Ishihara Yoshihisa, Fukuda Takaichi
Department of Anatomy and Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan.
Department of Anatomy and Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan.
Neuroscience. 2016 Nov 19;337:242-266. doi: 10.1016/j.neuroscience.2016.09.027. Epub 2016 Sep 21.
The subiculum is the output component of the hippocampal formation and holds a key position in the neural circuitry of memory. Previous studies have demonstrated the subiculum's connectivity to other brain areas in detail; however, little is known regarding its internal structure. We investigated the cytoarchitecture of the temporal and mid-septotemporal parts of the subiculum using immunohistochemistry. The border between the CA1 region and subiculum was determined by both cytoarchitecture and zinc transporter 3 (ZnT3)-immunoreactivity (IR), whereas the border between the subiculum and presubiculum (PreS) was partially indicated by glutamate receptor 1 (GluR1)-IR. The subiculum was divided into proximal and distal subfields based on cytoarchitecture and immunohistochemistry for calbindin (CB), nitric oxide synthase (NOS) and Purkinje cell protein 4 (PCP4). The proximal subiculum (defined here as subiculum 2) was composed of five layers: the molecular layer (layer 1), the medium-sized pyramidal cell layer (layer 2) that contained NOS- and PCP4-positive neurons, the large pyramidal cell layer (layer 3) characterized by the accumulation of ZnT3- (more proximally) and vesicular glutamate transporter 2-positive (more distally) boutons, layer 4 containing polymorphic cells, and the deepest layer 5 composed of PCP4-positive cells with long apical dendrites that reached layer 1. The distal subiculum (subiculum 1) consisting of smaller neurons did not show these features. Quantitative analyses of the size and numerical density of somata substantiated this delineation. Both the proximal-distal division and five-layered structure in the subiculum 2 were confirmed throughout the temporal two-thirds of the subiculum. These findings will provide a new structural basis for hippocampal investigations.
海马下脚是海马结构的输出组件，在记忆神经回路中占据关键位置。以往研究已详细阐明海马下脚与其他脑区的连接情况；然而，关于其内部结构却知之甚少。我们运用免疫组织化学方法研究了海马下脚颞部和中隔颞部的细胞构筑。CA1区与海马下脚之间的边界通过细胞构筑和锌转运体3（ZnT3）免疫反应性（IR）来确定，而海马下脚与前海马下脚（PreS）之间的边界部分由谷氨酸受体1（GluR1）-IR指示。基于细胞构筑以及钙结合蛋白（CB）、一氧化氮合酶（NOS）和浦肯野细胞蛋白4（PCP4）的免疫组织化学，海马下脚被分为近端和远端亚区。近端海马下脚（在此定义为海马下脚2）由五层组成：分子层（第1层）、包含NOS和PCP4阳性神经元的中型锥体细胞层（第2层）、以ZnT3（更靠近近端）和囊泡型谷氨酸转运体2阳性（更靠近远端）终末的积累为特征的大型锥体细胞层（第3层）、含有多形细胞的第4层以及由具有长顶树突且延伸至第1层的PCP4阳性细胞组成的最深层第5层。由较小神经元组成的远端海马下脚（海马下脚1）未表现出这些特征。对胞体大小和数量密度的定量分析证实了这种划分。海马下脚2中的近端 - 远端划分和五层结构在海马下脚颞部的三分之二区域均得到证实。这些发现将为海马研究提供新的结构基础。
