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

我用DiI和Biocytin标记法研究了发育中的大鼠丘脑皮质轴突的生长及其在大脑皮层中的分布。这些结果表明，丘脑皮质轴突在胚胎期（ED） 16到达中间区，在胚胎期（ED） 18进入大脑皮层深层，在出生后（PD）2开始在发育的第四层形成末端分支，并在PD7形成更清晰的周期性和密集的簇。为了获得大脑皮层第四层标记良好的gaba能神经元进行形态学分析，我在固定切片的gaba免疫阳性神经元中注射了染料。将生物细胞素从后方向注射到大鼠的右丘脑，并顺行标记丘脑皮质轴突。切片进行GABA免疫组化反应，显示GABA阳性神经元与FITC。因此，我在大脑皮层第四层FITC标记的细胞内注射了路西法黄。注射细胞用激光共焦显微镜成像。大多数注射神经元在各年龄段均为多极神经元。在PD7或更年轻的注射细胞中，垂直伸长或多角形的体细胞和垂直伸长的主树突更为常见。在PD14和21时，许多注射细胞的胞体呈球形或椭圆形，胞体向四面八方放射出更多的树突。这些结果表明，gaba能神经元的形态在PD7和pd14之间转变为成熟型。为了研究脑锥体细胞突触形成与丘脑皮质轴突投射的关系，我用生物细胞素顺行标记丘脑皮质轴突，用氟金逆行标记脑锥体细胞。因此，我将路西法黄注射到大脑皮层第V层和第II/III层的氟金标记细胞内。利用电镜标本，对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.