the major 118A allele (118AA genotype; n=16) of the OPRM1 polymorphism; 2) individuals carrying one or two copies of the variant 118G allele (118AG or 118GG genotype; because no subject with the rare 118GG genotype was in fact found, this group is hereafter called 118AG; n=12) of the OPRM1 polymorphism. Genotyping was on DNA from whole blood. SNP rs1799971 (A/G) was genotyped using the assay-on-demand (assay ID: C_8950074_1) from Applied Biosystems (Foster City, CA, USA). The alleles were discriminated by post-PCR plate read on ABI PRISM® 7900HT Sequence Detector System (Applied Biosystems).
