Development of signals influencing the growth and termination of thalamocortical axons in organotypic culture
Development of signals influencing the growth and termination of thalamocortical axons in organotypic culture
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DOI：
10.1006/exnr.1999.7032
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发表时间：
1999-04-01
影响因子：
5.3
通讯作者：
Blakemore, C
中科院分区：
文献类型：
--
作者：
Molnár, Z;Blakemore, C
胚胎或出生后大鼠皮质的外植体，在无血清培养基中进行器官型培养，保持其结构完整性，其上层继续成熟。胚胎丘脑部分与不同年龄的皮质切片共培养揭示了皮质信号的时间级联。(1)在E19或更早时取枕叶皮质切片，刺激胚胎外侧膝状体核外植体的轴突生长，但不允许纤维侵入。(2)在E19之后但在P2之前拍摄的皮质切片中，丘脑轴突从任何方向进入切片，并径向延伸穿过皮质板的整个深度，没有分支或终止。(3)在P2后的切片中，纤维减慢，树枝状化，并终止于皮质的成熟层4。如果将丘脑外植体贴着皮层切片的软脑膜表面放置，轴突仍然进入同一层并形成分支。这些发现意味着，发育中的皮层表达一种可扩散的生长促进因子，然后其自身变得允许生长，最后成熟层4表达“停止信号”。在一个丘脑外植体与两个相邻切片的“选择”的三重共培养中，丘脑轴突不会侵入小脑切片，但对来自半球任何区域的切片都有不可否认的反应。因此，丘脑投射在体内的初始切向分布（约由E16实现）不太可能由皮质产生的信号的区域变化控制。当皮质切片单独预培养7-14天，然后再加入胚胎丘脑外植体共培养4天时，神经支配的模式更适合切片的实际年龄，而不是第一次采取的年龄。因此，皮质特性级联的时间至少部分地由内在决定。这些信号的表达序列表明，它们在体内控制丘脑纤维的生长、皮质板下的积聚、板的侵入以及第4层中的树枝状化中发挥作用。(C)北京：科学出版社.
Explants of embryonic or postnatal rat cortex, organotypically cultured in serum-free medium, maintain their structural integrity and their upper layers continue to mature. Coculture of portions of embryonic thalamus with cortical slices taken at different ages reveals a temporal cascade of cortical signals. (1) Slices of occipital cortex taken at E19 or earlier stimulate axonal outgrowth from explants of embryonic lateral geniculate nucleus but do not allow the fibers to invade. (2) In cortical slices taken after E19 but before P2, thalamic axons enter the slice, from any direction, and extend radially across the entire depth of the cortical plate without branching or terminating. (3) In slices taken after P2, fibers slow down, arborize, and terminate in the maturing layer 4 of the cortex. If the thalamic explant is placed against the pial surface of the cortical slice, axons still enter and branch in the same layer. These findings imply that the developing cortex expresses a diffusible growth-promoting factor and then itself becomes growth permissive, and finally the maturing layer 4 expresses a "stop signal." In triple cocultures of one thalamic explant with a "choice" of two neighboring slices, thalamic axons will not invade slices of cerebellum but behave indistinguishably in response to slices from any region of the hemisphere. Thus the initial tangential distribution of the thalamic projection in vivo (which is achieved by about E16) is unlikely to be controlled by regional variation in signals produced by the cortex. When cortical slices were precultured alone for 7-14 days before the addition of an explant of embryonic thalamus for 4 further days of coculture, the pattern of innervation was more appropriate to the chronological age of the slice than the age at which it was first taken. Thus the timing of the cascade of cortical properties is at least partly intrinsically determined. This sequence of expression of these signals suggests that they play a part in vivo in controlling the outgrowth of thalamic fibers, their accumulation under the cortical plate, their invasion of the plate, and their arborization in layer 4. (C) 1999 Academic Press.