糖尿病大鼠视网膜N-甲基-D-天门冬氨酸受体表达的变化

目的:观察糖尿病不同时期视网膜 N-甲基-D-天门冬氨酸(NMDA)受体各亚基的表达.方法:采用雄性 SD 大鼠腹腔内注射链脲佐菌素建立糖尿病大鼠模型,分别于4、8、12周灌注,取眼球、冷冻切片;免疫组织化学、原位杂交方法检测NMDA 受体 NRl、NR2A、NR2B 亚基表达的变化;用 RS IMAGE 软件进行图像分析.结果:NRl、NR2A、NR2B 基因及其蛋白表达在糖尿病第 4 周时开始升高,至12周升高具有统计学意义,特别是 NRl 的变化更为显著.结论:NMDA 受体各亚基的高表达参与了糖尿病视网膜病变.     

癫痫发作敏感大鼠T区κ型阿片受体和NR_(2B)表达变化

为探讨前深梨状皮层T区(AT)κ型阿片受体与N-甲基-D-天门冬氨酸受体2B亚型(NR2B)表达在红藻氨酸(KA)诱导的癫痫发作敏感性长期增强中的作用。本研究采用颗叶癫痫(KA)模型,制备癫痫发作敏感大鼠,以免疫组化方法检测前深梨状皮层T区κ型阿片受体与NR2B表达变化,并结合行为学观察,与经蝎毒处理后癫痫发作敏感性明显降低的大鼠进行比较。结果显示,与对照组比较,癫痫发作敏感动物前深梨状皮层T区κ型阿片受体与NR2B免疫反应阳性细胞数目均明显减少,染色强度明显降低(P<0.05),以剂量为100 mg／(kg·d)的蝎毒(SV)给予动物连续灌胃4周,可明显降低其癫痫发作敏感性(P<0.05),丽脑内前深梨状皮层T区κ型阿片受体与NR2B免疫反应活性未见明显变化。以上结果提示:前深梨状皮层T区κ型受体免疫反应活性长期降低很可能是癫痫发作敏感性长期增强的重要原因之一,而NR2B免疫反应活性长期降低可能是一种对脑内神经元过度兴奋的代偿性内源性保护机制。     

雷公藤内酯醇对阿尔茨海默病模型大鼠突触后致密物蛋白N-甲基-D-天门冬氨酸受体亚基2B和突触后致密物质95的影响

目的:探讨雷公藤内酯醇(TP)对阿尔茨海默病(AD)模型大鼠海马神经元突触后致密物中N-甲基-D-天门冬氨酸受体亚基2B(NR2B)和突触后致密物质95(PSD-95)表达的影响.方法:30只SD雄性大鼠随机分成对照组、模型组、用药组.应用免疫组织化学法和RT-PCR法检测各组大鼠海马NR2B和PSD-95蛋白和mRNA的表达.结果:免疫组织化学显色结果显示,用药组NR2B和PSD-95阳性细胞数较模型组均增多,平均光密度较模型组增加.RT-PCR结果显示,用药组NR2B和PSD-95 mRNA水平较模型组升高.结论:TP能促进AD模型大鼠海马神经元NR2B和PSD-95的表达,表明其对突触可塑性有一定的改善作用.     

N-甲基-D-天门冬氨酸受体2A亚单位在SD成年雄性大鼠不同脑区的分布

目的 获取大鼠脑部的N-甲基-D-天门冬氨酸受体2A（NMDAR _2A）表达强度分布的数据。方法 通过免疫组织化学染色和图像分析,对成年雄性SD大鼠（n=6）不同脑区的NMDAR _2A表达进行检测。结果 得到大鼠全脑各主要结构NMDAR _2A 表达强度的数据,并绘制图谱。结论
获得的NMDAR _2A表达图谱可为原位检测鼠 脑NMDAR _2A的实验提供参考。     

LTP的钙离子通道机制:VDCC LTP和NMDA LTP

长时程增强(LTP)与学习记忆机制关系密切.长时程增强的产生依赖于钙离子通道的活动特性,Ca2+经不同的钙离子通道内流引发的长时程增强对应不同的记忆作用.综述了通过N-甲基-D-天门冬氨酸(NMDA)受体钙离子通道和电压依赖性钙离子通道(VDCC)活动产生LTP及其各自对应的记忆作用,还介绍了以低频刺激方式产生长时程增强的研究实例.     

NMDA受体亚单位NR1、NR2A和NR2B在大鼠海马的免疫组织化学表达

目的 :观察N 甲基 D 门冬氨酸受体亚单位 1 (N methyl D aspartatereceptorsubunit 1 ,NR1 )、亚单位 2A(NR2A)和亚单位 2B(NR2B)在成年大鼠海马结构各区的表达特点 ,为研究三者在海马生理和病理过程中的作用提供形态学资料。方法 :大鼠脑 2 0 μm厚冰冻切片 ,免疫组织化学ABC法显色 ,图像分析。结果 :NR1、NR2A和NR2B在海马CA1～CA3区锥体细胞以及齿状回颗粒细胞普遍表达 ,三者中以NR1免疫组织化学反应最强 ,NR2A最弱 ,NR2B居中。NR1与NR2A在海马各区间的表达水平都无显著差异 ;NR2B在海马CA1区的表达明显强于其在CA3区及齿状回的表达 ,尤其是CA1区锥体细胞的顶树突在贯穿辐射层及腔隙分子层的全长中都呈高表达。结论 :NR1、NR2A和NR2B在正常海马结构各区的表达强度和形式存在差异 ,提示各区间天然N 甲基 D 门冬氨酸(N methyl D aspartate ,NMDA)受体的亚单位构成比例可能有所不同     

β淀粉样蛋白对培养海马神经元NMDA受体亚单位磷酸化及其亚细胞定位的影响

目的:探讨在β淀粉样蛋白(Aβ)突触毒性作用下,N-甲基-D-天(门)冬氨酸受体(NMDA)受体亚单位的磷酸化状态及其在细胞不同部位的表达与分布,推测其所诱导突触功能紊乱的作用机制。方法:原代培养的大鼠海马神经元加入Aβ(10μmol/L)1 h后,免疫荧光检测加药组和对照组近胞体段10μm树突上PY1325NR2A和PY1472 NR2B总表达量及突触内表达量的变化。结果:Aβ作用1 h后与对照组比较,PY1325 NR2A及PY1472 NR2B表达量均显著减少;突触内PY1325 NR2A的表达量显著增加,而PY1472 NR2B表达量没有明显变化。结论:NMDA受体亚单位的磷酸化参与Aβ的突触毒性作用,提示磷酸化后的NR2A、NR2B功能可能发生变化,即NR2A可能由保护作用变为毒性作用,而NR2B则相反。     

抗NMDA 受体抗体在神经精神狼疮发病机制中的研究进展

系统性红斑狼疮是一种累及全身多个器官和系统的自身免疫病,出现神经精神症状时,称为神经精神狼疮(NPSLE)。N-甲基-D-天(门)冬氨酸(NMDA)受体是一种跨膜离子通道型谷氨酸受体,抗NMDA 受体抗体主要分为抗NR1 型和抗NR2 型,近年抗NMDA 受体抗体在NPSLE 的发病机制中的作用成为一研究热点,尤其是抗NR2 抗体与NPSLE 密切相关,本文就到目前为止NMDA 抗体在NPSLE 中的作用机制的研究进展作一综述。     

捆绑应激对学习和记忆的影响研究进展

1神经科学关于学习和记忆的基本原理研究根据经典的Hebb原理,学习和记忆是以同时活跃的神经元之间的突触修饰能力为基础的。唐亚平等利用基因技术,通过增强神经元之间的依赖NMDA(N-Methyl-D-Aspartate即N-甲基-D-天冬氨酸)受体2B(NR2B)的突触性结合能力,诱导和维持长时程增强(L     

鞘内注射丹参酮ⅡA对坐骨神经慢性压迫性痛大鼠脊髓背角N-甲基-D-天冬氨酸受体表达的影响

目的:研究丹参酮ⅡA对坐骨神经慢性压迫性痛大鼠脊髓背角内N-甲基-D-天冬氨酸受体2B亚基(NR2B)表达的影响,探讨丹参酮ⅡA的镇痛机制。方法:SD雄性大鼠随机分为假手术组和模型组。模型组又分为生理盐水组和处理组。模型组在手术当日及术后每日在大鼠鞘内注射生理盐水0.1 ml和丹参酮ⅡA 20 mg/kg,连续注射14 d。检测各组大鼠在手术前及术后14 d的机械痛阈和热痛阈;术后第14天,免疫组织化学检测大鼠脊髓背角内NR2B的表达。结果:与假手术组比较,生理盐水组大鼠的机械痛阈和热痛阈明显降低,NR2B的表达增多;与生理盐水组比较,处理组的机械痛阈和热痛阈明显升高,脊髓背角内NR2B的表达下降,差异均有统计学意义。结论:鞘内注射丹参酮ⅡA对坐骨神经慢性压迫性痛模型大鼠的镇痛作用可能与降低脊髓背角内NR2B的表达有关。     

PI3Kγ is required for NMDA receptor-dependent long-term depression and behavioral flexibility

Phosphatidylinositol 3-kinase (PI3K) has been implicated in synaptic plasticity and other neural functions in the brain. However, the role of individual PI3K isoforms in the brain is unclear. We investigated the role of PI3Kγ in hippocampal-dependent synaptic plasticity and cognitive functions. We found that PI3Kγ has a crucial and specific role in NMDA receptor (NMDAR)-mediated synaptic plasticity at mouse Schaffer collateral-commissural synapses. Both genetic deletion and pharmacological inhibition of PI3Kγ disrupted NMDAR long-term depression (LTD) while leaving other forms of synaptic plasticity intact. Accompanying this physiological deficit, the impairment of NMDAR LTD by PI3Kγ blockade was specifically correlated with deficits in behavioral flexibility. These findings suggest that a specific PI3K isoform, PI3Kγ, is critical for NMDAR LTD and some forms of cognitive function. Thus, individual isoforms of PI3Ks may have distinct roles in different types of synaptic plasticity and may therefore influence various kinds of behavior.     

LTP of GABAergic synapses in the ventral tegmental area and beyond

One of the mechanisms by which the experience-dependent reorganization of neural circuitry can occur is through changes in synaptic strength. Almost every excitatory synapse in the mammalian brain exhibits LTP (long-term potentiation) or LTD (long-term depression), two cellular mechanisms of synaptic plasticity. However, LTP and LTD have been reported much more rarely at fast inhibitory GABA_A receptor synapses. Our recent study suggests that in vivo morphine initiates a long-lasting alteration of GABAergic synapses in the ventral tegmental area (VTA) by blocking the mechanisms required for LTP of GABAergic synapses. Here we put this work into the context of other examples of synaptic plasticity at GABAergic synapses.     

Repetitive light stimulation inducing glycine receptor plasticity in the retinal neurons

Neurotransmitter receptor plasticity is a mechanism that can regulate the temporal and intensity encoding of a synapse. While this has been extensively studied as a mechanism of learning, less is known about such processes in sensory systems. This study examines modulation of glycine receptor function at the first synapse in the retina. It was found that horizontal cells, which are postsynaptic to photoreceptors, have glycine receptor currents that are enhanced when internal calcium is elevated. This can be achieved by glutamatergic synaptic input or by activation of voltage-gated calcium channels. When the retina was maintained in a dark-adapted state, the calcium levels in horizontal cells were relatively low. After a series of brief light stimuli, the internal calcium concentration in horizontal cells was elevated, and the glycine currents were faster and greater in amplitude. The increase of internal calcium levels was caused by increased transmitter release from photoreceptors. Thus glycine receptor function is state dependent and can be rapidly altered by synaptic input from photoreceptors. Light stimulation drives glycine receptor plasticity in the retinal neural network.     

Stimulation of the lateral division of the dorsal telencephalon induces synaptic plasticity in the medial division of adult zebrafish

In ray-finned fishes, the lateral (Dl) and medial (Dm) division of the dorsal telencephalon are important in learning and memory formation. Tract-tracing studies revealed that neural connections are formed between these regions via afferent Dl fibers projecting to the Dm. However, research analyzing Dl-Dm synaptic transmission is scant. We have used electrophysiological techniques to assess neurotransmission and synaptic plasticity in projections from the Dl to the Dm in zebrafish. We demonstrate that electrical stimulation of the Dl division evoked a negative field potential in the Dm division that could be inhibited by application of the AMPA/kainate receptor antagonist, CNQX (5μM). Pairs of stimuli, when delivered at brief inter-pulse intervals (IPI), elicited paired pulse facilitation (PPF). Long-term potentiation (LTP), induced through the application of three trains of high frequency stimulation (HFS; 100Hz for 1s), lasted for more than 1h and could be inhibited with DL-AP5 (40μM), an N-methyl-d-aspartate (NMDA) receptor antagonist. Our results suggest that the intratelencephalic connection between Dl and Dm may play an important role in the synaptic plasticity of the zebrafish brain. It also provides a new electrophysiological model for studying the neural mechanisms underlying learning and memory in zebrafish.     

Enhanced NR2A subunit expression and decreased NMDA receptor decay time at the onset of ocular dominance plasticity in the ferret.

Enhanced NR2A subunit expression and decreased NMDA receptor decay time at the onset of ocular dominance plasticity in the ferret. The NMDA subtype of glutamate receptor is known to exhibit marked changes in subunit composition and functional properties during neural development. The prevailing idea is that NMDA receptor-mediated synaptic responses decrease in duration after the peak of cortical plasticity in rodents. Accordingly, it is believed that shortening of the NMDA receptor-mediated current underlies the developmental reduction of ocular dominance plasticity. However, some previous evidence actually suggests that the duration of NMDA receptor currents decreases before the peak of plasticity. In the present study, we have examined the time course of NMDA receptor changes and how they correlate with the critical period of ocular dominance plasticity in the visual cortex of a highly binocular animal, the ferret. The expression of NMDA receptor subunits NR1, NR2A, and NR2B was examined in animals ranging in age from postnatal day 16 to adult using Western blotting. Functional properties of NMDA receptors in layer IV cortical neurons were studied using whole cell patch-clamp techniques in an in vitro slice preparation of ferret primary visual cortex. We observed a remarkable increase in NR1 and NR2A, but not NR2B, expression after eye opening. The NMDA receptor-mediated synaptic currents showed an abrupt decrease in decay time concurrent with the increase in NR2A subunit expression. Importantly, these changes occurred in parallel with increased ocular dominance plasticity reported in the ferret. In conclusion, molecular changes leading to decreased duration of the NMDA receptor excitatory postsynaptic current may be a requirement for the onset, rather than the end, of the critical period of ocular dominance plasticity.     

Regulation of neuromodulator receptor efficacy--implications for whole-neuron and synaptic plasticity

Membrane receptors for neuromodulators (NM) are highly regulated in their distribution and efficacy—a phenomenon which influences the individual cell’s response to central signals of NM release. Even though NM receptor regulation is implicated in the pharmacological action of many drugs, and is also known to be influenced by various environmental factors, its functional consequences and modes of action are not well understood. In this paper we summarize relevant experimental evidence on NM receptor regulation (specifically dopamine D1 and D2 receptors) in order to explore its significance for neural and synaptic plasticity. We identify the relevant components of NM receptor regulation (receptor phosphorylation, receptor trafficking and sensitization of second-messenger pathways) gained from studies on cultured cells. Key principles in the regulation and control of short-term plasticity (sensitization) are identified, and a model is presented which employs direct and indirect feedback regulation of receptor efficacy. We also discuss long-term plasticity which involves shifts in receptor sensitivity and loss of responsivity to NM signals. Finally, we discuss the implications of NM receptor regulation for models of brain plasticity and memorization. We emphasize that a realistic model of brain plasticity will have to go beyond Hebbian models of long-term potentiation and depression. Plasticity in the distribution and efficacy of NM receptors may provide another important source of functional plasticity with implications for learning and memory.     

Hippocampal CA1 synaptic plasticity as a gamma transfer function

The capacity of activity-dependent synaptic modification is essential in processing and storing information, yet little is known about how synaptic plasticity alters the input-output conversion efficiency at the synapses. In the adult mouse hippocampus in vivo, we carefully compared the input-output relationship, in terms of presynaptic activity levels versus postsynaptic potentials, before and after the induction of synaptic plasticity and found that synaptic plasticity led synapses to respond more robustly to inputs, that is, synaptic gain was increased as a function of synaptic activity with an expansive, power-law nonlinearity, i.e. conforming to the so-called gamma curve. In extreme cases, long-term potentiation and depression coexist in the same synaptic pathway with long-term potentiation dominating over long-term depression at higher levels of presynaptic activity. These findings predict a novel function of synaptic plasticity, i.e. a contrast-enhancing filtering of neural information through a gamma correction-like process.     

Impaired Regulation of Synaptic Strength in Hippocampal Neurons from GluR1-Deficient Mice

Neurons of the central nervous system (CNS) exhibit a variety of forms of synaptic plasticity, including associative long-term potentiation and depression (LTP/D), homeostatic activity-dependent scaling and distance-dependent scaling. Regulation of synaptic neurotransmitter receptors is currently thought to be a common mechanism amongst many of these forms of plasticity. In fact, glutamate receptor 1 (GluR1 or GluRA) subunits containing L-α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors have been shown to be required for several forms of hippocampal LTP and a particular hippocampal-dependent learning task. Because of this importance in associative plasticity, we sought to examine the role of these receptors in other forms of synaptic plasticity in the hippocampus. To do so, we recorded from the apical dendrites of hippocampal CA1 pyramidal neurons in mice lacking the GluR1 subunit (GluR1 −/−). Here we report data from outside-out patches that indicate GluR1-containing receptors are essential to the extrasynaptic population of AMPA receptors, as this pool was nearly empty in the GluR1 −/− mice. Additionally, these receptors appear to be a significant component of the synaptic glutamate receptor pool because the amplitude of spontaneous synaptic currents recorded at the site of input and synaptic AMPA receptor currents evoked by focal glutamate uncaging were both substantially reduced in these mice. Interestingly, the impact on synaptic weight was greatest at distant synapses such that the normal distance-dependent synaptic scaling used by these cells to counter dendritic attenuation was lacking in GluR1 −/− mice. Together the data suggest that the highly regulated movement of GluR1-containing AMPA receptors between extrasynaptic and synaptic receptor pools is critically involved in establishing two functionally diverse forms of synaptic plasticity: LTP and distance-dependent scaling.     

A single day of ethanol exposure during development has persistent effects on bi-directional plasticity, N-methyl-D-aspartate receptor function and ethanol sensitivity

To determine factors that contribute to the learning deficits observed in individuals with fetal alcohol syndrome, we examined the effects of early postnatal ethanol exposure on forms of synaptic plasticity thought to underlie memory. Treatment of rat pups with ethanol on postnatal day 7 impaired the induction of N-methyl-D-aspartate receptor-dependent long-term potentiation and abolished homosynaptic long-term depression in the CA1 region of hippocampal slices prepared at postnatal day 30. An N-methyl-D-aspartate receptor-independent form of long-term potentiation induced by very high frequency stimulation could be induced in slices from ethanol-treated rats. Defects in long-term depression correlated with a diminished contribution of ifenprodil-sensitive N-methyl-D-aspartate receptors to synaptic transmission and defects in a spontaneous alternation behavioral task. Rats exposed to ethanol on postnatal day 7 also exhibited diminished sensitivity of synaptic N-methyl-D-aspartate receptors to block by ethanol at postnatal day 30 and decreased behavioral sedation to systemic ethanol injections. These results indicate that changes in synaptic plasticity and N-methyl-D-aspartate receptor function are likely to provide a neural substrate for the cognitive and behavioral changes that follow developmental ethanol exposure.