Conte D, Legg E D, McCourt A C, Silajdzic E, Nagy G G, Maxwell D J
Spinal Cord Group, West Medical Building, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
Neuroscience. 2005;134(1):165-73. doi: 10.1016/j.neuroscience.2005.02.013.
Recent evidence suggests that serotonin has pronociceptive actions in the spinal cord when it acts through 5-hydroxytryptamine (5-HT)(3) receptors. Cells and axon terminals which are concentrated in the superficial dorsal horn possess this receptor. We performed a series of immunocytochemical studies with an antibody raised against the 5-HT(3A) subunit in order to address the following questions: 1) Are axons that possess 5-HT(3) receptors excitatory? 2) Are 5-HT(3) receptors present on terminals of myelinated primary afferents? 3) What is the chemical nature of dorsal horn cells that possess 5-HT(3) receptors? 4) Do axons that possess 5-HT(3) receptors target lamina I projection cells? Approximately 45% of 5-HT(3A) immunoreactive boutons were immunoreactive for the vesicular glutamate transporter 2 and almost 80% formed synapse-like associations with GluR2 subunits of the AMPA receptor therefore it is principally glutamatergic axons that possess the receptor. Immunoreactivity was not present on myelinated primary afferent axons labeled with the B-subunit of cholera toxin or those containing the vesicular glutamate transporter 1. Calbindin (which is associated with excitatory interneurons) was found in 44% of 5-HT(3A) immunoreactive cells but other markers for inhibitory and excitatory cells were not present. Lamina I projection cells that possessed the neurokinin-1 receptor were associated with 5-HT(3A) axons but the density of contacts on individual neurons varied considerably. The results suggest that 5-HT(3) receptors are present principally on terminals of excitatory axons, and at least some of these originate from dorsal horn interneurons. The relationship between lamina I projection cells and axons possessing the 5-HT(3) receptor indicates that this receptor has an important role in regulation of ascending nociceptive information.
最近有证据表明，血清素通过5-羟色胺（5-HT）（3）受体在脊髓中发挥促痛作用。集中在浅表背角的细胞和轴突终末具有这种受体。我们用针对5-HT（3A）亚基产生的抗体进行了一系列免疫细胞化学研究，以解决以下问题：1）具有5-HT（3）受体的轴突是否具有兴奋性？2）有髓初级传入纤维的终末是否存在5-HT（3）受体？3）具有5-HT（3）受体的背角细胞的化学性质是什么？4）具有5-HT（3）受体的轴突是否靶向I层投射细胞？大约45%的5-HT（3A）免疫反应性终扣对囊泡谷氨酸转运体2呈免疫反应性，近80%与AMPA受体的GluR2亚基形成突触样联系，因此主要是谷氨酸能轴突具有该受体。用霍乱毒素B亚基标记的有髓初级传入轴突或含有囊泡谷氨酸转运体1的轴突上不存在免疫反应性。在44%的5-HT（3A）免疫反应性细胞中发现了钙结合蛋白（与兴奋性中间神经元相关），但不存在抑制性和兴奋性细胞的其他标记物。具有神经激肽-1受体的I层投射细胞与5-HT（3A）轴突相关，但单个神经元上的接触密度差异很大。结果表明，5-HT（3）受体主要存在于兴奋性轴突的终末，其中至少一些起源于背角中间神经元。I层投射细胞与具有5-HT（3）受体的轴突之间的关系表明，该受体在调节上行伤害性信息方面具有重要作用。
