Frotscher M, Gähwiler B H
Institute of Anatomy, Johann Wolfgang Goethe University, Frankfurt am Main, F.R.G.
Neuroscience. 1988 Feb;24(2):541-51. doi: 10.1016/0306-4522(88)90348-x.
Pyramidal cells of regio inferior in slice cultures of the rat hippocampus were impaled and intracellularly stained with horseradish peroxidase. A correlated light- and electron-microscopic analysis was then performed to study the properties of these neurons under culture conditions with particular emphasis on input synapses onto these cells. Like pyramidal cells in situ, CA3 pyramidal neurons in slice cultures had a triangular cell body with an apical stem dendrite emerging from it. Several basal dendrites and the axon arose from the basal pole of the cell body. The peripheral thin branches of both apical and basal dendrites were covered with small spines, whereas proximal thick dendritic segments and portions of the cell body exhibited large spines or excrescences. The axon gave off numerous fine varicose collaterals which projected to stratum radiatum of CA1 (Schaffer collaterals), to the alveus and to the hilar region. In one case a collateral could be followed to stratum moleculare of the fascia dentata. Electron-microscopic analysis of the injected pyramidal neurons revealed that their cell bodies, dendritic shafts and spines formed synaptic contacts with presynaptic terminals. Mossy fiber endings were identified by their large size and their numerous clear synaptic vesicles with some dense-core vesicles intermingled, and were observed to form synaptic contacts on the large spines or excrescences. Since extrinsic afferents degenerate in slice cultures, the numerous synaptic boutons on the identified pyramidal neurons probably arise from axons of intrinsic neurons that have sprouted in response to deafferentation. This assumption is supported by the finding that collaterals of the injected neurons formed abundant synaptic contacts on dendritic shafts and spines of other cells. These results suggest that, although pyramidal cells under culture conditions retain a remarkable number of their normal characteristics, considerable synaptic reorganization does take place.
在大鼠海马切片培养物中，对海马下区域的锥体细胞进行刺入，并使用辣根过氧化物酶进行细胞内染色。然后进行相关的光学显微镜和电子显微镜分析，以研究这些神经元在培养条件下的特性，特别强调这些细胞上的输入突触。与原位锥体细胞一样，切片培养物中的CA3锥体细胞有一个三角形的细胞体，从细胞体发出一条顶端主干树突。几条基底树突和轴突从细胞体的基部发出。顶端和基底树突的外周细分支都覆盖着小棘，而近端粗树突段和细胞体的部分区域则呈现大棘或赘生物。轴突发出许多细小的曲张侧支，投射到CA1的辐射层（谢弗侧支）、海马槽和门区。在一个案例中，一条侧支可以追踪到齿状回的分子层。对注入的锥体细胞进行电子显微镜分析发现，它们的细胞体、树突干和棘与突触前终末形成突触联系。苔藓纤维终末通过其较大的尺寸和众多清亮突触小泡与一些致密核心小泡混合而被识别，并观察到它们在大棘或赘生物上形成突触联系。由于在切片培养物中外周传入纤维会退化，因此在已识别的锥体细胞上的大量突触小体可能来自于因去传入作用而发芽的内在神经元的轴突。这一假设得到了以下发现的支持：注入神经元的侧支在其他细胞的树突干和棘上形成了丰富的突触联系。这些结果表明，尽管培养条件下的锥体细胞保留了相当数量的正常特征，但确实发生了相当程度的突触重组。
