Easter S S, Ross L S, Frankfurter A
Department of Biology, University of Michigan, Ann Arbor 48109-1048.
J Neurosci. 1993 Jan;13(1):285-99. doi: 10.1523/JNEUROSCI.13-01-00285.1993.
Mouse embryos from embryonic days 8.5-10.5 (E8.5-E10.5) were fixed and labeled with an antibody to neuron-specific class III beta-tubulin (Moody et al., 1987; Lee et al., 1990a,b) to reveal the first neurons, axons, and tracts in the brain. They were studied in whole-mounts and in light microscopic sections. Some conclusions were checked by labeling tracts in older embryos (E11.5 and E12.5) with the lipophilic dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine. The first immunoreactive cells appeared at E8.5, prior to neural tube closure, in the neural plate immediately caudal to the optic vesicle. Cells along the dorsal midline of the mesencephalon issued the first axons, on E9.0; the cells were the mesencephalic nucleus of the trigeminal nerve, and the axons formed its descending tract. The tract reached the level of the trigeminal ganglion by E10.0 but did not enter the ganglion until after E12.5. On E9.5, the number of labeled cells and axons in the alar plate of the presumptive diencephalon and mesencephalon had increased substantially, and many of the rostral ones coursed into the basal plate to enter longitudinal tracts there. Two tracts originated from cells in the basal plate: the tract of the postoptic commissure (from the base of the optic stalk to the level of the cephalic flexure) and the medial longitudinal fasciculus (from the level of the cephalic flexure caudally through the mid and hind-brains). By E10.0, a small mammillotegmental tract paralleled the tract of the postoptic commissure, but immunolabeling was so widespread that discrete tracts were impossible to discern in the presumptive diencephalon and mesencephalon. The more rostral regions remained lightly labeled. In the cerebral vesicle, the presumptive cerebral cortex, the first immunoreactive cells appeared at E10.0; they had multiple processes oriented parallel to the pia, and were identified as the Cajal-Retzius cells. By E10.5, no tracts had formed in the cerebral vesicle. All the tracts formed by E10.0 were superficial, in the subpial lamina. Those that can be identified in the adult brain are very deep structures. These results are compared with previous descriptions of the embryonic brains of amphibians, fish, birds, and other mammals, including humans.
对胚胎第8.5 - 10.5天（E8.5 - E10.5）的小鼠胚胎进行固定，并用抗神经元特异性III类β - 微管蛋白抗体进行标记（穆迪等人，1987年；李等人，1990年a、b），以揭示大脑中最早的神经元、轴突和神经束。对其进行整体标本和光学显微镜切片研究。通过用亲脂性染料1,1'-二辛基 - 3,3,3',3'-四甲基吲哚羰花青标记较老胚胎（E11.5和E12.5）中的神经束，对一些结论进行了验证。最早的免疫反应性细胞于E8.5出现，在神经管闭合之前，位于视泡尾侧的神经板中。中脑背中线的细胞在E9.0发出了第一批轴突；这些细胞是三叉神经的中脑核，轴突形成其下行束。到E10.0时，该束到达三叉神经节水平，但直到E12.5之后才进入神经节。在E9.5时，推测的间脑和中脑翼板中标记细胞和轴突的数量大幅增加，许多靠前的细胞进入基板以进入那里的纵向神经束。有两条神经束起源于基板中的细胞：视交叉后束（从视柄基部到头部弯曲水平）和内侧纵束（从头部弯曲水平向后穿过中脑和后脑）。到E10.0时，一条小的乳头体被盖束与视交叉后束平行，但免疫标记非常广泛，以至于在推测的间脑和中脑中无法辨别离散的神经束。更靠前的区域标记仍然较浅。在脑泡中，推测的大脑皮层中最早的免疫反应性细胞于E10.0出现；它们有多个与软脑膜平行的突起，并被鉴定为Cajal - Retzius细胞。到E10.5时，脑泡中尚未形成神经束。到E10.0时形成的所有神经束都位于软膜下层的表面。在成体脑中可识别的那些神经束是非常深的结构。将这些结果与先前对两栖动物、鱼类、鸟类和其他哺乳动物（包括人类）胚胎脑的描述进行了比较。
