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.

这项研究通过光学和电子显微镜描述了成年斑马鱼纵向环面（TL）的细胞结构，以及通过DiI谱线追踪揭示了其主要联系。此外，通过使用高分辨率共聚焦成像，然后进行数字跟踪，我们描述了转基因品系中GFP阳性的顶角锥体细胞（I型细胞）的形态Tg（1.4dlx5a-dlx6a：GFP）^OT1。TL由位于附在内侧视神经膜上的纵向隆起的众多中小型神经元组成。这些神经元中有一小部分是GABA能的。Neuropil显示了三种类型的突触末端和许多树突。跟踪实验表明，TL的主要作用是由平行状的纤维形成的，这些纤维在视神经外缘的边缘层中行进。还观察到丘脑向外侧丘脑核的投射。TL的传入来自前保护区的视觉和小脑相关核，即中央，插层的和合瓣前的保护前核，以及峡部的瓣膜下核。TL的其他传入者可能来自小脑，但无法确定其起源。TL的顶盖传入投影起源于类似于其他鲤科动物中描述的X型细胞的细胞。椎体锥体神经元显示圆形或梨形细胞体，边缘层有尖顶树突状树。这项解剖学研究为今后针对斑马鱼小脑样回路的功能和发育研究提供了基础。