Postischemic intravenous administration of magnesium sulfate inhibits hippocampal CA1 neuronal death after transient global ischemia in rats

OBJECTIVE: We aimed to determine an effective dose schedule for intravenously administered magnesium, to establish its neuroprotective efficacy in both pre- and postischemic treatment paradigms, and to compare the neuroprotective properties of MgSO(4) and MgCl(2). METHODS: Rats that had been subjected to the bilateral carotid artery occlusion plus hypotension model of transient forebrain cerebral ischemia received either an intravenously administered loading dose (LD) of 360 micromol/kg MgSO(4) only or an intravenously administered LD of 360 micromol/kg followed by a 48-hour intravenous infusion of MgSO(4) at either 60, 120, 240, or 480 micromol/kg/h. For evaluation of the efficacy of MgSO(4) after ischemia, the dose (LD, 360 micromol/kg; infusion, 120 micromol/kg/h) that provided maximal neuroprotection before ischemia was administered 4, 8, 12, or 24 hours after ischemia. MgCl(2) (LD, 360 micromol/kg; infusion, 120 micromol/kg/h) was administered before and 8 hours after ischemia. At 7 days after ischemia, hippocampal CA1 neurons were histologically examined for protection. RESULTS: Animals that received the LD only demonstrated 33% hippocampal CA1 neuronal survival. Animals that received the LD followed by continuous infusion of MgSO(4) at either 60, 120, 240, or 480 micromol/kg/h demonstrated 30, 80, 16, and less than 5% CA1 neuronal survival, respectively. MgSO(4) treatment commencing at 4, 8, 12, or 24 hours resulted in 82, 71, 52, and 33% CA1 neuronal survival, respectively. Preischemic and 8-hour postischemic administration of MgCl(2) resulted in 50% and less than 5% CA1 neuronal survival, respectively. CONCLUSION: These results demonstrate a neuroprotective intravenous dose of MgSO(4), which is effective when administered before or late after ischemia, and a previously uncharacterized dose-response curve for MgSO(4).     

Effects of global ischemia duration on neuronal, astroglial, oligodendroglial, and microglial reactions in the vulnerable hippocampal CA1 subregion in rats

The hippocampal CA1 neurons are selectively vulnerable to global ischemia, and neuronal death occurs in a delayed manner. The threshold of global ischemia duration that induces neuronal death has been studied, but the relationship between ischemia duration and glial death in the hippocampal CA1 area has not been fully studied. We examined neuronal/glial viability and morphological changes in the CA1 subregion after different durations of global ischemia. Global ischemia was induced in Sprague-Dawley rats by 10, 5, and 3 min of bilateral common carotid artery occlusion and hypotension. At 1-56 days after ischemia, the morphological reactions of neurons, astrocytes, oligodendrocytes, and microglia were immunohistochemically evaluated. Most of the hippocampal CA1 pyramidal neurons underwent delayed death at 3 days after 10/5 min of ischemia, but not after 3 min of ischemia. The number of astrocytes gradually declined after 10/5 min of ischemia, and viable astrocytes showed characteristic staged morphological reactions. Oligodendrocytes also showed morphological changes in their processes after 10/5 min of ischemia. Microglia transformed into a reactive form at 5 days only after 10/5 min of ischemia. These data suggest that some morphological changes in glial cells were not dependent on neuronal cell death, but their own reactions to the different severity of ischemia.     

Time window characteristics of cultured rat hippocampal neurons subjected to ischemia and reperfusion

Themolecularmechanismofneuronalinjurycausedbycerebralischemiahasnotbeenclearlyunderstood.However,studieshaveprovedthatthepatho physiologicalmechanisminvolvedisakind ofcascadeofdamageandisrelatedtoatleastfour differentmechanism,thatisexcitotoxity,periinfarct depolarization,inflammationandprogrammedcell death(PCD).Before1990s ,neurondeathcausedby cerebralischemiahadbeenthoughttobeapassive processofnecrosis.Inrecentyears,withmoreand moreresearchesinneurondeath,ourunderstandingin celldeathhasunde…     

丙泊酚对大鼠海马脑片CA1区长时程增强的影响

目的观察不同浓度丙泊酚对离体大鼠海马脑片CA1区长时程增强(LTP)的影响。方法30张海马脑片分为五组,Ⅰ、Ⅱ和Ⅲ组分别应用浓度为30、10和3μmolo/L的丙泊酚,Ⅳ组用脂肪乳,Ⅴ组不用药物作为对照。利用细胞外记录方式,以海马脑片CA1区群峰电位(PS)为观察指标,首先观察丙泊酚对CA1区基础传递的影响,待基线稳定后,记录高频刺激(HFS)后海马脑片CA1区PS的变化情况。结果Ⅰ、Ⅱ、Ⅲ组应用丙泊酚后PS降低,在持续给药后30min恢复至基线。实施HFS后,Ⅲ、Ⅳ和Ⅴ组的PS较HFS前显著升高(P<0.05,P<0.01);而Ⅰ、Ⅱ组PS与HFS前相比差异无显著意义(P>0.05)。HFS后,Ⅰ组PS显著低于Ⅱ、Ⅲ、Ⅳ和Ⅴ组(P<0.01),Ⅱ组PS也低于Ⅲ、Ⅳ和Ⅴ组(P<0.05)。结论丙泊酚可以抑制大鼠离体海马脑片CA1区LTP的形成。     

右美托咪定对全脑缺血/再灌注大鼠海马CA1区神经元GluR2蛋白表达的影响

目的 探讨右美托咪定(dexmedetomidine,Dex)预处理对全脑缺血/再灌注(ischemia/reperfusion,I/R)大鼠海马CA1区神经元GluR2蛋白[α-氨基-3-羟基-5-甲基-4-异恶唑丙酸(α-amino-3-hydroxy-5-methyl4-isoxa-zolep-propionate acid,AMPA)受体中限制Ca2+通透的亚基]表达以及学习记忆能力的影响. 方法 按照随机数字表法将48只雄性SD大鼠分为4组(每组12只):假手术组(S组),I/R组,Dex组(D组),育亨宾+Dex组(YD组).使用四血管阻断法制作脑I/R模型,脑缺血5 min后行再灌注.D组于缺血前30 min腹腔注射Dex 100 μg/kg,YD组于对应时间点同时腹腔注射Dex 100 μg/kg和育亨宾0.1 mg/kg,S组和I/R组腹腔注射等量生理盐水.各组于再灌注后7d进行Morris水迷宫实验,测试各组大鼠的空间学习记忆能力.于再灌注72 h时,处死大鼠并分离海马CA1区,应用Western blot法测定GluR2蛋白的表达. 结果 与S组比较,I/R组大鼠的逃避潜伏期明显延长(P＜0.05)、停留目标象限时间[(32.1±5.0)s比(48.7±5.5)s]和穿越平台次数[(1.5±0.8)次比(5.0±1.2)次]明显减少(P＜0.05);与I/R组比较,D组的逃避潜伏期明显缩短(P＜0.05),停留目标象限时间[(40.6±2.1)s比(32.1±5.0)s]和穿越平台次数[(3.3 ±0.5)次比(1.5±0.8)次]明显增加(P＜0.05);与D组比较,YD组的逃避潜伏期明显延长,停留目标象限时间[(32.2±6.0)s比(40.6±2.1)s]和穿越平台次数[(1.6±0.8)次比(3.3±0.5)次]明显减少(P＜0.05);I/R组与YD组比较,差异无统计学意义(P＞0.05);I/R 72 h,I/R组大鼠海马CA1区GluR2蛋白表达显著下调(P＜0.01),D组GluR2蛋白表达下调比I/R组明显减小(P＜0.05),YD组GluR2蛋白表达水平明显低于D组(P＜0.05),YD组与I/R组比较,差异无统计学意义(P＞0.05). 结论 Dex可减轻大鼠全脑I/R的学习记忆能力障碍,其机制可能与抑制脑缺血后海马CA1区GluR2蛋白表达的下调有关.     

异丙酚或依托咪酯对戊四唑诱发大鼠海马CA1区神经元动作电位和突触传递的影响

目的探讨异丙酚或依托咪酯对戊四唑诱发大鼠海马CA1区神经元动作电位（APs）和突触传递的影响。方法断头法分离60只Wistar大鼠海马，切片机切出400μm厚度的海马脑片，随机分为4组：戊四唑组（P组）、戊四唑＋脂肪乳剂组（PI组）、戊四唑＋异丙酚组（PP组）、戊四唑＋依托眯酯组（PE组）。全细胞电流钳记录海马CA1区锥体神经元APs发放频率，全细胞电压钳记录电刺激Schaeffer侧支，联合纤维诱发的CA1区锥体神经元兴奋性突触后电流（EPSCs）的幅值。结果与基础值比较，加入戊四唑后4组大鼠海马CA1区神经元APs发放频率增加，EPSCs幅值下降（P〈0．05）；与加入戊四唑后比较，加入异丙酚或依托咪酯后APs发放频率减少。EPSCs幅值回升（P〈0．05）。与P组及PI组比较．PP组加入异丙酚、PE组加入依托咪酯后APs发放频率减少，EPSCs幅值回升（P〈0．05）；P组与PI组比较、PP组与PE组比较差异均无统计学意义（P〉0．05）。结论异丙酚、依托咪酯可拮抗戊四唑诱发大鼠海马CA1区神经元动作电位的发放和突触传递。     

The interaction of temperature with thiopental and etomidate on extracellular dopamine and glutamate levels in Wistar-Kyoto rats subjected to forebrain ischemia

BACKGROUND: Many studies demonstrate an association between brain damage and the extracellular release of catecholamines and amino acids during cerebral ischemia. While the clinical value of hypothermia during periods of compromised cerebral blood flow and oxygen delivery is well established, the role of anesthetic agents is less clear. Furthermore, the interaction between these agents and hypothermia remains to be elucidated. The purpose of this study was to examine the interactive effects of temperature, sodium thiopental (STP) and etomidate (ETOM) on extracellular neurotransmitter accumulation in the rat corpus striatum during cerebral ischemia. METHODS: Animals were randomly assigned to one of six subgroups: normal saline (NS-norm, pericranial t approximately equal to 37 degrees C, and NS-hypo, t=30 degrees C), etomidate (ETOM-norm and ETOM-hypo), and sodium thiopental (STP-norm and STP-hypo). Microdialysis probes were inserted into the corpus striatum. Dopamine (DA), glutamate, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels were measured. At zero minutes, animals received a 10-min infusion of STP (3 mg x kg(-1) x min(-1)), ETOM (0.6 mg x kg(-1) x min(-1)), or NS. Prior to ischemia, animals were given either intravenous STP (10 mg x kg(-1)), ETOM (3 mg x kg(-1)), or NS in bolus form. Each animal was then subjected to 10 min of forebrain ischemia (Is1) followed by a reperfusion interval (Rep1). The entire sequence was then repeated. RESULTS: There were significant interactions between temperature and drug for DA (Is1, P=0.006, Is2, P=0.032) and its metabolites (DOPAC, Is1 P=0.01, HVA, Is1 P=0.03), and for glutamate (Is1, P=0.03, Is2 P=0.06). The nature of this interaction differed for DA and glutamate. The reduction in DA accumulation seen during hypothermia was offset by the addition of either STP or ETOM, whereas the addition of these drugs did not affect the reduced glutamate levels seen with hypothermia. During normothermia, STP and ETOM resulted in diminished DA accumulation compared to controls, yet they increased the accumulation of extracellular glutamate. CONCLUSIONS: Consistent with other studies, hypothermia was associated with diminished extracellular DA concentrations during forebrain ischemia. However, depending on the temperature condition, the addition of STP or ETOM in our forebrain ischemia model led to unexpected findings. The administration of these agents during normothermia diminished ischemia-induced DA accumulation yet resulted in significantly higher concentrations of extracellular glutamate. In contrast, STP and ETOM during hypothermia were noted to significantly offset the DA-reducing effects of hypothermia.     

Statins increase neurogenesis in the dentate gyrus, reduce delayed neuronal death in the hippocampal CA3 region, and improve spatial learning in rat after traumatic brain injury

Traumatic brain injury (TBI) remains a major public health problem globally. Presently, there is no way to restore cognitive deficits caused by TBI. In this study, we seek to evaluate the effect of statins (simvastatin and atorvastatin) on the spatial learning and neurogenesis in rats subjected to controlled cortical impact. Rats were treated with atorvastatin and simvastatin 1 day after TBI and daily for 14 days. Morris water maze tests were performed during weeks 2 and 5 after TBI. Bromodeoxyuridine (BrdU; 50 mg/kg) was intraperitoneally injected 1 day after TBI and daily for 14 days. Brain tissue was processed for immunohistochemical staining to identify newly generated cells and vessels. Our data show that (1) treatment of TBI with statins improves spatial learning on days 31-35 after onset of TBI; (2) in the non-neurogenic region of the hippocampal CA3 region, statin treatment reduces the neuronal loss after TBI, demonstrating the neuroprotective effect of statins; (3) in the neurogenic region of the dentate gyrus, treatment of TBI with statins enhances neurogenesis; (4) statin treatment augments TBI-induced angiogenesis; and (5) treatment with simvastatin at the same dose provides a therapeutic effect superior to treatment with atorvastatin. These results suggest that statins may be candidates for treatment of TBI.     

中低温体外循环对大鼠海马CA1区神经元凋亡的影响

目的 观察中低温体外循环(CPB)对大鼠海马CA1区神经元凋亡的影响及机制。方法 雄性SD大鼠27只,随机分为三组:CPB后1h组(n=6)、CPB后6h组(n=6)及假手术组(Sham组,n=5)。所有动物在咪唑安定、芬太尼麻醉后经口插管控制呼吸,置入颈静脉流出管和尾动脉输入管,肝素抗凝(500μ/kg)。CPB组采用中低温CPB(26～28℃),经尾动脉灌注、颈静脉右心房-腔静脉引流,灌流量160ml·kg~(-1)·min~(-1),总转流时间2h,Sham组操作同CPB术后1h组,但不经历CPB,三组持续监测动脉压、ECG及动脉血气。CPB后1h组、CPB后6h组分别在术后1、6h时处死大鼠,4％多聚甲醛灌注固定后取大脑组织,TUNEL法检测神经元凋亡,并用电子显微镜观察神经元超微结构变化,用免疫组化法检测海马CA1区神经元bax和bcl-2蛋白表达。结果 与Sham组比较,CPB后1h组bax和bcl-2蛋白表达增强,CPB后6h组bax表达增强、bcl-2蛋白表达减弱(P<0.05);与CPB后1h组比较,CPB后6h组bax表达增强、bcl-2蛋白表达减弱(P<0.05)。与Sham组比较,CPB后1h、CPB后6h组bax/bcl-2比值、神经元凋亡率升高,CPB后6h组bax/bcl-2比值、神经元凋亡率高于CPB后1h组(P<0.05)。电镜下CPB后1h组海马CA1区神经元部分线粒体肿胀、空泡变性、嵴减少或消失;CPB后6h组可见少量神经元变性固缩、核不规则、核     

乳化异氟醚预处理对大鼠局灶性脑缺血再灌注时海马CA1区神经元凋亡的影响

目的 评价乳化异氟醚预处理对大鼠局灶性脑缺血再灌注时海马CA1区神经元凋亡的影响.方法 健康成年雄性SD大鼠48只,体重250～300 g,月龄4～6月,采用随机数字表法,将大鼠随机分为6组(n=8),假手术组(S组)腹腔注射生理盐水10.5 ml/kg,24 h后只分离血管,不置入线栓;缺血再灌注组(I/R组)和乳化异氟醚预处理组(EI组)分别腹腔注射生理盐水或8%乳化异氟醚10.5 ml/kg(120 mg/ml);LY294002+乳化异氟醚预处理组(L+EI组)缺血侧侧脑室注射LY294002(磷脂酰肌醇-3激酶特异性抑制剂)25 mmol/L 5 μl,30 min后腹腔注射8%乳化异氟醚10.5 ml/kg;LY294002组(L组)和DMSO(LY294002溶剂)组缺血侧侧脑室注射LY294002 25 mmol/L(5 μl)或DMSO 5 μl.于给 药后24 h采用大脑中动脉缺血2 h恢复再灌注的方法制备局灶性脑缺血再灌注模型.于再灌注24 h时行神经功能缺陷评分,检测海马CA1区神经元凋亡情况和磷酸化丝氨酸-苏氨酸蛋白激酶(p-Akt)表达,观察海马CA1区病理学改变.结果 与S组比较,其余各组神经功能缺陷评分、凋亡细胞计数升高.p-Akt表达上调(P＜0.05);与I/R组比较,EI组神经功能缺陷评分、凋亡细胞计数降低,p-Akt表达上调(P＜0.05),L+EI组、L组、DMSO组上述各指标差异无统计学意义(P＞0.05);与EI组比较,L+EI组神经功能缺陷评分、凋亡细胞计数升高,p-Akt表达下调(P＜0.05).EI组病理学损伤程度明显轻于I/R组,L+EI组、L组、DMSO组与I/R组相似.结论 乳化异氟醚预处理可减少大鼠局灶性脑缺血再灌注时海马CA1区神经元凋亡,其神经元保护作用与PI3K/Akt通路激活有关.

Abstract：

Objective To investigate the effect of preconditioning with emulsified isoflurane (eISO) on neuronal apoptosis in hippocampal CA1 region induced by focal cerebral ischemia-reperfusion (I/R) injury in rats. Methods Forty-eight healthy adult male SD rats weighing 250-300 g were randomly divided into 6 groups (n = 8 each): sham operation group (group S); I/R group; eISO + I/R group (group EI); LY294002 (a specific PI3K inhibitor) + eISO + I/R group (group L+ EI); LY294002 + I/R group (group L) and DMSO (solvent for LY294002) + I/R group (group DMSO). Focal cerebral I/R was induced by 2 h middle cerebral artery occlusion ( MCAO). A nylon thread (0.26 mm in diameter) with rounded tip was inserted into internal carotid artery and advanced cranially until resistance was met (depth of insertion about 18-20 mm) . eISO 10.5 ml/kg (120 mg/ml) was injected intraperitoneally (IP) in groups EI and L+ EI. LY294002 (25 mmol/L) 5 pi was injected into cerebral ventricle on the ischemic side in group L + EI ( at 30 min before eISO) and group L. DMSO 5 μl was injected into the cerebral ventricle on ischemic side before MCAO in group DMSO. Neurologic deficit was assessed and scored (0 = normal, 4 = unconscious) at 24 h of reperfusion. The animals were then killed and their brains were removed for detection of neuronal apoptosis (by TUNEL) and p-Akt expression (by immuno-histochemistry) in hippocampal CA1 region. Results Cerebral I/R significantly increased the neurologic deficit scores, the number of apoptotic cells and p-Akt expression in group I/R as compared with group S. Preconditioning with elSO attenuated the I/R-induced increase in neurologic deficit scores and number of apoptotic cells but further increased p-Akt expression. The neuroprotective effect of eISO preconditioning against I/R-induced changes was counteracted by LY294002. Conclusion eISO preconditioning can attenuate focal cerebral I/R-induced neuronal apoptosis in rats by activating PI3K/Akt pathway.     

短暂性脑缺血对老年大鼠海马神经元凋亡的影响

目的 探讨短暂性脑缺血对老年大鼠海马神经元凋亡的影响。方法 健康老年雄性Wistar大鼠100只，按Pusinelli方法建立四动脉阻断法全脑缺血模型，随机分为4组（n=25）：脑缺血1min组（I1组）、脑缺血3min组（I3组）、脑缺血5min组（15组）和假手术组（C组）。每组均于再灌注12h、1d,2d、3d和7d各随机处死5只大鼠。随机取其中4只大鼠的海马组织制作石蜡切片，另1只大鼠断头处死后，冰上提取海马CAl区脑组织，制作电镜标本。透射电镜观察神经元超微结构，TUNEL法检测神经元凋亡，免疫组织化学法检测caspase．3的表达。结果 各组于光镜和电镜下均可见凋亡神经元。与C组、I1组相比，I3组、I5组凋亡细胞数和caspase-3表达阳性细胞数均增高（P〈0．05）；与I3组相比，I5组凋亡细胞数和caspase-3表达阳性细胞数均增高（P〈0．05）。结论 脑缺血3～5min对老年大鼠不产生预处理的效果，可引起脑神经元凋亡。     

低浓度利多卡因对大鼠海马CA1区缺氧神经元持续钠电流的影响

目的观察低浓度利多卡因对大鼠海马CA1区缺氧神经元持续钠电流的影响,探讨其对缺血脑损伤保护作用的机制。方法酶消化法急性分离SD大鼠海马CA1区锥体细胞,随机分为7 组(n=10):缺氧组(C组)、利多卡因1μmol·L-1组(L1组)、3μmol·L-1组(L2组)、6μmol·L-1组(L3组)、10 μmol·L-1组(L4组)、20μmol·L-1组(L5组)、30μmol·L-1组(L6组)。以全细胞膜片钳技术记录各组缺氧前持续钠电流的基础值后,C组以无糖缺氧灌流液、L1-6组以含有不同浓度利多卡因的无糖缺氧灌流液在20 s内快速置换灌流液,建立体外神经元缺氧模型。记录缺氧5 min时各组神经元的持续钠电流。结果与基础值比较,各组神经元在缺氧5 min时持续钠电流均增大(P<0.01)。在缺氧5 min 时,L1-6组持续钠电流均低于C组,L2-6组均低于L1组,L3-6组均低于L2组,L4-6组均低于L3组(P< 0.01)。结论低浓度利多卡因能抑制大鼠海马CA1区神经元缺氧引起的持续钠电流增加,该作用在10 μmol·L-1时达到最大。     

异丙酚对大鼠海马CA1缺血神经元持续钠电流的影响

目的 探讨异丙酚对大鼠海马CA1缺血神经元持续钠电流的影响。方法 酶消化法急性分离SD大鼠海马CA1锥体细胞,通过低氧和无糖法制备神经元缺血模型,全细胞膜片钳技术记录异丙酚对缺血神经元持续钠电流的影响。结果 神经元缺血5 min后持续钠电流显著增强。异丙酚10μmol/L和100μmol/L均能明显抑制缺血引起的持续钠电流增强(与0μmmol/L组比,P<0.01),此作用为异丙酚100μmol/L较10μmol/L儿更强(P<0.05)。结论 异丙酚能够抑制体外脑缺血时海马神经元持续钠电流,这可能是其产生脑保护作用的机制之一。     

Effect of fentanyl on ischemic depolarization and ischemic neuronal damage of hippocampal CA1 in the gerbil

Purpose  

Temporary brain ischemia occurring during surgery under general anesthesia may induce the death of neuronal cells and cause severe neurological deficits. On the other hand, it is not clear whether μ-opioid receptor agonists promote ischemic brain injury. It is known that duration of ischemic depolarization affects the degree of neuronal damage. However, the effects of fentanyl during brain ischemia on ischemic depolarization have not been investigated. Therefore, in the current study, the effects of fentanyl on ischemic neuronal damage and ischemic depolarization were quantitatively evaluated.     

Effect of isoflurane on neuronal apoptosis in rats subjected to focal cerebral ischemia

Although isoflurane can reduce ischemic neuronal injury after short postischemic recovery intervals, this neuroprotective efficacy is not sustained. Neuronal apoptosis can contribute to the gradual increase in infarct size after ischemia. This suggests that isoflurane, although capable of reducing early neuronal death, may not inhibit ischemia-induced apoptosis. We investigated the effects of isoflurane on markers of apoptosis in rats subjected to focal ischemia. Fasted Wistar-Kyoto rats were anesthetized with isoflurane and randomly allocated to awake (n = 40) or isoflurane (n = 40) groups. Animals in both groups were subjected to focal ischemia by filament occlusion of the middle cerebral artery for 70 min. Pericranial temperature was servo-controlled at 37 degrees C +/- 0.2 degrees C throughout the experiment. In the awake group, isoflurane was discontinued and the animals were allowed to awaken. In the isoflurane group, isoflurane anesthesia was maintained at 1.5 MAC (minimum alveolar anesthetic concentration). Animals were killed 7 h, 1 day, 4 days, or 7 days after reperfusion (n = 10/group/time point). The area of cerebral infarction was measured by image analysis in a hematoxylin and eosin stained section. In three adjacent sections, apoptotic neurons were identified by TUNEL staining and immunostaining for active caspase-9 and caspase-3. Infarct size was smaller in the isoflurane group than the awake group 7 h, 1 day, and 4 days after reperfusion (P < 0.05). However, this difference was absent 7 days after reperfusion. The number of apoptotic (TUNEL, caspase-3, and caspase-9 positive) cells 1 day after ischemia was significantly more in the awake versus isoflurane group. After a recovery period of 4 or 7 days, the number of apoptotic cells in the isoflurane group was more than in the awake group. After 7 days, the number of caspase-3 and -9 positive neurons was more in the isoflurane group (P < 0.05). The data indicate that isoflurane delays but does not prevent the development of cerebral infarction caused by ischemia. Isoflurane reduced the development of apoptosis early after ischemia but did not prevent it at later stages of postischemic recovery. IMPLICATIONS: The effect of isoflurane on neuronal apoptosis was investigated in rats subjected to focal cerebral ischemia. In isoflurane-anesthetized animals, ischemia-induced apoptosis occurred during the later stages of postischemic recovery. Isoflurane did not inhibit postischemic neuronal apoptosis.     

咪达唑仑对大鼠海马CA1区突触传递的影响

目的 探讨咪达唑仑对大鼠海马CA1区突触传递的影响.方法 成年雄性Wistar大鼠35只,体重190～220 g,随机分为7组(n=5),单刺激下4组:对照组(C_1组)、荷包牡丹碱组(B_1组)、咪达唑仑组(M_1组)和荷包牡丹碱+咪达唑仑组(BM组);配对刺激下3组:对照组(C_2组)、荷包牡丹碱组(B_2组)和咪达唑仑组(M_2组).单刺激条件:刺激方波波宽0.1 ms、频率0.033 Hz,配对刺激条件:刺激方波波宽0.1 ms、频率0.033 Hz,两个配对刺激间隔30 ms,刺激强度为诱发兴奋性突触后电位(EPSP)峰值刺激强度的50%.C_(1,2)组和M_(1,2)组记录EPSP幅值的基础值,随后分别腹腔注射生理盐水3 ml/kg和咪达唑仑3 mg/kg;B_(1,2)组和BM组记录EPSP幅值的基础值,随后腹腔注射荷包牡丹碱2 mg/kg,20 min后BM组腹腔注射咪达唑仑3 mg,/kg.各组给药结束后再记录60 min,每10 min为一时段.单刺激下计算各时间段EPSP幅值与基础值的比值即相对幅值,配对刺激下记录两个配对刺激下的EPSP幅值(分别为E_1和E_2),计算E_2/E_1.结果 与C_1组比较,M_1组EPSP相对幅值降低(P<0.05或0.01),B_1组和BM组差异无统计学意义(P>0.05);与C_2组比较,B_2组E_2及E_2/E_1升高(P<0.05),E_1差异无统计学意义(P>0.05),M_2组E_1、E_2及E_2/E1_均降低(P<0.05);与B_2组比较,M_2组E_1、E_2及E_2/E_1均降低(P<0.05).结论 咪达唑仑可抑制大鼠海马CA1区兴奋性突触传递,呈可逆性,其机制可能与增强γ-氨基丁酸(GABA)能性突触前抑制性回路的兴奋性有关,而非直接影响GABA_A受体功能状态.     

Effects of neuroprotective cocktails on hippocampal neuron death in an in vitro model of cerebral ischemia

Cocktails of neuroprotectants acting at different parts of the ischemic injury cascade may have advantages over single agents. This study investigated, singly and in combination, the neuroprotective efficacy of an energy substrate (3.5 mM fructose 1,6-bisphosphate, FBP), an antagonist of NMDA receptors (1 and 10 microM MK-801), a free-radical scavenger (100 microM ascorbate), an adenosine A1 receptor agonist (10 microM 2-chloroadenosine), and an inhibitor of neurotransmission (2% isoflurane). These agents were evaluated for their ability to prevent loss and morphologic damage of CA1 neurons in rat hippocampal slices when these agents were administered during 30 minutes in vitro ischemia (combined oxygen/glucose deprivation at 37 degrees C) followed by 5 hours of recovery. Ten microM MK-801, alone or in combination with the other compounds, prevented loss of CA1 neurons and preserved their histologic appearance. Isoflurane, which prevents glutamate receptor-dependent cell death in this model, was also protective. Protection against neuron loss was also found when a subtherapeutic concentration of MK-801 (1 microM) was combined with 2-chloroadenosine (which indirectly causes NMDA receptor suppression), but not FBP or ascorbate. The authors conclude that in this model, the strategy of antagonizing NMDA receptors appears more protective than fructose-1,6-bisphosphate, 2-chloroadenosine or ascorbate.     

Long-term effects of hypothermia on neuronal cell death and the concentration of apoptotic proteins after incomplete cerebral ischemia and reperfusion in rats

BACKGROUND: The present study investigates the long-term effects of postischemic hypothermia on neuronal cell damage and concentration changes of apoptotic proteins after cerebral ischemia. METHODS: Sixty-four Sprague-Dawley rats were anesthetized, intubated and ventilated with 2.0 Vol% isoflurane and 70% N2O/O2. After preparation the animals were randomly assigned to the following groups: group 1 (n = 32, fentanyl-N2O/normothermia 37.5 degrees C), and group 2 (n = 32, fentanyl-N2O/hypothermia 34.0 degrees C. Ischemia (45 min) was induced by common carotid artery occlusion plus hemorrhagic hypotension (MAP = 40 mmHg). Arterial blood gases and pH were maintained constant. After 1, 3, 7, or 28 days (each n = 8) the brains were removed, frozen and cut. Neuronal damage was assessed by analyzing Bax, Bcl-2, p53, and Mdm-2 proteins, activated caspases-3-positive and eosinophilic cells. A third group (n = 8) of untreated animals served as naive controls. RESULTS: In hypothermic animals, Bax concentration was decreased by 50-70% over time compared to normothermia. On days 1 and 3, Bcl-2 was increased by 50% with hypothermia. The amount of activated caspase-3-positive cells in the ischemic hemisphere was 0.5% in the hypothermic and 1-2% in the normothermic animals. Of the hippocampal cells, 10-25% were eosinophilic in both groups over time. CONCLUSION: The present data show that hypothermia prevents an ischemia-induced increase of the pro-apoptotic protein Bax for as long as 28 days and increases the concentration of the antiapoptotic protein Bcl-2 up to 3 days compared to normothermic animals. Therefore, after cerebral ischemia, hypothermia has the sustained neuroprotective potential to shift apoptosis-related proteins towards neuronal cell survival.     

异丙酚对大鼠海马CA1区神经元兴奋性突触传递的影响

目的 研究异丙酚对大鼠海马CA1区神经元兴奋性突触后电流（EPSC）和自发性兴奋性突触后电流（sEPSC）的影响。方法 Wistar大鼠断头后分离海马脑组织，制成400μm厚度的海马脑片，脑片随机分为5组（n=10）。脂肪乳剂Ⅰ组、异丙酚Ⅰ组、SR95531＋异丙酚组：记录EPSC10min（基础值）后分别加入10％脂肪乳剂90μl,1％异丙酚90μl（相当于100μmol／L）、10μmol／LSR95531＋100μmol/L异丙酚，继续记录EPSC40min，分析EPSC幅值的变化。脂肪乳剂Ⅱ组、异丙酚Ⅱ组：细胞破膜后稳定10．15min，分别加入10％脂肪乳剂90出和1％异丙酚90出，记录sEPSC40min，分析sEPSC频率、幅值和半衰期的变化。膜钳制电压均为-70mV。结果 与基础值比较，给药后脂肪乳剂Ⅰ组和SR95531＋异丙酚组EPSC幅值差异无统计学意义，异丙酚Ⅰ组EPSC幅值降低；给药后异丙酚Ⅰ组EPSC幅值比脂肪乳剂Ⅰ组降低（P〈0．05）。与脂肪乳剂Ⅱ组比较，异丙酚Ⅱ组sEPSC的频率、幅值降低、半衰期缩短（P〈0．05）。结论 异丙酚主要通过增强大鼠海马CA1区神经元突触前膜和突触后膜的GABA．受体活性，产生突触前抑制和突触后抑制，从而抑制兴奋性突触传递。