下丘脑室旁核Epac蛋白在大鼠炎性痛调节过程中的作用及其机制研究

摘要

Aim To investigate the role and mecha-nism of exchange protein directly activated by cAMP (Epac) protein in the paraventricular nucleus(PVN) of the hypothalamus in the development of inflammatory pain in rats. Methods Adult SD male rats were cho-sen to establish the model of inflammatory pain through subcutaneous injection of complete Freund's adjuvant(CFA) on the center of left hind foot. Western blot was used to detect the changes of the expression of Ep-ac protein. Thermal withdrawal latency(TWL) was ob-served after the PVN injecting 8p-CPT-2′-O-Me-cAMP (8p-CPT),the agonist of Epac. Then activated down-stream MEK1/2 protein of Epac in PVN was detected using Western blot when the potency was the strongest.Results ① Compared with normal saline(control group),TWL decreased significantly on d 1, d 3, d 5, d 7,d 9 on the ipsilateral foot of CFA group rats(P<0.01),whereas it returned to normal level in d 13;the paw mechanical withdrawal threshold(PMWT) de-creased significantly on d 6,d 8,d 10,d 12 and d 14 (P<0.05);②Compared with the control,the Epac1 protein in CFA group rats began to decrease from d 3, and significantly decreased on d 3 and d 9(P<0.05), however the expression of Epac2 had no significant change, meanwhile p-MEK1/2 protein decreased sig-nificantly on d 3(P<0.05);③Compared with micro-injection of saline into the PVN(Saline group), the heat hyperalgesia of 20 min and 1h decreased signifi-cantly and TWL increased significantly after PVN ad-ministration of 8p-CPT(8p-CPT group)(P <0.05);paraventricular nucleus p-MEK1/2 protein expression increased significantly in 30 min(P <0.05) and re-covered to normal level 2 h after administration. Con-clusion The Epac1-MEK1/2 signaling pathway in the paraventricular nucleus of the hypothalamus may be in-volved in the development of chronic inflammatory pain induced by CFA.%目的 探讨下丘脑室旁核Epac在大鼠炎症性疼痛发展过程中的作用及其机制.方法 健康成年♂SD大鼠,通过左侧后肢足底中心皮下注射完全弗氏佐剂(complete Fre-und's adjuvant,CFA)建立炎症性疼痛模型,Western blot检测Epac蛋白的表达变化;室旁核给予 Epac激动剂8p-CPT (8p-CPT -2′-O-Me-cAMP)后,测定大鼠热缩足潜伏期(ther-mal withdrawal latency,TWL),观察痛行为变化,并在药效发挥最大作用时,取出大鼠下丘脑室旁核,用Western blot检测Epac下游p-MEK1/2蛋白表达情况.结果 与生理盐水对照组相比,CFA组大鼠炎症侧后足d 1、3、5、7、9、11的TWL明显降低(P<0.01),d 13的TWL基本恢复至正常水平;d 6、8、10、12、14的机械缩足反射阈值(paw mechanical with-draw threshold,PMWT)明显降低(P<0.05).与生理盐水对照组相比,CFA组大鼠室旁核Epac1蛋白表达在d 3开始明显降低,且在d 3和d 9均有统计学意义(P<0.05),而Ep-ac2蛋白表达则没有明显变化,p-MEK1/2蛋白表达在d 3开始降低(P<0.05).与室旁核微量注射生理盐水组相比,8p-CPT组大鼠于给药后20 min和1 h热痛敏均明显减轻,TWL明显升高(P <0.05);室旁核 p-MEK1/2蛋白在给药后30 min表达明显升高(P<0.05),2 h后恢复至给药前水平.结论 下丘脑室旁核 Epac1-MEK1/2信号通路可能参与了CFA所致的慢性炎症性疼痛的发展过程.