The poor recovery from peripheral nerve injuries (PNIs), found in a large number of Americans, is a significant public health issue. Moderate exercise and brief electrical stimulation have emerged as the most effective experimental treatments for PNI, but adapting them to patient use has proven difficult. Bioluminescent optogenetics (BL-OG) uses excitatory luminopsins, light-sensing ion channels fused with a light-emitting luciferase. When exposed to a cognate substrate (coelenterazine, CTZ), bioluminescence is generated by the luciferase moiety and the attached opsin is activated. If injured neurons are induced to express an excitatory luminopsin, they would be activated by this bioluminescence, stimulating the regeneration of their axons. In this project we will use BL-OG to treat nerve injuries in a manner that might be used in human patients. Two critical aspects of that strategy will be addressed now: Investigating the effectiveness of CTZ administration to excite neurons induced to express an excitatory luminopsin, using gene therapy after nerve injury, without exacerbating the pain that often accompanies PNI; and whether this excitation of injured neurons using BL-OG will enhance axon regeneration when nerve repair is delayed to allow for effective gene therapy. The bioluminescence produced during BL-OG will be exploited to evaluate the pharmacodynamics of CTZ in a clinically relevant mouse model of peripheral nerve injury. The effectiveness of treatment with CTZ on axon regeneration will be studied using electrophysiological and neuro-anatomical outcome measures in a well-established mouse model of peripheral nerve injury. We anticipate that the results of this exploratory/developmental research will provide a clear resolution to the fundamental obstacle to advancement of the use of an exciting new technology.