Li D, Field P M, Starega U, Li Y, Raisman G
Norman and Sadie Lee Research Centre, National Institute for Medical Research, Mill Hill, London, U.K.
Neuroscience. 1993 Feb;52(4):799-813. doi: 10.1016/0306-4522(93)90530-s.
We have demonstrated the formation of entorhinodentate projections by axons arising from explants of embryonic mouse entorhinal cortex or slices of postnatal rat entorhinal area co-cultured in contact with slices of postnatal rat hippocampus in roller tube and static culture. Species-specific markers (Thy-1 alleles and M6) showed that the most dense part of the projection was to the outer part of the molecular layer of the dentate gyrus (i.e. excluding the commissural-association zone). Retrograde axonal transport of fluorescent tracers placed in the dentate gyrus labelled a densely packed superficial layer of stellate cells in the entorhinal cortex. Anterograde axonal transport of biocytin placed in the entorhinal cortex showed that the entorhinodentate fibres formed typical parallel bundles oriented at right angles to the dentate granule cell dendrites and had short-stalked boutons. The formation of entorhinodentate synapses was confirmed in the electron microscope by electron-dense degeneration after cutting the previously formed connection between the co-cultures. Synaptic transmission was demonstrated by extracellular recording of postsynaptic field potentials after entorhinal stimulation. The entorhinal fibres also projected to the hippocampal stratum lacunosum-moleculare of fields CA1 and CA3, and were present in the outer part of the stratum oriens of the subiculum; in some cases they perforated the pyramidal cell layer of the subiculum. We conclude that the necessary molecular and tissue organizational signals for the formation of an entorhinodentate projection are present in tissues maintained in organotypic slice co-culture, and remain effective in the cross-species mouse-to-rat situation.
我们已经证明，在滚管和静态培养中，将胚胎小鼠内嗅皮层的外植体或出生后大鼠内嗅区的切片与出生后大鼠海马体的切片接触共培养时，轴突会形成内嗅 - 齿状投射。物种特异性标记物（Thy - 1等位基因和M6）显示，投射最密集的部分位于齿状回分子层的外侧部分（即不包括连合 - 联合区）。将荧光示踪剂置于齿状回中进行逆行轴突运输，标记了内嗅皮层中一层密集排列的星状细胞。将生物素置于内嗅皮层进行顺行轴突运输显示，内嗅 - 齿状纤维形成了典型的平行束，与齿状颗粒细胞树突成直角排列，并具有短柄终扣。通过切断共培养物之间先前形成的连接后进行电子致密性退变，在电子显微镜下证实了内嗅 - 齿状突触的形成。通过对内嗅刺激后突触后场电位进行细胞外记录，证明了突触传递。内嗅纤维也投射到CA1和CA3区海马的腔隙 - 分子层，并且存在于下托原层的外侧部分；在某些情况下，它们穿过下托的锥体细胞层。我们得出结论，在器官型切片共培养中维持的组织中存在形成内嗅 - 齿状投射所需的分子和组织组织信号，并且在跨物种小鼠 - 大鼠的情况下仍然有效。
