Kuwabara N, DiCaprio R A, Zook J M
Department of Zoological and Biomedical Sciences, Ohio University, Athens.
J Comp Neurol. 1991 Dec 22;314(4):684-706. doi: 10.1002/cne.903140405.
Cells and axons that supply direct afferent input to the medial nucleus of the trapezoid body are described. Afferents were intracellularly labeled in brainstem tissue slices of two rodent and two bat species. The main afferents are calyciferous axons from globular bushy cells of the ventral cochlear nucleus. Calyciferous axons were highly consistent across species, projecting directly from the cochlear nucleus, across the midline in the trapezoid body, to the contralateral medial nucleus of the trapezoid body. Within the target nucleus, a typical axon turned sharply away from horizontal to form a large ending, the calyx of Held, around the soma of a single principal cell. Three groups of calyciferous axons were classified based on the path taken from bend to calyx. In subjects younger than four weeks, single axons often formed two calyces, each on a different cell. These calyx pairs were often found on adjacent or vertically aligned cells. In older animals, calyx pairs were more closely aligned, but fewer double calyx axons were seen. A secondary focus of this study was the system of thin collateral branches that characterizes calyciferous axons in all species. The projection patterns of these collaterals suggest that calyciferous axons may provide ascending input to periolivary cell groups with descending projections. In addition to calyciferous afferents, labeled cells that provide input to the medial nucleus of the trapezoid body from adjacent periolivary cell groups are described. Also described is a type of afferent that descends from the level of the lateral lemniscus to the medial nucleus of the trapezoid body.
本文描述了向梯形体内侧核提供直接传入输入的细胞和轴突。在两种啮齿动物和两种蝙蝠的脑干组织切片中对传入神经元进行了细胞内标记。主要传入神经元是来自腹侧耳蜗核球状浓密细胞的花萼状轴突。花萼状轴突在不同物种间高度一致，直接从耳蜗核发出，穿过梯形体的中线，投射到对侧梯形体内侧核。在靶核内，典型的轴突会急剧偏离水平方向，在单个主细胞的胞体周围形成一个大的终末，即 Held 花萼。根据从弯曲处到花萼的路径，将三组花萼状轴突进行了分类。在四周龄以下的个体中，单个轴突常常形成两个花萼，每个花萼位于不同的细胞上。这些花萼对常常出现在相邻或垂直排列的细胞上。在年龄较大的动物中，花萼对排列更为紧密，但双花萼轴突较少见。本研究的另一个重点是细侧支系统，该系统是所有物种花萼状轴突的特征。这些侧支的投射模式表明，花萼状轴突可能为具有下行投射的橄榄周细胞群提供上行输入。除了花萼状传入神经元外，还描述了从相邻橄榄周细胞群向梯形体内侧核提供输入的标记细胞。还描述了一种从外侧丘系水平下行至梯形体内侧核的传入神经元类型。
