Antinociceptive and anti-inflammatory effects of electroacupuncture on experimental arthritis of the rat temporomandibular joint

This study investigated the antinociceptive and anti-inflammatory effects of electroacupuncture (EA) on zymosan-induced acute arthritis of the rat temporomandibular joint (TMJ). Male Wistar rats were injected with saline or zymosan (control group; 2?mg) into the left TMJ. Low frequency EA (10?Hz, 30?min) was performed at acupoints (LI4, LI11, ST36, ST44) or sham points 2?h after or 1?h before zymosan administration. Mechanical hypernociception was accessed by the electronic Von Frey method after zymosan administration. Rats were sacrificed 6?h after zymosan administration and the joint was removed for histopathological analysis, myeloperoxidase activity assessment, vascular permeability observations, and immunohistochemical verification of inflammatory mediators. The results showed that EA inhibited zymosan-induced hypernociception, compared with the control group and with the sham group (p?< 0.05). The results showed that EA inhibited inflammatory parameters such as neutrophil migration, vascular permeability, and tumour necrosis factor α (TNF-α), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) expression in the TMJ compared with the sham group (p < 0.05). Histopathological analysis showed that EA significantly inhibited edema and periarticular infiltration (p?< 0.05) compared with the control and sham groups. EA at acupoints produced antinociceptive and anti-inflammatory effects on zymosan-induced arthritis in the rat TMJ.