Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5880, USA.
Brain Res. 2012 Dec 13;1489:37-47. doi: 10.1016/j.brainres.2012.10.021. Epub 2012 Oct 17.
Jaw muscle spindle afferents (JMSA) in the mesencephalic trigeminal nucleus (Vme) project to the parvocellular reticular nucleus (PCRt) and dorsomedial spinal trigeminal nucleus (dm-Vsp). A number of premotor neurons that project to the trigeminal motor nucleus (Vmo), facial nucleus (VII) and hypoglossal nucleus (XII) are also located in the PCRt and dm-Vsp. In this study, we examined whether these premotor neurons serve as common relay pool for relaying JMSA to multiple orofacial motoneurons. JMSA inputs to the PCRt and dm-Vsp neurons were verified by recording extracellular responses to electrical stimulation of the caudal Vme or masseter nerve, mechanical stimulation of jaw muscles and jaw opening. After recording, biocytin in recording electrode was inotophorized into recording sites. Biocytin-Iabeled fibers traveled to the Vmo, VII, XII, and the nucleus ambiguus (Amb). Labeled boutons were seen in close apposition with Nissl-stained motoneurons in the Vmo, VII, XII and Amb. In addition, an anterograde tracer (biotinylated dextran amine) was iontophorized into the caudal Vme, and a retrograde tracer (Cholera toxin B subunit) was delivered into either the VII or Xll to identify VII and XII premotor neurons that receive JMSA input. Contacts between labeled Vme neuronal boutons and premotor neurons were observed in the PCRt and adjacent dm-Vsp. Confocal microscopic observations confirmed close contacts between Vme boutons and VII and XII premotor neurons. This study provides evidence that JMSA may coordinate activities of multiple orofacial motor nuclei, including Vmo, VII, XII and Amb in the brainstem via a common premotor neuron pool.
咀嚼肌肌梭传入纤维（JMSA）在中脑三叉神经核（Vme）投射到小细胞网状核（PCRt）和背内侧三叉神经脊髓核（dm-Vsp）。一些投射到三叉神经运动核（Vmo）、面神经核（VII）和舌下神经核（XII）的运动前神经元也位于 PCRt 和 dm-Vsp 中。在这项研究中，我们研究了这些运动前神经元是否作为将 JMSA 中继到多个口面运动神经元的共同中继池。通过记录对尾部 Vme 或咬肌神经的电刺激、咀嚼肌和张口的机械刺激的记录部位的细胞外反应，验证了 JMSA 对 PCRt 和 dm-Vsp 神经元的输入。在记录后，将记录电极中的生物胞素标记到记录部位。生物胞素标记的纤维行进到 Vmo、VII、XII 和疑核（Amb）。在 Vmo、VII、XII 和 Amb 中，标记的终末与尼氏染色的运动神经元紧密相邻。此外，将顺行示踪剂（生物素化葡聚糖胺）离子导入尾部 Vme，将逆行示踪剂（霍乱毒素 B 亚单位）递送至 VII 或 XII 以识别接收 JMSA 输入的 VII 和 XII 运动前神经元。在 PCRt 和相邻的 dm-Vsp 中观察到标记的 Vme 神经元末梢与运动前神经元之间的接触。共聚焦显微镜观察证实了 Vme 末梢与 VII 和 XII 运动前神经元之间的紧密接触。这项研究提供了证据表明，JMSA 可能通过共同的运动前神经元池协调多个口面运动核，包括脑干中的 Vmo、VII、XII 和 Amb 的活动。
