Using our combined population (N=489; 248 controls, 241 opioid abusers, see Supplemental Table 4 for demographics), we genotyped 11 SNPs within DRD1, HOMER1 and DLG4 (see Supplemental Table 3 for list of SNPs tested), and evaluated their association with opiate use. We found significant association for one DRD1 SNP (rs686), one DLG4 SNP (rs507506) and one HOMER1 SNP (rs4323213) with opiate use (P<0.05, Table 1). When Caucasians and African Americans were examined separately, we found significant associations for two DRD1 SNPs (rs265975 and rs265973) and two DLG4 SNPs (rs2521985 and rs507506) in the Caucasian population (N=286, 128 controls and 158 opioid abusers), and a significant association for one DRD1 SNP (rs686) in the African American population (N=187, 113 controls and 74 opioid abusers) (P<0.05, Table 1). A trend for association in HOMER1 (rs4323213, P=0.081) was also seen in African Americans. Thus, associations for DRD1 and post-synaptic glutamatergic genes with opioid use/abuse were seen within each race though the individual SNPs that were implicated differed.
