Directed early axonal outgrowth from retinal transplants into host rat brains.
Directed early axonal outgrowth from retinal transplants into host rat brains.
复制标题
视网膜移植到宿主大鼠大脑中的定向早期轴突生长。
DOI：
10.1002/neu.480210806
复制
发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Lund,RD
中科院分区：
文献类型：
--
作者：
Hankin,MH;Lund,RD
从视网膜移植到新生大鼠脑干的轴突表现出两种生长模式，可以根据移植物的位置在实验上彼此解耦。靠近嘴侧脑干表面的视网膜（距离顶盖5 mm）发出轴突，轴突沿嘴侧脑干的软膜下缘沿着向上级丘投射。相比之下，只要视网膜在顶盖表面约1 mm范围内，来自深深嵌入中脑实质内的移植物的轴突就会穿过神经毡直接投射到覆盖的上级丘。本研究表明，只要视网膜位于上级丘外，无论轴突是否来自软膜下或实质内位置的移植物，最早的预测是朝向上级丘。然而，我们也发现，直接移植到上级丘的视网膜轴突可以形成沿着软膜下缘远离顶盖的突起。从这些观察中可以得出几个主要结论。首先，最终的顶盖、移植衍生的投射并不是由最初随机生长的重组产生的，而是从一开始就指向一个适当的终止区域。第二，视网膜轴突与主要目标的相互作用改变了生长锥对沿视束沿着的方向线索的反应能力。因此，虽然增加支持的建议，视神经轴突达到上级丘通过相互作用，涉及基板分布沿着视束和扩散的因素起源于目标区域，它是越来越清楚，这种相互作用可能是复杂的和分层的。
Axons from retinae transplanted to the brain stem of neonatal rats exhibit two patterns of outgrowth that can be experimentally uncoupled from each other depending upon the location of the graft. Retinae placed close to the surface of the rostral brain stem (as much as 5 mm from the tectum) emit axons that project toward the superior colliculus along the subpial margin of the rostral brain stem. In contrast, axons from grafts embedded deep within the midbrain parenchyma project through the neuropil directly to the overlying superior colliculus, as long as the retina is within about 1 mm of the tectal surface. The present study shows that, as long as the retina is located outside the superior colliculus, and regardless of whether the axons derive from grafts in subpial or intraparenchymal locations, the earliest projections are oriented towards the superior colliculus. We have also found, however, that axons from retinae transplanted directly onto the superior colliculus can form projections that extend along the subpial margin away form the tectum. There are several major conclusions that may be drawn from these observations. First, the final tectopetal, transplant‐derived projection does not result from the reorganization of an initially random outgrowth but is directed from the start toward an appropriate region of termination. Second, it appears that the interaction of retinal axons with a primary target alters the ability of the growth cone to respond to directional cues along the optic tract. Thus, although adding support to the proposal that optic axons attain the superior colliculus through an interaction involving substrates distributed along the optic tract and diffusible factors originating in the target region, it is increasingly clear that such interactions are likely to be complex and hierachical.