A monosynaptic pathway links the vestibular nuclei and masseter muscle motoneurons in rats
A monosynaptic pathway links the vestibular nuclei and masseter muscle motoneurons in rats
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DOI：
10.1007/s00221-006-0834-7
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发表时间：
2007-02-01
影响因子：
2
通讯作者：
Billig, I.
中科院分区：
文献类型：
--
作者：
Cuccurazzu, B.;Deriu, F.;Billig, I.
生理学证据表明，前庭信号调节支配咬肌的运动神经元的活动。最近，使用伪狂犬病病毒的跨突触逆行运输的实验提供了解剖学证据，许多神经元集中在前庭内侧核（MVePC）和尾侧前置舌下肌（PH）的小细胞部的背内侧部分提供输入到运动神经元支配咬肌浅层的下三分之一。然而，目前尚不清楚这种前庭三叉神经投射是单突触还是多突触。本研究旨在确定是否在MVePC或PH项目的神经元直接控制大鼠咬肌的运动神经元。为此，将顺行示踪剂（生物素化葡聚糖胺，BDA）注射到前庭核（主要是MVePC）或PH中，并将逆行示踪剂（霍乱毒素的β-亚基，b-CT）注射到BDA注射部位的同侧或对侧咬肌中。BDA注射到前庭核或PH后，顺行标记的轴突终末观察到双侧三叉神经运动核（Mo 5），特别是在腹侧，内侧和外侧部分的核;预测背Mo 5稀疏。此外，逆行标记的运动神经元位于同侧Mo 5的腹侧和外侧部分。此外，顺行标记的终端被观察到是在靠近运动神经元的Mo 5逆行标记从b-CT注射到咬肌。本研究为MVePC和PH与咬肌运动神经元之间存在单突触通路提供了直接证据。
Physiological evidence indicates that vestibular signals modulate the activity of motoneurons innervating the masseter muscle. Recently, experiments using transynaptic retrograde transport of pseudorabies virus provided anatomical evidence that many neurons concentrated in the dorsomedial part of the parvicellular division of the medial vestibular nucleus (MVePC) and the caudal prepositus hypoglossi (PH) provide inputs to motoneurons innervating the lower third of the superficial layer of the masseter muscle. However, it was not clear whether this vestibulo-trigeminal projection was monosynaptic or polysynaptic. The present study sought to determine whether neurons in the MVePC or PH project directly to motoneurons controlling the masseter muscle in rats. For this purpose, an anterograde tracer (biotinylated dextran amine, BDA) was injected into vestibular nuclei (mainly MVePC) or PH and a retrograde tracer (the beta-subunit of cholera toxin, b-CT) was injected into the masseter muscle ipsilateral or contralateral to the BDA injection site. Following injections of BDA into the vestibular nuclei or PH, anterogradely labeled axon terminals were observed bilaterally in the motor trigeminal nucleus (Mo5), particularly in the ventral, medial, and lateral portions of the nucleus; projections to dorsal Mo5 were sparse. In addition, retrogradely labeled motoneurons were located in the ventral and lateral portions of the ipsilateral Mo5. Moreover, anterogradely labeled terminals were observed to be in close proximity to motoneurons in the Mo5 that were retrogradely labeled from b-CT injections into the masseter muscle. This study provides direct evidence that a monosynaptic pathway exists between the MVePC and PH and masseter motoneurons.