Seroogy K B, Seress L, Ribak C E
Exp Neurol. 1983 Dec;82(3):594-608. doi: 10.1016/0014-4886(83)90083-3.
Previous studies have described the polymorph neurons in the hilus of the dentate gyrus at the light microscopic level and have indicated that many of those neurons are the cells of origin for both ipsilateral associational and commissural projections to the dentate gyrus. Because previous studies have not described the ultrastructural characteristics of the hilar neurons, we identified these features of the commissural neurons in the hilus. The method of retrograde transport of horseradish peroxidase (HRP) was utilized with a silver staining technique for HRP intensification. Two populations of labeled commissural neurons were observed in electron microscopic preparations of the contralateral hilus. One type consisted of cells with somata that exhibited round or oval nuclei with no intranuclear inclusions and formed symmetric axosomatic synapses. The main dendrites of those neurons were thick and tapering. In contrast, the other type of labeled neuronal soma had infolded nuclei containing intranuclear rods or sheets, displayed both symmetric and asymmetric axosomatic synapses, and had dendrites that were less thick and generally aspinous. In those same preparations, labeled commissural axon terminals formed synapses with dendrites and dendritic spines in the hilus and molecular layer and with somata in the granule cell layer. From the results of this study it appears that there are two distinct populations of commissural hilar neurons: one type resembles the morphology of the spiny CA3 pyramidal neuron, a type of excitatory projection cell, and the other type is similar to the dentate gyrus basket cell, a local circuit neuron associated with GABAergic inhibition. This latter cell type provides further support for the notion that some commissural neurons are inhibitory.
以往的研究已在光学显微镜水平描述了齿状回门区的多形神经元，并指出这些神经元中的许多是向齿状回发出同侧联合投射和连合投射的起源细胞。由于以往的研究未描述门区神经元的超微结构特征，我们确定了门区连合神经元的这些特征。采用辣根过氧化物酶（HRP）逆行运输方法并结合用于增强HRP的银染技术。在对侧门区的电子显微镜标本中观察到两类标记的连合神经元。一类由胞体组成，其细胞核呈圆形或椭圆形，无核内包涵体，并形成对称的轴体突触。这些神经元的主要树突粗且逐渐变细。相比之下，另一类标记的神经元胞体有内陷的细胞核，含有核内棒或片层，显示对称和不对称的轴体突触，其树突较细且通常无棘。在相同的标本中，标记的连合轴突终末与门区和分子层的树突及树突棘以及颗粒细胞层的胞体形成突触。从这项研究的结果来看，似乎存在两种不同类型的连合门区神经元：一类类似于有棘的CA3锥体神经元的形态，这是一种兴奋性投射细胞，另一类类似于齿状回篮状细胞，这是一种与GABA能抑制相关的局部回路神经元。后一种细胞类型进一步支持了一些连合神经元具有抑制作用这一观点。
