None of the genes identified here is currently associated with a large literature involving substance dependence or disinhibitory behavior. One exception may be the gene NTSR2 that codes for neurotensin receptor 2, a protein that belongs to the G protein-coupled receptor family that activates a phosphatidylinositol–calcium second messenger system. There are previous reports that neurotensin exerts complex effects on the mesolimbic dopamine system that alter motivation and contribute to neuroadaptations associated with psychostimulant drug administration [Garlow et al., 2006; Reynolds et al., 2006]. However, before formulating hypotheses about the potential biological effects of the associated genes, replication in independent samples will be critical.
