Neuromuscular control of the mammalian tongue

描述（由申请人提供）：舌肌参与多种活动，如呼吸、吞咽、言语和咀嚼，因此对体内平衡至关重要。来自8块不同肌肉的纤维插入哺乳动物的舌头，控制舌头的运动、形状和硬度，但舌头肌肉运动单元的控制在很大程度上被忽视了。我们的目标是通过解决以下问题，探索中枢神经系统如何控制一种模式行为（由呼吸中枢模式发生器（CPG）控制的驱动），这种行为涉及多个肌肉作用于单个机械结构：1)驱动舌前伸肌和舌后伸肌的运动神经元接受重要的共同突触输入，尽管它们对舌有相反的机械作用，这表明激动剂-拮抗剂共同激活控制舌僵硬；2)舌头和“初级”吸气肌（横膈肌、肋间肌）的呼吸相关输入来自独立的来源；模型预测，随着突触输入细胞的增加，运动单元尖峰序列变得更加可变。当兴奋性突触输入叠加在来自呼吸CPG的基础输入上时，可以通过测量尖峰序列变异性的变化来测试这一点；4)支配舌肌呼吸相关活动的运动单元分为2个功能群；当驱动到肌肉时，那些编码率增加，而那些没有。我们认为，尽管突触输入增加，但不编码的运动单元的放电率达到饱和；我们会检验这个假设；5)肌肉内的单个运动单元至少包括4个任务特异性亚群（吸气、呼气、强直和呼气-吸气单元），并且给定单元的任务特异性取决于其收缩特性。实验将在麻醉、自主呼吸的成年大鼠身上进行。所使用的技术包括单运动单元电生理学、相互关系分析和通气量测量。这些实验的结果将为开发阻塞性睡眠呼吸暂停、吞咽障碍和口面部运动缺陷的治疗策略提供所需的知识基础。

DESCRIPTION (provided by applicant): The tongue muscles participate in such diverse activities as breathing, swallowing, speech and mastication, and are thus critical for homeostasis. Fibers from 8 different muscles insert into the mammalian tongue and control its movement, shape and stiffness, but the control of tongue muscle motor units has been largely ignored. Our goal is to explore how the central nervous system controls a patterned behavior (drive controlled by the respiratory central pattern generator, CPG) that involves multiple muscles acting on a single mechanical structure, by addressing the following issues: 1) motoneurons driving tongue protrudor and retractor muscles receive significant common synaptic input even though they have opposite mechanical actions on the tongue, suggesting that agonist-antagonist co-activation controls tongue stiffness; 2) respiratory-related input to tongue and "primary" inspiratory muscles (diaphragm, intercostals) is derived from independent sources; 3) Models predict that motor unit spike trains become more variable as synaptic input to the cell is increased. This can be tested by measuring the change in spike train variability when excitatory synaptic input is superimposed on the underlying input emanating from the respiratory CPG; 4) Motor units innervating tongue muscles with respiratory related activity fall into 2 functional populations; those that rate code when drive to the muscle increases, and those that do not. We propose that the firing rate of motor units that do not rate code saturates despite increases in synaptic input; and we will test this hypothesis; 5) Individual motor units within a muscle comprise at least 4, task-specific sub-populations (inspiratory, expiratory, tonic and expiratory-inspiratory units), and the task specificity of a given unit depends on its contractile properties. Experiments will be done in anesthetized, spontaneously breathing adult rats. Techniques used include single motor unit electrophysiology, cross correlation analysis and the measurement of ventilatory output. The results of these experiments will contribute to the knowledge base needed to develop treatment strategies for obstructive sleep apnea, swallowing disorders, and oro-facial motor deficits.