Toward a Selective, Reversible Optigenetic Block of Peripheral Nerve Conduction

As much as 8% of the general population suffers from chronic pain of a neuropathic origin. Peripheral neuropathic pain arises from damage to peripheral sensory nerves. Hypersensitization and increased spontaneous signaling in pain fibers have been shown to occur in damaged afferent nerves, resulting in episodes of chronic, persistent pain in absence of actual nociceptive stimuli. Small, unmyelinated, slow-conducting C-fibers carry the type of lingering, burning pain often associated with chronic neuropathic pain. As a result, the field of neural engineering continues to seek improvements to methods that block conduction in C-fibers in a selective, reversible way. In this paper we report initial evidence of nerve block achieved using the thy1:ChR2-YFP mouse line, which expresses the optogenetic transmembrane protein Channelrhodopsin-2, a blue-light-gated cation channel. We hypothesize that exposure to light depolarizes a section of the sciatic nerve sufficiently enough to achieve a depolarization block. Interesting features of the block include a visible recovery and a 9-second linear decrease in EMG amplitude before a steady state is reached.