New vistas in opioid control of pain

The mu-opioid receptors mainly contribute to the control of pain transmission, while a number of splice variants may have different physiological roles. In fact, some mu-opioid receptor agonists show distinct antinociceptive properties probably mediated via splice variants insensitive to traditional mu-opioid receptor agonists. These atypical mu-opioid receptor agonists are extremely effective against morphine-resistant interactive pain and lack the psychological dependence liability. mu-Opioid receptor splice variants specific for these atypical agonists may be the target for better analgesics effective against morphine-resistant interactive pain and lacking psychological dependence liability.