1993 Volume 5 Issue 1 Pages 22-29
There have been few reports concerning sensory and sympathetic innervation of the temporomandibular joint (TMJ). We investigated it by using horseradish peroxidase (HRP).
Experiments were performed using 20 Wister rats. The animals were divided into four experimental groups; 40% HRP (1-3μl) was injected into the TMJ capsule of one side (group 1). HRP was injected into the TMJ capsule of one side and the tooth pulp of upper first molar of the contralateral side (group 2). After sectioning the external carotid artery and the sympathetic plexus, HRP was injected into the ipsilateral TMJ capsule (group 3). After sectioning the auriculotemporal nerve, HRP was injected into the ipsilateral TMJ capsule (group 4). After a 24-hour survival period, the animals were perfused with fixative and the superior cervical (SCG), stellate (SG) and trigeminal (TRG) ganglia were dissected, sectioned and processed with tetraethyl benzidine method.
Labeled cells were recognized in the ipsilateral SCG and TRG. In SCG they were distributed uniformly. In TRG they were found in the submandibular division (group 1).
The mean diameter of labeled cells in SCG was 19.2±2.1μm. In TRG the mean diameter of labeled cells of TMJ (23.3±5.4μm) was significantly smaller than that of the tooth pulp (27.8±5.5μm) (group 2). Almost no labeling was obtained in SCG after sectioning of the sympathetic plexus (group 3). No labeling of TMJ was recognized in SCG and the number of labeled cells of TMJ (2.6±1.5) was reduced by 1/10 in group 2 by sectioning the auriculotemporal nerve (group 4).
The sympathetic components which originate from SCG are supposed to innervate TMJ through intervention of the nerve after ascending along the external carotic plexus. In the rat about 90% of the sensory fibers innervating TMJ are considered to be carried by the auricurotemporal nerve, which seem to contain more frequent ratio of smaller Aδ and C fibers that those for tooth pulp.
