Furuyama T, Kiyama H, Sato K, Park H T, Maeno H, Takagi H, Tohyama M
Department of Anatomy and Neuroscience, Osaka University Medical School, Japan.
Brain Res Mol Brain Res. 1993 Apr;18(1-2):141-51. doi: 10.1016/0169-328x(93)90183-p.
The present study attempted to explore the gene expression of the subunits (GluR1-4) of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type receptor, subunit (GluR5) of kainic acid (KA)-type receptor, NR1 [a subunit of N-methyl-D-aspartate (NMDA) receptors] and the possible glutamate-binding subunit of an NMDA receptor complex in the dorsal horn of the rat spinal cords using in situ hybridization histochemistry. These results were compared with those of the spinal motor neurons. Expression of the subunits of the AMPA-type receptor was also examined at the protein level using immunocytochemistry, with reference to the motor neurons. Although all the four subunits of the AMPA-type receptor were expressed throughout the dorsal horn, the pattern of expression was different according to the dorsal horn region and to the subunits. GluR2 showed the strongest expression in the dorsal horn. Huge numbers of strongly labelled cells formed a dense collection in lamina II and superficial parts of lamina III. Many neurons in lamina II and superficial parts of lamina III expressed GluR1 moderately. Scattered neurons moderately expressing GluR3 were also seen in these regions, while the expression of GluR4 was very low. Labelling of the dorsal horn neurons by the GluR5 probe was low, and NR1 probe and a glutamate-binding subunit of an NMDA receptor complex probe labelled them diffusely with low to moderate intensity. These findings show a close relationship between the glutamergic nociceptive primary afferent system and AMPA-type receptors in which GluR2 is especially highly expressed. The present study further showed that the expression pattern of the glutamate receptors in the spinal sensory neurons differs considerably from that of spinal motor neurons. Motor neurons very strongly express GluR3 and 4, while the expression of GluR2 and GluR1 is moderate and low, respectively. Expression of GluR5 is also low in the motor neurons. However, expression of NR1 and the glutamate-binding subunit of an NMDA receptor complex is very strong. These findings indicate that the subunit composition of the AMPA-type receptors regulating motor neurons is different from that of the AMPA-type receptors in the spinal sensory neurons, and that there are at least two kinds of glutamergic systems which regulate motor neurons: via AMPA-type receptors and via NMDA receptors.
本研究试图利用原位杂交组织化学技术，探究大鼠脊髓背角中α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）型受体亚基（GluR1 - 4）、海人酸（KA）型受体亚基（GluR5）、NR1 [N-甲基-D-天冬氨酸（NMDA）受体的一个亚基] 以及NMDA受体复合物中可能的谷氨酸结合亚基的基因表达情况。将这些结果与脊髓运动神经元的结果进行比较。还运用免疫细胞化学技术，以运动神经元为参照，在蛋白质水平检测AMPA型受体亚基的表达。尽管AMPA型受体的所有四个亚基在整个背角均有表达，但根据背角区域和亚基的不同，表达模式也有所差异。GluR2在背角中的表达最强。大量强阳性标记细胞在Ⅱ层和Ⅲ层浅层形成密集聚集。Ⅱ层和Ⅲ层浅层的许多神经元适度表达GluR1。在这些区域也可见到散在的适度表达GluR3的神经元，而GluR4的表达非常低。GluR5探针标记背角神经元的程度较低，NR1探针和NMDA受体复合物的谷氨酸结合亚基探针以低至中等强度弥散性地标记它们。这些发现表明谷氨酸能伤害性初级传入系统与AMPA型受体之间存在密切关系，其中GluR2尤其高表达。本研究进一步表明，脊髓感觉神经元中谷氨酸受体的表达模式与脊髓运动神经元的表达模式有很大差异。运动神经元非常强烈地表达GluR3和4，而GluR2和GluR1的表达分别为中等和低水平。GluR5在运动神经元中的表达也很低。然而，NR1和NMDA受体复合物的谷氨酸结合亚基的表达非常强。这些发现表明，调节运动神经元的AMPA型受体的亚基组成与脊髓感觉神经元中的AMPA型受体不同，并且至少有两种谷氨酸能系统调节运动神经元：通过AMPA型受体和通过NMDA受体。
