Distinct potassium channels on pain-sensing neurons

Differential expression of ion channels contributes functional diversity to sensory neuron signaling. We find nerve injury induced by the Chung model of neuropathic pain leads to striking reductions in voltage-gated K+ (Kv) c hannel subunit expression in dorsal root ganglia (DRG) neurons, suggesting a potential molecular mechanism for hyperexcitability of injured nerves. Mo reover, specific classes of DRG neurons express distinct Kv channel subunit combinations. Importantly, Kv1.4 is the sole Kv1 alpha subunit expressed i n smaller diameter neurons, suggesting that homomeric Kv1.4 channels predom inate in A delta and C fibers arising from these cells. These neurons are p resumably nociceptors, because they also express the VR-1 capsaicin recepto r, calcitonin gene-related peptide, and/or Na+ channel SNS/PN3/Nav1.8. In c ontrast, larger diameter neurons associated with mechanoreception and propr ioception express high levels of Kv1.1 and Kv1.2 without Kv1.4 or other Kv1 alpha subunits, suggesting that heteromers of these subunits predominate o n large, myelinated afferent axons that extend from these cells.