Deller T, Adelmann G, Nitsch R, Frotscher M
Anatomisches Institut I, Universität Freiburg, Postfach 111, D-79001 Freiburg, Germany.
Cell Tissue Res. 1996 Dec;286(3):293-303. doi: 10.1007/s004410050699.
Neurons of the entorhinal cortex project to the hippocampus proper and dentate gyrus. This projection is called the "perforant pathway" because it perforates the subiculum; current usage applies this term to all entorhino-hippocampal fibers. However, entorhinal fibers also reach Ammon's horn via the alveus ("alvear pathway"), an alternative route first described by Cajal. The anterograde tracer Phaseolus vulgaris leucoagglutinin (PHAL) was used in order to analyze the contribution of this pathway to the temporo-ammonic projection. In the temporal portion of the rat hippocampus, most of the entorhinal fibers reach Ammon's horn after perforating the subiculum (classical perforant pathway). At more septal levels, the number of entorhinal fibers that take the alvear pathway increases; in the septal portion of the hippocampal formation, most of the entorhinal fibers to hippocampal subfield CA1 reach this subfield via the alveus. These fibers make sharp right-angle turns in the alveus, perforate the pyramidal cell layer, and finally terminate in the stratum lacunosum-moleculare. The crossed temporo-ammonic fibers reach their termination area in the stratum lacunosum-moleculare of CA1 almost exclusively via the alveus. These data indicate that the alveus is a major route by which entorhinal fibers reach their targets in CA1.
内嗅皮质的神经元投射至海马本部和齿状回。这一投射被称为“穿通通路”，因为它穿过下托；目前的用法将该术语应用于所有内嗅-海马纤维。然而，内嗅纤维也通过海马槽（“槽通路”）到达海马角，这是卡哈尔首次描述的一条替代路径。为了分析这条通路对颞叶-海马投射的贡献，使用了顺行示踪剂菜豆凝集素（PHAL）。在大鼠海马的颞叶部分，大多数内嗅纤维在穿过下托后到达海马角（经典穿通通路）。在更靠隔区的水平，走行槽通路的内嗅纤维数量增加；在海马结构的隔区部分，大多数投射至海马亚区CA1的内嗅纤维通过海马槽到达该亚区。这些纤维在海马槽内急转弯，穿过锥体细胞层，最终终止于腔隙-分子层。交叉的颞叶-海马纤维几乎完全通过海马槽到达其在CA1腔隙-分子层的终末区域。这些数据表明，海马槽是内嗅纤维到达其在CA1靶点的主要途径。
