Comparison of different low-level laser therapy wavelengths in the soleus of Wistar rats after nerve injury

ABSTRACT Skeletal muscles may be affected by peripheral nervous system injuries, leading to muscle weakness and atrophy. Several therapeutic resources may be used in the attempt to recover the functionality of muscles, such as low-level laser therapy (LLLT). This study compared the effect of LLLT of two wavelengths (660 nm and 830 nm) on morphological characteristics of muscle tissue after axonotmesis of ischiatic nerves of Wistar rats. A total of 32 Wistar rats were divided into four groups: G1 (control), G2 (injury), G3 (injury and treatment with 660 nm LLLT) and G4 (injury and treatment with 830 nm LLLT). G2, G3, and G4 animals were submitted to sciatic nerve damage and, three days after the injury, G3 and G4 were treated with LLLT of 660 nm and 830 nm, respectively. After the treatment, all animals were euthanized, and the soles muscles were collected to perform morphological analyzes of the tissue using histological slides. We verified that animals submitted to the lesion underwent morphological changes in the fiber, resulting in their atrophy. We also noticed that LLLT with a wavelength of 830 nm presented slight signs of recovery of the morphometric characteristics analyzed.