背根神经节内交感神经纤维芽生与神经病理性痛

周围神经损伤诱发神经病理性痛,引起自发性疼痛、痛觉过敏和痛觉异常。目前关于神经病理性痛的发病机制尚不明确,但在许多神经损伤动物模型中观察到背根神经节（DRG）内的交感神经纤维芽生、围绕在节细胞周围形成篮状结构。以往的研究结果提示这些篮状结构（感觉-交感耦联）参与神经病理性痛的发生。现拟就DRG中交感神经纤维芽生与神经病理性痛及其敏化之间的关系予以综述。     

加巴喷丁对脊神经结扎大鼠背根神经节交感神经芽生的影响

目的:观察加巴喷丁干预后疼痛大鼠痛阈变化及背根神经节(DRGs)中交感神经芽生的改变。方法:将SD雄性大鼠随机分为正常对照组、模型组和加巴喷丁组,于术前及术后5 d每天检测大鼠痛阈变化;术后5 d取各组大鼠手术侧腰5和腰4及对侧腰5 DRG,观察DRGs中交感纤维数量及篮状结构的变化。结果:加巴喷丁可以显著抑制脊神经结扎引起的痛觉过敏;模型组(手术侧腰5及腰4)表现为交感神经节后纤维的异常增生,加巴喷丁干预后,手术侧腰5和腰4 DRGs TH-IR纤维及篮状结构的数量明显低于模型组。结论:加巴喷丁能提高疼痛大鼠痛阈,其机制可能是通过降低脊髓DRG中交感神经的芽生而产生镇痛作用。     

背根神经节电压门控钠离子通道与神经性疼痛的研究进展

神经性疼痛属于慢性疼痛,以痛觉过敏为特征,表现为自发性持续或间歇性烧灼痛,同时对疼痛刺激的反应性增高.由于发病机制尚不清楚,一直以来是困扰医学界的难题.背根神经节(DRG)作为痛觉传入的第一级神经元在痛觉的外周机制中起着极为重要的作用,对背根神经节上离子通道的认识,对于阐明神经性疼痛的机制有重要意义.本文结合近年来对背根节上电压门控钠通道的研究进展,对其与神经性疼痛的关系加以综述,望有助于同行了解相关领域的最新研究动态.     

血竭及其成分龙血素B影响背根神经节细胞钠离子通道的计算机模拟研究

应用膜片钳技术，观察中药血竭及其成分龙血素B对背根神经节细胞河豚毒素敏感型钠通道电流的影响。以Hodgkin—Huxley模型拟合实验资料，进行参数估计，并对药物作用前后的细胞膜动作电位进行计算机模拟。结果表明，m^3h模型能较好地拟合河豚毒素敏感型钠通道电导；药物作用于钠通道后，半激活电压均向去极化方向偏移；药物作用后的细胞产生动作电位的阈强度提高。说明血竭及其成分龙血素B并非类似河豚毒素完全抑制河豚毒素敏感型钠通道电流。血竭可能通过其成分龙血素B影响通道的激活过程阻滞动作电位的产生，干预痛觉信息的中枢传人而产生镇痛效应。     

山莨菪碱对兔缺血再灌注心室肌细胞钠离子通道电流的影响

目的:建立兔心肌缺血再灌注动物模型,研究山莨菪碱对兔在体缺血再灌注后心室肌细胞钠离子通道电流(INa)的影响,探讨山莨菪碱抗再灌注心律失常的细胞学离子机制。方法:45只新西兰大耳白兔随机分为3组:缺血再灌注动物模型组(I/R组,结扎冠脉左前降支30min后再开放120min);山莨菪碱治疗组(Ani+I/R组,手术前1min给予动物耳缘静脉注射山莨菪碱5mg/kg);假手术对照组(只开胸不结扎血管)。观察缺血再灌注期间室性心律失常(室早、室速和室颤)的发生率及持续时间。采用酶解的方法分离缺血部位心室肌外膜单个心室肌细胞,应用全细胞膜片钳技术记录INa。结果:(1)心律失常发生率:与I/R组比较,Ani+I/R组兔室速、室颤发生率及持续时间明显下降,其心律失常的评分明显低于I/R组(2.6±0.7vs3.6±0.8,P0.05)。对照组、I/R组和Ani+I/R组INa电流密度峰值(-30mV)分别为-42.78±5.48(n=16)、-22.46±5.32(n=12)和-38.89±5.24pA/pF(n=13),I/R组明显低于对照组(P0.01),Ani+I/R组明显高于I/R组(P0.01)。结论:山莨菪碱可降低心肌缺血再灌注期间心律失常的发生率。心肌缺血再灌注后,INa明显下降,山莨菪碱预处理可使下降的INa上调,逆转电重构,可能为山莨菪碱降低再灌注心律失常发生率的细胞学离子机制。     

皮质内胆碱能纤维损伤后的再生和侧支生芽

大鼠顶皮质切一宽2mm的冠状切口,用染AChE纤维的组织化学方法结合网格计算分析切口嘴、尾侧区的胆碱能纤维的再生和侧支生芽状况。主要结果是:1.损伤后切口嘴侧胆硷能纤维先轻度减少,然后迅速增加超过正常20％以上,并沿切口嘴侧缘形成一片密集的纤维丛;2.4周以后发现少量纤维直接穿过切口进入尾侧区;3.损伤后切口尾侧胆硷能纤维明显减少,第4周后纤维数量逐渐增加,6周时恢复到正常的87％,提示成年哺乳类皮质胆硷能纤维有很强的再生和侧支生芽能力。     

大鼠DRG内ClC-3敲减导致的TNF-α/IL-10失衡对电压门控性钠通道表达和机械痛敏的影响

目的:研究敲减大鼠背根神经节(DRG)内ClC-3氯通道/反向转运体对神经元电压门控性钠通道表达和大鼠机械痛敏的影响及机制。方法:成年SD大鼠鞘内注射ClC-3 shRNA腺相关病毒(AAV-ClC-3 shRNA)以敲减DRG内ClC-3的表达,RT-qPCR、免疫荧光染色和Western blot从mRNA和蛋白水平检测ClC-3、细胞因子和电压门控性钠通道表达的变化,用up-down方法检测机械痛敏。结果:鞘内注射AAV-ClC-3 shRNA后DRG组织ClC-3的表达下调,大鼠出现机械触诱发痛。敲减DRG组织ClC-3的表达可致电压门控性钠通道Nav1. 3、Nav1. 7、Nav1. 8和Nav1. 9的表达增加。敲减DRG组织ClC-3的表达可提高肿瘤坏死因子α(TNF-α)水平,降低白细胞介素10(IL-10)水平。结论:大鼠DRG内ClC-3下调导致TNF-α/IL-10失衡,进而增加电压门控性钠通道Nav1. 3、Nav1. 7、Nav1. 8和Nav1. 9表达,增强神经组织兴奋性,最终导致机械痛敏。     

IL-4和IL-6对慢性阻塞性肺疾病患者气道上皮细胞阿米洛利敏感的Na+通道电流的影响

目的：研究慢性阻塞性肺疾病（COPD）患者原代培养的气道上皮细胞中阿米洛利敏感的Na+通道电流（Iamil）及IL-4、IL-6对其影响。 方法： 体外分离培养气道上皮细胞，经过终浓度均为10 μg/L的IL-4、IL-6处理，用全细胞膜片钳技术记录原代培养的气道上皮细胞中Iamil。 结果： 正常不吸烟对照组、正常吸烟对照组及COPD组Iamil值无显著差异。IL-4处理可以下调正常不吸烟对照组、正常吸烟对照组及COPD组的Iamil，下调幅度分别为59.7%、54.7%及30.0%；IL-6处理可以下调正常不吸烟对照组、正常吸烟对照组的Iamil，下调幅度分别为44.8%及34.9%，但是IL-6处理不能下调COPD组Iamil值；且IL-4、IL-6处理后的Iamil电流形状未见明显改变。 结论： IL-4及IL-6处理可以下调体外培养的气道上皮细胞的Iamil，提示在COPD患者中升高的IL-4及IL-6水平将有助于气道高分泌状态的形成，同时由于COPD患者中自身IL-4及IL-6的水平升高，导致培养的COPD患者气道上皮细胞对IL-4及IL-6处理的反应相对较弱。     

Increased projection of ascending dorsal root fibers to vestibular nuclei after hemilabyrinthectomy in the frog

Summary The projections from brachial, ascending dorsal root fibers were studied autoradiographically in controls and chronically (four months) hemilabyrinthectomized frogs. Comparison showed that projections into the partially denervated vestibular nuclear complex of chronically hemilabyrinthectomized animals were far more dense than in control animals. In the cerebellar granular layer, no obvious difference in the extent of dorsal root projections was observed between both groups of animals. Cerebellar areas such as the auricular lobe and the dorsal rim, which normally receive many terminals from vestibular but not from dorsal root afferents, were not invaded by dorsal root fibers in chronically hemilabyrinthectomized frogs.     

Purinergic activation of dorsal root ganglion neurones in vivo

Functional relevance of non-synaptic purinergic receptors on dorsal root ganglion cells was tested in vivo by the influence of ATP using 2P-LSM and Ca imaging. Within a few seconds after local application of ATP, neurones in dorsal root ganglion were activated indicated by an increase of their calcium signal. The signal reached its maximum within a few seconds and declined to control values after about 30 s. Purinergic action seems to include non-synaptic cell-to-cell communication within dorsal root ganglia.     

The existence of hypoglossal root ganglion cells in adult humans: potential clinical implications

INTRODUCTION: Ganglion cells of the hypoglossal nerve (HN) have been confirmed in certain animals but have been thought not to be present in man. To investigate for the presence of these structures in adult humans and if present, to verify their functionality, the present study was performed. MATERIALS AND METHODS: We harvested adult cadaveric HN and observed for ganglion cells. Histological and immunohistochemical analyses were performed on all specimens. RESULTS: Ganglion cells were found in 33% of specimens. Using immunohistochemistry, we found that these ganglia were sympathetic in nature. Based on our findings, ganglion cells do exist in the human HN although they are located sporadically and are found inconstantly. CONCLUSIONS: Such information may be valuable in elucidating other functions of the HN and may aid in the histological diagnosis of this nerve. Additionally, pathology involving HN such as paragangliomas, are supported by our findings of the presence of autonomic ganglion cells in some HN specimens.     

Immunohistochemical analysis of acid-sensing ion channel 2 expression in rat dorsal root ganglion and effects of axotomy

Several studies have suggested that acid-sensing ion channel 2 (ASIC2) plays a role in mechanoperception and acid sensing in the peripheral nervous system. We examined the expression and distribution of ASIC2 in the rat dorsal root ganglion, the co-localization of ASIC2 with tropomyosin-related kinase (trk) receptors, and the effects of axotomy on ASIC2 expression. ASIC2 immunoreactivity was observed in both neurons and satellite cells. ASIC2-positive neurons accounted for 16.5 +/- 2.4% of the total neurons in normal dorsal root ganglion. Most ASIC2-positive neurons were medium-to-large neurons and were labeled with neurofilament 200 kD (NF200). Within these neurons, ASIC2 was not evenly distributed throughout the cytoplasm, but rather was accumulated prominently in the cytoplasm adjacent to the axon hillock and axonal process. We next examined the co-localization of ASIC2 with trk receptors. trkA was expressed in few ASIC2-positive neurons, and trkB and trkC were observed in 85.2% and 53.4% of ASIC2-positive neurons, respectively, while only 6.9% of ASIC2-positive neurons were co-localized with trkC alone. Peripheral axotomy markedly reduced ASIC2 expression in the axotomized dorsal root ganglion neurons. On the other hand, intense ASIC2 staining was observed in satellite cells. These results show that ASIC2 is expressed in the distinct neurochemical population of sensory neurons as well as satellite cells, and that peripheral axotomy induced marked reductions in ASIC2 in neurons.     

Inhibitory action of protein kinase Cbeta inhibitor on tetrodotoxin-resistant Na+ current in small dorsal root ganglion neurons in diabetic rats

Experimental evidence has been presented to suggest that protein kinase Cbeta isoform-selective inhibitor LY333531 is effective at alleviating diabetic hyperalgesia. In the present study, we isolated small (< or =25 microm in soma diameter) dorsal root ganglion (DRG) neurons from control and streptozocin (STZ)-induced diabetic rats, and examined the acute action of LY333531 (1-1000 nM) on the tetrodotoxin-resistant Na(+) current (TTX-R I(Na)), which plays an essential role in transmitting nociceptive impulses, using the whole-cell patch-clamp method. TTX-R I(Na) in diabetic DRG neurons was enhanced in amplitude (71.5+/-3.6pA/pF, n=10 versus 41.2+/-3.3pA/pF, n=8) and was activated at more negative potentials (V(1/2), -15.1+/-1.3 mV versus -9.6+/-1.4 mV), compared with that in control neurons. Bath application of LY333531 acutely inhibited TTX-R I(Na) in both control and diabetic DRG neurons, and the degree of inhibition by the drug at concentrations of 1, 10 and 100 nM was significantly greater in diabetic DRG neurons than in control DRG neurons. Thus, TTX-R I(Na), which is upregulated in the diabetic state, is likely to be more potently inhibited by submicromolar concentrations of LY333531. These results suggest that an acute inhibition of TTX-R I(Na) by LY333531 attenuates the exaggerated excitability of DRG neurons in the diabetic state, which appears to be related at least partly to anti-hyperalgesic actions of the drug in diabetic neuropathy.     

Isolation of specific peptides that home to dorsal root ganglion neurons in mice

We isolated peptides that home to mouse dorsal root ganglion (DRG) from a phage library expressing random 7-mer peptides fused to a minor coat protein (pIII) of the M13 phage. An in vitro biopanning procedure yielded 113 phage plaques after five cycles of enrichment by incubation with isolated DRG neurons and two cycles of subtraction by exposure to irrelevant cell lines. Analyses of the sequences of this collection identified three peptide clones that occurred repeatedly during the biopanning procedure. Phage-antibody staining revealed that the three peptides bound to DRG neurons of different sizes. To determine if the peptides would recognize neuronal cells in vivo, we injected individual GST-peptide-fusion proteins into the subarachnoid space of mice and observed the appearance of immunoreactive GST in the cytosol of DRG neurons with a similar size distribution as that observed in vitro, indicating that the GST-peptide-fusion proteins were recognized and taken up by different DRG neurons in vivo. The identification of homing peptide sequences provides a powerful tool for future studies on DRG neuronal function in vitro and in vivo, and opens up the possibility of neuron-specific drug and gene delivery in the treatment of diseases affecting DRG neurons.     

Transient early expression of TNF-alpha in sciatic nerve and dorsal root ganglia in a mouse model of painful peripheral neuropathy

The proinflammatory cytokine tumor necrosis factor-alpha (TNF) is an important mediator in neuropathic pain. We investigated the temporal pattern of TNF mRNA expression in the sciatic nerve, in dorsal root ganglia (DRG) and spinal cord in the mouse chronic constriction injury model of neuropathy with quantitative real-time polymerase chain reaction. Neuropathic pain-like behaviour was monitored by evaluating thermal hyperalgesia and mechanical allodynia. Pain-related behaviour and TNF expression were evaluated 6 h, 1, 3, 7 and 14 days after injury. Naive animals and sham-operated mice were used as controls. We found an early upregulation of sciatic nerve TNF mRNA levels in chronic constriction injury (CCI) and sham-operated animals 6 h after surgery: 1 day later TNF overexpression was present in CCI mice only and disappeared 3 days after injury. The mRNA cytokine levels were elevated in DRG 1 and 3 days after surgery in CCI animals only, while the cytokine was not modulated in the spinal cord. A significant hyperalgesia was present in CCI and sham-operated mice at 6 h and 1 day, while at later time point only CCI mice presented lower thresholds. Mechanical allodynia was already present only in CCI animals 6 h from surgery and remained constant up to the 14 th day. The results indicate that a transient early TNF upregulation takes place in peripheral nervous system after CCI that can activate a cascade of proinflammatory/pronociceptive mediators.     

Progress in dorsal root ganglion neurosteroidogenic activity: Basic evidence and pathophysiological correlation

Dorsal root ganglia (DRG) which contain glial cells and somas of primary sensory neurons are pivotal for neural transmission between the peripheral and central nervous systems. It is well established that neuropeptides such as substance P and calcitonin gene-related peptide located in DRG neurons control sensory and pain mechanisms. However, contrary to the brain and spinal cord which are extensively investigated, DRG received little attention. Therefore, the current knowledge on DRG may be far to represent their complete neurochemical potential. For instance, until 1997, nothing was known on DRG neurosteroidogenic ability but recently, several investigations have shown that DRG contain various key enzymes synthesizing neuroactive neurosteroids. To provide new advances into DRG neurochemistry, we reviewed and highlighted herein basic and functional evidence showing that neurosteroids are produced in DRG through a neuron-glia crosstalk mechanism. Indeed, key enzymes producing neurosteroids including pregnenolone, progesterone, dihydroprogesterone and estradiol are differentially expressed in DRG cell types. Cytochrome P450side-chain-cleavage is located in DRG neurons and satellite glial cells, 3β-hydroxysteroid dehydrogenase is expressed in Schwann cells and neurons, 5α-reductase is localized in satellite glial and Schwann cells (not in neurons) while aromatase is present in neurons but not in glia. Recent studies also revealed that DRG neurosteroidogenesis is a physiologically relevant process selectively regulated under pathological conditions. Acting through paracrine and autocrine mechanisms, endogenous neurosteroids modulate DRG sensory functions and protect DRG neurons against death. The paper suggests that DRG neurosteroidogenic components may be targeted for the development of therapies against peripheral nerve injury-induced afferent noxious stimulations.     

Changes in trkA expression in the dorsal root ganglion after peripheral nerve injury

Most of the biological effects of nerve growth factor (NGF) are mediated by TrkA, the high affinity receptor for NGF. Previous studies have shown that NGF levels in the dorsal root ganglia (DRG) fluctuate following a peripheral nerve injury. The present study examined changes of TrkA immunoreactivity and trkA mRNA expression in the DRG after segmental nerve ligation. In the normal L5 DRG of the rat, there were, on average, 4700 TrkA-immunoreactive (TrkA-IR) neurons, representing 42% of the total neuronal population. Following L5 spinal nerve ligation, the number of TrkA-IR neurons in the L5 DRG slowly declined, reducing by 25% at 1 week and 35% at 3 weeks postoperation (PO). In contrast, trkA mRNA in these ganglia showed a significant decrease from 3 days to 3 weeks PO and was followed by a full recovery at 2 months PO. The early decrease of trkA mRNA is likely due to deprivation of target-derived NGF, which is caused by nerve ligation, and the recovery might be because substitute sources of NGF become available. Despite the decline in trkA mRNA in the ganglion, 3000 injured DRG neurons sustain TrkA immunoreactivity, suggesting that exogenous NGF can still influence these TrkA expressing neurons, even though they are isolated from the periphery. Accordingly, the effects of endogenous NGF should be as well manifested by local administration of NGF to the ganglion as to the stump of the damaged nerve. Received: 20 October 1998 / Accepted: 10 February 1999