电针镇痛与神经病理性疼痛大鼠脊髓大麻素2受体表达

目的:观察电针对慢性坐骨神经缩窄性损伤(CCI)模型大鼠的镇痛效果及脊髓背角、背根神经节大麻素2受体(CB2)表达,探讨电针镇痛可能的机制.方法:健康SD雄性大鼠共40只,随机分为CCI假手术组(n=10);CCI对照组(n=10);CCI假电针组(n=10);CCI电针组(n=10).所有大鼠均在术前、术后第9、11、13、15、16d进行机械性痛阈测定;各组大鼠于术后第16d,采用Western blot法测定脊髓背角、背根神经节CB2受体蛋白表达.结果:CCI对照组、CCI假电针组和CCI电针组大鼠在治疗前机械性痛阈较术前明显下降,与同一时间段CCI假手术组大鼠比较差异有统计学意义(P＜0.05).治疗后6d,CCI电针组机械性痛阈较治疗前有一定改善(P＜0.05);CCI电针组与CCI假电针组和CCI对照组比较脊髓背角、背根神经节CB2的表达有下降的趋势,但差异无统计学意义(P＞0.05).结论:本研究观察到电针治疗能够在一定程度上改善CCI模型大鼠的机械性痛阈,起到一定的镇痛效果,但是本研究结果未能提示其镇痛机制有脊髓背角、背根神经节CB2的参与.     

脉冲射频大鼠CCI模型DRG对脊髓小胶质细胞IRF8表达的影响

目的:研究脉冲射频(pulsed radiofrequency,PRF)大鼠慢性坐骨神经缩窄损伤(chronic constriction injury of sciatic nerve,CCI)模型背根神经节(dorsal root ganglion,DRG)能否抑制脊髓小胶质细胞中干扰素调节因子8(interferon regulatory factor 8,IRF8)表达而减轻疼痛。方法:雄性SD大鼠120只随机均分为4组:假手术组(Sham)、CCI组、CCI+PRF组、CCI+NPRF组,每组30只。采用结扎一侧坐骨神经主干制作大鼠CCI模型。CCI+PRF组于制模后第7 d,对术侧L4-5背根神经节进行脉宽20 ms、脉冲频率2 Hz,42℃,持续6 min的PRF治疗。CCI+NPRF组仅在相同位置放置射频电极,无脉冲治疗,持续6 min。制模前测量各组大鼠基础阈值,制模后1、3、5、7 d,PRF后1、3、5、7、14 d四组大鼠均接受行为学、痛阈测定。制模后7 d,PRF后7、14 d western blot检测IRF8蛋白表达。制模后7 d,PRF后14 d免疫荧光法检测Iba1表达。结果:与假手术组比,CCI组、CCI+PRF组、CCI+NPRF组大鼠于神经损伤后痛阈均显著降低(P<0.05),脊髓IRF8、Iba1表达上调(P<0.05)。脉冲射频后CCI+PRF组与治疗前比较痛阈升高(P<0.05),并显著高于CCI组和CCI+NPRF组(P<0.05),脊髓IRF8、Iba1表达则相应减少。结论:脉冲射频可缓解大鼠CCI模型神经病理性疼痛,其机制可能与抑制大鼠脊髓IRF8表达、小胶质细胞活化有关。     

神经病理性疼痛大鼠脊髓IL-33蛋白表达的变化

目的:观察外周神经慢性压榨性损伤(chronic constrictive injury,CCI)大鼠脊髓白介素-33(interleukin-33,IL-33)表达的变化规律。方法:雄性Wistar大鼠60只,分为手术组和假手术组,每组30只,于CCI前1天、CCI后第1、4、7、14、21天各时间点测定机械痛阈及热痛阈后立即处死大鼠,每个时间点5只,取L4~6脊髓,采用Western blot方法测定IL-33的蛋白表达变化。结果:手术组大鼠术侧机械痛阈及热痛阈明显降低,脊髓IL-33水平表达增加,明显高于对侧和假手术组术侧;IL-33蛋白水平于CCI后第1天开始增加,第7天达到高峰(P<0.01),于CCI后第21天仍维持于较高水平(P<0.05)。结论:CCI致大鼠脊髓IL-33活化,参与神经病理性疼痛的调控过程。     

NMDA受体NR2B特异性拮抗剂Ifenprodil对CCI大鼠神经病理性疼痛的预防作用

目的:观察预先给予ifenprodil是否可以预防坐骨神经慢性压榨性损伤(CCI)大鼠的神经病理性疼痛。方法:体重在180～200g的雄性SD大鼠随机分为4组:假手术 生理盐水组、假手术 ifenprodil组、CCI 生理盐水组及CCI ifenprodil组。建立外周神经慢性压榨性损伤(CCI)动物模型,假手术组大鼠同样分离坐骨神经,但不结扎神经。假手术 ifenprodil组及CCI ifenprodil组大鼠在术前30min及术后第1、2d连续三天腹腔内注射ifenprodil(10mg/kg);假手术 生理盐水组及CCI 生理盐水组大鼠则以同体积生理盐水代替ifenprodil进行腹腔内注射。使用vonFrey纤维测量大鼠手术侧机械痛阈。比较各组大鼠手术前后的机械痛阈。结果:CCI 生理盐水组大鼠的机械痛阈在术后第7d及14d均明显低于术前(P<0.05);其余各组大鼠的机械痛阈在术后较术前无显著性差异(P>0.05);CCI ifenprodil组大鼠术后7d及14d的机械痛阈显著高于CCI 生理盐水组(P<0.05)。结论:预先给予选择性作用于NR2B亚基的NMDA受体拮抗剂(ifen-prodil)可有效预防外周神经损伤所导致的神经病理性疼痛。因此NR2B的活化在神经病理性疼痛的形成过程中起重要作用。     

鞘内注射维生素B_6对大鼠慢性神经痛的镇痛作用及对DRG神经元p-ERK表达的影响

目的:观察维生素B_6(VitB_6)对神经病理性疼痛大鼠机械痛敏、热痛敏及L4～L5背根神经节(DRG)磷酸化细胞外信号调节激酶(P-ERK)表达的影响.方法:选择6只正常SD大鼠作为对照组(control),另选择鞘内置管3天后无神经损伤症状的SD雄性大鼠54只,随机分为3组(n=18):假手术组(sham):只分离坐骨神经;CCI组:结扎坐骨神经;CCI+Vit B6组:坐骨神经结扎后鞘内注射VitB_610mg/kg/d,连续两周.各组术前2天和术后1、3、5、7、10、14天测定各组大鼠热缩足反射潜伏期(TWL)、机械缩足反射阈值(MWT).除control组外其余各组分别在术后3d、7d和14d处死大鼠,采用免疫组织化学法观察L4～5 DRG和p-ERK的表达.结果:与sham组比较,CCI组术后各天TWL、MWT明显降低(P＜0.01);与CCI组比较,CCI+VitB_6组术后3、5、7、10、14天TWL明显增高(3天P＜0.05,5、7、10、14天P＜0.01),而术后各天MWT无明显差别.术后3、7、14天,CCI组结扎侧L4,5背根节p-ERK阳性细胞率明显高于sham组(P＜0.01),CCI+Vit B_6组结扎侧L4,5背根节p-ERK阳性细胞率明显低于CCI组(P＜0.01).结论:背根神经节ERK活化参与神经病理性疼痛信号传递,鞘内注射Vit B_6抑制CCI大鼠热痛敏,其机制可能包括通过上游机制抑制ERK激活.     

电针对大鼠神经病理性疼痛及背根神经节中p38 MAPK蛋白表达的影响

目的:观察电针刺激“足三里”穴位对大鼠神经病理性疼痛的影响,及电针治疗对大鼠背根神经节中p38丝裂原活化蛋白激酶(p38 mitogen-activated protein kinase,p38 MAPK)信号转导途径的影响.方法:40只雄性Wistar大鼠随机均分为4组(n=10):空白对照组(Con组);坐骨神经结扎组(CCI组);假电针治疗组(CCI+A组);电针治疗组(CCI+EA组).分别于实验前及坐骨神经结扎后第7、14、21 d,观察并记录大鼠的热缩足反射潜伏期(paw withdrawal latency,PWL)和机械缩足反应阈值(paw withdrawal threshold,PWT)变化和大鼠受累后肢的运动功能评分.在实验结束(即第21 d)时,处死大鼠,取出右侧L4～6节段的背根神经节,之后采用免疫组化的方法检测大鼠背根神经节中p38MAPK蛋白的表达.结果:PWT和PWL在Con组中没有变化,而在CCI组和CCI+A组中显著降低,并持续至实验结束.CCI+EA组在电针治疗后PWT和PWL与CCI组和CCI+A组相比显著升高(P＜0.05).电针治疗后,CCI+EA组大鼠受累后肢的运动评分显著低于CCI+A组和CCI组(P＜0.05).免疫组化结果显示:CCI+EA组大鼠背根神经节中的磷酸化p38MAPK (phosphor-p38 MAPK,p-p38 MAPK)阳性细胞表达均显著低于CCI组和CCI+A组(P＜0.05).结论:电针刺激“足三里”穴位能够减轻神经病理性疼痛大鼠的热痛和机械痛,改善大鼠受累后肢的运动功能评分;电针抑制CCI大鼠背根神经节中p38MAPK的表达.     

大鼠背根神经节持续受压后脊髓背角TRPV4蛋白表达及分布的变化

目的:探讨大鼠背根神经节持续受压(chronic compression of the dorsal root ganglion,CCD)后瞬时感受器电位离子通道香草素亚族受体4(transient receptor potential vanilloid 4,TRPV4)在脊髓背角中的蛋白表达及分布规律。方法:选取清洁级雄性Wistar大鼠30只,按随机数字表法分组:空白对照组5只,手术组25只(术后4天、7天、14天、28天各5只;免疫荧光组5只)。制备大鼠背根神经节持续受压模型,于术后4天,7天,14天及28天,测量机械刺激缩爪反应痛阈,观察机械痛阈的变化;利用western blot技术检测空白对照组及术后4天,7天,14天及28天,手术侧及对侧脊髓背角TRPV4蛋白表达的变化;利用免疫荧光技术检测术后4天,手术侧与对侧脊髓背角TRPV4阳性细胞分布。结果:大鼠背根神经节持续受压后4—14天,机械痛阈值明显下降(P0.001);术后4—7天,手术侧脊髓背角TRPV4表达升高(P0.01),对侧无明显变化;手术侧脊髓背角内TRPV4阳性细胞数目高于对侧(P=0.0008)。结论:大鼠背根神经节持续受压后,机械痛阈下降的同时,手术侧脊髓背角内TRPV4蛋白表达上调及阳性数目增多,TRPV4可能参与CCD后病理性神经痛的中枢敏化机制。     

延胡索乙素分别与URB597和URB602联合应用对CCI大鼠镇痛作用的研究

目的:观察延胡索乙素(levo-tetrahydropalmatine,L-THP)分别与脂肪酸酰胺水解酶(fattyacid amide hydrolase,FAAH)、单酰甘油脂肪酶(monoacylglycerol lipase,MAGL)特异性抑制剂URB597、URB602分别联合应用对坐骨神经慢性压迫损伤(chronic constriction injury,CCI)所致大鼠神经病理性疼痛的影响。方法:成年健康雄性Wistar大鼠30只,体重180~220 g,随机分为5组(n=6):假手术组、CCI组、延胡索乙素CCI组、延胡索乙素URB597 CCI组、延胡索乙素URB602 CCI组。假手术组仅暴露坐骨神经但不结扎,其余组均暴露并结扎坐骨神经。术毕即刻,延胡索乙素CCI组、延胡索乙素URB597 CCI组和延胡索乙素URB602 CCI组腹腔注射延胡索乙素40 mg/(kg.d),连续14 d;假手术组和CCI组给予等量生理盐水。术后11 d开始,延胡索乙素URB597 CCI组、延胡索乙素URB602 CCI组手术切口局部分别注射URB597、URB602 0.3 mg/(kg.d),连续4 d,假手术组、CCI组、延胡索乙素CCI组注射等量生理盐水。于术前1 d、术后3 d、7d、11 d、12 d、13 d、14 d测试各组大鼠机械痛阈(mechanical withdrawal threshold,MWT)和热痛阈(thermal withdrawal latency,TWL)。结果:与术前和假手术组比较,CCI组、延胡索乙素CCI组、延胡索乙素URB597 CCI组和延胡索乙素URB602 CCI组大鼠,术后3 d开始各时间点机械痛阈和热痛阈显著降低(p<0.05);与CCI组比较,延胡索乙素CCI组、延胡索乙素URB597 CCI组和延胡索乙素URB602 CCI组大鼠术后3 d、7 d、11 d、12 d、13 d、14 d机械痛阈和热痛阈显著提高(p<0.05);与延胡索乙素CCI组比较,延胡索乙素URB597 CCI组、延胡索乙素URB602 CCI组大鼠,术后11 d、12 d、13 d、14 d机械痛阈和热痛阈明显提高(p<0.05);与延胡索乙素URB597 CCI组比较,延胡索乙素URB602 CCI组大鼠各时间点机械痛阈和热痛阈无显著性差异(p>0.05)。结论:在CCI大鼠模型中,延胡索乙素可以产生良好的镇痛作用,当分别与URB597、URB602合用时可以增强其镇痛作用。     

坐骨神经损伤大鼠模型鞘内移植神经干细胞后脊髓背角和背根神经节脑源性神经营养因子的表达

背景：坐骨神经损伤模型可测试伤害性的热刺激和机械刺激所引发的痛觉过敏及冷、触觉异常。目的：观察坐骨神经损伤模型大鼠鞘内移植神经干细胞后脊髓背角和背根神经节脑源性神经营养因子的表达。方法：72只SD大鼠随机均分为假手术组、对照组和实验组。对照组和实验组制作坐骨神经损伤模型,假手术组仅暴露坐骨神经,不结扎。分别于造模后第3,10天进行鞘内移植,实验组注入30μL的神经干细胞悬液,空白组和对照组注入30μL的细胞培养液。结果与结论：与假手术组相比,对照组和实验组移植后3d机械痛阈和热痛阈逐渐降低,至移植后7d降低至最低点（P〈0.01）,于移植后21d恢复至移植前水平;实验组移植后7,14d机械痛阈和热痛阈较对照组明显上升（P〈0.01）。与对照组相比,假手术组移植后7,14,21d各组大鼠脑源性神经营养因子的表达呈低水平（P〈0.05）;移植后14,21d,实验组脑源性神经营养因子的表达量高于对照组（P〈0.05）。提示鞘内移植神经干细胞可提高脊髓背角和背根神经节中脑源性神经营养因子的表达。从而抑制了周围神经损伤产生的神经病理性疼痛。     

鞘内注射地塞米松对神经病理性疼痛的影响

目的:通过大鼠鞘内注射免疫抑制剂地塞米松,探讨其对神经病理性疼痛的影响及机制,为疼痛的治疗提供新的途径。方法:将36只SD大鼠随机分成假手术 盐水治疗组、坐骨神经慢性压迫损伤(CCI) 盐水治疗组、CCI 地塞米松治疗组,每组12只。采用改良CCI法制作神经病理性疼痛模型,假手术 盐水治疗组只暴露坐骨神经而不予结扎,CCI 地塞米松治疗组大鼠于术后即刻、2、4、6、8、10、12天通过鞘内放置的PE-10导管予地塞米松0.5 mg(约0.1 mL),假手术 盐水治疗组和CCI 盐水治疗组大鼠在相同时间点予等容量的0.9%氯化钠。于术后1、3、7、14天测定大鼠的机械痛阈值,并于术后14天将大鼠处死,应用免疫组化技术测定其脊髓星形胶质细胞神经胶质原纤维酸性蛋白(GFAP)及肿瘤坏死因子-α(TNFα-)的表达。结果:坐骨神经结扎后痛阈下降,术后1、3、7、14天,CCI 盐水治疗组和CCI 地塞米松组的痛阈与假手术 盐水治疗组比较差异有统计学意义(P<0.01);CCI 地塞米松组痛阈与CCI 盐水治疗组比较有统计学意义(P<0.05)。免疫组化测定:假手术 盐水治疗组GFAP染色及TNFα-染色以阴性居多,CCI 盐水治疗组和CCI 地塞米松组GFAP染色为强阳性;CCI 盐水治疗组TNFα-染色弱阳性居多,CCI 地塞米松组TNFα-染色以强阳性居多,两者比较差异有统计学意义(P<0.05)。结论:地塞米松对神经病理性疼痛有明显的治疗作用。     

高压氧对神经病理性痛大鼠的疼痛行为学影响

目的:观察高压氧(HBO)对神经病理性痛大鼠的疼痛行为学影响及有效性.方法:40只雄性SD大鼠随机分成5组:即空白对照组(C组)、假手术组(M组)、坐骨神经慢性缩窄手术组(CCI组)、高压氧预处理组(Pre-H组)与高压氧干预组(Post-H组),对其疼痛行为学指标进行比较.结果:Pre-H组和Post-H组的机械性缩足反射阈值(MWT)较CCI组明显升高;热缩足反射潜伏期(TWL)较CCI组明显延长.HBO在热痛模型中显示的作用大子机械痛模型;Pre-H的作用大于Post-H.结论:高压氧对CCI大鼠神经病理性疼痛有一定的抑制作用.     

Tramadol relieves thermal hyperalgesia in rats with chronic constriction injury of the sciatic nerve

The present study was designed to test whether tramadol is effective in the control of neuropathic pain in rats. Chronic constriction injury (CCI) of the sciatic nerve was induced over the left hind limb in male Sprague-Dawley rats. Identical surgery was performed on the opposite side except that the sciatic nerve was not ligated (sham surgery). Paw withdrawal latency (PWL) to heat was tested for each hind paw 1 day before surgery and on the 4th day after surgery to ensure the development of thermal hyperalgesia. In the acute treatment groups, saline or tramadol was administered subcutaneously at doses of 10, 20 or 30 mg/kg, and PWLs were measured 30, 60, 90, 120, 150 and 180 min after treatment. In the semi-chronic treatment groups, continuous systemic administration of tramadol 40 mg/kg/day or saline for 7 days was provided at a uniform rate via osmotic mini pumps. Tramadol reversed PWL in a dose-dependent manner in the acute treatment groups. PWLs were significantly reversed at 2 days after tramadol infusion, and this effect was sustained throughout the remainder of the treatment period in comparison with the saline group. Tramadol also resulted in a decreased sensitivity to thermal stimulus on the sham limb both in acute and semi-chronic administration. We conclude that both acute and semi-chronic tramadol treatment relieves thermal hyperalgesia effectively in rats with CCI of the sciatic nerve. This indicates that tramadol shows promise as a potential treatment for relief of neuropathic pain in humans.     

损伤大鼠L5脊神经及其前后根对痛行为的影响

目的:观察大鼠腰5脊神经和脊神经根不同部位损伤对诱导神经病理性疼痛的不同作用。方法:采用腰5脊神经结扎加切断(lumbar5 spinal nerve ligation,L5 SNL)、腰5前根切除(lumbar5 ventral rhizotomy,L5 VR)和腰5背根切除(lumbar5 dorsal rhizotomy,L5 DR)诱导大鼠痛觉过敏,结合痛行为学测试观察病理性疼痛的发展过程。结果:(1)L5SNL可引起大鼠病理性疼痛。双侧后肢50%撤足阈值(paw withdrawal threshold,PWT)和撤足潜伏期(paw withdrawal latency,PWL)于术后1d明显下降,痛觉过敏的症状,在同侧后肢持续了5周,在对侧后肢也保持3周。(2)L5 VR也可诱导大鼠产生病理性疼痛。双侧后肢50%PWT和PWL于术后1d明显降低,并维持到了术后第5周。(3)L5DR没有引起大鼠产生痛觉过敏症状。与术前基础值和假手术组比较,L5DR后50%PWT和PWL均无明显变化。结论:选择性损伤运动纤维和损伤脊神经均能诱导大鼠产生病理性疼痛,但脊神经背根损伤不引起痛觉过敏。     

Effect of intrathecal octreotide on thermal hyperalgesia and evoked spinal c-Fos expression in rats with sciatic constriction injury

This study was designed to determine whether intrathecal octreotide (sandostatin), a synthetic octapeptide derivative of somatostatin, relieved thermal hyperalgesia and reduced the evoked spinal c-Fos expression in rats with chronic constriction injury (CCI) of the sciatic nerve. Intrathecal catheters were implanted in rats 7 days before CCI of the sciatic nerve over the left hind limb. After confirmation of the development of thermal hyperalgesia by decreased paw withdrawal latencies (PWL) to heat stimulation 7 days after CCI, intrathecal sandostatin at 20, 40, and 80 microg was administered, respectively. Rats in the control group received saline injections intrathecally. PWLs were evaluated at 30, 60, 120, 180, and 240 min after drug administration. Detection of Fos-like immunoreactivity (Fos-LI) neurons in the dorsal horn of the spinal cord following drug administration was performed after mechanical stimulation (stroking of the hind paws) on the 14th day after CCI. The reduction of PWL was attenuated significantly in the groups that received intrathecal sandostatin at 20, 40, and 80 g when compared with the saline group. However, PWL did not return to pre-CCI values in all groups. In the 40 microg group, PWL returned up to 76% of pre-CCI values 120 min after drug administration. Stroking of the hind paw in CCI-treated (ipsilateral) limbs induced a significantly greater expression of spinal Fos-LI neurons than that of non-CCI treated (contralateral) limbs in each group. The number of Fos-LI neurons in animals receiving intrathecal sandostatin was dose-dependently reduced. Expression of Fos-LI neurons in the 80 microg group was nearly completely inhibited. These data suggest that intrathecal sandostatin significantly relieved thermal hyperalgesia behaviorally but with limited effects and dose-dependently reduced spinal Fos-LI neurons expression evoked by stroking stimulation, which may reflect mechanical allodynia in rats with sciatic constriction injury. This implies that intrathecal sandostatin was effective in the treatment of neuropathic pain.     

术前给予巴氯酚延迟坐骨神经松结扎神经病理痛的形成

目的研究术前鞘内注射GABAB受体激动剂巴氯酚(Bac)对慢性神经病理痛大鼠痛阈的影响,探讨脊髓GABA能系统在神经病理痛调节中的作用。方法建立慢性坐骨神经结扎损伤模型(CCI),SD大鼠32只随机分成4组:假手术组,大鼠左侧坐骨神经分离,但不结扎,术前鞘内注射生理盐水10μL;神经结扎组,大鼠左侧坐骨神经松结扎,术前鞘内注射生理盐水10μL;Bac 1组,大鼠左侧坐骨神经松结扎前10 min,鞘内注射Bac 0.03μg;Bac 2组,大鼠左侧坐骨神经松结扎前10min,鞘内注射Bac 0.3μg。术后第1、3、5、7、10、14天测大鼠机械刺激缩足反射阈值(MWT)和热刺激缩足反射潜伏期(TWL)以及运动功能。结果术后第1~14天神经结扎组大鼠MWT和TWL较假手术组大鼠明显降低(P<0.05);术前给Bac 0.3μg的坐骨神经结扎大鼠与术前给生理盐水的坐骨神经结扎大鼠比较,术后第1~5天MWT和TWL明显升高(P<0.05)。结论坐骨神经结扎前鞘内注射Bac 0.3μg可延缓大鼠神经病理性疼痛的形成。     

瑞芬太尼对慢性坐骨神经损伤大鼠T细胞增殖及NK细胞活性的影响

目的:研究瑞芬太尼对慢性坐骨神经持续压迫损伤(chronic constriction injury,CCI)大鼠的T细胞增殖及自然杀伤细胞(NK细胞)活性的影响。方法:40只雄性W istar大鼠分为实验组、盐水对照组和假手术组,用手术方法结扎坐骨神经制作疼痛模型,观察大鼠缩腿反应潜伏期(paw with-drawal latency,PWL)。同时分别应用乳酸脱氢酶释放法和刀豆蛋白A(Con-A)刺激淋巴细胞转化法测定NK细胞活性和T细胞的增殖。结果:实验组大鼠出现PWL增高、T淋巴细胞功能和NK细胞活性抑制,与对照组相比有显著性差异(P<0.05)。结论:瑞芬太尼治疗能够对CCI大鼠痛敏反应产生剂量依赖性抑制作用,但大剂量应用会抑制NK细胞活性和T细胞增殖反应。     

Painful neuropathy decreases membrane calcium current in mammalian primary afferent neurons

Hyperexcitability of the primary afferent neuron leads to neuropathic pain following injury to peripheral axons. Changes in calcium channel function of sensory neurons following injury have not been directly examined at the channel level, even though calcium is a primary second messenger-regulating neuronal function. We compared calcium currents (I(Ca)) in 101 acutely isolated dorsal root ganglion neurons from 31 rats with neuropathic pain following chronic constriction injury (CCI) of the sciatic nerve, to cells from 25 rats with normal sensory function following sham surgery. Cells projecting to the sciatic nerve were identified with a fluorescent label applied at the CCI site. Membrane function was determined using patch-clamp techniques in current clamp mode, and in voltage-clamp mode using solutions and conditions designed to isolate I(Ca). Somata of peripheral sensory neurons from hyperalgesic rats demonstrated decreased I(Ca). Peak calcium channel current density was diminished by injury from 3.06+/-0.30 pS/pF to 2. 22+/-0.26 pS/pF in medium neurons, and from 3.93+/-0.38 pS/pF to 2. 99+/-0.40 pS/pF in large neurons. Under these voltage and pharmacologic conditions, medium-sized neuropathic cells lacked obvious T-type calcium currents which were present in 25% of medium-sized cells from control animals. Altered Ca(2+) signalling in injured sensory neurons may contribute to hyperexcitability leading to neuropathic pain.     

Rapid sprouting of sympathetic axons in dorsal root ganglia of rats with a chronic constriction injury

We compared the time-course of sympathetic nerve sprouting into the L4–6 dorsal root ganglia (DRG) of adult rats following a chronic constriction injury (CCI) made on the sciatic nerve, or following sciatic nerve transection at the same site. We also tested the rats for changes in threshold for withdrawal from mechanical and thermal stimuli delivered to the hindpaws. We found sympathetic sprouting in DRG by 4 days following CCI, paralleling the decreases in mechanosensory threshold and preceding changes in thermal thresholds. However, with sciatic nerve transection, sympathetic sprouting was not detectable until 14 days after nerve injury. Thus, after CCI, sympathetic sprouting occurs with a sufficiently rapid time-course for it to play a role in the genesis of neuropathic pain. We suggest that the more rapid sprouting seen after CCI than after resection is due to the availability of products of Wallerian degeneration, including nerve growth factor, to both spared and regenerating axons following CCI, but not following resection.