the sub-chronic PCP treated animals following all ITI conditions except in rats left completely undisturbed in the NOR test box for a 1 min ITI. The combined influence of sub-chronic PCP treatment and the effect of distraction provides further support for the validity of the NOR test in mimicking cognitive deficits of relevance to schizophrenia.