Analysis of synaptic formation on the cerebral pyramidal cell associated with the projection of thalamocortical axons

我用DiI和生物细胞素标记法研究了发育中大鼠丘脑皮质轴突的生长及其在大脑皮层的分布。这些结果显示了丘脑皮质轴突在胚胎第16天到达中间带时的形态，在胚胎第18天进入大脑皮层深层，在出生后第2天开始在发育的第IV层形成终末分支，并在出生后第7天形成更清晰的周期性和致密的簇状结构。为了获得标记良好的大脑皮质第IV层的GABA能神经元进行形态分析，我在固定切片上向GABA免疫阳性神经元注入染料。我从后向大鼠右侧丘脑注射Bicytin，并顺行标记丘脑皮质轴突。切片进行GABA免疫组织化学染色，FITC显示GABA阳性神经元。因此，我将荧光黄注射到大脑皮层第四层FITC标记的细胞中。注射细胞用激光强制显微镜成像。在各个年龄段，大多数注入的神经元都是多极的。在PD7或更年轻的注射细胞中，更常见的是具有垂直延长的或多边形胞体和主要的垂直延长的树突。注射后14、21天，许多注射细胞胞体呈球形或椭圆形，胞体向四面八方放射出较多树突。这些结果表明，GABA能神经元的形态从PD7到PD 14转变为成熟型。为了研究与丘脑皮质轴突投射相关的脑锥体细胞的突触形成，我用Bicytin顺行标记丘脑皮质轴突，用荧光金逆行标记脑锥体细胞。因此，我将荧光黄注射到大脑皮层第V层和第II/III层的荧光金标记细胞中。利用电子显微镜标本，对大脑锥体细胞突触形成的研究正在进行中。

I examined the outgrowth of thalamocortical axons in the developing rat and their distribution in the cerebral cortex with DiI and Biocytin labeling methods. These findings showed the morphology of thalamocortical axons as they arrive at the intermediate zone at embryonic day(ED) 16, as they enter into the deep layer of the cerebral cortex at ED18, and begin to make terminal branching in developing layer IV at postnatal day(PD)2 and form more clearly periodic and dense clusters by PD7.To obtain well-labeled GABAergic neurons in layer IV of the cerebral cortex for morphological analysis, I injected dye into GABA-immunopositive neurons in fixed slices. I injected Biocytin from a posterior direction into the right thalpmus of rats and labeled thalamocortical axons with Biocytin anterogradely. Sections were reacted for GABA immunohistochemistry and revealed GABA positive neurons with FITC. So I injected Lucifer yellow intracellularly into FITC labeled cells in layer IV of the cerebral cortex. Injected cells were imaged with a laser conforcal microscope. Most injected neurons were multipolar at all ages. At PD7 or younger injected cells with vertically elongated or polygonal soma and a major dendrite vertically elongated were more common. At PD14 and 21, many injected- cells had spherical or oval soma and showed more dendrites radiated from the soma in all directions. These findings show the morphology of GABAergic neurons change into mature type between PD7 and PD 14.To study the synaptic formation on the cerebral pyramidal cell associated with the projection of thalamocortical axons, I labeled thalamocortical axons with Biocytin anterogradely and cerebral pyramidal cells with Fluoro-Gold retrogradely. So I injected Lucifer yellow intracellularly into Fluoro-Gold labeled cells in layers V and II/III of the cerebral cortex. Using specimens for an electron microscope, the study of synaptic formation on the cerebral pyramidal cell is in progress.