The aim of this study was to identify biochemical changes in sciatic nerve (SN) after
crush injury and
low-level laser therapy (
LLLT) with 660 nm and 808 nm by Raman spectroscopy (RS) analysis. A number of 32 Wistar rats were used, divided into four groups (control 1, control 2,
LASER 660 nm, and
LASER 808 nm). All animals underwent
surgical procedure of the SN and groups control 2,
LASER 660 nm, and
LASER 808 nm were submitted to SN crush damage (
axonotmesis). The
LLLT in the groups
LASER 660 nm and
LASER 808 nm was applied daily for 21 consecutive days (100 mW, 30 s, 133 J/cm2 fluence). The hind paw was removed and the SN was dissected and positioned on an
aluminum support to collect dispersive Raman spectra (830 nm excitation, 30 s accumulation). To estimate the biochemical changes in the SN associated with
LLLT, the principal component analysis (PCA) was applied. The Raman spectra of the sciatic nerve fragments showed peaks of the major biochemical components of the nerve, especially
sphingolipids,
phospholipids,
glycoproteins, and
collagen. The spectral features identified in some of the principal component loading vectors are referred to the biochemical elements present on the SN and were increased in the groups treated with
LLLT, mainly
lipids (sphingo and
phospholipids) and
proteins (
collagen)-constituents of the myelin sheath. The RS was effective in identifying the biochemical differences in the SN after the
crush injury, and
LASER 660 nm was more efficient than the
LASER 808 nm in cell proliferation and repair of the injured SN.