RvD1对大鼠2型糖尿病神经病理性痛的作用及机制研究

目的：采用2型糖尿病神经病理性痛大鼠,探讨其脊髓背角小胶质细胞极化情况以及消退素D1（RvD1）缓解大鼠2型糖尿病神经病理性痛的机制。方法：雄性SD大鼠高糖高脂饲养,腹腔注射链脲佐菌素（STZ）,制备大鼠2型糖尿病神经病理性痛模型。将2型糖尿病神经病理性痛大鼠随机分为3组（n=36）：2型糖尿病神经病理性痛组（D组）、2型糖尿病神经病理性痛注射RvD1组（R组）和溶剂对照组（S组）。R、S组分别于注射STZ 14 d后蛛网膜下腔置管,3 d后R、S组分别给予RvD1 10μl（10 ng/μl）和100%乙醇10μl,每天1次,连续14 d,D组不做任何处理。另取36只正常大鼠为正常对照组（N组）,普通饲料喂养。鞘内给药后第1、3、7、14天时测定机械缩足阈值（MWT）和热缩足潜伏期（TWL）,各组随机取9只大鼠处死,取L4-6脊髓膨大,采用Western blot法检测小胶质细胞M1、M2型极化标记物,即诱导型一氧化氮合酶（iNOS）、精氨酸酶1（Arg1）的表达。结果：与N组比较,D、S组第1、3、7、14天时MWT降低、TWL缩短,脊髓背角Arg1表达减少,iNOS表达增多（P < 0.05）;与D组比较,R组第7、14天时MWT升高、TWL延长,脊髓背角Arg1表达增多,iNOS表达减少（P < 0.05）;D组与S组各指标比较差异无统计学意义。结论：RvD1促进小胶质细胞M2型极化并缓解大鼠2型糖尿病神经病理性痛。     

右美托咪啶对神经痛大鼠脊髓背角pERK、pCREB表达的影响

目的:评价右美托咪啶对神经病理性痛大鼠脊髓背角神经元磷酸化胞外反应激酶(phosphoryltion of extracellular regulated protein kinases,p ERK)、磷酸化c AMP反应元件结合蛋白(phosphoryltion of Camp response element bound protein,p CREB)蛋白表达的影响。方法:健康成年雄性Wistar大鼠54只,6~8周龄,体重180~220 g,采用随机数字表法,将其分为3组(n=18):假手术组(S组)、慢性神经病理性痛组(C组)和右美托咪啶组(D组)。S组仅分离坐骨神经但不结扎,C组和D组采用结扎坐骨神经的方法制备大鼠坐骨神经慢性压迫性损伤(chronic constriction injury,CCI)的神经病理性痛模型,D组于术后即刻开始至处死前1d腹腔注射右美托咪啶50μg/kg,1次/d,S组和C组注射等容量生理盐水。于术前1 d、术后3、7、14 d时以缩足阈值(paw withdrawal threshold,PWT)测定大鼠机械痛阈和辐射热的缩足潜伏期(paw withdrawl latency,PWL)测定大鼠的热痛阈,并于术后测定痛阈后灌注处死大鼠,取L4-6脊髓组织,采用免疫组织化学法检测脊髓背角神经元p ERK、p CREB的表达水平。结果:与S组比较,C组和D组术后3、7、14 d时MWT降低,TWL缩短,脊髓背角p ERK、p CREB表达上调(P0.05);与C组比较,D组术后3、7、14 d时MWT升高,TWL延长,脊髓背角p ERK、p CREB表达下调(P0.05)。与术前1 d比较,C组和D组术后3、7、14 d时MWT降低,TWL缩短;与术后3 d时比较,C组和D组7、14 d时MWT降低,TWL缩短,脊髓背角p ERK、p CREB表达上调(P0.05)。结论:右美托咪啶可减轻大鼠慢性神经病理性痛,抑制p ERK、p CREB的表达可能是其作用机制之一。     

靶向毁损触液核对大鼠痛行为及脊髓背角5-HT和c-Fos表达的影响

目的：观察缺失触液核（CSF-contacting nucleus）对大鼠痛行为及脊髓背角痛相关物质5-羟色胺（5-HT）和c—Fas表达的影响,为触液核参与疼痛调制及机制提供实验依据。方法：成年雄性SD大鼠随机分为正常组（Control）,假手术组（Sham）,霍乱毒素亚单位B与辣根过氧化酶复合物（CB—HRP）组和毁损触液核组（Damage）。以机械缩足阈值（MWT）和热缩足潜伏期（耶儿）测定大鼠痛行为。免疫荧光法检测脊髓背角5-HT和c—Fos表达,并进行痛行为阈值与物质变化趋势的相关分析。结果：与Control、Sham和CB—HRP组相比,Damage组大鼠MWT和TWL明显降低（P〈0．05）。免疫荧光结果显示,正常大鼠触液核神经元高表达5-HT;Damage组大鼠触液核神经元数量随毁损天数延续逐渐减少,且在给予毁损剂CB—SAP第10天完全消失。与此同时脊髓背角5-HT和c—Fos表达量日趋增加,且与痛行为阈值变化趋势成负相关。结论：CB—SAP能科学可靠靶向毁损触液核,缺失触液核可致大鼠痛行为阈值减低,而脊髓背角5-HT和c—Fos表达量增加。本研究提示触液核参与了疼痛调制,且5-HT和c—Fos在此调制中发挥了重要作用。     

慢性炎性痛大鼠脊髓背角单羧酸转运蛋白-2表达的变化

目的:在大鼠慢性炎性痛模型上,观察大鼠脊髓背角单羧酸转运蛋白-2(MCT-2)表达的变化。方法:健康雄性SD大鼠96只,体重180~220 g,采用随机数字表法将其随机分为2组(n=48):生理盐水组(NS组)和完全性弗氏佐剂组(CFA组)。CFA组左侧后足足底中部皮下注射完全性弗氏佐剂(CFA)100μl;NS组注射等量的生理盐水。在注射前(T0)及注射后3 h(T1)、第1天(T2)、3天(T3)、5天(T4)、7天(T5)、14天(T6)和第21天(T7)测定大鼠机械缩足反应阈值(MWT)和热缩足反应潜伏期(TWL),并于上述各时间点分别随机取4只大鼠,处死后取脊髓背角,采用Western blot法测定MCT-2表达的变化。结果:CFA组大鼠在注射CFA后3 h即出现痛觉过敏,并持续至第14天,其疼痛程度显著大于NS组(P0.05);且T1-6时脊髓背角MCT-2与NS组相比显著增加(P0.05)。大鼠脊髓背角MCT-2的表达与MWT和TWL相关(P0.05,P0.01)。结论:慢性炎性痛大鼠脊髓MCT-2表达上调,该变化可能参与慢性炎性痛中枢敏化的形成和维持。     

姜黄素对糖尿病大鼠疼痛过敏的影响

目的：神经病理性痛是糖尿病最常见的并发症之一,本课题旨在探讨姜黄素对糖尿病大鼠痛觉过敏的影响及其分子机制。方法：30只雄性SD大鼠随机分为对照组、糖尿病组和姜黄素治疗纽,模型纽和姜黄素治疗组利用腹腔注射链脲佐菌素（Streptozotocin,STZ）制备大鼠糖尿病模型,定期检测大鼠血糖、饮食、体重等变化,治疗组于STZ注射2wk后定期灌服姜黄素,分别在2wk和4wk后检测各组大鼠热痛敏和机械痛敏反应,在第4wk利用ELISA分别检测各组大鼠脊髓背角TNF-α表达变化。结果：STZ注射组大鼠2周后出现血糖〉14mol／L,并且该模型具有高血糖、体重增长缓慢、多饮多食多尿的特点,符合Ⅰ型糖尿病特征,痛行为测试结果显示糖尿病大鼠出现痛觉过敏,经过给予姜黄素灌服治疗后,痛觉过敏有所减轻,ELISA分析结果表明糖尿病大鼠脊髓背角TNF-α表达升高,经过姜黄素治疗后TNF-α表达有所下降。结论：成功制备STZ-型糖尿病大鼠模型,经过姜黄素治疗可以减轻糖尿病引起的疼痛过敏,姜黄素对糖尿病疼痛的治疗作用可能是通过降低大鼠脊髓背角TNF-α表达实现的。     

积雪草酸对大鼠神经病理性痛的影响及其相关机制

目的:探讨积雪草酸对大鼠神经病理性痛的影响及其可能机制。方法:选择32只体重220~240 g的雄性SD大鼠,采用随机数字表法将其分为4组(n=8):假手术对照组(S组)、神经病理性痛组(N组)、积雪草酸5 mg/kg组(AA_1组)及积雪草酸10 mg/kg组(AA_2组)。S组大鼠只暴露但不结扎坐骨神经;N组大鼠仅制备神经病理性痛模型;AA_1组和AA_2组大鼠制备神经病理性痛模型,并于模型建立后即刻及术后1、3、5、7天分别腹腔注射积雪草酸5、10、20 mg/kg(溶于0.1 mL生理盐水)。于术前1天(T0)及术后1、3、5、7天(T1-T4)分别测定大鼠机械缩足反应阈位(MWTs)和热缩足潜伏期(TWLs),采用Western blot法检测脊髓HMGB1、RAGE、IL-1β、TNF-α、iNOS蛋白表达。结果:与N组比较,AA2组T1-T4时间点MWT显著增加、TWL明显缩短,而AA1组仅MWT显著增加(P0.05),但各组各时间点TWL比较差异均无统计学意义(P0.05)。与S组比较,N组脊髓浆蛋白HMGB1和RAGE及总蛋白IL-1β、TNF-α、iNOS蛋白表达较高(P0.05);与N组比较,AA_1和AA_2组脊髓浆蛋白HMGB1和RAGE及总蛋白IL-1β、TNF-α、iNOS蛋白表达均明显下降(P0.05)。与AA_1组比较,AA_2组脊髓脊髓浆蛋白HMGB1和RAGE及总蛋白IL-1β、TNF-α、iNOS蛋白表达都明显降低(P0.05)。结论:积雪草酸可能通过缓解HMGB1-RAGE信号通路介导的脊髓炎症反应减轻神经病理性痛。     

姜黄素对糖尿病大鼠疼痛过敏的影响

目的:神经病理性痛是糖尿病最常见的并发症之一,本课题旨在探讨姜黄素对糖尿病大鼠痛觉过敏的影响及其分子机制。方法:30只雄性SD大鼠随机分为对照组、糖尿病组和姜黄素治疗组,模型组和姜黄素治疗组利用腹腔注射链脲佐菌素(Streptoz-otocin,STZ)制备大鼠糖尿病模型,定期检测大鼠血糖、饮食、体重等变化,治疗组于STZ注射2wk后定期灌服姜黄素,分别在2wk和4wk后检测各组大鼠热痛敏和机械痛敏反应,在第4 wk利用ELISA分别检测各组大鼠脊髓背角TNF-α表达变化。结果:STZ注射组大鼠2周后出现血糖>14mol/L,并且该模型具有高血糖、体重增长缓慢、多饮多食多尿的特点,符合I型糖尿病特征,痛行为测试结果显示糖尿病大鼠出现痛觉过敏,经过给予姜黄素灌服治疗后,痛觉过敏有所减轻,ELISA分析结果表明糖尿病大鼠脊髓背角TNF-α表达升高,经过姜黄素治疗后TNF-α表达有所下降。结论:成功制备STZ-型糖尿病大鼠模型,经过姜黄素治疗可以减轻糖尿病引起的疼痛过敏,姜黄素对糖尿病疼痛的治疗作用可能是通过降低大鼠脊髓背角TNF-α表达实现的。     

右美托咪啶可通过下调Toll样受体4(TLR4)和核因子-kappa b(NF-κB)来减轻神经病理性痛

为了探讨右美托咪啶对神经病理性痛大鼠脊髓背角Toll样受体4(toll like receptor 4,TLR4)和核因子-kappa b(nuclear factor-kappa b,NF-κB)表达的影响,我们选取了54只6~8周的雄性Wistar大鼠,将大鼠随机分为假手术组、模型组和观察组,每组18只,其中模型组和观察组大鼠建立慢性压迫性损伤(chronic constriction injury,CCI)模型。我们检测了各组机械痛阈(mechanical withdrawal threshold,MWT)和热痛阈(thermal withdrawl latency,TWL),并采用RT-PCR和Western blotting方法检测了各组大鼠脊髓4~6节段TLR4和NF-κB的mRNA和蛋白表达。我们发现,术后7 d和14 d模型组和观察组大鼠的MWT和TWL明显低于假手术组(p0.05),且较术前有所降低(p0.05);观察组术后7 d和14 d的MWT和TWL均明显高于模型组(p0.05);模型组和观察组术后7 d和14 d TLR4和NF-κB的mRNA和蛋白表达水平明显高于假手术组(p0.05),且较术前有所增高(p0.05);观察组术后7 d和14 d TLR4和NF-κB mRNA的表达均明显低于模型组(p0.05);观察组术后7 d和14 d TLR4和NF-κB蛋白的表达均明显低于模型组(p0.05)。研究表明,右美托咪啶可减轻神经病理性痛,且与其下调TLR4和NF-κB表达有一定的关系。我们的研究为神经病理性痛机制的研究及治疗提供了一定的帮助。     

大鼠脊髓小胶质细胞P2X4的表达和糖尿病病理性神经痛大鼠炎症反应和疼痛阈值的关系

摘要 目的：探究大鼠脊髓小胶质细胞P2X4的表达和糖尿病病理性神经痛大鼠炎症反应和疼痛阈值的关系。方法：通过高脂饮食结合链脲佐菌素注射诱导糖尿病病理性神经痛大鼠模型并分为3组：对照组（正常大鼠,腹腔注射载体柠檬酸盐缓冲液0.25 mL/kg）,模型组（糖尿病病理性疼痛模型,同上注射,n=15）和抑制剂组（大鼠糖尿病病理性模型,过鞘内导管注射米诺环素）,共28 d。通过MWT评估对机械刺激的手掌反应。通过双极针电极检测实验大鼠的运动神经传导速速。通过蛋白印迹分析P2X4和BDNF蛋白表达。通过RT-PCR分析炎症因子IL-1β、TNF-α和NLRP3的mRNA表达。通过蛋白印迹分析p38MAPK和p-p38MAPK的蛋白表达。结果：第2week、4week和6week,模型组MWT较对照组降低（P<0.05）,抑制剂组MWT较模型组升高（P<0.05）。第2 week,个实验组大鼠MNCV比较无差异（P>0.05）,第4week和第6week,模型组MNCV较对照组降低（P<0.05）,抑制剂组MNCV较模型组升高（P<0.05）。模型组P2X4和BDNF蛋白表达较对照组升高（P<0.05）,抑制剂组P2X4和BDNF蛋白表达较模型组降低（P<0.05）,模型组P2X4和BDNF mRNA表达较对照组升高（P<0.05）,抑制剂组P2X4和BDNF mRNA表达较模型组降低（P<0.05）。模型组IL-1β、TNF-α和NLRP3的mRNA表达较对照组升高（P<0.05）,抑制剂组IL-1β、TNF-α和NLRP3的mRNA表达较抑制剂组降低（P<0.05）。模型组p-p38MAPK蛋白表达较对照组升高（P<0.05）,抑制剂组p-p38MAPK蛋白表达较模型组降低（P<0.05）,各实验组大鼠p38MAPK蛋白表达无差异（P>0.05）。结论：大鼠脊髓小胶质细胞P2X4-BDNF信号在DNP中起重要作用,并且P2X4在DNP期间激活的脊髓小胶质细胞中表达升高,抑制小胶质细胞激活能显著降低P2X4表达和炎症水平,可防止热痛觉过敏并增加大鼠疼痛阈值。     

电针对糖尿病神经痛模型大鼠痛觉敏化及脊髓小胶质细胞BDNF表达的影响

目的观察糖尿病神经痛(diabetic neuropathic pain,DNP)大鼠L4-L6脊髓背角中小胶质细胞和脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)表达的变化及电针对其干预作用,探讨小胶质细胞和BDNF是否参与电针镇痛。方法 SD大鼠分为正常组(N组),模型组(M组),电针组(EA组),每组10只。EA组于第6周开始电针双侧足三里和昆仑穴,每次30 min,隔日1次,干预7次。分别检测各组大鼠的基础(base)、4周(4 weeks)、6周(6 weeks)、8周(8 weeks)空腹血糖(fasting blood glucose,FBG)、热痛阈(thermal paw withdrawal latency,PWL)和机械痛阈(paw withdrawal thresholds,PWT)变化;于8 weeks应用免疫荧光法检测大鼠L4-L6脊髓背角小胶质细胞和BDNF蛋白的表达。结果 (1) 6 weeks、8 weeks时,M组和EA组FBG较N组显著升高,EA组FBG较M组无明显变化;(2) 6 weeks、8 weeks时,M组PWL和PWT较N组显著下降; 8 weeks时,EA组PWL和PWT较M组显著升高; 6 weeks时,EA组PWL和PWT与M组无明显差异;(3) M组大鼠L4-L6脊髓背角CD11b(小胶质细胞标记物)和BDNF平均光密度值较N组显著升高,EA组大鼠L4-L6脊髓背角CD11b(小胶质细胞标记物)和BDNF平均光密度值较M组显著下降。结论脊髓背角小胶质细胞和BDNF可能参与了大鼠糖尿病神经痛的产生与维持,电针可能通过减少DNP大鼠脊髓背角小胶质细胞表达和BDNF的表达产生镇痛作用。     

Nanoparticle-encapsulated emodin decreases diabetic neuropathic pain probably via a mechanism involving P2X3 receptor in the dorsal root ganglia

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes mellitus (DM). More than 90% of all cases of DM belong to type 2 diabetes mellitus (T2DM). Emodin is the main active component of Radix et rhizoma rhei and has anti-bacterial, anti-viral, anti-ulcerogenic, anti-inflammatory, and anti-cancer effects. Nanoparticle encapsulation of drugs is beneficial for drug targeting and bioavailability as well as for lowering drug toxicity side effects. The aim of this study was to investigate the effects of nanoparticle-encapsulated emodin (nano emodin) on diabetic neuropathic pain (DNP) mediated by the Purin 2X3 (P2X3) receptor in the dorsal root ganglia (DRG). Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) values in T2DM rats were lower than those of control rats. MWT and TWL in T2DM rats treated with nano emodin were higher compared with those in T2DM rats. Expression levels of P2X3 protein and messenger RNA (mRNA) in the DRG of T2DM rats were higher than those of controls, while levels in T2DM rats treated with nano emodin were significantly lower than those of the T2DM rats. Phosphorylation and activation of ERK1/2 in the T2DM DRG were decreased by nano emodin treatment. Nano emodin significantly inhibited currents activated by the P2X3 agonist α,β-meATP in HEK293 cells transfected with the P2X3 receptor. Therefore, nano emodin treatment may relieve DNP by decreasing excitatory transmission mediated by the DRG P2X3 receptor in T2DM rats.     

Cav-1 participates in the development of diabetic neuropathy pain through the TLR4 signaling pathway

This study aims to determine whether caveolin-1 (Cav-1) participates in the process of diabetic neuropathic pain by directly regulating the expression of toll-like receptor 4 (TLR4) and the subsequent phosphorylation of N-methyl-D-aspartate receptor 2B subunit (NR2B) in the spinal cord. Male Sprague-Dawley rats (120–150 g) were continuously fed with high-fat and high-sugar diet for 8 weeks, and received a single low-dose of intraperitoneal streptozocin injection in preparation for the type-II diabetes model. Then, these rats were divided into five groups according to the level of blood glucose, and the mechanical withdrawal threshold and thermal withdrawal latency values. The pain thresholds were measured at 3, 7, and 14 days after animal grouping. Then, eight rats were randomly chosen from each group and killed. Lumbar segments 4–6 of the spinal cord were removed for western blot analysis and immunofluorescence assay. Cav-1 was persistently upregulated in the spinal cord after diabetic neuropathic pain in rats. The downregulation of Cav-1 through the subcutaneous injection of Cav-1 inhibitor daidzein ameliorated the pain hypersensitivity and TLR4 expression in the spinal cord in diabetic neuropathic pain (DNP) rats. Furthermore, it was found that Cav-1 directly bound with TLR4, and the subsequent phosphorylation of NR2B in the spinal cord contributed to the modulation of DNP. These findings suggest that Cav-1 plays a vital role in DNP processing at least in part by directly regulating the expression of TLR4, and through the subsequent phosphorylation of NR2B in the spinal cord.     

The effect of sinomenine in diabetic neuropathic pain mediated by the P2X<Subscript>3</Subscript> receptor in dorsal root ganglia

Type 2 diabetes mellitus (T2DM) accounts for more than 90% of all cases of diabetes mellitus (DM). Diabetic neuropathic pain (DNP) is a common complication of T2DM. Sinomenine is a natural bioactive component extracted from the Sinomenium acutum and has anti-inflammatory effects. The aim of our study was to investigate the effects of sinomenine on DNP mediated by the P2X₃ receptor in dorsal root ganglia (DRG). The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) in T2DM rats were lower than those of control rats. MWT and TWL in T2DM rats treated with sinomenine were higher compared with those in T2DM rats. The expression levels of the P2X₃ protein and mRNA in T2DM rat DRG were higher compared with those of the control, while those in T2DM rats treated with sinomenine were significantly lower compared with those of the T2DM rats. Sinomenine significantly inhibited P2X₃ agonist ATP-activated currents in HEK293 cells transfected with the P2X₃ receptor. Sinomenine decreased the phosphorylation and activation of P38MAPK in T2DM DRG. Therefore, sinomenine treatment may suppress the up-regulated expression and activation of the P2X₃ receptor and relieve the hyperalgesia potentiated by the activation of P38MAPK in T2DM rats.     

Suberoylanilide Hydroxamic Acid Triggers Autophagy by Influencing the mTOR Pathway in the Spinal Dorsal Horn in a Rat Neuropathic Pain Model

Histone acetylation levels can be upregulated by treating cells with histone deacetylase inhibitors (HDACIs), which can induce autophagy. Autophagy flux in the spinal cord of rats following the left fifth lumber spinal nerve ligation (SNL) is involved in the progression of neuropathic pain. Suberoylanilide hydroxamic acid (SAHA), one of the HDACIs can interfere with the epigenetic process of histone acetylation, which has been shown to ease neuropathic pain. Recent research suggest that SAHA can stimulate autophagy via the mammalian target of rapamycin (mTOR) pathway in some types of cancer cells. However, little is known about the role of SAHA and autophagy in neuropathic pain after nerve injury. In the present study, we aim to investigate autophagy flux and the role of the mTOR pathway on spinal cells autophagy activation in neuropathic pain induced by SNL in rats that received SAHA treatment. Autophagy-related proteins and mTOR or its active form were assessed by using western blot, immunohistochemistry, double immunofluorescence staining and transmission electron microscopy (TEM). We found that SAHA decreased the paw mechanical withdrawal threshold (PMWT) of the lower compared with SNL. Autophagy flux was mainly disrupted in the astrocytes and neuronal cells of the spinal cord dorsal horn on postsurgical day 28 and was reversed by daily intrathecal injection of SAHA (n?=?100 nmol/day or n?=?200 nmol/day). SAHA also decreased mTOR and phosphorylated mTOR (p-mTOR) expression, especially p-mTOR expression in astrocytes and neuronal cells of the spinal dorsal horn. These results suggest that SAHA attenuates neuropathic pain and contributes to autophagy flux in astrocytes and neuronal cells of the spinal dorsal horn via the mTOR signaling pathway.

     

MiR‐101 promotes pain hypersensitivity in rats with chronic constriction injury via the MKP‐1 mediated MAPK pathway

This study was performed to characterize the effect of microRNA‐101 (miR‐101) on the pain hypersensitivity in CCI rat models with the involvement of mitogen‐activated protein kinase phosphatase 1 (MKP‐1) in spinal cord microglial cells. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) in the developed CCI models were determined to assess the hypersensitivity of rats to mechanical stimulation and thermal pain. To assess inflammation, the levels of interleukin (IL)‐1β, IL‐6 and tumour necrosis factor‐α (TNF‐α) in the spinal dorsal horns of CCI rats and lipopolysaccharide (LPS)‐activated microglial cells were examined. miR‐101 and MKP‐1 gain‐ and loss‐of‐function experiments were conducted in in vivo and in vitro settings to examine the roles of miR‐101 and MKP‐1 in CCI hypersensitivity and inflammation. The results showed that miR‐101 was highly expressed in the spinal dorsal horn and microglial cells of CCI rat models. Furthermore, overexpression of miR‐101 promoted the pain hypersensitivity in CCI rat models by reducing MWT and TWL. The overexpression of miR‐101 also promoted inflammation in LPS‐exposed microglial cells, as indicated by increased levels of IL‐1β, IL‐6 and TNF‐α. MiR‐101 was shown to target MKP‐1, inhibiting its expression. Moreover, miR‐101 promoted pain hypersensitivity in CCI rat models by inhibiting MKP‐1 expression and activating the mitogen‐activated protein kinase (MAPK) signalling pathway. Taken together, miR‐101 could potentially promote hypersensitivity and inflammatory response of microglial cells and aggravate neuropathic pain in CCI rat models by inhibiting MKP‐1 in the MAPK signalling pathway.     

Regulation of increased glutamatergic input to spinal dorsal horn neurons by mGluR5 in diabetic neuropathic pain

Diabetic neuropathic pain is associated with increased glutamatergic input in the spinal dorsal horn. Group I metabotropic glutamate receptors (mGluRs) are involved in the control of neuronal excitability, but their role in the regulation of synaptic transmission in diabetic neuropathy remains poorly understood. Here we studied the role of spinal mGluR5 and mGluR1 in controlling glutamatergic input in a rat model of painful diabetic neuropathy induced by streptozotocin. Whole-cell patch-clamp recordings of lamina II neurons were performed in spinal cord slices. The amplitude of excitatory post-synaptic currents (EPSCs) evoked from the dorsal root and the frequency of spontaneous EPSCs (sEPSCs) were significantly higher in diabetic than in control rats. The mGluR5 antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) inhibited evoked EPSCs and sEPSCs more in diabetic than in control rats. Also, the percentage of neurons in which sEPSCs and evoked EPSCs were affected by MPEP or the group I mGluR agonist was significantly higher in diabetic than in control rats. However, blocking mGluR1 had no significant effect on evoked EPSCs and sEPSCs in either groups. The mGluR5 protein level in the dorsal root ganglion, but not in the dorsal spinal cord, was significantly increased in diabetic rats compared with that in control rats. Furthermore, intrathecal administration of MPEP significantly increased the nociceptive pressure threshold only in diabetic rats. These findings suggest that increased mGluR5 expression on primary afferent neurons contributes to increased glutamatergic input to spinal dorsal horn neurons and nociceptive transmission in diabetic neuropathic pain.