海人酸致癫痫大鼠海马结构中noggin表达变化

目的:研究海人酸(kainic acid,KA)侧脑室注射并诱发癫痫持续状态(status epilepticus,SE)后大鼠海马结构中noggin基因在大鼠海马的表达变化。方法:大鼠在侧脑室注射KA后1、3、7、14、30和60d等不同时间,采用RT-PCR研究noggin mRNA含量变化,采用免疫组化观察noggin蛋白表达变化。结果:在正常大鼠海马结构中noggin mRNA有少量表达。noggin阳性细胞主要位于齿状回及CA3、CA1区,数量较少。侧脑室注射KA诱发SE后,noggin表达持续升高,3d达到高峰;7d在脑内的表达开始降低;注射后2个月,noggin表达降至术前水平,仅见散在的阳性细胞。结论:侧脑室注射KA并诱发SE后,大鼠海马结构中noggin表达明显增加。     

Effect of age on kainate-induced seizure severity and cell death

While the onset and extent of epilepsy increases in the aged population, the reasons for this increased incidence remain unexplored. The present study used two inbred strains of mice (C57BL/6J and FVB/NJ) to address the genetic control of age-dependent neurodegeneration by building upon previous experiments that have identified phenotypic differences in susceptibility to hippocampal seizure-induced cell death. We determined if seizure induction and seizure-induced cell death are affected differentially in young adult, mature, and aged male C57BL/6J and FVB/NJ mice administered the excitotoxin, kainic acid. Dose response testing was performed in three to four groups of male mice from each strain. Following kainate injections, mice were scored for seizure activity and brains from mice in each age group were processed for light microscopic histopathologic evaluation 7 days following kainate administration to evaluate the severity of seizure-induced brain damage. Irrespective of the dose of kainate administered or the age group examined, resistant strains of mice (C57BL/6J) continued to be resistant to seizure-induced cell death. In contrast, aged animals of the FVB/NJ strain were more vulnerable to the induction of behavioral seizures and associated neuropathology after systemic injection of kainic acid than young or middle-aged mice. Results from these studies suggest that the age-related increased susceptibility to the neurotoxic effects of seizure induction and seizure-induced injury is regulated in a strain-dependent manner, similar to previous observations in young adult mice.     

The time-dependent effect of lipopolysaccharide on kainic acid-induced neuronal death in hippocampal CA3 region: possible involvement of cytokines via glucocorticoid

It has been reported that glucocorticoid (Gc) can induce neuronal cell toxicity in the hippocampus. In addition, we examined that serum Gc increased by restraint stress aggravated kainic acid (KA)-induced neuronal death in hippocampal CA3 region. However, the effect of other stressful stimulus like lipopolysaccharide (LPS) increasing serum Gc on KA-induced neuronal death was not elucidated until now. Thus, we examined the time course effect of LPS on KA-induced neuronal death in the hippocampal CA3 region of mice, especially to address the role of Gc and inflammatory mediators. In the present study, we found that an aggravating effect of LPS on KA-induced neuronal death was correlated with an alteration of hippocampal IL-1β mRNA level at all time points, and the serum Gc and hippocampal IL-1β mRNA level was peak at 90 min after LPS treatment (LPS 90 min) when the aggravating effect of LPS on KA-induced neuronal death was maximum. In addition, RU38486 (glucocorticoid receptor antagonist) decreased the hippocampal IL-1β mRNA level and abolished the aggravating effect of LPS on KA-induced neuronal death at LPS 90 min and 24 h. In the immunohistochemical study, we found activated and ramified microglia (OX-42) and astrocyte (GFAP) at 24 h after LPS treatment (LPS 24 h) in the hippocampus. These results suggest that Gc itself, cytokines triggered by Gc, or both appears to be involved in the LPS effect depending on LPS pretreatment time.     

左乙拉西坦对红藻氨酸致发育期癫痫幼鼠海马主穹窿蛋白表达的影响

目的:建立发育期慢性癫痫大鼠模型,观察海马主穹窿蛋白(MVP)的表达及左乙拉西坦(LEV)对其表达的影响。方法:腹腔注射红藻氨酸(KA)1 mg/kg(浓度0.5 mg/ml),建立大鼠慢性癫痫模型,注射后连续观察8 h,癫痫发作达5级以上并出现癫痫持续状态的大鼠,且两周后出现自发性反复惊厥发作者视为模型成功。将造模成功后的40只大鼠随机分为未治疗组(KA组)20只,左乙拉西坦治疗组(KA+LEV组)20只,另取40只大鼠腹腔注射生理盐水,并分为NS组20只、NS+LEV组20只。用药组均于癫痫自发性反复发作后开始用药,疗程为6周,然后将所有大鼠断头取脑,用免疫组化及RT-PCR法测定大鼠海马内MVP及其mRNA的表达。结果:(1)大鼠海马MVP的阳性细胞计数与MVP的mRNA表达趋势相一致。(2)NS组、NS+LEV组大鼠海马有少量MVP阳性细胞及mRNA表达,NS+LEV组MVP阳性细胞数及mRNA的含量与NS组相比差异无统计学意义(P>0.05);KA组MVP阳性细胞计数及mRNA的含量与NS组相比显著增高(P<0.05);KA+LEV组与KA组相比,MVP的阳性细胞及mRNA含量减少(P<0.05)。结论:MVP可能参与慢性癫痫耐药的发生,LEV可以控制大鼠痫性发作,并下调MVP的表达。     

Prominent hippocampal CA3 gene expression profile in neurocognitive aging

Research in aging laboratory animals has characterized physiological and cellular alterations in medial temporal lobe structures, particularly the hippocampus, that are central to age-related memory deficits. The current study compares molecular alterations across hippocampal subregions in a rat model that closely mirrors individual differences in neurocognitive features of aging humans, including both impaired memory and preserved function. Using mRNA profiling of the CA1, CA3 and dentate gyrus subregions, we have distinguished between genes and pathways related to chronological age and those associated with impaired or preserved cognitive outcomes in healthy aged Long-Evans rats. The CA3 profile exhibited the most prominent gene expression differences related to cognitive status and of the three subregions, best distinguished preserved from impaired function among the aged animals. Within this profile differential expression of synaptic plasticity and neurodegenerative disease-related genes suggests recruitment of adaptive mechanisms to maintain function and structural integrity in aged unimpaired rats that does not occur in aged impaired animals.     

癫癎发作对大鼠海马感觉门控的影响

目的：观察癫癎发作对大鼠海马感觉门控的影响。方法：采用青霉素诱导的大鼠癫癎发作模型，将探测电极植入大鼠海马的CA1区，连续7天，记录大鼠海马的听觉诱发电位；采用条件—测试模式的双短音刺激（S1、S2），刺激间隔是500ms，观察大鼠癫癎发作前后S1和S2波的峰—峰值、潜伏期和N40的测试刺激／条件刺激（T／C）比的变化，并与对照组进行比较。结果：与生理盐水对照组相比，实验组大鼠第一天癫癎发作后S2的峰—峰值增大，差异有显著意义（P=0．043）。反复癫癎发作一周，实验组第二天以后每天癫癎发作后总的趋势是：S1的峰—峰值减小，与对照组相比差异有显著意义（P=0．01），N40的T／C比在癫癎发作后增大，差异具有显著意义（P=0．028）。结论：癫癎发作对大鼠海马感觉门控具有急性和潜在的慢性损害作用。     

Evolution of hippocampal epileptic activity during the development of hippocampal sclerosis in a mouse model of temporal lobe epilepsy

Unilateral intrahippocampal injection of kainic acid in adult mice reproduces most of the morphological characteristics of hippocampal sclerosis (neuronal loss, gliosis, reorganization of neurotransmitter receptors, mossy fiber sprouting, granule cell dispersion) observed in patients with temporal lobe epilepsy. Whereas some neuronal loss is observed immediately after the initial status epilepticus induced by kainate treatment, most reorganization processes develop progressively over a period of several weeks. The aim of this study was to characterize the evolution of seizure activity in this model and to assess its pharmacological reactivity to classical antiepileptic drugs.Intrahippocampal electroencephalographic recordings showed three distinct phases of paroxystic activity following unilateral injection of kainic acid (1 nmol in 50 nl) into the dorsal hippocampus of adult mice: (i) a non-convulsive status epilepticus, (ii) a latent phase lasting approximately 2 weeks, during which no organized activity was recorded, and (iii) a phase of chronic seizure activity with recurrent hippocampal paroxysmal discharges characterized by high amplitude sharp wave onset. These recurrent seizures were first seen about 2 weeks post-injection. They were limited to the injected area and were not observed in the cerebral cortex, contralateral hippocampus or ipsilateral amygdala. Secondary propagation to the contralateral hippocampus and to the cerebral cortex was rare. In addition hippocampal paroxysmal discharges were not responsive to acute carbamazepine, phenytoin, or valproate treatment, but could be suppressed by diazepam.Our data further validate intrahippocampal injection of kainate in mice as a model of temporal lobe epilepsy and suggest that synaptic reorganization in the lesioned hippocampus is necessary for the development of organized recurrent seizures.     

Inositol 1,4,5-triphosphate receptors and NAD(P)H mediate Ca signaling required for hypoxic preconditioning of hippocampal neurons

Exposure of neurons to a non-lethal hypoxic stress greatly reduces cell death during subsequent severe ischemia (hypoxic preconditioning, HPC). In organotypic cultures of rat hippocampus, we demonstrate that HPC requires inositol triphosphate (IP₃) receptor-dependent Ca²⁺ release from the endoplasmic reticulum (ER) triggered by increased cytosolic NAD(P)H. Ca²⁺ chelation with intracellular BAPTA, ER Ca²⁺ store depletion with thapsigargin, IP₃ receptor block with xestospongin, and RNA interference against subtype 1 of the IP₃ receptor all blunted the moderate increases in [Ca²⁺]_i (50–100 nM) required for tolerance induction. Increases in [Ca²⁺]_i during HPC and neuroprotection following HPC were not prevented with NMDA receptor block or by removing Ca²⁺ from the bathing medium. Increased NAD(P)H fluorescence in CA1 neurons during hypoxia and demonstration that NADH manipulation increases [Ca²⁺]_i in an IP₃R-dependent manner revealed a primary role of cellular redox state in liberation of Ca²⁺ from the ER. Blockade of IP₃Rs and intracellular Ca²⁺ chelation prevented phosphorylation of known HPC signaling targets, including MAPK p42/44 (ERK), protein kinase B (Akt) and CREB. We conclude that the endoplasmic reticulum, acting via redox/NADH-dependent intracellular Ca²⁺ store release, is an important mediator of the neuroprotective response to hypoxic stress.     

Deletion of puma protects hippocampal neurons in a model of severe status epilepticus

Prolonged seizures (status epilepticus) can activate apoptosis-associated signaling pathways. The extent to which such pathways contribute to cell death might depend on the insult intensity, whereby the programmed or apoptotic cell death component is reduced when seizures are more severe or protracted. We recently showed that mice lacking the pro-apoptotic Bcl-2 homology domain 3-only protein Puma (Bbc3) were potently protected against damage caused by status epilepticus. In the present study we examined whether Puma deficiency was protective when the seizure episode was more severe. Intra-amygdala microinjection of 1 μg kainic acid (KA) into C57BL/6 mice triggered status epilepticus that lasted about twice as long as with 0.3 μg KA prior to lorazepam termination. Hippocampal damage was also significantly greater in the higher-dose group. Over 80% of degenerating neurons after seizures were positive for DNA fragmentation assessed by terminal deoxynucleotidyl dUTP nick end labeling (TUNEL). Microscopic analysis of neuronal nuclear morphology in TUNEL-positive cells revealed the proportion displaying large rounded clumps of condensed chromatin was ∼50% lower in the high-dose versus low-dose KA group. Nevertheless, compared to heterozygous and wild-type mice subject to status epilepticus by high-dose KA, neuronal death was reduced by ∼50% in the hippocampus of Puma-deficient mice. These data suggest aspects of the apoptotic component of seizure-induced neuronal death are insult duration- or severity-dependent. Moreover, they provide further genetic evidence that seizure-induced neuronal death is preventable by targeting so-called apoptosis-associated signaling pathways and Puma loss likely disrupts caspase-independent or non-apoptotic seizure-induced neuronal death.     

TNFR1 mediates increased neuronal membrane EAAT3 expression after in vivo cerebral ischemic preconditioning

A short ischemic event (ischemic preconditioning) can result in subsequent resistance to severe ischemic injury (ischemic tolerance). Glutamate is released after ischemia and produces cell death. It has been described that after ischemic preconditioning, the release of glutamate is reduced. We have shown that an in vitro model of ischemic preconditioning produces upregulation of glutamate transporters which mediates brain tolerance. We have now decided to investigate whether ischemic preconditioning-induced glutamate transporter upregulation takes also place in vivo, its cellular localization and the mechanisms by which this upregulation is controlled. A period of 10 min of temporary middle cerebral artery occlusion was used as a model of ischemic preconditioning in rat. EAAT1, EAAT2 and EAAT3 glutamate transporters were found in brain from control animals. Ischemic preconditioning produced an up-regulation of EAAT2 and EAAT3 but not of EAAT1 expression. Ischemic preconditioning-induced increase in EAAT3 expression was reduced by the TNF-alpha converting enzyme inhibitor BB1101. Intracerebral administration of either anti-TNF-alpha antibody or of a TNFR1 antisense oligodeoxynucleotide also inhibited ischemic preconditioning-induced EAAT3 up-regulation. Immunohistochemical studies suggest that, whereas the expression of EAAT3 is located in both neuronal cytoplasm and plasma membrane, ischemic preconditioning-induced up-regulation of EAAT3 is mainly localized at the plasma membrane level. In summary, these results demonstrate that in vivo ischemic preconditioning increases the expression of EAAT2 and EAAT3 glutamate transporters the upregulation of the latter being at least partly mediated by TNF-alpha converting enzyme/TNF-alpha/TNFR1 pathway.     

Effect of myo-inositol on convulsions induced by pentylenetetrazole and kainic acid in rats

We studied the effect of myo-inositol on pentylenetetrazole and kainic acid-induced seizures in rats. Myo-inositol significantly reduced seizure activity. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 143, No. 1, pp. 64–66, January, 2007     

Development of a fast method for quantitative measurement of hyperpolarized 129Xe dynamics in mouse brain

A fast method has been established for the precise measurement and quantification of the dynamics of hyperpolarized (HP) xenon‐129 (¹²⁹Xe) in the mouse brain. The key technique is based on repeatedly applying radio frequency (RF) pulses and measuring the decrease of HP ¹²⁹Xe magnetization after the brain Xe concentration has reached a steady state due to continuous HP ¹²⁹Xe ventilation. The signal decrease of the ¹²⁹Xe nuclear magnetic resonance (NMR) signal was well described by a simple theoretical model. The technique made it possible to rapidly evaluate the rate constant α, which is composed of cerebral blood flow (CBF), the partition coefficient of Xe between the tissue and blood (λ_i), and the longitudinal relaxation time (T_1i) of HP ¹²⁹Xe in the brain tissue, without any effect of depolarization by RF pulses and the dynamics in the lung. The technique enabled the precise determination of α as 0.103 ± 0.018 s^‐1 (± SD, n = 5) on healthy mice. To investigate the potential of this method for detecting physiological changes in the brain of a kainic acid (KA) ‐induced mouse model of epilepsy, an attempt was made to follow the time course of α after KA injection. It was found that the α value changes characteristically with time, reflecting the change in the physiological state of the brain induced by KA injection. By measuring CBF using ¹H MRI and ¹²⁹Xe dynamics simultaneously and comparing these results, it was suggested that the reduction of T_1i, in addition to the increase of CBF due to KA‐induced epilepsy, are possible causes of the change in ¹²⁹Xe dynamics. Thus, the present method would be useful to detect a pathophysiological state in the brain and provide a novel tool for future brain study. Copyright © 2011 John Wiley & Sons, Ltd.     

Delayed administration of a potent cyclin dependent kinase and glycogen synthase kinase 3 beta inhibitor produces long-term neuroprotection in a hypoxia-ischemia model of brain injury

We compared the neuroprotective efficacy of a potent and CNS-penetrant cyclin dependent kinase (CDK) and glycogen synthase kinase 3 beta (GSK3beta) inhibitor (Compound 1) in juvenile (postnatal day 21; P21) and adult C57Bl/6 mice (postnatal day 60; P60) using a model of hypoxic-ischemic brain injury (HI). Neuronal cell counts and density measures from brain sections stained with Cresyl Violet revealed that exposure of P21 mice to 60 min of HI resulted in extensive damage to the ipsilateral cornu ammonis 1 (CA1) region of the hippocampus (40% cell loss) and striatum (30% cell loss) 7 days later. Exposure of P60 mice to 40 min of HI produced a similar pattern of cell loss. Intraperitoneal administration of Compound 1 (3 mg/kg) 1, 5 and 9 h after 60 min of HI did not reduce brain injury in P21 mice relative to vehicle controls. By contrast, in P60 mice, this treatment significantly decreased cell loss in the ipsilateral hippocampus (10% cell loss) and striatum (15% loss) relative to vehicle controls. Terminal uridine deoxynucleotidyl transferase (TUNNEL) positive cell counts and infarct volume were also substantially reduced in P60 mice treated with Compound 1. A motor coordination test performed twice weekly until 5 weeks post-HI confirmed that Compound 1 produced long lasting functional recovery. Our results indicate that Compound 1 produced long lasting neuroprotective effects in adult but not juvenile mice suggesting that inhibition of the CDKs and GSK3beta plays a distinct neuroprotective role in the juvenile and adult brain.     

急性癫痫发作后海马齿状回颗粒细胞的树突改变

目的：为探讨癫痫发作敏感性的形成机制提供形态学依据。方法：海人酸(KA)或戊四氮(PTZ)诱导大鼠短暂癫痫发作后,用高尔基染色法对海马齿状回颗粒细胞的树突形态改变进行观察,并进行图像分析。结果：癫痫大鼠齿状回颗粒细胞树突的树突总长度、树突棘密度、树突分支点数和树突野最大伸展距离等均出现改变;除KA模型外,在PTZ模型中也得到了同样的证实。结论：一次癫痫发作后7d时,海马齿状回颗粒细胞(1)出现了明显增生改变,这可能是癫痫发作敏感性的原因之一;(2)出现的树突增生可能是各类癫痫模型的普遍性的变化。     

Uncoupling of local blood flow and metabolism in the hippocampal CA3 in kainic acid-induced limbic seizure status

Limbic seizure status was induced by microinjection of kainic acid into a unilateral amygdala in rats. Two hours after kainic acid injection, distant neuronal cell damage was produced, especially in the hippocampal CA3 on the kainic acid-injected side. In order to elucidate the mechanism of this neuronal cell damage, local cerebral glucose utilization and local cerebral blood flow were studied by means of an autoradiographic method using [14C]2-deoxyglucose and [14C]iodoantipyrine during kainic acid-induced limbic seizure status. These studies were performed 2 h after kainic acid microinjection into a unilateral amygdala. Both local cerebral glucose utilization and local cerebral blood flow were remarkably increased in the limbic system, ventrobasal complex of the thalamus, septal nucleus, nucleus accumbens, caudate nucleus, substantia nigra and hypothalamus on the kainic acid-injected side. In the hippocampus, local cerebral glucose utilization increased 2.6 times control in CA1 and 4.1 times in CA3, whereas the rates of increase in local cerebral blood flow were similarly low in CA1 and CA3: 1.2 and 1.4 times control, respectively. The results demonstrated that the degree of uncoupling of local cerebral glucose utilization and local cerebral blood flow were higher in CA3 than in CA1, and also suggested that relative hypoxia occurred in CA3 in this high degree of uncoupling, resulting in pyramidal cell damage in CA3 in kainic acid-induced limbic seizure status.     

Bayk-8644致癎小鼠的行为和脑电图表现

目的：观察L型钙离子通道激动剂Bayk-8644诱导的急性癫痫小鼠模型的行为和脑电图表现。方法：将C57BL／6近交系小鼠随机分成Bayk-8644模型和藻仁氨酸（KA）模型两组，每组6只。Bayk-8644模型组于小鼠腹腔注射Bayk-8644 5mg/kg,KA模型组于小鼠腹腔注射KA 30mg/kg。观察并比较两种小鼠模型的行为和脑电图表现。结果：Bayk-8644致痫小鼠模型与常用的KA模型相比具有诱导快、成功率高等特点，同时其明显发作时脑电图上的痫样放电较KA模型明显，但其行为表现在本实验中以强直为主。结论：Bayk-8644诱导的急性癫痫小鼠模型是一种稳定而可靠的癫痫模型。     

Differences of neuronal sensitivity to amino acids and related compounds in the rat hippocampal slice

The perfusion of slices of rat hippocampus with solutions containing N-methyl-DL-aspartic acid (NMA), kainic acid, ibotenic acid or quinolinic acid produced a reduction in the size of antidromically evoked population spikes in the CA1 pyramidal cells or dentate gyrus granule cells. The relative potencies of these compounds on CA1 cells compared with granule cells were kainate 3.65, quinolinate 3.46, NMA 2.19 and ibotenate 1.50. Since the former two compounds are known to show a degree of selective toxicity towards the CA1 cells, whereas NMA and ibotenate do not, these results are consistent with the excitotoxic hypothesis that excitation and neurotoxicity are related.     

Systemic administration of kainic acid induces selective time dependent decrease in [I]insulin-like growth factor I, [I]insulin-like growth factor II and [I]insulin receptor binding sites in adult rat hippocampal formation

Administration of kainic acid evokes acute seizure in hippocampal pathways that results in a complex sequence of functional and structural alterations resembling human temporal lobe epilepsy. The structural alterations induced by kainic acid include selective loss of neurones in CA1–CA3 subfields and the hilar region of the dentate gyrus followed by sprouting and permanent reorganization of the synaptic connections of the mossy fibre pathways. Although the neuronal degeneration and process of reactive synaptogenesis have been extensively studied, at present little is known about means to prevent pathological conditions leading to kainate-induced cell death. In the present study, to address the role of insulin-like growth factors I and II, and insulin in neuronal survival as well as synaptic reorganization following kainate-induced seizure, the time course alterations of the corresponding receptors were evaluated. Additionally, using histological preparations, the temporal profile of neuronal degeneration and hypertrophy of resident astroglial cells were also studied. [¹²⁵I]Insulin-like growth factor I binding was found to be decreased transiently in almost all regions of the hippocampal formation at 12 h following treatment with kainic acid. The dentate hilar region however, exhibited protracted decreases in [¹²⁵I]insulin-like growth factor I receptor sites throughout (i.e. 30 days) the study. [¹²⁵I]Insulin-like growth factor II receptor binding sites in the hippocampal formation were found to be differentially altered following systemic administration of kainic acid. A significant decrease in [¹²⁵I]insulin-like growth factor II receptor sites was observed in CA1 subfield and the pyramidal cell layer of the Ammon's horn at all time points studied whereas the hilar region and the stratum radiatum did not exhibit alteration at any time. A kainate-induced decrease in [¹²⁵I]insulin receptor binding was noted at all time points in the molecular layer of the dentate gyrus whereas binding in CA1–CA3 subfields and discrete layers of the Ammon's horn was found to be affected only after 12 h of treatment.

These results, when analysed with reference to the observed histological changes and established neurotrophic/protective roles of insulin-like growth factors and insulin, suggest possible involvement of these growth factors in the cascade of neurotrophic events that is associated with the reorganization of the hippocampal formation observed following kainate-induced seizures.     

Mitochondrial dysfunction in CA1 hippocampal neurons of the UBE3A deficient mouse model for Angelman syndrome

Angelman syndrome (AS) is a severe neurological disorder caused by a deficiency of ubiquitin protein ligase E3A (UBE3A), but the pathophysiology of the disease remains unknown. We now report that in the brains of AS mice in which the maternal UBE3A allele is mutated (m−) and the paternal allele is potentially inactivated by imprinting (p+) (UBE3A m−\p+), the mitochondria are abnormal and exhibit a partial oxidative phosphorylation (OXPHOS) defect. Electron microscopy of the hippocampal region of the UBE3A m−\p+ mice (n = 6) reveals small, dense mitochondria with altered cristae, relative to wild-type littermates (n = 6) and reduced synaptic vesicle density. The specific activity of OXPHOS complex III is reduced in whole brain mitochondria in UBE3A m−\p+ (n = 5) mice versus wild-type littermates (n = 5). Therefore, mitochondrial dysfunction may contribute to the pathophysiology of Angelman syndrome.