Impact of A118G polymorphism on the Mu opioid receptor function in pain

Abstract

Mu Opioid Receptor (MOR) activation by exogenous or endogenous agonists causes reduction of pain threshold after a noxious stimulus, relieving pain sensation.MOR is encoded by OPRM1 gene and its messenger RNA suffers extensible modifications by alternative splicing and single nucleotide polymorphisms (SNPs). A118G (N40D) is the most frequent encoding MOR SNP in humans. In this review we discuss the impact of this polymorphism at molecular, cellular and clinical levels. Since some SNPs are unequally distributed among human populations, we also discuss the utility of A118G as an ethnicity marker among worldwide human populations. As an example, we evaluate A118G frequency in an Argentinean humanpopulation and compare it with worldwide frequencies extracted from HapMap database.