ABSTRACT
Gender differences in psychiatric research are becoming more widely recognized, and changes in levels of the steroid hormone, oestrogen, over the menstrual or oestrous cycle are becoming increasingly implicated in alterations in cognitive strategies and capacities. The aim of this study is to investigate the interaction between oestrogen, NMDA receptor function and cognitive processing in rats. Forty-five mature female hooded-Lister rats received vehicle, 0.5, 5 or 10 microg/kg of oestradiol benzoate (EB, s.c. in olive oil) 24 h prior to an acute dose of 2 mg/kg phencyclidine (PCP, i.p. in 0.9% w/v saline), or vehicle (0.9% saline). After 30 min following PCP treatment, animals completed the novel object recognition task with a 1 min inter-trial interval to assess object recognition memory. Results show that 5 and 10 microg/kg of EB 24 h prior to 2 mg/kg PCP significantly (P < 0.01 and < 0.001, respectively) protected against the cognitive impairing effect of PCP in contrast to vehicle and 0.5 microg/kg EB plus PCP (not significant). EB may exert a neuromodulatory effect in this animal model leading to attenuation of the PCP-induced impairment in object recognition memory, suggesting an interaction between the gonadal steroids and NMDA receptor-mediated cognitive dysfunction, which is of potential relevance to schizophrenia.