The Influence Of A Positive Environment On Nicotine Self- Administration. A Gene-Environment Interaction Study
Genetic vulnerabilities can predispose individuals to develop psychological disorders. One of these disorders is a tobacco use disorder characterised by dependency on nicotine. A polymorphism in the serotonin transporter gene can result in a greater likelihood of developing psychological disorders. This polymorphism can be mimicked in rats by disrupting the serotonin transporter gene. Using an animal model allows us to examine the influence of factors such as the environment. It is suggested that housing rats in an enriched environment can protect against disorders. In the current study, serotonin knockout and wild type rats were housed in either environmental enrichment or standard housing. Self- administration acquisition was assessed, followed by extinction, reinstatement, and progressive ratio testing. Environmental enrichment exhibited protective effects during the acquisition stage in knockout rats genetically predisposed to nicotine dependence, but not in wild type rats. Rats in standard housing extinguished cue-induced reinstatement responding to a greater extent than rats in enrichment, but also showed a marginal increase in responding during extinction. Contrary to predictions, rats in standard housing were not more likely to self-administer nicotine compared to rats in enrichment, nor were their break points higher in progressive ratio. The findings of this study help to understand the mechanisms underlying genetic and environmental vulnerabilities of nicotine dependence, suggesting a gene x environment interaction in nicotine dependence. Thus, it is important to not only treat the dependence, but also consider environmental effects and psychological disorders to find an effective treatment, whether it be through therapy, pharmacology, or a combination.