Cellular mechanism for anti-analgesic action of agonists of the kappa-opioid receptor

The analgesic effect of opioids primarily activates the mu-opioid receptor but has a similar effect on the kappa-receptor, whose role is less clear. While kappa-receptors produce analgesia, they are also found to antagonize morphine analgesia. New research shows that the activation of the kappa-receptor specifically antagonizes analgesia induced by the mu-receptor. The finding suggest new approaches to the treatment of opioid addiction and pain control.