神经示踪定位SD大鼠长下行脊髓固有神经元胞体及其轴突投射的解剖位置

Nerve tracing the anatomical location of long descending propriospinal neurons and their axonal projections in SD rats

目的利用神经示踪技术探讨SD大鼠长下行脊髓固有神经元及其轴突投射的解剖位置。方法将荧光金(FG)注射入第1腰髓(L_(1))节段逆行标记大鼠下行脊髓固有神经元(DPNs)胞体;将顺行神经示踪剂生物素葡聚糖胺(BDA)注射到脊髓第3和第4颈髓处标记此处的DPNs胞体及其长下行脊髓固有束(LDPT)。固定取材与切片染色后,检测FG标记的DPNs胞体在颈髓节段的分布和BDA顺行标记的LDPT投射到胸腰髓节段的情况。结果FG逆行标记的DPNs胞体主要分布在颈髓的VII和VIII板层。BDA标记的LDPT主要走行在脊髓白质的两侧和腹侧,其中第8和第10胸髓(T8和T10)白质内BDA标记的LDPT轴突指数[分别为(61.19±8.61)%和(35.55±7.30)%]显著性高于L_(1)的(12.05±10.04)%,差异有统计学意义(P<0.05)。这些被标记的LDPT轴突主要投射支配胸腰髓IV-X板层的神经元,其中T8和T10脊髓灰质内BDA标记的轴突数(分别为41.47±20.33和24.87±15.80)显著性多于L_(1)的(7.40±4.88),差异有统计学意义(P<0.05)。结论 SD大鼠的长下行脊髓固有神经元胞体主要集中分布在颈膨大脊髓灰质的Ⅶ和Ⅷ板层。长下行脊髓固有束轴突可投射支配胸腰髓IV-X板层的神经元。

Objective The study investigated the anatomical location of long descending propriospinal neurons and theiraxonal projections in SD rats by anterograde and retrograde nerve tracing.Methods The retrograde nerve tracer Fluoro-Gold(FG)was injected into the 1 st lumbar(L_(1))segment of spinal cord by stereotaxic apparatus to label the somas of the de-scending propriospinal neurons(DPNs)in rats. The anterograde tracer biotin dextran amine(BDA)was injected into thecervical enlargement(C3-C4)of spinal cord to mark the propriospinal neurons and their long descending propriospinal tract(LDPT)of spinal cord. After 7 days and 14 days,the samples were fixed and sectioned,and then performed the immunoflu-orescence histochemical staining. The distribution and quantity of FG-labeled DPNs in the gray matter of the cervical spinalcord were detected under the fluorescence confocal microscope,and the axonal number and their innervation of BDA-labeledLPDT projecting to the thoracolumbar segment of spinal cord were also detected.ResultsThe FG-labeled DPNs were main-ly distributed in the Ⅶ and Ⅷ lamina of the cervical spinal cord,a few FG-labeled DPNs were also found in III-VI and Xlaminas. The result of statistical analysis showed that there was no statistical difference in the number of DPNs co-labeled byFG and PI among the C_(1)-C_(6) segments of spinal cord. The BDA-labeled LDPT was mainly distributed in both sides and ventralside of the white matter of spinal cord,and the axonal index of BDA-labeled LDPT in the white matter of T8 and T10 spinalcord[(61.19±8.61)% and(35.55±7.30)%,respectively]was significantly higher than that in the L_(1) spinal cord(12.05±10.04)%(P<0.05). The BDA-labeled LDPT axons mainly project to the thoracic spinal cord and innervate the neurons inthe IV-X laminas,and a few BDA-labeled axons also project to L_(1) spinal cord and innervate these neurons in the VII-IX lam-inas of L_(1) spinal cord. The result of statistical analysis showed that the number of BDA-labeled axons in the gray matter of T8 and T10 spinal cord(41.47±20.33 and 24.87±15.80,respectively)was significantly higher than that in the L_(1) spinal cord(7.40±4.88)(P<0.05).ConclusionThe somas of the Long descending propriospinal neurons were mainly distributed in the Ⅶ and Ⅷ lamina of spinal gray matter of the cervical enlargement in SD rats. The long descending propriospinal tractcan project to the thoracolumbar segments and innervate the neurons in the IV-X laminas of spinal cord.