大鼠坐骨神经切断后腰脊髓腹角内胶质细胞和神经元的可塑性变化

目的:探讨大鼠单侧坐骨神经切断后腰脊髓腹角胶质细胞和运动神经元的反应及其相互关系.方法:用免疫组织化学技术、HE染色和Tunnel法,观察坐骨神经切断后1,6,12,24 h及3,7和14 d腰脊髓腹角胶质原纤维酸性蛋白(GFAP)标记的星形胶质细胞、OX-42标记的小胶质细胞及运动神经元的变化.结果:坐骨神经切断侧腰脊髓腹角可见星形胶质细胞和小胶质细胞活化,星形胶质细胞的活化早于小胶质细胞;后期运动神经元发生凋亡,HE染色显示凋亡细胞周围为反应性OX-42阳性小胶质细胞和GFAP阳性星形胶质细胞包绕.结论:研究结果提示,坐骨神经切断后切断侧腰脊髓腹角活化的胶质细胞与凋亡的运动神经元之间关系密切.     

睫状神经营养因子对坐骨神经切断吻合后大鼠脊髓前角胶质纤维酸性蛋白

背景：睫状神经营养因子具有多种生物活性,在神经系统发育、分化和损伤修复中具有重要意义。 目的：观察睫状神经营养因子对坐骨神经切断吻合后大鼠相应脊髓节段前角星形胶质细胞的特异标记物胶质纤维酸性蛋白表达的影响。 方法：将SD大鼠随机分为对照组、模型组、生理盐水组及药物组。除对照组外,对所有大鼠实施双侧坐骨神经切断吻合术,药物组手术区局部注射睫状神经营养因子100 ng/kg,1次/d,生理盐水组局部注射等量生理盐水。术后1,3,7,14,21,28 d取相应脊髓节段,免疫组织化学染色观察胶质纤维酸性蛋白的表达,苏木精-伊红染色、TUNEL染色对脊髓前角神经元进行计数。 结果与结论：大鼠坐骨神经切断吻合后相应脊髓节段星形胶质细胞胞体大,突起分枝多且粗大,神经元数目逐渐减少,凋亡神经元增多,胶质纤维酸性蛋白表达增高。与模型组和生理盐水组比较,药物组神经元存活数目增多,凋亡减少,胶质纤维酸性蛋白表达明显增加(P < 0.05或P < 0.01)。同时,药物组大鼠的运动功能障碍较轻,恢复较快。说明睫状神经营养因子可以通过促进大鼠脊髓前角胶质纤维酸性蛋白的表达起到神经保护作用。 关键词：胶质纤维酸性蛋白;睫状神经营养因子;星形胶质细胞;神经元凋亡;周围神经损伤     

间歇性θ爆发式磁刺激对高血压大鼠胼胝体髓鞘及局部炎症反应的影响

目的探究间歇性θ爆发式磁刺激对慢性高血压大鼠胼胝体区域髓鞘脱失、星形胶质细胞增生和小胶质细胞活化的改善作用。方法对雄性Sprague-Dawley大鼠随机进行双肾双夹术,制作易卒中型肾血管性高血压大鼠模型。术后22周,模型制备成功的高血压大鼠随机接受连续14 d间歇性θ爆发式磁刺激治疗(intermittent theta burst stimulation,iTBS)(高血压iTBS组,n=6)或假性刺激(高血压假刺激组,n=6),假手术大鼠接受假性刺激(假手术假刺激组,n=6)。HE染色观察胼胝体小动脉形态。免疫荧光染色观察胼胝体MBP标记的髓鞘脱失情况。免疫荧光染色观察GFAP标记的星形胶质细胞数量和IBa-1标记的小胶质细胞数量和形态,以评价星形胶质细胞增生和小胶质细胞活化。结果高血压iTBS组和高血压假刺激组出现明显小动脉管壁增厚。与假手术假刺激组相比,高血压假刺激组胼胝体MBP阳性面积比例减少(P<0.01),GFAP阳性细胞和IBa-1阳性细胞数量明显增加(P<0.01),IBa-1阳性细胞胞体增大,突起变粗,分枝变少。iTBS治疗明显增加了高血压大鼠胼胝体MBP阳性面积比例,降低GFAP阳性细胞和IBa-1阳性细胞数量(P<0.01),IBa-1阳性细胞胞体变小,突起变细,分枝变多。结论iTBS治疗可减轻高血压大鼠胼胝体区域髓鞘脱失,抑制星形胶质细胞增生和小胶质细胞活化。     

缺血缺氧对体外培养星形胶质细胞细胞周期和增殖的影响

目的 观察缺血缺氧损伤对星形胶质细胞细胞周期和增殖的影响。方法 用流式细胞仪检测缺血缺氧后不同时问点星形胶质细胞细胞周期变化，并用荧光免疫细胞化学技术测定胶质细胞纤维酸性蛋白(GFAP)和增殖细胞核抗原(PCNA)的表达水平。结果 体外缺血缺氧损伤后星形胶质细胞S期较正常组明显增高，6h达高峰，而随后则呈下降趋势。PCNA阳性反应损伤后表达均增加，6h表达最高；在缺血缺氧早期，GFAP阳性染色增强，6h最高；缺血缺氧12h后GFAP阳性染色变弱。结论 缺血缺氧损伤后星形胶质细胞活化进入增殖期；PCNA参与了损伤后星形胶质细胞的修复和增殖；细胞周期事件与星形胶质细胞的活化密切相关。     

重复经颅磁刺激对大鼠海马、齿状回胶质纤维酸性蛋白、Ⅲ型补体受体表达的影响

目的观察重复经颅磁刺激(rTMS)对大鼠海屿、齿状间星形胶质细胞和小胶质细胞标记物胶质纤维酸性蛋白(GFAP)、Ⅲ型补体受体(OX-42)表达的影响。方法每日1次给予大鼠1Hz、100mT的TMS 10 min,共14d,观察大鼠行为的变化;14d后采用免疫组化ABC法检测其海马、齿状间GFAP、OX-42的表达,并与对照组比较。结果rTMS组、对照组大鼠海马、齿状MGFAP、OX-42阳性表达物在形态、数量等方面差异无显著性。结论本实验条件下的rTMS不会造成大鼠中枢神经系统明显损伤。     

氯胺酮对NMDA诱导大鼠脊髓背角星形胶质细胞损伤的保护作用

目的观察氯胺酮对N-甲基-D-天冬氨酸(NMDA)受体过度激活诱导大鼠脊髓背角星形胶质细胞凋亡影响,并探讨其可能的作用机制.方法取新生2～3 d wistar大鼠T11-L6脊髓背角星形胶质细胞原代纯化培养,GFAP鉴定星形胶质细胞纯度达98%后用于实验.将细胞随机分6组:对照组(C组),NMDA组(N组),氯胺酮组(K组)和三种不同浓度氯胺酮加NMDA组(0.1,0.5,1 mmol/L,标记为NK1～NK3组),再培养24 h后检测SOD活性和MDA含量,免疫组化HE复染观察Bcl-2蛋白和形态学变化,流式细胞仪检测星形胶质细胞凋亡率.结果N组细胞发生了大量凋亡,SOD活性显著降低,MDA含量明显增加,Bcl-2蛋白表达不明显;NK3组细胞凋亡被显著抑制,Bcl-2蛋白强阳性表达,SOD活性明显增加和MDA含量低.结论NMDA受体过度激活可诱导大鼠脊髓背角星形胶质细胞大量凋亡,适量氯胺酮显著抑制了细胞凋亡,其机制可能是增强了星形胶质细胞Bcl-2蛋白表达,同时抑制了自由基的产生和增强了SOD活性.     

GFAP和Fos蛋白在戊四氮致痫大鼠前脑中的表达变化

目的 研究大鼠在戊四氮导致癫痫发作时前脑内星形胶质细胞和神经元的形态学反应及其相互关系。方法 应用免疫组织化学单标记法分别显示前脑内GFAP和Fos蛋白表达的时间规律，并用免疫组织化学双重标记显示GFAP和Fos蛋白表达的相互关系。结果 在戊四氮导致大鼠癫痫发作早期，前脑的星形胶质细胞被激活，细胞体积增大，突起粗大，GFAP表达阳性，随着存活时间的变化，星形胶质细胞的反应经历先逐渐升高后降低的过程。被激活的星形胶质细胞和神经元表达Fos蛋白阳性，也呈现逐渐升高又降低的变化；另外，GFAP阳性星形胶质细胞和Fos阳性神经元在前脑主要分布在大脑皮层、海马、杏仁核等部位，二者的分布特征基本一致。结论 星形胶质细胞可能和神经元一起参与了戊四氮所致癫痫发作的变化。     

胶质纤维酸性蛋白与中枢神经系统疾病

<正>胶质纤维酸性蛋白(Glial Fibrillary Acidic Protein,GFAP) 是分子量为50-52kD的酸性蛋白,是星形胶质细胞的主要成分 之一,富含谷氨酸和天冬氨酸,以中间微丝蛋白和可溶性蛋白 两种形式存在于胶质细胞的胞浆中,是星形胶质细胞的骨架蛋 白。GFAP在星形胶质细胞受到刺激引起反应时,其表达发生 变化,因此GFAP能够用来特异性地标记星形胶质细胞、并被 认为是星形胶质细胞活化的标志。活化的星形胶质细胞 内GFAP的增高,可能起保护神经元的作用;星形胶质细胞在 损伤区分泌多种神经营养因子,以促进中枢神经和周围神经轴     

少突胶质细胞功能障碍与肌萎缩侧索硬化症

正肌萎缩侧索硬化症(amyotrophic lateral sclerosis,ALS)是一种神经系统变性疾病,以大脑皮质、脑干、脊髓前角运动神经元选择性丢失为特征,目前发病机制不清,尚无有效治疗手段~[1]。大量研究表明运动神经元变性是一种非神经细胞自主性过程,星形胶质细胞和小胶质细胞参与神经元的死亡~[2]。最近,少突胶质细胞在ALS发病机制中的作用日益受到关注。本文就少     

大鼠下丘脑室旁核小胶质细胞对次声的反应

目的探讨次声作用后大鼠下丘脑室旁核小胶质细胞与星形胶质细胞的变化及其相互关系。方法将SD大鼠反复暴露于声压级16Hz130dB的次声环境中。用抗大鼠Ⅲ型补体受体标志物（0X42）和抗胶质细胞原纤维酸性蛋白（GFAP）的免疫组化方法，观察次声作用后即刻，7d，14d大鼠下丘脑室旁核小胶质细胞与星形胶质细胞的变化及其相互关系。结果正常大鼠下丘脑室旁核的小胶质细胞和星形胶质细胞的数量较少，一般为静息性形态，胞体小，突起细长，染色浅淡。次声作用后大鼠下丘脑小胶质细胞被激活，胞体变大，突起短粗，染色深，7d以后逐渐减弱；次声作用后第7d起星形胶质细胞变多，胞体变大，突起变粗，染色深，第14d达到高潮；小胶质细胞和星形胶质细胞之间的关系密切。结论次声作用后小胶质细胞比星形胶质细胞早被激活；两者的关系密切。     

Expression of insulin-like growth factors and corresponding binding proteins (IGFBP 1–6) in rat spinal cord and peripheral nerve after axonal injuries

Insulin-like growth factors (IGFs) exert trophic effects on several different cell types in the nervous system, including spinal motoneurons. After peripheral nerve injury, the increased expression of IGFs in the damaged nerve has been suggested to facilitate axonal regeneration. Here we have examined the expression pattern of mRNAs encoding IGF-1 and and -2, IGF binding proteins (IGFBPs) 1–6 in the rat spinal cord and peripheral nerve in three lesion models affecting lumbar motoneurons, i.e., sciatic nerve transection, ventral root avulsion, and a cut lesion in the ventral funiculus of the spinal cord. The expression was also studied in enriched Schwann cell and astrocyte cultures. The injured sciatic nerve expressed IGF-1 and IGF-2 as well as IGFBP-4 and IGFBP-5, whereas central nervous system (CNS) scar tissue expressed IGF-1, IGFBP-2, and IGFBP-5. IGFBP-6 mRNA was strongly upregulated in spinal motoneurons after all three types of lesions. IGFBP-6-like immunoreactivity was present in motoneuron cell bodies, dendrites in the ventral horn, and axons in the sciatic nerve. In line with the in vivo findings, cultured Schwann cells expressed IGF-1, IGF-2, IGFBP-4, and IGFBP-5 mRNAs, whereas cultured astrocytes expressed IGF-1, IGFBP-2, and IGFBP-5 mRNAs. These findings show that IGF-1 is available for lesioned motoneurons both after peripheral and central axonal lesions, whereas there are clear differences in the expression patterns for IGF-2 and some of the binding proteins in CNS and peripheral nervous system (PNS) scar tissue. The robust upregulation of IGFBP-6 mRNA in lesioned motoneurons suggests that this binding protein may be of special relevance for the severed cells. J. Comp. Neurol. 400:57–72, 1998. © 1998 Wiley-Liss, Inc.     

Light and electron microscopic localization of B-50 (GAP43) in the rat spinal cord during transganglionic degenerative atrophy and regeneration.

Crush or transection of a peripheral nerve is known to induce transganglionic degenerative atrophy (TDA) in the segmentally related, ipsilateral Rolando substance of the spinal cord. When the lost peripheral connectivity is reestablished, the consecutive regenerative synaptoneogenesis results in restoration of the circuitry in the formerly deteriorated upper dorsal horn. Enhanced expression of the growth-associated protein (GAP43) B-50 occurs during neuronal differentiation, axon outgrowth, and peripheral nerve regeneration. This study documents changes in immunocytochemical distribution of B-50 in the regions of the lumbar spinal cord which are segmentally related to the axotomized sciatic nerve. At the light microscopic level, a weak B-50 immunoreactivity (BIR) is present in the neuropil of the upper dorsal horn of control animals. After unilateral transection and ligation of the sciatic nerve, BIR increased in the ipsilateral upper dorsal horn at 17 days postinjury, but decreased again after 24 days with respect to the contralateral side. Differences between effects of crush and transection were prominent in combined crush-cut experiments as well (i.e., after unilateral crush and contralateral transection and ligation of the sciatic nerve). Electron microscopic studies show that in the uninjured and injured spinal cord, BIR is detected in axons and axon terminals, but not all are stained. After transection of the sciatic nerve, BIR is found in afflicted primary sensory axon terminals, including those contacting substantia gelatinosa neurons and in axon terminals undergoing glial phagocytosis. The localization of BIR seen after crushing the sciatic nerve is similar. However, at 24 days after crush, BIR is detected also in axonal growth cones. In the ventral horn of control animals, synaptic boutons impinging upon motor neurons exhibited weak BIR. At 17 days after unilateral transection of the sciatic nerve, the pericellular BIR surrounding motor neurons is decreased at the ipsilateral with respect to the contralateral side, whereas 24 days after crush injury it increased considerably. Our results show that peripheral nerve injury inducing TDA also affects BIR distribution in the spinal gray matter. Successful regeneration of the peripheral nerve after crush lesion is associated with enhanced expression of B-50 in growth cones of sprouting central axons. The neuroplastic response of B-50 is in line with a function of B-50 in axonal sprouting and reactive synaptogenesis.     

Apoptosis of spinal interneurons induced by sciatic nerve axotomy in the neonatal rat is counteracted by nerve growth factor and ciliary neurotrophic factor

We have previously shown that not only motoneurons and dorsal root ganglion cells but also small neurons, presumably interneurons in the spinal cord, may undergo apoptotic cell death as a result of neonatal peripheral nerve transection in the rat. With the aid of electron microscopy, we have here demonstrated that apoptosis in the spinal cord is confined to neurons and does not involve glial cells at the survival time studied (24 hours). To define the relative importance of the loss of a potential target (motoneuron) and a potential afferent input (dorsal root ganglion cell) for the induction of apoptosis in interneurons in this situation, we have compared the distributions and time courses for TUNEL labeling, which detects apoptotic cell nuclei, in the L5 segment of the spinal cord and the L5 dorsal root ganglion after sciatic nerve transection in the neonatal (P2) rat. In additional experiments, we studied the effects on TUNEL labeling of interneurons after treatment of the cut sciatic nerve with either ciliary neurotrophic factor (CNTF) to rescue motoneurons or nerve growth factor (NGF) to rescue dorsal root ganglion cells. The time courses of the TUNEL labeling in motoneurons and interneurons induced by the lesion show great similarities (peak at 8-48 hours postoperatively), whereas the labeling in dorsal root ganglion cells occurs later (24-72 hours). Both CNTF and NGF decrease the number of TUNEL-labeled interneurons, but there is a regional difference, in that CNTF preferentially saves interneurons in deep dorsal and ventral parts of the spinal cord, whereas the rescuing effects of NGF are seen mainly in the superficial dorsal horn. The results are interpreted as signs of a trophic dependence on both the target and the afferent input for the survival of interneurons neonatally.     

Ventral horn motoneurons 10, 20 and 52 weeks after T-9 spinal cord transection.

To determine if transneuronal degeneration occurs in ventral horn motoneurons caudal to a spinal cord transection, we completely transected the spinal cord at T-9 in seven-week-old female rats. Ten, 20 or 52 weeks later, the motoneurons of the right sciatic nerve of transected and control rats were retrogradely labeled with Fluoro-Gold. There were no differences between control and transected rats in numbers or rostrocaudal distribution of labeled motoneurons at either 10, 20 or 52 weeks. At 20 weeks, there was no significant difference between control and transected rats in mean cross-sectional area of labeled neurons. We conclude that transneuronal degeneration did not occur.     

Modulation of serotonin 5-HT3 receptor expression in injured adult rat spinal cord motoneurons

The effects of sciatic nerve lesions on the expression of serotonin 5-HT3 receptor (5-HT3R) alpha subunit in motoneurons of the spinal cord was investigated by semi-quantitative immunohistochemistry. Following sciatic nerve crush, a significant reduction in density of staining in motoneurons was observed in longitudinal sections of the ventral horn at 3 and 15 days on the lesioned side when compared to the contralateral side (p<0.01). At 30 days after crush, after completion of sciatic nerve regeneration and reinnervation of peripheral targets, intensity of staining had returned to normal. Conversely, after sciatic nerve cut, a lesion that does not allow for target reinnervation, highly significant reductions were observed at 3, 15, 30 and 45 days. These results suggest a role for functional contacts with muscular targets in the maintenance of 5-HT3R expression in spinal motoneurons.     

PACAP mRNA is expressed in rat spinal cord neurons

This study examines the expression of pituitary adenylate cyclase activating polypeptide (PACAP) mRNA in the rat spinal cord during normal conditions and in response to sciatic nerve transection. Previously, PACAP immunoreactivity has been found in fibers in the spinal cord dorsal horn and around the central canal and in neurons in the intermediolateral column (IML). Furthermore, in the dorsal root ganglia, PACAP immunoreactivity and PACAP mRNA expression have been observed preferentially in nerve cell bodies of smaller diameter terminating in the superficial laminae of the dorsal horn. However, neuronal expression of PACAP mRNA in adult rat spinal cord appeared limited to neurons of the IML. By using a refined in situ hybridization protocol, we now detect PACAP mRNA expression in neurons primarily in laminae I and II, but also in deeper laminae of the spinal cord dorsal horn and around the central canal. In addition, PACAP mRNA expression is observed in a few neurons in the ventral horn. PACAP expression in the ventral horn is increased in a population of large neurons, most likely motor neurons, both after distal and proximal sciatic nerve transection. The proposed role of PACAP in nociception is strengthened by our findings of PACAP mRNA-expressing neurons in the superficial laminae of the dorsal horn. Furthermore, increased expression of PACAP in ventral horn neurons, in response to nerve transection, suggests a role for PACAP in repair/regeneration of motor neurons.     

Distribution of choline acetyltransferase activity in rat spinal cord — Influence of primary afferents?

Summary Choline acetyltransferase (CAT) activity was measured in various regions of rat spinal cord. In the ventral cord, enzyme activity was 2 to 3 times higher than in dorsal cord. In dorsal spinal cord, there was a gradient in enzyme activity, increasing CAT activity being observed in more caudal segments. In autonomic regions intermediate levels were measured. Bilateral transection of the sciatic nerve reduced CAT activity in the ventral horn of lumbar spinal cord, whereas CAT activity in the dorsal horn remained unchanged. Capsaicin pretreatment had no effect on CAT activity in any spinal cord region. Although a similar distribution of cholinergic neurones and primary afferent endings in rat dorsal spinal cord was described, no conclusive statement as to a possible functional interaction can be given.     

Modification of astrocytes in the spinal cord following dorsal root or peripheral nerve lesions

Glial fibrillary acidic protein (GFAP) immunocytochemistry was used to monitor the response of astrocytes in the rat spinal cord to either dorsal root or sciatic nerve lesions. Image analysis methods were used to provide a quantitative correlate of the reactive gliosis. Multiple dorsal root section elicited a rapid increase in GFAP immunoreactivity of astrocytes unilaterally within the spinal cord along the pathway of the degenerating dorsal root axons in the dorsal and ventral horns and this gliosis persisted in the dorsal horn beyond the time at which active phagocytosis of degenerative debris occurred. Labeling of proliferating cells using [3H]thymidine revealed that none of the dividing cells contained detectable GFAP, suggesting that the increased GFAP labeling represents primarily a hypertrophy rather than a proliferation of astrocytes. Comparison of animals that had been deafferented in the early neonatal period with those deafferented as adults indicated that the GFAP immunoreactive response persisted following neonatal lesions but that it was markedly less intense than after adult lesions. Sciatic nerve section in adults does not result in extensive frank degeneration but it does evoke a rapid and marked increase in staining of astrocytes both in the dorsal horn and in the ventral horn. Transganglionic changes in GFAP staining in the dorsal horn occur by 3 days post-operatively, which is much earlier than the time of dorsal root ganglion neuron death caused by the sciatic nerve lesion. These experiments indicate that astrocytes can respond to signals from a variety of changes in neurons, including not only Wallerian degeneration, but also retrograde and transganglionic changes.     

Regenerating motor bridge axons refine connections and synapse on lumbar motoneurons to bypass chronic spinal cord injury

To restore motor control after spinal cord injury requires reconnecting the brain with spinal motor circuits below the lesion. A bridge around the injury is an important alternative to promoting axon regeneration through the injury. Previously, we reported a novel motor bridge in rats. The thirteenth thoracic nerve was detached from the muscle it innervates and the cut end implanted caudally into the lumbar gray matter where motor bridge axons regenerate. In this study, we first determined that regenerating bridge axons project to spinal motor circuits. Stable projections were present in ventral motor laminae of the cord, including putative synapses directly on motoneurons, 2 months after insertion in the intact cord. At this time, earlier-forming dorsal horn projections were mostly eliminated. Regenerating axons were effective in evoking leg motor activity as early as 2 weeks. We next determined that bridge axons could regenerate caudal to a chronic injury. We hemisected the spinal cord at L2 and inserted the bridge nerve 1 month later at L5 and found ventral laminae projections similar to those in intact animals, including onto motoneurons directly. Finally, we determined that the bridge circuit could be activated by neural pathways rostral to its origin. For spinally hemisected animals, we electrically stimulated the rostral spinal cord and recorded evoked potentials from the bridge and, in turn, motor responses in the sciatic nerve. Our findings suggests that bridge motoneurons could be used by descending motor pathways as premotor interneurons to transmit neural signals to bypass a chronic spinal injury.