Innervation of Rat Temporomandibular Joint

An Immunohistochemical Study Using Protein Gene Product 9.5 Antibody

Abstract

Innervation and terminal formation were investigated in rat temporomandibular joint by immunohistochemistry for protein gene product 9.5 (PGP 9.5) both at light and electron microscopic levels. The results were summarized as follows:
1. Nerve fibers distributed in the rat temporomandibular joint entered the capsule anteriorly and posteriorly, and some branches further extended towards medial and lateral aspects of the articular disk. No differences were observed in nerve density between the anterior and posterior parts of the diskassociated connective tissue.
2. PGP 9.5-positive nerve fibers were not observed in the center of the articular disk, with only thin nerves scattered in the marginal portion of the articular disk.
3. Synovial membrane contained a number of thin nerve fibers which were located exclusively at the subsynovial layer. No nerve fibers penetrated deeply into the thick synovial cell layer toward the articular cavity.
4. Major population of nerve terminals in the rat temporomandibular joint was recognized as free nerve endings by light microscopic immunohistochemistry. At the electron microscopic level, however, those light microscopic free nerve endings were divided into two subtypes in the category of nociceptors and mechanoreceptors. The former type was much more prevalent than the latter.
5. As regards the specialized nerve endings, this immunostaining could demonstrate the Ruffini-like endings in the lateral pericondylar tissue near the center of the condyle. In addition, coiled-and Meissner's-like nerve terminals were also observed in the connective tissue surrounding the articular disk.