Neural control of hyperactivity and spasm in the masticatory muscles.

提示咀嚼肌活动亢进或痉挛是导致颞下颌关节紊乱的主要原因。然而，多动的神经机制还没有被清楚地发现。为了研究这一机制，我们做了以下六个实验。(1)食物硬度对咀嚼力控制的影响。(2)肌梭传入在咀嚼动力控制中的作用。(3)清醒动物咀嚼时颌骨肌梭放电的调制(4)颌骨肌梭传入的分类(5)生物胺对三叉神经运动神经元膜特性的影响(6)味觉排斥行为与吞咽行为的关系。结果如下：(1)在麻醉兔皮质诱发的节律性颌骨运动(CRJM)中，咀嚼较硬的试条可引起闭合肌电活动增加。(2)观察咀嚼力值与咀嚼肌梭传入放电频率的相关性。(3)不同咀嚼阶段之间放电模式的差异可能归因于梭形运动活动和颌骨运动模式的阶段性调节。(4)我们发现，颌骨肌梭传入可以根据斜行-保持牵拉反应的放电模式分为两组。(5)细胞内钙离子浓度可调节生物胺对三叉神经运动神经元后除极的影响。(6)臂旁核可能在拒绝味觉引起的流涎中起重要作用。

It is suggested that hyperactivity or spasm in the masticatory muscles cause the temporomandibular joint disorders. However the neural mechanism of the hyperactivity has not bee found clealy. To investigate this mechanism we have done following six experiments. (1) effect of the hardness of food on the control of masticatory force. (2) role of the muscle spindle afferents on the control of masticatory force. (3) modulation of jaw muscle spindle discharge during mastication in the awake animals (4) classification of the jaw muscle spindle afferents (5) influence of the biogenic amine on the membrane charactaristics of the trigeminal motoneurons (6) relationship between the taste rejection behavior and salivation.Results were as follows :(1) During cortically induced rhythmic jaw movements (CRJMs) in anesthetized rabbits, chewing of the harder test strips induced the larger EMG activities of the jaw closing muscle. (2) We observed the correlation between the magnitude of the masticatory force and the firing frequency of the spindle afferent of masticatory muscle. (3) The difference in the firing pattern among masticatory stages may be ascribed to a stage-dependent modulation of both fusimotor activity and jaw movement pattern. (4) We found the possibility that the jaw muscle spindle afferents may be calssified into two groups on the basis of the firing pattern in the response to the ramp-and-hold stretch. (5) Intracellular calcium concentration may modulate the effect of the biogenic amine on the afterdepolarization in the trigeminal motoneurons. (6) The parabrachial nucleus may play an important role on salivation induced by the rejectable taste.