皮质酮对大鼠海马CA1区长时程抑制的影响

目的 观察皮质酮对大鼠海马CA1区锥体神经元产生的长时程抑制(LTD)的影响.方法 断头法分离Wistar大鼠海马半脑,切片机切出400μm厚度的海马脑片.对照组不加任何药品,皮质酮组、D-APV组和D-APV 皮质酮组的脑片分别以10μmol/L皮质酮、50μmol/L D-APV和50μmol/L D-APV 10μmol/L皮质酮预孵60min.记录基础兴奋性突触后电流(EPSC)10min,然后给予低频刺激(LFS),记录LTD的表达情况.结果 对照组给予LFS后,产生LTD,LFS后EPSC值为基础值的58.2 %(P＜0.05);皮质酮组给予LFS后EPSC值为基础值的45.4 %(P＜0.05),明显低于对照组(P＜0.05);给予NMDA受体特异性拮抗剂D-APV后,D-APV组和D-APV 皮质酮组大鼠海马CA1区LFS不能诱发LTD.结论 该实验条件诱发的LTD是NMDA受体依赖型的,10 μmol/L皮质酮使大鼠海马CA1区锥体神经元LTD表达增强.     

三环哌酯对海马脑片神经元烟碱受体及谷氨酸能兴奋性突触传递的阻断作用

目的研究中枢抗胆碱药三环哌酯(TCPN)对海马脑片神经元烟碱受体(nAChR)及谷氨酸能兴奋性突触传递的阻断作用。方法采用海马脑片盲法全细胞记录技术,以自发兴奋性与抑制性突触后电流(sEPSC和sIPSC)为观测指标。结果TCPN(10～500μmol.L-1)浓度依赖地对抗nAChR激动剂碘化二甲基苯基哌嗪(DMPP)增强海马脑片CA1锥体神经元sEPSC的作用,500μmol.L-1完全阻断DMPP的增强作用。同时,TCPN浓度依赖地直接抑制神经元的sEPSC。但TCPN不抑制神经元的sIPSC,也不阻断DMPP对sIPSC的增强作用。结论TCPN对海马脑片神经元突触传递的影响具有双重作用,既能通过阻断谷氨酸能突触前末梢nAChR而抑制sEPSC,同时还能直接抑制sEPSC。     

海洛因急、慢性给药状态下大鼠海马CA1区生物电活动的记录

目的:记录海洛因慢性给药戒断期大鼠离体海马脑片和海洛因急性灌流正常大鼠离体海马脑片生物电活动,观察其特征性变化。方法:制作海洛因慢性给药戒断大鼠模型及其海马离体脑片,正常组大鼠海马脑片用两种浓度海洛因急性灌流,分别记录海马CA1区神经元的电活动。结果:慢性给药戒断状态:大鼠海马CA1神经元的被动电学性质与各组比较差异无显著性,但锋电位的半幅时程、10%-90%衰减时间显著缩短(P<0.05,P<0.01);给予1.6-2.0nA胞内电流刺激时,放电频率较对照组增加(P<0.01);CA1区神经元兴奋性突触后电位(EPSP)幅值显著增强(P<0.01)。急性灌流用药:0.3mmol.L-1海洛因灌流,使膜电位和阈值绝对值减小(P<0.05,P<0.01),锋电位的半幅时程、10%-90%衰减时间显著延长(P<0.05,P<0.01);膜斜率电阻增大(P<0.01),EPSP幅值显著下降(P<0.01)。结论:海洛因急、慢性给药状态下,大鼠海马CA1区生物电特性存在着明显的差别。     

石杉碱甲对大鼠海马脑片CA1神经元θ节律及长时程增强的影响

目的:研究石杉碱甲(HupA)对大鼠海马脑片CA1锥体神经元θ节律、长时程增强的影响,以分析其增强学习记忆功能的神经细胞电生理机制。方法:应用大鼠海马脑片神经元细胞内记录技术,观察石杉碱甲对大鼠海马脑片的CA1锥体神经元θ节律、长时程增强的影响。结果:(1)未用药组出现膜电位振荡前后4～10Hz(θ节律)功率分量之和无显著性差异,但在HupA(1μmol·L-1)灌流15min后出现膜电位振荡,与用药前没有膜电位振荡的4～10Hz功率分量之和配对t检验比较有显著差异(n=3,P<0.005)。(2)在LTP期间,对照组EPSP幅度在强直刺激后30min显著性的升高(P<0.05),而HupA组在强直刺激后15min即出现显著性升高(P<0.01)。结论:HupA可增加大海马锥体神经元在θ频率范围内的功率分量,并易化LTP的诱发,这可能是其增强学习记忆功能的细胞电生理机制之一。     

依托咪酯对大鼠海马CA1区兴奋性突触后电流的影响

目的 探讨依托咪酯对大鼠海马CA1区兴奋性突触后电流的影响.方法 将32只Wistar大鼠海马脑片均分为四组:脂肪乳剂组;10μM依托咪酯组;荷包牡丹碱+10μM依托咪酯组;士的宁+10μM 依托咪酯组.记录用药前和40 min后膜钳制电压为-70 mV时的兴奋性突触后电流(EPSC)幅值.结果 在膜钳制电压为-70 mV时,脂肪乳剂对CA1区锥体神经元细胞EPSC幅值无明显影响,而10μM依托咪酯可明显降低EPSC幅值(P＜0.05).应用荷包牡丹碱预孵脑片可完全消除10μM依托咪酯对大鼠海马CA1区EPSC值的抑制作用(P＜0.05).在应用士的宁预孵脑片后,10μM依托咪酯可使EPSC值下降约16.2％;但与依托咪酯组相比,该抑制作用被明显削弱(P＜0.05).结论 依托咪酯可能主要通过增强突触 γ-氨基丁酸A受体功能而抑制兴奋性突触活动.甘氨酸受体在其中亦起到一定的调节作用.     

丙泊酚对大鼠海马CA1区突触传递长时程抑制的作用

目的研究丙泊酚对大鼠海马CA1区兴奋性突触反应及突触可塑性的影响。方法取3周龄Wistar大鼠,快速断头取脑,用振动切片机切取400μm厚的海马脑片,电刺激靠近海马CA1区的Schaffer纤维,用全细胞膜片钳技术记录CA1区锥体细胞的兴奋性突触后电流(excitatory post-synaptic current,EPSC)。循环液中加入不同浓度的丙泊酚,观察其对EPSC的影响。然后给与低频刺激(900pulse,3Hz)诱导长时程抑制(long-termdepression,LTD),并观察丙泊酚对LTD诱导的影响。结果丙泊酚呈剂量依赖性地抑制EPSC,其作用可被印防己毒素(picrotoxin)阻断;丙泊酚可易化由N-甲基-D-门冬氨酸(N-methyl-D-aspartate,NMDA)受体介导的LTD的诱导。结论丙泊酚可影响大鼠海马CA1区的兴奋性突触传递和突触可塑性,从而对大鼠的学习和记忆产生影响。     

烟碱与强直刺激诱导大鼠海马CA1区的长时程增强具有不同机制(英文)

目的:研究烟碱与强直刺激在海马CA1区诱导的长时程增强是否具有不同机制。方法:细胞外记录离体海马脑片CA1区锥体细胞层群体峰电位。结果:烟碱10μmol/L可易化强直刺激诱导的长时程增强,同样,强直刺激也可易化烟碱10μmol/L诱导的长时程增强。MK-801 10μmol/L或N~Gnitro-L-arginine methyl ester(L-NAME)20μmol/L可阻断强直刺激诱导的长时程增强,但不能抑制烟碱10μmol/L诱导的长时程增强。结论:烟碱与强直刺激在海马CA1区诱导的长时程增强具有不同的突触机制。     

三七总皂苷对海马CA1区长时程增强效应的影响

三七总皂苷(Panax notoginseng saponins，PNS)是从传统中药三七的根中提取的主要有效成分， 具有改善血液循环、 耐缺氧、 改善记忆力、 抗衰老等多方面的生理活性。本研究采用“盲法”全细胞膜片钳技术观察PNS对大鼠海马CA1区锥体神经元长时程增强效应(LTP)的影响， 以分析其增强学习记忆功能的神经电生理机制。以断头法分离Wistar大鼠(3～4周)海马半脑， 用切片机切出400 μm厚度的海马脑片， 以全细胞电压钳制方式记录CA1区锥体细胞的兴奋性突触后电流(EPSCs)， 给予高频刺激HFS(100 Hz)诱导LTP， 分析PNS对大鼠海马CA1区EPSCs和LTP的影响。结果表明， PNS(0.1～0.4 g·L^-1)能显著抑制EPSCs(P<0.05)， 且对海马CA1区LTP无易化作用； 但PNS(0.04～0.05 g·L^-1)不影响CA1区的EPSCs基础突触传递(P>0.05)， 却可以增强HFS诱发的LTP(P<0.05)。上述结果提示， PNS(0.04～0.05 g·L^-1)能易化海马CA1区锥体神经元的长时程增强效应，该作用应是其增进学习记忆力的神经电生理机制。     

盐酸埃他卡林对大鼠海马神经元谷氨酸受体功能及突触活动的影响

目的 :研究盐酸埃他卡林 (Ipt)对脑神经元谷氨酸受体功能及突触活动的影响。方法 :采用原代培养的大鼠海马神经元 ,应用膜片钳全细胞记录技术 ,记录Ipt对培养的海马神经元谷氨酸或天冬氨酸(NMDA)诱发电流及神经元突触后电流的影响。结果 :Ipt(1～ 1 0 0 μmol·L- 1)可浓度依赖性地对抗培养的海马神经元谷氨酸或NMDA诱发电流 ,并为ATP敏感性钾通道拮抗剂格列本脲 30 μmol·L- 1所对抗。Ipt抑制培养的海马神经元之间突触联系形成的自发兴奋性突触后电流 ,降低其发放频率 ,抑制其电流幅度 ;但对微小兴奋性突触后电流无显著性影响。结论 :Ipt可阻断脑神经元谷氨酸受体功能 ,抑制脑神经元谷氨酸的兴奋性突触传递 ,其作用与ATP敏感性钾通道相关     

山奈酚对急性短暂缺氧时大鼠海马CA1神经元电压依赖性钾通道的作用

目的研究山奈酚对正常和急性短暂缺氧时大鼠海马CA1锥体神经元电压依赖性钾通道的作用.方法急性分离大鼠海马CA1区锥体神经元,采用全细胞记录,用含有氰化钾(KCN)60μmol·L-1的标准外液灌流模拟细胞缺氧,观察山奈酚对正常和缺氧时海马CA1区神经元电压依赖性钾通道的作用.结果山奈酚对正常和缺氧时海马CA1神经元电压依赖性K 电流有明显的抑制作用,可同时抑制瞬时外向型钾电流(IA)和延迟整流性钾电流(Ik),具有浓度依赖和电压依赖性;山奈酚对IA的半数抑制浓度(IC50)约为50μmol·L-1,对IK的IC50约为80μmol·L-1.结论山奈酚对正常和缺氧时大鼠海马CA1神经元电压依赖性钾通道有抑制作用,其对钾通道的抑制作用可能参与脑缺血保护.     

Pertussis toxin prevents neomycin-induced calcium-dependent electrophysiological effects in rat hippocampal slices

1. The influence of pertussis toxin has been studied on the effects of neomycin on CA1 field potentials in rat hippocampal slices in order to determine a role played by G protein in the modulation of synaptic transmission by the drug.2. Neomycin (500 μM), within 30 min significantly (P < 0.01) decreased the magnitude of the somatic CA1 excitatory postsynaptic potentials (EPSP) and population spike (PS) in control hippocampal slices.3. Neomycin (500 μM), within 30 min failed to significantly affect the magnitude of the somatic CA1 EPSP and PS in slices obtained from animals treated intracerebroventricularly (ICV) with 1–2 μg of pertussis toxin 3 days before.4. The results demonstrated that pertussis toxin prevents some electrophysiological effects of neomycin, suggesting a role of G protein in the modulation of the aminoglycoside antibiotic on central synaptic transmission.     

Selective enhancement of AMPA receptor-mediated function in hippocampal CA1 neurons from chronic benzodiazepine-treated rats

Two days following one-week administration of the benzodiazepine, flurazepam (FZP), rats exhibit anticonvulsant tolerance in vivo, while reduced GABA(A) receptor-mediated inhibition and enhanced EPSP amplitude are present in CA1 pyramidal neurons in vitro. AMPA receptor (AMPAR)-mediated synaptic transmission in FZP-treated rats was examined using electrophysiological techniques in in vitro hippocampal slices. In CA1 pyramidal neurons from FZP-treated rats, the miniature excitatory postsynaptic current (mEPSC) amplitude was significantly increased (33%) without change in frequency, rise time or decay time. Moreover, mEPSC amplitude was not elevated in dentate granule neurons following 1-week FZP treatment or in CA1 pyramidal neurons following acute desalkyl-FZP treatment. Regulation of AMPAR number was assessed by quantitative autoradiography with the AMPAR antagonist, [(3)H]Ro48-8587. Specific binding was significantly increased in stratum pyramidale of hippocampal areas CA1 and CA2 and in proximal dendritic fields of CA1 pyramidal neurons. Regulation of AMPAR subunit proteins was examined using immunological techniques. Neither abundance nor distribution of GluR1-3 subunit proteins was different in the CA1 region following FZP treatment. These findings suggest that enhanced AMPAR currents, mediated at least in part by increased AMPAR number, may contribute to BZ anticonvulsant tolerance. Furthermore, these studies suggest an interaction between GABAergic and glutamatergic systems in the CA1 region which may provide novel therapeutic strategies for restoring BZ effectiveness.     

Mu opioid receptor activation normalizes temporo-ammonic pathway driven inhibition in hippocampal CA1

The hippocampus of the mammalian brain is important for the formation of long-term memories. Hippocampal-dependent learning can be affected by a number of neurotransmitters including the activation of μ-opioid receptors (MOR). It has been shown that MOR activation can alter synaptic plasticity and network oscillations in the hippocampus, both of which are thought to be important for the encoding of information and formation of memories. One hippocampal oscillation that has been correlated with learning and memory formation is the 4-10 Hz theta rhythm. During theta rhythms, inputs to hippocampal CA1 from CA3 (Schaffer collaterals, SC) and the entorhinal cortex (perforant path) can integrate at different times within an individual theta cycle. Consequently, when excitatory inputs in the stratum lacunosum-moleculare (the temporo-ammonic pathway (TA), which includes the perforant path) are stimulated approximately one theta period before SC inputs, the TA can indirectly inhibit SC inputs. This inhibition is due to the activation of postsynaptic GABA(B) receptors on CA1 pyramidal neurons. Importantly, MOR activation has been shown to suppress GABA(B) inhibitory postsynaptic potentials in CA1 pyramidal neurons. Therefore, we examined how MOR activation affects the integration between TA inputs and SC inputs in hippocampal CA1. To do this we used voltage-sensitive dye imaging and whole cell patch clamping from acute hippocampal slices taken from young adult rats. Here we show that MOR activation has no effect on the integration between TA and SC inputs when activation of the TA precedes SC by less than one half of a theta cycle (<75 ms). However, MOR activation completely blocked the inhibitory action of TA on SC inputs when TA stimulation occurred approximately one theta cycle before SC activation (>150 ms). This MOR suppression of TA driven inhibition occurred in both the SC input layer of hippocampal CA1 (stratum radiatum) and the output layer of CA1 pyramidal neurons (stratum pyramidale). Thus MOR activation can have profound effects on the temporal integration between two primary excitatory pathways to hippocampal CA1 and subsequently the resultant output from CA1 pyramidal neurons. These data provide important information for understanding how acute or chronic MOR activation may affect the integration of activity within hippocampal CA1 during theta rhythm.     

羟丁酸钠在大鼠海马脑片缺氧/复氧损伤中的保护作用机制

目的：研究羟丁酸钠（SO）在大鼠海马脑片缺氧/复氧（H/R）损伤中的保护作用,揭示SO在缺血性脑损伤中的保护作用机制。方法：采用大鼠海马脑片H/R损伤模型。设正常对照组,H/R组,SO1、10、100μmol/L组,NCS-382100μmol/L＋SO100μmol/L（NCS-382＋SO）组、NCS-356100μmol/L（NCS-356）组。测定脑片孵育液中乳酸脱氢酶（LDH）释放率,γ-氨基丁酸（GABA）、谷氨酸（Glu）含量;脑片进行TTC染色计算组织损伤百分率;HE染色观察组织病理形态学变化,流式细胞仪测定细胞内钙;酶组织化学法检测一氧化氮合酶（NOS）的表达。结果：SO明显降低H/R海马脑片LDH释放率（P〈0.01）,提高TTC染色的A490值,降低组织损伤百分率（P〈0.01）,升高GABA/Glu比值（P〈0.01）,减轻H/R所致的组织病理损伤。H/R组脑片细胞内钙荧光强度和NOS阳性神经元明显高于正常对照组（P〈0.01）;SO100μmol/L组、NCS-356组细胞内钙荧光强度较H/R组显著减弱（P〈0.01）,NOS阳性神经元的数目明显减少（P〈0.01）。用γ-羟基丁酸（GHB）受体选择性阻断剂NCS-382后再使用SO,细胞内钙荧光强度、NOS阳性神经元的数目均接近H/R组。结论：SO对大鼠海马脑片H/R损伤有明显的保护作用,其机制可能与升高GABA/Glu比值,激动GHB受体抑制细胞内钙的增高及NOS的表达有关。     

The influence of helium pressure on the reduction induced in field potentials by various amino acids and on the GABA-mediated inhibition in the CA1 region of hippocampal slices in the rat

In a previous study, it was shown that helium pressure depressed excitatory synaptic transmission mediated by the Schaffer-commissural afferents and increased the intrinsic excitability of pyramidal cells, in the CA1 region of hippocampal slices in the rat. In the present study, the neurochemical bases of these changes was investigated. Various excitatory amino acids were studied under normal and up to 80 atm of helium. At normal pressure, the amino acids tested induced a decrease in the field excitatory postsynaptic potential (EPSP) and antidromic field potential of CA1 pyramidal cells. These changes probably resulted from the well known depolarizing effect of the compounds. Quisqualate is supposed to activate the synaptic receptors of the pathway tested. Since the effect of this amino acid and other agonists were not significantly affected by helium pressure, it is suggested that the depressed hippocampal synaptic potentials under pressure did not result from reduced sensitivity of synaptic receptors. On the other hand, helium pressure enhanced the action of N-methyl-D-aspartate (NMDA) and depressed the GABA-mediated inhibition of CA1 pyramidal cells. Given that the excitability of these neurones is modulated by NMDA-related events and GABA inhibition, these results indicate that both neurochemical systems were probably involved in the helium pressure-induced hyperexcitability of the cells studied.     

High calcium solutions prevent the depressant effects of aminoglycoside antibiotics on central synaptic transmission in rat hippocampal slices

1. The aminoglycoside antibiotics neomycin and streptomycin were tested on the synaptic activity of the CA1 pyramidal neuron-Schaffer collateral interconnections in rat hippocampal slices. 2. Neomycin (0.5 mM) decreased the magnitude and shifted to the right the stimulus-response curve of the somatic and dendritic excitatory postsynaptic potential (EPSP) and the somatic population spike (PS). 3. Streptomycin (1 mM) decreased the magnitude and shifted to the right the stimulus-response curve of the somatic and dendritic EPSP and the somatic PS. 4. High (+2 mM) calcium solutions were able to prevent the effects induced by the antibiotics and to shift to the left the stimulus-response curve of the 0.5 mM neomycin and 1 mM streptomycin treated hippocampal slices. 5. The data demonstrate an effect of aminoglycoside antibiotics on a central mammalian hippocampal synapses, that may depend on an interference of the drugs on calcium conductances.     

Electrophysiological actions of cyclosporin A and tacrolimus on rat hippocampal CA1 pyramidal neurons

Aim： The aim of the present study was to investigate the electrophysiological actions of cyclosporin A （CsA） and tacrolimus （FK506） on neurons in the brain, and to elucidate the relevant mechanisms. Methods： Whole-cell current-clamp recording was made in CA1 pyramidal neurons in rat hippocampal slices; whole- cell voltage-clamp recording was made in dissociated hippocampal CA1 pyrami- dal neurons of rats. Results： CsA （100 prnol/L） and FK506 （50 prnol/L） did not significantly alter the passive electrical properties of hippocampal CA 1 pyramidal neurons, but slowed down the repolarizing phase of the action potential. CsA （10-100 lamol/L） selectively inhibited the delayed rectifier K~ current （IK） in a concentration-dependent manner. CsA did not affect the kinetic properties of IX. Intracellular dialysis of CsA （100 prnol/L） had no effect on Ix. The inhibition ofIK by CsA （100 lamol/L） persisted under the low Ca^2＋ conditions that blocked the basal activity of calcineurin. Conclusion： CsA exerted calcineurin-independent inhibition on the Ix in rat hippocampal pyramidal neurons. Taken together with our previous finding with FK506, it is conceivable that the spike broadening caused by the immunosuppressant drugs is due to direct inhibition on the Ix.