Investigation of Temporomandibular Joint Innervation in Cats using Horseradish Peroxidase Anterograde Transport

Abstract

Distribution of the trigeminal sensory nerve fibers of the cat temporomandibular joint (TMJ) was studied using horseradish peroxidase (HRP) anterograde transport. Ten adult male cats weighing 3-4kg were anesthetized and paralyzed, and 10μl of 30% HRP (Type VI) in saline was injected manually into the right exposed trigeminal ganglion using a microsyringe. The cats were sacrificed after 48 hours. The dissected right TMJ capsule and disk were frozen and sectioned serially in either the sagittal or frontal planes at 20μm, and stained with tetramethyl benzidine. The same method was carried out on the left TMJ capsules and disks as controls. The results obtained were as follows :
1) Most of HRP-labeled nerve fibers had undulating courses. All nerve fibers terminated as free nerve endings.
2) No HRP-labeled nerve fibers were observed in the middle of the disk except in one cat.
3) Some of the HRP-labeled nerve fibers observed in subsynovial connective tissue were distributed in the synovial membrane.
4) HRP-labeled nerve fibers were observed in the adventitia of the artery of the TMJ.
5) Most of the HRP-labeled nerve fibers were observed at the boundary area of disk and capsule, and their numbers decreased gradually as the distance from the boundary area increased.
6) More HRP-labeled nerve fibers were observed in the posterior and lateral regions of the TMJ than in the anterior and medial regions.
In this way we were able to determine the trigeminal sensory innervation of the cat TMJ.