Distribution of substance P-like immunoreactive nerve fibers in temporomandibular joint soft tissues of monkey.

The distribution of substance P-immunoreactive and silver impregnated nerve fibers in the temporomandibular joint soft tissues of the Macaca fascicularis monkey was investigated in frozen sections. The pattern of substance P-immunoreactive structures in the soft tissues and periosteum of the temporomandibular joint was compared with the distribution of silver impregnated nerve fibers within these tissues. Presence of substance P-immunoreactive fibers was demonstrated in the temporomandibular joint capsule, disc attachments, fascia, adjacent periosteum and within the interfascicular connective tissue of the lateral pterygoid muscle. The overall distribution corresponded to that of silver impregnated nerve fibers. Substance P-immunoreactive nerve fibers were found in the adventitia of arteries in all vascularized temporomandibular joint soft tissues but could not be found in the adventitia of veins. No substance P-immunoreactive or silver impregnated nerve fibers were seen in the dense collagenous tissue forming the disc. Substance P is suggested to influence the major features of inflammation and to play a role in acute and chronic pain conditions.