大鼠脊髓背角内吗啡肽2的表达与带状疱疹后神经痛的相关性分析

Correlation Analysis of the Expression of Endomorphin-2 in Spinal Cord and Postherpetic Neuralgia in Rats

目的观察带状疱疹后神经痛(postherpetic neuralgia,PHN)大鼠脊髓背角内吗啡肽2(endomorphin-2,EM2)的表达变化及其与痛行为的关联性。方法成年雄性SD大鼠随机分为PHN组、假处理组和对照组。PHN组在大鼠足底皮下注入水痘带状疱疹病毒造模,假处理组在足底注射等量非洲绿猴肾细胞(Vero细胞)悬液,对照组未经任何处理。每组在造模前和造模后6、10、14、20、28、34、42天进行痛行为检测,然后利用高效液相色谱法(high performance liquid chromatography,HPLC)和免疫荧光组织化学染色检测脊髓EM2的表达变化。在PHN大鼠痛觉阈值最低的时间点进行行为药理学检测,即经脊髓鞘内注入不同剂量的吗啡、EM2和μ型阿片受体(mu-opioid receptor,MOR)拮抗剂β-富纳曲胺(β-funaltrexamine,β-FNA),记录痛觉阈值的变化。结果与假处理组和对照组比较,PHN组在造模后10天痛觉阈值显著降低,28天时痛觉阈值达到最低点(P<0.05),PHN组脊髓背角EM2表达量和染色密度显著减少(P<0.05)。EM2的表达减少与痛觉阈值的降低呈显著正相关(r=0.958,P<0.001);PHN组鞘内给予EM2镇痛作用比吗啡强,而鞘内给予β-FNA加深疼痛。结论本实验证实脊髓背角EM2的表达下调导致PHN大鼠痛敏状态的形成,从全新的角度诠释PHN形成的病理生理机制,为诊疗PHN提供新的理论依据。

Objective To observe the expression of endomorphin-2(EM2)in spinal dorsal horn of postherpetic neuralgia(PHN)rat model and explore its relationship with pain behavior.Methods Adult male SD rats were randomly divided into PHN group,sham operation group and control group.While varicella zoster virus were subcutaneously injected into the paw of rats in PHN group,sham operation group were injected with the same amount of Verda Reno(Vero cell)suspension,the control group were not received any treatment.The pain behavior of each group was detected before modeling and 6,10,14,20,28,34,42 days after modeling,and then changes of EM2 expression in spinal cord were detected by high performance liquid chromatography(HPLC)and immunofluorescence histochemical staining.Morphin,EM2 and the mu-opioid receptor(MOR)antagonistβ-funaltrexamine(β-FNA)were injected intrathecally when the threshold of paw withdrawal of PHN rats reached the lowest value,and the changes of pain threshold was recorded.Results Compared with the sham operation group and control group,the pain threshold of PHN group were significantly decreased on the 10 th day after injection and reached the lowest value on the 28 th day after modeling(P<0.05).In PHN group,the staining density and the expression of EM2 in spinal dorsal horn were significantly decreased(P<0.05).The decrease of EM2 expression level in PHN group was positively correlated with the decrease of pain threshold(r=0.958,P<0.001).The analgesic effect of intrathecal injection of EM2 was stronger than that of morphine in PHN group,however,intrathecal injection of β-FNA deepened pain.Conclusion The experiments confirm that the down-regulation of spinal EM2 experssion leads to the formation of pain sensitivity in PHN rats,which interpret the pathophysiological mechanism of PHN formation from a new perspective and provide a new theoretical basis for the diagnosis and treatment of PHN.