Bursztajn S, Rutkowski M D, Deleo J A
Department of Pathology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, USA.
Neuroscience. 2004;125(1):269-75. doi: 10.1016/j.neuroscience.2004.01.024.
The N-methyl-d-aspartate receptor (NMDAR) has been strongly implicated in mechanisms of persistent pain states. The purpose of the present study was to determine whether the NMDAR NR-1, a key subunit in regulation of NMDAR channel complex is directly contributing to the onset and propagation of peripheral nerve injury-induced allodynia and whether N-methyl-d-aspartate (NMDA) signaling interacts with spinal chemokine (chemotactic cytokines) expression and glial activation. We used genetically engineered male mice that had their normal NR1 gene knocked out and expressed a modified NR1 gene at either normal level (NR1 +/+, wild type) or at a low level (NR1+/-, knock down). Each mouse underwent a peripheral nerve injury in which the lumbar 5 spinal segment (L5) nerve was transected. Mechanical allodynia was assessed using 0.008 and 0.015 g von Frey filaments on days 1, 3, 5, 7, 10, 14, 17 and 21 post-surgery. Mice were killed on day 21 and the harvested L5 spinal cord was analyzed for chemokine expression using RNAse protection assay. In a separate study, glial expression using immunohistochemistry was assessed in both groups 7 days following peripheral nerve injury. The NR1+/- mice displayed decreased mechanical allodynia in comparison to their wild type counterparts. However, even with dramatically impaired NMDA receptor signaling, there was still evidence of tactile hypersensitivity. Using the RPA analysis, we found decreases in mRNA chemokine expression in the NR1+/- mice as compared with NR1+/+ mice. There were no apparent differences in microglial or astrocytic expression between the wild type and knock down mice. These data provide important insights into the cascade of events involving the dynamic interaction between NMDAR function and spinal chemokine and glial production in neuropathic pain states. The results support the findings that chemokine signaling releases glutamate in the spinal cord.
N-甲基-D-天冬氨酸受体（NMDAR）与持续性疼痛状态的机制密切相关。本研究的目的是确定NMDAR通道复合物调节中的关键亚基NMDAR NR-1是否直接导致外周神经损伤引起的异常性疼痛的发作和传播，以及N-甲基-D-天冬氨酸（NMDA）信号传导是否与脊髓趋化因子（趋化细胞因子）表达和神经胶质细胞激活相互作用。我们使用基因工程雄性小鼠，其正常的NR1基因被敲除，并以正常水平（NR1 +/+，野生型）或低水平（NR1+/-，敲低）表达修饰的NR1基因。每只小鼠都经历了外周神经损伤，其中腰5脊髓节段（L5）神经被横断。在手术后第1、3、5、7、10、14、17和21天，使用0.008和0.015 g的von Frey细丝评估机械性异常性疼痛。在第21天处死小鼠，并使用RNA酶保护试验分析收获的L5脊髓中的趋化因子表达。在另一项研究中，在外周神经损伤7天后，对两组小鼠进行免疫组织化学评估神经胶质细胞表达。与野生型对应物相比，NR1+/-小鼠的机械性异常性疼痛有所减轻。然而，即使NMDA受体信号传导明显受损，仍有触觉超敏反应的证据。使用RPA分析，我们发现与NR1 +/+小鼠相比，NR1+/-小鼠中mRNA趋化因子表达降低。野生型和敲低小鼠之间的小胶质细胞或星形胶质细胞表达没有明显差异。这些数据为涉及NMDAR功能与脊髓趋化因子和神经胶质细胞产生之间动态相互作用的一系列事件提供了重要见解。结果支持趋化因子信号传导在脊髓中释放谷氨酸的发现。
