AMPA受体和NMDA受体在leptin参与神经病理性痛机制中的作用

【目的】 观察离子型谷氨酸受体AMPA受体和NMDA受体在leptin参与神经病理性痛机制中的作用.【方法】 用膜片钳全细胞模式记录leptin是否影响正常大鼠脊髓切片背角Ⅱ层神经元AMPA受体和NMDA受体介导的电流;大鼠鞘内注射leptin,持续14 d,在第1,3,7,14天检测热痛阈和机械痛阈,在第14天处死动物,用免疫组化法和western blot检测脊髓背角AMPA受体和NMDA受体的表达.【结果】 灌流液中加入leptin能增加NMDA受体介导的电流,并有剂量依赖性,100 nmol/L leptin的作用最显著,leptin对AMPA受体介导的电流无影响;大鼠鞘内注射leptin,在第14天明显降低热痛阈和机械痛阈;leptin增加了脊髓背角NMDA受体亚单位NR1的表达,但是对AMPA受体亚单位GluR1的表达无影响,NMDA受体拮抗剂MK-801可抑制并逆转leptin诱导的痛行为及抑制leptin诱导的NR1表达增多.【结论】 Leptin可能通过影响NMDA受体参与神经病理性痛的发生.     

应激浓度皮质酮对大鼠海马神经元兴奋性氨基酸受体的快速作用

目的：研究大鼠应激浓度皮质酮对兴奋性谷氨酸受体——N-甲基-D-天冬氨酸（NMDA）受体的快速调控作用及其机制.方法：运用常规膜片钳技术,研究细胞外给予应激浓度皮质酮（CORT）对原代培养的大鼠海马神经元谷氨酸（Glu）和NMDA诱发电流（IGlu和INMDA）的快速作用,以及细胞内透析CORT对INMDA影响.结果：CORT（10μmol/L）可快速、可逆地抑制大鼠海马神经元IGlu和INMDA;细胞外牛血清清蛋白耦联的皮质酮（CORT-BSA,10μmol/L）有与CORT相似的作用;细胞内CORT（10 μmol/L）对INMDA的峰值无明显影响.结论：提示应激浓度CORT对大鼠中枢神经系统兴奋性突触传递过程有快速抑制作用,对谷氨酸受体（GluR）的作用主要是通过NMDA受体实现的;该作用是通过细胞外快速膜机制产生的.     

D-丝氨酸对大鼠视皮层神经元突触后NMDA受体功能的调制作用

目的：观察在发育大鼠视皮层脑片标本上D-丝氨酸对大鼠视皮层神经元突触后NMDA受体功能是否具有调制作用．方法：应用脑片膜片钳全细胞记录技术,记录13～15dSD大鼠视皮层Ⅱ-Ⅲ层椎体神经元的微小兴奋性突触后电流（mEPSCs）,观察D-丝氨酸对mEPSCs的调制作用．结果：mEPSCs包含两种受体电流成分,即AMPA受体与NMDA受体电流成分;应用外源性D-丝氨酸（1,10和100μmol／L）均增强了mEPSCs的NMDA受体电流成分（P〈0．01）,并呈现浓度依赖性,而应用NMDA受体阻断剂D—APV（50μmol／L）完全阻断这种增强效应．此外,D-丝氨酸没有影响mEPSCs的AMPA受体电流成分．结论：在大鼠视皮层Ⅱ-Ⅲ层锥体神经元上,突触后NMDA受体的甘氨酸结合位点是不饱和的,应用外源性D-丝氨酸可以增强NMDA受体功能,本研究为精神分裂等精神疾病的治疗提供有意义的资料．     

NMDA受体在培养神经元突触内和突触外发育中的变化

目的 观察培养大鼠海马神经元NMDA受体在突触内和突触外发育中的变化.方法 采用膜片钳的全细胞模式和外面向外模式分别记录突触内和突触外NMDA受体通道电流.结果 培养2周海马神经元突触内NMDA受体通道介导的微小兴奋性突触后电流(mEPSCNMDA)幅度比培养1周神经元小,对NMDA受体亚单位NR2B的特异拮抗剂ifnprodil的敏感性远低于培养1周神经元;培养2周神经元突触外NMDA受体的单通道电流幅度和开放概率比培养1周神经元增大,但两者的电导和翻转电位无显著差异.ifenprodil降低培养1周和2周神经元突触外NNDA受体单通道电流的电导和开放概率,且对培养2周神经元开放概率的抑制作用更显著.结论 NMDA受体通道电流在培养海马神经元突触内和突触外有发育变化,提示NMDA受体NR2亚单位在培养1周的神经元突触内和突触外均主要为NR2B亚单位;而神经元培养到2周时,突触内NR2B亚单位逐渐被NR2A亚单位取代,突触外仍主要为NR2B亚单位.     

大鼠视皮层神经元N-甲基-D-天冬氨酸受体电流的发育变化

目的　探讨大鼠视觉发育可塑性关键期内视皮层神经元N 甲基 D 天冬氨酸 (NMDA)受体介导的突触后电流的发育变化。方法　采用脑片膜片钳全细胞记录技术 ,记录出生后 14、2 1、2 8d龄Wistar大鼠视皮层神经元兴奋性突触后电流。然后在人工脑脊液中加入荷包牡丹碱 ( 2 0 μmol/L) ,记录谷氨酸受体电流 ;接着在人工脑脊液中同时加入荷包牡丹碱 ( 2 0 μmol/L)和 6 氰基 7 硝基喹啉 2 ,3 二酮 ( 2 0 μmol/L) ,记录NMDA受体电流 ,并计算NMDA受体和谷氨酸受体的峰电流的比率。结果　大鼠睁眼后 ,视皮层神经元的NMDA受体电流的下降时间显著变短 (P <0 0 5 ) ,而上升时间无明显变化 (P >0 0 5 ) ;NMDA受体电流和谷氨酸受体电流比率逐渐变小 (P <0 0 5 )。结论　随着视觉输入的增加 ,大鼠视皮层神经元的NMDA受体电流的时程变短 ,其电流成分在谷氨酸受体电流中所占的比例相对减少     

川芎、当归、红花和人参萃取液对缺氧海马神经元NMDA受体的抑制

目的：研究川芎、当归、红花和人参萃取液对缺氧海马神经元NMDA（N－甲基－D－天冬氨酸）受体功能的影响，探讨川芎、当归、红花和人参萃取液保护神经元损伤的机制。方法：采用全细胞膜片钳记录模式记录正常培养10d左右的海马神经元和经缺氧处理的海马神经元NMDA诱发电流；观察0．1％和0．5％的川芎、当归、红花和人参萃取液对NMDA电流的影响。结果：与正常培养10d左右的海马神经元相比，经缺氧处理的海马神经元NMDA诱发电流明显增大，而川芎、当归、红花和人参萃取液可快速，可逆地抑制经缺氧处理的海马神经元NMDA诱发电流。结论：川芎、当归、红花和人参萃取液对缺血缺氧引起的海马神经元NMDA受体活性过度增强有抑制作用，提示川芎、当归、红花和人参萃取液具有保护因NMDA受体过渡激活引起的神经元损伤的作用。     

α-突触核蛋白对大脑海马神经元NMDA受体影响的研究

目的 研究α-突触核蛋白(α-Synuclein,α-Syn)对海马神经元N-甲基-D-天门冬氨酸受体(N-methyl-D-aspartate receptors,NMDARs)功能的影响.方法 采用全细胞膜片钳记录模式记录正常培养10～ 12 d左右的海马神经元和经α-Syn处理1h的海马神经元NMDA诱发电流.结果 与正常培养10～12 d左右的海马神经元相比,经α-Syn处理的海马神经元NMDA诱发电流明显减小.结论 α-Syn可减少海马神经元膜上NMDARs数量,并抑制NMDARs活性.     

谷氨酸影响培养的海马神经元内钙变化机制

目的:研究谷氨酸对培养的大鼠海马神经元内钙信号的影响及作用机制。方法:用显微荧光测量技术监测神经元内钙信号的动态变化和谷氨酸对其的影响;阻断NMDA、AMPA受体后,观察谷氨酸对神经元内钙信号影响的变化。结果:谷氨酸使神经元内游离钙浓度明显升高,NMDA和AMPA受体拮抗剂、胞外钙离子浓度的降低均可不同程度地降低胞内游离钙离子升高幅度。结论:谷氨酸通过多种途径影响大鼠海马神经元内钙信号,激活NMDA和AMPA受体是其中的重要机制之一。     

缺氧及谷氨酸对大鼠海马神经元NMDA通道的影响

目的 观察大鼠海马神经元模拟缺血缺氧时谷氨酸诱发电流的改变,研究缺氧和谷氨酸对大鼠海马神经元N-甲基-D-天门冬氨酸(N-methyl-D-aspartic acid,NMDA)通道开放动力学的影响,为中枢神经损伤的康复提供理论依据.方法 实验分为6组;①对照组通氧 20μmol/LL-Glu 1.0μmol/L Gly;②组1通氧 50μmol/LL-Glu 1.0 μmol/L Gly;③组2通氧 100 μmol/L L-Glu 1.0 μmol/L Gly;④组3通氧 200μmol/L L-Glu 1.0μmol/L Gly;⑤组4缺氧 20 μmol/L L-Glu 1.0μmol/L Gly;⑥组5缺氧 20 μmol/L L-Glu 1.0μmol/L Gly 30 μmol/L MK-801.以原代培养的大鼠海马神经元为标本,运用膜片钳技术的细胞吸附式方法记录NMDA通道的单通道电流.结果 在急性缺氧条件下,NMDA通道的开放时间常数τ1,τ2较对照组延长,分别由(0.47±0.12)ms,(5.42±0.33)ms变为(1.02±0.17)ms,(7.47±0.93)ms;关闭时间常数τ1,τ2较对照组明显缩短,分别由(21.13±4.21)ms,(167.83±23.23)ms变为(6.54±1.44)ms,(21.32±2.87)ms;平均开放概率增大,由0.17±0.11变为0.79±0.32,差异有显著意义(P＜0.05).谷氨酸浓度增加时,NMDA通道开放时间常数增大,关闭时间常数减小,开放概率增大.结论 缺氧及谷氨酸能提高海马神经元NMDA通道的兴奋性,促进NMDA通道开放增加.     

Egb761抑制谷氨酸受体拮抗大鼠海马神经元兴奋毒损伤

目的 观察银杏叶提取物Egb761对海马神经元谷氨酸(Glu)兴奋毒性损伤的保护作用及其机制。方法 采用DAPI染色和TUNEL法检测Glu诱导的海马神经元细胞凋亡及Egb761的保护作用,采用全细胞膜片钳技术记录Egb761对大鼠海马神经元Glu受体电流的抑制作用。结果 Egb761拮抗Glu孵育诱导的海马神经元凋亡样死亡,其分子机制可能是抑制N 甲基-D-天冬氨酸(NMDA)型和海人酸(KA)型Glu受体。结论 银杏叶提取物Egb761通过抑制Glu离子通道而拮抗Glu对海马神经元的兴奋毒作用。     

Induction of Increased Intraceilular Calcium in Astrocytes by Glutamate through Activating NMDA and AMPA Receptors

To study the effect of glutamate on the intracellular calcium signal of pure cultured ratastrocytes and the role of NMDA and AMPA receptors in the procedure, the change of calcium sig-nal was investigated by monitoring the fluctuation of intracellular Ca2+ concentration ([Ca2+]i) onthe basis of Fura-2 single cell fluorescent ratio (F345/F380). The changes in the effect of glutamateon the intracellular calcium signal were observed after blockage of NMDA and(or) AMPA recep-tors. It was found that L-glutamate could induce an increased [Ca2+]i in most of the cells in concen-tration- and time-dependent manner. D-(-)-2-amino-5-phosphonopentanoic acid (D-AP-5, a selec-tive antagonist of the NMDA receptor) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, a selec-tive antagonist of the AMPA receptor) could abolish the effects of NMDA and AMPA respectively.Th.e treatment of D-AP-5 and CNQX simultaneously or respectively could attenuate the effect of L-glutamate at varying degrees. All these indicated that glutamate could modulate intracellular Ca2+of pure cultured rat astrocytes through different pathways. The activation of NMDA and AMPA re-ceptors took part in the complex mechanisms.     

Induction of Increased Intracellular Calcium in Astrocytes by Glutamate through Activating NMDA and AMPA Receptors

Almost 90 %ofcellsincentralnervoussystemareglia ,buttheirfunctionsarelittleknown .Whencentralnervoussystemisinjured ,itshowsgliosisnomattertheetiology .Inrecentyears ,manyresearchesrevealthatgliaalso playimportantrolesinnormalphysiologicalactivityandhaveintimaterelationshipwithneurons .Itisevidencedthataclosebidirectionalcommunicationsystemexistsbetweenneuronsandas trocytes[1] .AstrocytescanrespondtotheneurotransmitterreleasedfromactivesynapticterminalswithcytosolicCa2 +elevations ,andinturnc…     

CNTF对AMPA和NMDA引起海马神经元Ca2+浓度升高的作用

①目的探讨睫状神经营养因子(CNTF)对两种谷氨酸(Glu)离子型受体激动剂(α-氨基羧甲基异哑恶唑丙酸,AMPA;N-甲基-D-天冬氨酸,NMDA)激发的海马神经元内游离Ca2+([Ca2+]i)升高的作用.②方法原代培养海马神经元,在有或无CNTF条件下用活细胞内荧光探针Fura-2-AM实时检测AMPA和NMDA引起海马神经元内[Ca2+]i变化的情况.③结果 AMPA和NMDA均可引起细胞内[Ca2+]i升高,并呈量效依赖性;CNTF可快速抑制NMDA引起的海马神经元内[Ca2+]i升高(t=2.97～4.86,P＜0.05),而对AMPA的作用无影响(t=0.22～0.74,P＞0.05).④结论 CNTF可能通过与NMDA型受体相互作用而快速启动Ca2+信号的途径,保护因Glu引起的海马神经元损伤.AMPA型受体可能与CNTF的快速作用无关.     

A preliminary experimental study on the cardiac toxicity of glutamate and the role of AMPA receptor in rats

Background  Monosodium L-glutamate (MSG) is a food flavor enhancer and its potential harmfulness to the heart remains controversy. We sought to investigate if MSG could induce cardiac arrhythmias and apoptosis via the a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor.

Methods  Myocardial infarction was created by ligating the coronary artery and ventricular arrhythmias were monitored by electrocardiogram in the rat in vivo. Neonatal rat cardiomyocytes were isolated and cultured. Cell viability was estimated by MTT assay. Calcium mobilization was monitored by confocal microscopy. Cardiomyocyte apoptosis was evaluated by acridine orange staining, flow cytometry, DNA laddering, RT-PCR and Western blotting.

Results  MSG (i.v.) decreased the heart rate at 0.5 g/kg and even serious bradycardia at 1.5 g/kg, but could not induce ventricular tachyarrhythmias in normal rats in vivo. In rats with acute myocardial infarction (MI) in vivo, however, MSG (1.5 g/kg, i.v.) induced ventricular tachyarrhythmias, and these arrhythmias could be prevented by blocking the AMPA receptor and NMDA receptor. Selectively activating the AMPA receptor or NMDA receptor both induced ventricular tachyarrhythmias in MI rats. At the cellular level, AMPA induced calcium mobilization, oxidative stress, mitochondrial dysfunction and apoptosis in cultured cardiomyocytes, especially when the AMPA receptor desensitization was blocked by cyclothiazide. The above toxic cellular effects of AMPA were abolished by AMPA receptor blockade or by H₂O₂ scavengers.

Conclusion  MSG is proarrhythmic to the infarct rat heart at least in part via activating the AMPA receptor. AMPA receptor overactivation is also proapoptotic to the cardiomyocyte.

     

NMDA和AMPA型谷氨酸受体亚基在成年大鼠前脑室管膜及室管膜下区的分布

目的:观察前脑室管膜及室管膜下区N-甲基-D-天门冬氨酸(NMDA)和使君子酸(AMPA)型谷氨酸受体的分布. 方法:应用成年SD大鼠前脑切片免疫组织化学方法,显示NMDA和AMPA受体六种亚基的细胞定位. 结果:在室管膜及室管膜下区有NMDA受体亚基NR1,NR2C及AMPA受体亚基GluR1,GluR2/3,GluR4免疫反应阳性产物的分布,免疫阳性产物则均匀地分布在细胞质或细胞膜. 半定量分析表明NR1和GluR4阳性细胞的数目和染色密度均高于NR2C,GluR1和GluR2/3阳性细胞. 结论:结合以往研究,NMDA和AMPA受体亚基在大鼠前脑室管膜及室管膜下区定位结果提示NMDA和AMPA受体可能参与该区域神经发生等功能活动的调节.     

Effects of ketamine-midazolam anesthesia on the expression of NMDA and AMPA receptor subunit in the peri-infarction of rat brain

BACKGROUND: Activation of N-methyl-D-aspartate (NMDA) receptors and alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors play an important role in the neurons death induced by ischemia. The mitigating effect of intravenous anesthetics on ischemic neuron injury is related to their influence on NMDA receptors. This study was performed to investigate the effect of ketamine-midazolam anesthesia on the NMDA and AMPA receptor subunits expression in the peri-infarction of ischemic rat brain and explore its potential mechanism of neuroprotection. METHODS: Thirty Sprague Dawley (SD) rats were subjected to permanent middle cerebral artery occlusion under ketamine/atropine (100/0.05 mg/kg) or ketamine-midazolam/atropine (60/50/0.05 mg/kg) intraperitoneal anesthesia (n=15 each). Twenty-four hours after ischemia, five rats in each group were killed by injecting the above dosage of ketamine or ketamine-midazolam intraperitoneally and infarct size was measured. Twenty-four and 72 hours after ischemia, four rats in each group were killed by injecting the above dosage of ketamine or ketamine-midazolam intraperitoneally. After staining the brain tissue slices with toluidine blue, the survived neurons in the peri-infarction were observed. Also, the expression level of NMDA receptors 1 (NR1), NMDA receptors 2A (NR2A), NMDA receptors 2B (NR2B) and AMPA (GluR1 subunit) were determined by grayscale analysis in immunohistochemical stained slices. RESULTS: Compared with ketamine anesthesia, ketamine-midazolam anesthesia produced not only smaller infarct size [(24.1+/-4.6)% vs (38.4+/-4.2)%, P<0.05], but also higher neuron density (24 hours: 846+/-16 vs 756+/-24, P<0.05; 72 hours: 882+/-22 vs 785+/-18, P<0.05) and lower NR2A (24 hours: 123.0+/-4.9 vs 95.0+/-2.5, P<0.05; 72 hours: 77.8+/-4.1 vs 54.2+/-3.9, P<0.05) and NR2B (24 hours: 98.5+/-2.7 vs 76.3+/-2.4, P<0.05; 72 hours: 67.2 +/-7.5 vs 22.2+/-2.6, P<0.05) expression level in the peri-infarction following ischemia. CONCLUSION: The protective effects of ketamine-midazolam anesthesia on ischemic brain injury may related to decreasing NR2A and NR2B expression.     

钙离子通道在缺氧缺糖/再灌注诱导培养皮质神经元损伤中的作用

目的 探讨钙离子通道在缺氧缺糖/再灌注诱导皮质神经元损伤中的作用.方法 采用培养的大鼠皮质神经元缺氧缺糖模型,应用DAPI染色方法,以细胞凋亡率为指标,观察缺氧缺糖诱导神经兀损伤及Ca2＋螯合剂EGTA、NMDA受体拮抗剂MK-801、L-型电压门控钙通道（L-VGCC）拮抗剂尼莫地平、蛋白酪氨酸激酶（PTK）抑制剂染料木黄酮、CaMKⅡ抑制剂NK-62对缺氧缺糖/再灌注诱导神经元损伤的作用.结果 缺氧缺糖/再灌注诱导细胞发生凋亡,至再灌注24 h凋亡率达到80%左右;加入EGTA、MK-801及尼莫地平可以抑制细胞凋亡,凋亡率从80%分别降低为33%、35%和38%;加入染料木黄酮和KN-62可以使凋亡率从80%分别降低为43%和42%.结论 减少胞外Ca2＋浓度、阻断NMDA受体和L-VGCC、抑制蛋白酪氨酸激酶和CaMKⅡ可以减少缺氧缺糖/再灌注诱导的神经元损伤.缺氧缺糖/再灌注诱导的神经元损伤可能与胞外ca2＋内流有关,并与NMDA受体和L-VGCC两类钙通道的开放有关.