钾离子浓度及离子通道电导对海马CA1区神经元自发放电的影响

目的 分析在胞外钾离子浓度[K+]0和离子通道电导变化的情况下,海马CA1区单个神经元自发放电频率和放电模式的变化.方法 对 Warman等提出的模型进行改进,应用计算机软件MATLAB建立一个包括16个房室的海马CA1区锥体细胞单个神经元的电缆模型.其中树突室不含有源通道,而胞体室含有5个离子通道(INa、INap、...     

离体大鼠海马神经元自发放电活动一般特征的研究

观察离体大鼠海马锥体细胞的生理电发放模式.在脑脊液孵育下,将玻璃微电极插入到离体大鼠海马脑片锥体细胞附近,进行胞外电脉冲记录,微机记录并保存电信号.共观察到海马部神经元自发放电主要呈5种特征,分别为不规则发放、单波规则发放、紧张发放、阵发排放及周期排放型等形式.说明神经元的生理电发放模式可能与细胞的排列次序、生理应答呈一定的相关性.     

SAMP8小鼠记忆能力与海马CA1区神经元脱失相关性研究

目的探讨快速老化小鼠(SAMP8)学习记忆能力改变与海马CA1区神经元脱失间的关系。方法随机选取6月龄雄性P8和R1小鼠各15只,使用水迷宫实验分别检测两组小鼠的逃避潜伏期和跨越平台次数,尼氏染色观测两组小鼠海马CA1区神经元形态和数量变化。结果与R1小鼠比较,P8小鼠水迷宫实验逃避潜伏期明显较长,空间探索实验跨越平台次数P8小鼠明显减少,且P8小鼠游泳轨迹呈现无目的性环游,而R1小鼠游泳轨迹多集中于原隐匿平台象限;海马CA1区神经元层次排列紊乱,数量减少;逃避潜伏期与海马CA1区神经元数量呈负相关,跨越平台次数与海马CA1区神经元神经元数量呈正相关。结论快速老化P8小鼠的学习记忆能力明显下降,且与海马CA1区神经元的结构和数量变化有密切关系,该品系小鼠为阿尔茨海默病的研究提供了较为理想的动物模型。     

海马CA3区神经元集群放电的脉冲耦合神经网络仿真研究

目的 采用脉冲耦合神经网络(pulse coupled neural network,PCNN)对海马CA3区神经元集群放电进行仿真研究.方法 PCNN模型由120个神经元组成,兴奋性神经元与抑制性神经元个数之比为5∶1.神经元间的连接权重为高斯分布.结果 PCNN仿真模型输出结果表明,在周期信号、Gaussian随机信号及两类信号的线性叠加三类输入模式下,PCNN仿真网络的输出平均发放率均小于10%;神经元之间的稀疏连接可以通过调节权重实现.结论 ①在三类不同输入模式下,PCNN仿真网络的输出平均发放率均小于10%,满足海马CA3区神经元稀疏编码的特点.②在不同刺激下,模型中神经元的平均放电频率为6.02±1.55 Hz,其频率范围为3.6-8.6 Hz,与海马区神经元放电的特征频率(θ节律)一致.③在PCNN仿真模型中,神经元之间的连接可通过调节权重矩阵实现,满足海马CA3区神经元稀疏连接的特点.④针对不同的输出模式,PCNN仿真网络可输出网络中每个神经元在不同时刻放电的时间序列.PCNN仿真模型可以反映海马CA3区神经元集群的放电特性,其仿真结果可以作为研究海马区神经元集群编码的仿真数据.     

黄芪抗脑衰老作用的研究

目的研究黄芪对快速衰老鼠脑中12个衰老相关基因表达的影响。方法雄性SAM-P/8老年鼠,随机分为对照组和黄芪组,黄芪组每日腹腔注射黄芪注射液,14d后取材,RT-PCR检测。结果黄芪组与对照组比较。Gabarb3、MAPKK4和Sortilin在鼠脑额叶和海马中表达下调,CalcineurinB、MAP2和P35仅在鼠脑海马中表达下调,RAB6A在鼠脑额叶中表达下调,Calmodulin、MAP1B、RAP2A、SCN2B和Synapsin的表达在黄芪组和对照组之间比较没有统计学差异。结论黄芪可下调上述7种基因在衰老鼠脑中的表达发挥抗衰老作用,通过抑制这些基因产物对脑的消极作用抗衰老。     

急性饮酒对小鼠海马 CA1区锋电位的影响

观察研究急性饮酒前后,小鼠海马区锋电位（Spike）的放电频率及峰峰间期等的变化,描述并分析清醒状态及急性饮酒后小鼠海马区神经元电信号的特征差异,评价急性饮酒对小鼠海马区记忆功能的影响。以 ICR 小鼠为实验对象,分成急性饮酒组（P 组）和生理盐水对照组（C 组）。在小鼠海马 CA1区植入8通道微电极阵列,利用神经信号处理采集系统 Cerebus 记录急性饮酒前后小鼠海马 CA1区神经电信号,分析比较海马区神经元放电频率以及锋电位间隔直方图（Interspike Interval Histograms ,ISI）的变化。P 组与 C 组比较,P 组平均放电率小于 C 组;与清醒状态下比较,急性饮酒后小鼠海马区神经元放电频率变低,然后随着时间逐渐增强,慢慢恢复;ISI 值从较为集中变为较为分散。急性饮酒后小鼠海马区神经元自发放电在放电频率、ISI 等神经信号的特征方面存在明显差异。急性饮酒可抑制小鼠海马区神经元放电,抑制小鼠记忆功能。     

雌激素对SAMP8小鼠学习记忆及海马CA1区神经元的影响

目的 观察雌激素对SAMP8鼠学习记忆及海马神经元的影响. 方法 将6月龄SAMP8鼠45只分为假手术组(sham组)、去卵巢组(OVX组)和去卵巢+雌激素组(OVX+E组)3组,并用同龄正常老化SAMR1小鼠作为同源对照组.采用Morris水迷宫实验检测小鼠学习记忆能力,苏木素-伊红染色和免疫组织化学显示海马CA1区神经元及神经型一氧化氮合酶(nNOS)阳性神经元的变化,流式细胞术检测其nNOS的表达量. 结果 OVX组与sham组相比,逃避潜伏期明显延长(P<0.05),跨越平台次数显著减少(P<0.05).雌激素补充治疗能改善学习记忆能力,与sham组比较差异无统计学意义(P>0.05);OVX组海马CA1区神经元病变严重,且CA1区nNOS阳性神经元的数量、吸光度和海马nNOS荧光指数(FI)值均低于sham组(P<0.05);给予雌激素后,OVX+E组各项实验结果与OVX组相比差异有统计学意义(P<0.05),与sham组相比,差异无统计学意义(P>0.05). 结论 雌激素能够改善小鼠的学习记忆能力,有效保护海马CA1区的神经元,提高海马CA1区nNOS阳性神经元的表达.     

银杏内酯B对大鼠海马CA1区神经元自发放电的影响(英文)

为了研究银杏内酯B(Ginkgolide B,BN52021)对静息状态下的海马脑片神经元活动的影响。本研究应用细胞外记录单位放电技术观察了银杏内酯B对海马神经元电活动的影响,并分析了相关机制。结果显示:(1)在43个CA1区神经元放电单位给予银杏内酯B(0.1,1,10μmol/L)2min,有42个放电单位(97.67%)放电频率明显降低,且呈剂量依赖性;(2)预先用0.2mmol/L的L-glutamate(L-Glu)灌流海马脑片,10个放电单位放电频率明显增加,表现为癫痫样放电,在此基础上灌流银杏内酯B(1μmol/L)2min,其癫痫样放电全部被抑制;(3)预先用L型钙通道开放剂BayK8644灌流8个海马脑片神经元,8个单位(100%)放电全部增加,在此基础上灌流银杏内酯B(1μmol/L)2min,7个放电单位(87.5%)放电频率明显减低;(4)在8个CA1区神经元,银杏内酯B(1μmol/L)对单位放电的抑制效应可被1mmol/L广泛钾通道阻断剂(tetraethylammonium,TEA)完全阻断。上述结果提示,银杏内酯B可抑制海马CA1区神经元的自发放电,这种作用可能与银杏内酯B抑制L型钙通道有关,而且可能与延迟整流型钾通道(delayed rectifier potassium channel,KDR)有关。银杏内酯B通过降低神经元的活动而发挥对中枢神经元的保护作用。     

跑步对早期APP/PS1转基因阿尔茨海默病小鼠海马CA1区和齿状回神经元数量的影响

目的:应用体视学方法定量研究跑步对早期APP/PS1转基因阿尔茨海默病(AD)小鼠海马CA1和齿状回区域内神经元的影响。方法:将6月龄雄性APP/PS1转基因AD小鼠,随机分为跑步组和未跑步对照组。用Morris水迷宫检测2组小鼠的空间学习记忆能力,然后用体视学方法定量研究海马CA1和齿状回区域的体积和神经元的数量。结果:与对照组相比,跑步组AD小鼠Morris水迷宫的逃避潜伏期明显缩短,平台所在象限时间百分比和穿越平台次数均显著增加。体视学研究显示,跑步组AD小鼠海马CA1和齿状回的体积分别比对照组显著增大42.8%和27.3%,并且跑步组AD小鼠海马CA1和齿状回区域内的神经元数量分别比对照组显著增加61.8%和62.2%。结论:跑步能延缓早期AD小鼠空间学习记忆能力的下降;并且可降低AD小鼠海马CA1和齿状回区域内神经元的死亡。     

双氢睾酮对快速老化小鼠海马CA1区突触可塑性和N-甲基-D-天冬氨酸受体1的影响

目的 探讨双氢睾酮(DHT)对快速老化小鼠(SAMP8)海马CA1区突触可塑性和N-甲基-D-天冬氨酸受体1(NMDAR1)的影响.方法 6月龄雄性SAMP8小鼠21只随机分为假手术组、去势组及去势+DHT补充治疗组,每组7只.DHT剂量为1mg/(kg·d),皮下注射21d后,通过Golgi染色观察海马CA1区顶树突树突棘的变化;免疫组织化学及图像分析检测突触素和NMDAR1表达的改变.结果 1.Golgi染色,去势组海马CA1区顶树突树突棘个数明显减少;DHT补充治疗后,树突棘个数明显增多.2.去势组海马CA1区突触素和NMDAR1的表达明显减少,平均吸光度值明显低于其他组(P<0.05).DHT补充治疗能明显增加突触素和NMDAR1的表达.结论 DHT可调节海马CA1区突触可塑性,使树突棘密度增多.DHT对突触可塑性的影响可能与其调节锥体细胞的NMDAR1有关.     

Electrical conductivity of the hippocampal CA1 layers and application to current-source-density analysis

Summary The microstructure of the layers in the hippocampal CA1 area suggests that differences may exist between the electrical conductivities of these layers. In order to quantify these differences a sinusoidal current was applied to hippocampal slices in a bathing medium and potential differences were measured between pairs of neighbouring electrodes from an array. The maximum relative conductivity (100%) was found in the middle part of str. radiatum, with a gradual decrease towards the fissure (84%). There was also a gradual decrease towards the alveus (70%), but in str. pyramidale the relative conductivity was only 42%. No differences were observed between the laminar conductivities of normal hippocampal slices and slices generating spontaneous interictal bursts. These results were used to carry out a one-dimensional CSD analysis of field potentials evoked by Schaffer collateral stimulation. Despite the differences in conductivity, the homogeneous and the inhomogeneous CSD approximations did not lead to differences in the spatial distribution of sources and sinks and only gave some differences in the current density, especially at the pyramidal layer and its close environment.     

Enhancement of long-term potentiation by the calcium channel agonist Bayer K8644 in CA1 of the rat hippocampus in vitro

The effect of the Ca agonist BAY K8644 was studied on long-term potentiation (LTP) of extracellular excitatory postsynaptic potentials in the stratum radiatum of CA₁ of the hippocampus in vitro. LTP was evoked by brief trains of high-frequency stimulation applied to the stratum radiatum of CA₁. 0.5% Ethanol, the vehicle used to dissolve BAY K8644, reduced LTP from 43% to 15%. An amount of 15 μM BAY K8644, in 0.5% ethanol, enhanced LTP from 13% in the ethanol control to 57%. The Ca channel antagonist verapamil did not alter control LTP, but did inhibit the potentiating action of BAY K8644 on LTP. It is postulated that the enhancement of LTP by BAY K8644 may occur through enhancement of Ca influx through voltage-dependent Ca channels.     

Hippocampal neurons transplanted into ischemically lesioned hippocampus: electroresponsiveness and reestablishment of circuitries

Summary Severe forebrain ischemia was used to damage selectively the CA1 region of the rat hippocampal formation. One week later the CA1 region was repopulated with suspensions of 18 day old fetal hippocampal tissue. Intracellular recordings were made from single units within the transplants by using the in vitro slice preparation, two to nine months following transplantation. Based on firing characteristics during depolarizing current injection, pyramidal-like and interneuron-like cells were identified within the transplants. Synaptic potentials could be evoked in the pyramidal-like neurons by stratum radiatum and stratum oriens stimulation demonstrating that normal afferent contacts had been made. Local inhibitory circuits were not obvious within the transplanted regions as demonstrated by prolonged EPSP's and the absence of early or late after-hyperpolarization. This was supported by the lack of conductance fluctuation in the active membrane when compared with the resting cell. Antidromic spikes could be evoked by applying shocks to the stratum oriens, towards the fimbria and subiculum, suggesting that the transplanted neurons were projecting basal neurites, quite long distances, along the normal efferent pathways. Thus, the transplanted neurons have the capacity to reconstruct damaged circuitries and develop intrinsic properties similar to their normal counterparts.     

Gap junctions on GABAergic neurons containing the calcium-binding protein parvalbumin in the rat hippocampus (CA1 region)

Summary Gap junctions were identified for the first time on chemically defined neurons in the central nervous system. Gap junctions were thus demonstrated on GABAergic neurons containing the calcium-binding protein parvalbumin (PV) in the rat hippocampus. Thin and semithin (0.5 m thick) sections were cut alternately and consecutively from osmium-fixed tissue which was embedded in epoxy resin and usable for conventional electron microscopic studies. The semithin sections were processed for postembedding immunocytochemistry using an anti-PV serum. Structures corresponding to the PV-immunoreactive (PV-I) profiles on the semithin sections were easily identified on electron micrographs from the adjacent thin sections. Using this technique gap junctions were found (1) between PV-I dendrites, (2) between PV-I dendrites and PV-I somata and (3) between PV-I dendrites and small processes whose origin could not be identified. Despite a systematic search, we did not find gap junction between PV-negative processes.     

Synaptic triggering of epileptiform discharges in CA1 pyramidal cells in vitro

Intra- and extracellular recordings were made in the transverse hippocampal slice in vitro to study the requirements for the triggering of epileptiform discharges of CA1 cells. Spontaneous and induced epileptiform discharges were produced by adding small amounts of sodium benzyl penicillin. Recorded intracellularly, the epileptiform activity consisted of a burst of action potentials superimposed on a depolarizing wave. Extracellular recordings demonstrated a marked synchronization. The epileptiform activity of the CA1 cells appeared without changes in the passive membrane properties or in the spike generating mechanism. Spontaneous epileptiform discharges of the CA1 cells depended upon a synaptic activation from the CA3 region. Stimulation of afferent fibres evoked an early and a late burst response in the CA1 cells. The long latency burst was caused by a re-excitation from the CA3 region. The early burst response seems to be an intrinsic property of the CA1 cells and may be induced by synaptic activation of either apical or basal dendrites. The findings suggest that synaptic depolarization is necessary for the generation of epileptiform discharges of the CA1 cells.     

Control of IsAHP in mouse hippocampus CA1 pyramidal neurons by RyR3-mediated calcium-induced calcium release

In several neuronal preparations, the ryanodine-sensitive calcium store was reported to participate in the generation of slow afterhyperpolarization currents (IsAHP) involved in spike frequency adaptation. We show that calcium release from the ryanodine-sensitive calcium store is a major determinant of the triggering of IsAHP in mouse CA1 pyramidal neurons. Whole-cell patch clamp recordings in hippocampus slices show that the intracellular calcium stores depletion using an inhibitor of the endoplasmic reticulum Ca²⁺-ATPase (5 μM cyclopiazonic acid), as well as the specific blockade of ryanodine receptors (100 μM ryanodine) both reduced the IsAHP by about 70%. Immunohistology, using an anti-RyR3 specific antibody, indicates that RyR3 expression is particularly enriched in the CA1 apical dendrites (considered as the most important site for sAHP generation). We show that our anti-RyR3 antibody acts as a functional RyR3 antagonist and induced a reduction in IsAHP by about 70%. The additional ryanodine application (100 μ M) did not further affect IsAHP, thus excluding RyR2 in IsAHP activation. Our results argue in favor of a specialized function of RyR3 in CA1 pyramidal cells in triggering IsAHP due to their localization in the apical dendrite.     

快速老化系小鼠与昆明系小鼠AD相关指标的比较

目的： 观察6月龄的快速老化系SAM-P/8、SAM-R/1小鼠与昆明系小鼠的AD相关指标的变化。方法： 取健康（20±5）g 6月龄SAM-P/8小鼠、SAM-R/1小鼠和昆明系小鼠各14只，雌雄各半，随机分成：SAM-P/8小鼠（AD疾病模型小鼠）、SAM-R/1小鼠对照组和昆明系小鼠对照组，观察上述3组小鼠行为学、神经生化、超微结构、基因表达情况。结果： 6月龄SAM-P/8小鼠1-4d学习成绩、第5 d记忆成绩低于6月龄SMA-R小鼠和昆明系小鼠（P<0.05），真性胆碱酯酶活性则高于6月龄SMA-R/1小鼠和昆明系小鼠（P<0.05）；SAM-P/8小鼠海马神经元超微结构显示明显纤维化，而SAM-R/1小鼠和昆明系小鼠无明显纤维化；SAM-P/8小鼠脑神经细胞的凋亡相关基因表达有明显上调达2倍以上，而SAM-R/1小鼠和昆明系小鼠则未见这些基因有明显上调。SAM-R/1小鼠和昆明系小鼠比较，除基因表达略有差异之外，其它指标无明显差异。结论： 6月龄SAM-P/8小鼠在很多方面已经具备了AD自然发病模型典型特征。而用于正常对照的6月龄SAM-R/1与昆明系小鼠的行为学、TchE活性、超微结构则无显著差异；凋亡相关基因表达差异不明显，而部分基因表达则有一定差异。     

Offsetting of aberrations associated with seizure proneness in rat hippocampus area CA1 by theta pulse stimulation-induced activity pattern

Epileptiform activity induces long term aberrations in hippocampal network functions. This study was conducted in pentylenetetrazol (PTZ) -kindled rats to examine offsetting of aberrations associated with seizure proneness in hippocampus area CA1 by theta pulse stimulation (TPS: 5 Hz trains for 3 min) -induced activity pattern. In hippocampal slices from both control and kindled rats, the field excitatory postsynaptic potentials (fEPSP) and population spikes (PS) were simultaneously recorded through electrodes in the apical dendrites and stratum pyramidale, respectively. The following changes in kindled vs. control slices were observed. The fEPSP needed to be greater to produce the PS recorded in the cell body layer. The fEPSP was reduced by paired stimuli whereas the PS amplitude was increased. TPS selectively depressed the PS in a lasting fashion, and shifted the fEPSP slope and the PS amplitude relation toward what was observed in controls. Both the fEPSP and PS were increased by paired stimuli at 60 min after TPS application. The lasting depressive effect of TPS on the PS amplitude was converted into facilitation by adenosine A1 receptor antagonist 8-cyclopentyl-1, 3-dipropylxanthine (CPX). Potentiation of the PS amplitude by TPS in the presence of CPX was blocked by an N-methyl-d-aspartate receptor antagonist AP5. We hypothesize that the extracellular adenosine spillover, acting through adenosine A1 receptors, during TPS-induced activity pattern could trigger a homeostatic process for correcting network imbalances caused by epileptiform activity.