[Nicotine and animal models: what does the environmental enrichment paradigm tell us?].

The Environmental Enrichment (EE) paradigm is a housing condition which aims is to provide physical, cognitive and sensorial stimulation to rodents. Animals are housed in larger cages containing inanimate objects such as tunnels, toys and running wheels. The main aim of the current work is to tackle the arguments which suggest that EE may diminish vulnerability to developing addiction to nicotine and other drugs of abuse and to review recent experimental studies performed in relation to this subject. We discuss the major changes induced by EE at physical, neurobiological and behavioral levels and review the results of recent studies which indicate that EE promotes both neurochemical (potentiation of the increase in dopamine release induced by nicotine in the brain cortex) and behavioral changes (increased ability to discriminate the presence of reward and decreased impulsivity), thus supporting the hypothesis put forward. In light of these results, EE can be proposed as a model for the study of vulnerability to addiction to different drugs of abuse, including cocaine and nicotine, though further studies are needed in order to establish the neurobiological implications of the effects of exposure to enriched environments and their possible relationship with changes in brain reward systems.