初级传入纤维在发育阶段小鼠腰髓背角内生长特点的研究(英文)

DEVELOPMENTAL ORGANIZATION OF PRIMARY AFFERENT FIBERS IN THE DORSAL HORN OF THE MOUSE LUMBAR SPINAL CORD

本研究通过将亲脂性羰花青染料 Di I置入胚胎 12 d(E12 )到生后 3 d(P3 )小鼠背根神经节内进行追踪的方法 ,观察了初级传入纤维在小鼠腰段脊髓背角内生长过程和终止的形态特点。结果显示 ,初级传入纤维在 E13时生长至脊髓后索 ,在此停留 2d,到 E15时开始进入脊髓灰质。 E16和 E17时 ,生长至脊髓灰质内的初级传入纤维的数量增加并向腹角延伸。有相当数量的初级传入纤维进入脊髓背角深层。至 E18,背角深层的传入纤维的密度进一步增加 ,分支的状态变得更为复杂。一些分支延伸到背角浅层。在出生后 ,初级传入纤维在脊髓背角的分布特点无明显变化 ,但是在背角前层的纤维数量进一步增多。另外 ,还观察到初级传入纤维发出侧支向对侧脊髓背角的投射。这种向对侧生长的纤维侧支开始于 E16,来源于同侧背角内侧部的传入纤维。至E18和出生时 ,向对侧背角生长的侧支的来源部位增加到两个。本研究的结果表明 ,小鼠脊髓背角内初级传入纤维的板层分布模式形成于胚胎发育的晚期和出生后的早期 ,此后初级传入纤维在背角内进行进一步的精细调整 ,达到与成年时一致的状态。

The present study was designed to examine the morphological pattern of primary afferent projections into the spinal dorsal horn by labeling the lumbar dorsal root ganglia with carbocyanine fluorescent dye DiI in mouse embryos and neonatal pups aged embryonic day 12 to postnatal day 3 (E12-P3). Primary afferent fibers projected into dorsal funiculus at E13, but did not penetrated into gray matter of dorsal horn until E15. The afferent projections became dense and entered the spinal gray matter more deeply at E16 and E17. By E18 the intensity of primary afferent in the deep part of the dorsal horn increased and their branching patterns became more complicated. Some of these primary fibers were also observed to ramify extensively in the superficial laminae. The projection pattern of primary afferent remained unchanged after birth, but the intensity of afferent terminals increased in the superficial laminae. In addition, afferent fiber collaterals that projected into the contralateral dorsal horn were also observed. They were first examined at E16 and mainly originated from the medial and deep part of the dorsal horn. Around birth, the contralateral projections were also found to originate from the lateral part of dorsal horn. Our results indicate that laminar organization of primary afferents in the spinal dorsal horn is established during the late embryonic and early postnatal stages. This organization then undergoes further refinement to match the pattern seen in the adult.