Khachab M Y, Bruce L L
Department of Biomedical Sciences, Creighton University, Omaha, NE 68178-0405, USA.
Brain Res Dev Brain Res. 1999 May 14;114(2):179-92. doi: 10.1016/s0165-3806(99)00020-6.
To determine the role of retinal axons in the development of the corticocollicular projection in mice, the lipophilic fluorescent dye, DiI, was used to compare the development of the cortical projections in phenotypically normal (C57BL/6J) mice to that of anophthalmic 129SV/CPorJ mice. Cortical axons in anophthalmic mice found their targets and established a laminar specificity similar to those of cortical axons in normal mice despite the absence of the retinal projection. Cortical axons in normal mice reached the superior colliculus before those in anophthalmic mice and also had a faster rate of growth within the colliculus. Unlike cortical axons in normal mice in early postnatal ages, those in anophthalmic mice formed a disperse bundle in the stratum opticum. Axons labeled by focal applications of DiI into area 17 terminated in a larger and more medial area in anophthalmic mice than in normal mice. Thus, retinal axons are not essential for cortical axons to reach the superior colliculus, but they may have a role in organizing the growth of later-arriving cortical axons. Furthermore, cortical axons can terminate in the superior colliculus with a coarse topography when retinal axons are absent, but they cannot form a topographically refined projection.
为了确定视网膜轴突在小鼠皮质-皮质下投射发育中的作用，使用亲脂性荧光染料DiI，比较表型正常（C57BL/6J）小鼠与无眼129SV/CPorJ小鼠皮质投射的发育情况。尽管没有视网膜投射，但无眼小鼠的皮质轴突仍找到了它们的靶标，并建立了与正常小鼠皮质轴突相似的分层特异性。正常小鼠的皮质轴突比无眼小鼠的皮质轴突更早到达上丘，并且在上丘内的生长速度也更快。与出生后早期正常小鼠的皮质轴突不同，无眼小鼠的皮质轴突在视层形成了分散的束。通过将DiI局部应用于17区标记的轴突，在无眼小鼠中比在正常小鼠中终止于更大且更内侧的区域。因此，视网膜轴突对于皮质轴突到达上丘不是必需的，但它们可能在组织后来到达的皮质轴突的生长中发挥作用。此外，当没有视网膜轴突时，皮质轴突可以以上丘粗略的拓扑结构终止，但它们不能形成拓扑结构精细的投射。
