Mechanism of motor coordination of masseter and temporalis muscles for increased masticatory efficiency in mice
Mechanism of motor coordination of masseter and temporalis muscles for increased masticatory efficiency in mice
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DOI：
10.1111/joor.12491
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发表时间：
2017-05-01
影响因子：
2.9
通讯作者：
Yoshida, N.
中科院分区：
文献类型：
--
作者：
Yoshimi, T.;Koga, Y.;Yoshida, N.
近年来，随着越来越多的表达口颌系统功能障碍的转基因小鼠的出现，使用小鼠作为阐明口腔运动障碍的病理生理学和发病机制的动物模型的需求一直在增加。然而，在咀嚼过程中，小鼠下颌运动的基本特征尚未完全阐明。本研究的目的是探讨咬肌和颞肌的作用，以及这些肌肉的运动协调机制，以提高咀嚼效率在关闭相的小鼠。22只雄性Jcl：ICR小鼠分为正常对照组（n=8）、咬肌功能减退组（n=7）和颞肌功能减退组（n=7）。A型肉毒神经毒素（BoNT/A）用于诱导肌肉功能减退。将BoNT/A注入咬肌后，咬合期水平方向的咀嚼运动路径变得不稳定。将BoNT/A注射到颞肌中减少了与咀嚼周期的动力相对应的晚期闭合相的前后偏移。这些结果表明，咬肌起着重要的作用，在稳定的研磨路径，其中的食物团是通过滑动后牙在咬合阶段从后向前研磨。颞肌在闭合早期起着主要作用，使下颌骨更向后收缩，延长磨削路径。咀嚼效率基于咬肌和颞肌活动的协调而提高。
The demand for the use of mice as animal models for elucidating the pathophysiologies and pathogeneses of oral motor disorders has been increasing in recent years, as more and more kinds of genetically modified mice that express functional disorders of the stomatognathic system become available. However, the fundamental characteristics of mouse jaw movements during mastication have yet to be fully elucidated. The purpose of this study was to investigate the roles of the masseter and temporalis muscles, and the mechanisms of motor coordination of these muscles for increasing masticatory efficiency in the closing phase in mice. Twenty-two male Jcl:ICR mice were divided into control (n=8), masseter-hypofunction (n=7) and temporalis-hypofunction groups (n=7). Botulinum neurotoxin type A (BoNT/A) was used to induce muscle hypofunction. The masticatory movement path in the horizontal direction during the occlusal phase became unstable after BoNT/A injection into the masseter muscle. BoNT/A injection into the temporalis muscle decreased antero-posterior excursion of the late-closing phase corresponding to the power phase of the chewing cycle. These results suggest that the masseter plays an important role in stabilizing the grinding path, where the food bolus is ground by sliding the posterior teeth from back to front during the occlusal phase. The temporalis plays a major role in retracting the mandible more posteriorly in the early phase of closing, extending the grinding path. Masticatory efficiency is thus increased based on the coordination of activities by the masseter and temporalis muscles.