Most clinically used opioid drugs including morphine, fentanyl and oxycodone, as well as drugs of abuse such as heroin, act through mu opioid receptors. Over the past two decades, my laboratorys’ research has been focusing on mu opioid receptors, particularly alternatively spliced mu opioid receptor variants or isoforms, towards our main goals to understand molecular and cellular mechanisms of mu opioid actions and to translate our basic research into development of novel opioid analgesics that have potent analgesic actions devoid of side effects. Our research utilizes multidisciplinary in vitro and in vivo approaches, including molecular biology, biochemistry, pharmacology, and behavioral studies, as well as gene targeting animal models.