铅对大鼠海马NO与NOS的影响

一氧化氮 (ｎｉｔｒｉｃｏｘｉｄｅ,ＮＯ)是近年来在中枢神经系统和其他组织中发现的一种新的信使分子 ,具有广泛的生理功能 ,尤其是在中枢神经系统细胞间信息传导中发挥着重要作用[1～ 4 ] 。本次研究试图通过对接触不同浓度铅的大鼠 ,在学习记忆功能受损后 ,测定大鼠海马回ＮＯ含量及一氧化氮合酶 (ＮＯＳ)活性 ,探讨ＮＯ与铅致大鼠学习记忆功能下降的关系 ,为阐明铅致学习记忆功能变化提供一定的理论依据。1　材料与方法1 1　实验动物及分组　ＳＤ大鼠 ,江苏省实验动物中心提供 ,体重 180～ 2 2 0ｇ。按不同剂量随机分为 0、低、中、高 4…     

急、慢性染铅对大鼠海马细胞外信号调节激酶2影响

目的探讨急、慢性染铅对大鼠海马总量细胞外信号调节激酶2(ERK2)含量的影响。方法取正常30 d大鼠海马脑片培养,分别用含20μmol/L醋酸铅和不含醋酸铅的人工脑脊液(ACSF)孵育,作为急性染铅试验标本。大鼠在体染铅,取新生大鼠海马作为慢性染铅标本。用Western印迹法测定标本总量ERK2含量。结果急性染铅实验:染铅组和对照组总量ERK2含量均无明显变化。慢性染铅实验:慢性染铅总量ERK2含量于出生20 d后显著下降。结论急性染铅对总量ERK2含量无明显影响。慢性染铅使ERK2基因表达水平下降,总量ERK2含量明显减少。     

慢性铅暴露对仔鼠脑海马NMDAR受体蛋白表达的影响

目的探讨发育期慢性铅暴露对仔鼠空间学习记忆及海马细胞NMDAR受体亚单位ε1、ε2蛋白表达的影响。方法小鼠按雌、雄随机分为3个实验组,1个对照组,每组6只。其染毒剂量为1,48,14.4mmolL醋酸铅水溶液。用水迷宫检测仔鼠空间学习能力,用免疫蛋白印迹法检测慢性铅暴露时仔鼠海马细胞的NMDAR受体亚单位ε1蛋白、ε2蛋白表达水平。结果慢性铅暴露可致仔鼠空间学习记忆能力下降,与对照组比较有显著性差异(P<0.05);海马细胞的NMDAR受体亚单位ε1(NR2A)蛋白表达水平下降(2～4W),ε2(NR2B)蛋白表达水平基本不变。结论铅致仔鼠空间学习能力下降,与其致海马细胞的NMDAR受体亚单位ε1蛋白表达水平下降有关。     

慢性染铅对小鼠海马Ca~(2+)-钙调蛋白依赖性蛋白激酶Ⅱ表达的影响

目的通过检测海马Ca2+钙调蛋白依赖性蛋白激酶Ⅱ(CaMKⅡ)基因表达来探讨慢性铅中毒影响学习记忆的分子机制。方法小鼠交配后,通过饮水饲以2.4,4.8和9.6mmol·L-1醋酸铅。小鼠子代自胚胎期始即暴露于醋酸铅。幼鼠出生后,先通过哺乳接触铅,断乳后则自行饮用与母鼠饮用浓度相同的含铅水。6周后用逆转录聚合酶链反应法观察各组小鼠海马CaMKⅡmRNA的表达。结果3个染铅组小鼠CaMKⅡmRNA水平均明显降低,并具有浓度效应关系。结论铅致CaMKⅡ基因表达水平下降。     

急、慢性铅中毒对海马CA1区长时程增强和活化的细胞外信号调节激酶2影响

目的　探讨急、慢性铅中毒对大鼠海马活化的细胞外信号调节激酶 2 (ERK2 )含量的影响及其与海马CA1区长时程增强 (LTP)的关系。方法　大鼠怀孕后分别饮用蒸馏水或 0 .2 %醋酸铅溶液 ,断乳后鼠仔则直接饮用 ,于 30d后测定LTP ,并取海马作为慢性铅中毒标本测定ERK2含量。正常 30d大鼠海马片稳定培养 2h后 ,分别用含或不含 2 0 μmol·L-1 醋酸铅的人工脑脊液孵育 ,不同时间点收集 ,作为急性铅中毒标本测定ERK2含量。用Western印迹法测定标本活化的ERK2含量。结果　高频刺激后对照组和慢性铅中毒组峰电位分别为刺激前的1 85 %和 88% ;慢性铅中毒组活化的ERK2则比对照组降低了 46 %。海马片培养中 ,对照组活化的ERK2含量基本保持不变 ,铅中毒组在 30和 60min时分别下降了 68%和 33% ,1 2 0min后恢复到正常水平。结论　活化的ERK2含量降低可能是铅中毒致使CA1区LTP不能形成的原因之一     

急性染铅对大鼠海马细胞外信号调节激酶2的影响

目的探讨急性染铅对大鼠海马总量及磷酸化的细胞外信号调节激酶2(ERK2)含量的影响。方法正常30 d大鼠,海马脑片稳定培养2 h后,分别用含20μmol/L醋酸铅及不含醋酸铅的人工脑脊液(ACSF)孵育,不同时间点收集,作为急性染铅样品,用Westem印迹法测定样品总量及磷酸化的ERK2含量。结果海马脑片培养中,对照组磷酸化的ERK2含量基本保持不变。染铅组在30和60 min时分别下降了59%和41%,120 min后恢复到接近正常水平。总量ERK2染铅组和对照组含量变化均无显著性。结论急性染铅可使磷酸化的ERK2含量在一定的时间内降低,经过一段时间后显示向正常恢复的趋势。急性染铅对总量ERK2含量无显著影响。铅通过降低ERK2的磷酸化水平影响其活力。     

氯胺酮对未成年大鼠记忆维持及海马p-CREB、c-fos表达的影响

目的 探讨氯胺酮(Ket)对未成年大鼠记忆维持能力及海马磷酸化环腺苷酸应答元件结合蛋白(p-CREB)、c-fos表达的影响及其相关性.方法 筛选合格21日龄SD大鼠72只分为正常对照组、生理盐水组、假训练组、氯胺酮组(根据时间与剂量不同分为四个亚组:Ket1a、Ket1b:分别给与氯胺酮50 mg/kg、100 mg/kg腹腔注射后3 d进行训练).生理盐水组腹腔注射等体积的生理盐水.采用Y型迷宫进行学习记忆能力测试,应用免疫组化法检测海马p-CREB、c-fos的表达.结果 与生理盐水组相比,Ket1a、Ket1b组大鼠记忆维持能力下降(P＜0.05),同时海马神经元p-CREB、c-fos的表达减少(P＜0.05);而Ket3a组、Ket3b组差异无统计学意义(P＞0.05).与正常对照组相比,其余各组海马神经元p-CREB、c-fos表达均增多(P＜0.05).而Ket1a和Ket1b或Ket3a和Ket3b组之间的行为学指标与免疫组化指标差异均无统计学意义(P＞0.05).结论 氯胺酮可能通过抑制未成年大鼠海马p-CREB、c-fos的表达短期影响其记忆维持能力.     

替米沙坦对糖尿病大鼠学习记忆及海马Ghrelin受体表达的影响

目的:观察替米沙坦对糖尿病大鼠认知功能及海马Ghrelin受体GHSR的表达影响.方法:随机将40只大鼠分为正常对照组、糖尿病组、替米沙坦组.建立链脲佐菌素(STZ)糖尿病大鼠模型,替米沙坦干预12周,Morris水迷宫测试其学习记忆能力.RT-PCR检测海马GHSRmRNA水平表达变化.免疫组化观察大鼠海马GHSR蛋白的表达.结果:替米沙坦组与糖尿病组比较,Morris水迷宫测试中潜伏期明显缩短(P<0.05),中心区停留时间百分比和通过原平台位置次数增加(P<0.05),免疫组化显示GHSR蛋白表达增加(p<0.05),RT-PCR显示GHSR在mRNA水平表达增加(P<0.05).结论:替米沙坦组上调海马GHSR的表达,替米沙坦对糖尿病大鼠学习记忆功能的改善可能与海马GHSR的表达增加有关.     

骨折对空间学习记忆和海马一氧化氮的影响

目的探讨骨折对大鼠空间学习记忆和海马一氧化氮的影响.方法采用突然暴力致大鼠股骨干骨折建立应激模型.Morri s水迷宫观察动物的学习记忆能力,检测海马一氧化氮含量及NOS活性.结果应激大鼠空间学习及记忆能力明显下降,海马一氧化氮和NOS活性显著高于对照组.结论急性应激损害大鼠空间学习和记忆能力,并可能与海马一氧化氮代谢紊乱有关.     

铅对小鼠学习记忆功能及海马区c-fos表达的影响

目的　观察铅对小鼠海马区c- fos表达及学习记忆功能的影响 ,并探讨二者的关系。方法　小鼠随机分为3个实验组和 1个对照组 ,每组 10只染铅剂量分别为 2 4、4 8和 9 6mmol L ,用跳台学习试验测试小鼠学习记忆能力 ;用RT PCR法观察各组小鼠海马区c fosmRNA的表达状况。结果　 (1) 3个染铅组小鼠跳台学习成绩显著低于对照组 (P <0 . 0 1) ;(2 ) 3个染铅组小鼠c- fosmRNA水平均明显降低 ,以对照组的值为 10 0 ,则低剂量组为 75 . 0 4± 4 .75 ,中剂量组为5 8. 3 5± 5 . 2 9,高剂量组为 42. 66± 6 .3 0 ,与对照组相比 ,P <0 .0 1。高剂量组、中剂量组与低剂量组比较 ,P <0 . 0 1。结论　慢性铅染毒间接阻碍了c- fox基因的反应性表达 ,c- fos基因表达水平的下降可能与铅致小鼠学习记忆功能损害有关。     

Effect of Acute and Chronic Lead Exposure on Apomorphine‐Induced Sniffing in Rats

Abstract: Sniffing is a behaviour which can be induced by dopamine D_1/D₂ receptor agonists. In order to test the effect of chronic lead exposure on dopamine receptor subtypes, we studied the effects of acute and chronic lead exposure on sniffing induced by apomorphine, a dopamine receptor agonist. Intraperitoneal injection of the dopaminergic receptor agonist, apomorphine (0.25–1 mg/kg), induced dose‐dependent the sniffing behaviour in rats. Acute administration of lead acetate (50, 100 and 200 mg/kg) decreased the apomorphine‐induced sniffing. Chronic lead (0.25%) exposure also decreased the apomophine response. Dopamine D₁ or D₂ receptor antagonists reduced the apomorphine effect. Lead exposure could not potentiate the blockade induced by the dopamine receptor antagonists. It is concluded that the response of lead is not mediated by alteration of dopamine receptors.     

雌性小鼠慢性小剂量染镉对子代发育的影响

本文研究了雌性小鼠的慢性低剂量染镉对子代发育的影响。结果表明,在胚胎期,镉主要引起胚胎的早期死亡,对存活胚胎的发育影响不明显。在哺乳期,镉对仔鼠的生长发育及行为等具有广泛的影响。镉对仔鼠的影响主要是由乳汁中摄取的镉所致。     

芍药苷对醋酸铅诱导海马神经元凋亡及Bcl-2/Bax蛋白表达的影响

目的 探讨芍药苷(paeoniflorin,PF)对醋酸铅诱导海马神经元凋亡及Bcl-2/Bax蛋白表达的影响。方法 分离培养胎鼠海马神经元细胞,细胞免疫荧光染色鉴定纯度。MTT测定海马神经元细胞活力以确定醋酸铅最适造模浓度及时间,同时筛选合适剂量PF干预海马神经元凋亡。依据MTT测定结果,分为空白组、模型组和20,40,80 μmol·L^-1 PF组干预海马神经元细胞,作用24 h后,加醋酸铅染毒,检测细胞色素C (cytochrome C,Cyt-C)含量、线粒体膜电位及细胞内Ca²⁺浓度。流式细胞仪检测细胞凋亡情况,Western blotting测定海马神经元细胞中caspase-3、cleaved-caspase-3、caspase-8、cleaved-caspase-8、caspase-9、cleaved-caspase-9、Bax、Bcl-2蛋白表达水平。结果 细胞免疫荧光染色鉴定结果显示分离培养的细胞为海马神经元细胞,且纯度较高。MTT测定结果显示醋酸铅最适造模浓度及时间为25 μmol·L^-1染毒24 h;PF剂量为20,40,80 μmol·L-1可显著改善海马神经元细胞活性,呈剂量依赖性。与空白组相比,模型组Cyt-C含量、凋亡率、细胞内Ca²⁺浓度显著升高(P<0.01),线粒体膜电位显著降低(P<0.01)。与模型组相比,40 μmol·L^-1 PF组和80 μmol·L^-1 PF组可降低Cyt-C含量、凋亡率、细胞内Ca²⁺浓度(P<0.05或P<0.01),升高线粒体膜电位(P<0.01),20 μmol·L^-1PF组可显著升高线粒体膜电位(P<0.05)。此外,一定剂量的PF可下调cleaved-caspase-3、cleaved-caspase-8、cleaved-caspase-9、Bax蛋白表达,上调Bcl-2蛋白表达。结论 PF可抑制醋酸铅诱导的海马神经元凋亡,可通过调控Bcl-2/Bax蛋白表达发挥神经保护作用。     

七氟烷暴露对发育大鼠海马神经元可塑性的影响及机制

目的分析七氟烷暴露对发育大鼠海马神经元可塑性的影响及其机制。方法 60只产后第7天健康仔鼠均分为对照组、3%七氟烷暴露1 h组(Sev 1 h组)和6 h组(Sev 6 h组),Sev 1 h组及Sev 6 h组大鼠分别置于用3.0%七氟烷、空气通风的密封盒中1 h及6 h,对照组接受空气,没有麻醉剂暴露;各组大鼠水迷宫实验记录逃避潜伏期、平台象限活动时间及穿越平台次数,记录大鼠新物体识别任务时间及辨别指数;Western blotting法分析大鼠海马组织切片突触融合蛋白、人突触相关蛋白25(SNAP-25)及突触素α-突触核蛋白,高尔基染色检测树突棘密度;透射电镜观察海马突触的超微结构,记录海马脑片CA1区椎体细胞的兴奋性突触后电位(EPSP)、高频或低频刺激(HFS或LFS)后CA1区细胞长时程增强(LTP)和长时程抑制(LTD)。结果与对照组比较,Sev 6 h组探测时间和逃避潜伏期延长,平台象限区的入口数量减少,并且少于Sev 1 h组(P<0.05);新物体识别任务中,对照组辨别指数(DI)高于Sev 6 h组(P<0.05)。在Sev 6 h组中突触融合蛋白和...     

Impairment of the Ca2+‐Permeable AMPA/Kainate Receptors by Lead Exposure in Organotypic Rat Hippocampal Slice Cultures

Previous studies have demonstrated that chronic lead exposure may impair neuronal process underlying synaptic plasticity via a direct interaction with N‐methyl‐D‐aspartate (NMDA) receptors. The present study was carried out to investigate the effects of lead exposure on non‐NMDA (α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid, AMPA/kainate) receptors of rat hippocampus. Ca²⁺‐permeable AMPA/kainate receptors in organotypic slice cultures were evaluated by using cobalt uptake, a histochemical method that identifies cells expressing Ca²⁺‐permeable non‐NMDA receptors. Ten mM L‐glutamate‐induced cobalt accumulation was enriched in area CA1, area CA3 and in dentate gyrus, which was totally blocked by 100 μM DL‐2‐amino‐5‐phosphonovaleric acid (AP5) and 100 μM 6‐cyano‐7‐nitroquinoxaline‐2, 3‐dione (CNQX). Three hundred μM NMDA‐induced cobalt accumulation was in area CA1, area dentate gyrus and was blocked by AP5 or CNQX. One hundred μM AMPA had effects in area CA1, area CA3 and in dentate gyrus, which were blocked by CNQX, not by AP5. Furthermore, cobalt accumulations induced by NMDA and AMPA in the lead‐exposed rats decreased significantly than those in the controls. The results indicate that AMPA receptors enriched in area CA1, area CA3, area dentate gyrus and kainate receptors enriched in area CA1, area dentate gyrus are impaired by lead exposure.     

低水平铅暴露对仔鼠白细胞78kd糖调蛋白表达的影响

目的 通过建立低水平铅暴露模型,研究宫内和哺乳期低水平铅暴露对仔鼠白细胞葡萄糖调节蛋白78(glucose regulated protein 78,GRP78)蛋白表达量的影响,从内质网应激的角度探讨铅的发育免疫毒性.方法 将母鼠孕0天至仔鼠出生21天分成不同时期对仔鼠进行低水平铅暴露,用原子吸收分光光度法测定血铅含量,用Western印迹法检测白细胞内质网GRP78蛋白表达量.结果 3个染铅组血铅含量均明显高于对照组,哺乳组的白细胞中GRP78蛋白表达量明显高于对照组,有显著性差异.结论 哺乳期低水平铅暴露可使仔鼠白细胞内质网上的GRP78蛋白应激性表达增加而表现出发育免疫毒性,内质网上的GRP78是铅的重要蓄积库.     

An Update on Exposure and Effects of Lead

Lead is perhaps the oldest of industrial toxins, dating hackto Roman times. Despite the historic knowledge of lead, thismetal remains a public health concern today. This is due bothto the pervasiveness of lead in the environment and to the awarenessof toxic effects of lead occurring at exposure levels lowerthan previously thought harmful. At the 1991 Annual Meeting in Dallas, Texas, the Society ofToxicology hosted the symposium: "An Update on Exposure andEffects of Lead." The goal of the symposium was to present anoverview on critical issues associated with lead toxicity—rangingfrom fundamental mechanisms, such as the role of lead bindingproteins, to assessment of the potential effectiveness of leadabatement measures, such as the impact on blood lead of homedeleading. These issues are summarized in Fig. 1 using the four-stageparadigm of risk assessment as described by the National Academyof Science (NRC, 1977). Clearly, understanding potential impactsof lead in humans is interdisciplinary, involving the effortsof toxicologists, pathologists, epidemiolo gists, environmentalchemists, and others. The following is a summary of each of the individual presentations.     

Effect of Perinatal Lead Exposure on Rat Behaviour in Open-Field and Two-Wky Avoidance Tasks

Abstract: In view of conflicting results in literature concerning lead exposure associated with behavioural alterations, this study investigated behaviour in the open-field and shuttle avoidance, for as well as tissue lead burdens of pre- and post-natally lead-exposed rats. Rats were exposed to the metal from conception to weaning by giving the dams 0.5, 2.0 or 4.0 mM lead acetate in drinking water. This regimen did not affect body weight gain of dams or offspring development and had no effect on cerebral weights nor on haematological parameters of 23-day-old rats. In 1-day-old rats, lead accumulated in the blood but not in the brain, whereas both in 23-day-old rats and in dams lead accumulated in blood, kidney and cerebral cortex. In the open-field, lead-exposed groups showed higher locomotor activity in the test session as compared to controls and did not show any decrease in rearing responses in the test, indicating less habituation. Lead-treated rats subjected to a shuttle avoidance task showed no significant increase in avoidance responses between sessions as compared to control, indicating less retention. Moreover, only the control group presented a significant reduction of the footshock escape latency along testing session, suggesting a lead effect on footshock escape acquisition. In the shuttle box, intertrial crossing responses were not affected by lead treatment. The behavioural alterations occurred in animals with blood lead levels in the range 11-50.6 μg/dl.     

Effects of Lead Exposure on Skeletal Development in Rats

The effects of lead on growth in female rats and on growth andskeletal development in their offspring were investigated. Noalteration in growth rate, compared to the growth rate in pair-fedcontrols, was observed in 48 weanling females continuously exposedto 250 or 1000 ppm lead in drinking water and fed a repletediet. After 49 days of exposure, all rats (24 pair-fed controls,12 exposed to 250 ppm lead, and 12 exposed to 1000 ppm lead)were mated with control males. At parturition, six lactatingdams each from the 250 and 1000 ppm lead groups were removedfrom lead exposure and given control drinking water, and sixlactating dams each from the control group were given either250 or 1000 ppm lead in drinking water. Exposure conditionsfor the remaining dams in the control, 250, and 1000 ppm groupswere not changed. Maternal blood lead in the continuously lead-exposedgroups was higher at the end of lactation than prior to mating.Lead exposure prior to parturition caused greater maternal tibiallead accumulation than lead exposure after parturition. In contrast,lead exposure prior to parturition had a lesser impact on offspringtibial lead accumulation than lead exposure after parturition.Decreases in tibial calcium and phosphorus were observed indams exposed continuously to 250 or 1000 ppm lead; however,there was no apparent effect of lead on maternal growth-platemorphology or on growth-plate width. Offspring body weight wasdepressed relative to controls during suckling (Day 11) andafter weaning (Day 24) in high-dose and continuously lead-exposedgroups. Continuous lead exposure caused a greater decrease inoffspring body weight than lead exposure only prior to or afterparturition. Decreased tail length growth suggested possibleeffects of lead on tail vertebral bone growth. While tibialcalcium and phosphorus levels were not changed in the weanlings,increased weanling growth-plate width, with disruption of chondrocyteorganization, and wider metaphyseal trabeculae were observed.Although the mechanisms of these effects are not known, theresults suggest that local lead-related effects on growth-platechondrogenesis and metaphyseal mineralization may be involved.