A nociceptive neuronal ensemble in dorsomedial prefrontal cortex underlies pain chronicity

The prefrontal cortex (PFC) actively participates in a variety of cognitive functions, but distinct neuronal subpopulations may be engaged in different behaviors. Pain chronicity involves unpleasant experience in both somatosensory and affective aspects, and is accompanied by neuroplastic alterations of the PFC. However, whether specific PFC neuronal ensembles underlie pain chronicity remains elusive. Here we identified via c-fos screening and in vivo two-photon calcium imaging a nociceptive neuronal ensemble in the dorsomedial prefrontal cortex (dmPFC), which showed prominent reactivity to nociceptive stimuli. RNA sequencing combined with virus tracing revealed that this ensemble showed distinct molecular characteristics and was densely connected to pain-related regions including basolateral amygdala (BLA) and lateral parabrachial nuclei (LPB). Prolonged chemogenetic activation of this nociceptive neuronal ensemble, but not a randomly transfected subset of dmPFC neurons, induced chronic pain-like behaviors including persistent mechanical allodynia, thermal hyperalgesia, conditioned place preference to morphine, and anxiety-like behaviors in normal mice. By contrast, silencing laser-induced nociceptive dmPFC neurons relieved both pain hypersensitivity and anxiety in mice with chronic inflammatory pain. These results suggest the presence of specific dmPFC neuronal ensembles in processing nociceptive information and regulating pain chronicity.