Heat But Not Mechanical Hypersensitivity Depends on Voltage-Gated CaV2.2 Calcium Channel Activity in Peripheral Axon Terminals Innervating Skin

Voltage-gated Ca(V)2.2 calcium channels are expressed in nociceptors at presynaptic terminals, soma, and axons. Ca(V)2.2 channel inhibitors applied to the spinal cord relieve pain in humans and rodents, especially during pathologic pain, but a biological function of nociceptor Ca(V)2.2 channels in processing of nociception, outside presynaptic terminals in the spinal cord, is underappreciated. Here, we demonstrate that functional Ca(V)2.2 channels in peripheral axons innervating skin are required for capsaicin-induced heat hypersensitivity in male and female mice. We show that Ca(V)2.2 channels in TRPV1-nociceptor endings are activated by capsaicin-induced depolarization and contribute to increased intracellular calcium. Capsaicin induces hypersensitivity of both thermal nociceptors and mechanoreceptors, but only heat hypersensitivity depends on peripheral Ca(V)2.2 channel activity, and especially a cell-type-specific Ca(V)2.2 splice isoform. Ca(V)2.2 channels at peripheral nerve endings might be important therapeutic targets to mitigate certain forms of chronic pain.

Automated summary

Functional Ca(V)2.2 channels in peripheral axons innervating skin are required for capsaicin-induced heat hypersensitivity, which may be an important therapeutic target for certain forms of chronic pain.