顎関節刺激による二種の開口反射応答に関する研究

Abstract

Two different jaw opening responses elicited by a single stimulation of the temporomandibular joint (TMJ) were recorded from the myohyoid nerve in a-chloralose-anesthetized cats. One featured an early response (ER, 5-8 msec latency) and the other a late response (LR, 18-20 msec latency). The LR which was suppressed slowly by application of 2% Xylocaine to the TMJ was elicited by a lower stimulus intensity than that of ER. Mechanical stimulation of the TMJ was more effective for producing an LR than an ER. These results indicate that an LR originates from mechanoreceptors of TMJ having thick afferent fibers, and that an ER originates from nociceptors with thin afferent fibers. The LR amplitude produced by a test stimulus to the TMJ was suppressed by the conditioning stimulus to the TMJ. Similar results were obtained when the same test was applied to the periodontal ligament. When a conditioning stimulus was applied to the TMJ while a test stimulus was applied to the periodontal ligament and then reversed, the inhibitory effects elicited from both regions were smaller than when the conditioning and test stimulation were applied to a single site, The LR elicited by the movement of the jaw changed with the change in the position of condyle and the velocity of the movement. These results indicate that mechanoreceptors in the TMJ were specialized in their distribution, and the density of mechanoreceptors in comparison with that of nociceptors in the TMJ is greater than that in the periodontal ligament and oral mucosa.