大鼠脊髓内囊泡膜谷氨酸转运体1和囊泡膜谷氨酸转运体2阳性纤维和终末在生后发育中的分布和表达变化

Distribution and expression changes of the vesicular glutamate transporter 1 and vesicular glutamate transporter 2 immunopositive fibers and terminals in the postnatal development of the spinal cord of rat

目的探讨囊泡膜谷氨酸转运体1(VGLUT1)和VGLUT2阳性纤维和终末在生后第0天(P0)至第22天(P22)大鼠脊髓内的分布情况和表达变化。方法对生后发育P0~P22大鼠的颈膨大和腰膨大部位,进行VGLUT1和VGLUT2免疫组织化学染色。结果 P0~P22大鼠颈膨大和腰膨大脊髓内均可观察到VGLUT1和VGLUT2阳性纤维和终末,但未观察到胞体样结构。VGLUT1和VGLUT2阳性纤维和终末的分布呈现明显的互补分布,尤其是以脊髓后角更加明显。其中,VGLUT1阳性纤维和终末在P0主要见于颈膨大和腰膨大脊髓后角Ⅲ~Ⅴ层,中间部和前角很微弱。脊髓发育至P3,不仅Ⅲ~Ⅴ层VGLUT1的表达进一步增强,且向外侧部扩展,并在后角基底部Ⅵ层和前角的外侧部(Ⅸ层)也可观察到较强的VGLUT1阳性纤维,呈现一条明显由背内向腹外的带状分布趋势。P7时此带状分布更加明显,并随着发育逐渐向内、外扩展,至P22时已广泛分布于除Ⅱ层之外的整个脊髓。而VGLUT2阳性纤维和终末在P0时即密集出现于脊髓后角Ⅰ~Ⅱ层以及前角的外侧边缘区域;之后随着发育,VGLUT2阳性纤维和终末的分布模式并未发生明显改变,但其密度逐渐有所增加,特别是Ⅰ~Ⅱ层内VGLUT2阳性产物的表达尤为明显。另外,在脊髓白质后索内可见VGLUT1阳性皮质脊髓后束纤维由颈髓(P3)逐渐下降至腰髓(P7)的发育过程。结论 VGLUT1和VGLUT2阳性纤维和终末在脊髓发育过程中呈现明显不同,且表现出互补分布的特点,这对于进一步理解VGLUT1和VGLUT2在脊髓生后发育过程中不同功能特点可能有意义。

Objective To explore different distribution and expression changes of vesicular glutamate transporter 1 （VGLUT1） and YGLUT2 immunopositive （-ip） fibers and terminals in the spinal cord of postnatal 0 day （P0）-22 days （P22） rats. Methods Immunohistochemical staining was performed for the VGLUT1 and VGLUT2 in the cervical and lumber enlargements of P0-P22 rats. Results VGLUTI-and VGLUT2-ip fibers and terminals were observed in the cervical and lumber enlargements of the spinal cord in the postnatal P0-P22 rats but not soma. These fibers and termianls showed a typical complementary distribution pattern, especially in the posterior horn of the spinal cord. On P0, VGLUTI-ip fibersand terminals were mainly observed in the laminae III-V of the cervical and lumber enlargements, with a weak expression in the intermediate gray and anterior horn. From P3, the expression of VGLUT1 was increased in the laminae III-V and extended to the lateral, and the VGLUTI-ip profiles were detected in the basal part of posterior horn （lamina Wl ） and the lateral part of the anterior horn （lamina IV ） . An obvious trend of the belt distribution from the dorsomedial to ventrolateral side was observed. It was more obvious at P7, and expanded gradually to the medial and lateral side of spinal grey with development. On P22, VGLUTI-ip profiles were observed on almost whole spinal gray, except for a weak expression in the lamina 11 . On the contrary, VGLUT2-ip fibers and terminals were observed to distribute densely in laminae I-II and the margins of the anterior horn from P0. In the other areas of the spinal cord, medium density of VGLUT2-ip fibers and terminals were distributed much more evenly. With the development, the distribution pattern of VGLUT2-ip fibers and terminals were not changed greatly, although its density was gradually increased. On the other hand, in the posterior cord of the spinal white matter, the developmental process of the VGLUT1 positive eorticospinal posterior tract gradually went down from the cervical （P3） to the lumbar cord （P7）. Conclusion The distribution of VGLUTI-and VGLUT2-ip fibers and terminals is largely different in the postnatal developing cervical and lumber spinal cord of rats, showing an obvious complementary pattern. This may be important for us to understand the difference of their functional involvement during the postnatal development of the spinal cord.