Effects of environmental enrichment on reinstatement of methamphetamine-induced conditioned place preference

Objective: The influence of environmental enrichment (EE) on reinstatement to methamphetamine (METH) seeking in rat model was investigated. Methods: Wistar rats were divided to receive saline (1 ml/kg) or METH (1 mg/kg, i.p.) for 8 days during the conditioning training in the conditioned place preference (CPP) paradigm, which is one of the most popular models to study the motivational effects of drugs and non-drug treatments in experimental animals. Rats were then kept in either isolated (IE) or enriched environment (EE) for 30 days during the extinction training. Animals were finally examined for reinstatement provoked by i.p. injections of METH. Results: Saline injections during the conditioning phase did not change CPP during reinstatement in animals of IE or EE control groups. METH injections reinstated place preference in the IE animal group. Interestingly, EE significantly blocked this reinstatement effects of METH. Conclusion: These results show the important role of social interactions and positive environment conditions in preventing reinstatement to drug use.