The entorhino-dentate projection, i.e. the perforant pathway, terminates in a highly ordered and laminated fashion in the rodent dentate gyrus: Fibers arising from the medial entorhinal cortex terminate in the middle molecular layer, whereas fibers arising from the lateral entorhinal cortex terminate in the outer molecular layer of the dentate. In rats and rabbits, a crossed entorhino-dentate projection exists, which originates from the entorhinal cortex and terminates in the contralateral dentate gyrus. In contrast, in mice such a crossed projection is reportedly absent. Using single and double mouse organotypic entorhino-hippocampal slice cultures, we studied the ipsi- and crossed entorhino-dentate projections. Viral tracing revealed that entorhino-dentate projections terminate with a high degree of lamina-specificity in single as well as in double cultures. Furthermore, in double cultures, entorhinal axons arising from one slice freely intermingled with entorhinal axons originating from the other slice. In single as well as in double cultures, entorhinal axons exhibited a correct topographical projection to the dentate gyrus: medial entorhinal axons terminated in the middle and lateral entorhinal axons terminated in the outer molecular layer. Finally, entorhinal neurons were virally transduced with Channelrhodopsin2-YFP and stimulated with light, revealing functional connections between the entorhinal cortex and dentate granule cells. We conclude from our findings that entorhino-dentate projections form bilaterally in the mouse hippocampus in vitro and that the mouse hippocampus provides a permissive environment for crossed entorhinal fibers.

中文翻译：

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交叉的Entohino-齿状投射物形成并在小鼠海马的器官型切片培养物中以正确的层特异性终止

内嗅齿状突起（即穿孔途径）在啮齿动物齿状回中以高度有序和叠层的方式终止：由内侧内嗅皮层产生的纤维终止于中间分子层，而由内侧内嗅皮层产生的纤维终止于内齿层牙齿的外分子层。在大鼠和兔子中，存在一个交叉的内嗅齿状突起，该投影起源于内嗅皮层并终止于对侧齿状回。相反，据报道在小鼠中不存在这种交叉投影。我们使用单次和两次小鼠器官型内嗅-海马切片培养，研究了ips-和交叉的内嗅-齿状投射。病毒示踪显示，在单个和双重培养中，内嗅齿状的投射都以高度的层特异性终止。此外，在双重培养中，源自一个切片的内啡肽轴突与来自另一切片的内啡肽轴突自由地混合。在单一和双重文化中，内嗅轴突对齿状回均显示正确的地形投影：内侧内嗅轴突终止于中间分子内外侧轴突，终止于外分子层。最后，内嗅神经元被Channelrhodopsin2-YFP病毒转导并用光刺激，揭示了内嗅皮质和齿状颗粒细胞之间的功能连接。