癫痫发病机制的研究现状

癫痫是神经系统的常见病之一,据流行病学调查,一般人群的年患病率为5‰～7‰[1],活动性癫痫患病率(5年内有发作)为4.6‰,我国估计难治性癫痫患者不少于100万。而其发病机制非常复杂,迄今未完全阐明。近年来的研究表明,癫痫疾病与离子通道、神经递质、神经胶质细胞、接触传递及缝隙连接等有密切的关系。今将其研究现状综述如下。一神经递质与离子通道多年来的研究已经证明癫痫的发病和“神经-免疫-内分泌网络”调节失衡有关[2]。癫痫的发病与兴奋性递质与抑制性递质失衡有密切的关系。研究表明在癫痫发作时,在中枢神经系统中,谷氨酸与γ-氨基丁酸(gamma-aminobutyric acid,GABA)分别作为主要的兴奋性神经递质与抑制性神经递质而与癫痫的发作有着密切的联系,它们的生成、释放、灭活及受体的异常皆可引起神经元异常、过度的同步性放电。特别是各种神经递质的促离子受体,目前已引起人们的关注。1.谷氨酸谷氨酸是脑内最重要的兴奋性递质,一直认为与癫痫的发作密切相关。Yao[3]等在戊四唑(PTZ)点燃癫痫模型中发现,随着点燃级别的进展,谷氨酸表达呈现先增加后减少的趋势,可见谷氨酸导致癫痫发作可能是由于其早期胞内合成增加,后...     

S100B与癫痫

S1OOB主要是由星型胶质细胞和少突胶质细胞合成和分泌的一种酸性钙结合蛋白,主要存在于脑中,目前的研究认为:一方面S1OOB是神经胶质细胞损伤的标志物;癫痫发作后脑组织的病理研究表明胶质细胞会发生一系列变化(包括坏死、激活、增生等),体液中的S1OOB能否作为癫痫患者胶质细胞这种变化的标志物目前尚无定论;另一方面其作为一种钙结合蛋白参与ca2 介导的信号传递途径,Ca2 在癫痫的发病中具有重要的作用,现有文献报道S1OOB与癫痫的发作有关.     

高糖对缺氧神经元的影响及钙相关机制研究

研究高糖对神经元缺氧的影响 ,并探讨其钙相关机制。利用 SD大鼠大脑皮质神经元体外缺氧模型 ,通过对细胞活力的检测 ,观察浓度分别为 2 2 .7(对照组 ) ,30 ,40 ,50 ,60 (高糖组 ) mmol/ L的葡萄糖对神经元缺氧的影响 ;以 Fura- 2 / Am为荧光指示剂 ,测定细胞内游离钙离子浓度 ([Ca2 ]i。结果发现当培养基中葡萄糖浓度达到 60 mmol/ L时 ,高糖可引起缺氧神经元损伤 ;与对照组相比 ,有钙介质与无钙介质中静息[Ca2 ]i 均升高 ,P<0 .0 1 ;但对照组与高糖组在有钙介质中对氯化钾 (KCl)、谷氨酸 (Glu)刺激引起的[Ca2 ]i 升高无明显差异 ,P>0 .0 5;在无钙介质中 ,对氯化钙 (Ca Cl2 )引起的 [Ca2 ]i 增高率无明显差别 ,P>0 .0 5。本研究表明 :高糖对神经元的损伤作用可能与其促进细胞内钙离子释放 ,诱发细胞内钙超载有关     

少突胶质细胞的钙信号

钙是细胞内重要的第二信使,参与机体内多种生理过程,其胞内的钙信号传递依赖于胞内外的钙离子(Ca2+)浓度差,表现为胞质内钙的变化.Ca2+进入细胞内与钙的受体如钙调素(calmodulin,CaM)结合后发挥系列效应.以往认为Ca2+仅在兴奋性细胞中起传递信号作用,但近年来随着研究的深入,发现无论是兴奋性还是非兴奋性细胞,钙都作为第二信使参与信号转导及基因的表达调控.少突胶质细胞是中枢神经系统髓鞘形成细胞,被认为是中枢神经系统中一种非兴奋性细胞,其对于细胞外的刺激可表现为胞内钙浓度的变化从而调控细胞活动.     

抑制Na+内流与神经保护作用

颅脑外伤或脑缺血缺氧时,一系列继发性的病理生化机制将导致细胞内Na+急剧升高,而Na+的内流被认为是继发性脑损害的始动因素之一,可通过多种机制使细胞内Ca2+增加,继而促发了一系列最终导致细胞死亡的级联反应.一些Na+通道阻滞剂已被初步证明具有一定的神经保护作用,而一些具有抑制谷氨酸转运蛋白,或抑制Na+/H+交换的新型化合物也显示出较强的抑制Na+内流的作用,但抑制Na+内流与神经保护作用之间的关系及其临床意义仍有待于大量的研究证明.     

DHA介导GPR40转染PC12细胞内的钙离子动员

目的 构建GPR40基因质粒转染PC12细胞,用DHA干预后测定细胞内Ca2+浓度的变化,从而探讨DHA通过GPR40信号途径介导Ca2+上调的作用机制.方法 将PC12细胞分成4组,分别为未转染组.空载体转染组,GPR40基因-pCruz载体转染组及GPR40基因-pCruz载体转染+阻制剂Xestospongin C组;构建大鼠GPR40质粒并转染PC12细胞.采用RT-PCR和Western blot方法 从mRNA和蛋白质水平观察GPR40的表达.DHA(10 μmol/L)干预后,测定细胞内Ca2+浓度.结果 DHA干预后,未转染组和空转染组PC12细胞内Ca2+浓度没有受到明显影响;GPR40基因-pCruz载体转染组细胞内的Ca2+浓度明显增加,且这种作用不受细胞外Ca2+浓度的影响:添加阻滞剂组Ca2+浓度变化也不明显.结论 DHA能动员GPR40基因转染的PC12细胞内Ca2+浓度且这种作用完全能被IP3受体特异性阻止剂Xestospongin C所阻断,提示DHA可能通过GPR40信号途径动员细胞内Ca2+浓度并因此改善神经功能.     

鲫鱼视网膜ON型双极细胞的轴突末梢中不存在ryanodine受体门控的钙库(英文)

以前结果表明 ,ryanodine受体 (ryanodinereceptors ,RyRs)门控的咖啡因敏感的钙库和钙引钙释放(Ca2 inducedCa2 release ,CICR)机制存在于鲫鱼视网膜ON型双极细胞的胞体中[1] 。采用RyRs的免疫细胞化学方法和细胞内钙测量技术 ,我们进一步研究了RyRs门控的钙库是否存在于这些细胞的轴突末梢中。视网膜纵切和分离细胞的免疫细胞化学研究显示 ,RyRs主要位于ON型双极细胞的胞体中。咖啡因浓度升至 4 0mmol/L在轴突末梢不能诱导钙信号。在细胞外K 浓度升至 10mmol/L引起静息 [Ca2 ]i 轻微升高后 ,咖啡因在轴突末梢也不能诱导钙信号。在forskolin或多巴胺引起细胞内cAMP浓度升高 ,进而cAMP依赖的磷酸化增强后 ,咖啡因在轴突末梢仍不能诱导钙信号。此外 ,50 μmol/Lryanodine对 65mmol/LK 作用 1min或 2min诱导的轴突末梢的钙信号没有产生任何效应。这些结果表明 ,在鲫鱼视网膜ON型双极细胞的轴突末梢中不存在RyRs门控的咖啡因敏感的钙库和CICR机制     

高糖对缺氧神经元的影响及钙相关机制研究

研究高糖对神经元缺氧的影响,并探讨其钙相关机制.利用SD大鼠大脑皮质神经元体外缺氧模型,通过对细胞活力的检测,观察浓度分别为22.7(对照组),30,40,50,60(高糖组)mmol/L的葡萄糖对神经元缺氧的影响;以Fura-2/Am为荧光指示剂,测定细胞内游离钙离子浓度([Ca2+]i.结果发现当培养基中葡萄糖浓度达到60 mmol/L时,高糖可引起缺氧神经元损伤;与对照组相比,有钙介质与无钙介质中静息[Ca2+]i均升高,P＜0.01;但对照组与高糖组在有钙介质中对氯化钾(KCl)、谷氨酸(Glu)刺激引起的[Ca2+]i升高无明显差异,P＞0.05;在无钙介质中,对氯化钙(CaCl2)引起的[Ca2+]i增高率无明显差别,P＞0.05.本研究表明:高糖对神经元的损伤作用可能与其促进细胞内钙离子释放,诱发细胞内钙超载有关.     

难治性癫痫发病机制研究进展

难治性癫痫(refractory epilepsy,RE)约占癫痫患者总数的1/3 [1].虽然迄今对RE定义尚未达成共识,但一般基于治疗学指标认为,凡是序贯或联合应用至少3种抗癫痫药物(antiepileptic drugs,AEDs),给予足够或可耐受的剂量,观察足够长的疗程,发作次数并未减少或有所增加者即为RE [2].RE的发生涉及3个方面,即发作本身(包括病因、发作持续时间及发作类型等)、发作个体特征(包括年龄、遗传学因素、脑结构或网络结构变化等)以及药物作用(包括药物靶点及脑摄取改变).近年来随着遗传学研究的进步,对RE发病机制的认识逐渐深入,药物转运蛋白,离子通道及药物代谢酶正成为研究和认识RE发病机制、开发新型抗癫痫药的线索和突破点.本文拟就药物转运蛋白及其抑制剂、离子通道及药物代谢酶等方面进行综述.     

铝的神经毒性：改变神经细胞钙稳态

铝是一种具有神经毒性的金属，现在发现它与神经退行性老年性疾病有关。本研究主要目的探讨铝对神经毒性作用机制。采用动物实验方法，对实验大鼠进行经口染毒，判定铝染毒后大鼠大脑皮层细胞内钙浓度的改变，以及与钙稳态有关的基因和蛋白表达情况。结果显示铝染毒后大鼠大脑皮层内钙浓度增加，其机制可能是由于下调Cam蛋白表达，上调 Ryr2,L-Ca2+α1c和Na+/Ca2+ 交换体基因的表达而发挥神经毒性作用。所以可以认为铝可以通过改变与钙稳态有关的基因和蛋白表达，是神经细胞内钙浓度增加而发挥神经毒性作用。     

Epilepsy and anomalies of neuronal migration: MRI and clinical aspects

Neuronal migration disorders are the result of disturbed brain development. In such disorders, neurons are abnormally located. In diagnosing these conditions, magnetic resonance imaging is superior to any other imaging technique. This enables us to improve our knowledge of the clinical correlates of neuronal migration. With reference to migrational disorder, a retrospective study of all 303 patients with epileptic seizures referred for magnetic resonance imaging during a 3-year period was performed, 13 patients (aged 12-41, mean age 27) were identified. They represent 4.3% of the entire study group. Of the patients with known epilepsy, 6.7% and of the mentally retarded, 13.7% had migrational disorders. Four patients had schizencephaly as the dominant finding, one was classified as hemimegalencephaly, 2 had isolated heterotopias, and 6 had localized pachy- and/or poly-microgyria. The clinical pictures are complex. Ectopias of grey matter are recognised foci of epilepsy, but from an epileptological and a clinical viewpoint little attention has been given to these disorders. The present study shows that malmigration is not rare in epilepsy patients, especially not in the mentally retarded.     

Classification of methods in transcranial Electrical Stimulation (tES) and evolving strategy from historical approaches to contemporary innovations

Transcranial Electrical Stimulation (tES) encompasses all methods of non-invasive current application to the brain used in research and clinical practice. We present the first comprehensive and technical review, explaining the evolution of tES in both terminology and dosage over the past 100 years of research to present day. Current transcranial Pulsed Current Stimulation (tPCS) approaches such as Cranial Electrotherapy Stimulation (CES) descended from Electrosleep (ES) through Cranial Electro-stimulation Therapy (CET), Transcerebral Electrotherapy (TCET), and NeuroElectric Therapy (NET) while others like Transcutaneous Cranial Electrical Stimulation (TCES) descended from Electroanesthesia (EA) through Limoge, and Interferential Stimulation. Prior to a contemporary resurgence in interest, variations of transcranial Direct Current Stimulation were explored intermittently, including Polarizing current, Galvanic Vestibular Stimulation (GVS), and Transcranial Micropolarization. The development of these approaches alongside Electroconvulsive Therapy (ECT) and pharmacological developments are considered. Both the roots and unique features of contemporary approaches such as transcranial Alternating Current Stimulation (tACS) and transcranial Random Noise Stimulation (tRNS) are discussed. Trends and incremental developments in electrode montage and waveform spanning decades are presented leading to the present day. Commercial devices, seminal conferences, and regulatory decisions are noted. We conclude with six rules on how increasing medical and technological sophistication may now be leveraged for broader success and adoption of tES.     

Hepatic Considerations in the Use of Antiepileptic Drugs

Summary: Virtually all of the major antiepileptic drugs (AEDs) can cause hepatotoxicity, although fatal hepatic reactions are rare. The mechanisms, incidences, and risk profiles for such reactions differ from drug to drug. With carbamazepine and phenytoin, hepatotoxicity may be due to drug hypersensitivity. Although the profiles of patients at risk have not been well-defined for these two antiepileptic drugs, it would appear from reports in the literature that older adolescents and adults are at higher risk than children of developing serious or fatal hepatotoxicity. Once hepatotoxicity develops, mortality rates are 10–38% with phenytoin and 25% for carbamazepine. The risk profile for valproate fatal hepatotoxicity has been more clearly defined. Those at primary risk of fatal hepatic dysfunction are children under the age of 2 years who are receiving multiple anticonvulsants and also have significant medical problems in addition to severe epilepsy. The risk is considerably lower for patients over the age of 2 years on valproate monotherapy. In contrast to the risk profile with other AEDs, adults receiving valproate as monotherapy have the lowest risk of hepatotoxicity. Fatal hepatic dysfunction coincident with valproate may be the result of aberrant drug metabolism. Concomitant use of AEDs that induce microsomal P450 enzymes (e.g., phenytoin and phenobarbital) may enhance the production of a toxic metabolite, and hence the greater risk of hepatotoxicity with polypharmacy.     

Vascular Malformations and Epilepsy: Clinical Considerations and Basic Mechanisms

Summary: Vascular malformations (VMs) are associated with epilepsy. The natural history of the various VMs, clinical presentation, and tendency to provoke epilepsy determine treatment strategies. Investigations have probed the mechanisms of epileptogenesis associated with these lesions. Electrophysiologic changes are associated with epileptogenic cortex adjacent to VMs. Putative pathophysiologic mechanisms of epileptogenesis include neuronal cell loss, glial proliferation and abnormal glial physiology, altered neurotransmitter levels, free radical formation, and aberrant second messenger physiology.     

Neonatal Seizures: Problems in Diagnosis and Classification

Summary: The clinical identification of neonatal seizures is critical for the recognition of brain dysfunction; however, diagnosis is often difficult because of the poorly organized and varied nature of these behaviors. Current classification systems are limited in their ability to communicate motor, autonomic, and electroencephalo-graphic features of seizures precisely and to provide a basis for uniform effective diagnosis, therapy, and determination of prognosis. Recent investigations of neonates, utilizing bedside electroencephalographic/polygraphic/ video monitoring techniques, have provided the basis for improved diagnosis and classification of seizures in the newborn. These studies have demonstrated that not all clinical phenomena currently considered to be seizures require electrocortical epileptiform activity for their initiation or elaboration. In addition, the specific clinical character of the phenomena considered to be seizures, the clinical state of the infant, and the character of the EEG indicate the probable pathophysiological mechanisms involved and suggest probable etiologies, prognosis, and therapy. Similarities between animal models that demonstrate reflex physiology and neonates with motor automatisms and tonic posturing suggest that these clinical behaviors may not be epileptic in origin but, rather, primitive movements of progression and posture mediated by brainstem mechanisms. Although not all clinical behaviors currently considered to be neonatal seizures may have similar pathophysiological mechanisms, they are clinically significant because they all indicate brain dysfunction.     

Valproate Monotherapy in the Management of Generalized and Partial Seizures

Summary: For decades, therapeutic tradition has promoted the concept of polypharmacy in the management of epilepsy. In recent years, however, studies have shown that, for most patients, monotherapy can provide comparable or better seizure control than administration of multiple anticonvulsants, while diminishing the potential for adverse reactions, drug interactions, and poor compliance. Valproate is an important monotherapeutic agent that is highly effective in the control of idiopathic primary and secondarily generalized epilepsies, and partial seizures that do not generalize. Comparative studies have found that valproate is at least as effective as phenytoin and carbamazepine in the treatment of generalized and partial seizures. Given the similar efficacy, other factors such as pharmacokinetics and side effects may therefore determine anticonvulsant selection for monotherapy.     

Carbamazepine Efficacy and Utilization in Children

Summary: Carbamazepine is effective for preventing partial and generalized tonic-clonic seizures in children. Although absence epilepsies are more common in children than adults, an estimated 80% of children with epilepsy have seizure types or epilepsies that are potentially responsive to carbamazepine. The differential diagnosis of ictal staring is an especially important issue in children because absence and atypical absence seizures are more prevalent in children than adults. Age-related pharmacokinetic differences and drug interactions are major considerations in children. On average, children have higher clearance rates of carbamazepine, shorter half-lives, and higher ratios of carbamazepine-10, 11-epoxide to carbamazepine than adults. In addition, children with severe epilepsy are more likely to require multiple-drug therapy, which can lead to complex drug interactions. When carbamazepine is administered along with valproate, drug protein binding interactions can cause intermittent side effects.     

Un nouveau cadre conceptuel de travail pour la psychiatrie

In an attempt to place psychiatric thinking and the training of future psychiatrists more centrally into the context of modern biology, the author outlines the beginnings of a new intellectual framework for psychiatry that derives from current biological thinking about the relationship of mind to brain. The purpose of this framework is twofold. First, it is designed to emphasize that the professional requirements for future psychiatrists will demand a greater knowledge of the structure and functioning of the brain than is currently available in most training programs. Second, it is designed to illustrate that the unique domain which psychiatry occupies within academic medicine, the analysis of the interaction between social and biological determinants of behavior, can best be studied by also having a full understanding of the biological components of behavior.