Morimoto T, Inoue T, Masuda Y, Nagashima T
Department of Oral Physiology, Osaka University, Faculty of Dentistry, Japan.
Exp Brain Res. 1989;76(2):424-40. doi: 10.1007/BF00247900.
The role of oral and facial sensory receptors in the control of masticatory muscle activities was assessed from the effect of acute deafferentiation on cortically induced rhythmic jaw movements (CRJMs) in anesthetized rabbits. When a thin polyurethane-foam strip (1.5, 2.5 or 3.5 mm thick) was placed between opposing molars during CRJMs, masseteric activities were facilitated in association with an increase in the medial excursion of the mandible during the power phase. The effects varied with the pattern of CRJMs, and the rate of facilitation was greater for small circular movements than for the crescent-shaped movements. Furthermore, the response of the masseter muscle was greater in the anterior half of the muscle, where muscle spindles are most dense, than in its posterior half. It was also demonstrated that the response increased with an increase in the thickness of the test strip. In contrast, the activities of the jaw-opening muscle were not affected significantly. The duration of masseteric bursts increased during application of the test strip and the chewing rhythm tended to slow down. However, the latter effect was not significant. After locally anesthetizing the maxillary and inferior alveolar nerves, the facilitative responses of the masseter muscle to the test strip was greatly reduced but not completely abolished. Lesioning of the mesencephalic trigeminal nucleus (Mes V) where the primary ganglion cells of muscle spindle afferents from jaw-closing muscles and some periodontal afferents are located, also reduced the facilitative effects. Similar results were obtained in the animals with the kainic acid injections into the Mes V 1 week before electrical lesioning of this nucleus. In these animals the effects of electrical lesioning of the Mes V could be attributed to the loss of muscle receptor afferents since the neurons in the vicinity of the Mes V were destroyed and replaced by glial cells, whereas the Mes V neurons are resistant to kainic acid. When electrical lesioning of the Mes V and sectioning of the maxillary and inferior alveolar nerves were combined in animals with a kainic acid injection into the Mes V, the response of the masseter muscle to application of the strip was almost completely abolished. From these findings, we conclude that both periodontal receptors and muscle spindles are primarily responsible for the facilitation of jaw-closing muscle activities.(ABSTRACT TRUNCATED AT 400 WORDS)
通过急性去传入神经对麻醉兔皮质诱导的节律性下颌运动（CRJMs）的影响，评估口腔和面部感觉受体在咀嚼肌活动控制中的作用。当在CRJMs期间在相对的磨牙之间放置一条薄的聚氨酯泡沫条（1.5、2.5或3.5毫米厚）时，咬肌活动增强，同时在动力期下颌的内侧偏移增加。这些效应因CRJMs的模式而异，对于小圆形运动，促进率大于新月形运动。此外，咬肌在前半部分（肌梭最密集的部位）的反应比后半部分更大。还表明，反应随着测试条厚度的增加而增加。相比之下，开颌肌的活动没有受到显著影响。在应用测试条期间，咬肌爆发的持续时间增加，咀嚼节奏趋于减慢。然而，后一种效应并不显著。在上颌神经和下牙槽神经局部麻醉后，咬肌对测试条的促进反应大大降低，但并未完全消除。损伤中脑三叉神经核（Mes V）（来自闭口肌的肌梭传入纤维和一些牙周传入纤维的初级神经节细胞所在的部位）也降低了促进作用。在用电损伤该核1周前向Mes V注射 kainic 酸的动物中也获得了类似的结果。在这些动物中，Mes V电损伤的效应可归因于肌肉受体传入纤维的丧失，因为Mes V附近的神经元被破坏并被胶质细胞取代，而Mes V神经元对kainic 酸具有抗性。当在向Mes V注射kainic 酸的动物中将Mes V的电损伤与上颌神经和下牙槽神经的切断相结合时，咬肌对测试条应用的反应几乎完全消失。从这些发现中，我们得出结论，牙周受体和肌梭主要负责促进闭口肌活动。（摘要截断于400字）
