Tao Y X, Li Y Q, Zhao Z Q, Johns R A
Department of Anesthesiology and Critical Care Medicine, Blalock 1415, Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, MD 21287-4965, USA.
Brain Res. 2000 Sep 1;875(1-2):138-43. doi: 10.1016/s0006-8993(00)02608-1.
Recent pharmacological evidence showed that metabotropic glutamate receptors (mGluRs), particularly mGluRs1/5, had a potential role in spinal nociceptive processing. However, previous morphological studies on mGluRs have been limited mainly to their distribution in the spinal cord. In the present study, electron microscopic immunocytochemistry was employed to identify the synaptic relationship of the neurons containing mGluR5, with nociceptive primary afferent and gamma-aminobutyric acid-ergic (GABAergic) terminals in the superficial dorsal horn of the spinal cord. Nociceptive C- and A(delta)-primary afferent terminals selectively labeled with horseradish peroxidase conjugated to wheat-germ agglutinin were in asymmetric synaptic contacts with or in direct apposition to mGluR5 positive dendritic profiles. The double-labeling studies revealed that mGluR5 immunoreactive dendrites also received symmetric synaptic contacts from axon terminals labeled with immunogold particles indicating GABA. The present demonstration of mGluR5 neurons receiving inputs from both nociceptive primary afferents and GABAergic terminals of presumed interneurons further supports the involvement of mGluR5 in the transmission and modulation of nociceptive information in the spinal cord.
近期药理学证据表明，代谢型谷氨酸受体（mGluRs），尤其是mGluRs1/5，在脊髓伤害性信息处理中具有潜在作用。然而，先前关于mGluRs的形态学研究主要局限于其在脊髓中的分布。在本研究中，采用电子显微镜免疫细胞化学方法来确定脊髓背角浅层中含有mGluR5的神经元与伤害性初级传入纤维以及γ-氨基丁酸能（GABA能）终末之间的突触关系。用与麦芽凝集素偶联的辣根过氧化物酶选择性标记的伤害性C类和Aδ类初级传入终末，与mGluR5阳性树突状结构形成不对称突触联系或直接相邻。双重标记研究显示，mGluR5免疫反应性树突也接受来自用免疫金颗粒标记表明为GABA的轴突终末的对称突触联系。本研究证明mGluR5神经元接受来自伤害性初级传入纤维和假定中间神经元的GABA能终末的输入，进一步支持了mGluR5参与脊髓伤害性信息的传递和调制。
