Fluoro-Jade C染色在小鼠匹罗卡品癫痫模型中的应用

目的应用Fluoro-Jade C(FJC)染色技术在小鼠匹罗卡品癫痫模型中探测神经元变性,以了解FJC应用价值及其细胞死亡模式。方法雄性昆明小鼠6只:对照组3只;匹罗卡品处理组3只。处理组小鼠在癫痫持续状态后12 h处死,在海马水平切制冠状切片,先行FJC染色,用荧光显微镜观察;之后在切片上行FJC与Hoechst双标。结果处理组,FJC阳性细胞清晰显示,呈神经元形态,对照组未见。双标资料显示FJC(100%)与Hoechst33342双标记。结论小鼠匹罗卡品癫痫模型成功应用FJC染色技术探测了神经元变性,证实此技术在探测神经元变性方面敏感、可靠且简单,并显示此模型中FJC阳性细胞也许主要是凋亡性的。     

改良锂-匹罗卡品大鼠癫痫模型的制作及性别特点

目的 建立稳定可靠的颞叶癫痫动物模型，摸索并证实建模规律。方法 选用56只健康SD大鼠，雌雄近半，随机分配为试验组48只，对照组8只。氯化锂3mmol／kg腹腔注射预处理：18-20h后首剂注射匹罗卡品30mg／kg，此后每隔30分钟注射10mg／kg追加剂量，极量为60mg／kg，直至出现癫痫持续状态（SE）；SE1h后地西泮10mg／kg止痉，2h后注射生理盐水5mL／只，2／d．连续2d；SE后次日起灌胃鸡蛋牛奶糊7mL／只，2／d，连续6d；观察大鼠行为学改变。对照组大鼠除用等量生理盐水代替匹罗卡品外，其余处理措施均相同。结果大鼠成功点燃44只，病死10只．造模总成功只数为34。雌雄大鼠点燃只数相近．雄鼠病死只数低于雌鼠。结论中等剂量首剂．不超过3次小剂量累加腹腔注射匹罗卡品造模简易有效，可操作性强，效应匀齐。改良护理方法可明显降低病死率．雄鼠较雌鼠更适于造模。     

匹罗卡品诱发成年大鼠普遍癫痫与难治性癫痫海马神经发生的变化

背景：神经发生包括细胞增殖、迁移、分化和存活等,是人和多数哺乳动物部分脑区产生新生神经元的过程,主要分布在侧脑室下区和海马齿状回。癫痫可导致海马齿状回的神经发生改变,BrdU是目前公认最理想检测未成熟细胞增殖的标记物之一。 目的：观察匹罗卡品诱发成年大鼠癫痫后神经发生的特点,以及普通癫痫与难治性癫痫神经发生的差异。 设计、时间及地点：随机分组,细胞分子生物学实验,于2006-08/2007-06在华中科技大学同济医学院中心实验室及附属协和医院中心实验室完成。 材料：选用健康Sprague-Dawley雄性大鼠100只,随机分为2组,对照组8只,实验组92只,分为普通癫痫组,自发发作组,难治性癫痫组和非耐药组。匹罗卡品为武汉晶美公司产品,兔抗鼠BrdU抗体为美国sigma公司产品,辣根过氧化物酶标记的羊抗兔IgG为武汉博士德公司产品。 方法：对照组大鼠腹腔注射生理盐水;实验组腹腔注射匹罗卡品15mg/kg,最多注射4次,出现癫痫持续状态的大鼠注射水合氯醛终止发作。致癫大鼠癫痫发作终止后6h腹腔注射BrdU,观察自发发作情况。以脑电图、自发发作频率持续时间,无自发发作为普通癫痫组,有自发发作为自发发作组。行卡马西平灌胃2周并记录发作频率,对卡马西平治疗无效,发作频率减少<50%的为难治性癫痫组,治疗有效即发作频率减少>50%为非耐药组。普通癫痫组分别于注射后第1,2,3,7,14,21和28d取鼠脑海马部做冠状连续切片。非耐药组和难治性癫痫组的大鼠,再次行腹腔注射BrdU,每次为50mg/kg,连续注射4次,每次间隔2h,48h后取脑海马部制作石蜡切片。 主要观察指标：脑海马部切片行免疫组化染色,镜下观察不同时间点BrdU阳性细胞的分布、形态和数量及注射匹罗卡品后大鼠癫痫发作状况。 结果：匹罗卡品第1次注射后所有大鼠无癫痫发作,第2次注射发作16只,第3次注射发作42只,第4次注射后发作11只,14只大鼠4次注射仍无癫痫发作,9只大鼠癫痫持续状态后死亡,77只进入结果分析。神经发生主要位于海马颗粒细胞层和齿状回。与对照组比较,普通癫痫组BrdU阳性细胞明显增多（P<0.01）,难治性癫痫组新生细胞较普通癫痫组明显减少（P<0.01）,神经发生减少。癫痫后第2天BrdU 阳性细胞数目开始增加,14-15d达到高峰,1个月后回到初始水平。 结论：与普通癫痫相比,难治性癫痫可导致神经发生减少。     

应用Fluoro-Jade C评价匹罗卡品模型丘脑神经变性

目的 应用Fluoro-Jade C(FJC)染色方法 观察小鼠匹罗卡品癫(癎)模型丘脑神经元变性情况,以了解丘脑结构在慢性颞叶癫痫发生中的病理变化和癫(癎)反复发作的神经学基础.方法 以盐酸匹罗卡品腹腔注射(220 mg/kg)制备小鼠癫痼持续状态模型.脑组织切片经FJC染色后.荧光显微镜下观察FJC阳性细胞形态和在丘脑的整体分布情况.结果 匹罗卡品模型组小鼠FJC阳性细胞呈神经元形态,丘脑结构损害呈连续性.功能不同的丘脑核其细胞损害程度有所不同.结论 采用FJC染色技术观察匹罗卡品癫(癎)持续状态小鼠模型丘脑神经元变性情况,有利于更好地理解颞叶癫(癎)的中枢神经系统长期病理变化和自发性反复发作机制.     

单剂量匹罗卡品诱导小鼠癫痫及其海马神经损伤的研究

目的 探索不同剂量匹罗卡品单次腹腔注射对诱发小鼠癫痫及对海马损伤的影响,为癫痫建模提供参考。方法将100只健康的C57BL/6小鼠随机分为正常对照组、3个不同剂量匹罗卡品(250 mg/kg、290 mg/kg、350 mg/kg)腹腔注射组。比较3组的建模成功率、死亡率,通过免疫组化染色观察神经元和胶质细胞的数量变化,分析海马区组织的病变情况。结果 匹罗卡品250 mg/kg组小鼠的Racine评分4级以上发作率为12%,无死亡; 290 mg/kg组小鼠的4级以上发作率为70%,死亡率为32%; 350 mg/kg组小鼠的4级以上发作率为86%,死亡率为56%。免疫组化染色结果显示:与正常对照组相比,3个不同剂量匹罗卡品组小鼠诱发癫痫后,神经元数量均显著减少,小胶质细胞和星形胶质细胞数量均显著增加;但250 mg/kg组小鼠的活化小胶质细胞数量无显著变化,而其他两组显著增多。结论 匹罗卡品290 mg/kg单次注射诱发小鼠癫痫模型的成功率较高、死亡率较低,且海马区损伤明显,可以作为癫痫小鼠建模的参考方法。     

乌司他丁对氯化锂-匹罗卡品诱发癫痫大鼠脑保护作用及其机制研究

目的 研究乌司他丁对癫痫发作时大脑的保护作用及其机制。方法 通过对Wistar大鼠建立癫痫模型,建模成功后并对其进行4种分组处理,即A组注射生理盐水; B组注射卡马西平; C组注射卡马西平和少量乌司他丁(10 000 U/kg); D组注射卡马西平和大量乌司他丁(70 000 U/kg); 测量每组达到惊厥标准后24、48、72、96 h不同时间段的S100β蛋白和神经烯醇化酶(NSE)水及96 h后肿瘤坏死因子-α(TNF-α)与IL-1β水平; 通过免疫组化检测caspase-3、bax与bcl-2阳性细胞数; 观察神经元凋亡情况; 用水迷宫检测大鼠的认知功能,通过模型组与空白对照组和模型组间对比分析乌司他丁对癫痫大鼠的影响; 空白对照组全程注射等量生理盐水。结果 注射乌司他丁能够降低S100β和NSE水平,并且大剂量乌司他丁效果更显著(P<0.05); 乌司他丁对TNF-α与IL-1β表达进行抑制,且大剂量乌司他丁效果更显著(P<0.05); 注射乌司他丁后caspase-3与bax的阳性细胞减少而bcl-2的阳性细胞增加,且大剂量乌司他丁效果更显著(P<0.05); 注射乌司他丁能够减少海马CA3区神经元凋亡,且大剂量乌司他丁效果更显著(P<0.05); 注射乌司他丁能够改善癫痫大鼠的认知功能,且大剂量乌司他丁效果更显著(P<0.05)。结论 乌司他丁可能是通过抑制炎症因子的表达和caspase-3与bax的激活,促进bcl-2蛋白激活,并减少神经元凋亡来对癫痫大鼠的大脑进行保护。     

匹罗卡品致疒间大鼠海马GAP-43与TrkB基因表达及其意义

目的探讨生长相关蛋白(GAP-43)和脑源性神经营养因子(BDNF)受体TrkB基因在匹罗卡品致疒间大鼠海马的表达及其意义.方法应用原位杂交组织化学方法研究匹罗卡品(PILO)致疒间大鼠海马GAP-43及TrkB mRNA表达的变化.结果匹罗卡品致癫疒间持续状态后3～6小时,海马齿状回颗粒细胞、CA3区及CA1区锥体细胞层TrkB mRNA表达显著高于对照组(P<0.01或0.05);在慢性期第7～30天,呈现第2次表达增强.致疒间后6～12小时,正常状态下并不表达GAP-43的大鼠海马颗粒细胞其GAP-43 mRNA表达较对照组显著增高(P<0.01),24小时～7天表达减少,在癫疒间慢性期表达再次高于对照组.结论 GAP-43及TrkB是颞叶癫疒间病理基础--海马苔藓纤维出芽的重要分子机制;BDNF对苔藓纤维的作用部分是通过GAP-43实现的.     

锂—匹罗卡品致大鼠癫痫持续状态后脑内神经元的凋亡

探讨癫痫持续状态（Satatus Epilepticus,SE)时细胞凋亡的发生及其与海马硬化的关系，采用锂－匹罗卡品诱发大鼠SE模型，在SE的不同时点采大鼠脑标本，利用TUNEL染色方法检测大鼠海马皮质神经元的凋亡出现情况，结果发现，正常对照组大鼠大脑皮质可见散在的TUNEL阳性细胞，海马区未见TUNEL阳性细胞，SE1h，皮质TUNEL阳性细胞数即开始增加，SE后8h，海马区开始出现TUNEL阳性细胞，SE后1d，大脑皮质TUNEL阳性细胞数开始明显增加，海马区也可见到较多TUNEL阳性细胞，SE后5d，皮质及海马的TUNEL阳性细胞数达到高峰，7d时皮质及海马TUNEL阳性数均明显下降，结果提示，SE可引起神经元凋亡，5d时达到高峰，7d时已明显下降，神经元凋亡与SE引起的迟发性神经元死亡有关，并参与了海马硬化的形成。     

氯化锂-匹罗卡品致痫大鼠海马EphA5及ephrinA3的表达及意义

目的探讨颞叶癫痫发作后海马EphA5及ephrinA3基因的表达变化和轴突出芽的关系。方法建立氯化锂-匹罗卡品颞叶癫痫大鼠模型,利用原位杂交方法检测致痫后12h、24h、7d、15d、30d、60d海马CA3区、CA1区EphA5及ephrinA3 mRNA的表达,快速Golgi染色观察CA1区的轴突出芽。结果致痫后,EphA5 mRNA在CA3区表达下调,ephrinA3 mRNA在CA1区表达下调,均在7d降至最低点,与对照组相比差异有显著意义(P<0.01),此后逐渐回升,但15d时仍低于对照组(P<0.05),在30d和60d与对照组相比差异无统计学意义(P>0.05)。快速Golgi染色显示,对照组大鼠CA1区轴突走行正常,匹罗卡品致大鼠SE后7dCA1区锥体细胞层出现显著增多的轴突染色。结论CA3区的EphA5和CA1区的ephrinA3的表达下调可能与CA1区的轴突出芽、突触重建有关。     

锂-匹罗卡品致癫大鼠早期大脑皮质MyT1 mRNA表达变化

目的 探讨氟化锂-匹罗卡品致癫大鼠脑髓鞘转录因子1基因表达变化及其意义。方法 以氯化锂、匹罗卡品对雄性成年SD大鼠先后腹腔注射,制成癫痫持续状态动物模型;采用5′末端标记地高辛的寡核苷酸探针荧光原位核酸分子杂交检测癫性发作后早期大鼠大脑皮质MyT1 mRNA阳性细胞数量。结果 与对照组相比,癫痫后1d组大鼠脑皮质MyT1 mRNA阳性细胞数减少（P＜0.05）;其他各组大鼠脑皮质MyT1 mRNA阳性细胞数都有明显的增加,其中癫痫后7d和14d组MyT1mRNA阳性细胞数都有非常显著的增加（P＜0.05,P＜0.01）。结论 氯化锂-匹罗卡品致癫大鼠早期大脑MyT1 mRNA表达增加,并有时程性变化,提示与早期脑损伤修复有关。     

Ontogenetic profile of ectonucleotidase activities from brain synaptosomes of pilocarpine-treated rats

Adenosine, a well-known neuromodulator, can act as an endogenous anticonvulsant via the activation of adenosine A₁ receptors. This adenine nucleoside can be produced in the synaptic cleft by the ectonucleotidase cascade, which includes the nucleoside triphosphate diphosphohydrolase (NTPDase) family and ecto-5′-nucleotidase. It has been previously reported that ectonucleotidase activities are increased in female adult rats submitted to the pilocarpine model of epilepsy. Several studies have suggested that the immature brain is less vulnerable to morphologic and physiologic alterations after status epilepticus (SE). Here, we evaluate the ectonucleotidase activities of synaptosomes from the hippocampus and cerebral cortex of male and female rats at different ages (7–9, 14–16 and 27–30-day old) submitted to the pilocarpine model of epilepsy. Our results show that ATP and ADP hydrolysis in the hippocampus and cerebral cortex were not altered by the pilocarpine treatment in female and male rats at 7–9, 14–16 and 27–30 days. There were no changes in AMP hydrolysis in female and male rats submitted to the model at different ages, but a significant increase in AMP hydrolysis (71%) was observed in synaptosomes from the cerebral cortex of male rats at 27–30 days. Pilocarpine-treated male rats (60–70-day old) presented an enhancement in ectonucleotidase activities in the synaptosomes of the cerebral cortex (33, 40 and 64% for ATP, ADP and AMP hydrolysis, respectively) and hippocampus (55, 98 and 101% for ATP, ADP and AMP hydrolysis, respectively). These findings highlight differences between the purinergic system of young and adult rats submitted to the pilocarpine model of epilepsy.     

One-step labeling of degenerative neurons in unfixed brain tissue samples using Fluoro-Jade C

Neurodegeneration is the underlying cause of a vast majority of neurological disorders and often a result of brain trauma, stroke, or neurotoxic insult. Here we describe a simple method for labeling degenerating neurons in unfixed brain tissue samples. This method could provide a new avenue for identifying and harvesting degenerative neurons from unfixed brain tissues for subsequent molecular analyses.     

Kindling-induced potentiation in the piriform cortex

At intensities sufficient to induce epileptiform afterdischarges, repeated electrical stimulation of limbic structures can lead to the development of permanent increases in the strength of the epileptiform response (kindling). Field potentials evoked by pulse stimulation are also increased in amplitude in a number of forebrain pathways following kindling. This kindling-induced potentiation effect is similar in many respects to the 'long-term potentiation' (LTP) effect which is produced by non-epileptogenic stimulation. There are, however, some interesting differences. For example, kindling-induced potentiation can far outlast LTP. In these experiments, we attempted to determine the longevity of the kindling-induced potentiation of the response evoked in the piriform cortex by olfactory bulb stimulation, following olfactory bulb kindling. This system was targeted because both the olfactory bulb and the piriform cortex are highly reactive kindling sites. In addition, we used the paired pulse technique to monitor facilitation and inhibition in this system. Kindling was found to induce a potentiation in the piriform field potential that lasted for at least 3 months (the period of the experiment) with little or no decay. Kindling also produced a decrease in paired pulse facilitation. In some animals the net facilitation was changed to a net depression. These results are consistent with the interpretation that kindling produces an increase in recurrent inhibition in the piriform cortex. The paired pulse measures, however, returned to near baseline levels over the 3-month test period.     

Differences in the distribution of GABA- and GAD-immunoreactive neurons in the anterior and posterior piriform cortex of rats

There is accumulating evidence of anterior–posterior differences in the susceptibility of the piriform cortex to seizure induction and to functional alterations in response to seizures elicited from other limbic brain regions, but the reasons for such differences along the anterior–posterior axis of the piriform cortex are not clear. In the present study, GABAergic neurons have been identified in the piriform cortex of the rat at light microscopic level by immunocytochemical localization of GABA and the GABA-synthesizing enzyme glutamic acid decarboxylase. A monoclonal antibody to GABA and, for comparison, polyclonal antibodies to GABA and glutamic acid decarboxylase were used for this purpose. In both anterior and posterior piriform cortex, the highest number and density of GABA-immunoreactive cells was found in layer II. Lower density of GABAergic cells was found in layers I and III and the subjacent endopiriform cortex. When cells were quantified in 19 corresponding sections of the piriform cortex, covering most of anterior–posterior extension of this region, there appeared to be an increased density of GABAergic neurons in sections near to or within the transition zone between anterior and posterior piriform cortex. A more detailed analysis at 4 section levels in the anterior and posterior piriform cortex and the transition zone between the 2 parts substantiated a significantly higher density of GABAergic neurons in the transition zone, which was predominantly due to increased numbers of cells in layers II and III. We propose that the transition zone between anterior and posterior piriform cortex is a location where numerous GABAergic interneurons regulate the activity of neighbouring deep pyramidal cells which receive dense excitatory input from both the olfactory bulb and distant pyramidal cells in the more anterior and posterior parts of the piriform cortex at the same time, thus increasing the risk of paroxysmal activation within this restricted area. This proposal is in line with recent observations of increased susceptibility to epileptiform activation and to kindling-induced neurochemical alterations within the transition zone between anterior and posterior piriform cortex.     

Entorhinal cortex entrains epileptiform activity in CA1 in pilocarpine-treated rats

Layer III neurons of the medial entorhinal cortex (mEC) project to CA1 via the temporoammonic pathway and exert a powerful feed-forward inhibition of CA1 pyramidal neurons. The present study evaluates the hypothesis that disrupted inhibition of CA1 pyramidal neurons causes an eased propagation of entorhinal seizures to the hippocampus via the temporoammonic pathway. Using a method to induce a confined epileptic focus in brain slices, we investigated the spread of epileptiform activity from the disinhibited mEC to CA1 in control and pilocarpine-treated rats that had displayed status epilepticus and spontaneous recurrent seizures. In pilocarpine-treated rats, the mEC showed a moderate layer III cell loss and an enhanced susceptibility to epileptiform discharges compared to control animals. Entorhinal discharges propagated to CA1 in pilocarpine-treated rats but not in controls. Disconnecting CA3 from CA1 did not affect the spread of epileptiform activity to CA1 excluding its propagation via the trisynaptic hippocampal loop. Mimicking the invasion of epileptiform discharges by repetitive stimulation of the temporoammonic pathway caused a facilitation of field potentials in CA1 that were contaminated by population spikes and afterdischarges in pilocarpine-treated but not control rats. Single cell recordings of CA1 pyramidal neurons revealed a dramatic loss of feed-forward inhibition and the occurrence of strong postsynaptic excitatory potentials in pilocarpine-treated rats. Excitatory responses in CA1 were characterized by multiple NMDA receptor-mediated afterdischarges and a strong paired-pulse facilitation in response to activation of the temporoammonic pathway. Our results suggest that, irrespective of the enhanced seizure-susceptibility of the mEC in epileptic rats, the loss of feed-forward inhibition and the enhanced NMDA receptor-mediated excitability CA1 pyramidal cells ease the spread of epileptiform activity from the mEC to CA1 via the temporoammonic pathway bypassing the classical trisynaptic hippocampal loop.     

Galanin expressed in the excitatory fibers attenuates synaptic strength and generalized seizures in the piriform cortex of mice

The neuropeptide galanin is considered to be an endogenous antiepileptic agent, presumably acting via inhibition of glutamate release. Previously, we have demonstrated that in mice ectopically overexpressing galanin in cortical and hippocampal neurons, particularly in granule cells and their axons, the mossy fibers, hippocampal kindling epileptogenesis is suppressed and is associated with attenuated frequency facilitation in mossy fiber-CA3 cell synapses. We hypothesized that changes in synaptic transmission might occur also in other excitatory synapses of the galanin overexpressing (GalOE) mouse, contributing to seizure suppression. Lateral olfactory tract (LOT) synapses, formed by axons of olfactory bulb (OB) mitral cells and targeting piriform cortex (PC) pyramidal cells, ectopically express galanin in GalOE mice. Using whole-cell patch-clamp recordings, we found that excitatory synaptic responses recorded in PC pyramidal cells during high frequency stimulation of the LOT were attenuated in GalOE mice as compared to wild-type controls. This effect was mimicked by bath application of galanin or its agonist galnon to wild-type slices, supporting the notion of ectopic galanin action. Since the high frequency activation induced in vitro resembles epileptic seizures in vivo, we asked whether the observed synaptic inhibition would result in altered epileptogenesis when animals were kindled via the same synapses. In male GalOE mice, we found that the latency to convulsions was prolonged, and once animals had experienced the first stage 5 seizure, generalized seizures were less sustainable. These data indicate that the PC is a possible target for epilepsy treatment by ectopically overexpressing galanin to modulate seizure activity.     

Glutamine induces epileptiform discharges in superficial layers of the medial entorhinal cortex from pilocarpine-treated chronic epileptic rats in vitro

Purpose:   Glutamine (GLN) is a precursor for synthesis of glutamate and γ-aminobutyric acid (GABA) and has been found in the cerebrospinal fluid (CSF) at mean concentrations of 0.6 mM. Experiments on slices are usually performed in artificial CSF (aCSF) kept free of amino acids. Therefore, the role of glutamine, particularly in tissue of epileptic animals, remains elusive.
Methods:   Using extracellular recordings we studied effects of GLN on field potentials and stimulus-evoked field responses in the medial entorhinal cortex (MEC) of combined entorhinal cortex hippocampal slices from pilocarpine-treated chronic epileptic rats and age-matched saline-injected control rats.
Results:   In presence of GLN (0.5 and 2 mM) recurrent epileptiform discharges (REDs) were observed in slices from epileptic rats (64% and 80%, respectively), but not in slices from control rats. REDs were restricted to the superficial MEC, suppressed by the α-Amino-3-hydroxy-5-methyl-4-isoxazol-propionate (AMPA)/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (30 μM), attenuated by the inhibitor of neuronal glutamine transporters methylamino-isobutyric acid (10 mM), and apparently augmented and prolonged by the GABA_A receptor antagonist bicuculline-methiodide (5 μM). In contrast, amplitudes of stimulus evoked nonsynaptic and synaptic field responses increased in slices from control rats (+23% and +12% of the reference values) and insignificantly less or not in those of epileptic rats (+6.5% and −0.25%, respectively). Notably, stimulus-evoked slow negative transients confined to slices of epileptic animals were reduced in amplitude (−18%).
Discussion:   In combined entorhinal hippocampal slices from chronic epileptic animals, GLN induces glutamatergic REDs via neuronal uptake in superficial layers of the MEC where inhibitory function seemed to be partially preserved.     

Entorhinal cortex lesion studied with the novel dye fluoro-jade

We used the fluorescent dye Fluoro-Jade, capable of selectively staining degenerating neurons and their processes, in order to analyze degenerative effects of transecting the hippocampus from its main input, the entorhinal cortex in vivo and in organotypical hippocampal slice culture. Degenerating fibers stained with Fluoro-Jade were present as early as 1 day postlesion in the outer molecular layer of the dentate gyrus and could be detected up to 30 days postlesion. However, the intensity of the Fluoro-Jade staining in the outer molecular layer faded from postlesional day 20 onward. Punctate staining, various cells and neural processes became visible in this area suggesting that degenerating processes were phagocytosed by microglial cells or astrocytes. We conclude that Fluoro-Jade is an early and sensitive marker for studying degenerating neurites in the hippocampal system.