Willard F H, Ho R H, Martin G F
Brain Res Bull. 1984 Mar;12(3):253-66. doi: 10.1016/0361-9230(84)90053-4.
The opossum dorsal cochlear nucleus is divided into four layers distinguishable either on the basis of differential distribution of neuron types or by neuropil organization. We have used Nissl, Golgi and protargol stained preparations to examine these components. Four types of neurons (excluding granule cells) are seen. The principal neurons have large cell bodies arranged in a sheet defining layer II, their apical dendrites extend dorsally to form an elaborate arbor in layer I and their basal dendrites pass ventrally into layer III. Round cells are found throughout layers I and II. Their densely packed dendritic domains feature thick spine encrusted dendrites that have many recurrent branches. Giant neurons have large perikarya scattered throughout layers III and IV and long thick dendrites that radiate throughout the nucleus. Small multipolar neurons (stellate cells) are found throughout the nucleus. The more superficial ones have small perikarya whereas those found in deeper layers tend to be large. All four layers of the nucleus may be clearly differentiated in protargol stained sections. Layer I has small, thin fibers in parallel array, layer II has a mixture of fibers with an apparent random orientation, layer III has large diameter vertically oriented fibers, and layer IV has fibers of similar diameter but deposed horizontally. Immunohistochemical techniques have been used to identify specific fiber systems in the neuropil of the dorsal cochlear nucleus. Fibers containing 5-hydroxytryptamine (5-HT) immunoreactivity were prevalent in layers I, III and IV but sparse in layer II. Fibers containing enkephalin (ENK)-immunoreactivity were prevalent in layer I and II with only a few scattered fibers in the deeper layers. Isolated clusters of 5-HT and ENK immunoreactive fibers in layer II were found around principal neuron somata; similar clusters in the deep layers were located around the somata of giant neurons. The wide distribution of 5-HT immunoreactive fibers suggests they may be involved in a general regulation of activity in this nucleus; conversely the more circumscribed distribution of ENK immunoreactive fibers would suggest a restricted involvement of this fiber system with a specific feature of information processing.
负鼠的背侧耳蜗核可根据神经元类型的差异分布或神经毡组织分为四层。我们使用了尼氏染色、高尔基染色和原银染色制剂来检查这些组成部分。可以看到四种类型的神经元（不包括颗粒细胞）。主要神经元具有排列成薄片的大细胞体，界定了第二层，它们的顶端树突向背侧延伸，在第一层形成精细的树突分支，它们的基底树突向腹侧进入第三层。圆形细胞遍布第一层和第二层。它们密集排列的树突域具有厚的、有棘突覆盖的树突，这些树突有许多反复分支。巨型神经元有大的胞体，散布在第三层和第四层，长而粗的树突向整个核辐射。小多极神经元（星形细胞）遍布整个核。较浅的那些有小的胞体，而在较深层发现的那些往往较大。在原银染色切片中，核的所有四层都可以清楚地分辨出来。第一层有平行排列的小而细的纤维，第二层有纤维的混合物，具有明显的随机取向，第三层有大直径的垂直取向的纤维，第四层有直径相似但水平排列的纤维。免疫组织化学技术已被用于识别背侧耳蜗核神经毡中的特定纤维系统。含有5-羟色胺（5-HT）免疫反应性的纤维在第一层、第三层和第四层中普遍存在，但在第二层中稀疏。含有脑啡肽（ENK）免疫反应性的纤维在第一层和第二层中普遍存在，在较深层中只有少数散在的纤维。在第二层中，5-HT和ENK免疫反应性纤维的孤立簇在主要神经元胞体周围被发现；在较深层中，类似的簇位于巨型神经元的胞体周围。5-HT免疫反应性纤维的广泛分布表明它们可能参与该核活动的一般调节；相反，ENK免疫反应性纤维的分布更局限，这表明该纤维系统在信息处理的特定特征方面参与有限。
