Abstract The aim of this study was to evaluate the effectiveness of 3 different fluences of low-level laser therapy (LLLT) in intermediate period of spinal cord repair using an experimental model in rats.

Thirty two rats were randomly divided into four experimental groups:

Control Group (CG); Laser treated group 500 J/cm² (L-500); Laser treated group 750 J/cm² (L-750) and Laser treated group 1000 J/cm² (L-1000). Spinal cord injury (SCI) was performed by an impactor equipment (between 9th and 10th thoracic vertebrae), with a pressure of 150 kdyn. Afterwards, the injured region was irradiated daily for 14 consecutive sessions, using an 808 nm laser, at the respective fluence of each experimental groups. Locomotor function and tactile sensitivity were performed on days 1 and 15 post-surgery. Animals were euthanized 15 days post-surgery and samples were retrieved for histological and immunohistochemistry analysis. Functional behavior and tactile sensitivity were improved after laser irradiation. Moreover, higher fluencies of LLLT reduced the volume of injury. Additionally, LLLT produced a decreased CD-68 expression. These results demonstrated that, for an intermediate period of SCI repair, LLLT at higher fluences, was effective in promoting functional recovery and modulating the inflammatory process in the spinal cord of rats after traumatic SCI.