Melanocortin-4 receptor in subthalamic nucleus is involved in the modulation of nociception

Deep brain stimulation of the subthalamic nucleus (STN-DBS) stimulation produces significant improvement of overall pain related to Parkinson disease; however, the mechanisms underlying analgesic effects of STN-DBS are still unknown. This report describes direct neuroanatomical evidence for the central melanocortinergic-opioidergic circuits in the STN. We investigated melanocortin-4 receptor (MC4R) and mu-opioid receptor (MOR)-positive expression of the STN in MC4R-GFP transgenic mice using fluorescence immunohistochemical detection. Immunohistochemistry showed a large number of MC4R-GFP- and MOR-positive neurons within the STN region, and approximately 50% of MC4R-GFP-positive neurons coexpressed MOR. The results of this study showed direct neuroanatomical evidence for the central melanocortinergic-opioidergic signaling in the STN region. These findings contribute to the view of melanocortinergic-opioidergic circuits in the subthalamic nucleus as a reliable source of modulating of nociception with therapeutic potential for alleviating pain.