长时程增强诱导和维持过程中海马CA1区神经细胞粘附分子蛋白水平与mRNA表达的变化

既往研究发现,神经细胞粘附分子(neural cell adhesion molecules,NCAM)对海马CA1区突触传递长时程增强(longterm potentiation,LTP)的诱导和维持极为关键。本文采用原位杂交法和Western blot法,观察了大鼠海马腑片LTP诱导和维持过程中NCAM mRNA和蛋白水平的动态变化过程。结果显示,强直刺激诱发fEPSP斜率升高10 min时,海马CA1区NCAM mRNA染色阳性神经元数量显著增加(76.6±11.5个),NCAM蛋白水平亦明显升高(7.190±0.64任意单位/50μg蛋白)。强直刺激诱发fEPSP斜率升高1 h时,NCAM mRNA染色阳性神经元数量为73.3±14.0个,NCAM蛋白量为9.031±0.71任意单位/50 μg蛋白;与强直刺激后10 min比较,NCAM mRNA表达无显著变化,而NCAM蛋白水平变化明显。NMDA受体特异阻断剂AP-5在损害LTP的同时,显著抑制NCAM mRNA和蛋白的增加。实验结果表明,在大鼠海马LTP诱导和维持过程中,NCAM mRNA增强的表达相对稳定,而NCAM蛋白水平呈现先低后高的变化。     

褪黑素对大鼠海马 CA3区长时程增强诱导的影响

目的：研究褪黑素对海马CA3区长时程增强（LTP）诱导阶段的影响及可能的机制。方法：用细胞外电生理记录方法。通过向大鼠海马CA3区分别微量注射褪黑素、Tacrine（胆碱酯酶抑制剂）和DNQX（非NMDA受体的竞争性拮抗剂）,以海马CA3区群体兴奋性突触后电位（fEPSP）斜率的改变为指标,观察PP-CA3通路的LTP变化。结果：①0．2μg/μl、1μg/μl和5μg/μl的褪黑素对CA3区的诱发电位和LTP均有抑制作用,随着剂量加大,抑制作用加强。②褪黑素能抑制Tacrine对LTP诱导的易化作用。③DNQx能部分阻断褪黑素对LTP诱导的抑制作用。结论：褪黑素对LTP诱导的抑制作用可能与胆碱能系统和非NMDA受体有关。     

锂对铅引起的大鼠海马CA1区长时程增强效应（LTP）损伤的修复作用

应用离体脑片记录技术,记录大鼠海马CA1区的兴奋性突触后电位(EPSPs),研究了锂对铅引起的大鼠海马CA1区长时程增强效应(long-termpotentiation,LTP)损伤的修复作用。结果表明:对照组大鼠海马CA1区LTP幅度为194.42±14.05%(n=10);铅处理组LTP的幅度为147.06±9.55%(n=13);而锂加铅处理组LTP的幅度为193.45±14.91%(n=15)。与对照组相比,铅处理组LTP的幅度降低了47.36%,而锂几乎完全修复了铅对大鼠海马CA1区LTP幅度的损伤。锂和铅处理后对大鼠海马CA1区的双脉冲易化(paired-pulsefacilica-tion,PPF)都有一定的抑制作用,在脉冲间隔为50ms时,这种抑制效应最大:对照组为155.58±6.35%(n=7);铅暴露组为150.26±13.74%(n=8);锂加铅处理组为140.59±15.42%(n=8)。结果表明:锂对铅引起大鼠海马CA1区LTP的损伤有一定的修复作用。     

低频刺激后海马CA1区场兴奋性突触后电位与群体锋电位的变化

在大鼠海马脑片上使用双电极在CA1区进行细胞外记录 ,观察低频刺激 (LFS)诱发同突触长时程抑制 (LTD)时场兴奋性突触后电位 (fEPSP)的斜率 (S EPSP)和群体锋电位 (PS)的幅值 (A PS)的变化。给予 90 0脉冲 1HzLFS后 ,S EPSP和A PS降低的幅度分别是 35 4± 5 3%和 6 8 0± 7 2 % ;而给予 4 5 0脉冲 1HzLFS后 ,S EPSP和A PS分别降低 14 3± 2 3%和 36 8± 6 7%。上述两组中A PS的变化率均显著大于S EPSP (P <0 0 1) ,而 90 0脉冲数组中两个指标的变化率均大于 4 5 0脉冲数组 (P <0 0 5 )。高Mg2 + (4mmol/L)使突触的传递活动减弱 ,但不影响LTD的诱发 ,在高Mg2 + 介质中 ,LFS引起的A PS变化率仍显著大于S EPSP (P <0 0 1)。结果表明 ,由LFS诱发同突触LTD的水平不仅与LFS的脉冲数有关 ,还与评价指标的选择有关     

PAF受体在铝抑制海马CA3区长时程增强中的作用

目的 :观察PAF受体在铝抑制海马CA3区长时程增强 (longtermpotentiation ,LTP)中的作用。 方法 :应用细胞外电生理记录方法 ,通过向海马CA3区分别微量注射血小板活化因子 (PlateletactivatingfactorPAF)受体拮抗剂银杏内酯B(GinkgolideB)和激动剂mc PAF ,以群体锋电位 (populationspikesPS)幅度为指标 ,观察PP CA3通路的LTP变化。结果 :① 0 .2 μmol/L的银杏内酯B对CA3区的诱发电位无影响 ,但可抑制CA3区的LTP。② 0 .2 5mol/L的三氯化铝不影响CA3区LTP ,但可加强银杏内酯B的抑制作用。③ 4 0 μmol/Lmc PAF对强直刺激引起的LTP无影响 ,却可减轻 0 .5mol/L三氯化铝的对LTP的抑制作用。结论 :PAF受体在刺激PP诱发的CA3区LTP中起作用 ,而金属铝对CA3区LTP的抑制作用至少部分与PAF受体有关。     

硫酸镁对大鼠海马CA1区神经元钠电流的抑制作用

利用全细胞膜片钳技术研究了硫酸镁 (MgSO4 )对大鼠海马CA1区神经元钠电流的影响。结果表明 ,MgSO4 可浓度依赖和电压依赖地抑制钠电流 ,半数抑制浓度为 4 0 5mmol/L。这一抑制作用与刺激频率无关。结果还表明 ,4mmol/LMgSO4 不影响钠电流的失活过程 ,却使半数激活电压由 - 5 5 8± 6 8mV变为 - 3 4 2± 6 2mV (n =8,P <0 0 1) ,而激活曲线的斜率因子不变。结果提示 ,MgSO4 抑制大鼠海马CA1区神经元的钠电流可能是其抗缺血缺氧造成的中枢神经系统损伤的机制之一     

海马长时程增强与26S蛋白酶复合体活性变化的关系

实验观察了大鼠海马脑片上突触传递长时程增强(long term potentiation,LTP)的产生和维持中26S蛋白酶复合体活性的动态变化过程,初步分析了介导其变化的受体途径。结果显示:强直刺激前,26S蛋白酶复合体活性为190±14.3 cpm/(100 μg·2 h),强直刺激诱导fEPSP斜率增加10 min时,其活性升为273±18.3 epm/(100μg·2 h),强直刺激诱导fEPSP斜率增加60 min时,26S蛋白酶复合体活性又降为210±12.8 cpm/(100μg·2 h)。NMDA受体特异阻断剂AP-5在损害L1P产生的同时,抑制26S蛋白酶复合体活性升高。实验结果提示:大鼠海马LTP产生过程中,26S蛋白酶复合体活性存在一个短时间的,依赖于N-methyl-D-aspartate(NMDA)受体的升高过程。     

丹参酮ⅡA 预防慢性缺氧大鼠认知功能障碍的电生理机制

目的:探讨丹参酮ⅡA(TⅡA)预防慢性缺氧大鼠认知功能障碍的电生理机制。方法:将18只雄性SD大鼠(200-250 g)随机分为对照组、模型组(Model组)、TⅡA(10mg/kg.d)治疗组(TⅡA组)。复制慢性缺氧大鼠认知功能障碍模型,并给予相应治疗,在脑片水平运用膜片钳技术检测海马CA1区的LTP变化,并检测海马CA1区锥体细胞的兴奋性变化。结果:(1)给予高频强直刺激(HFS)后各组兴奋性突出后电位(fEPSP)斜率均显著增加,即均可诱发LTP并持续1h以上,但模型组LTP较对照组显著减弱(P<0.05),TⅡA治疗组LTP较模型组明显增强(P<0.05);(2)慢性缺氧使海马CA1锥体细胞放电所需的刺激电流幅度显著增加、阈电位升高、兴奋性降低,同样刺激强度条件下动作电位数量减少,TⅡA干预可明显减轻慢性缺氧对海马CA1锥体细胞的上述抑制。结论:TⅡA可能是通过维持海马CA1锥体细胞的兴奋性、维持海马的突出可塑性减轻慢性缺氧对认知功能的损害。     

晚时相长时程增强翻转前后大鼠海马CA1区AMPAR/GluR2的表达

晚时相长时程增强(late-phase long-term potentiation,L-LTP)对于海马长期记忆的维持具有非常重要的作用,然而L-LTP可被诱导之后的神经元活动所翻转。本实验旨在研究海马CA1区L-LTP的翻转是否有突触前机制的参与以及L-LTP翻转前后AMPARs的表达有无变化。实验采用海马脑薄片细胞外场电位记录技术,使用强直刺激(high-frequency stimulation,HFS)诱导出CA1区L-LTP,2h后用两组间隔10min的高强度的双脉冲低频刺激(high-intensity paired-pulse low frequency stimulation,HI-PP-LFS)诱导L-LTP翻转。在LTP诱导前、诱导2h后、翻转后均给予一个双脉冲刺激,观察双脉冲比值(paired-pulse ratio,PPR)的变化;另一方面,实验通过免疫荧光组织化学方法观察AMPAR/GluR2在L-LTP翻转前后海马CA1区表达的变化。结果显示,L-LTP诱导后2h,HI-PP-LFS可诱导L-LTP的部分翻转(翻转率为61.79%±14.51%)。LTP诱导前、诱导2h后、翻转后PPR均大于1,表现为双脉冲易化(paired-pulse facilitation,PPF),且三者大小顺序为:LTP诱导后LTP翻转后LTP诱导前;在海马CA1区AMPAR/GluR2亚单位的表达方面,对照组、LTP组及LTP翻转组之间没有显著差异。上述结果提示,海马CA1区L-LTP维持与翻转均有突触前机制的参与,但L-LTP诱导与翻转前后AMPAR/GluR2表达没有发生变化。     

血小板激活因子对大鼠海马脑片CA1区LTP的作用

目的:为了探讨血小板激活因子(platelet-activating factor,PAF)对大鼠海马脑片CA1区的长时程增强效应(long-term potentiation,LTP)的影响.方法:应用离体脑片电生理记录技术,记录大鼠海马CA1区的兴奋性突触后电位EPSP,研究了PAF对大鼠海马脑片CA1区的突触传递和可塑性的影响.结果:小剂量(1μmol/L)PAF可诱发大鼠海马CA1区LTP的产生;大剂量(10～50μmol/L)PAF不能诱发大鼠海马CA1区LTP的产生,且不能阻止高频电刺激(HFS,100 Hz,1 000 ms×2,每隔20 s给予)Schffer侧支引起的大鼠海马脑片CA1区LTP的形成和维持.大剂量PAF对海马CA1区基础EPSP没有影响.PAF受体拮抗剂银杏苦内酯(ginkgolide B,GB)可拮抗小剂量PAF诱发大鼠海马CA1区LTP的产生.结论:大剂量PAF具有神经毒性,可能是通过抑制海马CA1区的LTP的形成而参与艾滋病痴呆(HIV-1 associated dementia,HAD)的形成机制.     

Hippocampal calcium dyshomeostasis and long-term potentiation in 2-week zinc deficiency

On the basis of abnormal neuropsychological behavior in the open-field test after 2-week zinc deprivation, neurochemical response was examined in young mice fed a zinc-deficient diet for 2 weeks. Serum corticosterone concentration was markedly higher in zinc-deficient mice than in the control mice. Basal signals of intracellular calcium (fluo-4 FF) were also significantly more in hippocampal slices from zinc-deficient mice. These results suggest that basal Ca2+ levels in hippocampal cells are increased by zinc deficiency. On the other hand, Schaffer collateral long-term potentiation (LTP) was unaffected by zinc deficiency; the averaged fEPSP after tetanic stimulation was 162+/-8% of baseline value in the control and 172+/-22% in zinc-deficient mice. In the Morris water maze, there was also no significant difference in learning behavior for the hidden platform task between the control and zinc-deficient mice. The present study indicates that Schaffer collateral LTP associated with spatial cognition performance are unaffected by calcium dyshomeostasis in the hippocampus elicited by 2-week zinc deprivation, which may be linked to the increased serum corticosterone concentration.     

Promotion of forskolin-induced long-term potentiation of synaptic transmission by caffeine in area CA1 of the rat hippocampus

Caffeine which is present in soft drinks has been shown to increase alertness and allays drowsiness and fatigue. The aim of this study is to investigate whether caffeine could produce a long-term effect on the synaptic transmission using extracellular recording technique in the hippocampal slices. Bath application of caffeine (100 microM) reversibly increased the slope of field excitatory postsynaptic potential (fEPSP). Forskolin (25 microM) by its own did not affect the fEPSP significantly. However, in the presence of caffeine, forskolin induced a long-term potentiation (LTP) of fEPSP. Enprofylline which has been shown to exhibit some actions like caffeine but with a low adenosine antagonistic potency did not affect the normal synaptic transmission or the effect of forskolin at a lower concentration (10 microM). However, when the concentrations were increased to 20 and 50 microM, enprofylline significantly enhanced the fEPSP slope and promoted forskolin-induced LTP. The parallel increase of fEPSP and promotion of LTP observed with enprofylline suggests that adenosine A1 antagonism is the primary mechanism behind caffeine's effect. This hypothesis was further strengthened by the finding that promotion of forskolin-induced LTP was mimicked by the non-xanthine adenosine antagonist 9-chloro-2-(furyl)[1,2,4]triazolo [1,5-c]quinazolin-5-amine (CGS 15943). The promotion of forskolin-induced LTP provides a cellular basis behind caffeine's increase in capacity for sustained intellectual performance.     

Effects of Scopolamine and Melatonin Cotreatment on Cognition,Neuronal Damage,and Neurogenesis in the Mouse Dentate Gyrus

It has been demonstrated that melatonin plays important roles in memory improvement and promotes neurogenesis in experimental animals. We examined effects of melatonin on cognitive deficits, neuronal damage, cell proliferation, neuroblast differentiation and neuronal maturation in the mouse dentate gyrus after cotreatment of scopolamine (anticholinergic agent) and melatonin. Scopolamine (1 mg/kg) and melatonin (10 mg/kg) were intraperitoneally injected for 2 and/or 4 weeks to 8-week-old mice. Scopolamine treatment induced significant cognitive deficits 2 and 4 weeks after scopolamine treatment, however, cotreatment of scopolamine and melatonin significantly improved spatial learning and short-term memory impairments. Two and 4 weeks after scopolamine treatment, neurons were not damaged/dead in the dentate gyrus, in addition, no neuronal damage/death was shown after cotreatment of scopolamine and melatonin. Ki67 (a marker for cell proliferation)- and doublecortin (a marker for neuroblast differentiation)-positive cells were significantly decreased in the dentate gyrus 2 and 4 weeks after scopolamine treatment, however, cotreatment of scopolamine and melatonin significantly increased Ki67- and doublecortin-positive cells compared with scopolamine-treated group. However, double immunofluorescence for NeuN/BrdU, which indicates newly-generated mature neurons, did not show double-labeled cells (adult neurogenesis) in the dentate gyrus 2 and 4 weeks after cotreatment of scopolamine and melatonin. Our results suggest that melatonin treatment recovers scopolamine-induced spatial learning and short-term memory impairments and restores or increases scopolamine-induced decrease of cell proliferation and neuroblast differentiation, but does not lead to adult neurogenesis (maturation of neurons) in the mouse dentate gyrus following scopolamine treatment.     

小鼠海马CAl区高频刺激诱发的突触可塑性分析

通过细胞外记录方法记录场兴奋性突触后电位（field excitatory postsynaptic potential,fEPSP）的变化是研究突触可塑性,诸如长时程增强（long-term potentiation,LTP）和双脉冲可塑性（paired-pulse plasticity,PPP）的最常见方法之一。fEPSP波形的起始斜率、起始面积、峰值及总面积等的变化常用作判断突触可塑性增强或减弱的标准。在相同记录结果中测量fEPSP波形不同部位通常会有不同的结果,因此可能得出不同的结论,这些往往会被研究者忽略。本文通过测量小鼠海马CA1区细胞fEPSP波形的起始斜率、起始面积、峰值、总面积及时间参数等,分析比较高频刺激（high-frequency stimulation,HFS）诱发的突触可塑性,包括LTP和PPP的变化。结果显示,LTP过程中AMPA受体动力学变化加快,且在同一记录中,fEPSP波形不同部位的测量分析可以产生较大幅度的LTP和PPP差异。给予HFS后,双脉冲诱发fEPSP的比率在测量起始面积时略有下降,但在测量起始斜率时则显著增加,这些结果可能导致相反的结论。因此,全面仔细地分析fEPSP波形在整个实验中的变化对正确了解突触可塑性至关重要。     

脊髓背角Ⅱ板层长时程增强诱导及维持过程中的突触形态计量学研究

本研究和体视学方法探讨了在C纤维诱发电位长时程增强(long—-term potentiation,LTP)的诱导及维持过程中的脊髓背角Ⅱ板层的突触形念变化。结果显示(1)在LTP形成后30min,Ⅱ板层内的突触后致密物质(postsynaptic density,PSD)增厚,突触间隙增宽;(2)在LTP形成后3h,PSD厚度、突触间隙宽度及突触界面曲率都有明显增加;(3)在LTP诱导和维持全过程中,总突触的数密度比对照组有明显增高。(4)在LTP形成后3h和5h,穿孔性突触的数密度与对照组比较有明显增高。上述结果显示：PSD增厚是LTP诱导阶段的主要形态学变化。突触界面曲率增人及穿孔突触数目增多是LTP维持阶段的主要形态学基础。     

Modulation of ATP-induced LTP by cannabinoid receptors in rat hippocampus

Cannabinoids exert powerful action on various forms of synaptic plasticity. These retrograde messengers modulate GABA and glutamate release from presynaptic terminals by acting on presynaptic CB1 receptors. In particular, they inhibit long-term potentiation (LTP) elicited by electrical stimulation of excitatory pathways in rat hippocampus. Recently, LTP of the field excitatory postsynaptic potential (fEPSP) induced by exogenous ATP has been thoroughly explored. The present study demonstrates that cannabinoids inhibit ATP-induced LTP in hippocampal slices of rat. Administration of 10 μM of ATP led to strong inhibition of fEPSPs in CA1/CA3 hippocampal synapses. Within 40 min after ATP removal from bath solution, robust LTP was observed (fEPSP amplitude comprised 130.1 ± 3.8% of control, n = 10). This LTP never appeared when ATP was applied in addition to cannabinoid receptor agonist WIN55,212-2 (100 nM). Selective CB1 receptor antagonist, AM251 (500 nM), completely abolished this effect of WIN55,212-2. Our data indicate that like canonical LTP elicited by electrical stimulation, ATP-induced LTP is under control of CB1 receptors.

Electronic supplementary material

The online version of this article (doi:10.1007/s11302-012-9296-5) contains supplementary material, which is available to authorized users.     

Relationship between myocardial amiodarone concentration and antiarrhythmic effect in dogs with myocardial infarction and electrically induced ventricular arrhythmias

The relationship between the antiarrhythmic effect of amiodarone and its myocardial concentration was studied in dogs with 1-week-old myocardial infarction and reproducibly inducible sustained ventricular tachycardia or ventricular fibrillation. Three groups of animals (n = 10/group) received amiodarone, 40 mg.kg-1.day-1 (low-dose amiodarone), amiodarone 60 mg.kg-1.day-1 (high-dose amiodarone), or no amiodarone (control group). After 1 week of treatment, programmed electrical stimulation was repeated, and plasma and myocardial amiodarone and desethylamiodarone concentrations were measured. In the control group, sustained ventricular tachycardia or ventricular fibrillation was induced in six dogs (p = NS) when compared with baseline data. In the low-dose amiodarone group, sustained ventricular tachycardia or ventricular fibrillation was induced only in two dogs after 1 week of treatment (p less than 0.01 vs. baseline data). Sustained ventricular tachycardia or ventricular fibrillation was induced in seven dogs after treatment with high-dose amiodarone (p = NS vs. baseline data). Plasma amiodarone concentration in the low-dose amiodarone group (2.54 +/- 1.95 micrograms/mL) was significantly less (p less than 0.01) than that in the high-dose amiodarone group (4.64 +/- 1.66 micrograms/mL). Similarly, the plasma desethylamiodarone in the low-dose amiodarone group (0.32 +/- 0.16 microgram/mL) was significantly less (p less than 0.001) than that in the high-amiodarone dose group (0.56 +/- 0.23 microgram/mL). The myocardial amiodarone concentration in the low-dose amiodarone group (49.7 +/- 23.1 micrograms/g) was significantly lower (p less than 0.001) than that in the high-dose group (98.4 +/- 32.1 micrograms/g).(ABSTRACT TRUNCATED AT 250 WORDS)     

双电极绑定技术记录在体大鼠海马CA1区长时程增强

目的:探讨双电极绑定条件下记录大鼠在体海马CA1区长时程增强的可行性。方法:雄性Wistar大鼠乌拉坦麻醉;脑立体定位仪上埋置脑室导管;安装自制的刺激/记录绑定电极;引导基础性场兴奋性突触后电位(fEP-SP);强直刺激诱导长时程增强(LTP)。结果:绑定后的刺激和记录电极能可靠地引起海马CA1区fEPSP,fEPSP的出现率几乎100%;基础性fEPSP记录可保持长时间稳定;高频刺激成功诱导出LTP并维持达3h以上,诱导率约67%;双脉冲易化记录稳定、可靠;脑室注射β淀粉样蛋白(Aβ)对LTP显示出明显的压抑作用。结论:采用双电极绑定技术进行在体海马LTP记录简便易行、节省资源、引导fEPSP和诱导LTP的成功率较高,有望成为一项重要的研究学习和记忆机制的电生理辅助手段。