Distribution of PGP 9.5- and nNOS-containing nerve fibers in the temporomandibular joint disk attachments of the elderly human.

Innervation of the human temporomandibular joint (TMJ) disk and its surrounding structures posterior vascular plexus portion was investigated by immunohistochemistry for protein gene product 9.5 (PGP 9.5) and neuronal nitric oxide synthase (nNOS). The TMJ disk was free of PGP 9.5- and nNOS-immunoreactive (-ir) nerve fibers. In the TMJ disk attachments and posterior vascular plexus portion, however, PGP 9.5- and nNOS-immunoreactivity was detected. PGP 9.5-ir nerve fibers within nerve bundles were common in these regions. Perivascular PGP 9.5-ir nerve fibers were common in the attachments and posterior vascular plexus portion but not in the posterior attachment inferior. Isolated PGP 9.5-ir nerve fibers were also scattered throughout the TMJ attachments but not in the posterior vascular plexus portion. There was no significant difference about the density of PGP 9.5-ir nerve fibers among all of the attachments and posterior vascular plexus portion. NOS-ir nerve fibers within nerve bundles were common in the anterior and posterior attachments inferior, and the posterior vascular plexus portion. Perivascular nNOS-ir nerve fibers in the anterior attachment inferior were more abundant than in other regions. Isolated nNOS-ir nerve fibers were common in the anterior attachment inferior but not in other regions. Fine isolated nerve fibers with varicose appearance occasionally had small swellings in their terminals. Thick isolated nerve fibers rarely showed unencapsulated corpuscular endings with multiple large and spindle-shaped swellings. The density of nNOS-ir nerve fibers in the anterior attachment inferior was significantly higher than in the posterior attachment superior. In addition, the double immunofluorescence method demonstrated that vascular and isolated nNOS-ir nerve fibers were also immunoreactive for PGP 9.5 in the anterior attachment inferior. The present study suggests that nNOS-ir nerve fibers with a parasympathetic nature can control blood flow mainly in the anterior attachment inferior and slightly in other attachments and the posterior vascular plexus portion. nNOS-ir nerve fibers with a sensory nature may be associated with nociceptive transmission in the TMJ disk attachments.