Neural control of hyperactivity and spasm in the masticatory muscles.

提示咀嚼肌的过度活动或痉挛是引起颞下颌关节紊乱的原因。然而，多动症的神经机制尚不清楚。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)肌纺锤体传入神经在咀嚼力控制中的作用。(3)清醒动物咀嚼时颌肌纺锤体放电的调节(4)颌肌纺锤体传入神经的分类(5)生物胺对三叉神经运动神经元膜特性的影响(6)味觉排斥行为与唾液分泌的关系。结果表明：(1)在麻醉兔皮质诱导的节律性下颚运动（CRJMs）中，咀嚼较硬的试纸条诱导的下颚闭合肌肌电图活动较大。(2)我们观察了咀嚼力的大小与咀嚼肌纺锤体传入神经的发射频率之间的相关性。(3)咀嚼各阶段放电模式的差异可能归因于融合运动和下颌运动模式的阶段依赖性调节。(4)我们发现颚肌纺锤体传入事件可以根据对倾斜和保持拉伸的反应的放电模式分为两组。(5)细胞内钙浓度可能调节生物胺对三叉神经运动神经元后去极化的影响。(6)臂旁核可能在排斥味诱导的唾液分泌中起重要作用。

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.