TRPV1 and TRPA1 are cooperatively involved in the tooth movement-related pain.

Abstract

Electrical stimulation to periodontal ligament induces the jaw-opening reflex. Due to pain, the threshold for inducing jaw-opening reflex was significantly reduced when orthodontic force was applied to the tooth. The application of orthodontic force excites the trigeminal ganglia, as well as other peripheral pain, which is associated with expression of GFAP (Glial fibrillary acidic protein) in the satellite glial cells in V 1 and V 2 regions. In addition, the intraperitoneal administration of TRPV1 antagonist or the thermal stimulation (e.g., laser irradiation) to periodontium significantly inhibited orthodontic force-induced excitation of jaw-opening reflex and trigeminal ganglia. Recently, the conjugational function of TRPV1 and TRPA1 to inflammation has been reported, and both receptors are widely present in peripheral nervous systems. Thus, the effects of topical administration of TRPV1 and or TRPA1 antagonists to cervical gingiva on alteration of the tooth movement-related pain and the trigeminal excitability were examined. Each TRP antagonist expressed an analgesic effect on tooth movement-related pain; however, trigeminal excitation was not inhibited. Moreover, the co-administration of both TRP antagonists significantly increased the analgesic effect without inducing general/local temperature alteration. Taken together, the cooperative effect of TRP antagonists may play a critical role in controlling tooth movement-related pain.