The presubiculum plays a key role in processing and integrating spatial and head-directional information. Layer III neurons of the presubiculum provide strong projections to the superficial layers of the medial entorhinal cortex (MEC) in the rat. Our previous study revealed that the terminal distribution of efferents from layer III cells of the presubiculum was organized in a band-like fashion within the MEC, and the transverse axis of these zones ran parallel to the rhinal fissure. Identifying axonal branching patterns of layer III neurons of the presubiculum is important to further elucidate the functional roles of the presubiculum. In the present study, we visualized all axonal processes and terminal distributions of single presubicular layer III neurons in the rat, using in vivo injection of a viral vector expressing membrane-targeted palmitoylation site-attached green fluorescent protein (GFP). We found that layer III of the rat presubiculum comprised multiple types of neurons (n = 12) with characteristic patterns of axonal collateralization, including cortical projection neurons (n = 6) and several types of intrinsic connectional neurons (n = 6). Two of six cortical projection neurons provided two or three major axonal branches to the MEC and formed elaborate terminal arbors within the superficial layers of the MEC. The width and axis of the area of their terminal distribution resembled that of the band-like terminal field seen in our massive-scale observation. Two of the other four cortical projection neurons gave off axonal branches to the MEC and also to the subiculum, and each of the other two neurons sent axons to the subiculum or parasubiculum. Patterns of axonal arborization of six intrinsic connectional neurons were distinct from each other, with four neurons sending many axonal branches to both superficial and deep layers of the presubiculum and the other two neurons showing sparse axonal branches with terminations confined to layers III-V of the presubiculum. These data demonstrate that layer III of the rat presubiculum consists of multiple types of cortical projection neurons and interneurons, and also suggest that inputs from a single presubicular layer III neuron can directly affect a band-like zone of the MEC.

中文翻译：

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大鼠前臼单层III神经元轴突抵押的多种模式。

前房在处理和整合空间和头部信息方面起着关键作用。前臼的第III层神经元向大鼠的内侧内嗅皮层（MEC）的浅层提供了强有力的投射。我们先前的研究表明，前丘脑第三层细胞传出的末梢分布在MEC中以带状方式组织，并且这些区域的横轴平行于鼻裂。识别前臼第三层神经元的轴突分支模式对于进一步阐明前臼的功能作用很重要。在本研究中，我们可视化了大鼠中单个前亚第三层神经元的所有轴突过程和终末分布，使用体内注射表达膜靶向棕榈酰化位点连接的绿色荧光蛋白（GFP）的病毒载体。我们发现大鼠前臼的第三层包括多种类型的神经元（n = 12），具有轴突侧支特征性模式，包括皮质投射神经元（n = 6）和几种内在的连接神经元（n = 6）。六个皮质投射神经元中的两个向MEC提供了两个或三个主要的轴突分支，并在MEC的浅层内形成了精细的末端乔木。其末端分布区域的宽度和轴类似于我们大规模观测中看到的带状末端场的宽度和轴。其他四个皮质投射神经元中的两个向MEC以及下丘脑释放了轴突分支，而其他两个神经元则分别将轴突送至下丘脑或旁睑。六个内在联系神经元的轴突乔化模式彼此不同，四个神经元向前房的浅层和深层发送许多轴突分支，另外两个神经元显示出稀疏的轴突分支，其末端仅限于III-V层。前房。这些数据表明，大鼠前丘脑的第三层由多种类型的皮质投射神经元和中间神经元组成，并且还表明来自单个亚皮层前第三神经元的输入可直接影响MEC的带状区域。四个神经元将许多轴突分支发送至前房的浅表层和深层，而另两个神经元则显示出稀疏的轴突分支，其末端局限于前房的III-V层。这些数据表明，大鼠前丘脑的第三层由多种类型的皮质投射神经元和中间神经元组成，并且还表明来自单个亚皮层前第三神经元的输入可直接影响MEC的带状区域。四个神经元将许多轴突分支发送至前房的浅表层和深层，而另两个神经元则显示出稀疏的轴突分支，其末端局限于前房的III-V层。这些数据表明，大鼠前丘脑的第三层由多种类型的皮质投射神经元和中间神经元组成，并且还表明来自单个亚皮层前第三神经元的输入可直接影响MEC的带状区域。