The purpose of this study was to analyze the effects of low-power laser therapy (LLLT) on nociceptive behavior and neuronal activity of the trigeminal nucleus after unilateral disc injury of the temporomandibular joint (TMJ) in rats. Forty rats were used. Surgical access was made to the TMJ under general anesthesia. The animals were divided into 4 groups (n=10): Group 1: Surgical lesion of the articular disc and LLLT; Group 2: Sham - operated and LLLT; Group 3: Surgical lesion of the articular disc; Group 4, Naive: control without articular lesion or LLLT. Ten sessions of LLLT were carried out using a GaAs laser with a wavelength of 904 nm and an energy density of 6J/cm2. The development of neuropathic symptoms was assessed using the Von Frey test. Trigeminal ganglion samples were prepared for determination of protein expression of substance P (SP), transient receptor potential vanilloid subtype-1 (TRPV-1) and calcitonin gene-related peptide (CGRP). Statistical analysis was performed (p