NMDA受体NRl亚基对神经病理性疼痛大鼠脊髓组织中谷氨酸及其转运体GLT-1的影响

Mechanism and effects of NMDA receptor NR1 subunit on chronic constriction injury-induced neu- ropathic pain in a rat model

目的观察鞘内注射N-甲基-D-天门冬氨酸（NMDA）受体NR1亚基激动和拮抗剂对坐骨神经慢性缩窄性损伤（CCI）模型大鼠行为学、痛阈以及脊髓组织中谷氨酸转运体-1（GLT-1）表达的影响，探讨NMDA受体NR1亚基在神经病理性疼痛中的作用及机制。方法160只SD大鼠按随机数字表法分为4组，每组40只。假手术组（Sham组）和CCI组每只鞘内注射10μl生理盐水，NMDA受体激动剂组（NMDA组）坐骨神经结扎前3d每只鞘内注射10μl（10nm01）NMDA，NMDA受体NRl亚基拮抗剂组（Humanin，HN组）坐骨神经结扎前3d鞘内注射10u1（10nm01）Humanin。Sham组仅暴露坐骨神经而不结扎，其余各组均行右侧坐骨神经分支结扎术。术后l、3、5、7、10、14d分别观察大鼠行为学变化，测定各组大鼠的热痛阈、机械性痛阈；Westernblot法检测脊髓组织中GLT-1表达，ELISA法测定组织中谷氨酸含量变化。结果与Sham组相比，术后各观察点CCI组大鼠逐渐出现术侧后肢足趾并拢、足外翻以及反复舔舐术侧后肢等症状，且术后各观察点机械刺激缩爪阈值（PwT）和辐射热刺激缩爪潜伏期（PwL）评分明显降低，第7天达最低水平；同时脊髓组织中谷氨酸含量增加而其转运体GLT-1表达降低（P〈0．05）。与CCI组比较，NMDA组术后各观察点PWT、PWL、谷氨酸转运体GLT-1进一步降低（P〈0．05），而脊髓组织中谷氨酸含量增高；而与CCI组比较，Humanin组术后各观察点PWT、PWL、谷氨酸转运体GLT-1明显增高（P〈0．05），脊髓组织中谷氨酸含量则明显降低（P〈0．05）。结论NMDA受体NRl亚基参与神经病理性疼痛的调节，抑制MDA受体NR1亚基可以通过降低谷氨酸及其转运体GLT-1的表达缓解坐骨神经结扎引起的神经病理性疼痛。

Objective To investigate the effects of intrathecal injection （IT） of agonist and antago- nist of N-methyl-D-aspartate receptor subunit 1 （ NMDA NR1 ） on pain threshold and spinal levels of gluta- mate and glutamate transporter-1 （ GLT-1 ） in rat model of chronic constriction injury （CCI） induced neuropathic pain. Methods Sprague-Dawley （SD） rats were randomly divided into 4 groups （ Sham, CCI, NM- DA, and Humanin）. The CCI model was established by right sciatic nerve constriction. The thermal and mechanical thresholds were assessed by paw withdrawal latency （PWL） to radiant heat and yon Frey fila- ments at l , 3, 5, 7, 10 and 14 days as well as behavior after CCI. The NMDA and Humanin groups were administered intrathecally for 3 days before surgery. Spinal expression of GLT-1 assessed by Weston blotting and levels of glutamate were measured by enzyme-linked immunosorbent assay （ELISA）. Results Com- pared to Sham group, the rats in CCI group gradually appeared the symptoms of toe close together, foot valgus and repeated licking to the operative side of the hind legs after surgery, and the paw withdrawal threshold （PWT）, and PWL were greatly decreased, reaching the lowest level on the 7th day. Meanwhile, the glutamate content was increased, and the GLT-1 expression was decreased in spinal cord （P 〈 0. 05）. Com- pared to CCI group, the rats in NMDA group were observed with further decrease in PWT, PWL and GLT- 1 expressions at all observed timepoints （ P 〈 0. 05 ）, but increase in glutamate content in spine cord （P 〈 0. 05）. Compared to CCI group, the rats in Humanin group were observed with increase in PWT, PWL and GLT-1 expressions at all observed timepoint （ P 〈 0. 05 ）, but decrease in glutamate content in spine cord （P 〈 0. 05）. Conclusions NMDA receptor NR1 subunit participated in regulating neuropathic pain, in- hibiting NMDA receptor NR1 subunit can alleviate neuropathic pain by down - regulating of glutamate and GLT-1.