Constitutive and inducible nitric oxide synthases after dynorphin-induced spinal cord injury

It has recently been demonstrated that selective inhibition of both neuronal constitutive and inducible nitric oxide synthases (ncNOS and iNOS) is neuroprotective in a model of dynorphin (Dyn) A(1-17)-induced spinal cord injury. In the present study, various methods including the conversion of 3H-L-arginine to 3H-citrulline, immunohistochemistry and in situ hybridization are employed to determine the temporal profiles of the enzymatic activities, immunoreactivities, and mRNA expression for both ncNOS and iNOS after intrathecal injection of a neurotoxic dose (20 nmol) of Dyn A(1-17). The expression of ncNOS immunoreactivity and mRNA increased as early as 30 min after injection and persisted for 1-4 h. At 24-48 h, the number of ncNOS positive cells remained elevated while most neurons died. The cNOS enzymatic activity in the ventral spinal cord also significantly increased at 30 min 48 h, but no significant changes in the dorsal spinal cord were observed. However, iNOS mRNA expression increased later at 2 h, iNOS immunoreactivity and enzymatic activity increased later at 4 h and persisted for 24-48 h after injection of 20 nmol Dyn A(1-17). These results indicate that both ncNOS and iNOS are associated with Dyn-induced spinal cord injury, with ncNOS predominantly involved at an early stage and iNOS at a later stage.     

大鼠坐骨神经结扎后脊髓内诱导型一氧化氮合酶的表达

目的:研究坐骨神经结扎损伤后诱导型一氧化氮合酶(iNOS)在大鼠脊髓内的表达变化规律.方法:健康成年SD大鼠随机分为正常组、假手术组和坐骨神经结扎组.存活1、3、5、7、14、21、28 d后取腰4～6脊髓节段冷冻切片,用免疫组织化学方法结合图像分析技术检测脊髓内iNOS的表达变化,同时用免疫荧光双标染色技术检测14 d组中央管周围iNOS和神经肽Y(NPY)的共表达.结果:根据免疫阳性产物灰度值,损伤侧脊髓前角iNOS表达1 d明显升高,21 d达高峰,28 d接近正常,损伤后1～21 d损伤侧脊髓前角与对侧和正常组免疫阳性产物相比有统计学意义;损伤侧脊髓后角1 d iNOS表达增强,其他各组未见明显变化;损伤后中央管周围免疫阳性细胞数增多,3 d尤为明显,28 d恢复正常,免疫荧光双标染色显示14 d组iNOS和NPY在中央管周围共表达.结论:iNOS可能参与神经损伤后的再生过程及伤后神经性痛的凋节.     

mRNA and protein expression and activities of nitric oxide synthases in the lumbar spinal cord of neonatal rats after sciatic nerve transection and melatonin administration

Sciatic axotomy in 2-day-old rats (P2) causes lumbar motoneuron loss, which could be associated with nitric oxide (NO) production. NO may be produced by three isoforms of synthase (NOS): neuronal (nNOS), endothelial (eNOS) and inducible (iNOS). We investigated NOS expression and NO synthesis in the lumbar enlargement of rats after sciatic nerve transection at P2 and treatment with the antioxidant melatonin (sc; 1 mg/kg). At time points ranging from P2 to P7, expression of each isoform was assessed by RT-PCR and immunohistochemistry; catalytic rates of calcium-dependent (nNOS, eNOS) and independent (iNOS) NOS were measured by the conversion of [3H]L-arginine to [3H]L-citrulline. All NOS isoforms were expressed and active in unlesioned animals. nNOS and iNOS were detected in some small cells in the parenchyma. Only endothelial cells were positive for eNOS. No NOS isoform was detected in motoneurons. Axotomy did not change these immunohistochemical findings, nNOS and iNOS mRNA expression and calcium-independent activity at all survival times. However, sciatic nerve transection reduced eNOS mRNA levels at P7 and increased calcium-dependent activity at 1 and 6 h. Melatonin did not alter NOS expression. Despite having no action on NOS activity in unlesioned controls the neurohormone enhanced calcium-dependent activity at 1 and 72 h and reduced calcium-independent catalysis at 72 h in lesioned rats. These results suggest that NOS isoforms are constitutive in the neonatal lumbar enlargement and are not overexpressed after sciatic axotomy. Changes in NO synthesis induced by axotomy and melatonin administration in the current model are discussed considering some beneficial and deleterious effects that NO may have.     

大鼠坐骨神经损伤后诱导型一氧化氮合酶表达的变化

为了探讨大鼠坐骨神经损伤后再生过程中诱导型一氧化氮合酶(iNOS)表达的变化及意义,本研究采用大鼠坐骨神经切断缝合模型,分别于术后1、3、7、14、21及28d取吻合口远端的神经,采用免疫组织化学和实时荧光定量聚合酶链反应(RT-PCR)方法检测损伤神经远端iNOSmRNA及其蛋白的表达水平。结果显示:假手术对照组坐骨神经中未见明显的iNOS阳性产物,iNOSmRNA表达极低。实验组神经损伤后iNOSmRNA及其蛋白的表达水平均明显增高(P<0.01),iNOS阳性产物的吸光度(A)值在术后7d达高峰。iNOSmRNA表达在术后1、3、7d维持较高水平,此后则明显下降。上述结果说明大鼠坐骨神经损伤后神经纤维中iNOS的表达增加,iNOS可能在周围神经损伤后的再生过程中起着一定的作用。     

Expression of neuronal isoform of nitric oxide synthase in spinal neurons of neonatal rats after sciatic nerve transection.

Motoneuron death induced by sciatic nerve transection in neonatal rats has been related to induction of the neuronal isoform of nitric oxide synthase (nNOS), a diaphorase of which one of the cofactors is nicotinamide adenine dinucleotide phosphate (NADPH). We transected the sciatic nerve of neonatal rats (P2) and examined nNOS expression by immunostaining in neurons of the sciatic pool and of other spinal levels on the 5th day after surgery. No correspondence was observed between the surviving motoneurons and nNOS positive cells. The appearance and distribution of nNOS positive neurons at all spinal levels and laminae were similar to those of adult animals. These results are at variance with previous studies which showed correlation between motoneuron loss after axotomy and number of NADPH-diaphorase positive motoneurons after sciatic transection.     

大鼠坐骨神经横断后脊髓、背根神经节及坐骨神经Slit 2表达的变化

目的：观察 Slit 2在大鼠坐骨神经横断模型中的表达变化,为进一步研究 Slit/Robo 在周围神经再生中的作用提供实验依据。方法：SD 大鼠坐骨神经横断后用原位杂交及免疫组织化学方法检测 Slit 2在脊髓、背根神经节(DRG)和横断神经近、远端内的表达变化,图像分析方法测定阳性细胞数及平均积分光密度值。结果：正常脊髓前角运动神经元、DRG 和神经干内 Slit 2有一定的基础表达。损伤后近端神经胶质瘤、神经远端 Slit 2表达增高;DRG 内的 Slit 2表达呈现一定的时间变化,7 d 为表达高峰,14 d 下降。结论：Slit 2存在于正常成年大鼠周围神经系统,损伤可致其表达改变,Slit 2可能在周围神经再生中发挥重要作用。     

大鼠坐骨神经切断后Robo2在脊髓及背根节的表达变化

目的:研究坐骨神经损伤后Roundabout 2(Robo2)在成年大鼠背根节和脊髓的表达变化。方法:健康成年雌性SD大鼠坐骨神经切断后分别存活3～28d,取其L_(4～6)背根节(DRG)和脊髓;利用RT-PCR和免疫组织化学技术检测Robo2在上述组织中的表达变化。图像分析技术对阳性细胞的灰度值进行测定。结果:正常DRG感觉神经元表达Robo2 mRNA和蛋白质,脊髓前角运动神经元不表达。坐骨神经切断后3 d DRG内Robo2表达增加,7～14 d达高峰,21～28 d恢复到正常水平。结论:坐骨神经切断可导致DRG内Robo2的表达上调,可能与早期的感觉轴突再生有关。     

Glial cell proliferation in the spinal cord after dorsal rhizotomy or sciatic nerve transection in the adult rat

Proliferation of glial cells is one of the hallmarks of CNS responses to neural injury. These responses are likely to play important roles in neuronal survival and functional recovery after central or peripheral injury. The boundary between the peripheral nervous system (PNS) and CNS in the dorsal roots, the dorsal root transitional zone (DRTZ), marks a distinct barrier for growth by injured dorsal root axons. Regeneration occurs successfully in the PNS environment, but ceases at the PNS-CNS junction. In order to understand the role of different glial cells in this process, we analysed the proliferation pattern of glial cells in central (CNS) and peripheral (PNS) parts of the dorsal root and the segmental white and grey spinal cord matter after dorsal rhizotomy or sciatic nerve transection in adult rats 1-7 days after injury. Monoclonal antibody MIB-5 or antibodies to bromodeoxyuridine were used to identify proliferating cells. Polyclonal antibodies to laminin were used to distinguish the PNS and CNS compartments of the dorsal root. Dorsal root lesion induced glial cell proliferation in the CNS as well as PNS beginning at 1 day, with peaks from 2 to 4 days postoperatively. After sciatic nerve injury, cell proliferation occurred only in the CNS, was minimal at 1 day, and peaked from 2 to 4 days postoperatively. Double immunostaining with specific glial cell markers showed that after dorsal root transection 60% of the proliferating cells throughout the postoperative period examined were microglia, 30% astrocytes and 10% unidentified in the CNS, while in the PNS 40% were Schwann cells, 40% macrophages and 20% unidentified. After sciatic nerve injury virtually all proliferating cells were microglia. These findings indicate that non-neuronal cells in the CNS and PNS are extremely sensitive to the initial changes which occur in the degenerating dorsal root axons, and that extensive axonal degeneration is a prerequisite for astroglial and Schwann cell, but not microglial cell, proliferation.     

The role of inducible nitric oxide synthase following spinal cord injury in rat

Acute spinal cord injury (SCI) is two-step process that first involves the primary mechanical injury and then the secondary injury is induced by various biochemical reactions. Apoptosis is one of secondary SCI mechanisms and it is thought to play an important role for the delayed neuronal injury. The enhanced formation of nitric oxide (NO) via inducible nitric oxide synthase (iNOS) has been implicated in the pathogenesis of apoptosis in SCI. The level of .iNOS mRNA peaked at 6 hr after SCI and it declined until 72 hr after SCI in a rat model. Double-immunofluorescence staining revealed that iNOS positive cells were stained for ED-1, synaptophysin, GFAP, and oligodendrocyte marker. The terminal deoxynucleotidyl-transferase-mediated dUDP-biotin nick end-labeling (TUNEL) positive cell count was higher for the 72 hr post-SCI group than for the 24 hr post-SCI group. This cell count was also higher going in the caudal direction than in the rostral direction from the epicenter, and especially for the 72 hr group. Treatment with a selective iNOS inhibitor resulted in the reduction of TUNEL-positive cells at the lesion site. These findings suggest that nitric oxide generated by the iNOS of macrophages, neurons, oligodentrocytes, and astrocytes plays an important role for the acute secondary SCI that results from apoptotic cell death.     

Ultrastructural changes in the gracile nucleus of the rat after sciatic nerve transection

Summary Ultrastructural changes in the gracile nucleus of the rat have been examined after peripheral nerve injury. The sciatic nerve of adult rats was transected at mid-thigh level, and after survival times ranging from 1 day to 32 weeks sections from the gracile nucleus were prepared for electron microscopic examination. Unoperated animals served as controls. Atypical profiles were regularly observed in the experimental cases at post-operative survival times from 3 days up to 32 weeks. It was sometimes not possible to classify these as pre-terminal axons or terminals, because synaptic contacts could not be identified. The two most common changes throughout the entire post-operative period were greatly expanded myelinated axons, or unmyelinated profiles containing numerous mitochondria, osmiophilic dense bodies and vacuoles. Atypical profiles were occasionally observed in unoperated control animals. The results clearly show that various types of degenerative changes occur in the gracile nucleus after peripheral nerve injury. These changes differ markedly from previously described transganglionic changes in other systems. It cannot be excluded that some of the changes reflect growth-related reactions, although the typical features of axon regeneration could not be found.     

Long-term changes in the distribution of galanin in dorsal root ganglia after sciatic or spinal nerve transection in rats

The neuropeptide galanin is upregulated in primary afferent and sympathetic neurones and might be involved in the development of sympathetic perineuronal baskets ("rings") following nerve injury. Galanin, calcitonin gene-related peptide and tyrosine hydroxylase have been examined immunohistochemically in dorsal root ganglia and associated roots at times up to one year after transection of either sciatic or L5 spinal nerves in adult rats. Small diameter somata containing calcitonin gene-related peptide (with or without galanin) were reduced in number, whereas galanin (and, at later times, calcitonin gene-related peptide) appeared in medium to large diameter cells after both types of lesion. Galanin also appeared in axons in grey rami and somata in lumbar paravertebral ganglia. Within dorsal root ganglia, galanin-positive axons formed perineuronal rings of two types: (i) smooth coiled axons surrounded small (< 30 microm diameter) somata from which they probably arose; these were rare after 12 weeks, particularly after a spinal nerve lesion; and (ii) varicose terminals encircled medium to large galanin-positive somata; some arose from brightly immunofluorescent somata nearby and took nearly a year to disappear. About 30% of varicose galanin-positive rings had associated calcitonin gene-related peptide-positive terminals (partly colocalized) whereas nearly 45% had associated tyrosine hydroxylase-positive terminals (partly colocalized). Synaptophysin was present in swollen axons and in some varicosities of all types.We conclude that, after peripheral nerve lesions, varicose perineuronal rings around large diameter dorsal root ganglion cells may be formed by axotomized primary afferent neurones (some containing calcitonin gene-related peptide) and sympathetic neurones, both of which contain upregulated galanin. Exocytosis from the varicosities may modify the excitability of mechanosensitive somata. Small galanin-positive somata disappear over several months after both lesions as calcitonin gene-related peptide reappears in medium to large neurones.     

Augmentation of hypoxia-induced nitric oxide generation in the rat carotid body adapted to chronic hypoxia: an involvement of constitutive and inducible nitric oxide synthases

Acute hypoxia increases the endogenous release of nitric oxide (NO) in rat carotid body and the expression of nitric oxide synthases is modulated by chronic hypoxia. The aim of the study was to examine hypoxia-induced NO generation in rat carotid body adapted to chronic hypoxia with inspired oxygen at 10% for 4 weeks. The concentration of NO was measured electrochemically with a Pt/Nafion/Pd-IrOx/POAP modified electrode inserted into the isolated carotid body superfused with bicarbonate-buffer saline at 35 degrees C. Acute hypoxia increased the concentration of NO by 471.3+/-71.4 nM in the carotid body of chronically hypoxic (CH) rats. The amount of NO release induced by hypoxia was significantly augmented when compared with that of the normoxic control (87.6+/-15.9 nM). The hypoxia-induced NO generation was markedly attenuated by pretreatment with L- NG-nitroarginine methylester (L-NAME; 500 microM), a non-selective nitric oxide synthase (NOS) inhibitor and also by removal of extracellular calcium with the calcium chelator EGTA (5 mM). Additionally, NO generation during hypoxia was reduced by 30% in the CH carotid body treated with S-methylisothiourea (SMT; 50 microM), a specific blocker of inducible NOS (iNOS). Immunohistochemical study revealed that positive iNOS protein immunoreactivity was detected in clusters of glomus cells in the carotid bodies of CH rats, but not in the normoxic group. Thus, chronic hypoxia enhances hypoxia-induced NO generation mediated by calcium-dependent NOSs and iNOS in the carotid body. Extracellular recording of sinus nerve activity of CH carotid bodies showed that L-NAME treatment enhanced the afferent discharge in response to hypoxia, confirming that the generation of NO suppresses the activities of carotid chemoreceptors. Taken together, our results suggest that hypoxia-induced NO production increases in the rat carotid body adapted to chronic hypoxia and that constitutive and inducible NOSs are involved in the NO generation. The enhancement of NO generation may play a physiological role in blunting the hypoxic chemosensitivity during chronic hypoxia.     

诱导型一氧化氮合酶在强啡肽致脊髓损伤中的作用

目的：探讨诱导型一氧化氮合酶（ｉＮＯＳ）在强啡肽致脊髓损伤中的作用。方法：［３Ｈ］－左旋精氨酸转化法测定腹侧和背侧脊髓ｉＮＯＳ活性,原位杂交法观测脊髓ｉＮＯＳｍＲＮＡ表达及其细胞分布。结果：大鼠蛛网膜下腔注射（ＩｎＩ）强啡肽Ａ１－１７（Ｄｙｎ）２０ｎｍｏｌ引起持久性截瘫和迟发性神经元死亡;在Ｄｙｎ致瘫后２～３ｈｉＮＯＳｍＲＮＡ表达开始增多增强,４ｈ达高峰,２４ｈ和４８ｈ仍见广泛表达,其分布以胶质细胞和大运动神经元为主;腹侧脊髓ｉＮＯＳ活性在Ｄｙｎ致瘫后４ｈ显著升高,并持续至２４ｈ和４８ｈ;提前１０ｍｉｎＩｎＩ选择性ｉＮＯＳ抑制剂氨基胍１μｍｏｌ可显著对抗Ｄｙｎ２０ｎｍｏｌ引起的持久瘫及伤后４ｈ腹侧脊髓ｉＮＯＳ活性升高。结论：ｉＮＯＳ持续性高表达与Ｄｙｎ致脊髓损伤机制有关     

The morphological changes of the spinal motoneurons after peripheral nerve transection in the chicken

The cellular response of motoneurons and glial cells of the chicken spinal cord was observed following brachial plexectomy. The axotomized motoneurons initially showed an irregular nuclear membrane. Subsequently, they showed the appearance of a perineuronal space and the increase in number of glycogen granules. At 10 and 20 d post-operatively, the axon reaction reached a peak and the axotomized motoneurons contained abundant glycogen granules, and tended to an increase electron density in electron microscopy or an increased basophilia in light microscopy compared to those of the control. Elongated microglial cells appeared as satellites to the axotomized cells. The perineuronal space extended with the post-operative days. From 30 post-operative days forward, the axotomized motoneurons recovered with the post-operative days. The axotomized motoneurons did not show chromatolysis during axon reaction.     

坐骨神经切断对猫脊髓前角蛋白组表达的影响

用蛋白组学方法探讨猫双侧坐骨神经切断后脊髓前角蛋白组表达变化,找出差异蛋白。用二维凝胶电泳法获得脊髓前角蛋白组的考马斯亮蓝染色图谱,PDQuest软件对蛋白点进行定量分析。结果显示:在凝胶图谱中平均检测到382个蛋白点。损伤组与正常组比较后检测到11个明显差异蛋白。经基质辅助激光解析电离飞行时间质谱和串联质谱技术鉴定差异蛋白。其名称分别为:蛋白二硫键异构酶、磷酸苷油酸变位酶1、热休克蛋白70、ATP合成酶α链、丙酮酸脱氢酶β亚基、载脂蛋白A前体、肌球蛋白调节轻链异构体b/2、三磷酸苷油醛脱氢酶等。本实验鉴定了外周神经损伤后与脊髓前角变化相关的蛋白分子,为了解运动神经元轴突损伤所致的胞体蛋白组变化奠定了基础。     

坐骨神经损伤后VIP在大鼠脊髓腰段后角中的动态变化

结扎切断SD大鼠左侧坐骨神经或前后根后,在一定的存活时间序列里,用Olympus显微镜的测光装置对经PAP法显色处理后的大鼠腰段脊髓切片后角的VIP(血管活性肠肽)进行了相对变化率(X_c/X_c-1)×100%的测定.结果发现:坐骨神经结扎切断后,术侧VIP在各个时间的值都高于对照侧;术后15天增高至125%(P<0.01),30天时仅增高至27.2%(P<0.05),120天时增高至50.7%(P<0.01)变化曲线呈双峰夹谷状.     

大鼠坐骨神经受压和解压后背根节和脊髓内神经元nNOS表达的变化

目的 :观察坐骨神经受压及解压后大鼠腰段背根节和脊髓内神经元型一氧化氮合酶 (nNOS)表达的变化 ,借以探讨外周神经源性痛的发病和影响机制。方法 :大鼠随机分为压迫组、解压组和对照组 ,采用聚乙烯管压迫坐骨神经的动物模型 ,用免疫细胞化学方法并结合计算机图像分析进行研究。结果 :与对照组比较 ,压迫组和解压组腰4～ 6背根节中nNOS的表达显著增加 ,相应节段脊髓背角的表达则明显降低 ;解压组与压迫组比较 ,背根节中nNOS的表达明显减少 ,而脊髓背角的已经下调的nNOS表达则回升 ,但仍然低于对照组水平。结论 :NO可能与神经源性痛时在中枢和外周的痛觉敏感性形成和神经系统长时程改变有关。     

The effect of spinal cord transection on renal water excretion

Summary It was established that section of the spinal cord brings about decreased water dluresis. The higher the level of the section the greater the development of water diuresis. This phenomenon is not connected with delay in the water absorption from the gastro-intestinal tract, or with decreased filtration in the kidney glomeruli. Disturbance of water exctetory function of the kidney following section of the spinal cord is connected with the break of the afferent routes from the osmoreceptors to the nuclei of the hypothalamic area.Presented by Academician L. A. Orbeli     

锌对坐骨神经损伤小鼠脊髓运动神经元的保护作用

目的研究锌对坐骨神经损伤(sciatic nerve injury,SNI)模型小鼠脊髓前角运动神经元的保护作用。方法 48只CD1小鼠随机分4组,SNI小鼠模型,假手术组,低锌组(SNI后每天腹腔注射氯碘羟喹10mg/kg·d);高锌组(SNI后每天腹腔注射氯化锌溶液20 mg/kg·d)。应用原子吸收光谱技术、免疫组织化学技术和图像分析技术检测SNI后第7天锌含量变化对模型动物脊髓前角运动神经元caspase-3表达的影响。结果损伤组脊髓的锌含量降低,脊髓前角运动神经元caspase-3表达上调,阳性细胞百分比增大,光密度增加(0.01)。高锌组能增加脊髓的锌含量,下调caspase-3表达,降低阳性细胞百分比和光密度(0.01);而P低锌组则使脊髓的锌含量更少,caspase-3表达更多,阳性细胞百分比和光密度更高(0.01)。结论锌能抑制SNI模型小鼠脊髓前角运动神经元caspase-3的表达,锌对运动神经元具有保护作用。     

坐骨神经预损伤对脊髓损伤后小鼠神经功能恢复的影响

目的研究坐骨神经预损伤对脊髓损伤后小鼠神经功能恢复的影响。方法以C57BL/6小鼠为研究对象,分为假手术组(对照组,Control),脊髓损伤(spinal cord injury, SCI)组和坐骨神经预损伤(sciatic nerve injury,SNI)组。假手术组仅移除小鼠T8-T10椎骨上棘暴露胸髓,SCI组移除小鼠T8-T10椎骨上棘暴露胸髓给予外力打击造成标准损伤,SNI组小鼠手术切断右腿坐骨神经,在预损伤7d后进行脊髓损伤。在恢复期(即脊髓损伤14d后),通过电生理实验检测运动神经传导功能,通过组织病理学检验检测组织缺损恢复、髓鞘再生及小胶质细胞的募集活化。结果电生理实验表明SNI组小鼠运动传导功能恢复明显强于SCI组;HE染色结果说明SNI组脊髓组织缺损恢复情况明显强于SNI组;以MBP为指标的免疫荧光结果显示SNI组髓鞘含量明显多于SCI组,髓鞘再生能力明显增强;以IBA-1为指标的免疫荧光结果显示SNI组小胶质细胞明显增多,坐骨神经预损伤明显增强了小胶质细胞的募集活化作用。结论坐骨神经预损伤处理可促进小鼠脊髓损伤后组织形态恢复、小胶质募集活化作用、髓鞘再生作用和神经传导功能的恢复。