福尔马林致痛大鼠脊髓去甲肾上腺素能神经元及其激活蛋白2α的表达变化

Changes of dopamine-beta-hydroxylase and activator protein-2α expression in spinal cord of formalin-induced rat pain model

目的观察疼痛应激时,脊髓去甲肾上腺素(noradrenaline,NA)能神经元的形态、分布、数量和激活蛋白2α(AP-2α)的表达变化,以探讨NA参与痛觉调制的分子机制。方法应用免疫组化、免疫荧光双标、Western blotting和计算机图像分析方法检测福尔马林诱导致痛模型大鼠脊髓多巴胺-β-羟化酶(dopamine-β-hydroxylase,DBH)和AP-2α的表达变化。结果正常脊髓内NA能神经元主要分布于脊髓前角,模型鼠脊髓前角、中间带和后角均出现大量深染的DBH阳性神经元,3 d时达到高峰,至第7天时DBH阳性神经元数有所下降,但仍高于正常水平。图像分析和统计学分析表明,DBH阳性神经元的数量和染色强度明显增加,与对照组相比具有显著性差异(P<0.05);Western blotting结果证实DBH不同时段的表达变化规律与上述形态学变化一致。AP-2α的表达变化与DBH的表达变化规律具有显著的相似性。免疫荧光双标显示DBH和AP-2α共存于脊髓神经元内。结论在疼痛等应激状态下,脊髓前角NA能神经元内DBH表达明显增强;且中间带和后角新出现大量DBH阳性神经元,推测这些区域内一些神经元可能发生了化学性质的改变,由非NA能神经元转化为NA能神经元;而上述区域内AP-2α表达随着DBH表达增强而增加,提示NA与AP-2α在痛觉的调制和调控中发挥重要作用。

Objective To investigate the changes of dopamine-β-hydroxylase （DBH） and activator protein 2-α （AP-2α） expression in spinal cord under the condition of stress or pain stimulation, so as to explore the mechanism for changes of noradrenergic （NA） neurons in the spinal cord of rat pain model. Methods Immu-nohistochemical staining, double immunofluorescent staining, Western blotting and computing-image analysis system were used to detect the changes of DBH/AP-2α expression in the spinal cord of formalin-induced rat pain model. Results A small number of DBH-positive neurons were sparsely distributed in the ventral horn of the normal spinal cord, while in the formalin-treated group, much more darkly-stained DBH-positive neurons appeared primarily in the ventral horn, intermediate zone, and the dorsal horn, which reached the highest level on day 3 after formalin-injection. The grey value and number of DBH-positive neurons on day 7 after injection began to decrease, but still higher than that in the control group. Compared with control group, the number of noradrenergic neurons in spinal cord of formalin-treated rat was increased significantly, which was also confirmed by Western blotting. Double immunofluorescent staining showed that DBH and AP-2α co-existed in the cells of the spinal cord. The changes of AP-2α expression were similarly to that of DBH in the spinal cord of rat pain model. Conclusion Our results indicated that some non-noradrenergic neurons with different chemical properties might convert into noradrenergic neurons under pain stimulation; noradrenaline may be involved in the formalin-induced pain and behavior regulation; As one of transcription factors, AP-2α may promote the DBH synthesis.