下行纤维5-HT在猫背根节切除后脊髓背角的表达

5-HT Descending Expressing in the Dorsal Horn of Cat Spinal Cord after Deafferentation

目的观察猫脊髓背根神经节切除后下行纤维5-羟色胺(5-HT)在脊髓背角内的表达变化及5-HT异类终末,探讨其在脊髓背根节切除后的代偿意义。方法 10只成年雄性猫,在腹腔内注射麻醉下行腰1到骶2(L1~S2)单侧背根节切除术,建立猫腰骶背根节全切模型,术后分为急性组5只,存活2周,慢性组5只,存活2个月,实验结束时,动物腹腔内麻醉,开胸并心内灌注固定处理,取腰6(L6)节段脊髓,采用免疫组化染色方法检测手术侧和对侧脊髓背角、Ⅱ板层内5-HT的表达,电镜下观察5-HT异类终末。结果光镜下5-HT阳性染色主要分布于脊髓背角,Ⅱ板层区域较突出,呈细颗粒状和线条状。急性组手术侧与对侧非手术侧阳性染色无明显差异,慢性组两侧阳性染色差异明显,手术侧强于对照侧。电镜下,在慢性组手术侧脊髓Ⅱ板层中,观察到简单终末,发现了5-HT阳性非典型复合终末(ACT),它们较小,外观上呈圆形或椭圆形,多与两个突触后成分形成联系,突触活性带较平直或向外凸,突触内多含均匀清亮小泡或致密核心小泡。结论 5-HT在猫脊髓腰骶背根节切除后主要出现在脊髓背角,Ⅱ板层表达突出,5-HT阳性ACT可能是脊髓背根节全切后的一种下行纤维代偿终末。

Objective To investigate the Serotonin(5-HT) expression in dorsal horn of cat spinal cord and the atypical complex terminal(ACT) after complete dorsal rhizotomy.Methods Ten male adult cats were divided into 2 groups after carrying out the complete dorsal rhizotomy: acute group,which survived 2 weeks;chronic group,which survived 2 months.At maturity,all cats were perfused after anaesthesia,the L6 segments of the spinal cord were removed and prepared for light and electron microscopy of 5-HT immunohistochemistry for observing of ACT.Results 5-HT immuno-reactivity was demonstrated in dorsal horn especially in laminal Ⅱ both in operation and control sides in acute group.In chronic group,the 5-HT positive stain in operation sides was stronger than that of control sides.The immuno-positive ACTs were founded in the lamina Ⅱ of chronic operation side beside some 5-HT immuno-positive simple terminals;they were round or ellipse in shape and usually form flat or convex two synapse with two post-compounds.ACTs mainly contain clear or dense core vesicles.Conclusion The descending 5-HT express in operation side after complete dorsal rhizotomy is mainly on the in lamina Ⅱ.The 5-HT immuno-positive ACT may imply the mechanism of descending spinal cord plasticity.