Effect of infra-red low-power laser irradiation on regeneration of myelinated axons

The purpose of the present study was to examine the regeneration of myelinated axons under the effect of laser irradiation at various wavelengths and energy densities. Laser irradiation at 890 nm with an energy dose of 0.33 J cm(-2) as well as He-Ne laser irradiation failed to change the number of regenerating myelinated axons in distal nerve stumps on the 30th day after cutting the nerve. An increase of dose delivered to the skin to 9.33 J cm(-2) resulted in a 49% decrease in the number of myelinated axons. A 24% suppression of nerve regeneration was also registered using 1220 nm wavelength laser (dose 0.98 J cm(-2)). This phenomenon is likely to be attributed to the stimulating effect of laser irradiation of the near-infra-red range on proliferation of fibroblasts and scar formation. 1220 nm of 7.2 J cm(-2) dose effected neither the growth nor the myelinization of axons in distal nerve stumps on the 20th day following nerve damage.