Effects of Nicotine Administration in an Enriched Environment on the Behavior of Male MK-801-Exposed Rats

Smoking is more common in patients with schizophrenia than in healthy populations. Some controversial hypotheses connect the disease with the high prevalence of smoking. Moreover, environmental factors affect the severity of the positive and negative symptoms of schizophrenia. The current study aimed to assess the effect of enriched environment (EE) and nicotine on the MK-801 animal model of schizophrenia. Male Wistar rat pups randomly received saline or MK-801 (dose:1 mg/kg) for five days from the sixth postnatal day (P) until the tenth. The pups were placed in EE or standard cages (SCs) after weaning (P21). Morris water maze (MWM) was used to assess spatial learning and memory. The rats received 0.6 mg/kg nicotine twice for three days at the end of the second month and were examined in an open-field box and three-chamber social interaction test. MK-801 rats’ behaviors were the same as those of the saline rats when they were exposed to nicotine. No positive effects of EE were observed when the animals were exposed to nicotine.  The results suggested that nicotine decreased schizophrenia-like symptoms and covered the positive effects of EE.