Fabeeha Ahmed

Temporomandibular disorder (TMD), a disorder associated with the temporomandibular joint (TMJ), can cause chronic pain within the jaw. Furthermore, estrogen status in females has been reported to significantly affect the incidence of TMD and alters the response properties of TMJ neurons. The trigeminal ganglia (TG) innervates the head, oral cavity and the TMJ and is closely associated with pain in TMD. Satellite glial cells (SGCs) surround sensory neurons within the TG and gap junctions between SGCs relay sensory information to neurons. Connexin 43 (Cx43) is a gap junction protein that is preferentially expressed by SGCs in the TG. Currently, little is known about the effects of low-grade inflammation on Cx43 expression in the TG in animal models of TMD. The purpose of this study was to investigate whether Cx43 expression increased in inflammatory TMD models, and subsequently, whether Cx43 expression was greater under high estrogen conditions. To test this, male and female rats were given intra-TMJ a single injection of Complete Freund’s Adjuvant (CFA) to model TMJ inflammation. TG tissue was harvested at four or ten days post-CFA injection, and immunohistochemistry (IHC) was performed to quantify Cx43 expression. In subsequent experiments, Cx43 was knocked down through intra-TG injection of siRNA and TMJ-evoked electromyography was performed to assess jaw muscle activity. The preliminary data indicate that knockdown of Cx43 reduced muscle activity. These results suggest a relationship between Cx43 expression, estrogen status, and inflammatory TMJ pain. Consequently, drugs targeting Cx43 may provide therapeutic benefit for TMD patients.