Nociceptors in neuropathic pain and Nav1.7 channels: new insights

Pseudo-unipolar neurons of the dorsal root ganglion have one axon that is divided into two separate branches, one leads impulses from the periphery to the cell body in the ganglion, and one carrying impulses from the body to the spinal cord. These cells start in the periphery. Nociceptors in the peripheral nervous system are these pseudo-unipolar dorsal root ganglion neurons and they possess either unmyelinated or thinly myelinated axons, and are thus responsible for the emergence of pain in neuropathic pain.

Peripheral voltage-gated sodium channels, including Nav1.7, are mainly expressed in the DRG cells, and are seen to be central for understanding the mechanism behind neuropathic pain.

In a recent study the pain behavior and the expression of the Nav1.7 channels in the DGR were studied before and after plantar incision in rats. This can be seen as an acute postoperative pain model.  After the operation, mechanical and thermal pain threshold decreased significantly, the cumulative pain score was increased significantly. Expression of Nav1.7 in the DGR cells was enhanced significantly, and pain behavior could be inhibited by Scn9a Antibodies.

The enhanced expression of sodium channels in the peripheral nerve cells which act as nociceptors support the further development of phenytoin local cream, which inhibits these Nav1.7 channels as well as other sodium channels.

 

Source: Sun J, Li N, Duan G, Liu Y, Guo S, Wang C, Zhu C, Zhang X. Increased Nav1.7 expression in the dorsal root ganglion contributes to pain hypersensitivity after plantar incision in rats. Mol Pain. 2018 Jan 1:1744806918782323. doi: 10.1177/1744806918782323.