TRPV1受体基因敲除雌性小鼠背根神经节P2X3受体表达升高

本文旨在考察瞬时受体电位香草酸亚型1(transient receptor potential vanilloid 1,TRPV1受体)基因敲除后小鼠慢性炎症条件下机械痛阈的改变。通过足底注射给予完全弗氏佐剂(20μL)介导雌性小鼠慢性炎症痛的形成,利用弗莱毛测痛法测量TRPV1受体基因敲除型及野生型雌性小鼠在给药前1天和给药后8天内的机械痛阈。给药后第9天处死小鼠,利用蛋白质免疫印迹技术研究两组小鼠脊髓背根神经节(dorsal root ganglion,DRG)和脊髓背角中c-Fos蛋白和P2X3受体表达的差别。结果显示,与野生型小鼠相比,TRPV1受体基因敲除型小鼠基础机械痛阈明显增高(P0.05);足底注射CFA后第3天起,TRPV1受体基因敲除型小鼠机械痛阈高于野生型小鼠(P0.05);蛋白质免疫印迹结果表明TRPV1受体基因敲除型小鼠DRG和脊髓背角中c-Fos蛋白的表达明显低于野生型小鼠(P0.01,P0.05),TRPV1受体基因敲除型小鼠DRG中P2X3受体的表达明显高于野生型小鼠(P0.05)。以上结果证明TRPV1受体可能通过调节DRG和背角中的c-Fos蛋白的表达以及影响P2X3受体在DRG中的表达从而影响外周机械痛阈。     

大鼠面部慢性炎症痛导致三叉神经节表达P2X3神经元表型的转变

目的研究大鼠面部慢性炎症痛与三叉神经节内表达P2X3受体亚型神经元细胞大小和表型变化之间的关系。方法参照Neumann(1996)报道的研究方法,采用大鼠面部皮下注射松节油建立慢性炎症痛模型,用热测痛的方法测定面部皮肤的痛阈值,每天一次,连续测15d。用免疫组织化学技术观察大鼠面部慢性炎症后第5d三叉神经节内感觉神经元P2X3受体的表达。采用体视学的方法测量表达P2X3神经节细胞大小及表型的变化。结果炎症侧大鼠面部痛阈值与对照组相比明显降低,在第5d达到最低值,以后逐渐恢复,第13d开始痛阈恢复正常水平。炎症侧三叉神经节内表达P2X3神经元的平均细胞表面积(721±12μm2)与对照组(616±8μm2)相比明显增大(P<0·01)。进一步观察发现表达P2X3小细胞群(<950μm2)的表面积由炎症前的537±13μm2增加到炎症后的582±15μm2(P<0·05)而且小细胞占总细胞的数量比例由炎症前的42·2±3·2%增加到炎症后的51·8±3·5%(P<0·05);而表达P2X3受体的大细胞(>950μm2)的数量比例由炎症前的6·5±1·9%增加到炎症后的12·8±2·2%(P<0·05)。结论面部慢性炎症痛时,其三叉神经节内表达P2X3受体神经元的表型可发生改变,这可能与面部痛觉过敏和触诱发痛的形成有密切关系。     

神经病理痛大鼠DRG神经元GABAA受体激活电流的变化

目的：观察坐骨神经慢性压榨损伤（CCI）致神经病理痛后,大鼠背根节神经元GABAA受体（γ-氨基丁酸A受体）激活电流的变化。方法：运用全细胞膜片钳技术记录CCI模型手术侧、手术对侧及假手术组大鼠背根神经节细胞GABAx受体激活电流,比较坐骨神经慢性压榨损伤后GABAA受体激活电流的变化。结果：①CCI模型组大鼠手术侧DRG神经元在不同浓度（0．1-1000μmol／L）GABAA受体激活电流幅值均显著小于假手术组。②CCI模型组大鼠手术对侧DRG神经元在不同浓度（0．01-1000μmol／L）GABAA受体激活电流幅值均显著大于手术同侧及假手术组。结论：在坐骨神经慢性压榨损伤的过程中,不仅损伤侧的DRG神经元GABAA受体激活电流显著减小,这种损伤同时还引起了手术对侧的DRG神经元GABA激活电流代偿性的增强,GABAA受体功能的改变导致的突触前抑制作用的减弱可能是神经病理痛产生的根本原因之一。     

阻断炎症部位5-HT2A受体对大鼠完全弗氏佐剂诱发炎性痛和脊髓背角神经肽Y表达的作用

炎症时组织释放5-羟色胺(5-hydroxytryptamine,5-HT),对炎性痛觉过敏的产生起重要作用。但炎症组织5-HT2A受体在其中的意义尚不明确。本文旨在研究外周组织5-HT2A受体在慢性炎性痛中的作用。大鼠后足底注射完全弗氏佐剂(complete Freund’s adjuvant,CFA),在局部炎性部位给予选择性5-HT2A受体阻断剂酮色林,用行为学检测后足底对热和机械刺激的撤足反射,用免疫组织化学方法检查脊髓背角和背根神经节(dorsal root ganglion,DRG)中神经肽Y(neuropeptide Y,NPY)表达变化。结果显示,炎症局部给予酮色林(20、40、80μg)能剂量依赖性地抑制CFA诱发的热痛觉过敏;每日给予80μg酮色林,在第三天即完全翻转CFA引起的热痛觉过敏,以及部分地减轻触觉超敏。CFA诱发脊髓背角I~II层NPY表达增加,炎症组织局部注射酮色林能抑制脊髓背角NPY的表达增加,但不改变DRG中NPY的表达。这些结果表明:外周炎症组织5-HT2A受体激活参与慢性痛觉过敏的发生;阻断炎症部位5-HT2A受体能缓解疼痛,矫正与病理疼痛密切关联的脊髓背角细胞异常改变。因此,外周5-HT2A受体,有望成为治疗慢性炎性痛觉敏感性增高、不产生中枢神经系统副作用的药物靶点。     

福尔马林致痛对大鼠脊髓和背根神经节的P2X3的影响

目的:探索福尔马林致痛后大鼠脊髓和背根神经节(dorsal root ganglion,DRG)的P2X3表达变化。方法:选取健康成年正常SD大鼠25只,分正常对照组和实验组;实验组为右侧足底皮下给予0.1ml 5%福尔马林,分别观察15min、30min、1h、3h后处死,采用免疫组织化学方法及图像分析技术检测脊髓腰段及L4～6背根节P2X3的表达情况。结果:与正常对照组相比,实验15min、30min、1h组脊髓后角Ⅱ层P2X3表达未见变化,实验3h组可见P2X3表达升高,但未见明显差异;实验15min、30min组DRG神经元P2X3表达未见变化,1h组开始表达上调,3h组表达明显升高,与各组相比有显著性差异。结论:福尔马林致痛能引起脊髓和背根神经节P2X3的表达上调,可能是其产生伤害性作用的机制之一。     

大鼠初级感觉神经元P2X3受体的表达及其与SP的关系

目的研究在大鼠初级感觉神经元细胞上P2X3受体的表达情况及其与P物质的关系。方法取SD大鼠背根神经节(DRG)和三叉神经节(TG)固定后切片;用抗P2X3受体抗体和抗SP抗体进行免疫组织化学反应,并通过两种不同的显色方法同时进行P2X3受体和SP的双标。结果P2X3免疫反应阳性细胞主要集中在小细胞和中等细胞(其中在TG,P2X3-ir阳性神经元约占整个细胞的24.8%;在DRG约31.7%的神经元是P2X3-ir阳性),并且在DRG和TG细胞上均存在有P2X3受体和SP共存(TG上的双标细胞占P2X3-ir阳性细胞总数的36.26%,DRG上占46.81%)。结论由于ATP门控阳离子通道受体P2X3本身就与伤害性感受的初级传入有关,而它与SP的共存可提示当组织中的ATP释放时可以通过P2X3受体作用于含SP的伤害性感觉神经末梢上,促使SP释放引起痛觉过敏。     

肝细胞生长因子在正常大鼠腰段脊髓和背根神经节的表达

目的:观察肝细胞生长因子(hepatocyte growth factor,HGF)在大鼠脊髓和背根神经节(dorsal root ganglion,DRG)的表达。方法:取健康成年6只SD大鼠运用免疫组织化学染色技术检测HGF在腰段脊髓、背根神经节内的表达和分布。结果:在L4-6段脊髓,HGF免疫阳性产物可见于各板层神经元,尤以脊髓前角运动神经元明显;在DRG中,HGF免疫阳性物质可见于以大、中型为主的神经元的胞浆及突起中。结论:脊髓和背根神经节内的HGF通过与受体c-Met结合可能在神经再生及突触可塑性方面起一定作用。     

PKC激动剂佛波醇酯诱导大鼠伤害性感受并促进脊髓NO产生

目的:观察PKC激动剂PMA诱导大鼠伤害性感受作用及对脊髓NOS表达和NO生成的影响.方法:采用行为学方法观察大鼠痛反应;热甩尾法测定大鼠痛阈变化;采用NADPH-d组织化学法和硝酸还原酶法分别测定大鼠脊髓内NOS表达和NO含量.结果:鞘内注射PMA后,大鼠出现伤害性感受反应及痛阈降低,脊髓后角浅层和中央管周围灰质内NOS阳性细胞数目、阳性细胞胞体及突起的染色深度明显增加,脊髓NO含量亦明显增加.给予PKC选择性抑制剂CH预处理可阻断鞘内注射PMA诱导的上述改变.结论:脊髓神经元内PKC激活可诱导大鼠产生伤害性感受及热痛觉过敏,并可促进NO产生,其对NO产生的促进作用可能是其诱导痛觉过敏产生的机制之一.     

电针对炎性痛大鼠背根神经节卫星胶质细胞活化和P2X7受体表达的干预

目的观察电针对慢性炎性痛大鼠患侧足跖机械痛阈(paw withdrawal thresholds,PWTs)以及背根神经节(dorsal root ganglia,DRG)内卫星胶质细胞及其P2X7受体活化的影响,探讨电针抗大鼠炎性痛的外周机制。方法第一部分:将大鼠完全随机分为空白组(Con group,n=12)、炎性痛组(CFA group,n=12)、炎性痛+电针组(CFA+EA group,n=12)、炎性痛+假电针组(CFA+s EA group,n=12)。炎性痛大鼠于右后足掌侧正中皮下注射完全弗氏佐剂(complete freud’s adjuvant,CFA)每只0.1 m L构建模型;电针处理取穴"足三里"、"昆仑",电针参数为疏密波,频率2/100 Hz,强度0.5-1-1.5 m A(每个强度治疗10 min),每日1次,连续7 d。检测造模前和造模后1、3、7、8、10、12、14 d各组大鼠机械痛阈,采用免疫印迹法检测造模后14 d各组大鼠患侧DRG中神经胶质酸性蛋白(glial fibrillary acidic protein,GFAP)及P2X7受体活化情况。第二部分:将大鼠随机分为炎性痛+DMSO组(CFA+DMSO group,n=8)、炎性痛+P2X7R抑制剂A740003组(CFA+A740003 group,n=10)、炎性痛+电针+生理盐水组(CFA+EA+NS group,n=8)、炎性痛+电针+P2X7R激动剂Bz ATP组(CFA+EA+Bz ATP group,n=12),分别鞘内注射相应药物。分别于手术前、造模前、造模后和给药后各时点检测大鼠PWTs变化。结果 (1) CFA致炎性模型大鼠痛阈显著下降(P 0.01),电针治疗后其机械痛阈显著升高(P 0.01)。CFA足底注射14 d后,大鼠患侧L4-6 DRG中GFAP、P2X7蛋白表达显著增多(P 0.05);电针显著抑制大鼠患侧L4-6 DRG中GFAP、P2X7蛋白表达(P 0.05),而CFA+s EA组却无明显变化(P 0.05)。(2)与CFA+DMSO组比较,鞘内注射P2X7抑制剂A740003显著提高CFA大鼠机械痛阈(P 0.01); CFA+EA+Bz ATP组大鼠PWTs明显低于CFA+EA+NS组(P 0.01)。结论抑制大鼠背根神经节卫星胶质细胞活化和P2X7受体表达参与电针抗慢性炎性痛,可能是电针镇痛外周机制之一。     

瞬时外向钾电流的降低介导了慢性压迫背根神经节细胞兴奋性的升高

慢性压迫大鼠背根神经节（chronic compression of the dorsal root,ganglion,CCD）后,背根神经节细胞兴奋性升高,但引起神经元兴奋性改变的离子通道机制还需进一步探索。本实验采用胞内记录以及全细胞膜片钳记录方法,研究急性分离的大鼠背根神经节细胞兴奋性改变与瞬时外向钾电流（A-type potassium current,ⅠA）的关系。结果表明,CCD术后背根神经节细胞兴奋性升高,在急性分离的体外细胞中仍继续存在,表现为对辣椒素敏感的背根神经节细胞产生动作电位的最小电流刺激强度,即阈电流（current threshold）及阈电位（voltage threshold）降低;给予正常对照组神经元（未压迫损伤）瞬时外向钾通道阻断剂4-氨基吡啶,出现了类似CCD术后兴奋性升高的改变。进一步用两步电压钳方法分离ⅠA,研究CCD术后神经元ⅠA的变化,结果表明,CCD组神经元的ⅠA比对照组神经元ⅠA降低,并且与其阈电位的改变一致。以上结果提示,背根神经节压迫受损后,神经节细胞ⅠA降低可能参与介导了神经节细胞兴奋性的升高。     

Inhibitory effect of estrogen receptor beta on P2X3 receptors during inflammation in rats

Estrogen receptor beta (ERβ) has been shown to play a therapeutic role in inflammatory bowel disease (IBD). However, the mechanism underlying how ERβ exerts therapeutic effects and its relationship with P2X3 receptors (P2X3R) in rats with inflammation is not known. In our study, animal behavior tests, visceromotor reflex recording, and Western blotting were used to determine whether the therapeutic effect of ERβ in rats with inflammation was related with P2X3R. In complete Freund adjuvant (CFA)-induced chronic inflammation in rats, paw withdrawal threshold was significantly decreased which were then reversed by systemic injection of ERβ agonists, DPN or ERB-041. In 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats, weight loss, higher DAI scores, increased visceromotor responses, and inflammatory responses were reversed by application of DPN or ERB-041. The higher expressions of P2X3R in dorsal root ganglia (DRG) of CFA-treated rats and those in rectocolon and DRG of TNBS-treated rats were all decreased by injection of DPN or ERB-041. DPN application also inhibited P2X3R-evoked inward currents in DRG neurons from TNBS rats. Mechanical hyperalgesia and increased P2X3 expression in ovariectomized (OVX) CFA-treated rats were reversed by estrogen replacements. Furthermore, the expressions of extracellular signal-regulated kinase (ERK) in DRG and spinal cord dorsal horn (SCDH) and c-fos in SCDH were significantly decreased after estrogen replacement compared with those of OVX rats. The ERK antagonist U0126 significantly reversed mechanical hyperalgesia in the OVX rats. These results suggest that estrogen may play an important therapeutic role in inflammation through down-regulation of P2X3R in peripheral tissues and the nervous system, probably via ERβ, suggesting a novel therapeutic strategy for clinical treatment of inflammation.     

Monoarticular antigen-induced arthritis leads to pronounced bilateral upregulation of the expression of neurokinin 1 and bradykinin 2 receptors in dorsal root ganglion neurons of rats

This study describes the upregulation of neurokinin 1 and bradykinin 2 receptors in dorsal root ganglion (DRG) neurons in the course of antigen-induced arthritis (AIA) in the rat knee. In the acute phase of AIA, which was characterized by pronounced hyperalgesia, there was a substantial bilateral increase in the proportion of lumbar DRG neurons that express neurokinin 1 receptors (activated by substance P) and bradykinin 2 receptors. In the chronic phase the upregulation of bradykinin 2 receptors persisted on the side of inflammation. The increase in the receptor expression is relevant for the generation of acute and chronic inflammatory pain.     

Acid-sensing ion channels 3: a potential therapeutic target for pain treatment in arthritis

Acid-sensing ion channels 3 (ASIC3) is the most sensitive to such a pH change, predominantly distributed in the sensory peripheral nervous system, and strongly correlated with pain. Recently, there is increasing evidence that ASIC3 may contribute to the pathogenesis of chronic inflammatory pain diseases due to it is predominantly expressed in dorsal root ganglia (DRG) neurons making it a good candidate for a pain sensor. Elevated expression of ASIC3 was found in DRG of rodents with inflamed hind paws. In addition, it has been shown that ASIC3 gene knock-out mice (ASIC3−/−) exhibited no enhanced hyperalgesia in inflamed joint. All theses findings suggest that ASIC3 have important biological effects in inflammation that might be a promising therapeutic target for arthritis pain. In this review, we will briefly discuss the biological features of ASIC3 and summarize recent advances on the role of ASIC3 in the pathogenesis and treatment of arthritis pain.     

Protein kinase C-α upregulates sodium channel Nav1.9 in nociceptive dorsal root ganglion neurons in an inflammatory arthritis pain model of rat

Previous studies have found that increased expression of Nav1.9 and protein kinase C (PKC) contributes to pain hypersensitivity in a couple of inflammatory pain models. Here we want to observe if PKC can regulate the expression of Nav1.9 in dorsal root ganglion (DRG) in rheumatoid arthritis (RA) pain model. A chronic knee joint inflammation model was produced by intra-articular injection of the complete Freund's adjuvant (CFA) in rats. Nociceptive behaviors including mechanical, cold, and heat hyperalgesia were examined. The expression of Nav1.9 and PKCα in DRG was detected by a quantitative polymerase chain reaction, Western blot, and immunofluorescence. The in vitro and in vivo effects of a PKC activator (phorbol 12-myristate 13-acetate [PMA]) and a PKC inhibitor (GF-109203X) on the expression of Nav1.9 were examined. Moreover, the effects of PKC modulators on nociceptive behaviors were studied. Increased mechanical, heat, and cold sensitivity was observed 3 to 14 days after CFA injection. Parallel increases in messenger RNA and protein expression of Nav1.9 and PKCα were found. Immunofluorescence experiments found that Nav1.9 was preferentially colocalized with IB4+DRG neurons in RA rats. In cultured DRG neurons, PMA increased Nav1.9 expression while GF-109203X prevented the effect of PMA. PMA increased Nav1.9 expression in naïve rats while GF-109203X decreased Nav1.9 expression in RA rats. In naïve rats, PMA caused mechanical and cold hyperalgesia. On the other hand, GF-109203X attenuated mechanical and cold hyperalgesia in RA-pain model. Nav1.9 might be upregulated by PKCα in DRG, which contributes to pain hypersensitivity in CFA-induced chronic knee joint inflammation model of RA pain.     

Activation of extracellular signal-regulated protein kinases 5 in primary afferent neurons contributes to heat and cold hyperalgesia after inflammation

Heat and cold hyperalgesia is a common feature of inflammatory pain. To investigate whether activation of extracellular signal-regulated protein kinase 5 (ERK5), also known as big mitogen-activated protein kinase 1, in primary sensory neurons participates in inflammatory pain, we examined the phosphorylation of ERK5 in the dorsal root ganglion (DRG) after peripheral inflammation. Inflammation induced by complete Freund's adjuvant produced heat and cold hyperalgesia on the ipsilateral hind paw and induced an increase in the phosphorylation of ERK5, mainly in tyrosine kinase A-expressing small- and medium-size neurons. In contrast, there was no change in ERK5 phosphorylation in the spinal dorsal horn. ERK5 antisense, but not mismatch, oligodeoxynucleotide decreased the activation of ERK5 and suppressed inflammation-induced heat and cold hyperalgesia. Furthermore, the inhibition of ERK5 blocked the induction of transient receptor potential channel TRPV1 and TRPA1 expression in DRG neurons after peripheral inflammation. Our results show that ERK5 activated in DRG neurons contribute to the development of inflammatory pain. Thus, blocking ERK5 signaling in sensory neurons that has the potential for preventing pain after inflammation.     

Expression and function of proton-sensing G-protein-coupled receptors in inflammatory pain

Background

Chronic inflammatory pain, when not effectively treated, is a costly health problem and has a harmful effect on all aspects of health-related quality of life. Despite the availability of pharmacologic treatments, chronic inflammatory pain remains inadequately treated. Understanding the nociceptive signaling pathways of such pain is therefore important in developing long-acting treatments with limited side effects. High local proton concentrations (tissue acidosis) causing direct excitation or modulation of nociceptive sensory neurons by proton-sensing receptors are responsible for pain in some inflammatory pain conditions. We previously found that all four proton-sensing G-protein-coupled receptors (GPCRs) are expressed in pain-relevant loci (dorsal root ganglia, DRG), which suggests their possible involvement in nociception, but their functions in pain remain unclear.

Results

In this study, we first demonstrated differential change in expression of proton-sensing GPCRs in peripheral inflammation induced by the inflammatory agents capsaicin, carrageenan, and complete Freund's adjuvant (CFA). In particular, the expression of TDAG8, one proton-sensing GPCR, was increased 24 hours after CFA injection because of increased number of DRG neurons expressing TDAG8. The number of DRG neurons expressing both TDAG8 and transient receptor potential vanilloid 1 (TRPV1) was increased as well. Further studies revealed that TDAG8 activation sensitized the TRPV1 response to capsaicin, suggesting that TDAG8 could be involved in CFA-induced chronic inflammatory pain through regulation of TRPV1 function.

Conclusion

Each subtype of the OGR1 family was expressed differently, which may reflect differences between models in duration and magnitude of hyperalgesia. Given that TDAG8 and TRPV1 expression increased after CFA-induced inflammation and that TDAG8 activation can lead to TRPV1 sensitization, it suggests that high concentrations of protons after inflammation may not only directly activate proton-sensing ion channels (such as TRPV1) to cause pain but also act on proton-sensing GPCRs to regulate the development of hyperalgesia.     

Sustained neurochemical plasticity in central terminals of mouse DRG neurons following colitis

Sensitization of dorsal root ganglia (DRG) neurons is an important mechanism underlying the expression of chronic abdominal pain caused by intestinal inflammation. Most studies have focused on changes in the peripheral terminals of DRG neurons in the inflamed intestine but recent evidence suggests that the sprouting of central nerve terminals in the dorsal horn is also important. Therefore, we examine the time course and reversibility of changes in the distribution of immunoreactivity for substance P (SP), a marker of the central terminals of DRG neurons, in the spinal cord during and following dextran sulphate sodium (DSS)-induced colitis in mice. Acute and chronic treatment with DSS significantly increased SP immunoreactivity in thoracic and lumbosacral spinal cord segments. This increase developed over several weeks and was evident in both the superficial laminae of the dorsal horn and in lamina X. These increases persisted for 5 weeks following cessation of both the acute and chronic models. The increase in SP immunoreactivity was not observed in segments of the cervical spinal cord, which were not innervated by the axons of colonic afferent neurons. DRG neurons dissociated following acute DSS-colitis exhibited increased neurite sprouting compared with neurons dissociated from control mice. These data suggest significant colitis-induced enhancements in neuropeptide expression in DRG neuron central terminals. Such neurotransmitter plasticity persists beyond the period of active inflammation and might contribute to a sustained increase in nociceptive signaling following the resolution of inflammation.     

Nerve growth factor induces P2X(3) expression in sensory neurons

Glial cell line-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) are neuroprotective for subpopulations of sensory neurons and thus are candidates for pain treatment. However, delivering these factors to damaged neurons will invariably result in undamaged systems also being treated, with possible consequences for sensory processing. In sensory neurons the purinergic receptor P2X(3) is found predominantly in GDNF-sensitive nociceptors. ATP signalling via the P2X(3) receptor may contribute to pathological pain, suggesting an important role for this receptor in regulating nociceptive function. We therefore investigated the effects of intrathecal GDNF or NGF on P2X(3) expression in adult rat spinal cord and dorsal root ganglia (DRG). In control spinal cords, P2X(3) expression was restricted to a narrow band of primary afferent terminals within inner lamina II (II(i)). Glial cell line-derived neurotrophic factor treatment increased P2X(3) immunoreactivity within lamina II(i) but not elsewhere in the cord. Nerve growth factor treatment, however, induced novel P2X(3) expression, with intense immunoreactivity in axons projecting to lamina I and outer lamina II and to the ventro-medial afferent bundle beneath the central canal. In the normal DRG, we found a greater proportion of P2X(3)-positive neurons at cervical levels, many of which were large-diameter and calcitonin gene-related peptide-positive. In both cervical and lumbar DRG, the number of P2X(3)-positive cells increased following GDNF or NGF treatment. De novo expression of P2X(3) in NGF-sensitive nociceptors may contribute to chronic inflammatory pain.     

Altered gene expression of NIDD in dorsal root ganglia and spinal cord of rats with neuropathic or inflammatory pain

Nitric oxide and nitric oxide synthases are key players in synaptic plasticity events in spinal cord (SC), which underlies the chronic pain states. To date, little is known about the molecular mechanisms regulating the activity of nitric oxide synthases in nociceptive systems. The present study was aimed at the determination of the gene expression of nNOS-interacting DHHC domain-containing protein with dendritic mRNA (NIDD), a recently identified protein regulating nNOS enzyme activity, in rat SC and dorsal root ganglia (DRG) and studying its regulation in states of nociceptive hypersensitivity in a rat model of neuropathic or inflammatory pain. It was found that NIDD mRNA was predominantly expressed in nociceptive primary neurons and in neurons of the spinal dorsal horn (DH) and the number of NIDD-positive neurons in the corresponding DRG or SC increased significantly following induction of chronic hyperalgesia. Meanwhile, remarkable changes of nNOS were detected under such pain conditions. Our data suggest a potential role for NIDD in the maintenance of thermal pain hypersensitivity possibly via regulating the nNOS activity. Meng-Ling Chen and Chun Cheng are contributed equally to this work.