Bajo V M, Merchán M A, Malmierca M S, Nodal F R, Bjaalie J G
Laboratorio de Neurobiología de la Audición Instituto de Neurociencias de Castilla y León, Universidad de Salamanca, Spain.
J Comp Neurol. 1999 May 10;407(3):349-66. doi: 10.1002/(sici)1096-9861(19990510)407:3<349::aid-cne4>3.0.co;2-5.
The dorsal nucleus of the lateral lemniscus (DNLL) is an auditory structure of the brainstem. It plays an important role in binaural processing and sound localization and it provides the inferior colliculus with an inhibitory projection. The DNLL is a highly conserved auditory structure across mammals, but differences among species in its detailed organization have been reported. The main goal of this study was to analyze the topographic organization of the cat DNLL. Single, small iontophoretic injections of biotinylated dextran amine were made at different loci in the central nucleus of the inferior colliculus (CNIC). The distribution of the labeled structures in the ipsi- and contralateral DNLL was computer reconstructed in three dimensions. In individual sections, a band of labeling is seen in the DNLL on both sides. These two labeled bands occupy symmetric locations and are made of retrogradely labeled neurons with flattened dendritic arbors oriented parallel to each other. Moreover, the ipsilateral labeled band contains labeled terminal fibers parallel to the labeled dendrites. With three-dimensional reconstructions, it becomes evident that the labeled band seen in each individual DNLL section represents a slice through a rostrocaudally oriented lamina. The shape, size, orientation, and location of this lamina change as the injection site is shifted along the tonotopic axis of the CNIC. An injection in the low-frequency region of the CNIC, produces a lamina that resembles a flattened tube located in the dorsolateral corner of the DNLL. An injection in the high-frequency region of the CNIC, by contrast, results in a lamina that is an elongated sheet located at the ventromedial surface of the DNLL. The laminae of the DNLL might constitute the structural basis for its tonotopical organization. Previous studies (Merchan MA, et al. 1994. J Comp Neurol 342:259-278) in conjunction with our current results suggest that the laminar organization in the DNLL might be common among mammals.
外侧丘系背核（DNLL）是脑干的一个听觉结构。它在双耳处理和声音定位中起重要作用，并向下丘提供抑制性投射。DNLL是哺乳动物中高度保守的听觉结构，但已报道不同物种在其详细组织上存在差异。本研究的主要目的是分析猫DNLL的拓扑组织。在下丘中央核（CNIC）的不同位点进行单次、小剂量的生物素化葡聚糖胺离子电渗注射。对同侧和对侧DNLL中标记结构的分布进行三维计算机重建。在各个切片中，两侧的DNLL都可见一条标记带。这两条标记带占据对称位置，由逆行标记的神经元组成，其扁平的树突彼此平行排列。此外，同侧标记带包含与标记树突平行的标记终末纤维。通过三维重建可以明显看出，在每个单独的DNLL切片中看到的标记带代表了一个沿 rostrocaudally 方向排列的薄片的切片。随着注射部位沿CNIC的音调轴移动，该薄片的形状、大小、方向和位置会发生变化。在CNIC低频区域的注射会产生一个类似于位于DNLL背外侧角的扁平管的薄片。相比之下，在CNIC高频区域的注射会导致一个位于DNLL腹内侧表面的细长薄片。DNLL的薄片可能构成其音调组织的结构基础。先前的研究（Merchan MA等人，1994年。《比较神经学杂志》342:259 - 278）结合我们目前的结果表明，DNLL中的层状组织在哺乳动物中可能很常见。
