Arakawa Takahiro, Iwashita Misato, Matsuzaki Fumio, Suzuki Toshiharu, Yamamoto Tohru
Laboratory of Neuroscience, Faculty of Pharmaceutical Sciences, Hokkaido University, Kita12-Nishi6, Kita-ku, Sapporo, Japan.
Brain Res. 2008 Aug 5;1223:25-33. doi: 10.1016/j.brainres.2008.05.062. Epub 2008 Jun 3.
The paths of embryonic chick spinal commissural neurons originating from the lumbosacral (LS) 2 spinal segment and born around Hamburger-Hamilton stage (HH) 18 were observed by labeling the axons with an in ovo electroporation method designed to limit the electroporated area to approximately one somite length. After crossing the floor plate, these axons followed two major paths, one ventral and one dorsal, and a minor path running between the major ones. These axons reached the brachial region by HH28, passed through the cervical region at HH29, and entered the medullary area by HH30. The dorsal axons entered the developing cerebellum by HH33, crossed the midline again, and spread into the rostral-ipsilateral area of the developing cerebellum so that most of them were confined to lobules II-III by HH39. A small population of ventrally running axons turned to enter the cerebellum, and the rest entered the superior medullary velum between the cerebellum and the midbrain. The LS2-originating axons that ascended ipsilaterally into the cerebellum followed a single path, and their extension was delayed compared with that of the commissural axons. Some of the ipsilateral axons innervated the cerebellum; the rest entered the superior medullary velum. These direct observations of the formation of part of the spinocerebellar projections in chick will be a useful reference for future analyses of the underlying mechanisms.
通过一种旨在将电穿孔区域限制在大约一个体节长度的卵内电穿孔方法标记轴突，观察了源自腰荐（LS）2脊髓节段且在汉伯格-汉密尔顿（HH）18期左右生成的胚胎鸡脊髓连合神经元的轴突路径。穿过底板后，这些轴突沿着两条主要路径，一条腹侧路径和一条背侧路径，以及一条在主要路径之间的次要路径延伸。这些轴突在HH28时到达臂部区域，在HH29时穿过颈部区域，并在HH30时进入延髓区域。背侧轴突在HH33时进入发育中的小脑，再次穿过中线，并扩散到发育中小脑的吻侧同侧区域，因此到HH39时，它们中的大多数局限于小叶II - III。一小部分腹侧延伸的轴突转向进入小脑，其余的进入小脑和中脑之间的上髓帆。源自LS2且同侧向上进入小脑的轴突沿着单一路径延伸，与连合轴突相比，它们的延伸延迟。一些同侧轴突支配小脑；其余的进入上髓帆。对鸡脊髓小脑投射部分形成的这些直接观察将为未来对潜在机制的分析提供有用的参考。
