Capsaicin receptor expression in the rat temporomandibular joint

Abstract

Experimentally, temporomandibular joint (TMJ) nerve units respond to capsaicin, which is used clinically to treat TMJ pain. However, the existence of capsaicin receptors in the TMJ has not previously been clearly demonstrated. Immunohistochemical analysis has revealed the presence of transient receptor potential vanilloid subtype 1 (TRPV1) expression in the nerves and synovial lining cells of the TMJ. TRPV1-immunoreactive nerves are distributed in the synovial membrane of the joint capsule and provide branches to the joint compartment. The disc periphery is supplied by TRPV1 nerves that are mostly associated with small arterioles, and occasional nerves penetrate to the synovial lining layer. Double immunofluorescence has shown that many TRPV1-immunoreactive nerves are labeled with neuropeptide calcitonin gene-related peptide, whereas few are labeled with IB4-lectin. The results provide evidence for the presence of TRPV1 in both nerves and synovial lining cells, which might thus be involved in the mechanism of nociception and inflammation in the TMJ.

Synovial TRPV1 is upregulated by 17-β-estradiol and involved in allodynia of inflamed temporomandibular joints in female rats

“…16 TRPV1 is not only expressed in the nerves and vessels distributed in the synovium, but also in the synovial lining cells in both rat and human TMJs. 17,18 However, its biological role in the TMJ remains unexplored. In this article, we explored whether estradiol can induce TRPV1 expression in the TMJ synovium and whether synovial TRPV1 is involved in the allodynia of the inflamed TMJ.…”

GABAergic influence on temporomandibular joint-responsive spinomedullary neurons depends on estrogen status

“…The TMJ region is supplied by small diameter sensory fibers (Kido et al, 1995; Takeuchi and Toda, 2003; Ioi et al, 2006) that project to the superficial laminae at the Vc/C 1–2 region (Shigenaga et al, 1986; 1988). The superficial laminae at the Vc/C 1–2 region share many properties with corresponding regions at lower segments of the spinal cord (Bereiter et al, 2000) and receive the majority of input from unmyelinated sensory fibers (Kobayashi and Matsumura, 1996; Sugimoto et al, 1997).…”

Chronic inflammation and estradiol interact through MAPK activation to affect TMJ nociceptive processing by trigeminal caudalis neurons

“…The TMJ region is supplied by small diameter sensory fibers (Kido et al, 1995; Takeuchi and Toda, 2003; Ioi et al, 2006) that project mainly to the superficial laminae at the Vc/C 1–2 region (Shigenaga et al, 1986; 1988). The superficial laminae receive the vast majority of unmyelinated C-fiber input from peripheral nociceptors (Light, 1992) and express a high density of estrogen receptors (Bereiter et al, 2005a).…”