Local anesthesia does not block mustard-oil-induced temporomandibular inflammation

Temporomandibular joint (TMJ) disorders and rheumatoid arthritis are two co nditions in which neurogenic mechanisms may play a critical role. We invest igated the neurogenic contribution underlying acute TMJ inflammation by eva luating effects of local anesthetic blockade of afferent innervation on the development of mustard oil (MO)-induced edema in the rat TMJ area. Groups of eight adult male Sprague-Dawley rats were anesthetized by intraperitonea l ol-chloralose and urethane. A saline injection into the right TMJ followe d by MO (1% to 60%) 6 min later elicited dose-dependent edema development ( P < 0.05, repeated measures analysis of variance). Lidocaine (5%) or bupiva caine (0.5%) followed by MO (1% or 40%) did not produce edema development d ifferent from saline controls (P > 0.05, repeated measures analysis of vari ance). The failure of local anesthetic blockade to prevent MO-induced edema is not consistent with MO acting through a neurogenic mechanism, as tradit ionally perceived.