Participation of IL-1β in temporomandibular nociception in rats with CFA-induced inflammation

ABSTRACT

The aim of the present study was to develop an animal model for evaluation of temporomandibular (TMJ) nociception under TMJ inflammation. We also investigated the participation of IL-1β in inflammation-induced TMJ nociception. Experiments were carried out using male Sprague-Dawley rats. Intra-articular injection of 3% formalin was administered to evaluate hyperalgesia 3 days after CFA injection. Intra-articular injection of 3% formalin did not produce nociceptive behavior in normal rats. Although intra-articular injection of 3 doses of CFA produced TMJ inflammation, only 13 diluted CFA produced hyperalgesia when formalin was injected intra-articularly 3 days after CFA injection. Co-administration of IL-1 receptor inhibitor with formalin into the TMJ cavity 3 days after CFA injection was performed. Co-administration of IL-1 receptor inhibitor significantly inhibited formalin-induced hyperalgesia in rats with CFA-induced TMJ inflammation. These results suggested that intra-articular injection of formalin produced hyperalgesia under chronic TMJ inflammation. Moreover, IL-1β plays an important role in TMJ hyperalgesia under chronic inflammation and blockade of IL-1β is a potential therapeutic target for inflammatory TMJ pain.