Electroacupuncture versus celecoxib for neuropathic pain in rat SNL model

Though acupuncture has long been used to treat various kinds of pain, its mechanisms remain partly understood. Our recent study has shown that it may inhibit cyclooxygenase-2 (COX-2) in the spinal dorsal horn where COX-2 is upregulated after the development of neuropathic pain following spinal nerve ligation (SNL). The current study directly compared the effect of acupuncture with COX-2 inhibitor celecoxib in the spinal cord after SNL in rats. After L5 SNL, the rats were treated either with acupuncture applied to Zusanli (ST36) and Sanyinjiao (SP6) bilaterally with or without electrical stimulation (2 Hz, 0.5–1–2 mA) four times over 22 days, and/or celecoxib fed daily. Paw-withdrawal-threshold to mechanical stimulation and paw-withdrawal-latency to thermal test were tested for neuropathic pain at four intervals following the treatments in comparison with the pre-treatment and non-treatment controls. The results demonstrate that electroacupuncture (EA) had a long lasting and better analgesic effect than celecoxib in reducing neuropathic hypersensitivity. Though COX-2 expression in the spinal L4–L6 dorsal horn by immunostaining was significantly reduced by acupuncture just as well as by celecoxib, the superior analgesic mechanism of acupuncture appears well beyond COX-2 inhibition alone.     

脊髓刺激术对神经病理性痛模型大鼠脊髓背角内NR2B受体和星形胶质细胞激活的影响

目的:探讨脊髓刺激术(spinal cord stimulation,SCS)对L5脊神经结扎(spinal nerve ligation,SNL)诱导的神经病理性痛(neuropathic pain,NP)大鼠脊髓背角内NMDA受体亚单位NR2B的表达和星形胶质细胞激活的影响。方法:成年雄性SD大鼠48只,随机分为4组:正常组(不做任何处理);SCS组(植入SCS装置并给予SCS刺激);SNL+sham SCS组(给予SNL手术并植入SCS装置,但不进行刺激);SNL+SCS组(SNL手术并给予SCS刺激)。SCS刺激是在SNL术后第6～10 d进行(8 h/d),第10 d刺激结束后处死动物。运用行为学方法检测慢性痛状态下大鼠后肢对机械性刺激的反应阈值;采用免疫组织化学染色和Western blot方法分别检测脊髓背角内NR2B和星形胶质细胞的标志物GFAP的表达变化。结果:(1)SNL术后大鼠手术侧后足机械性痛敏显著增加,第6～10 d给予SCS刺激后,可观察到大鼠的痛行为学表现有明显缓解;(2)免疫组化结果显示:与SNL+sham SCS组相比,SNL+SCS组大鼠脊髓背角内NR2B和GFAP免疫阳性细胞的数量显著减少;(3)Western blot结果显示:给予SCS刺激后,SNL大鼠腰膨大段脊髓背角内NR2B的表达量显著下调,同时GFAP的表达量也明显有所降低。结论:给予SCS刺激可以有效地缓解SNL模型大鼠的神经病理性痛的行为学表现;该作用可能与SCS刺激抑制脊髓背角内NR2B的表达和星形胶质细胞的激活密切相关。     

Activation of microglia and p38 mitogen-activated protein kinase in the dorsal column nucleus contributes to tactile allodynia following peripheral nerve injury

The activation of glial cells in the CNS has been suggested to be involved in abnormal pain sensation after peripheral nerve injury. Previous studies demonstrated phosphorylation of p38 mitogen-activated protein kinase (MAPK) in spinal cord glial cells after peripheral nerve injury, and such phosphorylation has been suggested to be involved in the development of neuropathic pain. The aim of this study was to examine the dorsal column nuclei for phosphorylation of p38 MAPK following peripheral nerve injury and to explore a possibility of its contribution to neuropathic pain. Immunohistochemical labeling for phosphorylated p38 (p-p38) MAPK was performed in histological sections of the rat spinal cord and medulla oblongata after the fifth lumbar (L5) spinal nerve ligation (SNL). The number of p-p38 MAPK-immunoreactive (IR) cells was significantly increased in the L5 dorsal horn and the gracile nucleus ipsilateral to the injury at days 3-21 after SNL. Double immunofluorescence labeling with cell-specific markers revealed that p-p38 MAPK-IR cells co-expressed OX-42, suggesting their microglial identity. Increased immunofluorescence labeling for OX-42 indicated that microglial cells were activated by SNL in the L5 dorsal horn and the gracile nucleus ipsilateral to the injury. Continuous infusion of a p38 MAPK inhibitor into the cisterna magna for 14 days beginning on the day of SNL suppressed the development of tactile allodynia, but not thermal hyperalgesia induced by nerve injury. These results demonstrate that SNL activates p38 MAPK pathway in microglia in the gracile nucleus as well as in the spinal cord dorsal horn. Activation of p38 MAPK in medullary microglia may contribute to the pathogenesis of neuropathic pain.     

TWIK-Related Spinal Cord K+ Channel Expression Is Increased in the Spinal Dorsal Horn after Spinal Nerve Ligation

Purpose

The TWIK-related spinal cord K⁺ channel (TRESK) has recently been discovered and plays an important role in nociceptor excitability in the pain pathway. Because there have been no reports on the TRESK expression or its function in the dorsal horn of the spinal cord in neuropathic pain, we analyzed TRESK expression in the spinal dorsal horn in a spinal nerve ligation (SNL) model.

Materials and Methods

We established a SNL mouse model by using the L5-6 spinal nerves ligation. We used real-time polymerase chain reaction and immunohistochemistry to investigate TRESK expression in the dorsal horn and L5 dorsal rot ganglion (DRG).

Results

The SNL group showed significantly higher expression of TRESK in the ipsilateral dorsal horn under pain, but low expression in L5 DRG. Double immunofluorescence staining revealed that immunoreactivity of TRESK was mostly restricted in neuronal cells, and that synapse markers GAD67 and VGlut2 appeared to be associated with TRESK expression. We were unable to find a significant association between TRESK and calcineurin by double immunofluorescence.

Conclusion

TRESK in spinal cord neurons may contribute to the development of neuropathic pain following injury.     

曲古抑菌素A通过抑制脊髓背角内的炎症反应减轻大鼠神经病理性痛

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

Mouse strains that lack spinal dynorphin upregulation after peripheral nerve injury do not develop neuropathic pain

Several experimental models of peripheral neuropathy show that a significant upregulation of spinal dynorphin A and its precursor peptide, prodynorphin, is a common consequence of nerve injury. A genetically modified mouse strain lacking prodynorphin does not exhibit sustained neuropathic pain after nerve injury, supporting a pronociceptive role of elevated levels of spinal dynorphin. A null mutation of the gamma isoform of protein kinase C (PKCgamma KO [knockout]), as well as an inbred mouse strain, 129S6, also does not manifest behavioral signs of neuropathic pain following peripheral nerve injury. The objective of this study was to extend our observations to these genetic models to test the hypothesis that elevated levels of spinal dynorphin are essential for the maintenance of abnormal pain. In PKCgamma wild-type mice and the outbred mouse strain ICR, ligation of the L5 and L6 spinal nerves (SNL) elicited both tactile hypersensitivity and thermal hyperalgesia. Both strains showed a significant elevation in dynorphin in the lumbar spinal dorsal horn following SNL. Spinal administration of an anti-dynorphin A antiserum blocked the thermal and tactile hypersensitivity in both strains of mice. However, the PKCgamma KO mice and the 129S6 mice (which express PKCgamma) did not show abnormal pain after SNL; neither strain showed elevated levels of spinal dynorphin. The multiple phenotypic deficits in PKCgamma KO mice confound the interpretation of the proposed role of PKCgamma-expressing spinal neurons in neuropathic pain states. Additionally, the data show that the regulation of spinal dynorphin expression is a common critical feature of expression of neuropathic pain.     

脊髓刺激术对神经病理性痛模型大鼠痛行为和脊髓背角内小胶质细胞激活的影响

目的:探讨脊髓刺激术(spinal cord stimulation,SCS)对神经病理性痛(neuropathic pain,NP)模型大鼠痛行为及脊髓背角内小胶质细胞激活的影响。方法:成年大鼠20只,随机分为4组:(1)正常对照组(control组);(2)SCS组:正常大鼠给予SCS刺激;(3)脊神经结扎(spinal nerve ligation,SNL)假刺激组(SNL+shamSCS组):SNL且植入SCS装置,但不刺激;(4)SNL+SCS组:SNL且给予SCS刺激。术前连续3 d、术后第5 d检测各组大鼠足底机械痛敏阈值(mechanical withdrawal threshold,MWT)。SCS组和SNL+SCS组术后第2-5 d给予SCS刺激,每d持续8 h;且在每次给予SCS 8 h刺激前进行90 min行为学测试,即SCS刺激30 min,以及刺激结束后的60 min内(共90 min),每15 min测量一次MWT。在第5 d给予SCS 8 h刺激结束后处死动物,利用免疫组织化学染色结合平均光密度(average optical density,AOD)分析的方法检测各组大鼠腰5节段脊髓背角内小胶质细胞特异性标志物OX-42的表达情况。结果:(1)行为学结果显示:术后第5 d,SNL+shamSCS组和SNL+SCS组大鼠手术侧后爪的MWT由术前26.00±0.0 g分别降至5.50±0.96 g和6.40±0.40 g(P<0.05);SNL+SCS组给予SCS刺激30 min后大鼠手术侧后爪的MWT明显有所提高,达16.20±2.60 g,与刺激前(6.40±0.40 g)相比有显著性差异(P<0.05);但停止SCS刺激60 min后,大鼠的MWT明显有所下降,与刺激前几乎没有明显差别。(2)免疫组化染色结果显示:术后第5 d,SNL+SCS组脊髓背角内OX-42的表达明显弱于SNL+shamSCS组,但二者都强于control组和SCS组;AOD结果也证实:SNL+SCS组大鼠脊髓背角内OX-42的AOD(1.29±0.28)明显低于SNL+shamSCS组(2.66±0.38),但仍高于control组(0.14±0.21)和SCS组(0.24±0.08)。结论:SCS对SNL模型大鼠的神经病理性痛有较好的镇痛效果;该作用可能与SCS刺激显著抑制脊髓背角内小胶质细胞的激活密切相关。     

大鼠外周神经损伤后脊髓背角HMGB1表达上调参与机械性痛觉超敏

目的:研究HMGB1(high mobility group box-1)在神经病理性痛大鼠脊髓水平的表达变化,探索HMGB1在神经病理性痛发生发展中的作用,为治疗神经病理性痛提供新的理论依据和治疗靶点。方法:(1)雄性SD大鼠(180～220)g 12只,随机均分为三组:NS组:鞘内注射生理盐水;A组:鞘内注射HMGB1 1μg;B组:鞘内注射HMGB1 10μg。盲法用von Frey测定给药前及给药后1 h、1、3、7、14、21、28 d大鼠50%机械缩足阈值(me-chanical withdrawal threshold,MWT);(2)雄性SD大鼠(180～220)g 5只,免疫荧光双标观察HMGB1在脊髓背角的表达定位;(3)雄性SD大鼠(180～220)g 42只,随机均分为对照组(6只),SNL模型组(每时间点6只),West-ern Blot方法观察大鼠脊髓背角HMGB1对照及术后1、3、7、14、21、28 d的表达变化。结果:(1)大鼠脊髓鞘内注射HMGB1后诱发长时程机械性痛敏,A组在鞘内给药后7 d MWT明显下降(P<0.01),B组给药后1 h MWT即显著下降,且持续存在至少28 d;(2)免疫荧光双标显示:HMGB1主要表达于NeuN标记的神经元,而GFAP阳性的星形胶质细胞以及OX42阳性的小胶质细胞几乎不表达HMGB1;(3)Western Blot结果显示,脊髓背角HMGB1在SNL模型术后缓慢增高,7 d时增高最为显著,且持续至少28 d。结论:以上结果表明,外周神经损伤后脊髓水平HMGB1的表达上调可能在神经病理性痛的产生和维持中起着重要作用。     

Dexmedetomidine decreases hyperalgesia in neuropathic pain by increasing acetylcholine in the spinal cord

The activation of α2-adrenoceptors has attracted attention as a therapeutic target for neuropathic pain, which remains a clinical challenge. In the present study, we examined the interaction between α2-adrenergic and cholinergic signaling in a rat model of neuropathic pain induced by spinal nerve ligation (SNL). Intrathecal administration of dexmedetomidine, which is a selective α2-adrenoceptor agonist (0.1–1.0 μg), dose-dependently suppressed hyperalgesia in SNL rats but did not alter paw withdrawal thresholds in normal rats. The analgesic effect of dexmedetomidine was abolished by intrathecal pretreatment with idazoxan (30 μg) and atropine (30 μg), which antagonize the α2-adrenoreceptor and muscarinic receptor, respectively. In vivo microdialysis in the lumbar spinal dorsal horn revealed that acetylcholine concentrations increased after dexmedetomidine perfusion (1 μM), but only in SNL rats. The combination of an ineffective dose of intrathecal dexmedetomidine with intraperitoneal donepezil, which is a cholinesterase inhibitor, decreased neuropathic hypersensitivity. These results suggest that plasticity of the spinal noradrenergic–cholinergic axis only occurs in neuropathic pain states. Thus, drug combinations that strengthen the noradrenergic–cholinergic interaction may provide therapeutic benefit in neuropathic pain.     

Changes of expression of glial cell line-derived neurotrophic factor and its receptor in dorsal root ganglions and spinal dorsal horn during electroacupuncture treatment in neuropathic pain rats

Injury to the nervous system occasionally leads to intense and persistent neuropathic pain, which is resistant to conventional analgesic methods. It was reported that electroacupuncture (EA) had potent analgesic effect on neuropathic pain by activating various endogenous transmitters such as the opioid peptides. Glial cell line-derived neurotrophic factor (GDNF) has been hypothesized to play an important role in modulation of nociceptive signals especially during neuropathic pain state. Using immunohistochemistry, Western blot, and RT-PCR analysis techniques, the present study observed the effects of EA on the expression of GDNF and GDNF family receptor alpha-1 (GFRalpha-1, the high-affinity receptor of GDNF) in neuropathic pain rats. The results showed that both protein and mRNA levels of GDNF and GFRalpha-1 in the dorsal root ganglions (DRG), as well as GDNF protein in the spinal dorsal horn, were significantly increased after chronic constriction injury (CCI) of the rats' sciatic nerve and could be further enhanced by EA treatment. The present data demonstrated that EA could activate endogenous GDNF and GFRalpha-1 system of neuropathic pain rats and this might underlie the effectiveness of EA in the treatment of neuropathic pain.     

Pharmacological characterization and gene expression profiling of an L5/L6 spinal nerve ligation model for neuropathic pain in mice

L5/L6 spinal nerve ligation (SNL) in rodents induces behavioral signs similar to the symptoms of neuropathic pain in humans. L5/L6 SNL in rats has been well characterized so far, but there have been few studies using mice. In this study, we established an L5/L6 SNL model in mice and examined the effects of known antinociceptive drugs in the model. We also analyzed the changes in gene expression in dorsal root ganglions with special reference to those which are known to change in a neuropathic pain state to validate the model. Mechanical allodynia in the ipsilateral side paw was observed beginning on day 1 and lasted for at least 2 months following surgery. Diclofenac showed no significant effect on the mechanical allodynia. Gabapentin and pregabalin completely reversed allodynia, but they also caused a decrease in locomotor activity. Duloxetine caused a partial recovery of the threshold. Mexiletine completely reversed allodynia, but it also caused sedation or motor impairment. Morphine caused a partial recovery of the threshold and hyper-locomotion. This mouse L5/L6 SNL model represents a robust mechanical allodynia, which shows a similar pharmacological response to that reported in rats and human patients with neuropathic pain. The pattern changes in gene expression also resembled those reported in rats. This model will therefore be useful for investigation of the effects of novel antinociceptive compounds and the mechanisms of neuropathic pain.     

Studies on the changes of c-fos protein in spinal cord and neurotransmitter in dorsal root ganglion of the rat with an experimental peripheral neuropathy

Animal models for human chronic pain syndromes have been developed and widely used for pain research. One of these neuropathic pain models by Kim and Chung (1992) has many advantages for operation and pain elicitation. In this neuropathic model we have examined the c-fos protein, substance P, CGRP immunoreactivity in dorsal root ganglia and dorsal horn. 50 Sprague-Dawley rats were used for this study. L5 and L6 spinal nerves were ligated tightly to produce the neuropathic pain model. After 2, 4, 8, 16, and 24 hours and 1 week of surgery, rats were anesthetized and sacrificed by perfusion. After confirmation of the roots transected by the surgery, the L5 and L6 dorsal root ganglions and spinal cord were removed and processed for immunohistochemistry. All tissue sections were immunohistochemically stained for substance P, CGRP and c-fos using the peroxidase-antiperoxidase (PAP) method. The number of immunostained substance P and CGRP dorsal root ganglion cells and c-fos immunoreactive dorsal horn cells were counted and analyzed statistically with Mann-Whitney U test. The results are as follows. The number of c-fos protein immunoreactive neurons in the superficial layer of dorsal horn were increased markedly 2 hours after operation, and gradually decreased to normal level 1 week after operation. The number of c-fos protein immunoreactive neurons in the deep layer of the dorsal horn gradually increased to a peak 24 hours after operation, then decreased to the normal level 1 week after operation. The number of substance P and CGRP immunoreactive L5 and L6 dorsal root ganglion neurons were decreased markedly 1 week after the pain model operation. In conclusion, after neuropathic pain model operation, c-fos proteins were immediately expressed in the superficial layer of spinal dorsal horn, thereafter c-fos proteins in the deep layer of spinal dorsal horn were expressed. CGRP and substance P immunoreactive neurons in DRG were decreased markedly 1 week after neuropathic pain model operation. These decrements do not coincide with the other chronic pain models, which show great increases in these pain transmitting substances. Therefore, the relationship between pain and c-fos, SP and CGRP should be investigated further.     

Rostral ventromedial medulla control of spinal sensory processing in normal and pathophysiological states

Complex networks of pathways project from various structures in the brain to modulate spinal processing of sensory input in a top-down fashion. The rostral ventromedial medulla (RVM) in the brainstem is one major final common output of this endogenous modulatory system and is involved in the relay of sensory information between the spinal cord and brain. The net output of descending neurons that exert inhibitory and facilitatory effects will determine whether neuronal activity in the spinal cord is increased or decreased. By pharmacologically blocking RVM activity with the local anesthetic lignocaine, and then measuring evoked responses of dorsal horn neurons to a range of applied peripheral stimuli, our aim was to determine the prevailing descending influence operating in normal anesthetized animals and animals with experimental neuropathic pain. The injection of 0.8 microl 2% lignocaine into the RVM caused a reduction in deep dorsal horn neuronal responses to electrical and natural stimuli in 64% of normal animals and in 81% of spinal-nerve-ligated (SNL) animals. In normal animals, responses to noxious input were predominantly reduced, while in SNL animals, reductions in spinal cord activity induced by intra-RVM lignocaine further included responses to non-noxious stimuli. This suggests that in terms of activity at least, if not number, descending facilitations are the predominant RVM influence that impacts the spinal cord in normal animals. Moreover, the increase in the proportion of neurons showing a post-lignocaine reduction in dorsal horn activity in SNL rats suggests that the strength of these facilitatory influences increases after neuropathy. This predominant inhibitory spinal effect following the injection of lignocaine into the RVM may be due to blockade of facilitatory On cells.     

Characterization of nestin expression in the spinal cord of GFP transgenic mice after peripheral nerve injury

Many studies have shown that activation and increase in the number of astrocytes and microglia in the spinal cord participate in the initiation and maintenance of neuropathic pain, but little attention has been paid to the responses of neural progenitor cells to peripheral nerve injury. Nestin, a class VI intermediate filament protein, is expressed both in neuronal and glial progenitors as well as in their common precursors; and nestin-positive cells appear in the brain and spinal cord following various forms of damage to these regions. To clarify the responses of neural progenitor cells to nerve injury, we applied L5 spinal nerve transection (L5-SNT) to nestin-promoter GFP (pNestin-GFP) transgenic mice to narrow the target to them. While pNestin-GFP expression was strongly retained in the ependyma lining the central canal of the transgenic spinal cord even in adulthood, it was markedly reduced in the dorsal horn during postnatal development by day 7. Increases in pNestin-GFP expression and labeling by the proliferation marker 5-bromodeoxyuridine were broadly found in the dorsal horn of adult mice on day 3 after L5-SNT. On the other hand, the activation and increase in number of microglia and astrocytes are restricted to the superficial layer of the dorsal horn, the central terminal of injured primary afferent fibers. Purinergic P2X agonist α, β-MeATP increased [Ca²⁺]i in nestin-positive cells in the superficial layer ipsilateral to nerve injury and P2 receptor antagonists suramin and pyridoxalphosphate-6-azophenyl-2,4-disulphonic acid (PPADS) blocked the expression and elongation of pNestin-GFP fibers in the slice culture of the spinal cord. These results with pNestin-GFP transgenic mice demonstrate that nestin-positive cells proliferate in the dorsal horn in response to peripheral nerve injury and suggest that ATP may contribute to the expression of nestin and activation of neural progenitor cells after nerve injury.     

GDF10在神经病理性疼痛大鼠脊髓中的表达

目的:观察生长和分化因子10(GDF10)在神经病理性疼痛大鼠脊髓中的表达变化。方法:取雄性SD大鼠60只,通过结扎左侧L5脊神经制备神经病理性疼痛模型,于术前1 d,术后当天及术后1 d、3 d、10 d、21d检测大鼠左后爪50%缩爪阈值,并采用免疫荧光染色及Western blot检测大鼠L5脊髓后角GDF10的表达变化。结果:脊神经结扎大鼠在术后1 d缩爪阈值开始降低,自3 d起,与正常对照组相比差异有统计学意义(P0.05),到10 d阈值下降最明显,至21 d呈现持平状态。免疫荧光检测观察到伤侧L5脊髓组织中GDF10主要表达于脊髓背角神经元细胞的胞浆内。GDF10在术后持续降低,到10 d降低最为显著,与正常组相比差异具有统计学意义(P0.05),一直持续低水平表达至21 d。Western blot证实术后10 d脊髓中GDF10蛋白的表达较正常组大鼠明显降低(P0.05)。结论:大鼠脊神经结扎使脊髓背角中GDF10表达减少,其减少可能与大鼠脊神经损伤后对机械刺激引起的疼痛过敏有关联。     

全脑照射后对小鼠血脑屏障通透性和室管膜下区细胞增殖的影响

目的:探讨60Co-γ射线(Gy)全脑照射后对小鼠血脑屏障通透性和室管膜下区神经干细胞增殖的影响。方法:112只健康小鼠随机分成0 Gy组(对照组),5 Gy照射组(小剂量照射组),15 Gy照射组(中等剂量照射组)和30 Gy照射组(大剂量照射组),每组28只。各组随机取出7只分别于照射后1周和4周测定各组小鼠脑组织伊文思蓝的含量,7只观察室管膜下区的BrdU+细胞形态和数量。结果:(1)照射后1周,15 Gy组和30Gy组脑组织伊文思蓝含量明显升高(P<0.05),室管膜下区的BrdU+细胞数明显降低(P<0.05);(2)照射后4周,15 Gy剂量照射组脑组织伊文思蓝含量和室管膜下区的BrdU+细胞数均恢复到对照组水平(P>0.05),而30Gy剂量照射组脑组织伊文思蓝含量仍明显升高(P<0.05),BrdU+细胞数也未见恢复(P<0.05)。结论:全脑照射后血脑屏障破坏可能对室管膜下区的细胞增殖有进一步抑制作用。     

Effects of electro-acupuncture on NT-4 expression in spinal dorsal root ganglion and associated segments of the spinal dorsal horn in cats subjected to adjacent dorsal root ganglionectomy

It is well known that neuroplasticity occurs in the central nervous system in response to injury. Electro-acupuncture (EA) may also promote neuroplasticity. But little is known about the underlying molecular mechanisms for the beneficial effects of EA. This study investigated the effects of EA on neurotrophin-4 (NT-4) expression in L(6) spinal dorsal root ganglion (DRG) and associated segments of the spinal dorsal horn in cats subjected to unilateral removal of L(1)-L(5) and L(7)-S(2) DRG. NT-4 protein was normally present in the cytoplasm of the L(6) DRG neurons and L(3) and L(6) spinal dorsal horn neurons and glia. Adjacent ganglionectomy leads to a significant decrease in NT-4 expression in the L(6) DRG, but no change in the spinal dorsal horn. Following EA treatment a significant increase occurred in the L(6) DRG at 14 days post-operation (dpo) as well as the L(6) cord segment at 7 and 14 dpo. These findings pointed to a possible association between NT-4 expression and EA promoted spinal cord plasticity in adult cats subjected to partial ganglionectomy.     

Subtype-specific changes in 5-HT receptor-mediated modulation of C fibre-evoked spinal field potentials are triggered by peripheral nerve injury

Neurotransmitter serotonin (5-HT) released from descending pain modulation pathways to the dorsal horn is crucial to spinal nociception processing. This study sought to gain insight into the modulatory roles of specific serotonin receptor subtypes in experimentally induced neuropathic pain. In rats subjected to spinal nerve ligation (SNL) surgery, we recorded field potentials evoked in the spinal dorsal horn by C fibre-input, during spinal superfusion with subtype-selective drugs. In neuropathic rats, subtype 5-HT1A agonist 8-OH-DPAT (100 nM) was found to potently depress evoked field potentials, as opposed to 5-HT2A or 5-HT2B subtype agonists TCB-2 (100 nM) or BW 723C86 (1 μM), respectively, which consistently enhanced evoked potentials. All three failed to alter spinal field potentials in sham operated rats. CP 94253 (1 μM), WAY 161503 (1 mM) or SR 57227 (at 1 μM in SNL rats, and 100 μM in sham rats), selective agonists for 5-HT1B, 5-HT2C and 5-HT3 receptors, respectively, significantly depressed evoked field potentials in both animal groups. The 5-HT4 agonist RS 67333 (1 μM) was depressant only in sham operated animals. Only after SNL, spinal superfusion with 5-HT1A- or 5-HT1B receptor-antagonists (S)-WAY 100135 (100 μM) or SB 224289 (100 μM), respectively, disinhibited C fibre-evoked potentials, whereas 5-HT2A or 5-HT2B receptor-antagonists 4F 4PP (100 μM) or SB 204741 (100 μM) depressed evoked potentials, suggesting tonic activity of all four subtypes as a consequence of experimental nerve injury. The present findings reveal profound subtype-specific changes in the functional modulatory activities of spinal serotonin receptors following peripheral nerve injury. In particular, spinal hyperexcitation promoted by receptors 5-HT2A and 5-HT2B is suggested as a novel pathogenic pathway contributing to neuropathic pain.     

电针对慢性内脏痛大鼠脊髓背角降钙素基因相关肽的影响

目的:检测电针对慢性内脏痛大鼠脊髓背角内降钙素基因相关肽(calcitonin gene-related peptide,CGRP)表达的影响。方法:SD大鼠随机分成正常对照组,慢性内脏痛模型组和模型加电针组,每组6只。慢性内脏痛模型采用新生幼鼠结直肠刺激方法制备;模型加电针组选取双侧"足三里"和"上巨虚",疏密波,强度1mA,持续30min,隔日一次,持续四次。记录结直肠扩张刺激下腹外斜肌放电幅值;免疫组织化学法检测各组大鼠胸腰段、腰骶段脊髓背角内CGRP的表达变化。结果:电针能够显著降低内脏痛大鼠结直肠扩张刺激诱导的腹外斜肌放电幅值(P0.05);免疫组织化学染色法显示:CGRP样免疫阳性物质的表达在模型组大鼠的胸腰段、腰骶段脊髓背角内均显著升高(P0.01),而模型加电针组的胸腰段、腰骶段脊髓背角内CGRP的表达与模型组相比有显著降低(P0.01)。结论:电针降低慢性内脏痛敏反应的镇痛机制与减少脊髓背角内CGRP样免疫阳性物质的表达有关。