Genetic studies estimate that 65-78% of the vulnerability risk for cocaine dependence is heritable (Kendler and Prescott, 1998); however, identification of genetic susceptibility factors has been difficult due to the complex mode of inheritance and clinical heterogeneity. Dopaminergic brain systems have been implicated to play a major role in drug reward (Hyman et al., 2006), thus making genes involved in these circuits plausible candidates for influencing susceptibility to substance use disorders. The dopamine receptor (D3)gene (DRD3) encodes an inhibitory dopamine receptor and is expressed mainly in discrete areas of the limbic system, implicated in drug reward pathways (Pierce and Kumaresan, 2006). Converging anatomical, pharmacological, and behavioral evidence implicates dopamine D3 receptors in the mechanisms underlying drug seeking behavior and drug reward (Garner and Baker, 1999). In this study we tested the hypothesis that variation in the DRD3gene increases susceptibility to cocaine dependence in individuals of African descent.
