大鼠脊髓背角内第5型代谢型谷氨酸受体免疫组织化学特征

The Immunohistochemical Features of Metabotropic Glutamate Receptor Type 5 in the Rat Spinal Dorsal Horn

应用免疫组织化学方法在光镜下观察到 ,大鼠脊髓内第 5型代谢型谷氨酸受体 (m Glu R5 )主要分布在背角 ～ 层内 ;行单侧背根 (L1～ L6 )切断术后 ,未见术侧 m Glu R5免疫反应性明显变化 ;脊神经节内仅见极少数神经元呈 m Glu R5免疫反应弱阳性。由此提示 ,脊髓背角内 m Glu R5的主要来源为非一级传入神经元。免疫电镜研究显示 ,在脊髓背角浅层内 ,m Glu R5主要定位在部分神经元胞体和大量树突内 ,并常见部分含 m Glu R5的树突与具有一级传入C纤维终末形态特征的轴突终末构成突触小球。 m Glu R5在脊髓背角浅层内的超微定位特征表明 ,脊髓背角内的m Glu R5可能主要作为突触后受体介导或调节谷氨酸传递一级感觉 (包括痛觉 )

By using immunohistochemical technique, it was observed under light microscope that in the rat spinal cord the metabotropic glutamate receptor type 5 (mGluR5) was mainly distributed in layer Ⅰ to Ⅲ of the dorsal horn. In the rats with unilateral posterior rhizotomy at lumbar level (L1-L6), no obvious change of mGluR5 immunoreactivity was seen in the dorsal horn ipsilateral to the rhizotomy compared with that in the intact side. The immunostaining of dorsal ganglion showed that few of ganglionic neurons were weakly positive for mGluR5. It was suggested that the majority of mGluR5 in the spinal dorsal horn originates from non primary afferent neurons. Immunoelectron microscopic examination revealed that mGluR5 was prominently located in some neuronal somata and a lot of dendrites within the superficial layers of the spinal dorsal horn. Some dendrites containing mGluR5 constituted synaptic glomeruli with the terminals exhibiting the morphological characteristics of primary afferent C fiber. The ultrastructural features indicated that mGluR5 in the dorsal horn of the spinal cord may prominently work as a postsynaptical receptor to mediate or modulate the function of glutamate in the primary sensory transmission, including the nociceptive transmission.