DEVELOPMENT OF THE MOSSY FIBERS OF THE DENTATE GYRUS .1. A LIGHT AND ELECTRON-MICROSCOPIC STUDY OF THE MOSSY FIBERS AND THEIR EXPANSIONS
DEVELOPMENT OF THE MOSSY FIBERS OF THE DENTATE GYRUS .1. A LIGHT AND ELECTRON-MICROSCOPIC STUDY OF THE MOSSY FIBERS AND THEIR EXPANSIONS
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DOI：
10.1002/cne.901950106
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发表时间：
1981-01-01
影响因子：
2.5
通讯作者：
DENT, JA
中科院分区：
文献类型：
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作者：
AMARAL, DG;DENT, JA
齿状颗粒细胞轴突（即所谓的苔藓纤维）的出生后发育，在蒂姆和高尔基体制剂的光学显微镜水平以及透射电子显微镜下对大鼠进行了研究。在蒂姆染色的材料中，出生后第一天的门和早期透明层有独特的颜色，表明苔藓纤维的存在。在接下来的2周内，染色区域变得更加广泛，染色颗粒的尺寸和密度增加，并且颗粒的染色变得更加强烈。这些苔藓纤维逐渐发育的迹象似乎在时间和地形上反映了其亲本颗粒细胞的发育梯度。高尔基体材料证实出生后第一天肺门中存在苔藓纤维。在 3 日龄海马体的透明层中观察到苔藓纤维束，尽管这些未成熟的轴突缺乏大的突触扩张，但它们的末端确实有明显的生长锥。沿着轴突长度的小扩展首先出现在第 7 天，到第 14 天左右，这些扩展已达到大约成人的大小和复杂性。苔藓纤维突触的突触后成分，即带刺的赘生物，直到第 9 天后的某个时间才开始从锥体细胞树突的近端部分出现。在出生后第一天的 EM 水平上，小的、不成熟的苔藓纤维扩展，使对称和不对称的苔藓纤维扩展。观察到与树突轴直接的不对称接触。这些轮廓的大小仅为成熟扩张的 1/10，在出生后 1-9 天之间迅速生长，并将其平均面积增加了 5 倍。在第 9 天或大约第 9 天，随着多刺赘生物的出现，不对称突触开始与这些棘突相关。总而言之，高尔基体和电镜分析支持这样的观点，即苔藓纤维在出生后早期（即出现任何脊柱发育迹象前几天）与锥体细胞树突建立突触接触。在远端锥体细胞树突上出现更典型的有蒂刺后，就会出现多刺的赘生物。虽然很明显，21 天龄材料中的苔藓纤维大部分已经完全成熟，但成年动物 Timm 制剂中染色颗粒面积和密度的增加表明，该系统的发育更加微妙和持久，一直持续到成年期。
The postnatal development of the axons of the dentate granule cells, the so-called mossy fibers, was studied in the rat at the light microscopic level in Timm and Golgi preparations and also by transmission electron microscopy. In the Timm-stained material, there was a distinctive coloration in the hilus and incipient stratum lucidum, indicating the presence of mossy fibers, on the 1st postnatal day. Over the next 2 wk, the stained areas became more extensive, the size and density of the stained particles increased, and the particles became more intensely stained. These signs of progressive development of the mossy fibers appeared to reflect, temporally and topographically, the developmental gradients followed by their parent granule cells. The Golgi material confirmed the presence of mossy fibers in the hilus on the 1st postnatal day. Fasciculi of mossy fibers were observed in the stratum lucidum of the 3-day-old hippocampus, and although these immature axons were devoid of large synaptic expansions, they did have prominent growth cones at their termini. Small expansions along the lengths of the axons first appeared on day 7 and these grew to approximately an adult size and complexity by about day 14. The postsynaptic component of the mossy fiber synapse, the thorny excrescence, did not begin to emerge from the proximal portion of the pyramidal cell dendrites until sometime after day 9. At the EM level on the 1st postnatal day, small, immature mossy fiber expansions which made both symmetric and asymmetric contacts directly with dendritic shafts were observed. These profiles, which were only 1/10 the size of mature expansions, grew rapidly between postnatal days 1-9 and increased their mean area by a factor of 5. On or about day 9, as the thorny excrescences emerged, the asymmetric synapses came to be associated with these spinous processes. Taken together, the Golgi and EM analyses support the suggestion that mossy fibers establish synaptic contact with pyramidal cell dendrites early in the postnatal period, several days before there is any indication of spine development. The thorny excrescences develop after the more typical, pedicellate spines have appeared on the distal pyramidal cell dendrites. While it is clear that the mossy fibers in 21-day-old material are for the most part fully matured, a more subtle and protracted development of the system, long into adulthood, is indicated by the increased area and density of stained particles in the Timm preparations from adult animals.