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目的在光镜及电镜下观察大鼠脊髓后角内μ阿片受体（ＭＯＲ）与Ｃ纤维的关系，为进一步揭示阿片镇痛的突触机制提供形态学证据。方法根据辣椒素对初级传入神经中Ｃ纤维的特异性神经毒性，在大鼠蛛网膜下腔注射辣椒素以毁损Ｃ纤维，用免疫组织化学ＡＢＣ法比较脊髓后角内ＭＯＲ免疫反应性的变化；根据西非单叶豆同工凝集素Ｉ－Ｂ４（ｇｒｉｆｏｎｉａｓｉｍｐｌｉｃｉｆｏｌｉａｉｓｏｌｅｃｔｉｎＩ－Ｂ４，Ｉ－Ｂ４）与初级传入Ｃ纤维选择性结合的特性，应用双标（免疫）组织化学电镜技术（ＡＢＣ－纳金法）分别标记脊髓后角内Ｉ－Ｂ４结合位点和ＭＯＲ。结果大鼠蛛网膜下腔注射辣椒素３～７ｄ后，其脊髓后角Ⅰ～Ⅱ层内的ＭＯＲ免疫反应性较对照动物明显减弱；电镜下在大鼠脊髓后角浅层内观察到，ＭＯＲ不仅定位于树突内，也分布在含Ｉ－Ｂ４结合位点的Ｃ纤维终末内。无论在树突内还是在轴突终末内，ＭＯＲ主要分布在非突触部位，仅少量ＭＯＲ与突触前膜和／或突触后膜有关。结论脊髓后角中部分ＭＯＲ来源于辣椒素敏感的Ｃ纤维，外源性吗啡或内源性吗啡样物质如内吗啡肽等ＭＯＲ激动剂在脊髓后角内既可通过突触后（树突内）的ＭＯＲ发挥作用，也可通过突触前（轴突终末内）的ＭＯＲ对Ｃ纤维产生突触前?
Objective To observe the relationship between mu opioid receptors (MOR) and C fibers in the spinal dorsal horn of rats by light microscope and electron microscope, and to provide morphological evidence for further revealing the synaptic mechanism of opioid analgesia. Methods According to the specific neurotoxicity of capsaicin on C fiber in primary afferent nerve, capsaicin was injected into the subarachnoid space of rats to destroy C fibers. Immunohistochemical ABC method was used to compare the changes of MOR immunoreactivity in the posterior horn of spinal cord ; According to the characteristics of selective binding of primary in vitro fibrinolytic enzyme I-B4 (grifoniasimplicifolia isolectin I-B4, I-B4) in West Africa, double-labeled immunohistochemical electron microscopy (ABC- ) Respectively labeled I-B4 binding sites and MOR in the dorsal horn of the spinal cord. Results After 3 ~ 7 days of capsaicin injection into subarachnoid space, MOR immunoreactivity in Ⅰ ~ Ⅱ layer of spinal dorsal horn was significantly weaker than that in control animals. Electron microscopy showed that MOR Not only located within the dendrites, but also distributed in the I-B4 binding sites within the C fiber terminal. MOR is predominantly located in non-synaptic sites, both within the dendrites and in the terminal axon, with only a small amount of MOR associated with presynaptic and / or postsynaptic membranes. CONCLUSIONS: MOR in the dorsal horn of the spinal cord is derived from capsaicin-sensitive C fibers. Exogenous morphine or endogenous morphine-like MOR agonists such as endomorphin may act both in the posterior horn of the spinal cord via postsynaptic (dendritic ) Of the MOR play a role, but also through pre-synaptic (intra-axon terminal MOR) C-fiber pre-synaptic?