NMDA受体在培养海马神经元树突树上的表面表达及定位

目的　研究NMDA受体在不同发育阶段的培养大鼠海马神经元的表面表达以及在树突结构上的定位。　方法　构建绿荧光蛋白 (GFP)标记的NMDA受体NR1a亚单位的表达载体 (GFP NR1a) ,转染原代培养 5d的大鼠海马神经元 ,用抗GFP抗体和Cy3交联的二抗染色活细胞表面的受体簇。结合青荧光蛋白 (CFP)的共表达突出神经元的结构细节 ,观察表面NMDA受体簇的分布。　结果　GFP NR1a转染的神经元能表达点状、且分布于全细胞的绿荧光NMDA受体簇 ,在成熟神经元的树突上多为表面受体簇。培养 7d和培养 17d的转染神经元树突表面的NMDA受体簇密度并无显著差异。另外 ,培养 7d的海马神经元 ,表面NMDA受体簇几乎都位于树突干上 ,而树突丝上则罕见 ;培养 2周后 ,约一半的NMDA受体簇分布于树突棘。　结论　表面NMDA受体簇的分布具有树突结构相关的特异性 ,尤其是发现在发育早期NMDA受体簇罕见于树突丝 ,却已广泛分布于树突干上 ,且密度相当于成熟神经元。提示在突触形成过程中NMDA受体可能是以预先表达于树突干表面的受体簇形式被新形成的突触所征募     

培养海马神经元突触外NMDA受体通道电流在发育中的变化

为观察培养大鼠海马神经元突触外NMDA受体通道电流在发育中的变化,本研究采用膜外面向外模式记录突触外NMDA受体介导的单通道电流。结果显示:培养2周神经元的电流幅度和开放概率比培养1周神经元大,但电导和翻转电位无显著差异。培养2周神经元只出现高电导开放,培养1周神经元同时出现高电导和低电导两种开放形式。NR2B受体亚型的特异性拮抗剂ifenprodil可降低培养1周和2周海马神经元的电流幅度、电导和开放概率,且对培养2周神经元开放概率的抑制作用更明显。以上结果表明,培养海马神经元突触外NMDA受体通道电流有发育变化,且培养1周神经元突触外NMDA受体的NR2亚型可能为NR2B和NR2D;而神经元培养到2同时,突触外主要为NR2B亚型,且数量有所增加。     

NMDA受体的NR2A和NR2B亚基在海马可塑性中的作用

脑的学习和记忆功能的实现是一个相当复杂的生理过程,一直是神经科学研究的热点问题之一。人们认为脑之所以具有将短时的经历转化为几乎无限的长期记忆的能力,是因为神经突触间的传递效率发生了活动依赖性的改变,即突触可塑性。大量研究结果证明突触可塑性的形成与NMDA受体的激     

脑兴奋性突触后NMDA受体信号转导复合物

在脑兴奋性突触中,N甲基D天(门)冬氨酸受体和各种信号蛋白在突触后形成了一个多蛋白的NMDA受体复合物,共同调控着神经信号由突触前向细胞内的传导以及在细胞内的级联释放、传递,介导突触强度的长期变化,并参与突触可塑性、学习记忆和认知等多种神经功能。NMDA受体复合物由受体、衔接蛋白、信号蛋白和骨架蛋白等上百种蛋白组成,各种蛋白在突触后形成了一个蛋白间相互作用的网络,编码神经信号,将电信号转化为生化变化,从而精密地调控着神经功能。对NRC组成和功能的研究将有助于阐明其在突触可塑性、学习记忆和认知中的作用机制。     

慢性复合应激对大鼠学习与记忆及海马 NMDA受体NR1亚基表达的影响

目的：观察慢性复合应激对大鼠学习与记忆的影响和海马内NMDA受体亚基NR1表达的变化。方法：成年雄性Wistar大鼠实验组每天交替暴露于复合应激原环境中达6w，然后作Morris水迷宫和Y迷宫作业测试，再采用免疫组织化学和图像处理方法分析海马CA1、CA3和齿状回区内NR1的表达变化。结果：慢性复合应激组大鼠寻找平台的潜伏期较对照组明显缩短，学会躲避电击的正确次数较对照组明显增多；海马内NMDA受体亚基NRI的表达水平较对照组明显上调。结论：慢性复合应激可增强学习与记忆能力，NMDA受体表达变化可能是影响学习与记忆的机制之一。     

氯胺酮对缺氧大鼠海马神经元钙激活钾通道的作用

脑缺血时细胞外兴奋性氨基酸浓度增高,增高的兴奋性氨基酸将通过N-甲基-D-天门冬氨酸(NM-DA)受体及非NMDA受体门控的离子通道导致细胞内游离Ca^2 浓度([Ca^2 ]i)增高,最终将导致神经元的损害或坏死。另一方面,脑缺血也诱导产生多种自身代偿机制,以拮抗各种病理性损伤及增加神经元的存活率。     

NMDA受体在β-淀粉样蛋白引起海马神经元突触蛋白改变中的作用

为了研究NMDA受体活性对Aβ引发的海马神经元突触蛋白表达变化的影响,本文运用免疫细胞化学方法检测不同浓度NMDA受体激动剂以及拮抗剂对Aβ诱导的海马神经元突触蛋白变化的影响。结果显示:NMDA可浓度依赖性地缓解Aβ25-35引起的突触蛋白synaptophysin与PSD-95的减少。抑制突触内NMDA受体,NMDA缓解Aβ减少突触蛋白的作用减弱;抑制突触外NMDA受体,对抗Aβ的作用无显著变化。本研究结果提示NMDA受体活性改变影响Aβ诱导的突触蛋白减少,突触内NMDA受体激活可对抗Aβ的毒性作用。突触内NMDA受体活性减弱可能在谷氨酸兴奋毒性中发挥作用。     

Dimebon对小鼠中型多棘神经元NMDA激活电流的影响

目的：探讨药物Dimebon在阿尔茨海默氏病（AD）和亨廷顿氏病（HD）的药理作用。方法采用膜片钳技术在培养的小鼠纹状体中型多棘神经元（medium spiny striatal neurons，MSN）上观察不同浓度的Dimebon对NMDA (N-methyl-D-aspartic acid)受体激活电流的影响。结果高浓度的Dimebon抑制NMDA激活电流，而低浓度的Dimebon增强NMDA激活电流,从而下调NMDA受体。结论 Dimebon对NMDA受体激活电流的影响有双重作用，依Dimebon浓度的不同而不同，为临床用药提供依据。     

神经干细胞向神经元前体细胞分化过程中NMDA受体介导的电流变化

背景：NMDA受体是脑内主要的兴奋性氨基酸谷氨酸的特异性受体,参与中枢神经系统许多重要的生理和病理过程。 目的：观察体外培养的SD大鼠海马区的神经干细胞及神经前体细胞在发育过程中NMDA受体介导的全细胞电流的变化情况。 方法：应用细胞免疫化学方法观察神经干细胞的nestin以及分化1,3,7 d 神经前体细胞的βⅢ-tubulin表达情况。应用全细胞膜片钳技术在-60 mV钳制电压下记录神经干细胞和神经前体细胞电流。将神经干细胞和神经前体细胞和分为对照组和实验组,对照组加入无Mg2+的细胞外液;实验组加入10,20,50,100 μmol/L NMDA。 结果与结论：神经干细胞的NMDA受体未检测到介导电流产生;分化1,2 d的神经元前体细胞未检测到电流;分化3,7 d的神经元前体细胞能够检测到电流,随着NMDA剂量的增加电流也在增大;分化7 d的神经元前体细胞在相同剂量的NMDA诱导产生的电流较分化3 d的产生的电流大。提示：①实验中未检测到神经干细胞的NMDA介导电流产生。②神经前体细胞第3天时检测到NMDA介导电流。 ③随着神经前体细胞分化的进展,NMDA介导电流在增大。     

NMDA受体与癫痫及学习、记忆的关系

谷氨酸为中枢神经系统中兴奋性氨基酸,其离子型受体NMDA受体与癫痫的发生、发展密切相关,并且参与长时程增强(LTP)的产生.本文重点介绍近年对NMDA受体与癫痫关系的研究进展,及与学习、记忆的关系.     

N-methyl-D-aspartate receptors in the medial septal area have a role in spatial and emotional learning in the rat

Cholinergic and GABAergic neurons in the medial septal/vertical limb of the diagonal band of Broca (MS/vDB) area project to the hippocampus and constitute the septohippocampal pathway, which has been implicated in learning and memory. There is also evidence for extrinsic and intrinsic glutamatergic neurons in the MS/vDB, which by regulating septohippocampal neurons can influence hippocampal functions. The potential role of glutamatergic N-methyl-D-aspartate (NMDA) receptors within the MS/vDB for spatial and emotional learning was studied using the water maze and step-through passive avoidance (PA) tasks, which are both hippocampal-dependent. Blockade of septal NMDA receptors by infusion of the competitive NMDA receptor antagonist D-(-)-2-amino-5-phosphonopentanoic acid (D-AP5) (0.3-5 microg/rat), infused 15 min prior to training, impaired spatial learning and memory at the 5 microg dose of D-AP5, while doses of 0.3 and 1 microg per rat had no effect. The impairment in spatial learning appears not to be caused by sensorimotor or motivational disturbances, or anxiogenic-like behavior. Thus, d-AP5-treated rats were not impaired in swim performance or visuospatial abilities and spent more time in the open arms of the elevated plus-maze. In the PA task, intraseptal D-AP5 infused 15 min before training impaired retention as examined 24 h after training. This impairment was observed already at the 0.3 microg dose, suggesting that NMDA receptors within the MS/vDB may be more important for emotional than spatial memory. In summary, the present data indicate that changes in septal glutamate transmission and NMDA receptor activity can influence activity-dependent synaptic plasticity in the hippocampus and thereby learning and memory.     

铝暴露干扰学习记忆与Ras/Raf/ERK和CREB信号分子的关系

铝是与脑组织有较大亲和力的神经毒物,可引起神经系统的慢性退行性病变。学习记忆相关脑区海马是铝蓄积于中枢神经系统的重要靶器官。铝通过对信号转导分子及相关转录因子的影响发挥神经毒性作用。Ras/Raf/ERK(Ras/ERK)信号通路与学习记忆功能密切相关。CREB则参与多种神经活动,其中包括突触可塑性和学习记忆。本文对铝暴露干扰学习记忆功能过程予以阐述并提出铝有可能影响Ras/Raf/ERK通路与CREB引发学习记忆障碍。     

Subunit- and site-specific pharmacology of the NMDA receptor channel.

N-Methyl-D-aspartate (NMDA) receptor channels play important roles in various physiological functions such as synaptic plasticity and synapse formation underlying memory, learning and formation of neural networks during development. They are also important for a variety of pathological states including acute and chronic neurological disorders, psychiatric disorders, and neuropathic pain syndromes. cDNA cloning has revealed the molecular diversity of NMDA receptor channels. The identification of multiple subunits with distinct distributions, properties and regulation, implies that NMDA receptor channels are heterogeneous in their pharmacological properties, depending on the brain region and the developmental stage. Furthermore, mutation studies have revealed a critical role for specific amino acid residues in certain subunits in determining the pharmacological properties of NMDA receptor channels. The molecular heterogeneity of NMDA receptor channels as well as their dual role in physiological and pathological functions makes it necessary to develop subunit- and site-specific drugs for precise and selective therapeutic intervention. This review summarizes from a molecular perspective the recent advances in our understanding of the pharmacological properties of NMDA receptor channels with specific references to agonists binding sites, channel pore regions, allosteric modulation sites for protons, polyamines, redox agents, Zn2+ and protein kinases, phosphatases.     

The effect of ganglioside GQ1b on the NMDA receptor signaling pathway in H19-7 cells and rat hippocampus

Gangliosides, sialic acid-containing glycosphingolipids, are related to various synaptic functions in the rat brain. Previously, we investigated the behavioral effects of the ganglioside GQ1b on learning and memory using the Y-maze and Morris water maze test. GQ1b-treated rats showed highly increased memory performance on the Y-maze and the Morris water maze test. In this study, we determined the role of GQ1b on the activation of the N-methyl-d-aspartate (NMDA) receptor signaling pathway in H19-7 rat hippocampal cells and the hippocampus of rats. After 12 h of treatment with GQ1b, the expression levels of NMDA receptor subunit 2A and 2B were increased in H19-7 cells and the hippocampus of rats. In addition, treatment of GQ1b increased the tyrosine phosphorylation of NR2B that may enhance NMDA receptor synaptic activation and enhancement of NMDA receptors. Also, following GQ1b treatment, the phosphorylation of extracellular signal-regulated kinases (ERK1/2) and protein kinase A, a cAMP activated protein kinase (PKA) increased in H19-7 cells and the hippocampus of rats. These increases resulted in an increase in the phosphorylation of cAMP response element binding protein (CREB). These results suggest that GQ1b might facilitate the activation of the NMDA receptor signaling pathway in the hippocampus of rats, an effect which is dependent on ERK1/2, PKA and CREB phosphorylation. Also, these data support our previous result that GQ1b improves the learning and memory of rats.     

Influence of diet restriction on NMDA receptor subunits and learning during aging.

This study was designed to determine if changes related to aging and diet in the mRNA expression of subunits of the NMDA receptor were associated with changes in binding to NMDA receptors and learning ability in C57Bl/6 mice. Three age groups (3, 15, and 26-27 months old) and 2 diet groups (ad libitum-fed and diet restricted) were used. The old ad libitum-fed mice had significantly poorer performance in a spatial reference memory task than all other groups. Diet restriction slightly spared glutamate binding to NMDA sites and improved zeta1, but not epsilon2, mRNA expression. Significant correlations were found between NMDA-displaceable [(3)H]glutamate binding and both learning ability and epsilon2 and epsilon1 mRNA density in several brain regions. Learning ability in the old mice also correlated with the ratios of mRNA expression for epsilon1 and epsilon2 and/or zeta1 subunits in the parietal cortex and CA1 region of the hippocampus. This suggests that it is the relationship between subunit expression levels that is important for maintaining memory functions in older animals.     

Memory consolidation induces N-methyl-D-aspartic acid-receptor- and Ca2+/calmodulin-dependent protein kinase II-dependent modifications in alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor properties

The N-methyl-D-aspartic acid (NMDA) receptor-dependent activation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) is necessary for induction of the long-term potentiation of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor-mediated responses in the CA1 region of the hippocampus, a putative model for learning and memory. We analyzed the interplay among NMDA receptor, CaMKII and AMPA receptor during consolidation of the memory for an inhibitory avoidance learning task in the rat. Bilateral intra-CA1 infusion of the NMDA receptor antagonist D-(-)-2-amino-5-phosphonopentanoic acid (AP5) or of the CaMKII inhibitor 2-[N-(2-hydroxyethyl)]-N-(4-methoxybenzenesulfonyl)] amino-N-(4-chlorocinnamyl)-N-methylbenzylamine) (KN-93) immediately after step-down inhibitory avoidance training hindered memory consolidation. Learning of the avoidance response induced the NMDA receptor-dependent translocation of alphaCaMKII to a postsynaptic density-enriched fraction isolated from dorsal CA1 and the autophosphorylation of this kinase at Thr-286. Step-down inhibitory avoidance training increased the quantity of GluR1 and GluR2/3 AMPA receptor subunits and the phosphorylation of GluR1 at Ser-831 but not at Ser-845 in CA1 postsynaptic densities. The intra-CA1 infusion of KN-93 and AP5 blocked the increases in GluR1 and GluR2/3 levels and the phosphorylation of GluR1 brought on by step-down inhibitory avoidance training. Our data suggest that step-down inhibitory avoidance learning promotes the learning-specific and NMDA receptor-dependent activation of CaMKII in the CA1 region of the dorsal hippocampus and that this activation is necessary for phosphorylation and translocation of AMPA receptor to the postsynaptic densities, similarly to what happens during long-term potentiation.     

Differential contribution of NMDA receptors in hippocampal subregions to spatial working memory.

N-methyl-D-aspartate (NMDA) receptor-dependent synaptic plasticity in the mammalian hippocampus is essential for learning and memory. Although computational models and anatomical studies have emphasized functional differences among hippocampal subregions, subregional specificity of NMDA receptor function is largely unknown. Here we present evidence that NMDA receptors in CA3 are required in a situation in which spatial representation needs to be reorganized, whereas the NMDA receptors in CA1 and/or the dentate gyrus are more involved in acquiring memory that needs to be retrieved after a delay period exceeding a short-term range. Our data, with data from CA1-specific knockout mice, suggest the possibility of heterogeneous mnemonic function of NMDA receptors in different subregions of the hippocampus.     

Growth hormone replacement in hypophysectomized rats affects spatial performance and hippocampal levels of NMDA receptor subunit and PSD-95 gene transcript levels

Clinical studies have demonstrated that growth hormone (GH) promotes learning and memory processes in GH-deficient (GHD) patients. In animal studies, GH also influences the N-methyl-D-aspartate (NMDA) receptor system in the hippocampus, an essential component of long-term potentiation (LTP), which is highly involved in memory acquisition. This study was designed to examine the beneficial effects of recombinant human GH (rhGH) on cognitive function in male rats with multiple hormone deficiencies resulting from hypophysectomy (Hx). The performance of an rhGH-treated group and an untreated control group was appraised in the Morris water maze (MWM). The rhGH-treated group performed significantly better in the spatial memory task than the control animals on the second and third trial days. Further training eliminated this difference between the groups. Hippocampal mRNA expression of the NMDA subunits NR1, NR2A and NR2B, insulin-like growth factor type 1 receptor (IGF-1R), and postsynaptic density protein-95 (PSD-95) was then measured in the animals by Northern blot analysis. The results suggest that there may be a relationship between the NMDA receptor subunit mRNA expression levels and learning ability, and that learning is improved by rhGH in Hx rats. Furthermore, a link between MWM performance and PSD-95 was also suggested by this study.     

Sulindac improves memory and increases NMDA receptor subunits in aged Fischer 344 rats

Inflammatory processes in the central nervous system are thought to contribute to Alzheimer's disease (AD). Chronic administration of nonsteroidal anti-inflammatory drugs (NSAIDs) decreases the incidence of Alzheimer's disease. There are very few studies, however, on the cognitive impact of chronic NSAID administration. The N-methyl-d-aspartate (NMDA) receptor is implicated in learning and memory, and age-related decreases in the NMDA NR2B subunit correlate with memory deficits. Sulindac, an NSAID that is a nonselective cyclooxygenase (COX) inhibitor was chronically administered to aged Fischer 344 rats for 2 months. Sulindac, but not its non-COX active metabolite, attenuated age-related deficits in learning and memory as assessed in the radial arm water maze and contextual fear conditioning tasks. Sulindac treatment also attenuated an age-related decrease in the NR1 and NR2B NMDA receptor subunits and prevented an age-related increase in the pro-inflammatory cytokine, interleukin 1beta (IL-1beta), in the hippocampus. These findings support the inflammation hypothesis of aging and have important implications for potential cognitive enhancing effects of NSAIDs in the elderly.     

NMDA受体在癫痫发病机制中的作用

癫痫是慢性反复发作短暂脑功能失调综合征,是神经科常见疾病之一。目前有关癫痫的发病机制尚未阐明。研究表明,癫痫的发生与兴奋性神经递质和抑制性神经递质的失衡有关。谷氨酸作为一种主要的兴奋性神经递质,通过受体介导的兴奋性机制在癫痫的发生过程中具有重要作用。谷氨酸受体可以分为促离子型和促代谢型2类。