Giaconi E, Deriu F, Tolu E, Cuccurazzu B, Yates B J, Billig I
Department of Otolaryngology, Eye and Ear Institute, University of Pittsburgh, Room 519, Pittsburgh, PA 15213, USA.
Exp Brain Res. 2006 May;171(3):330-9. doi: 10.1007/s00221-005-0275-8. Epub 2005 Nov 24.
Previous studies reported that the activity of trigeminal motoneurons innervating masseter muscles is modulated by vestibular inputs. We performed the present study to provide an anatomical substrate for these physiological observations. The transynaptic retrograde tracer pseudorabies virus-Bartha was injected into multiple sites of the lower third of the superficial layer of the masseter muscle in rats, a subset of which underwent a sympathectomy prior to virus injections, and the animals were euthanized 24-120 h later. Labeled masseteric motoneurons were first found in the ipsilateral trigeminal motor nucleus following a 24-h postinoculation period; subsequent to 72-h survival times, the number of infected motoneurons increased, and at > or =96 h many of these cells showed signs of cytopathic changes. Following 72-h survival times, a few transynaptically labeled neurons appeared bilaterally in the medial vestibular nucleus (MVe) and the caudal prepositus hypoglossi (PH) and in the ipsilateral spinal vestibular nucleus (SpVe). At survival times of 96-120 h, labeled neurons were consistently observed bilaterally in all vestibular nuclei (VN), although the highest concentration of infected cells was located in the caudal part of the MVe, the SpVe, and the caudal portion of PH. The distribution and density of labeling in the VN and PH were similar in sympathectomized and nonsympathectomized rats. These anatomical data provide the first direct evidence that neurons in the VN and PH project bilaterally to populations of motoneurons innervating the lower third of the superficial layer of the masseter muscle. The MVe, PH, and SpVe appear to play a predominant integrative role in producing vestibulo-trigeminal responses.
先前的研究报道，支配咬肌的三叉神经运动神经元的活动受前庭传入神经的调节。我们进行本研究是为这些生理学观察提供解剖学基础。将经突触逆行示踪剂伪狂犬病病毒 - 巴塔株注射到大鼠咬肌浅层下三分之一的多个部位，其中一部分在病毒注射前进行了交感神经切除术，然后在24 - 120小时后对动物实施安乐死。接种24小时后，首次在同侧三叉神经运动核中发现标记的咬肌运动神经元；存活72小时后，受感染运动神经元的数量增加，在≥96小时时，许多这些细胞出现细胞病变迹象。存活72小时后，一些经突触标记的神经元双侧出现在内侧前庭核（MVe）、舌下前置核尾侧部（PH）以及同侧脊髓前庭核（SpVe）。在存活96 - 120小时时，在所有前庭核（VN）中均持续观察到双侧标记的神经元，尽管受感染细胞的最高浓度位于MVe尾部、SpVe以及PH尾部。交感神经切除和未切除的大鼠中，VN和PH中标记的分布和密度相似。这些解剖学数据首次直接证明，VN和PH中的神经元双侧投射至支配咬肌浅层下三分之一的运动神经元群体。MVe、PH和SpVe似乎在产生前庭 - 三叉神经反应中起主要整合作用。
