Chloride Dysregulation through Downregulation of KCC2 Mediates Neuropathic Pain in Both Sexes

Summary: The behavioral features of neuropathic pain are not sexually dimorphic despite sex differences in the underlying neuroimmune signaling. This raises questions about whether neural processing is comparably altered. Here, we test whether the K+-Cl− co-transporter KCC2, which regulates synaptic inhibition, plays an equally important role in development of neuropathic pain in male and female rodents. Past studies on KCC2 tested only males. We find that inhibiting KCC2 in uninjured animals reproduces behavioral and electrophysiological features of neuropathic pain in both sexes and, consistent with equivalent injury-induced downregulation of KCC2, that counteracting chloride dysregulation reverses injury-induced behavioral and electrophysiological changes in both sexes. These findings demonstrate that KCC2 downregulation contributes equally to pain hypersensitivity in males and females. Whereas diverse (and sexually dimorphic) mechanisms regulate KCC2, regulation of intracellular chloride relies almost exclusively on KCC2. Directly targeting KCC2 thus remains a promising strategy for treatment of neuropathic pain in both sexes. : Neuropathic pain arises in males and females through distinct neuroimmune signaling. Yet the behavioral (or clinical) features of neuropathic pain are not sexually dimorphic. Mapplebeck et al. demonstrate that KCC2—though regulated in multiple, sex-specific ways—is uniquely responsible for the synaptic disinhibition causing neuropathic pain in both sexes. Keywords: K+-Cl− co-transporter KCC2, sex differences, degeneracy, neuropathic pain, disinhibition, GABA, glycine, BDNF