星形胶质细胞在完全弗氏佐剂诱导的炎性痛中的作用

目的 探讨脊髓背角星形胶质细胞在完全弗氏佐剂(complete Freund's adjuvant,CFA)诱导的炎性痛中的作用.方法 雄性SD大鼠随机分为3组(6只/组):CFA组(大鼠左后肢足底注射CFA诱导炎性痛,同时行鞘内置管术,术后6 d鞘内给予生理盐水);L-α-aminoadipate(LAA)组(处理方式同CFA组,但术后6 d鞘内给予LAA);对照组(处理方式同CFA组,但足底注射生理盐水).术前2 d及术后7 d检测各组机械痛和热痛阈值,术后7 d以Real-time PCR法检测脊髓背角GFAP mRNA变化.结果 术前2 d各组大鼠左后肢足底机械痛及热痛阈值无明显差异(P> 0.05).术后7 d,CFA组大鼠脊髓背角GFAP mRNA较对照组明显增高(P<0.01),左后肢足底机械痛及热痛阈值较对照组明显降低(P<0.01);与CFA组相比,LAA组大鼠脊髓背角GFAP mRNA明显降低(P<0.01),左后肢足底机械痛及热痛阈值均明显增高(P<0.01).结论 LAA特异性抑制脊髓背角星形胶质细胞活性,缓解了CFA大鼠炎性痛,提示脊髓背角星形胶质细胞活化是CFA诱导炎性痛的重要机制.     

IL-36Ra抑制炎性痛小鼠脊髓A1型星形胶质细胞极化

目的评价不同剂量IL-36Ra对炎性痛小鼠痛行为以及脊髓A1型星形胶质细胞极化的影响。方法雄性C57BL/6小鼠32只,采用足底注射完全弗氏佐剂(CFA)建立炎性痛模型。随机将小鼠分为CFA+生理盐水组、CFA+IL-36Ra 50 ng组、CFA+IL-36Ra 100 ng组以及CFA+IL-36Ra 200 ng组,每组8只。各组小鼠在造模后d 1~d 7,每日1次鞘内给药。同时,分别在造模前以及造模后d 1、3、5、7检测4组小鼠机械刺激缩足阈值(mechanical withdraw threshold, MWT)和辐射热刺激缩爪潜伏期(PWL)的变化。以逆转录聚合酶链反应检测IL-36Ra对CFA小鼠脊髓A1、A2型星形胶质细胞标志物表达水平的影响。以免疫组化法检测各组小鼠脊髓背角A1型星形胶质细胞标志物C3与GFAP共表达水平的变化。结果炎性痛小鼠造模后患侧MWT、PWL均明显下降,IL-36Ra(100、200 ng)可显著改善小鼠的机械性痛觉超敏与热痛觉过敏;且在治疗7 d后,IL-36Ra可降低CFA小鼠脊髓星形胶质细胞激活标志物GFAP、Lcn2的表达水平,抑制星形胶质细胞激活;同时,IL-36Ra(100、200 ng)可下调CFA小鼠脊髓A1型星形胶质细胞标志物Serping1、 H2-T23的mRNA水平,但IL-36Ra各个剂量对A2型星形胶质细胞标志物表达没有明显作用;此外,IL-36Ra还可抑制脊髓背角A1型星形胶质细胞标志物C3表达。结论 IL-36Ra可能通过抑制CFA小鼠脊髓A1型星形胶质细胞极化,进而改善小鼠炎性痛痛行为。     

背根神经节脉冲射频术对炎性痛大鼠痛阈及脊髓胶质细胞活化的影响

目的 评价背根神经节脉冲射频对炎性痛大鼠脊髓星形胶质细胞标记物胶质纤维酸性蛋白（GFAP）、小胶 质细胞标记物补体受体-3的单克隆抗体（OX42）表达的影响。方法 成年雄性 SD大鼠 32只,采用随机数字表法分 为4组（n=8）：对照组（C组）、炎性痛组（IP组）、脉冲射频组（PR组）和炎性痛+脉冲射频组（IP+PR组）。脉冲射频组和 炎性痛+脉冲射频组于造模后第 4天行 L4-5背根神经节脉冲射频术。各组大鼠于造模前（d0）和造模后第 1、3、5、7天 （d1、d3、d5、d7）测定机械缩足反应阈（MWT）和热缩足潜伏期（TWL）。取L4-6脊髓组织,采用Western blot法检测脊髓 GFAP和 OX42的表达。结果 与 C组和与 PR组比较,IP组和 IP+PR组炎性痛造模后各时点 MWT降低,TWL缩短 （P＜0.05）;与 IP组比较,IP+PR组行脉冲射频术后各时点（d5和 d7）MWT升高,TWL延长（P＜0.05）;与 C组和与 PR 组比较,IP组和IP+PR组脊髓GFAP和OX42表达上调（P＜0.05）;与IP组比较,IP+PR组比较脊髓GFAP和OX42表达 降低（P＜0.05）。结论 背根神经节脉冲射频可减轻炎性痛大鼠痛敏反应,抑制炎性痛大鼠脊髓胶质细胞活化。     

丙戊茶碱预处理削弱大鼠关节炎痛觉过敏的脊髓机制

目的研究预先鞘内注射丙戊茶碱对大鼠佐剂性关节炎热痛觉过敏的影响及其作用是否与抑制脊髓星形胶质细胞活化相关。方法实验采用大鼠右后爪踝关节外侧皮下注射CFA50μl致炎模型。①SD大鼠48只,随机分为6组(n=8),生理盐水(normal saline,NS)组:鞘内注射(intrathecal injection,it)NS10μl加皮下注射NS50μl;模型组:NSi加皮下注射CFA;单用丙戊茶碱组:10μg/10μl丙戊茶碱i加皮下注射NS;丙戊茶碱治疗组,分别为p2.5、p5、p10组:2.5μg/10μl、5μg/10μl及10μg/10μl丙戊茶碱it加皮下注射CFA。热辐射法测定各组大鼠热缩足反射潜伏期。②SD大鼠30只,随机分为6组(n=5),随机取3组鞘内预先注射生理盐水10μl,30min后注射CFA50μl,并分别于注射CFA5h、3d、7d麻醉;余大鼠预先注射丙戊茶碱(10μg/10μl,it),每天1次,30min后注射CFA50μl制成炎症模型,分别于注射CFA后5h、3d、7d麻醉;灌注,取材,免疫组化分析在炎症的不同阶段,大鼠炎症侧脊髓背角星形胶质细胞标志物GFAP表达。结果①模型组大鼠注射侧d2热缩足反射潜伏期与生理盐水组比较明显缩短(P<0.01),鞘内注射丙戊茶碱(5和10μg/10μl组)5h后大鼠热缩足反射潜伏期明显延长(P<0.01),有效作用时间为d1~d7;2.5μg/10μl组药物有效作用时间为d1~d2;注射对侧肢体大鼠行为学在实验观察期间没有明显变化;②模型组大鼠注射侧脊髓背角星形胶质细胞活化明显,积分光密度值增加(P<0.01)。鞘内注射丙戊茶碱(10μg/10μl组)5h后免疫组织化学染色可看到GFAP染色变浅,星形胶质细胞分支缩短,积分光密度值下降(P<0.01)。结论预先鞘内注射丙戊茶碱可提高大鼠热反射缩足潜伏期,可能通过抑制脊髓部位星形胶质细胞活化发挥抗伤害性作用。     

鞘内注射左旋布比卡因下调甲醛炎性痛大鼠远位触液神经元P物质的表达

目的观察鞘内注射左旋布比卡因对甲醛炎性痛大鼠P物质(substanceP,SP)在脊髓背角及远位触液神经元(thedistal cerebrospinal fluid contacting neuron,dCSF-CN)表达的影响。方法采用CB-HRP大鼠侧脑室注射示踪标记dCSF-CN;48h后先鞘内注射0.5%左旋布比卡因10μl(并以鞘内注射10μl人工脑脊液作对照),大鼠左后掌足跖部皮下注射2.5%福尔马林建立炎性痛模型,记录大鼠舔足时间,1h后测定机械缩足阈值(mechanical withdrawal threshold,MWT)评估机械痛敏;免疫组织化学光镜镜检及免疫电镜镜检P物质在脊髓背角(L4~5)及dCSF-CN的表达。结果鞘内注射左旋布比卡因减少大鼠福尔马林试验的舔足时间(P<0.01),MWT值无变化(与基础值对比,P>0.05),SP在脊髓背角及dCSF-CN的表达弱于对照组(P<0.01)。结论鞘内注射左旋布比卡因减低脊髓伤害性疼痛反应及下调SP在dCSF-CN的表达。     

鞘内注射甘珀酸对腰5脊神经切断大鼠痛觉高敏的影响

目的观察鞘内注射甘珀酸(CBX)对腰5脊神经切断(SNT)大鼠机械痛阈及脊髓背角星形胶质细胞标志物(GFAP)和TNF-α、IL-1β表达的影响。方法 36只成年♂SD大鼠,随机分成3组(n=12),假手术组(Sham组)、SNT+NS组(NS组)、SNT+CBX(CBX组)。Sham组仅暴露腰5脊神经,不切断,NS组和CBX组切断腰5脊神经。术后10d,Sham组和NS组鞘内注射生理盐水10μl,CBX组鞘内注射甘珀酸5μg(10μl),分别于术前1 d,术后1、3、5、7、10 d及给药后1、2、4、6 h随机取6只大鼠测损伤侧机械痛阈(MWT),并采用免疫组化技术观察给药后2 h后损伤侧脊髓背角中GFAP表达的变化,ELISA测定损伤侧脊髓背角TNF-α和IL-1β的水平。结果 3组大鼠术前1 d,MWT差异均无显著性(P>0.05);Sham组术后各时间点与术前相比损伤侧MWT差异无显著性(P>0.05);与Sham组相比,NS组和CBX组术后1、3、5、7、10 d痛阈明显下降(P<0.05);NS组术后10 d给药后1、2、4、6 h,MWT与给药前无差异(P>0.05),但给药后2 h损伤侧脊髓背角GFAP的表达和TNF-α、IL-1β的水平较Sham组明显增高(P<0.05);CBX组给药后1、2、4 h损伤侧MWT较给药前明显提高(P<0.05),6 h无差异(P>0.05),给药后2 h损伤侧脊髓背角GFAP的表达和TNF-α、IL-1β的水平较NS组明显降低(P<0.05)。结论单次鞘内注射5μg CBX可改善脊神经切断大鼠损伤侧机械痛敏行为,该效应可能与其抑制损伤侧脊髓背角星形胶质细胞的活化,减少TNF-α、IL-1β的释放有关。     

鞘内注射米诺四环素对慢性坐骨神经结扎大鼠机械痛敏和热痛敏的影响

目的观察鞘内注射小胶质细胞抑制剂米诺四环素对慢性坐骨神经结扎大鼠机械痛敏和热痛敏的影响。方法所有大鼠术前8d鞘内置管,用机械缩足反射阈值和热缩足潜伏期来分别评价大鼠机械痛敏和热痛敏。前给药组:生理盐水10μl或米诺四环素50μg,于坐骨神经结扎前1d开始持续到术后1d(每天2次)鞘内注射,机械缩足反射阈值和热缩足潜伏期分别于术前2d,术后1,3,5,7,14d测定;后给药组:坐骨神经结扎后7d,鞘内注射1次生理盐水10μl或米诺四环素50μg,其对机械缩足反射阈值和热缩足潜伏期的影响分别于给药后0.5、1、2、4、8h测定。结果CCI大鼠从术后1d形成稳定的热痛敏和机械痛敏,前鞘内注射米诺四环素明显增加CCI大鼠MWT和TWL(P<0.05,P<0.01),相反,后鞘内注射米诺四环素对CCI大鼠MWT和TWL无明显影响。结论前鞘内注射米诺四环素明显抑制CCI大鼠机械痛敏和热痛敏,提示小胶质细胞的活化参与慢性坐骨神经结扎引发神经病理痛的形成。     

红花注射液通过抑制脊髓小胶质细胞激活及炎性因子的释放缓解大鼠炎性痛的研究

目的探讨红花注射液缓解完全弗氏佐剂所致大鼠炎性痛的药理作用机制。方法将24只大鼠随机分为假手术组、完全弗氏佐剂组、地塞米松阳性对照组和红花注射液治疗组,每组6只。通过测定大鼠热刺激缩足反应潜伏期和机械缩足反射阈值,观察红花注射液是否具有缓解大鼠炎性痛的作用。采用免疫荧光检测炎性痛大鼠脊髓小胶质细胞的激活;免疫印迹法检测炎性痛大鼠脊髓背角神经元细胞内p-ERK、p-CREB蛋白的表达;ELISA法检测炎性痛大鼠脊髓背角组织中TNF-α、IL-1β和IL-6的表达;RT-PCR法检测炎性痛大鼠脊髓背角神经元细胞内c-fos基因的表达。结果红花能够延长炎性痛大鼠热刺激缩足反应潜伏期,提高炎性痛大鼠机械刺激缩足反射阈值;红花通过抑制脊髓小胶质细胞激活,减少炎性痛大鼠脊髓背角p-ERK和p-CREB蛋白,抑制TNF-α、IL-1β和IL-6的释放,降低c-fos基因的表达发挥镇痛作用。结论红花对炎性痛具有较好的缓解作用,其机制可能与抑制小胶质细胞激活,调节p-ERK信号通路和减少TNF-α、IL-1β和IL-6的释放有关。     

下丘脑室旁核ATP敏感性钾离子通道参与大鼠炎性痛调节的作用研究

目的探讨下丘脑室旁核ATP敏感性钾离子通道(KATP通道)在大鼠炎性痛中的作用。方法♂SD大鼠(250²80 g),采用随机数字法分为5组(每组6只):正常组(Normal组)、完全弗氏佐剂致炎性痛组(CFA组)、生理盐水组(Saline组)、KATP通道特异性激动剂组(Diaoxide组)和激动剂溶媒组(Vehicle组)。以热痛敏刺激仪检测各组大鼠热缩足潜伏期(TWL),观察痛行为学变化;以免疫荧光技术观察室旁核KATP通道和脊髓背角c-Fos阳性细胞数的变化。并观察KATP通道激动剂对大鼠痛行为和脊髓背角c-Fos表达的影响。结果 1与术前和Saline组相比,CFA组大鼠炎症侧后足术后d 1、d 3和d 7的TWL降低(P<0.05),CFA组术后d 3、d 7的KATP阳性细胞数减少(P<0.01),脊髓背角c-Fos阳性细胞数增加(P<0.01);2与Vehicle组相比,激动剂组大鼠热痛觉过敏减轻(P<0.01),脊髓背角c-Fos阳性细胞数减少(P<0.01)。结论下丘脑室旁核KATP通道可能与CFA所致炎性痛的发生机制相关。     

8-O-乙酰山栀子苷甲酸对慢性炎性痛模型大鼠脊髓背角内HDAC1～5表达的影响及与JAK_2-STAT_3信号通路的关系研究

目的:研究8-O-乙酰山栀子苷甲酸(8-OaS)对慢性炎性痛模型大鼠脊髓背角内组蛋白去乙酰化酶1～5(HDAC1～5)表达的影响及与Janus激酶2-信号转导与转录活化因子3(JAK_2-STAT3)信号通路的关系。方法:取SD大鼠随机分为正常对照组、假手术组(生理盐水)、完全弗氏佐剂(CFA)组(生理盐水)和8-OaS低、中、高剂量组(2、20、200μg/kg),每组6只,除正常对照组和假手术组外,其余各组大鼠左侧后足趾侧皮下注射CFA复制慢性炎性痛模型,建模后腹腔注射相应药物,每日1次,连续7 d。采用热辐射法检测首次给药第1、2、3、4、5、6、7、8、11、15天大鼠的缩足潜伏期。另取大鼠按上述后5组方法进行分组给药,采用Western blot法检测大鼠末次给药后腰膨大节段脊髓背角中HDAC1～5、磷酸化JAK_2(pJAK_2)、磷酸化STAT3(pSTAT3)蛋白表达情况。再另取大鼠随机分为假手术组(生理盐水)、CFA组(生理盐水)、8-OaS组(20μg/kg)和JAK_2-STAT_3的拮抗药α-氰基-(3,4-羟基)-N-苄苯乙烯胺(AG490)组(8 mg/kg),每组6只,同上法复制IP模型后腹腔注射相应药物,每日1次,连续7 d,采用免疫荧光组织化学染色观察各组大鼠HDAC5和胶质纤维酸性蛋白(GFAP)在脊髓背角的表达情况。结果:与正常对照组和假手术组比较,其余各组大鼠的缩足潜伏期均明显缩短(P<0.05);与CFA组比较,8-OaS低、中、高剂量组大鼠的缩足潜伏期均明显延长(P<0.05),且呈剂量依赖性。与假手术组比较,CFA组大鼠脊髓背角中HDAC1～5、pJAK_2、pSTAT3蛋白表达均明显增强(P<0.05);与CFA组比较,8-OaS低、中、高剂量组大鼠脊髓背角中HDAC5、pJAK_2、pSTAT3蛋白表达均明显降低(P<0.05),但HDAC1～4蛋白表达差异均无统计学意义(P>0.05)。HDAC5大量表达于星形胶质细胞上,与假手术组比较,CFA组大鼠脊髓背角中GFAP和HDAC5表达均明显增强(P<0.05);与CFA组比较,8-OaS组和AG490组大鼠脊髓背角中GFAP和HDAC5表达均明显降低(P<0.05)。结论:8-OaS可有效缓解由CFA诱导的慢性炎性痛,其机制可能与下调脊髓背角中HDAC5表达和JAK_2、STAT3的磷酸化水平有关。     

Antisense oligonucleotide knockdown of mGluR1 alleviates hyperalgesia and allodynia associated with chronic inflammation

Chronic inflammation induced by injection of complete Freund's adjuvant (CFA) into one hindpaw elicits thermal hyperalgesia and mechanical allodynia in the injected paw. Metabotropic glutamate receptors (mGluRs) have been implicated in dorsal horn neuronal nociceptive responses and pain associated with short-term inflammation. The goal of the present study was to assess the role of mGluR1 in the hyperalgesia and allodynia associated with the CFA model of chronic inflammation. Here we show that antisense (AS) oligonucleotide knockdown of spinal mGluR1 attenuates thermal hyperalgesia and mechanical allodynia in rats injected with CFA in one hindpaw. When intrathecal infusion of mGluR1 AS oligonucleotide (50 microg/day) began prior to CFA injection, mechanical allodynia was attenuated from Days 1 to 8 following CFA injection, whereas heat hyperalgesia was attenuated on Day 1 and then from Days 4 to 8. When intrathecal infusion of mGluR1 AS oligonucleotide was begun 2 days after CFA injection, both mechanical allodynia and heat hyperalgesia were attenuated at all time points following the oligonucleotide infusion. Thus, the present data suggest a role for mGluR1 in persistent inflammatory nociception.     

Activation of spinal orexin-1 receptor produces anti-allodynic effect in the rat carrageenan test

Orexin-A and orexin-1 receptors are found in the dorsal root ganglion cells and the spinal dorsal horn and this suggests that orexin-A is involved in the spinal nociceptive transmission. The authors examined the effect of intrathecally administered orexin-A on the level of mechanical allodynia and thermal hyperalgesia induced by paw carrageenan injection in the rat. Intrathecal injection of 0.3 and 3 nmol of orexin-A suppressed the level of mechanical allodynia, but not that of thermal hyperalgesia, and the effect of orexin-A on mechanical allodynia was antagonized by the pretreatment of 1-(2-methylbenzoxazol-6-yl)-3-[1,5]naphthyridin-4-yl urea hydrochloride, SB-334867, a selective orexin-1 receptor antagonist. These data suggest that the activation of spinal orexin-1 receptor modulates the mechanical information transmission, but not thermal information transmission, in the spinal cord during carrageenan test.     

Involvement of subtype 1 metabotropic glutamate receptors in apoptosis and caspase-7 over-expression in spinal cord of neuropathic rats.

The effect of the non-selective, 1-aminoindan-1,5-dicarboxylic acid (AIDA), and selective (3,4-dihydro-2H-pyrano[2,3-b]quinolin-7-yl)-(cis-4-methoxycyclohexyl) methanone (JNJ16259685), metabotropic glutamate subtype 1 (mGlu1) receptor antagonists, on rat sciatic nerve chronic constrictive injury (CCI)-induced hyperalgesia, allodynia, spinal dorsal horn apoptosis, and gliosis was examined at 3 and 7 days post-injury. RT-PCR analysis showed increased expression of bax, apoptotic protease-activating factor-1 (apaf-1), nestin, GFAP, and caspase-7 mRNA in the dorsal horn spinal cord by 3 days post-CCI. At 7 days post-CCI, only over-expression of bcl-2, nestin and GFAP mRNA was observed. Administration of AIDA reduced thermal hyperalgesia and mechanical allodynia at 3 and 7 days post-CCI; administration of JNJ16259685 reduced thermal hyperalgesia at 3 and 7 days post-CCI, but not mechanical allodynia. AIDA decreased the mRNA levels of bax, apaf-1, GFAP and caspase-7 genes. JNJ16259685 increased the mRNA levels of bcl-2 and GFAP gene, and decreased APAF-1 and caspases-7 genes. Inhibiting mGlu1 receptors also reduced TUNEL-positive profiles and immunohistochemical reactivity for caspase-7. We report here that despite inhibiting CCI-induced over-expression of pro-apoptotic genes in the spinal cord dorsal horn, the selective mGlu1 receptor antagonist JNJ16259685 exerted only a slight and transient allodynic effect. Moreover, JNJ16259685, but not the non-selective AIDA, increased astrogliosis which may account for its decreased analgesic efficacy. This study provides evidence that the contemporary and partial blockade of group I and likely ionotropic glutamate receptors may be a more suitable therapy than selective blockade of mGlu1 subtype receptors condition to decrease neuropathic pain symptoms.     

弗氏佐剂致炎大鼠脊髓背角Fos神经元的表达

目的探讨完全弗氏佐剂（CFA）致炎性痛大鼠Fos神经元（Fos-LIN）在脊髓背角痛觉传导通路中的表达及意义。方法①16只SD大鼠随机均分为两组,于右后肢踝关节外侧皮下分别注射0.9%生理盐水（NS）或CFA50μl,观察注射前后大鼠热缩足反射潜伏期TWL的变化;②48只大鼠随机平分为两组后分别注射NS和CFA（剂量和注射部位同前）以免疫组化法检测脊髓背角Fos-LIN表达。结果①大鼠注射CFA后TWL逐渐降低,12h时为最低点,持续3d后逐渐恢复,14d时基本恢复至基础水平;②NS组脊髓背角Fos-LIN散在出现,而CFA组中Fos-LIN1h时最先出现在大鼠右侧脊髓背角I-II层,4h时出现在V-VI层的数目逐渐增多,12h时为脊髓全层出现最多,至14d时在背角各层少见,且同组左侧脊髓各层Fos-LIN在1h-14d均比较少见。结论50μlCFA能诱导大鼠产生为期2周的炎性痛觉过敏。炎症期间脊髓背角Fos神经元的持续表达与外周痛觉信号的传导和中枢的调控有关。     

Dexmedetomidine blocks thermal hyperalgesia and spinal glial activation in rat model of monoarthritis

Aim:

To investigate the effect of systemic administration dexmedetomidine, a selective alpha 2 adrenergic receptor (α₂AR) agonist, on thermal hyperalgesia and spinal glial activation evoked by monoarthritis (MA).

Methods:

MA was induced by an intra-articular injection of complete Freund''s adjuvant (CFA). Thermal hyperalgesia was measured by Hargreaves'' test. The spinal glial activation status was analyzed by GFAP (an astrocytic marker) and Iba-1 (a microglial marker) immunohistochemistry or immunoblotting.

Results:

Unilateral intra-articular injection of CFA produced a robust glial activation of astrocytes and microglia in the spinal cord, which was associated with the development and maintenance of thermal hyperalgesia. Intraperitoneal (ip) injection of dexmedetomidine (2.5 and 10 μg/kg) was repeatedly given once daily for 5 days with the first injection 60 min before intra-articular CFA. At the dose of 10 μg/kg, dexmedetomidine significantly attenuated MA-induced ipsilateral hyperalgesia from day 2 to day 5. MA-induced up-regulation of GFAP expression on both sides of the spinal dorsal horn was significantly suppressed by day 5 post-MA following dexmedetomidine application, whereas MA-induced Iba-1 up-regulation was only partially suppressed.

Conclusion:

Systemic dexmedetomidine inhibits the activation of spinal glia, which is possibly associated with its antihyperalgesia in monoarthritic rats.     

Evidence for suppression of spinal glial activation by dexmedetomidine in a rat model of monoarthritis

1. Spinal glial cells play a key role in developing and maintaining allodynia and hyperalgesia following tissue inflammation. Dexmedetomidine, a highly selective α₂‐adrenoceptor (α₂‐AR) agonist, has exhibited a significant analgesic effect in various rodent models of chronic pain. However, whether spinal glial activation is involved in the analgesic effect of dexmedetomidine remains unknown. The present study investigated whether spinal administration of dexmedetomidine could antagonize glial activation in the spinal dorsal horn and attenuate thermal hyperalgesia in complete Freund’s adjuvant (CFA)‐induced ankle joint monoarthritic (MA) rats. 2. Unilateral intra‐articular injection of CFA produced a robust activation of microglia and astrocytes in the spinal cord, which was associated with the development and maintenance of thermal hyperalgesia. Repeated lumbar puncture (LP) administration of dexmedetomidine (10 μg) significantly attenuated MA‐induced thermal hyperalgesia in a cumulative manner. Monoarthritis‐induced spinal glial activation was also suppressed following dexmedetomidine application. The α_2A‐AR, essential for the antinociceptive effects of α₂‐AR agonists, was detected in spinal neurons and glia, as well as in dorsal root ganglion primary afferent neurons, which may be implicated in dexmedetomidine‐induced suppression of spinal glial activation and antihyperalgesic effects. 3. These data provide the first evidence that blocking spinal glial activation is involved in the analgesic action of dexmedetomidine.     

脊髓胶质细胞及前炎性细胞因子在慢性前列腺炎/慢性盆腔疼痛综合征大鼠中的作用及机制

目的探讨脊髓星形胶质细胞和小胶质细胞以及前炎性细胞因子白细胞介素-1β(IL-1β)、白细胞介素-6(IL-6)和肿瘤坏死因子α(TNFα)在CP/CPPS发生发展中的作用及机制。方法 40只健康雄性Sprague-Dawley(SD)大鼠,随机分为正常不加任何处理的对照组(n=20)、CP/CPPS模型组(n=20),完全福氏佐剂和3%角叉菜胶前列腺内注射造成CP/CPPS模型。通过检测机械性痛阈(PWT)来评价动物痛行为学改变;采用免疫组织化学、逆转录多聚酶链反应(RT-PCR)等方法,检测脊髓星形胶质细胞GFAP和小胶质细胞OX-42的表达以及脊髓前炎性细胞因子IL-1β、IL-6及TNFαmRNA表达的变化,评价脊髓小胶质细胞和星形胶质细胞活化情况及脊髓前炎性细胞因子表达与疼痛行为改变的关系。结果与对照组比较,CP/CPPS模型组大鼠建模后第11天出现PWT明显降低(P<0.05),并呈进行性下降趋势;随着时间进程,免疫组化结果显示模型组动物脊髓小胶质细胞和星形胶质细胞依次活化,小胶质细胞活化开始于建模后第7天,星形胶质细胞活化开始于建模后第14天;模型组动物脊髓IL-1β、IL-6和TNFαmRNA表达较对照组明显增加(P<0.05)。结论在CP/CPPS大鼠中脊髓胶质细胞活化及前炎性细胞因子IL-1β、IL-6和TNFα的表达增加,可能在神经病理性疼痛的产生和维持中起着重要的作用。     

Effect of Mas-related gene (Mrg) receptors on hyperalgesia in rats with CFA-induced inflammation via direct and indirect mechanisms

Background and Purpose

Mas oncogene-related gene (Mrg) receptors are exclusively distributed in small-sized neurons in trigeminal and dorsal root ganglia (DRG). We investigated the effects of MrgC receptor activation on inflammatory hyperalgesia and its mechanisms.

Experimental Approach

A selective MrgC receptor agonist, bovine adrenal medulla peptide 8-22 (BAM8-22) or melanocyte-stimulating hormone (MSH) or the μ-opioid receptor (MOR) antagonist CTAP was administered intrathecally (i.t.) in rats injected with complete Freund''s adjuvant (CFA) in one hindpaw. Thermal and mechanical nociceptive responses were assessed. Neurochemicals were measured by immunocytochemistry, Western blot, ELISA and RT-PCR.

Key Results

CFA injection increased mRNA for MrgC receptors in lumbar DRG. BAM8-22 or MSH, given i.t., generated instant short and delayed long-lasting attenuations of CFA-induced thermal hyperalgesia, but not mechanical allodynia. These effects were associated with decreased up-regulation of neuronal NOS (nNOS), CGRP and c-Fos expression in the spinal dorsal horn and/or DRG. However, i.t. administration of CTAP blocked the induction by BAM8-22 of delayed anti-hyperalgesia and inhibition of nNOS and CGRP expression in DRG. BAM8-22 also increased mRNA for MORs and pro-opiomelanocortin, along with β-endorphin content in the lumbar spinal cord and/or DRG. MrgC receptors and nNOS were co-localized in DRG neurons.

Conclusions and Implications

Activation of MrgC receptors suppressed up-regulation of pronociceptive mediators and consequently inhibited inflammatory pain, because of the activation of up-regulated MrgC receptors and subsequent endogenous activity at MORs. The uniquely distributed MrgC receptors could be a novel target for relieving inflammatory pain.     

Activation of ERK／CREB pathway in spinal cord contributes to chronic constrictive injury-induced neuropathic pain in rats

Aim: To investigate whether activation and translocation of extracellular signalregulated kinase (ERK) is involved in the induction and maintenance of neuropathic pain, and effects of activation and translocation of ERK on expression of pCREB and Fos in the chronic neuropathic pain. Methods: Lumbar intrathecal catheters were chronically implanted in male Sprague-Dawley rats. The left sciatic nerve was loosely ligated proximal to the sciatica‘s trifurcation at approximately 1.0 mm intervals with 4-0 silk sutures. The mitogen-activated protein kinase kinase (MEK) inhibitor U0126 or phosphorothioate-modified antisense oligonucleotides (ODN) were intrathecally administered every 12 h, 1 d pre-chronic constriction injury (CCI) and 3 d post-CCI. Thermal and mechanical nociceptive thresholds were assessed with the paw withdrawal latency (PWL) to radiant heat and von Frey filaments. The expression of pERK, pCREB, and Fos were assessed by both Western blotting and immunohistochemical analysis. Results: Intrathecal injection of U0126 or ERK antisense ODN significantly attenuated CCI-induced mechanical allodynia and thermal hyperalgesia. CCI significantly increased the expression of p-ERK-IR neurons in the ipsilateral spinal dorsal horn to injury, not in the contralateral spinal dorsal horn. The time courses of pERK expression showed that the levels of both cytosol and nuclear pERK, but not total ERK, were increased at all points after CCI and reached a peak level on postoperative d 5. CCI also significantly increased the expression of pCREB and Fos. Phospho-CREB-positive neurons were distributed in all laminae of the bilateral spinal cord and Fos was expressed in laminae I and II of the ipsilateral spinal dorsal horn. Intrathecal injection of U0126 or ERK antisense ODN markedly suppressed the increase of CCI-induced pERK, pCREB and c-Fos expression in the spinal cord. Conclusion:The activation of ERK pathways contributes to neuropathic pain in CCI rats, and the function of pERK may partly be accomplished via the cAMP response element binding protein (CREB)-dependent gene expression.