Rubin E
J Neurosci. 1985 Mar;5(3):685-96. doi: 10.1523/JNEUROSCI.05-03-00685.1985.
The growth of sympathetic preganglionic axons has been studied in the fetal rat. Preganglionic axons first emerge from the spinal cord and enter the paravertebral chain of ganglia between days 12 and 13 of gestation (E12 to E13). By E14, hundreds of preganglionic neurons have sent axons into the sympathetic chain. Even at this age, the arrangement of the preganglionic axons conforms to the adult organization in a number of ways. As in maturity, these axons leave the spinal cord only through the ventral root of the segment in which their cell bodies reside. Furthermore, axons grow into the superior cervical ganglion only from the same set of spinal segments as supply this ganglion in maturity, and in correct segmental proportions, although there is a slight rostral-to-caudal lag along the spinal cord in the full establishment of the projection. The development of appropriate projections in this system owes little to the growth of axons along stereotyped pathways. Rather, preganglionic organization apparently reflects a more general instruction that governs the relative number of axons from each spinal segment which course rostrally or caudally within the sympathetic chain. The appropriate distribution of preganglionic axons early in development suggests that a fiber's segmental level of origin biases the axon to grow in a particular direction.
在胎鼠中对交感神经节前轴突的生长进行了研究。妊娠第12至13天（E12至E13），节前轴突首先从脊髓发出并进入椎旁神经节链。到E14时，数百个节前神经元已将轴突发送到交感神经链中。即使在这个年龄，节前轴突的排列在许多方面也符合成年期的组织结构。与成熟时一样，这些轴突仅通过其细胞体所在节段的腹根离开脊髓。此外，轴突仅从成熟时供应该神经节的同一组脊髓节段以正确的节段比例长入颈上神经节，尽管在投射完全建立时沿脊髓存在轻微的头端到尾端延迟。该系统中适当投射的发育很少归因于轴突沿定型路径的生长。相反，节前组织显然反映了一种更普遍的指令，该指令控制来自每个脊髓节段的轴突在交感神经链中向头端或尾端走行的相对数量。发育早期节前轴突的适当分布表明，纤维起源的节段水平会使轴突偏向于向特定方向生长。
