SUBSTANCE P-ASSOCIATED INCREASE OF INTRAARTICULAR TEMPERATURE AND PAIN THRESHOLD IN THE ARTHRITIC TMJ

Neuropeptides are considered mediators and modulators of inflammatory joint disease. Substance P (SP) has been proposed as a mediator of pai n, and Its vasoactive properties are well documented. In this study, t he presence of SP-like immunoreactivity in the synovial fluid was corr elated to intra-articular temperature (IAT) and pain from the arthriti c temporomandibular joint (TMJ) 3 to 5 weeks after one intra-articular injection of glucocorticosteroids. Eighteen TMJs were investigated fo r IAT and the presence of SP-like immunoreactivity in the synovial flu id in 12 patients with systemic inflammatory joint disease. After arth rocentesis, the aspirates were analyzed for SP-like immunoreactivity b y means of competitive radio immunoassay. A visual analogue scale and an algometer determining the pressure pain threshold and tolerance lev el assessed arthritic pain and hyperalgesia in the TMJ. Our results in dicate that SP-like immunoreactivity is associated with IAT and that i ncreased concentrations of joint fluid SP-like immunoreactivity corres pond to increased pain threshold and tolerance and a concomitantly: de creased visual analogue scale. These findings suggest that SP is impli cated in the vascular and nonciceptive response of the arthritic joint anti that SP, possibly assisted by the antinociceptive effect of loca l corticosteroids, has a modulatory role in arthritic pain and hyperal gesia.