大鼠海马CA1区锥体神经元树突分支的生后发育

目的 研究大鼠海马CA1区锥体神经元树突分支的生后发育。方法 应用biocytin细胞内染色方法。结果 CA1锥体神经元的树突在生后第2～3周发育最快。顶树突的分支和长度在生后21d发育成熟;而基树突要到生后56～70d才发育成熟。基树突的发育较顶树突慢。结论 细胞内染色技术可更完整地显示神经元的形态。海马CA1区锥体神经元在出生后继续发育,且基树突的发育较顶树突慢。     

过氧化氢对大鼠海马CA1区神经元钠电流的影响

目的与方法 :采用全细胞膜片钳技术研究过氧化氢 (H2 O2 )对急性分离的大鼠海马CA1区神经元钠电流的影响。结果 :①过氧化氢可剂量依赖地增大钠电流 ,剂量为 10 μmol/L和 10 0 μmol/L时 ,钠电流分别增大 4 8 0 %± 4 2 %和 88 2 %± 5 1% (n =10 )。② 10 μmol/L的H2 O2 不影响钠电流的激活过程 ,却非常显著地影响其失活过程 ,作用前后的半数失活电压分别为(- 6 4 5 8± 1 2 2 )mV和 (- 5 3 5 5± 0 94 )mV(n =10 ,P <0 0 1) ,但不改变失活曲线的斜率因子。结论 :H2 O2 作为体内氧化代谢产物可能与一些神经系统疾病的发生有关…     

海马CA1区锥体细胞内钙离子释放与突触传递的可塑性

为分析海马CA1区锥体细胞内钙离子释放与突触传递长时程增强以及长时程抑制的关系，采用全细胞膜片钳和细胞内钙成像技术，观察了不同参数的突触前刺激引起大鼠海马锥体细胞内钙离子释放的状况。结果为：100Hz、50Hz、20Hz频率，分别用50、25、15、10、5脉冲的突触前刺激均可引起锥体细胞内钙的释放，10脉冲以上的刺激引起细胞内钙释放的成功率为100％，而5脉冲的刺激引起细胞内钙的释放率为57％。100Hz 3脉冲的刺激可引起少数锥体细胞内钙释放，而5Hz各脉冲的刺激均不能引起锥体细胞内钙的释放。结果提示，长时程抑制时细胞内钙的升高并非来自于细胞内钙库的钙释放；引起长时程增强的刺激参数与引起锥体细胞内钙释放的参数相似。本文又分析了两者的异同处。     

谷氨酸对大鼠海马CA1区锥体细胞电压依赖性Na^＋电流的影响

本实验采用全细胞膜片钳技术、观察了谷氨酸对急性分离的海马ＣＡ１区神经元的电压依赖性Ｎａ＾＋通道的影响,结果发现谷氨酸对电压依赖性Ｎａ＾＋电流有明显抑制作用,其抑制方式呈电压依赖性,浓度依赖性和时间依赖性,表明谷氨酸对电压依赖性钠通道有抑制作用。     

大鼠海马CA_1区锥体神经元在衰老过程中的超微结构变化

本文对不同年龄组雄性ＳＤ大鼠海马ＣＡ_１区锥体神经元的超微结构进行了观实，结果表明随增龄：（１）锥体神经元核周体基质密度有所下降，一些细胞器在数量、形态上也有变化，还见到”空泡变性”现象．（２）锥体神经元核膜出现皱褶，染色质群集或异染色质边集，核内包含物出现，也偶见“空泡变性”现象．（３）胞突中树突发生显著改变．上述结果可能是大鼠老化的一些形态学指征。     

长期硒缺乏对大鼠子代海马CA3区突触结构参数的影响

目的　探讨硒缺乏对生长发育期大鼠神经发育的影响及机制。方法　取子3代膳食性硒碘缺乏的生长发育期大鼠,定量研究大鼠海马CA3区GrayⅠ型突触界面结构。实验分为对照组、低硒组、低碘组、低硒低碘组,利用透射电镜观察结合图像分析,比较各组大鼠海马CA3区突触的形态结构。结果　与对照组相比,低硒组、低碘组和低硒低碘组大鼠突触活性带的长度明显缩短[分别为(261 7±50 1)nm、(286 7±41 6)nm和(220 8±61 6)nm比(312 4±47 7)nm,均P<0 01],突触后致密物质的厚度明显缩短[分别为( 22 9±6 3 )nm、( 27 5±8 6 )nm和( 25 2±6 5 )nm比(48 1±12 3)nm,均P<0 01 ],低硒组和低碘组的突触界面曲率下降( 1 076±0 039和1 079±0 038比1 108±0 054,P<0 01),低硒低碘组的突触间隙宽度明显缩小[ (11 1±3 3)nm比(16 1±4 0)nm,P<0 01]。结论　膳食性硒缺乏可能通过在突触水平发生的神经元改变,影响学习记忆等神经功能。     

大鼠海马CA3区胆碱能神经元的衰老变化

目的:探讨大鼠海马CA3区胆碱能神经元增龄性变化的规律.方法:SD大鼠随机分为1～2月龄、4～5月龄,11～12月龄、≥24月龄4组,常规石蜡包埋海马连续冠状切片,尼氏染色、乙酰胆碱转移酶(ChAT)免疫组织化学显色,图像分析仪测量ChAT免疫反应阳性产物的光密度及其阳性神经元的多种形态学参数.结果:随着年龄的增长,大...     

琥珀酸在海马CA1区对突触前GABA释放的影响

为了观察琥珀酸在大鼠海马CA1区对突触前GABA释放的影响,我们采用红外可视全细胞膜片钳技术记录了琥珀酸对γ-氨基丁酸(GABA)能自发性微小抑制性突触后电流(miniature inhibitory postsynaptic currents,mIPSCs)的作用。结果显示不同浓度的琥珀酸(10-6mol/L、10-5mol/L、10-4mol/L和10-3mol/L)在海马CA1区均能以浓度依赖的方式增强GABA能mIPSCs的频率,而对其电流幅度没有影响。10-4mol/L琥珀酸组GABA能mIPSCs的频率为2.25±0.99Hz,与正常对照组相比有显著性差异(n=8,P<0.01),而其电流幅度为31.63±6.16pA,与正常对照组相比没有差异(n=8,P>0.05)。以上实验结果表明琥珀酸能通过增强突触前GABA的自发性释放,对海马CA1区神经元产生超极化作用,此作用可能是琥珀酸抑制癫痫形成的主要方式之一。     

小鼠海马CA1区轴棘突触树突棘头与突触后致密体大小的相关性

目的探讨小鼠海马CA1区兴奋性轴棘突触树突棘头与突触后致密体(postsynaptic density,PSD)是否存在大小的相关性.方法利用Golgi染色、超薄连续切片及NIH图像分析系统测量海马CA1区锥体细胞树突棘头及突触后致密体的大小.结果光镜下测量海马CA1区第2、3级顶树突的树突棘头平均面积为(0.429±0.230)μm2,频数分布为正偏态分布曲线.电镜所测树突棘头的平均体积为(0.032 63±0.024 03)μm3;PSD平均体积为(0.002 318±0.001 362)μm3,PSD与树突棘头体积之比为0.106±0.035.树突棘头体积频数分布曲线和PSD体积频数的分布曲线非常相似,两者呈显著的正相关.结论海马CA1区轴棘突触的树突棘头大小与其突触后致密体的大小具有显著的相关性.     

焦亚硫酸钠对大鼠海马CA1区神经元钠电流的影响

目的：探讨SO2 及其体内衍生物（亚硫酸盐和亚硫酸氢盐）对中枢神经元钠通道的影响。 方法: 采用全细胞膜片钳技术研究了焦亚硫酸钠（SMB）对大鼠海马CA1区神经元钠电流的影响及超氧化物歧化酶(SOD)、过氧化氢酶(CAT)及谷胱甘肽过氧化物酶(GPx)相应的保护作用。 结果： ① 焦亚硫酸钠可剂量依赖性地增大全细胞钠电流，剂量为2 μmol/L和20 μmol/L时，钠电流分别增大（22.36±3.28）% 和（65.05±5.75）%（n=10）。② 10　μmol/L的焦亚硫酸钠不影响钠电流的激活过程，却非常显著地影响其失活过程，使失活曲线显著右移，作用前后的半数失活电压分别为（-82.38±0.54）mV和（-69.39±0.41）mV (n=10, P<0.01), 但失活曲线的斜率因子未见改变。③ SOD(1×106 U/L)、CAT(2×106 U/L) 及GPx (1×104 U/L) 均可使SMB（10 μmol/L）增大的钠电流部分恢复。 结论： SMB增大钠电流并抑制其失活过程，从而影响神经细胞的兴奋性，这一效应可能与硫中心或氧中心自由基的损伤作用有关。     

The synaptically evoked late hyperpolarisation in hippocampal CA1 pyramidal cells is resistant to intracellular EGTA

It has been suggested that the late hyperpolarisation following synaptic activation of hippocampal CA1 pyramidal neurons is activated by calcium influx. This hypothesis was examined using microelectrodes containing EGTA. Intracellular injection of EGTA blocked the afterhyperpolarisation which normally followed cell firing produced by injection of a depolarising current or the ionophoresis of glutamate onto the apical dendrites. In contrast, the hyperpolarisation following synaptic activation was resistant to EGTA. The results suggest that this potential is not dependent on intracellular Ca2+. Other possible mechanisms are discussed.     

The slow inhibitory postsynaptic potential in rat hippocampal CA1 neurones is blocked by intracellular injection of QX-314

Intracellular recordings were made from CA1 pyramidal neurones in the rat hippocampus slice preparation. The recording electrodes contained potassium acetate (4 M) with or without the quaternary lidocaine derivative, QX-314 (50 mM). Both fast (f) and slow (s) inhibitory postsynaptic potentials (IPSP) were evoked by low-frequency orthodromic stimulation. The s-IPSP was rapidly reduced by QX-314 injection. It decreased along a similar time course to the dV/dt of the action potential (AP). The f-IPSP and excitatory postsynaptic potential were not significantly reduced in size at a time when the s-IPSP was virtually abolished by QX-314. It is concluded that conductance through the K⁺ channels which are coupled to GABA_B receptors is readily blocked by QX-314, while the Cl⁻ channels which are coupled to GABA_A receptors and the cation channels coupled to the glutamate receptors are relatively resistant to the local anaesthetic.     

Noradrenaline-induced spontaneous inhibitory postsynaptic currents in mouse basolateral nucleus of amygdala pyramidal neurons: Comparison with dopamine-induced currents

The basolateral nucleus of the amygdala (BLA) receives both noradrenergic and dopaminergic projections. These projections are thought to be important for modulation of amygdala neural circuits. In BLA pyramidal neurons, noradrenaline (NA) is known to facilitate gamma-aminobutyric acid (GABA)ergic spontaneous inhibitory postsynaptic currents (sIPSCs) through excitation of interneurons. Dopamine (DA) also is known to facilitate GABAergic sIPSCs in pyramidal neurons of the amygdala region including the BLA. It is unclear which neurotransmitter, NA or DA, is predominant in facilitating sIPSC in the BLA. Whether NA and DA facilitate sIPSC in different or the same pyramidal neurons also remains unknown. Herein, we employed the patch clamp recording technique on BLA pyramidal neurons in mouse brain slices, and compared the facilitating actions of NA and DA on sIPSCs. First NA and then DA, or first DA and then NA, were applied to a slice. NA enhanced sIPSC frequency in the majority (80–90%) of pyramidal neurons tested, whereas DA enhanced sIPSC frequency in relatively few neurons (approximately 30%). Neurons responding to NA alone and DA alone accounted, respectively, for 54.3% and 2.9% of the pyramidal neurons tested (11.4% of neurons responded to neither NA nor DA). Pyramidal neurons in which NA and DA both facilitated sIPSCs accounted for 31.4% of neurons tested. These results suggest that NA facilitates GABAergic sIPSCs in a larger proportion of mouse BLA pyramidal neurons than DA.     

Effects of ammonium salts on synaptic transmission to hippocampal CA1 and CA3 pyramidal cells in vivo

The effects of ammonium acetate or chloride, perfused through the lateral ventricle, were studied on the hippocampal formation of the rat. During perfusion with ammonia, the population spikes, evoked by stimuli delivered to the fimbria, were first increased and then reduced. On the other hand, the late positive wave gradually decreased throughout the application of ammonia. The inhibition, studied by the paired-pulse test, was found to be reduced when the population spike was transiently enhanced, indicating that disinhibition could be responsible for the enhancement of synaptically evoked responses. Neither antidromically evoked population spikes nor the typical effects of iontophoretically applied glutamate, aspartate or gamma-aminobutyrate were changed by ammonia. These findings can be accounted for by a single action of ammonia, a depression of excitatory synaptic transmission, the excitatory synapses on inhibitory interneurons being more readily depressed than those on the pyramidal cells. Both effects, early hyperexcitability and late depression, are probably due to a reduction in the release of the excitatory neurotransmitter, glutamate and/or aspartate. We tentatively suggest that these mechanisms are responsible for some of the symptoms observed during the development of hyperammonemic encephalopathies.     

Action of tachykinins in the hippocampus: facilitation of inhibitory drive to GABAergic interneurons

By acting on neurokinin 1 (NK1) receptors, neuropeptides of the tachykinin family can powerfully excite rat hippocampal GABAergic interneurons located in the CA1 region and by this way indirectly inhibit CA1 pyramidal neurons. In addition to contact pyramidal neurons, however, GABAergic hippocampal interneurons can also innervate other interneurons. We thus asked whether activation of tachykinin-sensitive interneurons could indirectly inhibit other interneurons. The study was performed in hippocampal slices of young adult rats. Synaptic events were recorded using the whole-cell patch clamp technique. We found that substance P enhanced GABAergic inhibitory postsynaptic currents in a majority of the interneurons tested. Miniature, action potential-independent inhibitory postsynaptic currents were unaffected by substance P, as were evoked inhibitory synaptic currents. This suggests that the peptide acted at the somatodendritic membrane of interneurons, rather than at their axon terminals. The effect of substance P was mimicked by a selective NK1 receptor agonist, but not by neurokinin 2 (NK2) or neurokinin 3 (NK3) receptor agonists, and was suppressed by a NK1 selective receptor antagonist. In contrast to substance P, oxytocin, another peptide capable of activating hippocampal interneurons, had no effect on the inhibitory synaptic drive onto interneurons. We conclude that tachykinins, by acting on NK1 receptors, can influence the hippocampal activity by indirectly inhibiting both pyramidal neurons and GABAergic interneurons. Depending on the precise balance between these effects, tachykinins may either activate or depress hippocampal network activity.     

红藻氨酸对大鼠海马锥体细胞钙电流的影响

目的：应用膜片钳技术,观察红藻氨酸（KA）对大鼠海马锥体细胞ca2＋电流的影响,以研究癫痫的发病机制。方法：采用酶加机械分离法制备出生10～12d的大鼠海马锥体神经元标本,用全细胞膜片钳技术测定其生理学特性及观察KA对ca2＋电流的影响。结果：分离出的海马锥体细胞形态正常,有较长突起;用膜片钳技术证实,其保存了主要的离子通道活性。KA20μmol／L和100μmol／L的浓度均可使海马锥体细胞ca2＋电流峰值增大（n=8,P〈0．01）。结论：①大鼠海马锥体神经细胞具有明显的突起,细胞膜表面光洁、晕光好,适用于膜片钳实验研究;②KA使ca2＋内流增加,引起“Ca”超载”导致细胞毒性等一系列反应;③KA通过激活α-氨基羟甲基恶唑丙酸（AMPA）受体,诱发快速的兴奋性突触后电位（EPSP）,参与兴奋性突触传递。AMPA受体的激活可能是癫痫的发病机制之一。     

Frequency-to-voltage conversion in the pyramidal tract neuron: an important role of the inhibitory postsynaptic potential

Frequency-coded impulses are known to be converted into postsynaptic potentials (PSPs) at the synapse of a target neuron. This can be termed frequency-voltage (F-V) conversion. Studies on this problem in pyramidal tract neurons (PTNs) showed that not only the amplitude but also the duration of depolarizing PSPs was determined as a function of the input impulse frequency. Two opposite patterns of F-V conversion were observed following activation of two input systems to PTNs. Inhibitory postsynaptic potentials were found to play an important role in the regulation of the duration of PSPs by curtailing excitatory post-synaptic potentials.     

Spontaneous inhibitory postsynaptic potentials in guinea pig neocortex and olfactory cortex neurones

The membrane potential of olfactory cortex and neocortex neurones in vitro was recorded using conventional microelectrode techniques. During recordings with KCl- or CsCl-filled microelectrodes, spontaneous, subthreshold, transient membrane depolarizations were observed. These were abolished by the GABAA-receptor antagonist, bicuculline methiodide, and were prolonged by the barbiturate pentobarbitone. In most cells they were abolished by tetrodotoxin. It is concluded that these spontaneous depolarizations are inhibitory postsynaptic potentials arising from spontaneous activity in inhibitory interneurones.     

Chronic morphine exposure blocks opioid effects on both the early and late inhibitory postsynaptic potentials in hippocampal CA1 pyramidal cells

The μ-opioid agonist, [

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(PL017), significantly decreased the conductance changes measured during both the early and late inhibitory postsynaptic potentials (IPSP) in CA1 pyramidal cells. Although the conductance change during the early IPSP was much larger than that during the late IPSP, the relative decrease in conductance caused by 1 μM PL017 was similar for both. Chronic morphine treatment of rats prior to hippocampal slice preparation resulted in a loss of PL017 (1 μM) effects on both the early and late IPSPs. These results suggest that opioids have an equal ability to alter both early and late IPSPs in the CA1, that these effects are equally sensitive to chronic morphine, and that these measurements are a sensitive means of determining opioid tolerance in the hippocampus.     

大鼠海马神经元培养与鉴定

探索适用于膜片钳记录的大鼠海马神经元的分离及原代培养方法,并检测其电生理特性。采用钝性分离1日龄SD大鼠双侧海马,经酶消化及吸管吹打,用含胎牛血清、马血清的DMEM体外培养,并经阿糖胞苷处理24h,第9—15d用于膜片钳全细胞模式检测神经元电生理特性。结果显示培养的海马锥体神经元表面光洁,膜片钳记录封接成功率90％,具有正常神经元的电生理及反应特性。表明本分离及原代培养方法,有益于大鼠海马锥体神经元生长,并适用于膜片钳记录。