Ruth R E, Collier T J, Routtenberg A
J Comp Neurol. 1982 Jul 20;209(1):69-78. doi: 10.1002/cne.902090107.
Retrograde tracing experiments were performed to clarify the topographic projection from medial (area 28m) and intermediate (area 28i) divisions of the entorhinal cortex to the dentate gyrus. Pipets filled with horseradish peroxidase (HRP) were positioned by electrophysiologic guidance at one of several septotemporal (S-T) levels in the dentate molecular layer of anesthetized rats; the tracer was expelled iontrophoretically to minimize its spread. Retrograde labeling of neurons within areas 28m and 28i was analyzed in relation to cytoarchitectonic as well as spatial features of the region (obtained by histologic reconstruction). Regardless of the S-T level, ejections of HRP which were confined to the dentate gyrus labeled only layer II neurons of each area. Following septal pole ejections, labeled neurons were located in the posterolateral, extreme posterior, and posteromedial parts of both areas 28m and 28i. Mid S-T ejections produced not only a ventral, but also an anteromedial, shift in the location of entorhinal projection cells; no cells were labeled posterolaterally. After temporal dentate ejections labeled neurons occupied the most anteromedial part of these entorhinal areas. For both areas, but especially for area 28i, convergence of entorhinal efferents upon a single S-T level in the dentate gyrus occurred from neurons which lay in a dorsoventral (i.e., frontal), and to a lesser extent a rostrocaudal, plane. The efferent axes of both areas 28m and 28i thus appear to be curved and are therefore best described in three dimensions. The entorhinal axes begin in a posterodorsolateral location, wrap around the posterior cortical convexity, and end in an anteroventromedial position. The results provide a useful map for in situ exploration of entorhinodentate connections in the rat, emphasize the parallel innervation of the dentate gyrus by distinct entorhinal fiber systems, and reflect the importance of the S-T axis as a framework for interpreting hippocampal organization.
进行逆行追踪实验以阐明内嗅皮质的内侧（28m区）和中间（28i区）部分到齿状回的拓扑投射。将充满辣根过氧化物酶（HRP）的移液管在电生理引导下置于麻醉大鼠齿状分子层中几个隔颞（S-T）水平之一处；通过离子电渗法排出示踪剂以尽量减少其扩散。分析28m区和28i区内神经元的逆行标记与该区域的细胞结构以及空间特征（通过组织学重建获得）的关系。无论S-T水平如何，局限于齿状回的HRP注射仅标记每个区域的II层神经元。在隔极注射后，标记的神经元位于28m区和28i区的后外侧、极后部和后内侧部分。S-T中部注射不仅使内嗅投射细胞的位置产生腹侧移位，还产生前内侧移位；后外侧没有细胞被标记。在颞齿状回注射后，标记的神经元占据这些内嗅区域的最前内侧部分。对于这两个区域，尤其是28i区，内嗅传出纤维在齿状回的单个S-T水平上的汇聚发生在位于背腹（即额叶）平面且在较小程度上位于前后平面的神经元之间。因此，28m区和28i区的传出轴似乎是弯曲的，因此最好用三维来描述。内嗅轴始于后背外侧位置，环绕后皮质凸面，止于前腹内侧位置。这些结果为在大鼠中原位探索内嗅-齿状回连接提供了有用的图谱，强调了不同内嗅纤维系统对齿状回的平行支配，并反映了S-T轴作为解释海马组织框架的重要性。
