Bilateral mechanical and thermal hyperalgesia and tactile allodynia after chronic compression of dorsal root ganglion in mice

Objective Low back pain is one of the most inextricable problems encountered in clinics. Animal models that imitate symptoms in humans are valuable tools for investigating low back pain mechanisms and the possible therapeutic applications. With the development of genetic technology in pain field, the possibility of mutating specific genes in mice has provided a potent tool for investigating the specific mechanisms of pain. The aim of the present study was to develop a mouse model of chronic compression of dorsal root ganglion （CCD）, in which gene mutation can be applied to facilitate the studies of chronic pain. Methods Chronic compression of L4 and L5 dorsal root ganglia was conducted in mice by inserting fine stainless steel rods into the intervertebral foramina, one at L4 and the other at L5. Mechanical allodynia and thermal hyperalgesia were examined with von Frey filaments and radiating heat stimulator, respectively. Results The CCD mice displayed dramatic mechanical and thermal hyperalgesia as well as tactile allodynia in the hindpaw ipsilateral to CCD. In addition, this mechanical and thermal hyperalgesia as well as tactile allodynia was also found to spread to the contralateral hindpaw. Conclusion This model, combined with the possible genetic modification, will strengthen our knowledge of the underlying mechanisms of low back pain. It also favors the development of new treatment strategies for pain and hyperalgesia after spinal injury and other disorders which affect the dorsal root ganglion in humans.

Expression and effect of sodium-potassium-chloride cotransporter on dorsal root ganglion neurons in a rat model of chronic constriction injury

Sodium-potassium-chloride cotransporter 1 (NKCC1) and potassium-chloride cotransporter 2 (KCC2) are associated with the transmission of peripheral pain.We investigated whether the increase of NKCC1 and KCC2 is associated with peripheral pain transmission in dorsal root ganglion neurons.To this aim,rats with persistent hyperalgesia were randomly divided into four groups.Rats in the control group received no treatment,and the rat sciatic nerve was only exposed in the sham group.Rats in the chronic constriction injury group were established into chronic constriction injury models by ligating sciatic nerve and rats were given bumetanide,an inhibitor of NKCC1,based on chronic constriction injury modeling in the chronic constriction injury + bumetanide group.In the experiment measuring thermal withdrawal latency,bumetanide (15 mg/kg) was intravenously administered.In the patch clamp experiment,bumetanide (10 μg/μL) and acutely isolated dorsal root ganglion neurons (on day 14) were incubated for 1 hour,or bumetanide (5 μg/μL) was intrathecally injected.The Hargreaves test was conducted to detect changes in thermal hyperalgesia in rats.We found that the thermal withdrawal latency of rats was significantly decreased on days 7,14,and 21 after model establishment.After intravenous injection of bumetanide,the reduction in thermal retraction latency caused by model establishment was significantly inhibited.Immunohistochemistry and western blot assay results revealed that the immune response and protein expression of NKCC1 in dorsal root ganglion neurons of the chronic constriction injury group increased significantly on days 7,14,and 21 after model establishment.No immune response or protein expression of KCC2 was observed in dorsal root ganglion neurons before and after model establishment.The Cl^– (chloride ion) fluorescent probe technique was used to evaluate the change of Cl^– concentration in dorsal root ganglion neurons of chronic constriction injury model rats.We found that the relative optical density of N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (a Cl^– fluorescent probe whose fluorescence Cenintensity decreases as Cl– concentration increases) in the dorsal root ganglion neurons of the chronic constriction injury group was significantly decreased on days 7 and 14 after model establishment.The whole-cell patch clamp technique revealed that the resting potential and action potential frequency of dorsal root ganglion neurons increased,and the threshold and rheobase of action potentials decreased in the chronic constriction injury group on day 14 after model establishment.After bumetanide administration,the above indicators were significantly suppressed.These results confirm that CCI can induce abnormal overexpression of NKCC1,thereby increasing the Cl^– concentration in dorsal root ganglion neurons;this then enhances the excitability of dorsal root ganglion neurons and ultimately promotes hyperalgesia and allodynia.In addition,bumetanide can achieve analgesic effects.All experiments were approved by the Institutional Ethics Review Board at the First Affiliated Hospital,College of Medicine,Shihezi University,China on February 22,2017 (approval No.A2017-169-01).

Differential Expression of Alpha-Adrenoceptor Subtypes in Rat Dorsal Root Ganglion after Chronic Constriction Injury

Summary： mRNAs of alpha-adrenoceptor （α-AR） subtypes are found in neurons in dorsal root ganglion （DRG） and change after peripheral nerve injury. In this study, the distribution of α-AR subtype proteins was studied in L5 DRG of normal rats and rats with chronic constriction injury of sciatic nerve （CCI）. Using immunofluorescence technique, it was found that α1A-, α1B-, and α2A-AR proteins were expressed in large, medium, and small size neurons in normal DRG, and significantly increased in all size neurons 14 days after CCI. α1D- and α2C-AR was also expressed in all size neurons in normal DRG. However, α1D-AR was significantly increased and α2C-AR was decreased in small size neurons 14 days post CCI. α2B-AR neurons were not detectable in normal and CCI DRG. Co-expression of α1A- and α2A-AR in the same neuron was observed in normal DRG and increased post CCI. Collectively, these results indicated that there is distinct distribution of α-AR subtypes in DRG neurons, and the distribution and levels of expression of α-AR subtypes change differently after CCI. The up-regulation of α-AR subtypes in DRG neurons may play an important role in the process of generating and transmitting neuropathic pain.

Effects of intrathecal injection of glial cell inhibitor on spinal cord astrocytes following chronic compression of dorsal root ganglia in rats

BACKGROUND： Astrocytes are considered to provide nutritional support in the central nervous system. However, recent studies have confirmed that astrocytes also play an important role in chronic pain. OBJECTIVE： To investigate the effects of intrathecal injection of fluorocitrate, minocycline or both on astrocyte activation and proliferation in the spinal dorsal horn of compressed dorsal root ganglion in rats. DESIGN, TIME AND SETTING： The neurology randomized controlled animal study was performed at the Jiangsu Institute of Anesthesia Medicine, from September 2006 to April 2007. MATERIALS： A total of 96 male Sprague Dawley rats, aged 6-8 weeks, were selected for this study. Following intrathecal catheterization, 80 rats underwent steel bar insertion into the L4-5 intervertebral foramina to make a stable compression on the L4-5 posterior root ganglion. Thus rat models of ganglion compression were established. Minocycline and fluorocitrate were purchased from Sigma, USA. METHODS： A total of 96 rats were randomly and equally divided into six groups. Rat L4, L5 transverse process and intervertebral foramina were exposed in the sham operation group, but without steel bar insertion. The model group did not receive any manipulations. Rats in the phosphate buffered saline （PBS） group were intrathecally injected with 0.01 mmol/L PBS （20 μL）. Rats in the fluorocitrate group were subjected to 1 μmol/L fluorocitrate （20 μL）. Rats in the minocycline group were intrathecally injected with 5 g/L minocycline （20 μL）. Rats in the minocycline and fluorocitrate group received a mixture （20 μL） of 5 g/L minocycline and 1 μmol/L fluorocitrate. Following model establishment, drugs were administered once a day. MAIN OUTCOME MEASURES： At 7 and 14 days following model induction, glial fibrillary acidic protein expression in the spinal dorsal horn was measured by immunofluorescence microscopy. Six sections with significant glial fibrillary acidic protein -positive expression were obtained to count astrocytes under an inverted microscope. RESULTS： No significant differences in astrocyte count were detected between the fluorocitrate and model groups. Cell bodies were small with a few processes in the fluorocitrate group, compared with the model group. The astrocyte count decreased significantly in the minocycline group and the minocycline and fluorocitrate group compared with the sham operation, model, PBS and fluorocitrate groups （P 〈 0.01）. The decrease in astrocyte count was mainly found in layers Ⅲ–Ⅳ of the spinal dorsal horn. Cell body volume was smaller and process numbers were fewer in the minocycline group and the minocycline and fluorocitrate group, compared with the model and PBS groups. CONCLUSION： Fluorocitrate can inhibit astrocyte activation, but does not affect astrocyte proliferation. However, minocycline can inhibit the activation and proliferation of astrocytes.

Estrogen affects neuropathic pain through upregulating N-methyl-D-aspartate acid receptor 1 expression in the dorsal root ganglion of rats

Estrogen affects the generation and transmission of neuropathic pain,but the specific regulatory mechanism is still unclear.Activation of the N-methyl-D-aspartate acid receptor 1（NMDAR1） plays an important role in the production and maintenance of hyperalgesia and allodynia.The present study was conducted to determine whether a relationship exists between estrogen and NMDAR1 in peripheral nerve pain.A chronic sciatic nerve constriction injury model of chronic neuropathic pain was established in rats.These rats were then subcutaneously injected with 17β-estradiol,the NMDAR1 antagonist D（-）-2-amino-5-phosphonopentanoic acid（AP-5）,or both once daily for 15 days.Compared with injured drug na？ve rats,rats with chronic sciatic nerve injury that were administered estradiol showed a lower paw withdrawal mechanical threshold and a shorter paw withdrawal thermal latency,indicating increased sensitivity to mechanical and thermal pain.Estrogen administration was also associated with increased expression of NMDAR1 immunoreactivity（as assessed by immunohistochemistry） and protein（as determined by western blot assay） in spinal dorsal root ganglia.This 17β-estradiol-induced increase in NMDAR1 expression was blocked by co-administration with AP-5,whereas AP-5 alone did not affect NMDAR1 expression.These results suggest that 17β-estradiol administration significantly reduced mechanical and thermal pain thresholds in rats with chronic constriction of the sciatic nerve,and that the mechanism for this increased sensitivity may be related to the upregulation of NMDAR1 expression in dorsal root ganglia.

Increased gene and protein expressions of the transient receptor potential vanilloid receptor 4 following sustained pure mechanical pressure on rat dorsal root ganglion neurons

Dorsal root ganglion （DRG） neurons from newborn Wistar rats cultured in vitro were pressurized with 20, 40, 80 or 120 mm Hg compressive Ioadings （1 mm Hg = 0.133 kPa） for 12, 24, 48 or 72 hours, respectively. The 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide test showed that pressures less than 80 mm Hg had no obvious impact on the activity of DRG neurons. The protein expression levels of transient receptor potential vanilloid receptor 4 （TRPV4）, transient receptor potential vanilloid receptor 1, transient receptor potential channel of melastatin type 8, and transient receptor potential subtype ankyrin 1 were assessed by western blot analysis. The mRNA expression of TRPV4 was assessed by real-time PCR. The results showed that sustained mechanical compression up-regulated TRPV4 mRNA and protein expression in the rat DRG neurons, in a time-dependent fashion. Similar changes were not found in the protein expression of transient receptor potential vanilloid receptor 1, transient receptor potential channel of melastatin type 8, and transient receptor potential subtype ankyrin 1. Images of cells using a laser scanning confocal microscope showed that the sustained mechanical pressure increased the number of responsive DRG neurons and was synergistic on the enhanced Ca^2＋ responses to the TRPV4 phorbol ester agonist 4a-phorbo112, 13-didecanoate and hypotonic solutions. These findings demonstrate that sustained mechanical compressive loading in vitro increases the expression of TRPV4 mRNA and protein in DRG neurons and sensitizes TRPV4 Ca^2＋ signals. Mechanical compression does not impact other ion channels in the transient receptor potential family.

Microencapsulated Schwann cell transplantation inhibits P2X3 receptor expression in dorsal root ganglia and neuropathic pain

Schwann cell transplantation is a promising method to promote neural repair, and can be used for peripheral nerve protection and myelination. Microcapsule technology largely mitigates immune rejection of transplanted cells. We previously showed that microencapsulated olfactory ensheathing cells can reduce neuropathic pain and we hypothesized that microencapsulated Schwann cells can also inhibit neuropathic pain. Rat Schwann cells were cultured by subculture and then microencapsulated and were tested using a rat chronic constriction injury（CCI） neuropathic pain model. CCI rats were treated with Schwann cells or microencapsulated Schwann cells and were compared with sham and CCI groups. Mechanical withdrawal threshold and thermal withdrawal latency were assessed preoperatively and at 1, 3, 5, 7, 9, 11 and 14 days postoperatively. The expression of P2X3 receptors in L4-5 dorsal root ganglia of the different groups was detected by double-label immunofluorescence on day 14 after surgery. Compared with the chronic constriction injury group, mechanical withdrawal threshold and thermal withdrawal latency were higher, but the expression of P2X3 receptors was remarkably decreased in rats treated with Schwann cells and microencapsulated Schwann cells, especially in the rats transplanted with microencapsulated Schwann cells. The above data show that microencapsulated Schwann cell transplantation inhibits P2X3 receptor expression in L4-5 dorsal root ganglia and neuropathic pain.

Targeting the nitric oxide/cGMP signaling pathway to treat chronic pain

Nitric oxide(NO)/cyclic guanosine 3′,5′-monophosphate(cGMP) signaling has been shown to act as a mediator involved in pain transmission and processing. In this review, we summarize and discuss the mechanisms of the NO/cGMP signaling pathway involved in chronic pain, including neuropathic pain, bone cancer pain, inflammatory pain, and morphine tolerance. The main process in the NO/cGMP signaling pathway in cells involves NO activating soluble guanylate cyclase, which leads to subsequent production of cGMP. cGMP then activates cGMP-dependent protein kinase(PKG), resulting in the activation of multiple targets such as the opening of ATP-sensitive K+ channels. The activation of NO/cGMP signaling in the spinal cord evidently induces upregulation of downstream molecules, as well as reactive astrogliosis and microglial polarization which participate in the process of chronic pain. In dorsal root ganglion neurons, natriuretic peptide binds to particulate guanylyl cyclase, generating and further activating the cGMP/PKG pathway, and it also contributes to the development of chronic pain. Upregulation of multiple receptors is involved in activation of the NO/cGMP signaling pathway in various pain models. Notably the NO/cGMP signaling pathway induces expression of downstream effectors, exerting both algesic and analgesic effects in neuropathic pain and inflammatory pain. These findings suggest that activation of NO/cGMP signaling plays a constituent role in the development of chronic pain, and this signaling pathway with dual effects is an interesting and promising target for chronic pain therapy.

脊髓背根神经节ZXDC介导CCL2对慢性压迫性 神经损伤小鼠神经性疼痛的作用

目的探讨脊髓背根神经节(dorsal root ganglion,DRG)中转录因子锌指X连锁复制C(zinc finger X-linked duplicated C,ZXDC)介导CCL2/CCR2信号通路对慢性压迫性神经损伤(chronic construction injury model,CCI)诱导神经性疼痛的作用及机制。方法构建小鼠坐骨神经慢性压迫性损伤模型,免疫荧光染色、Western blot法和实时荧光定量PCR(RT-qPCR)检测正常情况和CCI造模后DRG中ZXDC及CCL2表达变化;将实验动物分为假手术(Sham)组、CCI+AAV-NC组和CCI+AAV-ZXDC siRNA组;Western blot法和免疫荧光染色检测各组小鼠CCI造模后各时间点DRG中ZXDC、CCL2和CCR2表达,RT-qPCR检测DRG中促炎性细胞因子TNF-α和IL-1βmRNA表达,机械性缩足反射测试检测神经性疼痛行为改变。结果ZXDC表达定位在DRG大、中、小神经元。CCI损伤后1~3天DRG中ZXDC和CCL2蛋白和mRNA表达显著增高,CCI后7天二者表达显著降低,ZXDC和CCL2mRNA表达量呈正相关(P均<0.05)。CCI后3天,与Sham组比较,CCI+AAV-NC组和CCI+AAV-ZXDC siRNA组ZXDC、CCL2、CCR2蛋白表达、TNF-α和IL-1βmRNA表达显著增高,其中CCI+AAV-ZXDC siRNA组较CCI+AAV-NC组ZXDC、CCL2、CCR2蛋白表达、TNF-α和IL-1βmRNA显著降低(P均<0.05)。与Sham组比较,CCI+AAV-ZXDC siRNA组和CCI+AAV-NC组CCI后各时间点机械缩足阈值均显著降低,其中CCI后7天,CCI+AAV-ZXDC siRNA组机械缩足阈值显著高于CCI+AAV-NC组(P均<0.05)。结论脊髓背根神经节ZXDC基因敲减通过抑制CCL2/CCR2信号通路介导CCI诱导的神经性疼痛。

大黄素抑制背根神经节压迫小鼠模型STAT3、VEGFA、p-ERK蛋白表达及其镇痛作用研究

目的 研究大黄素(Emodin,ED)对背根节压迫小鼠模型的镇痛作用以及对STAT3/VEGFA/p-ERK信号通路的影响。方法 建立背根神经节慢性压迫(chronic compression damage,CCD)小鼠疼痛模型,随机分为空白组、模型组、普瑞巴林组及ED低、中、高剂量组。通过检测动物机械痛敏和热辐射痛敏阈值、醋酸扭体实验评价镇痛效果;ELISA检测小鼠L4-L5节段脊髓组织中白细胞介素-6(interleukin-6,IL-6)、肿瘤坏死因子(tumor necrosis factor-α,TNF-α)和CD18等炎症因子含量;Western blot和免疫荧光检测脊髓组织信号转导子和转录激活子3(signal transducer and activator of transcription 3,STAT3)、血管内皮生长因子(vascular endothelial growth factor,VEGF)和磷酸化细胞外信号调节激酶(phosphorylated extracellular signal-regulated kinases 1/2,p-ERK1/2)蛋白表达。结果 与空白组比较,模型组的机械痛敏、热辐射痛敏阈值显著降低(P<0.05),脊髓背角炎症因子表达显著增高(P<0.05),脊髓中VEGFA、STAT3、p-ERK的表达显著上调(P<0.05)。与模型组比,ED低、中、高剂量组CCD小鼠模型的机械痛敏、热辐射痛敏阈值升高(P<0.05);脊髓背角炎症因子表达降低(P<0.05);脊髓背角小胶质细胞STAT3、VEGFA、p-ERK的表达降低(P<0.05),醋酸诱导的小鼠急性疼痛中扭体次数减少(P<0.05)。结论 ED对背根节压迫小鼠模型有良好的镇痛作用,其机制可能与抑制脊髓背角炎症因子表达和STAT3/VEGFA/p-ERK介导的脊髓小胶质细胞活化有关。

Microencapsulation improves inhibitory effects of transplanted olfactory ensheathing cells on pain after sciatic nerve injury

Olfactory bulb tissue transplantation inhibits P2X2/3 receptor-mediated neuropathic pain. However, the olfactory bulb has a complex cellular composition, and the mechanism underlying the action of purified transplanted olfactory ensheathing cells（OECs） remains unclear. In the present study, we microencapsulated OECs in alginic acid, and transplanted free and microencapsulated OECs into the region surrounding the injured sciatic nerve in rat models of chronic constriction injury. We assessed mechanical nociception in the rat models 7 and 14 days after surgery by measuring paw withdrawal threshold, and examined P2X2/3 receptor expression in L4–5 dorsal root ganglia using immunohistochemistry. Rats that received free and microencapsulated OEC transplants showed greater withdrawal thresholds than untreated model rats, and weaker P2X2/3 receptor immunoreactivity in dorsal root ganglia. At 14 days, paw withdrawal threshold was much higher in the microencapsulated OEC-treated animals. Our results confirm that microencapsulated OEC transplantation suppresses P2X2/3 receptor expression in L4–5 dorsal root ganglia in rat models of neuropathic pain and reduces allodynia, and also suggest that transplantation of microencapsulated OECs is more effective than transplantation of free OECs for the treatment of neuropathic pain.

Electroacupuncture Attenuates Visceral Pain and Reverses Upregulation of TRPV1 Expression in Adult Rats with Neonatal Maternal Deprivation

Irritable bowel syndrome (IBS) is characterized by chronic visceral hypersensitivity that companied by altered bowel movement. However, the treatment options are very limited. The aim of this study was to investigate effects of electroacupuncture (EA) on visceral hypersensitivity in a rat model of IBS and to explore the underlying mechanisms of EA effects. Visceral hypersensitivity was established by neonatal maternal deprivation (NMD) in male rats on postnatal days 2 - 15. Behavioral experiments were conducted at the age of 7 weeks. Treatment with EA at Zusanli (stomach-36, ST-36) significantly reduced abdominal withdrawal reflex (AWR) scores in NMD rats but not in age-matched healthy control rats. In addition, EA treatment hyperpolarized resting membrane potentials, increased the rheobase and reduced the numbers of action potentials evoked by 2 and 3 times rheobase current stimulation of dorsal root ganglion (DRG) neurons innervating the colon. NMD markedly enhanced expression of TRPV1 in colon related DRGs while EA treatment drastically suppressed the expression of TRPV1 in DRGs of NMD rats. These data suggest that EA treatment produced an analgesic effect, which might be mediated at least in a part by suppression of TRPV1 expression and by inhibition of neuronal excitability of primary sensory neurons in rats with chronic visceral pain.

祛风宣肺方通过背根神经反射降低咳嗽敏感性的作用机制研究

目的:探讨祛风宣肺方对咳嗽敏感性增高豚鼠背根神经节中瞬时受体电位香草酸亚型1(TRPV1)、P物质(SP)、降钙素基因相关肽(CGRP)蛋白及基因的作用,进一步研究祛风宣肺方在慢性咳嗽中的作用机制。方法:将48只SPF级雄性健康豚鼠随机分为正常对照组(生理盐水)、模型组(生理盐水)、西药组(Capsazepine)、中药组(祛风宣肺方),采用卵蛋白致敏的方法建立咳嗽敏感性增高豚鼠模型。药物干预1周后辣椒素雾化法测定各组豚鼠的咳嗽次数,实时PCR法测定背根节中TRPV1、SP、CGRP mRNA水平,蛋白印迹法测定背根节中TRPV1、NK1-R、CGRP蛋白表达。结果:与正常对照组比较,模型组咳嗽次数增加,背根节中TRPV1、SP、CGRP mRNA表达增加,TRPV1、NK-1R、CGRP蛋白表达升高(均P<0.01)。与模型组比较,西药组、中药组咳嗽次数降低(P<0.05),背根节中TRPV1、SP、CGRP mRNA表达下降(P<0.01),西药组背根节中TRPV1、NK-1R、CGRP蛋白表达下降(P<0.05),中药组背根节中NK-1R、CGRP蛋白表达下降(P<0.05),TRPV1蛋白表达与模型组比较,差异无统计学意义(P>0.05)。结论:抑制TRPV1通道,抑制背根神经反射进而降低气道神经源性炎症可能是祛风宣肺方的重要疗效机制之一。

TRPV4在介导大鼠背根神经节持续受压后机械和热痛敏中的作用

目的:观察持续机械压迫(CCD)对瞬时感受器电位离子通道4(TRPV4)基因、蛋白表达及功能的影响,明确TRPV4是否参与CCD导致的机械和热痛敏。方法:建立CCD模型后,分别于手术前及手术后第7天、第14天及第28天取材前测量运动功能、机械刺激缩爪反应阈值和热辐射刺激缩爪反应潜伏期。为了测量TRPV4反义核苷酸干扰对机械和热痛阈值的影响,在蛛网膜下腔内注入TRPV4寡脱氧核苷酸(ODN)40μg/d,每天1次,第7天后测量大鼠行为学变化。使用实时定量RT-PCR检测TRPV4基因表达的变化,Western blot检测TRPV4蛋白质表达量的变化,激光共聚焦检测低渗溶液和佛波醇(4α-PDD)刺激背根神经节(DRG)神经元后细胞内钙离子浓度的变化。结果:所有动物在损伤前后步态均正常,持续压迫明显降低大鼠的机械和热痛阈,TRPV4干扰可部分逆转该痛敏。持续机械压迫可以明显增加TRPV4基因和蛋白的表达,手术后第7天,第14天和第28天,TRPV4mRNA的表达分别为假手术组大鼠的4.29倍、2.95倍和2.48倍,蛋白表达量分别为假手术组大鼠的4.34倍,3.88倍和2.47倍。持续机械压迫后,对低渗溶液和4α-PDD产生反应的DRG神经元的比例数增加,细胞内钙的峰值增高。这种反应被TRPV4反义ODN所抑制。结论:CCD可以上调TRPV4的基因、蛋白表达,敏化通道的功能;TRPV4参与介导CCD导致的机械和热痛敏。

延胡索乙素对小鼠坐骨神经CCI模型背根神经节Cav1.2表达的影响

目的探讨延胡索乙素对小鼠坐骨神经慢性压迫性损伤(CCI)所致神经病理性疼痛的镇痛作用以及对背根神经节Cav1.2表达的影响。方法♂C57BL/6小鼠40只,随机分为5组,分别为假手术组(S组)、CCI组(C组)、延胡索乙素组(L组)。建立稳定的小鼠坐骨神经慢性压迫性损伤致神经病理性疼痛模型。按照神经病理性疼痛的诱发和持续时间,又将L组分为诱导期组、诱导维持期组、长程低剂量组。诱导期组于疼痛诱导期(0~5 d)、诱导维持期组于疼痛诱导期及维持期(0~5 d、14~19 d)腹腔给予延胡索乙素45mg·kg^(-1),每日1次;长程低剂量组从术后即刻开始腹腔给予延胡索乙素15 mg·kg^(-1),每日1次,给予19 d。监测小鼠行为学变化,检测小鼠机械痛阈和热痛阈,Western blot及免疫组织化学方法测定背根神经节中Cav1.2表达。结果脊髓背根神经节Cav1.2在C组表达水平最低,S组表达水平最高,在诱导期组、诱导维持期组及长程低剂量组表达明显上调,差异具有统计学意义(P<0.05,P<0.01)。与C组比较,诱导期组、诱导维持期组高剂量以及长程低剂量组长程低剂量给予延胡索乙素可以明显缓解神经病理性疼痛诱导的机械痛敏和热痛敏(P<0.05,P<0.01)。高剂量延胡索乙素可以缓解诱导期、维持期的机械痛敏及维持期的热痛敏(P<0.05),低剂量延胡索乙素对诱导期机械痛敏和热痛敏均无明显作用(P>0.05)。结论小鼠CCI模型疼痛的诱导期、诱导维持期应用高剂量以及长程应用低剂量延胡索乙素可明显缓解坐骨神经慢性压迫性损伤所致神经病理性疼痛,其可能机制之一是延胡索乙素通过上调脊髓背根经节Cav1.2亚基的表达来发挥镇痛作用。

延胡索乙素对大鼠慢性压迫背根节神经元自发放电的影响

目的观察延胡索乙素(l-THP)对大鼠慢性压迫背根节神经元A类纤维自发放电的影响。方法采用单纤维记录大鼠慢性压迫背根节神经元自发放电的方法,观察l-THP对自发放电的影响,以及浓度-效应关系。结果实验中记录到单纤维A类神经元自发放电84根。在A类神经元自发放电中有25根自发放电为周期节律,59根为非周期节律。l-THP(100μmol/L)分别引起16.0%(4/25)的周期节律放电神经元和67.8%(40/59)非周期节律放电神经元放电减少(P<0.01,l-THP干预前后配对t检验)。l-THP对受损背根节(DRG)神经元自发放电的抑制作用具有剂量依赖关系,随着浓度的增大抑制神经元自发放电的时间越快,自发放电恢复所需的时间也越长。其中有57.1%(24/42)的DRG神经元自发放电在洗脱后20 min内可以恢复,42.8%(18/42)的DRG神经元自发放电在洗脱后经过3 h始终没有恢复。结论l-THP对大鼠慢性压迫背根节神经元A类纤维的自发放电有抑制作用。

延胡索乙素对大鼠外周镇痛作用的实验研究

目的观察延胡索乙素(l-THP)对大鼠慢性压迫背根节神经元形成的慢性腰背痛的镇痛作用。方法采用单纤维记录大鼠慢性压迫背根节神经元自发放电。结果本次实验中记录到单纤维A类神经元自发放电59根,其中l-THP对67.80%(40/59)自发放电有抑制作用。l-THP对受损背根节神经元自发放电的抑制作用具有剂量依赖性,随着剂量的增大抑制神经元自发放电的起效时间越快,自发放电恢复所需的时间也越长。结论延胡索乙素对大鼠慢性压迫背根节神经元自发放电有抑制作用。

EPO/NGF对大鼠背根节压迫性损伤的治疗作用

目的:外源EPO/NGF通过其抗痛敏作用,抗凋亡作用及对钠离子通道的影响来探索和研究其在背根神经节(DRG)慢性压迫中的治疗作用。方法:制作多节段DRG慢性压迫大鼠模型,并给予外源EPO或NGF,进行行为学检测,测量大鼠的机械痛阈值和热痛阈值,Tunnel方法原位检测组织中细胞凋亡情况,通过免疫荧光技术,RT-PCR和Western Blot技术检测c-jun,c-fos,NGF,Nav1.8的表达情况。结果:与对照组相比,模型组的大鼠从建模第1 d起痛阈就开始下降,并持续到13 d;与模型组相比,EPO/NGF治疗组的机械痛阈值和热痛阈值得以升高,DRG神经细胞的损伤和凋亡现象减轻或者恢复。NGF的表达由于受到压迫损伤而降低,在给予外源NGF或EPO治疗后表达升高,Nav1.8的表达与NGF相一致。结论:EPO和NGF在神经系统中具有一定的抗凋亡作用,镇痛作用及促进钠离子通道Nav1.8的表达,并且痛阈的降低与Nav1.8表达下降具有一定相关性。

抑制外周神经元PAR2-PKA/PKCε通路对痛转化模型大鼠痛阈的影响

目的探讨外周神经元蛋白酶激活受体2-蛋白激酶A/蛋白激酶Cε(PAR2-PKA/PKCε)通路在痛转化中的作用,寻找同时干预急性痛和慢性痛的可能方案。方法 SD大鼠随机分为空白组、假诱发组、诱发组、抑制剂1组和抑制剂2组。除空白组和假诱发组,所有大鼠均通过先后足部注射角叉菜胶和前列腺素E2(PGE2)建立痛觉敏化诱发模型。PGE2于角叉菜胶注射后7 d进行足部注射。抑制剂1组和抑制剂2组大鼠于PGE2注射前/后,分别给予PAR2抑制剂。观察角叉菜胶/生理盐水,注射前、注射后5 h、3 d、6 d、7 d 0.5 h、7 d 4 h和7 d 24 h大鼠机械痛阈(PWTs)的变化,检测角叉菜胶注射后7 d 24 h造模侧背根神经节(DRG)中PAR2、蛋白激酶A(PKA)和蛋白激酶(PKCε)表达。结果痛觉敏化诱发模型建立成功。角叉菜胶注射后7 d给予PGE2,显著延长了PGE2诱发疼痛的存在时间,角叉菜胶注射后7 d 24 h假诱发组大鼠PWTs与同期空白组相比差异无显著性(P>0.05),而诱发组大鼠PWTs明显低于同期空白组和假诱发组大鼠(P<0.01)。诱发组大鼠造模侧DRG中PAR2和PKCε表达在角叉菜胶注射后7 d 24 h明显提升,高于同期假诱发组和空白组(P<0.05)。给予PAR2抑制,不论时间均能显著翻转角叉菜胶注射后7 d 24 h,诱发组大鼠由PGE2诱发的疼痛(P<0.05),并抑制DRG中PKCε表达。但,给予PAR2抑制剂不能影响PGE2诱发的急性疼痛和调制DRG中PKA含量。结论抑制PAR2表达能阻断急性痛向慢性痛转化,这可能与其抑制DRG中PAR2-PKCε通路激活有关。但抑制PAR2并不能干预急性痛,这可能是因为DRG中PAR2相关通路未参与急性痛的产生。

电针对慢性坐骨神经压迫性损伤大鼠神经病理学及背根神经节P2X_3受体表达的影响

目的:观察EA对CCI大鼠坐骨神经组织病理学及DRG P2X3受体表达的影响,探讨电针对神经组织学的影响及P2X3受体在电针镇痛效应中的作用。方法:将32只成年雄性SD大鼠,分为假模组、模型对照组、健侧EA组、患侧EA组,每组8只,模型对照组及EA组结扎坐骨神经造成CCI疼痛模型。各组于术前(0天)及术后3、57、1、01、2、14天分别测量大鼠患侧足MWT和TWL,EA组于术后第8天电针"足三里"-"阳陵泉"连续7天,每天1次。术后14天对坐骨神经标本行组织学观察,采用Estebe评分方法行组织学评分,免疫荧光组织化学检测患侧L5背根神经节中P2X3受体的表达情况。结果:与术前比较,CCI各组大鼠痛阈明显降低,出现痛觉过敏(P<0.01),而电针干预后EA组较CCI模型组痛阈明显增加(P<0.05)但仍低于假模组。各组大鼠坐骨神经组织学观察无明显差异,各组评分差异无统计学意义(P>0.05)。术后14天EA组较模型对照组患侧DRG L5中P2X3受体表达显著减少(P<0.05),并且患侧EA组较健侧EA组减少明显。结论:电针对坐骨神经压迫性损伤的镇痛效果可能是通过抑制大鼠DRG中P2X3受体的表达产生作用;患侧电针较健侧电针镇痛效果明显;电针后坐骨神经未见明显的病理组织学改变。