The molecular biology of mu opioid receptor

Abstract

Opiates remain important drug treatment in severe pain. The opioid system consists of endogenous opioid peptides and mu, delta and kappa opioid receptors which are target molecules for analgesia, reward and many physiological functions of opiates. The powerful analgesic effects of morphine and related drugs focus attention on morphine-preferring mu opioid receptors. Analgesia, reward, respiratory depression, constipation, immunosuppression and physical dependence induced by morphine are absent in mice lacking the mu opioid receptor. These data show that the mu receptor is the critical molecular target for most effects of morphine, both therapeutic effects and side effects. Mice lacking the mu receptor which we and other groups generated will be a useful tool to study complex opioid systems. We have also analyzed individual differences of human mu receptor gene. We have been studying possible relationship between individual genetic variance and effects of opioids for development of custom-made individualized treatment on pain.