匹罗卡品致痫诱发大鼠齿状回颗粒细胞GAP-43 mRNA表达

目的 研究边缘系统癫痫发作后海马颗粒细胞生长相关蛋白（GAP-43）基因表达变化。方法 建立匹罗卡品急、慢性癫痫模型,用原位杂交方法定量检测不同时间点海马颗粒细胞GAP-43mRNA表达。结果 对照组颗粒细胞几乎不表达GAP-43mRNA,匹罗卡品致病后6～12h颗粒细胞表达GAP-43mRNA增高,15～30d呈现第2次高峰。结论 成年大脑海马颗粒细胞在致痫后发生可塑性变化,GAP-43mRNA表达是癫痫大鼠大脑结构性重组（颗粒细胞苔藓纤维出芽）的重要分子机制。     

氯化锂-匹罗卡品致(疒间)大鼠脑髓鞘转录因子的表达及其意义

目的探讨氯化锂-匹罗卡品致疒间大鼠脑髓鞘转录因子1(MyT1)的表达及其意义.方法给SD大鼠先后腹腔注射氯化锂、匹罗卡品,制成癫疒间动物模型;用免疫荧光组化法检测癫疒间大鼠癫疒间发作后不同时间大脑皮质和海马CA1区MyT1阳性细胞数.结果与对照组相比,癫疒间后1 d组大鼠海马CA1区MyT1阳性细胞数显著减少(P＜0.05),癫疒间后其他各时间组大鼠脑皮质和海马CA1区MyT1阳性细胞数均有明显的增加,其中癫疒间后7 d组MyT1阳性细胞数最多(P＜0.01,P＜0.05).结论氯化锂-匹罗卡品致疒间大鼠早期大脑MyT1表达增加,并有时程性变化.     

颞叶癫癎大鼠海马TrkB mRNA及其蛋白表达的动态变化

目的探讨颞叶癫瘸发作大鼠海马TrkB mRNA及其蛋白表达的动态变化特征.方法建立匹罗卡品(PILO)颞叶癫癎大鼠模型,应用原位杂交及免疫组织化学方法分别检测致瘸大鼠海马齿状回、CA3区及CAi区TrkB mRNA及其蛋白质表达的变化.结果 PILO致瘸后3～6 h,海马齿状回颗粒细胞层、CA1、CA3区锥体细胞层TrkBmRNA表达显著增高(P＜0.01),稍后TrkB蛋白表达也随之增高.第7～30d,TrkBmRNA及其蛋白在齿状回、CA3区呈现第二次表达增强.结论在癫癎发作早期,TrkB表达增强,提示其可能参与急性癜癎状态的发生;后期表达增强则可能参与了海马的可塑性反应而与慢性自发性发作形成有关.     

颞叶癫痫大鼠海马TrkB mRNA及其蛋白表达的动态变化

目的 探讨颞叶癫痫发作大鼠海马TrkB mRNA及其蛋白表达的动态变化特征。方法 建立匹罗卡品(PILO)颞叶癫痢大鼠模型,应用原位杂交及免疫组织化学方法分别检测致(?)大鼠海马齿状回、CA3区及CA1区TrkB nRNA及其蛋白质表达的变化。结果 PILO致(?)后3～6 h,海马齿状回颗粒细胞层、CA1、CA3区锥体细胞层TrkB mRNA表达显著增高(P<0.01),稍后TrkB蛋白表达也随之增高。第7-30 d,TrkB mRNA及其蛋白在齿状回、CA3区呈现第二次表达增强。结论在癫(?)发作早期,TrkB表达增强,提示其可能参与急性癫痫状态的发生;后期表达增强则可能参与了海马的可塑性反应而与慢性自发性发作形成有关。     

匹罗卡品癫痫大鼠海马TrkB受体表达与苔藓纤维突触重建的关系

目的 探讨匹罗卡品诱导慢性癫痫大鼠海马齿状颗粒细胞苔藓纤维突触重建与神经营养素受体TrkB表达的关系。方法 取匹罗卡品诱导大鼠急性癫痫持续状态及慢性自发性颞叶癫痫发作期大鼠脑片，用免疫组织化学方法检测TrkB及突触体素(P38，一种突触形成标志物)在大鼠海马的表达。结果 急性癫痫持续状态诱导颗粒细胞表达TrkB一过性增高，第2次表达高峰呈现在7～30d；P38免疫反应性在齿状回内分子层则呈进行性增加，与neo-Timm显示的异常苔藓纤维出芽相一致。结论 TrkB受体激活有助于海马齿状回苔藓纤维轴突生长及突触形成从而有利于颞叶癫痫的发生。     

匹罗卡品致痫大鼠海马一氧化氮水平和caspase-3 mRNA表达的动态变化

目的探讨大鼠癫(疒间)持续状态(SE)后海马一氧化氮(NO)与caspase-3 mRNA表达的改变及相互关系.方法采用匹罗卡品腹腔注射建立大鼠SE模型,用比色法和逆转录-聚合酶链反应(RT-PCR)技术在不同时相点检测大鼠海马NO水平与caspase-3 mRNA的表达.结果大鼠海马NO含量在SE后6 h迅速升高,48～72 h虽有所降低,但仍明显高于对照组(均P<0.01);SE后7 d,海马NO含量仍高于正常,但差异无显著性.大鼠海马caspase-3 mRNA表达于SE后6 h开始增多(P<0.05),SE后48 h达到高峰(P<0.01),72 h开始降低,SE后7 d,caspase-3 mRNA表达仍高于对照组,但差异无显著性(P>0.05).结论 caspase-3 mRNA表达升高在NO水平升高之后,并与NO保持相似的变化趋势,提示SE后caspase-3的激活可能与NO神经毒性作用有关.     

颞叶癫大鼠海马轴突导向分子Sema3F及其受体Np2表达的变化

目的 研究颞叶癫(癎)大鼠海马轴突导向分子Sema3F及其受体Np2表达的变化.方法 给SD大鼠腹腔注射匹罗卡品、氯化锂制作颞叶癫(癎)模型.用免疫组化法和原位杂交技术对致(癎)后不同时间点大鼠海马CA1区、CA3区、齿状回的Sema3F mRNA、Np2 mRNA和蛋白表达进行检测,并与正常对照组比较.结果 颞叶癫(癎)大鼠致(癎)后7 d、15 d,海马CA1区、CA3区Sema3F mRNA、Np2 mRNA和蛋白的表达明显低于正常对照组(P＜0.05～0.01), 致(癎)后30 d、60 d表达与正常对照组差异无统计学意义;而齿状回Sema3F mRNA、Np2 mRNA和蛋白的表达与正常对照组的差异无统计学意义.结论 颞叶癫(癎)大鼠海马CA1区、CA3区Sema3F、Np2表达在致(癎)后早期明显下调,而在慢性期恢复正常.     

癫大鼠海马区囊泡锚定蛋白Ⅰ的表达及突触超微结构的改变

目的观察大鼠癫发作后海马区囊泡锚定蛋白Ⅰ(synapsinⅠ)的表达和突触超微结构的变化,探讨突触功能、形态可塑性与癫的关系。方法用锂匹罗卡品制作癫疒间大鼠模型,应用免疫组化法观察致疒间后急性期、静止期和慢性期synapsinⅠ在海马的表达;应用电镜和图像处理软件观察海马突触超微结构。结果癫疒间组大鼠海马区synapsinⅠ的表达于致疒间后3h减弱;6h和12h达高峰,与对照组比较差异有显著性(P<0.05～0.01);24h恢复正常并持续到60d。致疒间后3h突触后致密物质厚度(PSD)和突触数密度(Nv)无显著改变;6hPSD增高,Nv降低;7d、30dPSD恢复正常,Nv增高。结论synapsinⅠ的高表达和PSD的增高可能与急性期癫疒间持续状态的维持有关;synapsinⅠ的正常表达和PSD的正常可能是静止期内癫疒间不发作的原因之一;慢性期Nv的增加是自发性发作出现的物质基础。     

颞叶癫(癎)大鼠海马轴突导向分子Sema3F及其受体Np2表达的变化

目的研究颞叶癫大鼠海马轴突导向分子Sema3F及其受体Np2表达的变化。方法给SD大鼠腹腔注射匹罗卡品、氯化锂制作颞叶癫模型。用免疫组化法和原位杂交技术对致后不同时间点大鼠海马CA1区、CA3区、齿状回的Sema3F mRNA、Np2 mRNA和蛋白表达进行检测,并与正常对照组比较。结果颞叶癫大鼠致后7d、15d,海马CA1区、CA3区Sema3F mRNA、Np2 mRNA和蛋白的表达明显低于正常对照组(P<0.05~0.01),致后30d、60d表达与正常对照组差异无统计学意义;而齿状回Sema3F mRNA、Np2 mRNA和蛋白的表达与正常对照组的差异无统计学意义。结论颞叶癫大鼠海马CA1区、CA3区Se-ma3F、Np2表达在致后早期明显下调,而在慢性期恢复正常。     

颞叶癫(癎)大鼠海马区NCX3 mRNA和蛋白的表达变化

目的:动态观察钠-钙交换体(NCX)mRNA和蛋白在氯化锂-匹罗卡品致(癎)模型大鼠海马CA1、CA3及齿状回区表达的变化,探讨其在癫(癎)发生发展中的作用.方法:用氯化锂-匹罗卡品制备癫(癎)动物模型;应用原位杂交和免疫组化技术检测各时间点NCX3 mRNA和蛋白的表达.结果:急性期(6～24 h)海马各区NCX3 mRNA表达均随时间的延长逐渐减少;进入静止期各区表达趋向回升,慢性反复自发发作期(30、60 d)各区表达又出现不同程度的两次下调.除致(癎)后6 h大鼠海马各区的NCX3蛋白表达无明显变化外,NCX3蛋白变化趋势与NCX3 mRNA基本一致.结论:NCX3表达下调可能通过增加神经元钙超载,改变海马神经元的兴奋性,促使癫(癎)发生.     

GAP-43 mRNA and protein expression in the hippocampal and parahippocampal region during the course of epileptogenesis in rats

In order to reveal axonal rewiring in the hippocampal and parahippocampal regions after status epilepticus, we investigated the temporal evolution of growth-associated protein-43 (GAP-43) mRNA and protein expression in two rat models of mesial temporal lobe epilepsy (MTLE). Status epilepticus (SE) was induced by electrical stimulation of the angular bundle or by intraperitoneal kainic acid (KA) injections. Despite increased GAP-43 mRNA expression in dentate granule cells at 24 h after SE, GAP-43 protein expression in the inner molecular layer (IML) of the dentate gyrus decreased progressively after 24 h after SE in both models. Nevertheless robust mossy fiber sprouting (MFS) was evident in the IML of chronic epileptic rats. Remaining GAP-43 protein expression in the IML in chronic epileptic rats did not correlate with the extent of MFS, but with the number of surviving hilar neurons. In the parahippocampal region, GAP-43 mRNA expression was decreased in layer III of the medial entorhinal area (MEAIII) in parallel with extensive neuronal loss in this layer. There was a tendency of GAP-43 mRNA up-regulation in the presubiculum, a region that projects to MEAIII. With regard to this parahippocampal region, however, changes in GAP-43 mRNA expression were not followed by protein changes. The presence of the presynaptic protein GAP-43 in a neurodegenerated MEAIII indicates that fibers still project to this layer. Whether reorganization of fibers has occurred in this region after SE needs to be investigated with tools other than GAP-43.     

Expression of GAP-43 in the Granule Cells of Rat Hippocampus After Seizure-induced Sprouting of Mossy Fibres: In Situ Hybridization and Immunocytochemical Studies

The axonal growth-associated protein GAP-43 is believed to play some role in the synaptic remodelling that takes place in the hippocampus of adult rats after certain experimental lesions. GAP-43 mRNA is highly expressed in adult CA3 pyramidal cells but almost absent in the dentate granule cells. We analysed whether the sprouting of granule cell axons, the mossy fibres of the hippocampus, caused by kainic acid-induced seizures in adult rats was associated with any induction of GAP-43 mRNA in granule cells and with any changes in the immunostaining pattern of GAP-43 in the hippocampus. Increased GAP-43 mRNA expression was found to be induced in granule cells 18, 24 and 30 h after a systemic injection of kainic acid which induced generalized seizures in adult rats, and returned to control levels by 48 h post-treatment. No effect was observed in other regions of the hippocampus. However, when kainic acid was injected into 15-day-old rats, which responded with generalized seizures but no sprouting of mossy fibres, there was no induction of GAP-43 mRNA in the granule cells, suggesting a close relation between GAP-43 expression and sprouting of these cells. Seven days after kainic acid injections, GAP-43 immunostaining was decreased in the inner molecular layer of the dentate gyrus except for a thin supragranular band, whereas 30 days after treatment all animals showed increased GAP-43 immunoreactivity in the whole inner molecular layer. Since collaterals of mossy fibres grow in the inner molecular layer after kainic acid-induced seizures, these results support the theory that GAP-43 plays a role in synaptic remodelling in the adult central nervous system.     

Delayed kindling development after rapidly recurring seizures: relation to mossy fiber sprouting and neurotrophin, GAP-43 and dynorphin gene expression

Development of kindling and mossy fiber sprouting, and changes of gene expression were studied after 40 seizures produced during about 3 h by electrical stimulation every 5 min in the ventral hippocampus. As assessed by 5 test stimulations, enhanced responsiveness was present already after 6–24 h but from 1 week post-seizure increased gradually up to 4 weeks without additional stimuli. Sprouting of mossy fibers in the dentate gyrus was demonstrated only at 4 weeks with Timm's staining. In situ hybridization showed a transient increase (maximum at 2 h) of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), TrkB and TrkC mRNA levels and reduction (maximum at 12–24 h) of neurotrophin-3 (NT-3) mRNA expression in dentate granule cells after the seizures. In addition, BDNF mRNA levels were elevated in CAI and CA3 regions, amygdala and piriform cortex. Marked increases of mRNA for growth-associated protein (GAP-43), with maximum expression at 12–24 h, were observed in dentate granule cells and in amygdala-piri-form cortex. Dynorphin mRNA levels showed biphasic changes in dentate granule cells with an increase at 2 h followed by a decrease at 24 h. No long-term alterations of gene expression were observed. These findings indicate that increased responsiveness develops rapidly after recurring seizures but that the kindled state is reached gradually in about 4 weeks. Mossy fiber sprouting occurs in parallel to epileptogenesis and may play a causative role. Short-term changes of neurotrophin and Trk, GAP-43 and dynorphin mRNA levels and the assumed alterations of the corresponding proteins could trigger structural rearrangements underlying kindling but might also contribute to the initial increase of seizure susceptibility.     

Rapid induction by kainic acid of both axonal growth and F1/GAP-43 protein in the adult rat hippocampal granule cells

Hippocampal granule cells do not normally express the axonal growth and plasticity-associated protein F1/GAP-43 in the adult rat. Using three different methods that lead to hypersynchronous activity in limbic circuits, expression of F1/GAP-43 mRNA can be induced in granule cells which is followed by sprouting in mossy fibers, the axons of granule cells. F1/GAP-43 mRNA expression in granule cells was induced in the temporal, but not septal, hippocampus beginning at 12 hours after kainic acid (KA) subcutaneous injection (10 mg/kg). Beginning 2 days after KA treatment, mossy fiber sprouts restricted to the temporal hippocampus were observed in the supragranular layer. In the same animal we also observed that levels of protein F1/GAP-43 immunoreactivity in this layer apparently increased at this same 2 day time point and same ventral hippocampal location. F1/GAP-43 protein levels and mossy fiber sprouting showed an increase up to 10 days after KA treatment. Sprouting was at a maximum at 40 days, the longest time point studied. These events parallel axonal regeneration with one critical difference: granule cell axons are not damaged by kainate. The rapid onset of axonal growth in the adult is striking and occurs earlier than reported previously (2 days vs. 12 days). Such growth closely associated with elevated levels of protein F1/GAP-43 may occur as a result of a) reactive synaptogenesis caused by the availability of post-synaptic surface on granule cell dendrites at the supragranular layer, b) Hebbian co-activation of the post-synaptic granule cells and their presynaptic afferents, and c) loss of target-derived inhibitory growth factor. © 1996 Wiley-Liss, Inc.     

Transient downregulation of Sema3A mRNA in a rat model for temporal lobe epilepsy. A novel molecular event potentially contributing to mossy fiber sprouting

Mossy fiber sprouting (MFS) in the hippocampal dentate gyrus is thought to play a critical role in the hyperexcitability of the hippocampus in temporal lobe epilepsy patients. The composition of molecular signals that is needed to direct this sprouting response has not yet been elucidated to a great extent. In the present study we investigated the expression profile of Sema3A mRNA and the axonal growth-associated protein GAP-43 mRNA during the process of electrically induced epileptogenesis in rats. Sema3A is an axon guidance molecule with repellent activity on dentate granule cell axons. It is produced by neurons in the entorhinal cortex, which synapse on the dendrites of dentate granule cells. Upregulation of GAP-43 expression in granule cells has often been reported in conjunction with MFS. After induction of status epilepticus, the expression of Sema3A mRNA was temporarily downregulated in the entorhinal cortex concomitantly with an upregulation of GAP-43 mRNA in dentate granule cells. In the following days, robust MFS into the dentate molecular layer was observed. When the induction of status epilepticus was incomplete the two responses appeared to dissociate, i.e., the downregulation of Sema3A mRNA did not occur, while upregulation of GAP-43 mRNA in dentate granule cells was still displayed. However, in these rats no significant MFS was observed. These findings indicate that Sema3A mRNA downregulation is temporarily correlated with MFS, while GAP-43 upregulation per se is not, and suggest that a loss of Sema3A in the molecular layer of the dentate gyrus could facilitate MFS into this area during epilepsy.     

Circuit Mechanisms of Seizures in the Pilocarpine Model of Chronic Epilepsy: Cell Loss and Mossy Fiber Sprouting

We used the pilocarpine model of chronic spontaneous recurrent seizures to evaluate the time course of supragranular dentate sprouting and to assess the relation between several changes that occur in epilep tic tissue with different behavioral manifestations of this experimental model of temporal lobe epilepsy. Pilo carpine-induced status epilepticus (SE) invariably led to cell loss in the hilus of the dentate gyrus (DG) and to spontaneous recurrent seizures. Cell loss was often also noted in the DG and in hippocampal subfields CA1 and CA3. The seizures began to appear at a mean of 15 days after SE induction (silent period), recurred at variable frequencies for each animal, and lasted for as long as the animals were allowed to survive (325 days). The granule cell layer of the DG was dispersed in epileptic animals, and neo-Timm stains showed supra-and intragranular mossy fiber sprouting. Supragranular mossy fiber sprout ing and dentate granule cell dispersion began to appear early after SE (as early as 4 and 9 days, respectively) and reached a plateau by 100 days. Animals with a greater degree of cell loss in hippocampal field CAS showed later onset of chronic epilepsy (r= 0.83, p < 0.0005), suggest ing that CA3 represents one of the routes for seizure spread. These results demonstrate that the pilocarpine model of chronic seizures replicates several of the fea tures of human temporal lobe epilepsy (hippocampal cell loss, suprar and intragranular mossy fiber sprouting, den tate granule cell dispersion, spontaneous recurrent sei zures) and that it may be a useful model for studying this human condition. The results also suggest that even though a certain amount of cell loss in specific areas may be essential for chronic seizures to occur, excessive cell loss may hinder epileptogenesis.     

红藻氨酸致颞叶癫(癎)大鼠脑内Semaphorin3A、Semaphorin4C基因表达的研究

目的研究轴索导向分子Semaphorin3A(Sema3A)、4C(Sema4C)对癫大鼠海马苔藓纤维重建的调控作用及对皮层神经元的保护作用。方法大鼠侧脑室内注射红藻氨酸制备颞叶癫模型,原位杂交法检测致痫间后1d,1、2、3、4周大鼠脑内Sema3A/Sema4C mRNA表达。结果致痫间后1周Sema3A、Sema4CmRNA分别在齿状回(DG),CA3区表达明显下降(P<0.01),持续至3、4周时恢复至正常(P>0.05);致痫间后1d Sema3A mRNA在皮层表达明显下降(P<0.01),持续至1、2周后恢复至正常(P>0.05)。结论红藻氨酸致痫间后DG及CA3区神经元分别下调Sema3A/Sema4C mRNA的表达,促进癫大鼠苔藓纤维重建;皮层神经元通过下调Sema3A mRNA的表达来维持自身存活。     

Effects of vigabatrin treatment on status epilepticus-induced neuronal damage and mossy fiber sprouting in the rat hippocampus

Selective neuronal damage and mossy fiber sprouting may underlie epileptogenesis and spontaneous seizure generation in the epileptic hippocampus. It may be beneficial to prevent their development after cerebral insults that are known to be associated with a high risk of epilepsy later in life in humans. In the present study, we investigated whether chronic treatment with an anticonvulsant, vigabatrin (gamma-vinyl GABA), would prevent the damage to hilar neurons and the development of mossy fiber sprouting. Vigabatrin treatment was started either 1 h, or 2 or 7 days after the beginning of kainic acid-induced (9 mg/kg, i.p.) status epilepticus and continued via subcutaneous osmotic minipumps for 2 months (75 mg/kg per day). Thereafter, rats were perfused for histological analyses. One series of horizontal sections was stained with thionine to estimate the total number of hilar neurons by unbiased stereology. One series was prepared for somatostatin immunohistochemistry and another for Timm histochemistry to detect mossy fiber sprouting. Our data show that vigabatrin treatment did not prevent the decrease in the total number of hilar cells, nor the decrease in hilar somatostatin-immunoreactive (SOM-ir) neurons when SOM-ir neuronal numbers were averaged from all septotemporal levels. However, when vigabatrin was administered 2 days after the onset of status epilepticus, we found a mild neuroprotective effect on SOM-ir neurons in the septal end of the hippocampus (92% SOM-ir neurons remaining; P < 0.05 compared to the vehicle group). Vigabatrin did not prevent mossy fiber sprouting regardless of when treatment was started. Rather, sprouting actually increased in the septal end of the hippocampus when vigabatrin treatment began 1 h after the onset of status epilepticus (P < 0.05 compared to the vehicle group). Our data show that chronic elevation of brain GABA levels after status epilepticus does not have any substantial effects on neuronal loss or mossy fiber sprouting in the rat hippocampus.