小鼠海马结构与脊髓损伤后抑郁症高发病率的关系研究

目的:探究脊髓损伤引发的抑郁高风险率是否与海马生理结构的改变有关。方法:制作小鼠脊髓损伤模型,分别在损伤后不同时期采用Basso Mouse Scale(BMS)评分对小鼠术后运动功能进行评估;并通过糖水偏好实验和悬尾实验评估小鼠的抑郁情况;HE染色观察海马组织内部细胞的变化;电镜观察海马亚细胞结构突触的结构变化;RT-qPCR检测突触蛋白标志物突触小泡蛋白(SYP)和突触后致密蛋白95(PSD-95)在mRNA水平上的变化。结果:行为学实验显示模型组小鼠有显著的抑郁行为,且在第7天抑郁程度最显著(P<0.01);HE染色显示,与对照组相比,模型组海马细胞排列紊乱,数量减少,形态欠规则;电镜结果显示,与对照组相比,模型组海马超微结构突触数量减少,突触活动区长度变短,突触后致密物厚度变薄,突触间隙宽度增加,突触界面曲率减小(P<0.05);RT-qPCR结果显示模型组SYP和PSD-95 mRNA表达水平较对照组降低(P<0.05)。结论:海马生理结构的改变是脊髓损伤后抑郁症高风险的原因之一。     

抑郁症小鼠模型的神经免疫改变

目的 建立慢性束缚应激（CRS）和慢性不可预见性应激（CUMS）模型，观察C57BL/6小鼠行为学指标，海马区及脾脏结构及相关因子基因表达的差异，探讨不同慢性应激造模手段对小鼠神经免疫系统的影响，为抑郁症发病机制及抗抑郁药初筛选提供实验依据。方法 建立6周的对照组、CRS及CUMS小鼠模型共45只，通过行为学评价测定小鼠行为学指标；运用HE染色观察小鼠大脑海马区及脾脏组织形态；运用尼氏染色观察海马区神经元受损情况；Real-time PCR检测海马区抑郁相关基因脑源性神经营养因子(BDNF)、五羟色胺转运体(5-HTT)，吲哚胺2，3加双氧酶1（IDO1）及脾脏炎症因子白细胞介素（IL）-1β、IL-6的表达情况。结果 慢性应激6周后， CRS组小鼠的水平穿格数及直立数无显著变化而CUMS组极显著下降；CRS组与CUMS组小鼠悬尾及强迫游泳试验累计不动时间均显著增加（P<0.05）；同时两种应激均能引起海马和脾脏结构的损伤，但CUMS组海马区的神经元损伤更严重；仅有CUMS组海马区相关基因显著改变；CUMS组脾脏IL-1β，IL-6的基因表达水平显著升高，而CRS组IL-6水平无显著变化。结论 应激6周后，CRS和CUMS均可不同程度地引起抑郁样症状；从神经免疫学角度观察，CUMS模型的抑郁样症状明显。提示，与CRS模型相比，CUMS模型更能反映机体的抑郁症状。     

氟西汀对抑郁大鼠治疗的作用机制

目的:观察氟西汀对抑郁大鼠治疗的作用机制。方法:选取30只成年雄性SD大鼠,按照随机数字表随机分为正常组、模型组、氟西汀组,每组10只。采用慢性温和不可预见性应激刺激(Chronic unpredictable mild stress,CUMS)合并孤养法建立大鼠抑郁模型,在CUMS刺激4W后氟西汀组灌胃给予氟西汀(10mg·kg-1)2W;正常组及模型组同时灌胃等体积的生理盐水。通过体重变化、蔗糖水消耗和旷场实验对大鼠进行行为学检测,HE染色观察海马神经元形态及数目改变;蛋白印迹和RT-PCR测定海马组织突触素(Synaptophysin,SYP)和突触后密致蛋白-95(Postsynaptic density-95protein,PSD-95)白及mRNA的表达水平。结果:与正常组相比,模型组4个时间点(7d,14d,21d,28d)行为学评分升高(P0.05)。与模型组比较,氟西汀组4个时间点行为学评分明显降低(P0.05)。HE结果显示,模型组海马神经元排列紊乱,细胞层变薄;Western blot结果显示,与正常组相比,模型组的SYP蛋白表达显著下降,PSD-95的蛋白水平显著升高;RT-PCR结果显示,模型组大鼠海马PSD-95mRNA表达显著升高,SYP mRNA表达较正常组显著降低(P0.05)。结论:氟西汀可明显促进CUMS大鼠神经元突触重塑,其机制可能与上调CUMS大鼠海马组织中SYP的表达,抑制PSD-95表达相关。     

对药酸枣仁-合欢花对抑郁模型大鼠海马CA3区细胞凋亡及caspase-12表达的影响

目的:研究对药酸枣仁(SZS)-合欢花(AJF)对抑郁模型大鼠海马CA3区细胞凋亡及半胱氨酸天冬氨酸特异性蛋白酶-12(caspase-12)表达的影响,从内质网应激(ERS)角度探讨其抗抑郁作用机制。方法:将雄性SD大鼠按随机数字表法分为正常对照组(Control)、模型组(CUMS)、对药酸枣仁-合欢花组(SZS+AJF)、盐酸文拉法辛组(Venlafaxine),采用孤养加慢性不可预见性温和应激(CUMS)建立抑郁症大鼠模型,并用旷场实验评价各组大鼠行为学改变。应用DNA原位末端缺口标记(TUNEL)法检测海马CA3区神经元凋亡情况,应用免疫组化检测海马CA3区caspase-12表达。结果:与Control组比较,CUMS组大鼠旷场实验得分降低,海马CA3区细胞凋亡率及caspase-12表达显著增加。与CUMS组比较,SZS+AJF组、Venlafaxine组大鼠旷场实验得分显著增加,海马CA3区细胞凋亡率及caspase-12表达显著减少。结论:对药酸枣仁-合欢花能显著改善抑郁模型大鼠的抑郁症状,降低海马CA3区caspase-12表达,抑制海马CA3区细胞凋亡。     

肝X受体激动剂GW3965对应激小鼠海马小胶质细胞活化的影响

目的:研究肝X受体（LXRs）激动剂GW3965对慢性不可预知性应激（CUS）抑郁模型小鼠海马CA1、CA2/3和DG区内小胶质细胞密度和神经炎症的作用。方法:选取4～6周龄的雄性C57BL/6J小鼠，适应性喂养1周后，随机分为对照组（control）、对照+GW组（GW）、抑郁模型组（CUS）以及抑郁模型+GW组（CUS+GW）。对CUS组和CUS+GW组小鼠进行10周的CUS干预；从第7周起，对GW组和CUS+GW组小鼠进行4周的GW3965给药。第10周末进行行为学测试后运用免疫荧光方法评估小鼠海马各亚区内小胶质细胞的密度，并采用Western Blot检测海马炎症因子的水平。结果:10周的CUS干预显著减少C57小鼠的体重以及糖水偏好实验结果，并显著增加强迫游泳实验中小鼠的不动时间；4周的GW3965治疗可以逆转以上结果。CUS干预显著增加小鼠海马CA1区、CA2/3区和DG区内Iba1⁺小胶质细胞密度，以及海马炎症因子IL-1β、TNF-α和转录因子NF-κB的蛋白表达水平，显著降低抗炎介质CD206的蛋白表达水平；而GW3965治疗可逆转上述变化。结论...     

低氧预适应后小鼠海马神经肽Y及突触的变化

目的 探讨低氧预适应产生神经保护作用的机制。方法 将小鼠随机分为对照组（H0组）和低氧组（H4组）,H4组为通过整体重复低氧建立的小鼠低氧预适应动物模型,H0组不进行低氧处理。用免疫组织化学方法检测小鼠海马神经肽Y(NPY)及突触体素（SYP）的表达,电镜观察海马CA1区的不对称突触和穿通型不对称突触形态及数量。结果 与H0组相比较,H4组海马NPY阳性细胞数量有中等量增多(n=30),SYP阳性细胞数量有明显增多(n=30),而海马CA1区的不对称突触和穿通型不对称突触数量减少(n=6)。结论 低氧预适应后海马的这些变化可能降低了神经元的兴奋性,从而增强了脑抵抗低氧/缺血的能力而产生神经保护作用。     

右美托咪定介导NLRP3/caspase-1/GSDMD信号通路改善七氟烷致老年大鼠认知功能障碍

目的 观察右美托咪定（DEX）对七氟烷所致大鼠认知功能障碍及对NLRP3/caspase-1/GSDMD信号通路的影响。方法 32只SD大鼠随机分为对照组（C组）、七氟烷组（M组）、右美托咪定低、高剂量组（DL、DH组）。旷场实验和Morris水迷宫实验测定认知功能；HE染色观察海马区神经元形态；Nissl染色观察海马区神经元数量；ELISA测定海马组织中SYP和PSD-95的表达量；Western blot法测定海马组织中NLRP3、Caspase-1和GSDMD-N蛋白含量。结果 与M组比较，DL组和DH组站立次数和穿越平台次数明显增加，活动总路程明显增加，海马区神经元形态和数量得到明显改善，SYP和PSD-95浓度明显升高，NLRP3、Caspase-1和GSDMD-N蛋白含量明显降低。结论 DEX可通过抑制NLRP3/caspase-1/GSDMD信号通路改善七氟烷麻醉所致的认知功能障碍。     

脱氢表雄酮对血管性痴呆小鼠学习和记忆能力的改善作用

目的:研究脱氢表雄酮(dehydroepiandrosterone,DHEA)对血管性痴呆小鼠学习和记忆能力的改善作用及可能机制。方法:将小鼠随机分为假手术组、模型组及DHEA(20、40和60 mg/kg)组。采用夹闭小鼠双侧颈总动脉15 min再放开的方法,建立全脑缺血再灌注所致的血管性痴呆小鼠模型。通过Y迷宫和新物体辨别实验测试小鼠的学习和记忆能力;采用Western blot法检测小鼠海马组织神经元核抗原(NeuN)、突触小泡蛋白(SYP)和突触后致密蛋白95(PSD-95)的含量。结果:与假手术组相比,在Y迷宫和新物体辨别实验中,模型组小鼠出现显著的学习和记忆障碍,DHEA治疗能显著增加Y迷宫实验中小鼠自发交替反应率,同时还可显著提高小鼠新物体辨别实验的优先指数和辨别系数(P 0. 05),其中DHEA中剂量组效果最为显著(P 0. 01)。Western blot实验结果显示,模型组小鼠海马组织NeuN、SYP和PSD-95的表达水平与假手术组比显著降低(P 0. 05); DHEA组小鼠海马组织NeuN、SYP和PSD-95蛋白的表达较模型组显著增多(P 0. 05)。结论:DHEA具有提高血管性痴呆小鼠学习和记忆能力的作用,其机制可能与减少神经元的丢失和改善突触的可塑性有关。     

氟西汀调控CUMS抑郁大鼠海马突触重塑

目的:探究氟西汀(fluoxetine)对慢性不可预见性温和刺激(chronic unpredictable mild stress,CUMS)抑郁大鼠海马突触重塑的m TOR和细胞自噬信号调控作用。方法:60只雄性Sprague-Dawley大鼠随机分成正常对照(control)组、CUMS组和氟西汀组。采用CUMS结合孤养法构建CUMS抑郁模型,期间给予氟西汀(20 mg·kg-1·d-1)灌胃治疗。通过体重变化、糖水测试水平及行为学实验验证模型建立,采用RT-PCR和Western blotting等生化方法测定突触重塑相关蛋白胶质纤维酸性蛋白(glial fibrillary acidic protein,GFAP)、突触泡蛋白(synaptophysin,SYP),细胞凋亡相关蛋白Bcl-2、cleaved caspase-3,m TOR信号通路相关蛋白m TOR、4EBP1,自噬相关蛋白beclin 1、LC3 mRNA及蛋白表达水平的变化。结果:与control组相比,CUMS大鼠的体重、糖水摄取量、旷场实验总路程和中间停留时间均下降,差异具有统计学显著性。RT-PCR和Western blotting实验结果显示,与control组相比,CUMS组SYP和GFAP的mRNA和蛋白水平显著下调,Bcl-2表达下调,cleaved caspases-3上调,m TOR及下游靶分子4EBP1磷酸化水平下调,细胞自噬关键基因beclin1和LC3在mRNA和蛋白水平显著上调。氟西汀可以减缓以上结果中的上调或下调趋势,差异具有统计学显著性。结论:氟西汀可能通过下调细胞凋亡和自噬信号通路以及上调m TOR信号通路调节海马突触重塑并缓解抑郁症状。     

表没食子儿茶素没食子酸酯对APP/PS1双转基因小鼠神经元突触可塑性和神经细胞黏附分子表达的影响

目的 观察表没食子儿茶素没食子酸酯 (EGCG) 对淀粉样前体蛋白（APP）/早老素1(PS1)双转基因小鼠空间学习记忆能力、海马 CA1 区突触超微结构和神经细胞黏附分子表达的影响。方法 选用 8 周龄雄性APP/PS1双转基因小鼠随机分为模型组、EGCG组、盐酸多奈哌齐组,另以同窝阴性小鼠设立正常组,每组 12 只。连续灌胃给药 6 个月后进行相关指标检测。采用 Morris 水迷宫实验观测APP/PS1转基因小鼠空间学习记忆能力;透射电子显微镜观察小鼠海马CA1区突触超微结构; 分别采用免疫荧光法及免疫印迹法检测APP/PS1转基因小鼠海马CA1区神经细胞黏附分子（NCAM）和唾液酸转移酶（ST8Sia Ⅱ）的蛋白表达。结果 与正常组比较,模型组逃避潜伏期延长;与模型组比较,EGCG组、盐酸多奈哌齐组小鼠逃避潜伏期下降 (P＜0.05)。电子显微镜结果显示,与模型组比较,EGCG组和盐酸多奈哌齐组突触界面曲率变化不明显;突触间隙宽度变窄,突触后致密物厚度增加（P＜0.05）。免疫荧光结果显示,海马CA1区NCAM、ST8Sia Ⅱ蛋白表达在神经元的胞体内,EGCG组和盐酸多奈哌齐组NCAM、ST8Sia Ⅱ蛋白表达明显增加 (P＜0.05),免疫印迹实验发现其含量亦呈高表达水平(P＜0.05)。结论 EGCG对 APP/PS1 转基因小鼠的空间学习记忆功能具有改善作用,其机制可能与影响小鼠海马突触结构,提高小鼠海马神经黏附分子表达有关。     

探索GalR1在雌性CUMS C57小鼠海马表达及M617对干细胞增殖的影响

目的:探究GalR1在雌性CUMS C57小鼠海马表达及GalR1激动剂M617对干细胞增殖的影响。方法:(1)将小鼠分为实验组及对照组,对照组不给予任何刺激,实验组给予慢性温和不可预知应激(CUMS)。通过糖水偏好、悬尾实验及血清皮质酮比较两组的抑郁水平;部分小鼠行免疫荧光染色比较两组海马DG的增殖情况;另一部分小鼠行qPCR检测,比较两组海马甘丙肽及其受体的表达。(2)行细胞培养,传代细胞给予不同浓度的M617处理3 d,取每组细胞铺板并加入10μmol/L的Brd U,继续孵育4 h后PFA固定,行Brdu免疫荧光染色并比较各组的阳性细胞数。结果:(1)第2、3周的糖水偏好实验显示两组糖水的消耗量未见差异,第4周CUMS组糖水消耗量少于对照组(P0.05);悬尾实验中,CUMS组静止不动时间延长(P0.05);CUMS组血清皮质酮水平明显高于对照组(P0.01)。(2)CUMS组海马DG区的Brd U+及Ki67+细胞数明显少于对照组(P0.05)。(3)q PCR结果显示CUMS组甘丙肽及GalR1基因表达水平明显增加(P0.01)。(4)不同浓度M617对干细胞增殖无明显组间差异。结论:(1)GalR1在雌性CUMS C57小鼠海马表达增高,可能参与调节抑郁症的发生过程。(2)不同浓度M617对干细胞增殖无明显影响,提示GalR1可能不参与神经干细胞增殖的调节。     

A combination extract of ginseng, epimedium, polygala, and tuber curcumae increases synaptophysin expression in APPV717I transgenic mice

ABSTRACT: BACKGROUND: The density of presynaptic markers of synaptic communication and plasticity, especially synaptophysin (SYP), is significantly correlated with cognitive decline and the progression of Alzheimer's disease (AD), indicating that synaptic protection is an important therapeutic strategy for AD. This study aims to investigate the synaptic protective effects of a combination of several active components extracted from the Chinese herbs ginseng, epimedium, polygala and tuber curcumae (GEPT), in the brains of APPV717I transgenic mice. METHODS: Three-month-old APPV717I mice were arbitrarily divided into 10 groups (n = 12 per group): APP groups receiving vehicle treatment for four or eight months (model groups), three dose groups of GEPT-treated mice for each treatment period, and donepezil-treated mice for each treatment period. Three-month-old C57BL/6J mice (n = 12) were also given vehicle for four or eight months (control groups). Vehicle, donepezil or GEPT were intragastrically administered. Immunohistochemistry (IHC) and Western blot analysis were used to assess protein expression in the hippocampal CA1 region and ratios of SYP to beta-actin levels in hippocampal tissue homogenate, respectively. RESULTS: Both IHC and Western blot revealed a decrease in SYP levels in the CA1 region of 7- and 11-month-old APPV717I transgenic mice compared with the control groups, whereas SYP levels were increased in donepezil- and GEPT-treated transgenic mice compared with the APP group. There was a significant difference in the levels of SYP detected by IHC between the GEPT high-dose group and the APP group after 4 months of treatment, and there were significant differences between all three GEPT groups and the APP group after 8 months of treatment. Western blotting showed that the SYP protein-beta-actin ratio was decreased in APP mice, while donepezil- and GEPT-treated transgenic mice showed increased trends in the SYP protein-beta-actin ratios. CONCLUSION: GEPT increases SYP expression and protects synapses before and after the formation of amyloid plaques in the brains of APPV717I transgenic mice.     

Changes in hippocampal synapses and learning-memory abilities in age-increasing rats and effects of tetrahydroxystilbene glucoside in aged rats

The aim of the present study is to investigate the changes in hippocampal synapses and their relation with learning-memory abilities at different ages, and evaluate the effects of 2,3,5,4'-tetrahydroxystilbene-2-O-beta-d-glucoside (TSG), which is one of the major components of a traditional Chinese herb Polygonum multiflorum, on brain aging. Sprague-Dawley rats at the age of 1, 3, 6, 18 and 24 months were used. TSG at doses of 30 and 60 mg/kg/day was intragastrically administered to 21-month-old rats for 3 months, respectively. Learning-memory abilities were determined by Morris water maze and passageway water maze tests. The ultrastructure of synapses in the hippocampal CA1 region was observed by electronic microscopy. The expression of synaptophysin (SYP) in whole hippocampus was measured by using immunohistochemistry. Compared with rats at 6 months of age, both the 1-month-old rats and 24-month-old rats showed longer escape latency and swimming distance in the Morris water maze test, while more errors were detected in the passageway water maze test, with a smaller number of synapses and synaptic vesicles and less expression of SYP in the hippocampus. Treatment with high-dose TSG in rats at 24 months of age had significant improvement in the learning-memory abilities in the water maze tests associated with an increase in the number of synapses and synaptic vesicles, and an elevation of expression of SYP in the hippocampus. In conclusion, hippocampal synapses count and synaptophysin expression decreased in aged rats, which may be one of the mechanisms involved in learning-memory deficit. TSG reversed the above changes in aged rats, suggesting that TSG may be beneficial for the treatment of Alzheimer disease or cognitive impairment in old people.     

N-棕榈酰乙醇胺通过调控前额叶皮质PPARα通路抗大鼠抑郁样行为

目的:探讨皮质过氧化物酶体增殖物激活受体α(PPARα)在N-棕榈酰乙醇胺(PEA)调控大鼠抑郁样行为中的作用。方法:构建大鼠慢性不可预见性温和应激(CUMS)抑郁模型。将70只大鼠随机分为正常对照组、CUMS模型组、CUMS+氟西汀(10 mg/kg)组、CUMS+PEA (2.5、5和10 mg/kg)组及CUMS+PEA (10 mg/kg)+MK886 (3 mg/kg)组。CUMS第8天开始药物处理,监测大鼠体重并测试其相关行为学变化。第36天大鼠麻醉后取脑组织标本,用免疫组化和组织形态学方法观察前额叶皮质(PFC)的突触小泡蛋白(SYP)表达及神经元形态改变;Western blot和RT-PCR法检测大鼠PFC中PPARα蛋白和mRNA的表达。结果:PEA增加CUMS抑郁模型大鼠的体重获得、蔗糖偏好率和旷场实验中的运动时间,缩短旷场实验的不动时间(P<0.01),上调PFC中SYP的蛋白表达,改善神经元的形态,增加PFC质量及PFC/全脑百分比,下调PFC中PPARα的蛋白和mRNA表达。与PEA(10 mg/kg)的组相比,MK886组大鼠在CUMS第35天体重获得和蔗糖偏好率明显降低,旷场实验中不动时间增加及运动距离减少,PFC中的SYP表达降低,PPARα的蛋白和mRNA表达上调(P<0.05)。结论:PEA拮抗CUMS大鼠的抑郁样行为,其机制可能与PEA调控PFC的PPARα通路、改善其突触可塑性有关。     

皮质酮与慢性不可预见性应激诱导的两种抑郁症模型比较

目的从行为学及分子水平比较皮质酮(CORT)与慢性不可预见性应激(CUMS)诱导的抑郁症模型的异同,为抑郁症发病机制研究及抗抑郁药物的筛选与评价模型提供一定的参考。方法将30只雄性C57BL/6小鼠随机分成对照组(Ctrl)、慢性不可预见应激组(CUMS)和皮质酮注射应激组(CORT)组,制作应激模型21d,期间每3d对小鼠进行称重。21d模型制作结束后,对小鼠进行行为学测试,并于第22天,通过眼眶取血收集动物血清,并用ELISA法测定血清皮质酮含量。眼眶取血后脱颈椎处死动物,取出动物的胸腺和脾脏进行称重,计算脏器指数;取出脑组织,置于液氮罐保存,尼氏(Nissl)染色法观察小鼠大脑海马区神经元损伤情况;采用Western blotting、RT-PCR方法测定抑郁症相关蛋白及基因的表达。结果与对照组相比,两种抑郁症模型组开场实验中的行为学指标均改变,强迫游泳和悬尾实验的累积不动时间显著升高。两个模型组的胸腺指数无明显变化,而CORT组的脾脏指数较对照组下降。CUMS和CORT组小鼠血清皮质酮含量高于对照组,CORT组与CUMS组相比有升高趋势,但差异无显著性。CUMS和CORT两种模型均使海马CA1、CA3和DG区神经元密度降低,CORT模型变化更明显。两模型组的促肾上腺素释放激素(CRH)的mRNA和蛋白的表达量均显著性增加,脑源性神经营养因子(BDNF)、磷酸化转录因子环磷腺苷反应元件结合蛋白(p-CREB)和磷酸化细胞外信号调节激酶(p-ERK)的蛋白表达水平均呈现明显地抑制,但CUMS和CORT两组之间差异无显著性。结论 CORT模型和CUMS模型均能成功构建抑郁症模型,且与下丘脑-垂体-肾上腺(HPA)轴紊乱有关,两种模型在小鼠海马结构改变及大脑BDNF-pCREB和ERK信号通路激活等方面差异无显著性。提示,CORT模型可用于抑郁症机制的研究及抗抑郁药的筛选与评价,尤其可用于以HPA轴功能紊乱所引起的抑郁症分子机制探讨。     

alpha-Isoform of calcium-calmodulin-dependent protein kinase II and postsynaptic density protein 95 differentially regulate synaptic expression of NR2A- and NR2B-containing N-methyl-d-aspartate receptors in hippocampus

N-methyl-d-aspartate receptors (NMDARs) are critical determinants of bidirectional synaptic plasticity, however, studies of NMDAR function have been based primarily on pharmacological and electrophysiological manipulations, and it is still debated whether there are subunit-selective forms of long-term potentiation (LTP) and long-term depression (LTD). Here we provide ultrastructural analyses of axospinous synapses in cornu ammonis field 1 of hippocampus (CA1) stratum radiatum of transgenic mice with mutations to two key underlying postsynaptic density (PSD) proteins, postsynaptic density protein 95 (PSD-95) and the alpha-isoform of calcium-calmodulin-dependent protein kinase II (alphaCaMKII). Distribution profiles of synaptic proteins in these mice reveal very different patterns of subunit-specific NMDAR localization, which may be related to the divergent phenotypes of the two mutants. In PSD-95, Dlg, ZO-1/Dlg-homologous region (PDZ) 3-truncated mutant mice in which LTD could not be induced but LTP was found to be enhanced, we found a subtle, yet preferential displacement of synaptic N-methyl-d-aspartate receptor subunit 2B (NR2B) subunits in lateral regions of the synapse without affecting changes in the localization of N-methyl-d-aspartate receptor subunit 2A (NR2A) subunits. In persistent inhibitory alphaCaMKII Thr305 substituted with Asp in alpha-isoform of calcium-calmodulin kinase II (T305D) mutant mice with severely impaired LTP but stable LTD expression, we found a selective reduction of NR2A subunits at both the synapse and throughout the cytoplasm of the spine without any effect on the NR2B subunit. In an experiment of mutual exclusivity, neither PSD-95 nor alphaCaMKII localization was found to be affected by mutations to the corresponding PSD protein suggesting that they are functionally independent of the other in the regulation of NR2A- and NR2B-containing NMDARs preceding synaptic activity. Consequently, there may exist at least two distinct PSD-95 and alphaCaMKII-specific NMDAR complexes involved in mediating LTP and LTD through opposing signal transduction pathways in synapses of the hippocampus. The contrasting phenotypes of the PSD-95 and alphaCaMKII mutant mice further establish the prospect of an independent and, possibly, competing mechanism for the regulation of NMDAR-dependent bidirectional synaptic plasticity.