川芎嗪对紫杉醇致神经病理性疼痛大鼠的疗效及其对坐骨神经中神经生长因子表达的影响

目的探讨川芎嗪对紫杉醇致神经病理性疼痛大鼠的疗效及其对坐骨神经中神经生长因子(NGF)表达的影响。方法成年雄性SD大鼠30只随机分为A组(对照组,n=6)、B组(n=8)、C组(n=8)、D组(n=8)。以首次给药为d1,实验前一日为d0,各组分别在d1、d3、d5、d7腹腔注入2.0 mg/(kg·d)紫杉醇。于d1~d14,B组腹腔注入川芎嗪200 mg/(kg·d),C组口服普瑞巴林3 mg/(kg·d),D组同时腹腔注射川芎嗪和口服普瑞巴林,剂量同B组、C组。分别于d0和d7、d12、d16、d20测定大鼠的机械缩足反射阈值(MWT)和热缩足潜伏期(TWL)。采用透射电镜观察各组大鼠坐骨神经的超微结构,用免疫组化法检测大鼠坐骨神经中NGF的表达。结果 4组大鼠d0时后肢MWT差异无统计学意义(均P0.05);D组大鼠d7~d20时后肢平均MWT与A组及C组相比明显升高(均P0.05);B、C组大鼠d12~d20时后肢MWT与A组相比明显升高(均P0.05);B组d12、d16时MWT明显高于C组(均P0.05)。4组大鼠d0时后肢TWL差异无统计学意义(均P0.05);B、C、D组大鼠d7~d20时后肢TWL与A组相比明显升高(均P0.05);D组大鼠d7~d20时后肢TWL与C组相比明显升高(均P0.05);C组大鼠d16、d20时后肢TWL与B组相比明显升高(均P0.05)。透射电镜下,A组大鼠的坐骨神经纤维髓鞘板层结构明显松散,呈网状,严重脱髓鞘;B组、C组、D组大鼠的坐骨神经纤维髓鞘板层结构较松散,明显脱髓鞘,但较A组明显减轻,且B组、D组脱髓鞘程度较C组更轻。与A组比较,B组和C组大鼠坐骨神经中NGF表达减少不明显(均P0.05),D组大鼠坐骨神经中NGF表达明显减少(P0.05)。结论川芎嗪能有效防治紫杉醇所致的大鼠神经病理性疼痛,疗效与普瑞巴林相似并有协同作用,作用机理可能是减低坐骨神经NGF的表达,减轻神经损伤。     

实验性糖尿病周围神经病大鼠脊髓及背根神经节CGRP、VIP表达变化

目的通过观察糖尿病大鼠周围神经形态学的变化以及脊髓、背根神经节中降钙素基因相关肽(CGRP)、血管活性肠肽(VIP)表达变化,以探讨神经肽在糖尿病性神经病中所起的作用。方法Wistar大鼠模型的建立:采用腹腔一次性注射pH4.4枸橼酸钠缓冲液配制的1.25%链脲佐菌素(Streptozotocin STZ)制成糖尿病周围神经病大鼠。用ABC免疫组化方法观察8周和12周大鼠降钙素基因相关肽(CGRP)、血管活性肠肽(VIP)在脊髓及背根神经节的表达。结果糖尿病大鼠8周和12周时背根神经节、12周时脊髓CGRP、VIP表达下降(P<0.05),糖尿病大鼠脊髓8周时CGRP、VIP表达与正常大鼠比无明显差别。结论CGRP和VIP参与了糖尿病周围神经病的发病,糖尿病对大鼠背根神经节CGRP、VIP的表达影响更早。     

弥可保对糖尿病神经病理性疼痛大鼠背根神经节Nav1.7表达的影响

目的探讨弥可保对链脲佐菌素(STZ)致糖尿病模型大鼠痛阈及背根神经节(DRG)中电压门控性钠离子通道亚型1.7(Nav1.7)表达的影响。方法健康雄性SD大鼠75只,体质量200~250g,随机分为空白对照组(C组)、模型组(DNP组)和弥可保组(DNP+M组),每组25只,其中模型组和弥可保组皮下注射STZ 75mg/kg制作糖尿病大鼠模型,剔除血糖低于16.7mmol/L的大鼠,14d后给予安慰剂和弥可保(600μg/kg)腹腔注射,1次/d,观察STZ注射前1d及注射后3、7、14、21、28d机械缩足反射阈值(mechanical withdrwal threshold,MWT),行为学测试完成后,采集大鼠背根神经节(DRG)标本,用免疫组化和Western blot方法分别检测其钠离子通道Nav1.7蛋白表达水平。结果与对照组比较,模型组大鼠MWT降低,DRG中Nav1.7的表达上调,差异有统计学意义(P0.05);与模型组比较,弥可保组大鼠MWT升高,DRG中Nav1.7的表达下调,差异有统计学意义(P0.05)。结论弥可保通过抑制糖尿病大鼠DRG中Nav1.7表达,从而缓解大鼠神经病理性疼痛。     

MEK阻滞剂U0126对背根神经节压迫神经痛模型大鼠nNOS表达的影响

摘要 背景：胞外信号调节激酶（ERK）信号通路以及NO激活,是伤害性刺激引起中枢敏化和长时程神经元可塑性中的重要因素,但二者在慢性压迫性损伤引起的神经痛的形成和维持中的作用尚未见报道。 目的：研究ERK信号传导通路阻滞剂U0126对背根神经节压迫神经痛大鼠脊髓背角内神经型一氧化氮合酶表达。 设计,时间及地点：随机对照的实验研究,于2008年7月至2009年3月在吉林大学第一医院耳鼻咽喉头颈外科研究所完成。 材料：雄性Wistar大鼠由吉林大学实验动物中心提供;U0216（美国Bio-Mol公司产品） 方法：CCD模型建立后第五天,采用单次鞘内注射方法行U0126注射,同时在对照组给予鞘内注射无菌的5%二甲基亚砜。 主要观察指标：采用von Frey纤维丝和热痛刺激仪观察CCD大鼠鞘内应用U0126后机械性痛敏和热痛敏阈值的变化,同时应用免疫荧光染色和免疫印记方法观察其对大鼠脊髓背角内nNOS活性的影响。 结果：CCD引起大鼠脊髓背角内nNOS活性的增强,鞘内注射U0126抑制nNOS活性的同时能明显减轻由CCD导致的大鼠机械性痛敏和热痛敏。 结论：脊髓背角神经元胞内ERK信号通路活性的变化能够影响脊髓背角内nNOS表达,ERK参与介导了NO在神经病理性疼痛中的作用。。 主题词：细胞外信号调节激酶;一氧化氮合成酶;神经痛;中枢敏化;痛觉过敏     

神经病理性疼痛治疗进展

目前,神经病理性疼痛(NP)的治疗进展主要表现为对传统镇痛药物作用的重新评价及微创介入治疗的广泛应用.近年来,对周围神经损伤所致病理性疼痛的分子和细胞学机制,特别是对初级感觉神经元和脊髓损伤的研究积累了丰富的资料,周围神经损伤、脊髓背根神经节(DRG)胞体损伤及背根神经损伤等动物模型的建立,为认识神经病理性疼痛的机制和筛选治疗药物提供了有力的工具.     

鞘内注射水溶性脂聚体运载NR2B siRNA减轻坐骨神经缩窄性损伤大鼠神经病理性疼痛

脊髓背角N-甲基-D-天冬氨酸受体2B亚基（NR2B）的过度表达在神经病理性疼痛的产生和维持方面起关键作用,利用siRNA抑制NR2B的表达有望成为神经病理性疼痛甚至神经损伤治疗的新途径,然而,目前仍然缺乏NR2B siRNA安全且高效的载体。本实验探讨了低分子量聚乙烯亚胺和胆固醇组成的水溶性脂聚体（WSLP）运载NR2B siRNA治疗大鼠神经病理性疼痛的可行性,以寻找神经病理性疼痛基因治疗的安全且高效的载体。结果发现：WSLP与NR2B siRNA复合物（WSLP/siRNA）鞘内注射后3d,坐骨神经缩窄性损伤导致的神经病理性疼痛大鼠脊髓背角NR2B的基因表达显著下降,转录水平及蛋白水平的表达分别下降59%及54%（P < 0.01）,WSLP/乱序siRNA(scRNA) 及低分子量聚乙烯亚胺/siRNA鞘内注射后NR2B的基因表达无明显变化。WSLP/siRNA鞘内注射后3,7,14及21d神经病理性痛大鼠患足的疼痛程度明显减轻,而注射低分子量聚乙烯亚胺/ siRNA及WSLP/scRNA却无此作用。由此表明,WSLP可有效运载siRNA抑制神经病理痛大鼠NR2B基因的过度表达,从而对神经病理性疼痛大鼠具有治疗作用。     

脊髓磷酸化胞外信号调节蛋白激酶在大鼠切口痛痛觉过敏中的作用

目的 研究切口痛模型大鼠脊髓磷酸化胞外信号调节蛋白激酶(p-ERK)表达的变化及鞘内注射ERK上游激酶MEK的抑制剂U0126对其机械性痛觉阈值的影响.方法 雄性SD大鼠32只按随机数字表法分为假手术组、模型组、DMSO组、U0126组,每组8只,前2组大鼠鞘内注射生理盐水20μL;后2组大鼠分别鞘内注射DMSO、U0126 10μL后用生理盐水10μL冲管.注药10min后除假手术组外,后3组大鼠均制备右后足趾部切口痛模型.分别于制作模型前、模型后2、24、48 h应用YLS-3E电子压痛仪测定各组大鼠右足的机械性痛觉阈值.另取SD大鼠24只.分组方法 和处理同上,每组6只.每组分别在模型后2h、24h选择3只应用免疫组化染色检测大鼠脊髓背角p-ERK的表达.结果模型组、DMSO组大鼠模型后2、24、48 h及U0126组大鼠模型后2、24 h有足机械性痛觉阈值均低于模型前,差异有统计学意义(P<0.05);DMSO组和模型组之间比较大鼠机械性痛觉阈值差异无统计学意义(P>0.05);与同一时间点DMSO组和模型组比较,U0126组大鼠模型后2、24、48 h右足机械性痛觉阈值均增高,差异有统计学意义(P<0.05).免疫组化染色结果发现.与假手术组比较模型组和DMSO组模型后2、24 h患侧脊髓背角P-ERK免疫阳性细胞增多;与模型组和DMSO组同一时间比较,U0126组患侧脊髓背角p-ERK阳性细胞减少,差异均有统计学意义(P相似文献   

NG2细胞的增殖活化对大鼠脊髓损伤后神经病理性疼痛产生和维持的影响

目的探讨NG2细胞在脊髓损伤(SCI)后神经病理性疼痛的产生和维持中的作用。方法将100只健康成年雄性SD大鼠按随机数字表法分为对照组(n=20, 不做任何干预措施)、假手术组(n=40, 暴露T10节段但不实施脊髓撞击)及SCI组(n=40, 暴露T10节段并采用改进型Allen’’s法构建SCI模型)。分别于术前1 d及术后14 d、21 d、28 d时, 应用Von Frey纤维探针检测大鼠后肢的机械缩足反射阈值(MWT), 采用免疫荧光染色检测大鼠脊髓背角NG2阳性细胞数量占细胞总数比例, 应用Western blotting实验检测大鼠脊髓背角硫酸软骨素蛋白多糖(CSPG)的表达。结果术后14 d、21 d、28 d时, SCI组大鼠后肢MWT均明显低于对照组及假手术组, 脊髓背角NG2阳性细胞数量占细胞总数比例均明显高于对照组及假手术组, 脊髓背角CSPG表达均明显高于对照组及假手术组, 差异均有统计学意义(P<0.05)。SCI组大鼠术前1 d及术后14 d、21 d、28 d时的后肢MWT呈现先下降后回升趋势, 脊髓背角NG2阳性细胞数量占细胞总数比例呈现先上升后...     

早期高压氧治疗对慢性压迫性损伤模型大鼠疼痛行为学的影响

目的观察神经病理性疼痛发病早期0.25 MPa高压氧治疗对大鼠疼痛行为学的影响,并探讨早期治疗的作用机制。方法采用左后肢坐骨神经结扎术建立慢性压迫性损伤大鼠模型,术后早期(第1天)即开始进行高压氧(0.25 MPa)治疗(60 min/d),5d后观察大鼠一般情况、自发缩足次数、缩足阈值(PWT)和缩足潜伏期(PWL)等疼痛行为学变化。结果与假手术组相比,模型组大鼠体质量显著下降(t=4.772,P=0.000)、高压氧组大鼠体质量降低幅度小于模型组(t=2.411,P=0.029);模型组大鼠术后即出现缩足潜伏期缩短(t=28.345,P=0.000),第3天开始自发缩足次数增多(t=12.541,P=0.000)、缩足阈值降低(t=4.032,P=0.001)。与模型组相比,高压氧治疗组大鼠术后第3天开始缩足次数减少(t=8.077,P=0.000)、缩足阈值增加(t=2.114,P=0.049)、缩足潜伏期延长(t=7.715,P=0.000)。结论早期施行高压氧(0.25 MPa)治疗可以显著改善神经病理性疼痛大鼠痛敏症状,为临床神经病理性疼痛提供一种新的便捷、经济、有效的治疗方法。     

普瑞巴林对CCI模型大鼠背根神经节p-JNK1表达的影响

目的观察不同剂量普瑞巴林对慢性坐骨神经压迫损伤所致神经病理性疼痛大鼠痛行为及背根神经节p-JNK表达的影响。方法雌性SD大鼠60只,随机分为5组,每组12只：假手术组（S组）、CCI组（C组）和不同剂量普瑞巴林P1组、P2组、P3组。S组仅分离坐骨神经不结扎,C组和P1、P2、P3组建立CCI模型,P1、P2、P3组于术后第1天开始至取材时点分别胃内灌注普瑞巴林7mg/kg、15mg/kg、30mg/kg,S组和C组灌相同体积生理盐水。各组大鼠分别于术前1d,术后1、3、7、15天测定热痛阈PWL值,且在术后第3、7、15天测定热痛阈后每组随机取4只大鼠术侧背根神经节,免疫组化法测定背根神经节p-JNK的表达。结果与术前1d比较,C组、P1组术后1、3、7、15dPWL值和p-JNK的表达有显著统计学差异（P〈0.05）。与C组比较,P1、P2、P3组PWL值和p-JNK在术后3、7、15d的表达有显著性差异（P〈0.05）。与P1组比较,P2、P3组术后1、3、7、15dPWL值和p-JNK的表达差异有统计学意义（P〈0.05）。结论不同剂量普瑞巴林对CCI模型大鼠致神经病理性疼痛有镇痛作用且呈剂量依赖性,其机制可能与抑制p-JNK的活化有关。     

Activation of extracellular signal-regulated protein kinases 5 in the spinal cord contributes to the neuropathic pain behaviors induced by CCI in rats

Abstract

Objective: To investigate whether activation and translocation of extracellular signal-regulated kinase 5 (ERK5) is involved in the induction and maintenance of neuropathic pain and observe the effects of activation and translocation of ERK5 on the expression of phosphorylated cAMP response element binding (pCREB) 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 ～ 1.0 mm intervals with 4-0 silk sutures. The phosphorothioate-modified antisense oligonucleotides (AS-ODNs) were intrathecally administered every 12 hours, 1 day pre-chronic constriction injury (CCI) and 3 day post-CCI. Thermal and mechanical nociceptive thresholds were assessed with the paw withdrawal latency to a radiant heat and von Frey filaments. Expressions of phosphorylated ERK5 (pERK5), pCREB, were assessed by both Western blotting and immunohistochemical analysis.

Results: Intrathecal injection of ERK5 AS-ODN significantly attenuated CCI-induced mechanical allodynia and thermal hyperalgesia. CCI significantly increased the expression of pERK5 neurons in the ipsilateral spinal dorsal horn to injury, not in the contralateral spinal dorsal horn. The time courses of pERK5 expression showed that the levels of both cytosol and nuclear pERK5 were increased at all points after CCI and reached a peak level on post-operative day 5. CCI significantly increased the expression of pERK5 neurons in the laminae I and II of ipsilateral spinal dorsal horn to injury, not in the contralateral spinal dorsal horn. Phospho-CREB-positive neurons were distributed in all laminae of the bilateral spinal cord. Intrathecal injection AS-ODN markedly suppressed the increase of CCI-induced pERK5, pCREB expression in the spinal cord.

Conclusion: The activation of ERK5 pathways contributes to neuropathic pain in CCI rats, and the function of pERK5 may partly be accomplished via the CREB protein-dependent gene expression.     

Electroacupuncture and A‐317491 depress the transmission of pain on primary afferent mediated by the P2X3 receptor in rats with chronic neuropathic pain states

P2X is a family of ligand‐gated ion channels that act through adenosine ATP. The P2X₃ receptor plays a key role in the transmission of neuropathic pain at peripheral and spinal sites. Electroacupuncture (EA) has been used to treat neuropathic pain effectively. To determine the role of EA in neuropathic pain mediated through the P2X₃ receptor in dorsal root ganglion neurons and the spinal cord, a chronic constriction injury (CCI) model was used. Sprague‐Dawley rats were divided into four groups: sham CCI, CCI, CCI plus contralateral EA, and CCI plus ipsilateral EA. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were recorded. Furthermore, the expression of the P2X₃ receptor was evaluated through Western blotting and immunofluorescence. The effects of EA and A‐317491 were investigated through the whole‐cell patch‐clamp method and intrathecal administration. Our results show that the MWT and TWL of EA groups were higher than those in the CCI group, whereas the expression of the P2X₃ receptor was lower than that in the CCI group. However, no significant difference was detected between the two EA groups. EA depressed the currents created by ATP and the upregulation of the P2X₃ receptor in CCI rats. Additionally, EA was more potent in reducing mechanical allodynia and thermal hyperalgesia when combined with A‐317491 through intrathecal administration. These results show that both contralateral and ipsilateral EA might inhibit the primary afferent transmission of neuropathic pain induced through the P2X₃ receptor. In addition, EA and A‐317491 might have an additive effect in inhibiting the transmission of pain mediated by the P2X₃ receptor. © 2014 Wiley Periodicals, Inc.     

Role of puerarin in the signalling of neuropathic pain mediated by P2X3 receptor of dorsal root ganglion neurons

Tissue injury or inflammation of the nervous system may result in chronic neuropathic pain characterized by sensitivity to painful stimuli. P2X₃ receptors play a crucial role in facilitating pain transmission. Puerarin is an active compound of a traditional Chinese medicine Ge-gen, and Ge-gen soup has anti-inflammatory effects. The present research investigated the role of puerarin in the signalling of chronic neuropathic pain mediated by P2X₃ receptors of rat dorsal root ganglion neurons. Chronic constriction injury (CCI) rat model was adopted. Sprague-Dawley rats were randomly divided into blank control group (Ctrl), sham group (Sham), puerarin-treated control group (Ctrl + PUE), chronic constriction injury (CCI) group and puerarin-treated CCI group (CCI + PUE). Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured by the von-Frey test and the Hargreaves’ test respectively. The stain values of P2X₃ protein and mRNA in L4/L5 dorsal root ganglion (DRG) were detected by immunohistochemistry, western blot and in situ hybridization. At day 4-7 after the operation of CCI rats, MWT and TWL in group CCI and CCI + PUE were lower than those in group Ctrl, Sham and Ctrl + PUE, while there was no difference among group Ctrl, Sham and Ctrl + PUE. At day 7-10 after operation, MWT and TWL in group CCI + PUE was higher than those in group CCI, but there was no significant difference between group CCI + PUE and group Ctrl (p > 0.05). At day 14 after operation, the stain values of P2X₃ proteins and mRNAs in L4/L5 DRG of group CCI were higher than those in group Ctrl, Sham, Ctrl + PUE and CCI + PUE, while the stain values of P2X₃ proteins and mRNAs in group CCI + PUE were significantly decreased compared with those in group CCI. Therefore, puerarin may alleviate neuropathic pain mediated by P2X₃ receptors in dorsal root ganglion neurons.     

Role of phosphorylation of ERK in induction and maintenance of LTP of the C-fiber evoked field potentials in spinal dorsal horn

Previous works have shown that activation of extracellular signal-regulated kinase (ERK)/cAMP response element binding protein (CREB) pathway is essential for long-term potentiation (LTP) in hippocampus. In the present study, the role of the ERK/CREB pathway in LTP of C-fiber evoked field potentials in spinal dorsal horn, which is relevant to pathologic pain, was investigated in adult rats. Western blotting analysis showed that the protein level of phosphorylated ERK (p-ERK) in ipsilateral spinal dorsal horn was transiently increased after LTP induction, starting at 15 min and returning to control at 60 min after tetanic stimulation and that the protein level of p-CREB increased at 30 min, persisting for at least 3 hr after LTP induction. Double immunofluorescence staining showed that p-ERK and p-CREB were only located in neurons but not in glial cells in the spinal dorsal horn after LTP induction. More importantly, we found that spinal application of PD 98059 (100 microM), a selective MEK inhibitor, at 30 min before tetanic stimulation blocked LTP induction and prevented the increase in p-ERK and p-CREB in spinal dorsal horn. When applied 15 min after LTP induction, PD98059 reversed established LTP. The drug, however, did not affect the spinal LTP, when applied at 30 min after LTP. Our results suggested that activation of ERK/CREB pathway in spinal dorsal neurons is necessary for induction and maintenance of long-term potentiation of the C-fiber evoked field potentials.     

Effect of tetramethylpyrazine on primary afferent transmission mediated by P2X3 receptor in neuropathic pain states

Neuropathic pain is the most difficult type of pain to treat. The P2X₃ receptors play a crucial role in facilitating pain transmission at peripheral and spinal sites. The present research investigated the effects of tetramethylpyrazine (TMP) on the primary afferent transmission induced by P2X₃ receptor in neuropathic pain states. Chronic constriction injury (CCI) model was adopted. Sprague–Dawley male rats (n = 30) had been randomly divided into normal saline (sham + NS) group (I), TMP group (II), sham group (III), CCI + TMP group (IV), and CCI group (V). Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured and P2X₃ immunoreactivity in L4/L5 dorsal root ganglion (DRG) and spinal cord was detected by immunohistochemistry. The mechanical withdrawal threshold and thermal withdrawal latency in group V were lower than those in groups I–III or IV (p < 0.05), while P2X₃ receptor expression of L4/L5 DRG and spinal cord in group V was higher than those in groups I–III (p < 0.01) or group IV (p < 0.05). The mechanical withdrawal threshold, thermal withdrawal latency and P2X₃ immunoreactivity of L4/L5 DRG and spinal cord in group IV showed no significant difference compared with those in groups I, II or III (p > 0.05). The amplitudes of the currents in group V (CCI) were much larger than those obtained in other groups after application of same concentration adenosine 5′-triphosphate disodium (ATP) (p < 0.01). α,β-Methylene-ATP (α,β-meATP)-activated currents in DRG neurons of CCI rats were more obvious than those obtained in other group rats (p < 0.01). The results showed that TMP may inhibit the primary afferent transmission of neuropathic pain induced by P2X₃ receptor.     

Translocation Associated Membrane Protein 1 Contributes to Chronic Constriction Injury-Induced Neuropathic Pain in the Dorsal Root Ganglion and Spinal Cord in Rats

Neuropathic pain is a severe debilitating state caused by injury or dysfunction of somatosensory nervous system, and the clinical treatment is still challenging. Translocation associated membrane protein 1 (TRAM1), an adapter protein, participates in a variety of transduction pathways and mediates the biological functions such as cell proliferation, activation, and differentiation. However, whether TRAM1 is involved in the pathogenesis of neuropathic pain is still unclear. In our study, we reported the role of TRAM1 in the maintenance of neuropathic pain induced by chronic constriction injury (CCI) on rats. By western blot and staining, we found that TRAM1 increased in the dorsal root ganglion (DRG) neurons and spinal cord (SC) neurons after CCI. Being similar to IB4-, CGRP-positive expressed area, TRAM1 also expressed in the superficial laminae of the spinal cord dorsal horn (SCDH), suggesting it was related to the innervations of the primary afferents. Moreover, intrathecal injection of TRAM1 siRNA or Toll-like receptor 4 (TLR4) inhibitor induced low expression of TRAM1 in SC, which alleviated the pain response induced by CCI. The upregulation of p-NF-κB expression was reversed by TRAM1 siRNA in SC and DRG, and intrathecal injection of p-NF-κB inhibitor relieved neuropathic pain. All the data indicated that TRAM1 could take part in CCI-induced pain and might be a potential treatment for chronic neuropathic pain.     

RSEP1 is a novel gene with functional involvement in neuropathic pain behaviour

Neuropathic pain from nerve injury by trauma, disease or surgery often causes prolonged suffering. To explore the molecular mechanisms that underlie neuropathic pain, we used mRNA from the L4--5 segments of the lumbar spinal cord of rats with chronic constriction injury (CCI)-induced neuropathic pain, and differentially screened a cDNA library from the rat brain. A novel gene, termed RSEP1 (Rat Spinal cord Expression Protein 1), was identified. Northern blots revealed that RSEP1 was expressed mainly in the central nervous system including the cerebral cortex, hippocampus, brainstem and spinal cord, as well as in the kidney and ovary. In situ hybridization showed a high level of RSEP1 expression in the CA1, CA3 and dentate gyrus regions of the hippocampus and the small sensory neurons in the dorsal horn, as well as the large neurons in the ventral horn of the spinal cord. Intrathecal injection of RSEP1 antisense oligonucleotide into the spinal cord lumbar enlargement attenuated neuropathic pain behaviours in CCI rats, suggesting a functional involvement of RSEP1 in neuropathic pain.     

Fractalkine (CX3CL1) and fractalkine receptor (CX3CR1) distribution in spinal cord and dorsal root ganglia under basal and neuropathic pain conditions

Fractalkine is a unique chemokine reported to be constitutively expressed by neurons. Its only receptor, CX3CR1, is expressed by microglia. Little is known about the expression of fractalkine and CX3CR1 in spinal cord. Given that peripheral nerve inflammation and/or injury gives rise to neuropathic pain, and neuropathic pain may be partially mediated by spinal cord glial activation and consequent glial proinflammatory cytokine release, there must be a signal released by affected neurons that triggers the activation of glia. We sought to determine whether there is anatomical evidence implicating spinal fractalkine as such a neuron-to-glia signal. We mapped the regional and cellular localization of fractalkine and CX3CR1 in the rat spinal cord and dorsal root ganglion, under basal conditions and following induction of neuropathic pain, employing both an inflammatory (sciatic inflammatory neuropathy; SIN) as well as a traumatic (chronic constriction injury; CCI) model. Fractalkine immunoreactivity and mRNA were observed in neurons, but not glia, in the rat spinal cord and dorsal root ganglia, and levels did not change following either CCI or SIN. By contrast, CX3CR1 was expressed by microglia in the basal state, and the microglial cellular concentration was up-regulated in a regionally specific manner in response to neuropathy. CX3CR1-expressing cells were identified as microglia by their cellular morphology and positive OX-42 and CD4 immunostaining. The cellular distribution of fractalkine and CX3CR1 in the spinal circuit associated with nociceptive transmission supports a potential role in the mechanisms that contribute to the exaggerated pain state in these models of neuropathy.     

CX3CL1/CX3CR1 regulates nerve injury‐induced pain hypersensitivity through the ERK5 signaling pathway

Peripheral nerve injury induces the cleavage of CX3CL1 from the membrane of neurons, where the soluble CX3CL1 subsequently plays an important role in the transmission of nociceptive signals between neurons and microglia. Here we investigated whether CX3CL1 regulates microglia activation through the phosphorylation of extracellular signal‐regulated protein kinase 5 (ERK5) in the spinal cord of rats with spinal nerve ligation (SNL). ERK5 and microglia were activated in the spinal cord after SNL. The knockdown of ERK5 by intrathecal injection of antisense oligonucleotides suppressed the hyperalgesia and nuclear impact of nuclear factor‐κB induced by SNL. The blockage of CX3CR1, the receptor of CX3CL1, significantly reduced the level of ERK5 activation following SNL. In addition, the antisense knockdown of ERK5 reversed the CX3CL1‐induced hyperalgesia and spinal microglia activation. Our study suggests that CX3CL1/CX3CR1 regulates nerve injury‐induced pain hypersensitivity through the ERK5 signaling pathway. © 2013 Wiley Periodicals, Inc.