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

Abstract : 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 (2mg/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, 10s 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.