Opposing effects on descending control of nociception by mu and kappa opioid receptors in the anterior cingulate cortex.

ACC kappa opioid receptor activation therefore diminishes descending control of nociception both in naïve animals and as an adaptive response to chronic pain likely by enhancing net descending facilitation. DCN can be restored by activation of mu opioid receptors in the ACC, but also by kappa opioid receptor antagonists, providing a nonaddictive alternative to opioid analgesics. NMRA-140 is now in advanced clinical trials.