To date, however, few studies have examined the relationship between genetic variations in GIRK channels and phenotypic differences in humans, although several studies have identified human GIRK channel gene polymorphisms [16]–[18]. Therefore, the present study focused on GIRK channel gene polymorphisms, particularly those of the KCNJ6 gene encoding GIRK2 because it has been investigated more extensively than the other subtypes with regard to its involvement in analgesia [6], [7], [13]–[15]. We sought to reveal the relationship between genetic variations in the KCNJ6 gene and individual differences in opioid analgesic sensitivity.
