Zhan Xiping, Ryugo David K
Department of Otolaryngology--Head and Neck Surgery, Center for Hearing and Balance, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
J Comp Neurol. 2007 Oct 10;504(5):583-98. doi: 10.1002/cne.21463.
The lateral reticular nucleus (LRN) resides in the rostral medulla and caudal pons, is implicated in cardiovascular regulation and cranial nerve reflexes, and gives rise to mossy fibers in the cerebellum. Retrograde tracing data revealed that medium-sized multipolar cells from the magnocellular part of the LRN project to the cochlear nucleus (CN). We sought to characterize the LRN projection to the CN using BDA injections. Anterogradely labeled terminals in the ipsilateral CN appeared as boutons and mossy fibers, and were examined with light and electron microscopy. The terminal field in the CN was restricted to the granule cell domain (GCD), specifically in the superficial layer along the anteroventral CN and in the granule cell lamina. Electron microscopy showed that the smallest LRN boutons formed 1-3 synapses, and as boutons increased in size, they formed correspondingly more synapses. The largest boutons were indistinguishable from the smallest mossy fibers, and the largest mossy fiber exhibited 15 synapses. Synapses were asymmetric with round vesicles and formed against thin dendritic profiles characterized by plentiful microtubules and the presence of fine filopodial extensions that penetrated the ending. These structural features of the postsynaptic target are characteristic of the terminal dendritic claw of granule cells. LRN projections are consistent with known organizational principles of non-auditory inputs to the GCD.
外侧网状核（LRN）位于延髓头端和脑桥尾端，参与心血管调节和脑神经反射，并在小脑产生苔藓纤维。逆行追踪数据显示，LRN大细胞部的中型多极细胞投射至蜗神经核（CN）。我们试图通过注射生物素结合蛋白-D（BDA）来描绘LRN向CN的投射。同侧CN中顺行标记的终末表现为终扣和苔藓纤维，并通过光镜和电镜进行检查。CN中的终末场局限于颗粒细胞区（GCD），特别是在沿蜗神经腹前核的表层和颗粒细胞层。电镜显示，最小的LRN终扣形成1 - 3个突触，随着终扣尺寸增大，它们形成的突触相应增多。最大的终扣与最小的苔藓纤维难以区分，最大的苔藓纤维有15个突触。突触为不对称性，有圆形囊泡，形成于以丰富微管和穿透终末的细丝状伪足为特征的细树突轮廓上。突触后靶点的这些结构特征是颗粒细胞终末树突爪的特征。LRN投射与已知的GCD非听觉输入组织原则一致。
