鞘内预注射L-NAME对神经性疼痛大鼠脊髓背角降钙素基因相关肽表达的影响

Effect of pre-emptive intrathecal administration of L-NAME on CGRP expression in spinal dorsal horn in a rat model of neuropathic pain

目的 观察鞘内预注射NG-硝基-L-精氨酸-甲基酯(L-NAME)对结扎坐骨神经所致神经性疼痛大鼠脊髓背角降钙素基因相关肽(CGRP)表达的影响。方法 选择鞘内置管后无神经损伤症状的SD雌性大鼠96只,随机分为4组,每组24只。A组:假手术组;B组:坐骨神经结扎组;C组:假手术前15 min鞘内注射L-NAME 10 μl(250 μg);D组:坐骨神经结扎前15 min鞘内注射L-NAME 10 μl(250 μg)。各组分别在术后第1、4、7和14天随机处死6只大鼠。采用免疫组织化学方法观察各组大鼠结扎侧脊髓背角CGRP的表达。结果 与A组比较,B组、D组大鼠结扎侧脊髓背角CGRP表达在术后第4、7和14天明显升高(P<0.05),C组差异无显著性。与C组比较,D组大鼠结扎侧脊髓背角CGRP表达在术后第4、7和14天明显升高(P<0.05)。而D组大鼠结扎侧脊髓背角内的CGRP表达与B组比较,差异无显著性(P>0.05)。结论 鞘内预注射L-NAME不能抑制周围神经损伤所诱导的脊髓背角CGRP表达,提示一氧化氮介导神经性疼痛的作用不是通过促进CGRP释放实现的。

Objective To investigate the effect of pre-emptive intrathecal (IT) administration of L-NAME, a non-selective nitric oxide synthase (NOS) inhibitor on calcitonin gene-related peptide (CGRP) expression in the dorsal horn of spinal cord in a rat model of neuropathic pain. Methods Ninety-six female adult SD rats weighing 220-310 g were randomly divided into four groups with 24 animals in each group : group A received IT 0.9% NaCl 15 min before sham operation; group B received IT 0.9% NaCl 15 min before right sciatic nerve ligation; group C received IT L-NAME 250 mg in 10μl 15 min before sham operation and group D received IT L-NAME 250 μg in 10 μl15 min before sciatic nerve ligation. The animals were anesthetized with intraperitoneal pentobarbital 50 mg·kg-1. A PE-10 catheter was placed in subarachnoid space with the tip of the catheter reaching the lumbar enlargement region. The animals were allowed to recover for 3-4 days and only those waking normally were used in the study. Right sciatic nerve was exposed and four loose ligatures were placed on the sciatic nerve according to the method described by Bennet. In sham operation the sciatic nerve was exposed but not ligated. The animals were sacrificed on the 1 st, 4 th, 7 th and 14 th day after operation. The lumbar segment of spinal cord was immediately removed. The CGRP expression in the ligated-side dorsal horn was assessed with immuno-histochemistry technique. Results In group B and D CGRP expression in the ligated side dorsal horn was significantly increased on the 4th, 7th and 14th day after operation as compared with that in group A. There was no significant difference in the CGRP expression in the ligated side dorsal horn between group A and C as well as between B and D. Conclusion Pre-emptive IT administration of L-NAME cannot inhibit the increase in CGRP expression in dorsal horn induced by peripheral nerve injury, suggesting that the neuropathic pain mediated by NO is not related to the release of calcitonin gene-related peptide.