Effect of Touch stimulus on the Expression of C-fos and TrkA in Spinal Cord Following Chronic Constriction Injury of the Sciatic Nerve in Rats

Summary: To study the mechanism of the innoxious touch-stimulus on the modulation of hyperalgesia and the expression of the C-fos and the nerve growth factor (NGF) receptor-TrkA in the spinal dorsal horn neurons following the chronic constriction injury (CCI) of the sciatic nerve in rats, 60 female Sprague-Dawley rats were randomly divided into sham-operation group and CCI group, with each group being further divided into 3 subgroups on the 7th,14th and 28th day after operation (n=10). The mechanical and the thermal withdrawal threshold were assessed following the touch stiumulation after the CCI, immunohistochemical methods were employed to observe the expression of the C-fos and TrkA in spinal dorsal horn. Our results showed that the hyperalgesia appeared on the 4th day and reached the maximal level on the 14th day after operation. The expression of the C-fos also increased significantly and reached its maximal level on the 14th day after the touch-stimulus. Meanwhile, the TrkA expression was elevated significantly in both groups, as compared with basic data, and the difference was statistically significant (P<0.05). It is concluded that the level of the C-fos expression changed with the paw withdrawal threshold variation and increased markedly following the innoxious touch-stimulus. The expression of the TrkA receptors also increased gradually following the development of the neuropathic pain. The results suggest that C-fos may play a crucial role in the development of the hyperalgesia in the earlier-time of the neuropathic pain, but TrkA receptors may be involved in the long-lasting adaptive changes of the central pathway in neuropathic pain.

Mechanism of persistent hyperalgesia in neuropathic pain caused by chronic constriction injury

Transmembrane member 16 A(TMEM16 A) is involved in many physiological functions, such as epithelial secretion, sensory conduction, nociception, control of neuronal excitability, and regulation of smooth muscle contraction, and may be important in peripheral pain transmission. To explore the role of TMEM16 A in the persistent hyperalgesia that results from chronic constriction injury-induced neuropathic pain, a rat model of the condition was established by ligating the left sciatic nerve. A TMEM16 A selective antagonist(10 μg T16 Ainh-A01) was intrathecally injected at L5–6. For measurement of thermal hyperalgesia, the drug was administered once at 14 days and thermal withdrawal latency was recorded with an analgesia meter. For measurement of other indexes, the drug was administered at 12 days,once every 6 hours, totally five times. The measurements were performed at 14 days. Western blot assay was conducted to analyze TMEM16 A expression in the L4–6 dorsal root ganglion. Immunofluorescence staining was used to detect the immunoreactivity of TMEM16 A in the L4–6 dorsal root ganglion on the injured side. Patch clamp was used to detect electrophysiological changes in the neurons in the L4–6 dorsal root ganglion. Our results demonstrated that thermal withdrawal latency was shortened in the model rats compared with control rats.Additionally, TMEM16 A expression and the number of TMEM16 A positive cells in the L4–6 dorsal root ganglion were higher in the model rats, which induced excitation of the neurons in the L4–6 dorsal root ganglion. These findings were inhibited by T16 Ainh-A01 and confirm that TMEM16 A plays a key role in persistent chronic constriction injury-induced hyperalgesia. Thus, inhibiting TMEM16 A might be a novel pharmacological intervention for neuropathic pain. All experimental protocols were approved by the Animal Ethics Committee at the First Affiliated Hospital of Shihezi University School of Medicine, China(approval No. A2017-170-01) on February 27, 2017.

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.

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).

Aloin attenuates chronic constriction injury-induced neuropathic pain in rats by inhibiting inflammatory cytokines and oxidative stress

Objective:To investigate the effect of aloin against chronic constriction injury(CCI)-induced neuropathic pain in rats.Methods:Rats were randomly divided into 7 groups:GroupⅠ(normal control),GroupⅡ(sham-operated),GroupⅢ(CCI control)and GroupⅣ,Ⅴ,Ⅵ,andⅦ,which underwent CCI surgery and then were administered with aloin(5 mg/kg,p.o.;25 mg/kg,p.o.;125 mg/kg,p.o.)and gabapentin(50 mg/kg,p.o.),respectively for 14 days.Peripheral neuropathy was induced by silk ligatures(4-0)loosely placed around the sciatic nerve.Nociceptive thresholds against mechanical stimuli(Von-Frey filaments)and thermal stimuli(12℃and 40℃)were measured at midplantar paw region ipsilateral to the compressed nerve on day-3,7,11,and 14.The concentration of cytokines including tumor necrosis factor-α(TNF-α),interleukin-6,and interleukin-1βwas estimated at day-7.At day 14,motor nerve conduction velocity was determined under urethane anesthesia(1.25 g/kg).Oxidative stress parameters(malondiadehyde,glutathione,catalase,and superoxide dismutase)were estimated in sciatic nerve homogenates at day 14.Representative nerve samples were processed for histological investigations.Results:Aloin significantly reduced CCI-induced mechanical and thermal allodynia.It also improved motor nerve conduction velocity and decreased oxidative stress in nerve tissues.In addition,it decreased pro-inflammatory cytokine levels and restored the histoarchitecture of compressed sciatic nerve.Conclusions:Aloin mitigates CCI-induced neuropathic pain in rats by inhibiting oxidative stress and pro-inflammatory cytokines in the afflicted sciatic nerve.

Molecular mechanisms underlying the effects of acupuncture on neuropathic pain

Acupuncture has been used to treat neuropathic pain for a long time, but its mechanisms of action remain unknown. In this study, we observed the effects of electroacupuncture and manual acu- puncture on neuropathic pain and on ephrin-B/EphB signaling in rats models of chronic constriction injury-induced neuropathic pain. The results showed that manual acupuncture and electroacu- puncture significantly reduced mechanical hypersensitivity following chronic constriction injury, es- pecially electroacupuncture treatment. Real-time PCR results revealed that ephrin-B1/B3 and EphB1/B2 mRNA expression levels were significantly increased in the spinal dorsal horns of chronic constriction injury rats. Electroacupuncture and manual acupuncture suppressed the high expres- sion of ephrin-B1 mRNA, and elevated EphB3/B4 mRNA expression. Electroacupuncture signifi- cantly enhanced the mRNA expression of ephrin-B3 and EphB3/B6 in the dorsal horns of neuro- pathic pain rats. Western blot results revealed that electroacupuncture in particular, and manual acupuncture, significantly up-regulated ephrin-B3 protein levels in rat spinal dorsal horns. The re- sults of this study suggest that acupuncture could activate ephrin-B/EphB signaling in neuropathic pain rats and improve neurological function.

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.

Recent evidence for activity-dependent initiation of sympathetic sprouting and neuropathic pain

Traumatic injury or inflammatory irritation of the peripheral nervous system often leads to persistent pathophysiological pain states.It has been well-documented that,after peripheral nerve injury or inflammation,functional and anatomical alterations sweep over the entire peripheral nervous system including the peripheral nerve endings,the injured or inflamed afferent fibers,the dorsal root ganglion(DRG),and the central afferent terminals in the spinal cord.Among all the changes,ectopic discharge or spontaneous activity of primary sensory neurons is of great clinical interest,as such discharges doubtless contribute to the develop-ment of pathological pain states such as neuropathic pain.Two key sources of abnormal spontaneous activity have been identified following peripheral nerve injury:the injured afferent fibers(neuroma) leading to the DRG,and the DRG somata.The purpose of this review is to provide a global account of the abnormal spontaneous activity in various animal models of pain.Particular attention is focused on the consequence of peripheral nerve injury and localized inflammation.Further,mechanisms involved in the generation of spontaneous activity are also reviewed;evidence of spontaneous activity in contributing to abnormal sympathetic sprouting in the axotomized DRG and to the initiation of neuropathic pain based on new findings from our research group are discussed.An improved understanding of the causes of spontaneous activity and the origins of neuropathic pain should facilitate the development of novel strategies for effective treatment of pathological pain.

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.

The Primary Motor Cortex Stimulation Attenuates Cold Allodynia in a Chronic Peripheral Neuropathic Pain Condition in <i>Rattus norvegicus</i>

Background: The primary motor cortex (M1) stimulation (MCS) is a useful tool for attenuation of the peripheral neuropathic pain in patients with pharmacologically refractory pain. Furthermore, that neurological procedure may also cause antinociception in rodents with neuropathic pain. Cold allodynia is a frequent clinical finding in patients with neuropathic pain, then, we evaluated if an adapted model of neuropathy induced by chronic constriction injury (CCI) of the ischiadicus nervus (sciatic nerve) produces cold allodynia in an animal model of chronic pain. In addition, we also investigated the effect of the electrical stimulation of the M1 on chronic neuropathic pain condition in laboratory animals. Methods: Male Wistar rats were used. An adapted model of peripheral mononeuropathy induced by CCI was carried out by placing a single loose ligature around the right sciatic nerve. The acetone test was used to evaluate the cold allodynia in CCI or Sham (without ligature) rats. The MCS (M1) was performed at low-frequency (20 μA, 100 Hz) during 15 s by deep brain stimulation (DBS-Thomas Recording device) 21 days after CCI or Sham procedures. The cold allodynia was measured before and immediately after the neurostimulation of M1 in the following time-window: 0, 15 and 30 min after MCS. Results: Cold allodynia threshold increased in animals with chronic neuropathic pain submitted to the acetone test 21 days after the CCI surgery. The M1-stimulation by DBS procedure decreased the cold allodynia immediately and until 30 min after M1-stimulation in rats with chronic neuropathic pain. Conclusion: The current proposal for a CCI model by a single loose ligature of the sciatic nerve can be employed as an experimental model of chronic neuropathic pain in rats submitted to peripheral nervous system injury. The M1-stimulation produced antinociception in rats with chronic neuropathic pain. Thus, we reinforced that the MCS decreases cold allodynia in laboratory animals submitted to persistent sciatic nerve constriction and can be a more reasonable procedure for the treatment of chronic intractable neuropathic pain.

富血小板血浆凝胶缓解CCI模型大鼠周围神经痛及其改善中枢海马组织炎性机制研究

目的建立大鼠坐骨神经慢性压迫损伤(CCI)模型,观察富血小板血浆凝胶(PRP)对CCI大鼠坐骨神经病理性疼痛进展期痛域的影响,并探讨其对中枢海马组织的抗炎作用机制。方法选择SPF级雄性SD大鼠50只,其中10只用于制备PRP,其余40只采用随机数表法分为空白对照组、假手术组、CCI组和CCI+PRP组,每组10只。比较各组大鼠在术前1 d、术后6 h、1 d、3 d、7 d足底机械性缩足反射阈值(MWT)和热辐射缩足潜伏期(TWL)变化;比较术后7 d时各组大鼠海马区肿瘤坏死因子(TNF-α)、白细胞介素-1β(IL-1β)和高迁移率组蛋白1(HMGB1)及其下游Toll样受体-4(TLR4)、糖基化终产物受体(RAGE)mRNA表达水平。结果空白组与假手术组各时间点大鼠MMT和TWL比较差异均无统计学意义(P>0.05);CCI组和CCI+PRP组大鼠术后MMT和TWL值与术前比较差异均有统计学意义(P<0.05);CCI组和CCI+PRP组大鼠术后各时间点MWT和TWL比较差异均有统计学意义(P<0.05)。术后7 d时,对照组和假手术组大鼠海马组织的TNF-α、IL-1β、HMGB1含量以及HMGB1、TLR4和RAGE mRNA表达水平比较差异均无统计学意义(P>0.05),而CCI组和CCI+PRP组与对照组或假手术组比较差异均具有统计学意义(P<0.05);术后7 d时,CCI+PRP组与CCI组大鼠海马组织的TNF-α、IL-1β、HMGB1含量以及HMGB1、TLR4和RAGE mRNA表达水平比较,差异均具有统计学意义(P<0.05)。结论富血小板血浆可有效延缓CCI大鼠神经病理性疼痛进展期痛域,抑制中枢海马组织炎性反应,其机制可能与富血小板血浆通过HMGB1-TLR4/RAGE信号通路抑制TNF-α、IL-1β表达水平有关。

Radial shock wave therapy in the treatment of chronic constriction injury model in rats： a preliminary study

Background Pain physicians pay close attention to neuropathic pain （NP）,since there is currently no ideal treatment.Radial shock wave therapy （RSWT） is a noninvasive treatment to chronic pain of soft tissue disorders.So far,there is no information on the use of RSWT for the treatment of NP.Therefore we observe the effects of RSWT on a NP model induced by chronic constriction injury （CCI） in rats.Methods Four different energy densities （1.0,1.5,2.0 and 2.5 bar） RSWT administered as a single session or repeated sessions in rats with NP induced by CCI of the sciatic nerve.The analgesic effect was assessed by measuring mechanical withdrawal threshold （MWT） and thermal withdrawal latency （TWL）.The safety was assessed through calculating sciatic functional index （SFI）.Results MWT and TWL increased after a single session of RSWT from day 1 to day 5 but retumed to baseline levels by day 10.Following repeated sessions of RSWT,both the MWT and TWL were significantly higher than NP group （P ＜ 0.01）for at least 4 weeks.In addition,no significant changes of SFI were observed in any groups after repeated sessions of RSWT and no increased pain or other side effects in any animals.Conclusions A single session of RSWT is rapidly effective in the treatment of CCI,but the efficacy maintained in a short period.However,repeated sessions of RSWT have prolonged efficacy.

Pulsed radiofrequency alleviated neuropathic pain by down-regulating the expression of substance P in chronic constriction injury rat model

Background:Pulsed radiofrequency(PRF),as a non-invasive treatment of neuropathic pain(NP),has been widely administered clinically.Previous studies have shown that PRF has the potential to improve hyperalgesia in animal models of NP.However,there have been few reports to clarify whether the mechanism of PRF treatment of NP involves intervention in the expression of substance P(SP).Therefore,this study administered PRF treatment to chronic constriction injury(CCI)model rats and observed the sciatic nerve mechanical pain threshold and SP expression in the spinal cord to explore the mechanism of PRF treatment.Methods:A total of 96 Sprague-Dawley rats were randomly divided into the sham-surgery-sham-treatment group(S-S group),the sham-surgery-PRF group(S-P group),the CCI-sham-treatment group(C-S group),and the CCI-PRF group(C-P group).The C-S group and the C-P group underwent sciatic nerve CCI,while the other groups received a sham operation.At 14 days after the operation,the C-P group and the S-P group were treated with PRF for 300 s.We recorded the hindpaw withdrawal threshold(HWT)and the thermal withdrawal latency(TWL)of rats in the various groups at baseline,before treatment(0 days),and at 1,7,14,and 28 days after treatment.L4 to L6 spinal cord tissues were taken before treatment(0 days)and 1,7,14,and 28 days after treatment.The transcription and translation of SP were measured by quantitative polymerase chain reaction and Western blotting,respectively.Results:The HWT and the TWL in the C-P group 28 days after PRF treatment were significantly higher than those in the C-S group(95%confidence interval[CI]:5.84–19.50,P<0.01;95%CI:2.58–8.69,P=0.01).The expression of SP in the C-P group 28 days after PRF treatment was significantly lower than that in the C-S group(95%CI:1.17–2.48,P<0.01).Conclusions:PRF may alleviate CCI-induced NP by down-regulating the expression of SP in the spinal cord of CCI model rats.

颅痛宁颗粒对眶下神经缩窄环术诱导三叉神经痛大鼠的治疗作用研究

目的研究颅痛宁颗粒对三叉神经痛模型大鼠的治疗作用,为其临床应用提供参考资料。方法采用眶下神经缩窄环术(ION-CCI)制备大鼠三叉神经痛模型,大鼠随机分为正常组、假手术组、模型组、卡马西平阳性药组、颅痛宁高剂量组(2.70 g生药·kg^(-1)·d^(-1))、颅痛宁低剂量组(1.35 g生药·kg^(-1)·d^(-1))。Von Frey毛刷测定大鼠触须垫机械痛阈值,生化法检测血液血流变和凝血功能,HE染色观察眶下神经病理变化,Western blot技术检测三叉神经内P38和P-P38的蛋白水平。结果颅痛宁颗粒能提高模型大鼠的痛阈值(P<0.05,P<0.01)降低模型大鼠血浆黏度(P<0.05,P<0.01)和全血还原黏度(P<0.05,P<0.01),提高模型大鼠血流变能力;提高模型大鼠血液凝血酶原时间(prothrombintime,PT)、活化部分凝血活酶时间(activated partial thromboplatin time,APTT)和凝血酶时间(thrombin time,TT)水平(P<0.05,P<0.01),降低模型大鼠纤维蛋白原(fibrinogen,FIB)水平(P<0.01),改善凝血功能;改善模型大鼠眶下神经的病理改变;并降低模型大鼠三叉神经内P-P38的表达量(P<0.01)。结论颅痛宁颗粒具有改善三叉神经痛作用,可能与其活血化瘀功能有关。

Effect of Pulsed Radiofrequency on Rat Sciatic Nerve Chronic Constriction Injury： A Preliminary Study

Background：Pulsed radiofrequency （PRF） application to the dorsal root ganglia can reduce neuropathic pain （NP） in animal models,but the effect of PRF on damaged peripheral nerves has not been examined.We investigated the effect of PRF to the rat sciatic nerve （SN） on pain-related behavior and SN ultrastructure following chronic constriction injury （CCI）.Methods：The analgesic effect was measured by hindpaw mechanical withdrawal threshold （MWT） and thermal withdrawal latency （TWL）.Twenty rats with NP induced by ligating the common SN were then randomly divided into a PRF treatment group and a sham group.The contralateral SN served as a control.The MWT and TWL were determined again 2,4,6,8,10,12,and 14 days after the PRF or sham treatment.On day 14,ipsilateral and contralateral common SNs were excised and examined by electron microscopy.Results：Ipsilateral MWT was significantly reduced and TWL significantly shorter compared to the contralateral side 14 days after CCI （both P =0.000）.In the PRF group,MWT was significantly higher and TWL significantly longer 14 days after the PRF treatment compared to before PRF treatment （both P =0.000）,while no such difference was observed in the sham group （P ＞ 0.05）.Electron microscopy revealed extensive demyelination and collagen fiber formation in the ipsilateral SN of sham-treated rats but sparse demyelination and some nerve fiber regrowth in the PRF treatment group.Conclusions：Hyperalgesia is relieved,and ultrastructural damage ameliorated after direct PRF treatment to the SN in the CCI rat model of NP.

Pulsed radiofrequency inhibits expression of P2X3 receptors and alleviates neuropathic pain induced by chronic constriction injury in rats

Background:Pulsed radiofrequency (PRF) is a minimally invasive interventional technique that provides a novel and effective treatment strategy for neuropathic pain (NP).PRF is advantageous because it does not damage nerves and avoids sensory loss after treatment.At present,animal studies have demonstrated that PRF is safe and effective for relieving the NP associated with sciatic nerve damage in rats with chronic constriction injury (CCI).However,the mechanism through which this effect occurs is unknown.An increasing body of evidence shows that the expression of the P2X ligand-gated ion channel 3 (P2X3) receptor is closely related to NP;this study was to investigate whether the expression of this receptor is involved in NP relief due to PRF.Methods:A total of 36 healthy adult male Sprague-Dawley (SD) rats were randomly divided into three groups:Sham group,CCI group,and PRF group.The right sciatic nerve was ligated in CCI group and PRF group to establish a CCI model;the right sciatic nerve was separated but not ligated in Sham group.On day 14 after the operation,PRF was administered to the ligated sciatic nerve in PRF group (42℃,45 V,2 min).A non-live electrode was placed at the exposed sciatic nerve for the rats in Sham and CCI groups.The hindpaw withdrawal threshold (HWT) and thermal withdrawal latency (TWL) were measured at the right hindpaw at different time points before and after PRF or sham therapy.On day 28 after treatment,the dorsal root ganglion (DRG) and spinal dorsal horn of the right L4-6 were harvested from each group to determine the mRNA and protein levels of the P2X3 receptor.Results:On day 28 after PRF treatment,the HWT (8.33 ± 0.67 g vs.3.62 ± 0.48 g) and TWL (25.42 ± 1.90 s vs.15.10 ± 1.71 s) were significantly higher in PRF group as compared to CCI group (P < 0.05).The mRNA expression of the P2X3 receptor in the DRG in PRF group was 23.7% lower than that in CCI group (P < 0.05),in the spinal dorsal horns in PRF group was 22.7% lower than that in CCI group (P < 0.05).The protein expression of the P2X3 receptor in the DRG in PRF group was 27.8 % lower than that in CCI group (P < 0.05),in the spinal dorsal horns in PRF group was 35.6% lower than that in CCI group (P < 0.05).Conclusion:PRF possibly reduces NP in CCI rats by inhibiting the expression of the P2X3 receptor in the L4-6 DRG and spinal dorsal horns.

Treatment with acetyl-L-carnitine exerts a neuroprotective effect in the sciatic nerve following loose ligation:a functional and microanatomical study

Peripheral neuropathies are chronic painful syndromes characterized by allodynia,hyperalgesia and altered nerve functionality.Nerve tissue degeneration represents the microanatomical correlate of peripheral neuropathies.Aimed to improve the therapeutic possibilities,this study investigated the hypersensitivity and the neuromorphological alterations related to the loose ligation of the sciatic nerve in rats.Effects elicited by treatment with acetyl-L-carnitine（ALCAR） in comparison to gabapentin were assessed.Axonal injury,reduction of myelin deposition and accumulation of inflammatory cells were detected in damaged nerve.A decrease of phosphorylated 200-k Da neurofilament（NFP） immunoreactivity and a redistribution in small clusters of myelin basic like-protein（MBP） were observed in ipsilateral nerves.Treatment with ALCAR（100 mg/kg intraperitoneally-i.p.） and gabapentin（70 mg/kg i.p.） administered bis in die for 14 days induced a significant pain relieving effect.ALCAR,but not gabapentin,significantly countered neuromorphological changes and increased axonal NFP immunoreactivity.These findings indicate that both ALCAR and gabapentin significantly decreased the hypersensitivity related to neuropathic lesions.The observation of the positive ALCAR effect on axonal and myelin sheath alterations in damaged nerve supports its use as neurorestorative agent against neuropathies through mechanism（s） consistent to those focused in this study.

miR-132-3p靶向调节Ptch1减轻慢性压迫性神经损伤小鼠神经性疼痛

背景:神经病理性疼痛的发病机制复杂,病理过程繁多,miR-132在神经病理性疼痛传导通路中异常表达,影响疼痛的发生、发展过程。目的:探讨miR-132-3p在慢性压迫性神经损伤小鼠神经性疼痛中所发挥的作用及机制。方法:①小鼠小胶质细胞BV2经100μg/L脂多糖刺激建立活化模型,采用Western blot检测小胶质细胞激活标记物IBA1的表达,RT-qPCR检测miR-132-3p的表达。将miR-132-3p mimic或inhibitor分别转染至BV2细胞,采用Western blot检测IBA1以及P2X4R的表达。预测并验证miR-132-3p的靶向调节作用,将Ptch1表达载体pcDNA-Ptch1或si-Ptch1转染BV2细胞24 h后用脂多糖刺激培养24 h,采用Western blot检测IBA1、P2X4R以及Shh信号通路标记蛋白的表达。BV2细胞共转染miR-132-3p-mimic和pcDNA-Ptch124 h后用脂多糖刺激培养24 h,采用Western blot检测上述蛋白的表达。②30只C57BL/6小鼠随机分为对照组(n=6),假手术组(n=6),模型组(n=6),NC-mimic组(n=6),miR-132-3p-mimic组(n=6),后两组经鞘内注射NC-mimic和miR-132-3p-mimic,检测各组小鼠机械缩足反射阈值和热阈值,行为学检测后取背根神经节,采用RT-qPCR检测miR-132-3p的表达,Western blot检测Ptch1、P2X4R和Shh通路标记蛋白的表达,进一步验证miR-132-3p在慢性压迫性神经损伤小鼠神经性疼痛中发挥的作用及机制。结果与结论:①与对照组比较,脂多糖刺激促进BV2细胞的激活(P<0.05),下调miR-132-3p的表达(P<0.05);②miR-132-3p通过靶向调节Ptch1抑制Shh信号通路的激活,并进一步抑制BV2细胞的激活以及P2X4R的表达,过表达Ptch1可以逆转miR-132-3p-mimic的作用(P<0.05);③成功建立慢性压迫性神经损伤模型,与注射NC-mimic组相比,鞘内注射miR-132-3p-mimic下调Ptch1的表达(P<0.05),抑制Shh信号通路的激活(P<0.05),减少P2X4R的表达(P<0.05),并显著提高慢性压迫性神经损伤小鼠的机械缩足反射阈值和热阈值(P<0.01);④结果表明,miR-132-3p通过靶向调节Ptch1抑制Shh信号通路的激活,减轻慢性压迫性神经损伤小鼠的神经性疼痛。

芒果苷对CCI大鼠神经病理性疼痛的改善作用

目的:探究芒果苷对慢性缩窄性损伤(CCI)大鼠神经病理性疼痛的作用及机制。方法:采用成年SpragueDawley大鼠构建CCI模型,以模拟临床神经病理性疼痛。将大鼠随机分为假手术组(Sham组)、CCI组、CCI+Man组[手术后立即用40 mg/(kg·d)芒果苷灌胃,连续治疗17 d],10只/组。术后连续17 d观察缩爪机械阈值(PWMT)和缩爪热潜伏期(PWTL);术后17 d,处死大鼠,ELISA检测脊髓中细胞因子IL-1β、IL-6及趋化因子CCL2、CCR2表达水平;免疫荧光法检测脊髓神经元中Cleaved caspase-3和pJNK蛋白表达水平;免疫组化法和Western blot分析脊髓中c-Fos蛋白表达水平。结果:与Sham组相比,CCI组大鼠术后第1~17天的PWMT和PWTL显著降低,脊髓中促炎因子IL-6、IL-1β,趋化因子CCL2、CCR2及c-Fos蛋白水平明显升高(P<0.001);脊髓神经元细胞中Cleaved caspase-3和pJNK蛋白水平明显升高(P<0.001)。经芒果苷治疗后,CCI组大鼠术后第1~17天的PWMT和PWTL显著升高,脊髓中促炎因子IL-6、IL-1β,趋化因子CCL2、CCR2及c-Fos蛋白水平明显降低(P<0.01);脊髓神经元细胞中Cleaved caspase-3和pJNK蛋白水平明显降低(P<0.01)。结论:芒果苷对CCI大鼠的神经病理性疼痛具有改善作用,其可能与降低脊髓炎症、凋亡、c-Fos及pJNK蛋白表达有关。

基于TLR4/NF-κB通路研究蒺藜总皂苷对周围神经病理性疼痛的镇痛作用

目的:基于TLR4/NF-κB通路研究蒺藜总皂苷(gross saponins from tribulus terrestris,GSTT)对大鼠慢性坐骨神经损伤(chronic constriction injury,CCI)所引起的周围神经病理性疼痛是否具有镇痛作用。方法:选取雄性SD大鼠40只,随机分为假手术组(SHAM组)、CCI组、GSTT 100 mg/kg+CCI组、GSTT 200 mg/kg+CCI组、普瑞巴林+CCI组(阳性对照)5组,每组8只。除SHAM组,其余各组均制备CCI大鼠模型,分别以药物处理后,检测各组大鼠机械缩足反射阈值(paw withdrawal mechanical threshold,PWMT)、热敏潜伏期;以HE染色检测各组大鼠脊髓及背根神经节组织病理形态变化;免疫组化检测脊髓及背根神经节组织中NF-κB的表达。结果:与SHAM组相比,CCI组大鼠PWMT、热敏潜伏期明显降低(P<0.05);损伤侧脊髓背角及背根神经节的神经元、胶质细胞染色较深,并出现肿胀、萎缩等损伤,细胞核浓缩、丢失;损伤侧脊髓背角及背根神经节中NF-κB表达水平明显增高(P<0.05)。与CCI组相比,GSTT 100 mg/kg+CCI组、200 mg/kg+CCI组,普瑞巴林+CCI组大鼠PWMT、热敏潜伏期升高(P<0.05),上述病理变化也明显改善,损伤侧脊髓背角及背根神经节中NF-κB水平降低。结论:GSTT对CCI大鼠引起的周围神经病理性疼痛具有镇痛作用,可能与TLR4/NF-κB通路有关。