硬脊膜外腔注射辣椒素对大鼠一级传入C纤维的影响——组织化学与电镜观察

THE EFFECT OF EXTRADURAL INJECTION OF CAPSAICIN ON PRIMARY AFFERENT C FIBER OF THE RAT ——A Histochemical and Electron Microscopic Obseration

本文应用组织化学与电镜方法,观察了硬脊膜外腔注射辣椒素(CAP)对成年大鼠一级传入C纤维的影响。经CAP处理后第7天,大鼠脊髓后角Ⅰ～Ⅲ层内P物质(SP)免疫反应性明显减弱,抗氟化钠酸性磷酸酶(FRAP)活性消失或明显减弱,但亮氨酸脑啡肽(LEK)、神经降压素(NT)及5-羟色胺(5-HT)免疫反应性无明显变化。电镜观察发现,CAP处理后脊神经后根内部分无髓神经纤维被破坏,但有髓神经纤维无变化。在给药后48小时的脊髓胶状质(SG)内即可出现变性(DEG)终末,在第5、7、和10天,DEG终末增多,DEG程度加重。部分DEG终末属于Ⅰ型突触球的中央终末,但Ⅱ型突触球的中央终末无DEG征象。以上结果表明,成年大鼠硬脊膜外腔注射CAP亦可有效而特异地损毁一级传入C纤维。此动物模型的建立为选择性地研究C纤维与SG内其它结构之间的超微联系奠定了基础,并在进一步研究C纤维的功能方面具有一定的实用价值。

The effect of extradural injection of capsaicin (CAP) on primary afferent C fiber of the adult rat has been observed by means of histochemical and electron microscopic methods. On the 7th day after CAP treatment, in laminae Ⅰ-Ⅲ of spinal dorsal horn of the rat, substance P (SP) immunoreactivities decreased significantly and fluoride-resistant acid phosphatase(FRAP)activities disappeared or was markedly weakened, but the immunoreactivities of leucine-enkephalin (LEK), neurotensin (NT) and 5-hydroxytryptamine (5-HT) were not effectcd. Electron microscopic results showed that a part of unmyelinatcd nervous fibers in dorsal roots were damaged but myelinated nervous fibers were not after being treated with CAP. There existed degenerate (DEG) terminals in spinal substantia geletinosa (SG) 48 hours after administration of CAP. On the 5th, 7th, 10th day after the administration, DEG terminals increased and the degeneration became severe. It was also found that some DEG terminals were the central terminals of type Ⅰ synaptic glomeruli but the central terminals of type Ⅱ synaptic glomeruli showed no degenertion. The results shown above indicate that extradural injection of CAP to adult rat can also destroy primary afferent C fiber effectively and specifically. Furthermore, the establishment of the experimental animal model has laid a foundation for studying selectively the ultrastructural relation between C fiber and other structures in SG and may have practical value for further investigating the functions of C fiber.