Eide A L
Department of Physiology, University of Oslo, Norway.
Anat Embryol (Berl). 1996 Jun;193(6):543-57. doi: 10.1007/BF00187926.
The projection pattern of the neurons of the paragriseal Hofmann nuclei was mapped in the chicken embryo using the lipophilic tracer DiI. This report focuses on the pattern of projection from the Hofmann nuclei major observed 1-4 days prior to hatching, at which time the projection appears to be substantially developed. (1) Each neuron extends a commissural axon through the ventral gray matter and across the midline in the ventral commissure. The axons originating from a single Hofmann nucleus cross within a stretch of the cord equivalent to about one spinal segment. There is a small overlap of the axon populations originating from adjacent Hofmann nuclei. After reaching the contralateral ventral columns the individual axons bifurcate and extend rostrally and caudally up to 5 spinal segments in each direction. The rostral and caudal trajectories differ; the rostral axons shift progressively more laterally while the caudal axons tend not to deviate from their initial course. (2) Throughout their longitudinal course the axons give rise to terminal collaterals that are concentrated in lamina 8. Rostrally and caudally the terminals decrease in density and become increasingly scattered. (3) Hofmann neurons are multipolar with 4-5 laterally directed primary dendrites whose arbors are restricted to the Hofmann nucleus major within which the neurons reside. (4) Hofmann neurons receive afferent terminals from a longitudinal column of commissural interneurons located contralaterally in close approximation to the central canal. Each Hofmann nucleus major is innervated by a rostrocaudally restricted subset of these presynaptic neurons. The axon trajectories of the presynaptic neurons are similar to those of the Hofmann neurons. (5) Paragriseal neurons that are not located within Hofmann nuclei major are also commissural intersegmental interneurons and tend to be clustered segmentally. The segmentation is clearest for the Hofmann nuclei minor, which are clusters of neurons iterated along the ventrolateral margin of the thoracic spinal cord but not organized in protruding lobes.
利用亲脂性示踪剂DiI，在鸡胚中绘制了近缝际霍夫曼核神经元的投射模式。本报告重点关注孵化前1 - 4天观察到的主要霍夫曼核的投射模式，此时投射似乎已基本发育完成。（1）每个神经元通过腹侧灰质延伸一条连合轴突，穿过腹侧连合中的中线。源自单个霍夫曼核的轴突在相当于约一个脊髓节段长度的脊髓区域内交叉。源自相邻霍夫曼核的轴突群体有少量重叠。到达对侧腹侧柱后，单个轴突分叉并分别向头侧和尾侧延伸达5个脊髓节段。头侧和尾侧的轨迹不同；头侧轴突逐渐向外侧偏移更多，而尾侧轴突往往不偏离其初始路径。（2）在其纵向行程中，轴突发出集中在第8层的终末侧支。在头侧和尾侧，终末密度降低且越来越分散。（3）霍夫曼神经元是多极的，有4 - 5个向外侧的初级树突，其树突分支局限于神经元所在的主要霍夫曼核内。（4）霍夫曼神经元接受来自位于对侧、紧邻中央管的纵向连合中间神经元柱的传入终末。每个主要霍夫曼核由这些突触前神经元的头尾向受限子集支配。突触前神经元的轴突轨迹与霍夫曼神经元的相似。（5）不在主要霍夫曼核内的近缝际神经元也是连合节段间中间神经元，且倾向于按节段聚集。对于较小的霍夫曼核，节段划分最清晰，它们是沿胸段脊髓腹外侧缘重复排列但未组织成突出叶状的神经元簇。
