N-甲基-D-天冬氨酸-2B受体功能的研究进展

N-甲基-D-天冬氨酸(mDA)受体是一种配体门控型离子通道，由7种亚型(NR1，NR2A，NR2B，NR2C，NR2D，NR3A和NR3B)组成，通过其不同亚型与细胞内多种蛋白相互作用。NR2B受体参与突触信号转导和蛋白之间的调节，与学习、记忆、疼痛感受、进食行为及多种神经疾病有关。本文综述了近年来有关NR2B受体的结构、分布及功能调节等方面的研究进展。     

塞络通胶囊对大鼠多发性脑梗死恢复期Glu和GABA合成以及NMDA受体亚型表达的影响

观察塞络通胶囊(塞络通)对大鼠多发性脑梗死恢复期脑组织中神经递质谷氨酸(Glu)和γ-氨基丁酸(GABA)含量以及NMDA受体亚型NR1、NR2A和NR2B表达的影响,阐述塞络通在脑缺血后恢复期对脑组织保护的作用机制。通过大鼠颈内动脉注射微球血管栓塞剂的方法建立多发性脑梗死大鼠模型,在脑梗死后10天采用不同剂量的塞络通(16.5及33.0 mg.kg 1)连续干预60天。采用透射电子显微镜观察脑组织超微病理结构改变,高效液相色谱法检测脑组织Glu和GABA含量,免疫组织化学方法分析脑组织NMDA受体NR1、NR2A和NR2B亚型表达的变化。结果表明,与假手术组相比,模型组恢复期脑组织不仅存在神经元、神经胶质细胞和突触超微结构异常改变,而且神经递质Glu和GABA合成显著减少,同时NMDA受体NR1、NR2A和NR2B亚型表达明显升高;塞络通能够改善脑组织超微结构,明显促进神经元Glu和GABA合成,同时下调NMDA受体NR1、NR2A和NR2B亚型表达。以上结果提示,塞络通在大鼠多发性脑梗死恢复期通过促进Glu和GABA神经递质合成以及抑制NMDA受体表达而产生一定程度的神经保护作用。     

左归降糖解郁方对糖尿病并发抑郁症模型大鼠海马神经元突触功能可塑性相关蛋白的影响

目的 针对NR受体亚型及其下游分子CaMKII、SynGAP的表达情况,探索左归降糖解郁方对糖尿病并发抑郁症模型大鼠海马神经元突触功能可塑性的影响。方法 复制糖尿病并发抑郁症大鼠模型并随机分为4组：模型组,阳性药组(二甲双胍0.18 g·kg^-1+盐酸氟西汀1.8 mg·kg^-1),左归降糖解郁方高、低剂量组(32.82,8.20 g·kg^-1),以正常大鼠为空白对照组。采用Morris水迷宫检测大鼠的空间学习记忆能力,Western-blotting实验检测大鼠海马NR2A、NR2B、CaMKII、SynGAP的表达情况。结果 与空白对照组比较,模型组大鼠逃避潜伏期延长,空间探索时间减少(P<0.05),NR受体亚型NR2A、NR2B及CaMKII、SynGAP的表达明显减少(P<0.01);与模型组比较,阳性药组和左归降糖解郁方高剂量组逃避潜伏期显著缩短(P<0.05),空间探索时间显著增加(P<0.05),NR2A、NR2B、CaMKII、SynGAP的表达明显增多(P<0.05或0.01)。结论 左归降糖解郁方可以明显增强糖尿病并发抑郁症大鼠的学习记忆能力,改善认知功能障碍,缓解抑郁症状,该作用可能与调节海马NR受体亚型NR2A、NR2B及其下游分子CaMKII、SynGAP的表达,保护海马神经元突触功能可塑性有关。     

N-甲基-D-门冬氨酸受体2B 亚基在抑郁症形成机制中作用的研究进展

抑郁症是一种精神科常见的疾病。它的临床特征以心境低落,快感缺失,负性思维和精力减退为核心,严重的可使患者的社会功能、职业功能下降,并给患者家庭、社会带来沉重的经济负担。目前抑郁症的确切发病机制尚不明确,但大部分学者认为边缘系统异常可能是抑郁症发病的主要原因,其中海马作为边缘系统的重要组成部分,在抑郁形成中发挥重要作用。NMDA受体是广泛分布于中枢神经系统的离子型谷氨酸受体,主要由NR1、NR2（A、B、C和D）和NR3（A和B）3种亚型组成,在神经元可塑性,情绪调节过程中发挥着重要作用［1］,其NR2B亚基主要分布于前脑区如海马和纹状体,与情绪调节密切相关［2］。在强迫游泳实验制备的抑郁模型中,大鼠海马中含有NR2 B亚基的NMDA受体（ NR2 B ）表达水平明显升高,而NR2 A水平未见明显改变,而给予NMDA受体拮抗剂氯胺酮可以降低NR2 B水平改善抑郁症状;同样在大鼠抑郁模型中,有研究发现在给予氯胺酮以及NR2 B受体特异性拮抗剂后,大鼠抑郁症状明显改善［3］。这些研究均提示NR2 B尤其是海马NR2 B的表达变化在抑郁形成过程中发挥重要作用,因此本文拟对NR2 B在抑郁形成中的作用研究进展作一综述。     

钩藤碱对苯丙胺依赖大鼠伏核和杏仁核中NR2B蛋白表达的影响

目的:研究钩藤碱对苯丙胺依赖大鼠伏核和杏仁核中NR2B蛋白表达的影响。方法:采用条件性位置偏爱实验和免疫组化技术。结果:(1)建立了苯丙胺(2mg.kg-1,连续4d)诱导的位置偏爱模型,氯胺酮及钩藤碱低、中、高剂量均可消除苯丙胺诱导的位置偏爱效应,随钩藤碱剂量增加其效应加强,且本身无精神依赖性;(2)苯丙胺模型组大鼠伏核和杏仁核NR2B蛋白表达增加,氯胺酮及钩藤碱中、高剂量抑制NR2B表达,低剂量及本身对NR2B表达无影响。结论:伏核和杏仁核NR2B蛋白表达参与了钩藤碱抗苯丙胺依赖作用的分子机制。     

Ax亚型的家系调查1例

ABO血型亚型主要是经血型血清学实验，以抗原性弱为主要特征的多种表型。ABO亚型的存在可造成定型错误，给临床输血安全带来隐患，危急患者的生命。Ax亚型是ABO亚型中比较少见的亚型，在ABO定型中如不仔细核对，易造成漏检，特别是血清中含有抗A1抗体的最易误定为O型，区别亚型要考虑以下五方面情况：①红细胞与抗A、抗A1、抗B、抗AB及抗H的凝集强度；②红细胞上H物质活性强弱；③血清中是否存在抗A1；④分泌型人唾液中A、B和H物质；     

脑缺血再灌注损伤大鼠大脑皮质NR2A及NR2B受体表达变化

目的探讨N-甲基-D-天冬氨酸受体亚单位NR2A/2B表达与缺血再灌注损伤的关系。方法建立局灶性大脑中动脉阻塞大鼠模型观察缺血2 h再灌6～96 h的组织病理学改变,实时荧光定量PCR及Western印迹法测定大脑皮质NR2A/2B mRNA及蛋白表达。结果大鼠缺血再灌注后6 h,皮质开始出现明显病理学改变,12 h可见血管内有淤血,24 h梗死区锥体细胞出现严重的核固缩、核溶解,几乎看不到正常神经元,48 h出现大面积角质化,96 h可见炎症细胞浸润。与假手术组相比,再灌组NR2A/2B mRNA于再灌注6 h即开始一直持续明显下降(P<0.01),再灌12和24 hNR2A/2B mRNA比值均为1∶2,偏离正常的1∶1,48 h两者的表达开始上调,至96 h NR2A/2B mRNA比值达到1∶1;再灌24 h后NR2A蛋白表达显著降低(P<0.05);NR2B蛋白于再灌6 h开始明显降低,一直持续到24 h(P<0.01),48 h开始上调,96 h后蛋白表达接近假手术组水平。结论缺血2 h再灌注24 h后神经元损伤最严重,并与NR2A/2B表达改变存在时间一致性和受体亚型选择性。     

钩藤碱对苯丙胺依赖大鼠神经核团中NR2B mRNA表达的影响

目的研究钩藤碱对苯丙胺诱导的条件性位置偏爱大鼠伏核和杏仁核中NR2B mRNA表达的影响。方法将56只♂SPF级SD大鼠分为正常对照组、苯丙胺模型组、氯胺酮+苯丙胺组、钩藤碱低、中、高剂量+苯丙胺组和钩藤碱+生理盐水组,每组8只。按要求分别给予相应药物。d5用条件性位置偏爱箱观察大鼠在白箱中的停留时间,并用原位杂交技术对伏核和杏仁核NR2B mRNA表达进行检测。结果①连续4d给予苯丙胺2mg.kg-1建立了位置偏爱模型,氯胺酮及钩藤碱低、中、高剂量均可消除位置偏爱效应,随钩藤碱剂量增加效应加强,且钩藤碱自身无精神依赖性;②苯丙胺模型大鼠伏核和杏仁核NR2B mRNA表达较正常对照大鼠明显增加,氯胺酮及中、高剂量钩藤碱抑制NR2B mRNA的表达,低剂量无明显影响。钩藤碱本身不影响正常大鼠NR2B mRNA的表达。结论伏核和杏仁核NR2B mRNA的表达参与了钩藤碱抗苯丙胺依赖作用的分子生物学机制。     

过氧化物酶体增殖物激活受体β/δ在血管相关疾病中的作用及进展

<正>过氧化物酶体增殖物激活受体(PPARs)是配体激活的核受体超家族转录因子。PPAR家族包含3个蛋白:PPARα(NR1C1),PPARβ/δ(NR1C2),PPARγ(NR1C3)。与其他核受体一样,所有PPAR亚型在4个功能域中包含5~6个结构区域,称为A/B,C,D和E/F[1]。PPAR调节基因转录的方式是:PPAR被激动剂激活后,与维甲酸类X受体(RXR)结合成一     

血管紧张素转换酶抑制剂和血管紧张素Ⅱ阻滞剂联用对排钠后血压正常者血压和肾素释放的相加作用

血管紧张素Ⅱ受体阻滞剂洛沙坦（losartan）属于高效血管紧张素Ⅱ受体Ⅰ亚型（AT1）受体选择性粘抗剂。本文旨在研究血管紧张素转换酶抑制剂和血管紧张素Ⅱ阻滞剂络按坦同时作用对肾素-血管紧张素系统有否更有效的抑制作用。探讨了联用这两种药物能否减弱血管紧张素11受体互亚型阻滞剂诱导的血管紧张素11的反应性升高。并对其生物学及血液动力学方面的作用进行了研究。采用单剂量、双盲随机交叉分为四组。分别为血管紧张素11阻滞剂组，血管紧张素转换酶抑制剂组，及以上两种联用组和安慰剂组。12名轻度排钠后血压正常的男性志愿受试者，口…     

Synthesis and pharmacology of N1-substituted piperazine-2,3-dicarboxylic acid derivatives acting as NMDA receptor antagonists

The binding site for competitive NMDA receptor antagonists is on the NR2 subunit, of which there are four types (NR2A-D). Typical antagonists such as (R)-AP5 have a subunit selectivity of NR2A > NR2B > NR2C > NR2D. The competitive NMDA receptor antagonist (2R,3S)-(1-biphenylyl-4-carbonyl)piperazine-2,3-dicarboxylic acid (PBPD, 16b) displays an unusual selectivity with improved relative affinity for NR2C and NR2D vs NR2A and NR2B. Analogues of 16b bearing aroyl or aryl substituents attached to the N(1) position of piperazine-2,3-dicarboxylic acid have been synthesized to probe the structural requirements for NR2C/NR2D selectivity. A phenanthrenyl-2-carbonyl analogue, 16e, had >60-fold higher affinity for NR2C and NR2D and showed 3-5-fold selectivity for NR2C/NR2D vs NR2A/NR2B. The phenanthrenyl-3-carbonyl analogue (16f) was less potent but more selective, having 5- and 7-fold selectivity for NR2D vs NR2A and NR2B, respectively. Thus, antagonists bearing bulky hydrophobic residues have a different NR2 subunit selectivity than that of typical antagonists.     

NR2B selective NMDA receptor antagonists

NR2B antagonists have received considerable attention in recent years. In this class of excitatory amino acid receptor antagonists NR2B antagonists have shown efficacy in neuroprotection, anti-hyperalgesic and anti-Parkinson animal models. Several groups are involved in developing these compounds as therapeutic agents and evaluating newer therapeutic targets for these agents. Until recently benzylpiperidine and phenylpiperidine templates, which were based on the structures of Ifenprodil and Eliprodil, formed the basis of most SAR in this area. A few chemical leads in this class such as CP-101,606, Ro25,6981 and PD0196860 have been identified as possible development leads which have generated significant interest in this area. In addition to the efforts of Pfizer (Parke-Davis), Roche and E.Merck, several other industrial and academic research groups have continued to work in the NR2B area and recently Merck and Roche have reported new chemical leads as NR2B antagonists with significantly different biaryl templates. These new advances have raised hope, for potential success of the NR2B antagonists as new therapeutic agents, for the treatment of several pathophysiological indications.     

Insights into structure-activity relationships and CNS therapeutic applications of NR2B selective antagonists

Excessive stimulation of NMDA receptors is involved in various CNS pathologies such as Parkinson's disease, acute and chronic pain and cerebral ischaemia. The use of NMDA antagonists as therapeutic agents has been restricted as a result of unwanted side effects including hallucinations and loss of co-ordination. NR2B subtype selective antagonists have previously shown a therapeutic effect without causing the side effects of broad spectrum NMDA antagonists. Considerable research has since been devoted to the development of orally bioavailable, selective NR2B antagonists and their applications in various neurological diseases. The improved therapeutic index of these compounds is expected to be the result of the subtype selectivity and cellular location of the NR2B receptors within the CNS. This review describes recent advances in the development of NR2B antagonists as well as their therapeutic applications.     

The NR2B subtype of NMDA receptor: a potential target for the treatment of alcohol dependence

Ethanol is a small molecule acting on several neurotransmitter systems in the brain. Accumulating evidences suggest that the primary excitatory--i.e. the glutamatergic--neurotransmitter system is a particularly important site of ethanol's action. Several studies showed that ethanol is a potent and selective inhibitor of the N-methyl-D-aspartate (NMDA) receptors and prolonged ethanol exposition leads to a compensatory "up-regulation" of these receptors resulting in enhanced NMDA receptor-mediated functions after removal of ethanol. These alterations are supposed to contribute to the development of ethanol tolerance, dependence as well as the acute and delayed signs of ethanol withdrawal. In recent papers, alterations in subunit composition of NMDA receptors were reported after long term ethanol exposure. mRNA and/or protein levels of NR2A and NR2B types of subunits were found elevated both by in vivo and in vitro experiments. Our results showed that especially the NR2B subunit expression is increased in cultured hippocampal and cortical neurones after 3 days of intermittent ethanol treatment. According to the high calcium permeability, the increased agonist sensitivity and the relatively slow closing kinetics of NMDA ion channels composed of NR2B subunits, the above mentioned changes may underlie the enhanced NMDA receptor activation observed after long term ethanol exposure. Accordingly, we have tested NR2B subunit selective NMDA receptor antagonists in primary cultures of rat cortical neurones pre-treated with ethanol intermittently for 3 days and found that these compounds potently inhibited the neurotoxic effect of ethanol withdrawal. Hypothesising the involvement of enhanced NR2B subunit expression in development of alcohol dependence and withdrawal symptoms and considering the tolerable side effect profile of the NR2B subunit selective NMDA receptor antagonists, the NR2B type of NMDA receptor subunit may serve as a possible drug target in pharmacological interventions for alcoholism. The aim of this review is to give an update on the role of altered structure and function of NMDA receptors after ethanol exposure and to summarise the recent data about the activity of NR2B subunit selective NMDA receptor antagonists in model systems related to alcoholism.     

NMDA/NR2B selective antagonists in the treatment of ischemic brain injury

Glutamate is the main excitatory neurotransmitter in the central nervous system and it plays a significant role not only in synaptic transmission but also in acute and chronic neuropathologies including stroke. Presently, four receptors for glutamate have been identified and the NMDA receptor family is the most intensively studied. A number of NMDA receptor antagonists have been developed and used for treatment of neurological diseases in patients. However, all of these drugs have been failed in clinical trials either because of intolerable side effects or lack of medical efficacy. Recently, the understanding of molecular structure of NMDA receptors has been advanced and this finding thus provides information for designing subtype-selective antagonists. Using NR2B subunit selective antagonists, ifenprodil and eliprodil, as basic structure models, second and third generation congeners have been developed. Several NR2B-selective compounds showed neuroprotective actions at doses that did not produce measurable side effects in preclinical studies. Some of NR2B subunit selective antagonists have also been tested for the treatment of ischemic brain injury. The present review describes the role of glutamate in ischemic brain injury with an emphasis on the NR2B containing NMDA receptors.     

Recent advances in the development of NR2B subtype-selective NMDA receptor antagonists

Over activation of the NMDA receptor complex has been implicated in a number of neurological conditions. The use of NMDA antagonists as therapeutic agents has been limited by serious cognitive and motor side effects. Significant efforts have been reported in the development of NR2B subtype-selective antagonists, which have shown efficacy without the side effects observed with nonspecific NMDA antagonists. Classical ifenprodil-like molecules containing benzyl- and phenylpiperidines attached to a phenol or an appropriate isostere by a linker have provided valuable chemical leads as potential therapeutic agents. In this review, recent efforts in the discovery and development of structurally unique NR2B subtype-selective NMDA antagonists that do not fit the classical "ifenprodil-like" pharmacophore will be discussed.     

Role of altered structure and function of NMDA receptors in development of alcohol dependence

Long-term alcohol exposure gives rise to development of physical dependence on alcohol in consequence of changes in certain neurotransmitter functions. Accumulating evidence suggests that the glutamatergic neurotransmitter system, especially the N-methyl-D-aspartate (NMDA) type of glutamate receptors is a particularly important site of ethanol's action, since ethanol is a potent inhibitor of the NMDA receptors (NMDARs) and prolonged ethanol exposition leads to a compensatory "upregulation" of NMDAR mediated functions supposedly contributing to the occurrence of ethanol tolerance, dependence as well as the acute and delayed signs of ethanol withdrawal.Recently, expression of different types of NMDAR subunits was found altered after long-term ethanol exposure. Especially, the expression of the NR2B and certain splice variant forms of the NR1 subunits were increased in primary neuronal cultures treated intermittently with ethanol. Since NMDA ion channels with such an altered subunit composition have increased permeability for calcium ions, increased agonist sensitivity, and relatively slow closing kinetics, the abovementioned alterations may underlie the enhanced NMDAR activation observed after long-term ethanol exposure. In accordance with these changes, the inhibitory potential of NR2B subunit-selective NMDAR antagonists is also increased, demonstrating excellent potency against alcohol withdrawal-induced in vitro cytotoxicity. Although in vivo data are few with these compounds, according to the effectiveness of the classic NMDAR antagonists in attenuation, not only the physical symptoms, but also some affective and motivational components of alcohol withdrawal, novel NR2B subunit selective NMDAR antagonists may offer a preferable alternative in the pharmacotherapy of alcohol dependence.     

NMDA受体亚单位NR2B拮抗剂和神经退行性疾病

NMDA受体过度激活在多种神经退行性疾病的发生发展过程中发挥着重要作用。虽然NMDA受体拮抗剂在动物模型取得了明显的治疗效果,但严重的副反应限制了这类化合物的临床应用;而NMDA受体NR2B亚单位分布相对集中,选择性NR2B拮抗剂有望成为更安全、有效、副作用低的一类新型药物。该文就近年来国内外NR2B拮抗剂在神经退行性疾病中的研究进展作一综述。     

The effect of competitive antagonist chain length on NMDA receptor subunit selectivity

The widely-used N-methyl-D-aspartate (NMDA) receptor antagonists (R)-4-(3-phosphonopropyl) piperazine-2-carboxylic acid ((R)-CPP) and (R)-2-amino-7-phosphonoheptanoate ((R)-AP7) are frequently used as general NMDA receptor antagonists and assumed not to display significant selectivity among NMDA receptor NR2 subunits. However, electrophysiological studies have suggested that certain longer chain N-methyl-D-aspartate (NMDA) receptor competitive antagonists, such as (R)-CPP are ineffective at subpopulations of NMDA receptors in the red nucleus, superior colliculus, and hippocampus. Using recombinant receptors expressed in Xenopus oocytes, we have examined the effect of antagonist chain length on NR2 subunit selectivity. All antagonists displayed the potency order (high to low affinity) of NR2A > NR2B > NR2C > NR2D, however the longer chain antagonists (having 7 instead of 5 bond lengths between acidic groups) displayed much greater subunit selectivity than their short-chain homologues. For example (R)-CPP displayed a 50-fold difference in affinity between NR2A-containing and NR2D-containing NMDA receptors, while the shorter chain homologue 4-(phosphonomethyl) piperazine-2-carboxylic acid (PMPA) displayed only a 5-fold variation in affinity. These results can account for the earlier physiological findings and suggest that longer chain antagonists such as (R)-CPP and (R)-AP7 should not be used as general NMDA receptor antagonists.     

Effects of distinct classes of N-methyl-D-aspartate receptor antagonists on seizures, axonal sprouting and neuronal loss in vitro: suppression by NR2B-selective antagonists

Chronic treatment with high-affinity, competitive N-methyl-D-aspartate receptor (NMDAR) antagonists can promote axonal sprouting, induce neuronal loss and exacerbate seizures associated with temporal lobe epilepsy. Whether moderate-affinity uncompetitive and NR2B subunit-selective NMDAR antagonists elicit similar responses remains largely unexplored. We directly compared the effects of distinct classes of NMDAR antagonists on electrographic seizures, axonal sprouting and neuronal survival using electrophysiological recordings and histology in hippocampal slice cultures treated chronically with vehicle, D-APV (high-affinity competitive), Ro 25-6981 or ifenprodil (NR2B-selective), or memantine (moderate-affinity uncompetitive). Granule cell layer field potential recordings revealed multiple spontaneous electrographic seizures in vehicle-treated cultures following GABA(A) receptor blockade. Compared to vehicle, seizures were dramatically reduced in cultures treated with NR2B selective antagonists and slightly increased in cultures treated with moderate-affinity uncompetitive or high-affinity competitive antagonists. In general, compared to vehicle, cultures treated with NR2B selective antagonists exhibited less sprouting of granule cell mossy fiber axons (MFS) and more granule cell layer neurons. Cultures treated with high-affinity competitive or moderate-affinity uncompetitive NMDAR antagonists showed increased MFS and fewer granule cell layer neurons. These data reveal differential effects of distinct classes of NMDAR antagonists on seizure expression, axonal sprouting and neuronal survival and suggest an association between these responses.