Table_1_Anatomy and Connectivity of the Torus Longitudinalis of the Adult Zebrafish.DOCX

This study describes the cytoarchitecture of the torus longitudinalis (TL) in adult zebrafish by using light and electron microscopy, as well as its main connections as revealed by DiI tract tracing. In addition, by using high resolution confocal imaging followed by digital tracing, we describe the morphology of tectal pyramidal cells (type I cells) that are GFP positive in the transgenic line Tg(1.4dlx5a-dlx6a:GFP)ot1. The TL consists of numerous small and medium-sized neurons located in a longitudinal eminence attached to the medial optic tectum. A small proportion of these neurons are GABAergic. The neuropil shows three types of synaptic terminals and numerous dendrites. Tracing experiments revealed that the main efference of the TL is formed of parallel-like fibers that course within the marginal layer of the optic tectum. A toral projection to the thalamic nucleus rostrolateralis is also observed. Afferents to the TL come from visual and cerebellum-related nuclei in the pretectum, namely the central, intercalated and the paracommissural pretectal nuclei, as well as from the subvalvular nucleus in the isthmus. Additional afferents to the TL may come from the cerebellum but their origins could not be confirmed. The tectal afferent projection to the TL originates from cells similar to the type X cells described in other cyprinids. Tectal pyramidal neurons show round or piriform cell bodies, with spiny apical dendritic trees in the marginal layer. This anatomical study provides a basis for future functional and developmental studies focused on this cerebellum-like circuit in zebrafish.

本研究利用光学显微镜与电子显微镜技术，结合DiI束路追踪法，解析了成年斑马鱼纵行隆起核（torus longitudinalis, TL）的细胞构筑及其主要纤维联系。此外，本研究通过高分辨率共聚焦成像联合数字示踪技术，描述了转基因品系Tg(1.4dlx5a-dlx6a:GFP)ot1中绿色荧光蛋白（GFP）阳性的顶盖锥体细胞（I型细胞）的形态特征。TL由大量中小型神经元组成，这些神经元聚集于附着于视顶盖内侧的纵行隆起结构中，其中仅小部分为γ-氨基丁酸能（GABAergic）神经元。神经纤维网内可见三种类型的突触终末与大量树突。束路追踪实验结果显示，TL的主要传出纤维为类平行纤维轴突束，沿视顶盖的边缘层走行。此外，研究还观察到TL向丘脑吻外侧核的投射通路。TL的传入纤维主要来源于顶盖前区的视觉相关与小脑相关核团，包括顶盖前区中央核、顶盖前区中间核、顶盖前区副连合核，以及峡部的瓣下核。另有证据提示小脑可能向TL提供传入纤维，但该投射的起源尚未得到确切证实。顶盖向TL的传入投射起源于一类与其他鲤科鱼类中描述的X型细胞相似的神经元。顶盖锥体细胞呈圆形或梨形胞体，其顶树突丛分布于视顶盖边缘层并带有棘突。本项解剖学研究为后续针对斑马鱼该小脑样环路的功能与发育相关研究提供了理论基础。