Opioids are widely prescribed pain relievers with multiple side effects and potential complications. They produce analgesia via G-protein-protein coupled receptors: mu-, delta-, kappa-opioid and opioid receptor-like 1 receptors. Bivalent ligands targeted to the oligomerized opioid receptors might be the key to developing analgesics without undesired side effects and obtaining effective treatment for opioid addicts. In this review we will update the biological effects of mu-opioids on homo- or hetero-oligomerized mu-opioid receptor and discuss potential mechanisms through which bivalent ligands exert beneficial effects, including adenylate cyclase regulation and receptor-mediated signaling pathways.
