外周炎症性疼痛刺激诱导大鼠中脑导水管周围灰质胶质细胞激活及细胞因子的表达

目的观察完全弗氏佐剂(CFA)外周刺激后,大鼠中脑导水管周围灰质(PAG)中胶质纤维酸性蛋白(GFAP)、小胶质细胞标记物(Iba)以及细胞因子IL-β、TNF-α的表达变化。方法结合行为学检测,反转录-聚合酶链式反应(RT-PCR)、Western blotting以及免疫组织化学的方法,观察了大鼠后爪注射CFA后疼痛感觉的变化,并检测了PAG中上述标记物和细胞因子在基因水平和蛋白水平的表达变化。结果注射CFA后,注射侧后爪出现热痛过敏和机械性触诱发痛;大鼠的热痛过敏14d基本恢复正常,但机械性触诱发痛持续到21d时仍未恢复正常;星形胶质细胞标记物GFAP在急性期和慢性期有显著增加;小胶质细胞的标记物CD14、细胞因子(IL-β、TNF-α)在急性期、亚急性期和慢性期均有增加。结论小胶质细胞的激活可能与炎性疼痛的起始相关,而星形胶质细胞可能与疼痛的维持相关,细胞因子表达的增加可能对痛觉过敏的发生起重要作用。     

雷公藤内酯醇(T10)通过抑制脊髓内胶质细胞的激活改善大鼠CFA诱导的炎性痛的机制研究

目的:观察腹腔注射雷公藤内酯醇(Triptolide,T10)对完全弗氏佐剂(complete Freund’s adjuvant,CFA)诱导的大鼠慢性炎性痛行为的改善作用并探讨其机制。方法:SD大鼠随机分为四组,即Saline+Veh组、Saline+T10组、CFA+Veh组和CFA+T10组。后两组大鼠于右侧足底注射CFA制备大鼠慢性炎性痛模型,前两组则在相同部位注射生理盐水。第二组和第四组大鼠分别于造模前1 h给予T10腹腔注射,随后每12 h给予腹腔注射药物1次,持续用药7 d;第一组和第三组则以相同方式给予100 ml/kg的生理盐水作为对照。采用辐射热法和机械刺激法连续观察给药后大鼠的痛行为;应用免疫组织化学染色和Western Blot方法观察连续给予T10 3d和7 d后大鼠腰膨大平面脊髓背角内小胶质细胞和星形胶质细胞的活化程度;应用实时定量PCR(RT-PCR)方法观察连续给药7 d后大鼠腰5背根神经节内炎性因子,如白细胞介素-6(interleukin-6,IL-6)、白细胞介素-1β(interleukin-1 beta,IL-1β)和肿瘤坏死因子-α(tumour necrosis factor-α,TNF-α)的表达变化。结果:(1)与CFA+Veh组相比,CFA+T10组大鼠机械缩足阈值及辐射热痛潜伏期显著下降(P0.05),并持续到造模成功后7 d,表明腹腔注射T10可以明显改善CFA诱导的大鼠机械痛敏和辐射热痛敏。(2)免疫组织化学染色和Western Blot结果显示:造模后3 d和7 d后CFA+Veh组大鼠脊髓背角出现大量CFA诱导活化的小胶质细胞和星形胶质细胞;小胶质细胞标记物IBa-1和星形胶质细胞标记物GFAP的表达量分别在CFA造模后3 d和7 d显著增高(P0.05),而给予T10 3 d和7 d后炎性痛大鼠腰膨大平面IBa-1和GFAP的活化程度均显著减轻(P0.05)。(3)RT-PCR结果显示:与Saline+Veh组相比,CFA造模7 d后腰5背根神经节内炎性因子IL-1β、IL-6 mRNA和TNF-αmRNA的表达显著增高(P0.05),腹腔注射T10 7 d后上述炎性因子的表达则显著降低(P0.05)。结论:腹腔注射T10可以显著改善CFA诱导的大鼠慢性炎性痛,其机制可能与抑制脊髓背角小胶质细胞和星形胶质细胞的活化以及炎性因子IL-1β、IL-6和TNF-α的合成有关。     

外周炎症性疼痛刺激诱导丘脑中胶质细胞激活及细胞因子的表达

目的:研究完全弗氏佐剂(CFA)外周刺激后,大鼠丘脑中线核群和板内核群中星形胶质细胞标记物(GFAP)、小胶质细胞标记物(Iba)以及细胞因子(IL-1β,TNF-α)的表达变化.方法:逆转录聚合酶链式反应(RT-PCR),免疫印迹法,免疫组织化学.结果:在炎症刺激后的4 h、3 d和14 d,丘脑中线核群和板内核群中小胶质细胞的标记物CD14、细胞因子IL-1β,TNF-α的mRNA和蛋白均有增加;星形胶质细胞标记物GFAP在炎症后的3 d和14 d,其mRNA和蛋白有显著增加.结论:外周炎症性刺激能够相继激活丘脑中线核群和板内核群的小胶质细胞和星形胶质细胞,并使炎症前细胞因子表达增多.提示该部位的胶质细胞可能通过细胞因子参与对炎症性疼痛的调节.     

外周注射福尔马林诱导前扣带皮层中胶质细胞激活和细胞因子表达增高

为了观察外周注射福尔马林对大鼠前扣带皮层(ACC)中星形胶质细胞标记物胶质纤维酸性蛋白(GFAP)和S100B,小胶质细胞标记物CD14以及与胶质细胞密切相关的炎症前细胞因子白介素1β(IL-1β)、肿瘤坏死因子α(TNF-α)表达的影响,本研究结合行为学检测和RT-PCR方法,观察了大鼠单侧足底皮下注射福尔马林后的行为学变化,并检测了在不同时间点ACC中GFAP、S100B、CD14、IL-1β和TNF-α在基因水平的表达变化。结果显示:福尔马林急性疼痛刺激的大鼠出现典型的双时相自发性疼痛反应。ACC中GFAP和S100B mRNAs表达水平在刺激后30min、1h增高,2h恢复正常;CD14 mRNA表达水平在15min开始增高,1h达到高峰,6h恢复正常;IL-1β和TNF-αmRNAs表达水平在刺激后30min、1h、2h增高,6h恢复正常。上述结果表明,福尔马林外周急性伤害性刺激能够诱导ACC内短暂性的星形胶质细胞、小胶质细胞激活及IL-1β、TNF-α表达增高,提示激活的胶质细胞及表达上调的炎症前细胞因子可能参与伤害性信息的调制。     

慢性痛大鼠模型前扣带皮层内小胶质细胞活化与细胞因子表达

目的:观察慢性炎症性疼痛大鼠前扣带皮层(ACC)中小胶质细胞标记物(CD14,IBA1)及促炎症细胞因子(IL-1β,TNF-α)的表达变化。方法:单侧足底注射完全弗氏佐剂(CFA)诱导大鼠慢性炎症性疼痛,用RT-PCR检测ACC中CD14、IL-1β、TNF-αmRNA的表达,用免疫组织化学染色观察ACC中IBA1免疫阳性小胶质细胞的变化。结果:足底注射CFA后4 h、3 d双侧ACC中CD14 mRNA表达较生理盐水(NS)组有显著增加(P<0.001);CFA后4 h、3 d、14 d双侧ACC中IL-1βmRNA表达较NS组有显著增加(P<0.001);CFA后3 d、14 d双侧ACC中TNF-αmRNA表达较NS组有显著增加(P<0.001)。CFA 3 d组双侧ACC中IBA1免疫阳性小胶质细胞胞体变大、突起变粗。结论:ACC中小胶质细胞的活化以及IL-1β和TNF-α的表达增加可能在慢性炎症性疼痛的产生和维持中发挥作用。     

8-O-乙酰山栀子苷甲酸通过抑制脊髓背角JNK的磷酸化水平改善大鼠炎性痛的研究

目的:探究8-O-乙酰山栀子苷甲酸(8-O-acetyl-SM,8-Oa S)对于慢性炎性痛模型大鼠痛行为及脊髓背角星形胶质细胞内c-Jun氨基酸末端激酶(c-Jun N-terminal kinase,JNK)磷酸化水平的影响。方法:运用大鼠足底注射完全弗式佐剂(complete Freund’s adjuvant,CFA)的方法建立慢性炎性痛模型;通过腹膜腔注射8-Oa S进行干预;采用von Frey丝测定大鼠足底50%机械性缩足反射阈值;应用免疫荧光组织化学染色法观察大鼠腰膨大节段脊髓背角胶质纤维酸性蛋白(glial fibrillary acidic protein,GFAP)及磷酸化的JNK(phosphorylatedc-Jun N-terminal kinase,p JNK)表达;应用Western Blot方法对大鼠脊髓背角内GFAP、JNK以及p-JNK的表达水平进行定量分析。结果:(1)行为学结果显示:与对照组相比,CFA模型大鼠机械性痛阈明显降低(P0.01),腹膜腔注射8-Oa S可有效提高CFA诱导的机械性痛阈值(P0.05);(2)免疫荧光染色结果显示:CFA模型脊髓背角内GFAP的表达量明显高于正常组,且p JNK基本表达于星形胶质细胞内;(3)Western Blot结果显示:与对照组相比,CFA造模后7 d脊髓背角内GFAP和p JNK表达明显上调,腹膜腔给予8-Oa S可以显著下调CFA诱导的脊髓背角内GFAP和p JNK的水平(P0.01)。结论:腹膜腔内给予8-Oa S可有效提高炎性痛大鼠的机械性痛阈,其机制是通过下调脊髓背角星形胶质细胞内JNK信号通路的磷酸化水平进而抑制星形胶质细胞的激活。     

Notch3信号介导小胶质细胞活化在慢性前列腺炎疼痛中的作用

目的观察Notch3介导L5~S2脊段背角小胶质细胞活化在慢性前列腺炎疼痛中的作用。方法大鼠分为实验组(慢性前列腺炎组)和对照组,实验组通过完全弗氏佐剂(CFA)注射前列腺来制作大鼠慢性前列腺炎疼痛模型,对照组注射生理盐水,采用热辐射甩尾痛阈测定和前列腺组织病理学检查鉴定疼痛模型,分别在注射CFA后0、4、12、24 d,采用qRT-PCR检测L5~S2脊段后角小胶质细胞活化标志物IBA-1和受体Notch3 mRNA的表达,采用ELISA检测小胶质细胞炎症因子TNF-α和IL-1β的分泌,并在鞘内注射小胶质细胞和Notch3抑制剂后检测小胶质细胞TNF-α和IL-1β蛋白的表达。结果前列腺组织病理和热痛域实验证实慢性前列腺炎疼痛模型建立成功。实验组大鼠Notch3、IBA-1、TNF-α及IL-1β的表达在第4天开始增加,第12天达到最高水平,第24天开始下降,均显著高于对照组,差异有极显著性统计学意义(P<0.01)。抑制小胶质细胞和Notch3受体后,TNF-α和IL-1β的分泌明显减少(P<0.05)。结论慢性前列腺炎疼痛中Notch3介导L5~S2脊段中枢小胶质细胞活化,炎症因子分泌增加,与慢性前列腺炎呈现的持续顽固神经炎性疼痛有关。     

葛根素通过抑制脊髓胶质细胞活化和炎症反应治疗腰椎间盘突出症引起的神经根性疼痛（英文）

目的:从脊髓胶质细胞活化和炎症反应角度探究中药葛根素在治疗大鼠神经根性疼痛中的作用及机制。方法:用自体髓核(NP)移植方法复制大鼠腰椎间盘突出症模型,假手术组行同样手术但不进行NP移植。治疗组大鼠术前1 h开始腹腔注射不同浓度(50、100和150 mg/kg)葛根素注射液,每天1次,连续7 d。机械性缩爪阈值(PWT)检测法评价大鼠痛行为。免疫荧光染色法检测小胶质细胞和星形胶质细胞活化情况。ELISA检测脊髓抗炎和致炎细胞因子的含量。结果:与假手术组相比,NP移植后3～14 d,大鼠的PWT明显下降。与溶剂对照组相比,100 mg/kg和150 mg/kg的葛根素明显增加NP组大鼠的PWT,缓解疼痛症状。葛根素明显降低小胶质细胞标志物离子钙结合接头分子1和星形细胞标志物胶质细胞原纤维酸性蛋白的表达,并且降低致炎细胞因子肿瘤坏死因子α、白细胞介素1β(IL-1β)和IL-6的含量,增加抗炎细胞因子IL-10的含量(P 0. 01)。结论:葛根素通过抑制脊髓胶质细胞活化和炎症反应治疗腰椎间盘突出症诱导的神经根性疼痛。     

石菖蒲挥发油对炎症痛大鼠基底外侧杏仁核中胶质纤维酸性蛋白和即刻早期基因表达的影响

目的 通过注射完全弗氏佐剂(CFA)构建炎症痛大鼠模型,探讨石菖蒲挥发油对炎症痛大鼠基底外侧杏仁核(BLA)中神经胶质纤维酸性蛋白(GFAP)和即刻早期基因(c-fos)表达的影响。方法 成年SD雄性大鼠36只,随机分为6组: 对照（control）组、假手术（sham）组、CFA组、CFA+5 g/(kg ·d)石菖蒲挥发油组、CFA+10 g/(kg ·d)石菖蒲挥发油组、CFA+20 g/(kg ·d)石菖蒲挥发油组,每组各6只动物,于灌胃21 d后取材。采用免疫荧光及Western blotting技术检测各组大鼠BLA中GFAP和c-fos表达量的变化。结果 免疫荧光及Western blotting结果均显示,与control组相比,CFA组大鼠BLA中GFAP及c-fos阳性表达均显著增多(P<0.01);与CFA组相比,石菖蒲挥发油处理组GFAP和c-fos阳性表达均降低,且表达量呈剂量依赖性递减(P<0.01);其中,高剂量组GFAP和c-fos阳性表达的下降趋势较低剂量组相比更为显著(P<0.01)。结论 石菖蒲挥发油可减少CFA诱导的炎症性疼痛大鼠BLA中星形胶质细胞表达,并进一步抑制c-fos的表达。     

曲古抑菌素A通过抑制脊髓背角内的炎症反应减轻大鼠神经病理性痛

目的:观察曲古抑菌素A (TSA)对脊神经结扎(SNL)大鼠镇痛效果及分子机制。方法:40只健康雄性Sprague Dawley(SD)大鼠随机分为假手术组(sham)、曲古抑菌素A处理组(TSA)、脊神经结扎组(SNL)和SNL+TSA组(SNL+TSA)。采用L5脊神经结扎(SNL)的方法建立神经病理性痛模型,鞘内注射TSA进行干预,通过von Frey丝和热板实验检测大鼠的痛敏,应用免疫荧光染色方法观察大鼠脊髓背角内HDAC1的表达情况;应用Western Blot方法观察大鼠脊髓背角内胶质纤维酸性蛋白(GFAP)和离子钙接头蛋白分子1(Iba-1)的表达水平;应用real time RT-PCR方法检测大鼠脊髓背角内TNF-α、IL-1β和IL-6的mRNA表达水平。结果:SNL模型大鼠术后机械性痛阈值和热痛阈值均显著降低(P 0.05),鞘内给予TSA能够明显缓解大鼠患侧后足机械性痛敏和热痛敏; SNL模型大鼠脊髓背角内HDAC1的表达较对照组明显增加,而鞘内注射TSA可显著抑制其表达; SNL术后脊髓背角内GFAP和Iba-1的表达显著升高(P 0.05),鞘内给予TSA能够明显下调GFAP和Iba-1的表达; SNL术后大鼠脊髓背角内TNF-α、IL-1β和IL-6的表达较对照组明显上调(P 0.05),而鞘内给予TSA能够显著逆转这一趋势。结论:鞘内给予TSA能够通过抑制脊髓HDAC1表达缓解大鼠神经病理性痛。     

Antihyperalgesic and antiallodynic effect of sirolimus in neuropathic pain and the role of cytokines in this effect

Recent studies have revealed that T lymphocytes play a role in neuropathic pain following nerve injury in rats through releasing several cytokines. Sirolimus is an immunosuppressive antibiotic inhibiting T cell activation. This study aimed to determine the effect of sirolimus on hyperalgesia and allodynia and on serum and spinal cord TNF-α, IL-1β and IL-6 levels in rat neuropathic pain. Neuropathic pain was induced by loose ligation of the sciatic nerve and evaluated by tests measuring the mechanical hyperalgesia and allodynia. Sirolimus (0.75 and 1.5 mg/kg) was administered intraperitoneally once every 3 days for 2 weeks (7 doses totally). This dosing regimen revealed acceptable blood concentrations in neuropathic rats. Chronic constriction injury of the sciatic nerve resulted in hyperalgesia and allodynia. Serum levels of cytokines remained unchanged in neuropathic rats. However, TNF-α, but not IL-1β or IL-6, protein level was increased in the spinal cord tissue as evaluated by Western blotting analysis. Treatment with sirolimus resulted in antihyperalgesic and antiallodynic effects and prevented the increased spinal cord TNF-α level. It seems that sirolimus could be a promising immunosuppressive agent in the treatment of neuropathic pain.     

Differential regional expression patterns of α-synuclein, TNF-α, and IL-1β; and variable status of dopaminergic neurotoxicity in mouse brain after Paraquat treatment

Background

During inflammation, immune cells accumulate in damaged areas and release pro-inflammatory cytokines and neurotrophins. Brain-derived neurotrophic factor (BDNF) plays a neuromodulatory role in spinal cord dorsal horn via the post-synaptic tyrosine protein kinase B (trkB) receptor to facilitate pain transmission. However, the precise role of BDNF and trkB receptor in the primary sensory neurons of dorsal root ganglia (DRG) during inflammation remains to be clarified. The aim of this study was to investigate whether and how BDNF-trkB signaling in the DRG is involved in the process of inflammatory pain.

Methods

We used complete Freund's adjuvant- (CFA-) induced and tumor necrosis factor-α- (TNF-α-) induced inflammation in rat hindpaw as animal models of inflammatory pain. Quantification of protein and/or mRNA levels of pain mediators was performed in separate lumbar L3-L5 DRGs. The cellular mechanism of TNF-α-induced BDNF and/or trkB receptor expression was examined in primary DRG cultures collected from pooled L1-L6 DRGs. Calcitonin gene-related peptide (CGRP), BDNF and substance P release were also evaluated by enzyme immunoassay.

Results

CFA injection into rat hindpaw resulted in mechanical hyperalgesia and significant increases in levels of TNF-α in the inflamed tissues, along with enhancement of BDNF and trkB receptor as well as the pain mediators CGRP and transient receptor potential vanilloid receptor subtype 1 (TRPV1) in DRG. Direct injection of TNF-α into rat hindpaw resulted in similar effects with retrograde transport of TNF-α along the saphenous nerve to DRG during CFA-induced inflammation. Primary DRG cultures chronically treated with TNF-α showed significant enhancement of mRNA and protein levels of BDNF and trkB receptor, BDNF release and trkB-induced phospho-ERK1/2 signal. Moreover, CGRP and substance P release were enhanced in DRG cultures after chronic TNF-α treatment or acute BDNF stimulation. In addition, we found that BDNF up-regulated trkB expression in DRG cultures.

Conclusions

Based on our current experimental results, we conclude that inflammation and TNF-α up-regulate the BDNF-trkB system in DRG. This phenomenon suggests that up-regulation of BDNF in DRG may, in addition to its post-synaptic effect in spinal dorsal horn, act as an autocrine and/or paracrine signal to activate the pre-synaptic trkB receptor and regulate synaptic excitability in pain transmission, thereby contributing to the development of hyperalgesia.     

Changes in intramuscular cytokine levels during masseter inflammation in male and female rats

The present study was conducted to examine cytokine profiles in the masseter muscle before and after complete Freund's adjuvant (CFA)-induced inflammation and possible sex differences in the cytokine levels. Age matched male and female Sprague Dawley rats were injected with CFA in the mid-region of the masseter muscle. Muscle tissue surrounding the injection site was extracted 6 h, 1, 3 and 7 days after the injection to measure TNF-α, IL-1β, IL-6 and IL-4 levels with Luminex multi-analyte profiling (xMAP) technology. The cytokine levels were compared to those obtained from naïve rats. CFA injection into the masseter muscle led to a significant time effect in the level of TNF-α compared to that of naïve rats. The pattern of changes in TNF-α level after CFA injection was significantly different between the male and female rats owing to the differences in basal levels. CFA injection induced significant time-dependent increases in the levels of IL-1β and IL-6 in the masseter muscle in both male and female rats. The level of IL-4 was slightly, but significantly, reduced in both sexes at 6 h and 3 days after CFA-induced inflammation. No significant sex differences were observed in the levels of IL-1β, IL-6 or IL-4. The results provided novel information about distinct cytokine profiles during CFA-induced muscle inflammation, and the basis for further pursuing contributions of each cytokine in pain processing and analgesic responses in both sexes.     

Characteristics and classification of hippocampal theta rhythm induced by passive translational displacement

Painful peripheral neuropathy induced by chronic ethanol consumption is a major medico-socioeconomical problem. The objective of present investigation was to study the effect of curcumin (20, 40 and 80mg/kg; p.o.) in alcohol-induced neuropathy in rats. Ethanol (35% v/v, 10g/kg; p.o.) was administered for 10 weeks which showed a significant decrease in thermal hyperalgesia, mechanical hyperalgesia, mechanical allodynia and nerve conduction velocity. It caused enhanced malondialdehyde, oxidative-nitrosative stress, total calcium levels, inflammatory mediators (TNF-α and IL-1β levels) along with DNA damage. Co-administration of curcumin and α-tocopherol for 10 weeks significantly and dose-dependently improved nerve functions, biochemical as well as molecular parameters and DNA damage in sciatic nerve of ethanol treated rats. Hence, it was concluded that curcumin is of potent therapeutic value in the amelioration of alcoholic neuropathy in rats and acts by inhibition of pro-inflammatory mediators like TNF-α and IL-1β.     

Inflammation of craniofacial muscle induces widespread mechanical allodynia

The modulation of behavioral responses evoked by local and distant nociceptive stimuli following a discrete somatic injection of complete Freund's adjuvant (CFA) was examined in rats. Inflammation of one craniofacial muscle evoked mechanical allodynia not only in the region of inflammation but also secondary mechanical allodynia in the contralateral head, ipsilateral hindpaw, and contralateral hindpaw. In contrast to this, CFA-induced inflammation of either the hindpaw or gastrocnemius muscle evoked mechanical allodynia restricted to the hindlimb region. The widespread modulation of nocifensive behavior evoked by inflammation of deep craniofacial tissue found in this study resembles the widespread deep tissue pain reported in fibromyalgia, whiplash injury and some temporomandibular disorders and thus may provide insight into the mechanisms of these musculoskeletal pathologies.     

Persistent monoarthritis of the temporomandibular joint region enhances nocifensive behavior and lumbar spinal Fos expression after noxious stimulation to the hindpaw in rats

Effects of persistent temporomandibular joint (TMJ) inflammation on nociceptive responses of remote bodily areas of the rat were investigated. Monoarthritis of the TMJ region was evoked by the injection of complete Freund’s adjuvant (CFA) into the left TMJ region. Rats without injection of CFA into the TMJ region served as controls (non-CFA group). Time spent on licking behavior evoked by the injection of formalin into the left hindpaw and withdrawal thresholds of mechanical stimulation to both sides of the hindpaw were measured during TMJ inflammation for 3 weeks. Furthermore, expression of Fos protein in the lumbar dorsal horn was immunohistochemically investigated following the injection of formalin into the hindpaw during TMJ inflammation. Formalin-evoked nocifensive behavioral activities were significantly enhanced at 10 and 14 days after CFA injection in the late phase, while the withdrawal threshold to mechanical stimulation was significantly decreased bilaterally at 8, 10 and 14 days after CFA injection. Both formalin-evoked licking behavior and mechanical withdrawal thresholds to bilateral hindpaw at 21 days after CFA injection were similar to those in the non-CFA group. The number of Fos-positive neurons in the lumbar dorsal horn ipsilateral to the formalin injection at 1 and 7 days after CFA injection into the TMJ were similar to those in the non-CFA group; however, those were significantly increased in the laminae I–II and V–VI of the lumbar dorsal horn at 14 days after CFA injection. TMJ inflammation for 7 and 14 days alone produced a small number of Fos-expressing neurons in the lumbar dorsal horn. These results provide evidence that persistent unilateral inflammation of the TMJ region causes an increase in behavioral hyperalgesia of the hindpaw, which is attributed to the modulation of neural activities, in part, in the lumbar dorsal horn, likely mediated by supraspinal neural mechanisms.     

Role of the Na+-K+-2Cl- cotransporter in the development of capsaicin-induced neurogenic inflammation

Recent behavioral and electrophysiological studies have attributed an important role to dorsal root reflexes (DRRs) in the initiation and development of neurogenic inflammation produced by intradermal capsaicin (CAP). The DRRs can occur in peptidergic fibers, resulting in peripheral release of neuromediators that produce vasodilation, plasma extravasation and subsequently hyperalgesia and allodynia. In this study, we have evaluated the effect of spinal administration of bumetanide (a blocker of the Na+-K+-2Cl- cotransporter, NKCC) on DRR activity, changes in cutaneous blood flow (vasodilation), hindpaw edema, mechanical allodynia, and hyperalgesia induced by intradermal injection of 1% CAP in Sprague-Dawley rats. Vasodilation was monitored using laser Doppler flowmetry, neurogenic edema was evaluated by measurements of hindpaw volume, and secondary mechanical allodynia and hyperalesia were tested using von Frey filaments (10 and 200 mN) applied to the plantar surface of the paw. Changes in the blood flow were blocked significantly by intrathecal bumetanide at 10 and 100 microM in both pre- and posttreatment studies. Spinal bumetanide at 10 and 100 microM blocked neurogenic edema when it was administered before CAP injection, but only bumetanide at 100 microM administered after CAP injection reduced the paw edema significantly. Furthermore, the administration of bumetanide onto the spinal cord reduced the increment in DRR activity produced by CAP. Finally, both secondary mechanical allodynia and hyperalesia were reduced by bumetanide at 1, 10, and 100 microM. Taken together these results suggest that NKCC is involved in the increases in DRR activity, neurogenic inflammation and hyperalgesia and allodynia induced by intradermal CAP.     

Effects of repeated administered ghrelin on chronic constriction injury of the sciatic nerve in rats

Chronic constriction injury (CCI) is a peripheral mononeuropathic pain model that is caused by an injury to the peripheral nervous system and refractory to available conventional treatment. Mechanisms involved in neuropathic pain are still unclear. Previous studies reveal that proinflammatory cytokines contribute to CCI-induced peripheral nerve pathology. Ghrelin, a novel identified gastric peptide, has been shown to have antinociceptive activity and also anti-inflammatory properties by decreasing proinflammatory cytokines. Therefore, the aim of the present study was to investigate the effects of ghrelin on the CCI and its relationship with proinflammatory cytokines in rats. Wistar rats underwent sciatic nerve ligation to induce CCI fallowed by repeated ghrelin administrations (50 and 100 μg/kg i.p., once daily) for a period of 14 days. Mechanical hyperalgesia was assessed before surgery and at day 14 after CCI. TNF-α, IL-1β and IL-6 were measured in blood and spinal cord. The changes of sciatic nerve was assessed histologically by both light and electron microscopy. Ghrelin attenuated mechanical hyperalgesia, reduced spinal TNF-α and IL-1β levels and enhanced sciatic nerve injury with correlated morphometric recovery. These results indicate that the protective effect by ghrelin in the spinal cord is mediated through the suppression of TNF-α and IL-1β. Thus ghrelin may be a promising peptide in the management of neuropathic pain.