A genetically defined mPFC-thalamic circuit underlies pain chronicity

Chronic pain is a major health care problem with great social and economic consequences. Although the medial prefrontal cortex (mPFC) and the thalamus have been implicated in regulating pain, whether and how these regions may involve in pain chronification process have remained largely unknown. Here, we show that Foxp2+ neurons in mPFC, which are corticothalamic (CT) neurons representing the major mPFC output to thalamus, are deactivated in chronic inflammatory pain. Interestingly, prolonged, but not short-term, inactivation of the Foxp2+ neurons in mPFC increases the sensitivity to noxious stimulations. Conversely, chemogenetic activation of this neuronal cluster induces robust antinociceptive effects in both naïve mice and mice with chronic inflammatory pain. Furthermore, we found that the mPFC Foxp2+ neurons project to several thalamic relay nuclei and that activation of the mPFC to the parataenial nucleus of thalamus (PTN) circuit relieves pain. Finally, RNA-seq of the mPFC Foxp2+ neurons revealed that many genes related to neuronal activity are dysregulated in mice with chronic inflammatory pain. Collectively, our studies revealed that Foxp2+ neurons in mPFC that project to thalamus play a critical role in somatosensory processing and pain chronification. 4 weeks after the bilateral injection of AAV expressing KASH-GFP in the mPFC of Foxp2-Cre mice, the mice were euthanized by inhalation of CO2 and the brains were rapidly removed to a matrix and mPFC was dissected with scalpals. The 3 replicates are collected for each pain and control condition.