内嗅皮质-海马神经投射通路的形成——体内及体外示踪研究

本研究对内嗅皮质一海马通路的各个亚支的发生进行了调查。方法：对不同龄大鼠脑用DiI、DiO、快兰示踪法及calretinin免疫细胞化学法处理。结果：槽通路、海马交通通路于胚胎16天（E16）开始发生,而穿通通路分别始见于胚胎17天海马的腔隙分子层和生后第2天齿状回外分子层。DiI的逆行标记显示内嗅皮质．海马通路主要来自内嗅皮质中Ⅱ到Ⅳ层神经元。另外,calretinin免疫细胞化学法显示Cajal—Retzius（CR）细胞早在胚胎16天存在于海马的腔隙分子层,DiI和calretinin免疫细胞化学法双重标记显示CR细胞和内嗅皮质转入纤维之间可能存在密切的接触关系。结论：嗅皮质-海马通路的各个亚支是按照上述各自的时间表进行发生,CR细胞和穿通纤维的发育时空关系提示该细胞对内嗅皮质传入纤维寻径具有引导作用。

Formation of the entorhino-hippocampal pathway: a tracing study in vitro and in vivo

Objective The entorhino-hippocampal pathway is the major excitatory input from neurons of the entorhinal cortex on both ipsilateral and contralateral hippocampus/dentate gyrus. This fiber tract consists of the alvear path, the perforant path and a crossed commissural projection. In this study, the histogenesis and development of the various subsets of the entorhino-hippocampal projection have been investigated. Methods DiI, DiO and fast blue tracing as well as anti-calretinin immunocytochemistry were carried out with prenatal and postnatal rats at different ages. Results The alvear path and the commissural pathway started to develop as early as embryonic day (E) 16, while the first perforant afferents reached the stratum lacunosum-moleculare of the hippocampus at E17 and the outer molecular layer of dentate gyrus at postnatal day (P) 2, respectively. Retrograde tracing with DiI identified entorhinal neurons in layer II to IV as the origin of entorhino-hippocampal pathway. Furthermore, anti-calretinin immunocytochemistry revealed transitory Cajal-Retzius (CR) cells in the stratum lacunosum-moleculare of the hippocampus from as early as E16. DiI labeling of entorhinal cortex fibers and combined calretinin-immunocytochemistry showed a close association between CR cells and entorhinal afferents. Conclusion The subsets of entorhino-hippocampal pathway appear in the developmental hippocampus during E16-P2. The temporal and spatial relationship between CR cell and perforant afferent suggests the role of this cell type as a guiding cue for entorhinal afferents at early cortical development.