In summary, the identification of a potentially new functional SNP with a substantial minor allele frequency within alternative exons of OPRM1 is of considerable importance to the field of pain genetics. Although the association of SNPs rs563649 with sensitivity to noxious stimuli and morphine responses requires further confirmation in larger cohorts, our results provide strong evidence that this SNP has a far greater effect on receptor function than other currently known OPRM1 polymorphisms. Collectively, our data open conceptually new approaches to examining the structure and function of the OPRM1 gene.
