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Previous studies examining the focal application of photobiomodulation (PBM) on nerves have consistently yielded reductions in small-diameter fiber activity lasting multiple days. Experiments demonstrating that PBM applied to the sciatic nerve following selective small-diameter fiber excitation would provide further evidence that PBM reduces sensitivity of small-diameter fibers. To investigate this, focal PBM was applied to the rat sciatic nerve, a capsaicin solution was injected into the hind paw, and behavioral data were collected following PBM application. Small fiber heat sensitivities were reduced by over 20% for days following treatment, but mechanical sensitivities were only reduced for one day. To understand translational opportunities, we measured additional effects: focal PBM’s effect on tissue temperature, and PBM’s effect on motor fiber output of the gastrocnemius. Focal PBM application to the sciatic nerve caused an average temperature change of 5oC, and the force generation of the gastrocnemius did not vary following PBM application. Taken together, these data support focal PBM’s translational appeal as a non-addictive, prolonged, pain-reducing therapy.
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