应用神经轴突示踪技术研究人类视觉神经通路胚胎发育

目的 :应用神经轴突示踪方法 ,研究人类视觉神经通路在胚胎期 12w时的发育情况。方法 :取 12w胎龄的胚胎 ,浸泡在 4 %的甲醛缓冲液中固定后 ,分别在视束、上丘臂和视皮质下植入DiI染料 (DiI,1,1’ dioctadecyl 3,3,3’ ,3’ tetramethylin docarbocyanineperchlorate)。于室温下放置 4w ,待DiI晶体充分扩散后 ,根据神经轴突方向切片 ,通过共焦激光扫描显微镜观察并记录结果。结果 :大体标本观察可见到 ,视网膜神经纤维投射已到达外侧膝状体、上丘。切片观察发现 :外侧膝状体处尚未出现分层现象 ;上丘处 ,来自视网膜的神经纤维位于上丘臂的背侧 ;视皮质下已存在板层结构 ,板层内神经元呈多种形态。结论 :通过神经轴突示踪技术发现 ,12w时视网膜的神经纤维投射已经到达外侧膝状体和上丘 ,视皮质下存在板层结构。这说明人类视觉神经通路发育存在“等待期”。

Prenatal development of human visual system--an assessment using axon tracer

Objective: To reveal morphological features of visual system during early prenatal developm ent.Methods: A fetal brain(age 12 GW) was immersed in 4% formaldehyde for fixation. DiI(1,1'-dioctadecyl-3,3,3',3'-tetramethylin-docarbocyanine perchlorate) wa s em bedded into the optic tract,brachium of superior colliculus and in the intermed iate zone of the medial occipital lobe. The embedded brain tissue was incubated at room temperature for 4 weeks. And then the tissue was sectioned,mounted afte r DiI diffused through the entire axons of the visual system. The slides were ob served under confocal laser scanning microscopy.Results: It was showed that axons from retina have already reached lateral geniculate nuc leus(LGN) and superior colliculus(SC) in the brain tissue. Under the confocal laser scanning microscopy,retinogeniculate axon has already reached L GN but there is no cellular lamination. Axons from retina also have arrived at S C,and the fibers were distributed along the dorsal part of SC. There were subpl ates under visual cortex,and neurons within the subplate appeared to be polymor phous. Conclusion: The retinogeniculate axon reaches LGN by 12 ws,but cellular lamination does not. The axon from retina reaches SC and the subplate under visual cortex forms duri ng early prenatal fetus.