been shown to decrease receptor coupling and signaling (Befort et al., 2001; Koch et al., 2000; Wang et al., 2001). Other OPRM1 polymorphisms that have been identified and associated with pain or opioid dependence including a short tandem (CA)n repeat (Kranzler et al., 1998), C17T (A6V), which is found primarily in African Americans (Berrettini et al., 1997), and C440G (S147C), which is extremely rare in the general population (MAF< 0.006) (Glatt et al., 2007). To date, none of these polymorphisms have in vitro evidence supporting a functional consequence.
