Purdue University, Dept. of Psychological Sciences, West Lafayette, IN 47907-2081, United States.
Auton Neurosci. 2013 Dec;179(1-2):90-8. doi: 10.1016/j.autneu.2013.08.069. Epub 2013 Aug 30.
Little is known about the architecture of the vagal motor units that control esophageal striated muscle, in spite of the fact that these units are necessary, and responsible, for peristalsis. The present experiment was designed to characterize the motor neuron projection fields and terminal arbors forming esophageal motor units. Nucleus ambiguus compact formation neurons of the rat were labeled by bilateral intracranial injections of the anterograde tracer dextran biotin. After tracer transport, thoracic and abdominal esophagi were removed and prepared as whole mounts of muscle wall without mucosa or submucosa. Labeled terminal arbors of individual vagal motor neurons (n=78) in the esophageal wall were inventoried, digitized and analyzed morphometrically. The size of individual vagal motor units innervating striated muscle, throughout thoracic and abdominal esophagus, averaged 52 endplates per motor neuron, a value indicative of fine motor control. A majority (77%) of the motor terminal arbors also issued one or more collateral branches that contacted neurons, including nitric oxide synthase-positive neurons, of local myenteric ganglia. Individual motor neuron terminal arbors co-innervated, or supplied endplates in tandem to, both longitudinal and circular muscle fibers in roughly similar proportions (i.e., two endplates to longitudinal for every three endplates to circular fibers). Both the observation that vagal motor unit collaterals project to myenteric ganglia and the fact that individual motor units co-innervate longitudinal and circular muscle layers are consistent with the hypothesis that elements contributing to peristaltic programming inhere, or are "hardwired," in the peripheral architecture of esophageal motor units.
尽管这些单位对于蠕动是必需的并且负责，但对于控制食管横纹肌的迷走运动单位的结构知之甚少。本实验旨在描述形成食管运动单位的运动神经元投射场和终末树突。通过双侧颅内注射顺行示踪剂葡聚糖生物素，标记大鼠的疑核致密形成神经元。在示踪剂转运后，取出胸腹部食管并制备无黏膜或黏膜下层的肌肉壁全层。对食管壁中单个迷走运动神经元（n=78）的标记终末树突进行了清点、数字化和形态计量学分析。在胸腹部食管中，支配横纹肌的单个迷走运动单位的大小平均为每个运动神经元 52 个终板，这表明了精细的运动控制。大多数（77%）运动终末树突还发出一个或多个侧支，与局部肌间神经节的神经元接触，包括一氧化氮合酶阳性神经元。单个运动神经元终末树突以大致相似的比例共同支配（即，两个终板到纵肌，三个终板到环肌纤维）或串联供应纵肌和环肌纤维的终板。迷走运动单位侧支投射到肌间神经节的观察结果以及单个运动单位共同支配纵肌和环肌层的事实都与这样的假设一致，即有助于蠕动编程的因素存在于食管运动单位的外周结构中，或者是“硬连线”的。
