The OPRK1 5′ region and first exon, from −2312 (numbering here is relative to the translational start site ATG in RefSeq NM_000912) to +453, were amplified from 16 human genomic DNAs, eight from individuals with the higher risk haplotype and eight with the lower risk haplotype previously described (17). Primers (Table 1) were designed on the basis of the NCBI reference genome contig (NT_008183.18). We used the primer pairs shown in Table 2 to amplify the region from −2312 to +452 in four overlapping fragments. PCR products were directly sequenced using the ABI BigDye Terminator Cycle Sequencing Kit (Applied Biosystems, Foster City, CA, USA) and separated on an ABI 3100 Genetic Analyzer (Applied Biosystems). Sequences were aligned using MacVector (MacVector Inc., Cary, NC, USA), and polymorphic sites were checked on the electropherograms. New sequences were submitted to dbSNP (SNPs: rs35970029, rs34418807, rs35991105, rs34709943, rs35373196, rs35160174; indel rs35566036).
