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OBJECTIVE: The aims of this study were to investigate the protective effect of quercetin on changes in recognition memory as assessed by the novel object recognition (NOR) test, as well as on changes in the oxidative stress levels in the hippocampus and prefrontal cortex, produced in a model of memory impairment in schizophrenia induced by administration of a subanesthetic dose of ketamine.
METHODS: A total of 40 Balb-C mice were randomly divided into five groups (Corn oil + Saline, Quercetin 50 + Saline, Corn oil + Ketamine, Quercetin 25 + Ketamine, Quercetin 50 + Ketamine). Corn oil and Quercetin (25 or 50 mg/kg/day) was given by orogastric gavage once daily for 21 days. Corn oil was chosen as the vehicle and administered at the same volume as quercetin. Ketamine was injected at a dose of 25 mg/kg intraperitoneally (i.p.) for a period of 7 days starting from the 15th day. Behavioural responses were evaluated with the NOR test. The activity levels of antioxidant enzymes and levels of malondialdehyde (MDA) were assayed in the prefrontal cortex and hippocampus.
RESULTS: The time of exploration of the novel object was longer than TF (time to explore the familiar object) in the Corn oil + Saline and Quercetin 50 + Saline groups in NOR Test-1 (p < .05). The discrimination ratios of the Quercetin 50 + Ketamine and Corn oil + Ketamine groups were significantly lower than that of the Quercetin 50 + Saline group (p < .05). The discrimination ratios of the Quercetin 50 + Ketamine and Corn oil + Saline groups were significantly lower than that of the Quercetin 50 + Saline group (p < .05). The time of exploration of the novel object was longer than TF in the Corn oil + Saline and Quercetin 50 + Ketamine groups in NOR Test-2 (p < .05). The discrimination ratios of the Corn oil + Ketamine and Quercetin 25 + Ketamine groups were significantly lower than those of the Quercetin 50 + Ketamine group (p < .05). Quercetin at 50 mg/kg reduced the MDA levels and elevated the SOD and GPx activity compared to the Corn oil + Ketamine group.
CONCLUSION: These results show that quercetin has the potential to improve cognitive deficits in mice and that quercetin may be useful for treating the symptoms of schizophrenia, partially due to its ability to scavenge free radicals and its high antioxidant capacity