Fritzsch B, Nichols D H
Department of Biomedical Sciences, Creighton University, Omaha, Nebraska 68178.
Hear Res. 1993 Feb;65(1-2):51-60. doi: 10.1016/0378-5955(93)90200-k.
We have reinvestigated the time of arrival of efferent fibers at the developing otocyst of mice employing diffusion of the lipophilic dye DiI in fixed tissue. In contrast to almost all previous reports, our data indicate a prenatal arrival of efferent fibers. A few efferent fibers were found to enter the eighth nerve root at embryonic day (ED) 10 1/2. Retrogradely labelled efferent cell bodies were at this stage coextensive with those of the facial motor nucleus, but started to segregate by ED 12. In contrast to retrogradely labelled facial motor neurons, labelled efferent neurons were bilaterally distributed in the hindbrain with a few projecting to both otocysts as early as ED 12. Anterograde labelling from the brain showed efferent fibers in the vestibular ganglion by ED 11. Invasion of the future vestibular sensory epithelia started by ED 12. Growth cones of efferent fibers had also reached the future cochlear sensory epithelium but invasion was only achieved by a few filopodia at this stage. The early arrival of efferents at the future sensory epithelia demonstrated here may allow an as yet unexplored interaction of efferent fibers with the proliferating and/or differentiating hair cells.
我们利用亲脂性染料DiI在固定组织中的扩散，重新研究了传出纤维到达发育中小鼠耳囊的时间。与几乎所有先前的报道相反，我们的数据表明传出纤维在产前就已到达。在胚胎第10.5天，发现有少数传出纤维进入第八神经根。在此阶段，逆行标记的传出细胞体与面神经运动核的细胞体重叠，但到胚胎第12天开始分离。与逆行标记的面神经运动神经元不同，标记的传出神经元在后脑双侧分布，早在胚胎第12天就有少数投射到两个耳囊。从脑进行的顺行标记显示，到胚胎第11天，前庭神经节中有传出纤维。在胚胎第12天开始侵入未来的前庭感觉上皮。传出纤维的生长锥也已到达未来的耳蜗感觉上皮，但在此阶段只有少数丝状伪足实现了侵入。此处证明的传出纤维提前到达未来的感觉上皮，可能会使传出纤维与增殖和/或分化的毛细胞发生尚未被探索的相互作用。
