current study due to small effect size, low MAF in our sample, greater variability across populations of differing ethnicity for some of these SNPs (e.g., rs6473797, rs3778151), or our failure to genotype the specific risk-associated SNPs. Given the well-documented involvement of MORs and KORs in the effects of opioids [including important aspects of dependence e.g., see (Christie 2008)] and the close functional interrelationships of these three receptors in which heterodimerization may be integrally involved (Ferré & Franco 2010; von Zastrow 2010) they remain extremely important targets for other avenues of research in order to improve current understanding of the pathophysiology of heroin dependence as well as treatment of this disorder.
