Ma Q P, Hargreaves R J
Department of Pharmacology, Merck Sharp & Dohme Research Laboratories, Neuroscience Research Centre, Terlings Park, CM20 2QR, Harlow, UK.
Neuroscience. 2000;101(3):699-707. doi: 10.1016/s0306-4522(00)00419-x.
In the present study we have used immunohistochemical staining and retrograde tracing techniques to investigate the relationship between the N-methyl-D-aspartate receptor NR2B subunits and small-diameter primary afferent dorsal root ganglion neurons that give rise to the sciatic nerve fibers. Three days after an intra-sciatic nerve injection of tetramethyl rhodamine isothiocyanate-conjugated wheat germ agglutinin which labels small-diameter primary afferents, many NR2B and wheat germ agglutinin-double-labeled cells ( approximately 70% of wheat germ agglutinin-labeled neurons) were observed in the L5 dorsal root ganglia. Three days after an intra-sciatic nerve injection of fluorescein isothiocyanate-conjugated Bandeiraea simplicifolia agglutinin isolectin B4 which labels predominantly non-peptidergic C-fiber primary afferents, NR2B and Bandeiraea simplicifolia agglutinin isolectin B4 double-labeled neurons ( approximately 90% of Bandeiraea simplicifolia agglutinin isolectin B4-labeled neurons) were also observed in the L5 dorsal root ganglion. Three days after an intra-sciatic nerve injection of fluorescein isothiocyanate-conjugated cholera toxin B subunit, only approximately 40% of cholera toxin B subunit-labeled neurons were NR2B positive and those labeled neurons tended to be small-sized. When calcitonin gene-related peptide and NR2B were labeled by a double immunofluorescent staining technique, we found that the majority of calcitonin gene-related peptide-positive neurons was NR2B immunoreactive (>90% of calcitonin gene-related peptide-positive neurons, and approximately 60% of NR2B-positive neurons) as well. Size frequency analysis also demonstrated that NR2B subunits were predominantly localized on the small and medium-sized neurons. These results suggest that NR2B subunits are predominantly expressed on small diameter primary afferents, and these NR2B containing N-methyl-D-aspartate receptors may play a role in the modulation of neurotransmitter release from primary afferent terminals.
在本研究中，我们使用免疫组织化学染色和逆行追踪技术来研究N-甲基-D-天冬氨酸受体NR2B亚基与支配坐骨神经纤维的小直径初级传入背根神经节神经元之间的关系。在坐骨神经内注射异硫氰酸四甲基罗丹明缀合的麦胚凝集素（标记小直径初级传入纤维）三天后，在L5背根神经节中观察到许多NR2B和麦胚凝集素双标记细胞（约占麦胚凝集素标记神经元的70%）。在坐骨神经内注射异硫氰酸荧光素缀合的单叶豆凝集素isolectin B4（主要标记非肽能C纤维初级传入纤维）三天后，在L5背根神经节中也观察到NR2B和单叶豆凝集素isolectin B4双标记神经元（约占单叶豆凝集素isolectin B4标记神经元的90%）。在坐骨神经内注射异硫氰酸荧光素缀合的霍乱毒素B亚基三天后，只有约40%的霍乱毒素B亚基标记神经元为NR2B阳性，且这些标记神经元往往体积较小。当用双重免疫荧光染色技术标记降钙素基因相关肽和NR2B时，我们发现大多数降钙素基因相关肽阳性神经元也具有NR2B免疫反应性（>90%的降钙素基因相关肽阳性神经元，约60%的NR2B阳性神经元）。大小频率分析还表明，NR2B亚基主要定位于中小直径神经元。这些结果表明，NR2B亚基主要在小直径初级传入纤维上表达，且这些含有NR2B的N-甲基-D-天冬氨酸受体可能在调节初级传入终末神经递质释放中发挥作用。
