慢性铅暴露对幼鼠海马CA1区长时程增强的影响

OBJECTIVE: To study the effects of chronic exposure to lead on learning and memory function in young rats, based on the plasticity of their synapse function. METHODS: With method of extracellular glass microelectrode recording, effects of exposure to lead at different concentrations on long term potentiation (LTP) induction in hippocampal CA(1) area of young rats in vivo were observed. RESULTS: Incidence of LTP and mean amplitude increase after application of high frequency stimulus decreased, as blood lead in rats reached (3.28 +/- 0.88) micromol/L, even causing long term depression. To the exposed rats, their mean increase ratio in their population spike amplitudes after high-frequency stimulation correlated inversely with their brain lead load. CONCLUSION: Chronic lead exposure could damage in vivo LTP induction and maintenance in the CA(1) area in hippocampus of rats, and the severity of damage increased with the extent of exposure to lead.     

慢性铅暴露对大鼠海马CA1区长时程增强的影响

本研究采用神经生理细胞外玻璃微电极记录方法，观察了慢性铅暴露对年幼大鼠海马ＣＡ１区ＬＴＰ的影响。结果表明，铅暴露组与对照组比，ＰＴＰ的平均群体峰电位振幅增强率无明显差别，ＬＴＰ发生率及平均ＰＳ电位幅值增强显著降低，ＰＳ电位增强与脑铅浓度呈显著负相关，提示慢性铅暴露可损害年幼在鼠海马ＣＡ１区的ＬＴＰ的诱导和维持。     

铅对海马区长时程增强影响机制的研究新进展

长时程增强 (long term potentiation ,LTP)现象是指当给予兴奋性传导通路以短暂的连续高频刺激时 ,就能记录到兴奋性突触后电位 (EPSP)斜率的持久性上升 ,即引起突触传递效率的持续增加。目前普遍认为 ,海马区LTP现象是突触可塑性的一种模式 ,是学习和记忆过程中细胞水平的可能机制。铅是环境中广泛存在的重金属元素。目前 ,低水平铅中毒对儿童智力发育的影响受到各方面的广泛关注。我国城市儿童中约半数以上处于无症状的亚临床铅中毒状态[1] 。动物研究结果表明[2 ,3 ] ,铅中毒可增加诱导LTP的阈值 ,使诱导产生的LTP幅度下降和持续…     

环境铅暴露对大鼠海马CA1区长时程增强的影响

用神经生理细胞外玻璃微电极记录方法，观察环境铅暴露对年幼大鼠海马ＣＡ１区ＬＴＰ的影响。结果：铅暴露组与对照组比较，ＰＴＰ的平均群体峰电位振幅增强率无差别；ＬＴＰ发生率与平均ＰＳ电位振幅增强率显著降低。ＰＳ电位增强率与脑铅浓度呈显著负相关。提示环境铅暴露可损害年幼大鼠海马ＣＡ１区的ＬＴＰ的诱导和维持     

脑发育不同阶段铅暴露对大鼠学习记忆能力及海马CA1区长时程增强的影响

随着城市化和工业化的发展 ,环境中低浓度铅污染对儿童智力发育的影响日益受到人们的关注。目前已经证实铅能危害神经系统 ,主要影响未成熟脑的发育及学习记忆功能。而儿童在生长发育的各个时期均可受到铅的威胁 ,因此为进一步明确学习记忆能力在发育的不同时期对铅损伤的敏感性 ,我们利用断乳前后不同发育阶段铅暴露的大鼠为实验对象 ,检测了成年鼠在脑发育的不同时期铅暴露后其空间学习记忆能力的改变。又因为长时程增强 (ＬＴＰ)是目前较为公认的学习记忆的基础[1] ,那么低水平铅暴露对不同发育阶段铅暴露大鼠ＬＴＰ的损害如何 ,国内鲜见…     

铅对大鼠海马生长抑素的影响

探讨铅对大鼠海马生长抑素含量的影响以及停止接触后生长抑素的恢复情况。随着铅染毒剂量增加，血铅及皮层铅浓度均增加，海马中生长抑素含量减少；停止接触３０、９０天后，生长抑素可恢复至正常水平。     

铅暴露对神经元可塑性的影响及其机制

铅是环境中广泛存在的强神经毒物。目前已经证实它能影响神经系统 ,尤其是对婴幼儿的智力发育及学习记忆功能具有危害。我们主要综述了铅暴露对海马长时程增强(ｌｏｎｇ ｔｅｒｍｐｏｔｅｎｔｉａｔｉｏｎ ,ＬＴＰ)等突触可塑性与学习记忆的影响的研究现状及进展 ,以便深入探讨铅影响学习记忆的细胞机制。1973年 ,Ｂｌｉｓｓ和Ｌｏｍｏ首先在麻醉兔上发现了ＬＴＰ现象 ,即短串高频刺激传入引发的突触兴奋性的持续升高 ,表现为给予一定短串高频条件刺激后 ,单个测试刺激引起的群体锋电位 (ｐｏｐｕｌａｔｉｏｎｓｐｉｋｅ ,ＰＳＰ)和群体兴奋…     

出生后铅暴露对大鼠海马突触结构可塑性的影响

目的通过观察断乳后染毒Wistar大鼠海马神经元数目、突触数目以及突触结构参数:突触间隙宽度、突触后致密物厚度、突触活性带长度、突触界面曲率的变化情况,探讨出生后铅暴露对海马突触结构可塑性的影响。方法断乳后雌性大鼠16只,随机分成染铅组和对照组各8只。染铅组经水给予400μmol/L PbCl2,对照组饮用去离子水,直至观察终点(2月龄),T迷宫学习训练后灌注取脑,应用免疫组化法检测神经元数目,利用透射电镜测定突触数目及突触结构参数。结果与对照组相比,染铅组血铅显著增高(P<0.05);染铅组大鼠脑海马CA3区神经元数目与对照组神经元细胞数目无显著差异(P>0.05);染铅组与对照组相比,大鼠脑海马CA1区突触数目显著减少(P<0.05),突触结构参数中:间隙宽度显著增大(P<0.05),突触后致密物厚度、突触界面曲率及突触活性带长度显著减小(P<0.05)。结论断乳后低剂量的铅染毒并不对大鼠海马神经元的数目产生影响,而是主要引起突触连接数目的减少以及突触间隙、突触后致密物厚度等突触结构参数的改变,从而对学习记忆造成影响。     

宫内铅暴露降低海马NMDAR—2A mRNA表达及影响成年后大鼠海马长时程增强

本研究观察了宫内低水平铅暴露对成年后大鼠海马穿通纤维-齿状回颗粒细胞层LTP(长时程增强)及21日龄大鼠海马NMDAR-2A(N-甲基-D-天门冬氨酸受体2A亚型)mRNA表达的影响,从分子水平探讨铅神经毒性的远期危害作用。雌性大鼠从交配前10天开始直到断乳(产后21天)饮用含0.5g/L或2g/L的醋酸铅水,在仔鼠70～90日龄时,利用在位电生理技术测定大鼠海马齿状回由强直刺激诱导的群峰电位。结果表明,虽然铅暴露大鼠的血铅水平已降至100μg/L以下,但海马齿状回LTP的幅度在60min时低铅组分别为(139±41)%和(136±31)%,在高铅组为(151±32)%和(145±30)%而对照组均显著较高,分别为(311±112)%和(319±114)%。提示发育早期铅暴露对学习记忆的损害可能持续到成年期。以原位杂交法检测21日龄仔鼠海马DG(齿状回)、CA1及CA2区NMDAR-2AmRNA表达情况。对DG区颗粒细胞层,CA1及CA2区锥体细胞层分析表明,中毒组动物NMDAR-2AmRNA的表达明显低于对照组,下降幅度分别为34%、37%和44%。因为NMDA受体通道开放是LTP触发之基础,所以宫内低铅暴露对NMDA受体mRNA表达的影响很可能是铅对LTP远期危害的关键分子机制。     

ATP在海马CA1区长时程增强中的作用及机制

目的探讨三磷酸腺苷(adenosine5'-triphosphate,ATP)在海马CA1区长时程增强(LTP)中的作用及机制。方法本研究采用海马在体电生理记录和免疫组织化学方法。在体电生理记录海马CA1区兴奋性突触后电位(field excitatory postsynaptic potentials,fEPSPs)以及高频刺激诱导的LTP,免疫组织化学观察海马CA1区小胶质细胞的激活情况。结果①侧脑室内给予ATP不影响基础性fEPSPs,但能显著抑制高频刺激诱导的LTP,高频刺激后fEPSPs平均幅度较生理盐水对照组明显降低。②侧脑室内给予P2X7受体拮抗剂oxidized ATP,可阻止ATP对海马CA1区LTP的抑制。③给予ATP后30 min,海马CA1区的小胶质细胞明显被激活;侧脑室内给予小胶质细胞抑制剂美满霉素或TNF-α中和抗体,均可阻止ATP对海马CA1区LTP的抑制。结论 ATP可能与P2X7受体结合,激活小胶质细胞抑制海马CA1区LTP,TNF-α参与此作用。     

全氟辛烷磺酸亚慢性暴露对小鼠学习记忆及海马神经元的影响

目的 探讨全氟辛烷磺酸(perfluorooctane sulphonate,PFOs)暴露对小鼠的学习记忆能力及海马神经元的影响.方法 将32只健康清洁级8周龄雄性ICR小鼠按体重随机分为4组,分别为对照(含2％吐温-80的生理盐水)组和5、20、40 mg/kg PFOS暴露组,每组8只.采用腹腔注射方式进行染毒,染毒容量为10 ml/kg,每周3次,连续染毒6周.采用Morris水迷宫实验检测小鼠空间学习、记忆能力,并进行海马神经元形态学的定量分析.结果 训练第1天20 mg/kgPFOS暴露组小鼠的逃避潜伏期长于对照组(P＜0.05),而40 mg/kg PFOS暴露组小鼠训练第1、2天和第5天的逃避潜伏期均较对照组延长(P＜0.05,P＜0.01).与对照组相比,5、20 mg/kg PFOS暴露组小鼠海马CA1和CA3区神经元密度、细胞面积和核黑度差异无统计学意义(P＞0.05);而40 mg/kg PFOS暴露组小鼠海马CA1区神经元密度下降,胞面积减小,核黑度值增大,且CA3区神经元密度也下降,差异均有统计学意义(P＜0.01).结论 一定剂量的PFOS暴露可使小鼠学习记忆能力减弱,可能与海马区神经元损伤有关.     

宫内铅暴露降低海马NMDAR-2AmRNA表达及影响成年后大鼠海马长时程增强

本研究观察了宫内低水平铅暴露对成年后大鼠海马穿通纤维 -齿状回颗粒细胞层 L TP(长时程增强 )及 2 1日龄大鼠海马 NMDAR- 2 A(N-甲基 - D-天门冬氨酸受体 2 A亚型 ) m RNA表达的影响 ,从分子水平探讨铅神经毒性的远期危害作用。雌性大鼠从交配前 10天开始直到断乳 (产后 2 1天 )饮用含 0 .5g/ L 或 2 g/ L 的醋酸铅水 ,在仔鼠 70～ 90日龄时 ,利用在位电生理技术测定大鼠海马齿状回由强直刺激诱导的群峰电位。结果表明 ,虽然铅暴露大鼠的血铅水平已降至 10 0 μg/ L 以下 ,但海马齿状回 L TP的幅度在6 0 min时低铅组分别为 (139± 41) %和 (136± 31) % ,在高铅组为 (15 1± 32 ) %和 (145± 30 ) %而对照组均显著较高 ,分别为 (311± 112 ) %和 (319± 114) %。提示发育早期铅暴露对学习记忆的损害可能持续到成年期。以原位杂交法检测 2 1日龄仔鼠海马 DG(齿状回 )、CA1及 CA2区 NMDAR- 2 A m RNA表达情况。对 DG区颗粒细胞层 ,CA1及 CA2区锥体细胞层分析表明 ,中毒组动物 NMDAR- 2 A m RNA的表达明显低于对照组 ,下降幅度分别为 34%、37%和 44 %。因为 NMDA受体通道开放是 L TP触发之基础 ,所以宫内低铅暴露对 NMDA受体 m RNA表达的影响很可能是铅对 L TP远期危害的关键分子机制。     

Repeated third trimester-equivalent ethanol exposure inhibits long-term potentiation in the hippocampal CA1 region of neonatal rats

Developmental ethanol exposure damages the hippocampus, causing long-lasting learning and memory deficits. Synaptic plasticity mechanisms (e.g., long-term potentiation [LTP]) contribute to synapse formation and refinement during development. We recently showed that acute ethanol exposure inhibits glutamatergic synaptic transmission and N-methyl-d-aspartate receptor (NMDAR)-dependent LTP in the CA1 hippocampal region of postnatal day (P)7-9 rats. The objective of this study was to further characterize the effect of ethanol on LTP in the developing CA1 hippocampus during the third trimester equivalent. To more closely model human ethanol exposure during this period, rat pups were exposed to ethanol vapor (2 or 4.5 g/dL in air, serum ethanol concentrations = 96.6-147.2 or 322-395.6 mg/dL) from P2-9 (4 h/d). Brain slices were prepared immediately after the end of the 4-h exposure on P7-9 and extracellular electrophysiological recordings were performed 1-7 h later under ethanol-free conditions to model early withdrawal. LTP was not different than group-matched controls in the 96.6-147.2 mg/dL group; however, it was impaired in the 322-395.6 mg/dL group. Neither α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor (AMPAR)/NMDAR function nor glutamate release were affected in the 322-395.6 mg/dL ethanol exposure group. These data suggest that repeated in vivo exposure to elevated ethanol doses during the third trimester-equivalent period impairs synaptic plasticity, which may alter maturation of hippocampal circuits and ultimately contribute to the long-lasting cognitive deficits associated with fetal alcohol spectrum disorders.     

妊娠压力与铅联合暴露对大鼠子代空间学习记忆的影响

目的 探讨妊娠压力与铅联合暴露对大鼠子代早期空间学习记忆能力的影响.方法 运用数字表法随机将32只Sprague-Dawley孕鼠分为空白对照组(NS/C),铅暴露组(NS/L),压力暴露组(S/C),联合暴露组(S/L),每组8只.NS/L、S/L自由饮用0.2%醋酸铅溶液,S/C、S/L给予束缚压力.子代于30 d龄进行Morris水迷宫测试,并检测海马组织铅含量及水迷宫实验前、后血清肾上腺酮.结果 S/L雄、雌性仔鼠在原平台所在象限停留时间分别为(16.08 ±3.41)s、(15.72 ±3.33)s,显著短于NS/L(25.42±4.76)s、(24.55±4.43)s和S/C(20.96±3.45)s、(20.65±2.98)s,妊娠压力与铅对仔鼠在原平台所在象限停留时间的影响存在交互作用(F=5.478,P<0.05);妊娠压力与铅对仔鼠应激后血清肾上腺酮水平的影响存在交互作用.NS/L、S/L仔鼠海马铅含量分别为(0.4378 ±0.1041)μg/g、(0.4679 ±0.1243)μg/g,差异无统计学意义(F=0.298,P0.05).结论 (1)妊娠压力与铅对大鼠子代学习记忆的损害可能具有叠加作用.(2)妊娠压力与铅对仔鼠下丘脑.垂体-肾上腺轴的影响可能具有叠加作用.该作用可能是二者对子代学习记忆叠加损害的原因之一.(3)联合暴露未显著增加铅在子代海马中的蓄积.     

Effects of fasting on distribution and excretion of lead following long-term lead exposure in rats

Lead was given to rats through drinking water containing 100 ppm lead acetate for 20 days. Delta-aminolevulinic acid dehydratase (ALAD) activity in erythrocytes was significantly lower (p < 0.05) at 20 days after Pb treatment. Erythrocytic ALAD activity was significantly lower (p < 0.05) in fasted rats than in fed rats with or without Pb pretreatment. Serum glutamic pyruvic transaminase and glutamic oxaloacetic transaminase activities after 6 days of fasting were significantly higher (p < 0.05) in Pb pretreated rats than in other groups (Ph nontreated fed and fasted rats, and Pb pretreated fed rats). Long periods of fasting strongly enhanced these serum-enzymes elevations induced by lead. Maximum Pb concentrations and total amount in feces increased in rats fasted for 3 days regardless of Pb pretreatment. On the other hand, total amount of Pb in feces of rats fasted for 6 days were not significantly different from the other groups because their fecal volume decreased to about 1 % of fed rats. The Pb concentrations of liver, kidney, spleen, and femur increased significantly in Pb pretreated rats compared to in controls, but there were no significant differences between the fed and fasted rats.     

铅暴露对雄性仔鼠海马锌离子转运体3表达的影响

目的探讨铅暴露对雄性仔鼠海马锌离子转运体3(zinc transporter 3,ZNT3)表达的影响。方法将12只健康SPF级雌性SD大鼠随机分为3组,分别为对照(去离子水)组和低(0.5 g/L乙酸铅)、高(2.0 g/L乙酸铅)剂量铅染毒组,每组4只。采取自由饮水方式进行染毒,自妊娠前10 d至仔鼠断乳(出生后21 d)。采用等离子体发射光谱(ICP-AES)法检测雄性仔鼠全血及海马组织中铅、锌的含量;采用RT-PCR法检测其海马组织中ZNT3 m RNA的表达水平;采用Western blot法检测其海马组织中ZNT3蛋白的表达。结果与对照组比较,各剂量铅染毒组雄性仔鼠全血与海马组织中的铅含量均较高,锌含量均较低,差异有统计学意义(P0.05);且随着铅染毒剂量的升高,雄性仔鼠全血和海马组织中铅的含量呈上升趋势,锌含量呈下降趋势。与对照组比较,各剂量铅染毒组雄性仔鼠海马组织中ZNT3 m RNA及蛋白的表达水平均较高,差异有统计学意义(P0.05);但高、低剂量铅染毒组雄性仔鼠海马组织中ZNT3 m RNA及蛋白的表达水平间比较,差异无统计学意义(P0.05)。结论铅暴露上调了大鼠海马组织中ZNT3的表达水平,这可能与铅暴露使海马锌含量的降低有关。     

In vivo and in vitro exposure to PCB 153 reduces long-term potentiation

We examined the effects of gestational and lactational exposure to polychlorinated biphenyl (PCB) 153 (2,4,5,2',4',5'-hexaCB) on the magnitude of long-term potentiation (LTP) observed in the CA1 region of hippocampal brain slices prepared from rats at 30 days of age. We compared these actions to those observed when PCB 153 is dissolved in normal Krebs-Ringer solution and perfused on slices from control rats of the same age. In vivo exposure was at three dose levels (1. 25, 5, and 20 mg/kg/day) from gestational day 3 through weaning at postnatal day 21. Although responses to low-frequency stimulation of the Schaffer collateral pathway in exposed animals were not different from controls, significantly reduced LTP was induced after tetanic stimulation, even at the lowest dose studied. We observed a comparable depression of LTP when control slices were perfused with Krebs-Ringer that had been equilibrated with PCB 153 in a generator column. Neither in vivo nor in vitro exposure significantly altered the input-output curves obtained before tetanic stimulation, but both suppressed the increase in response observed in controls after tetanic stimulation. Because LTP is thought to be correlated with learning ability, these observations may provide at least a partial mechanism to explain the reduction of intelligence quotient observed in humans exposed to PCBs early in development.     

Effects of intermittent binge alcohol exposure on long-term motor function in young rats

Ethanol has well described acute effects on motor function, and chronic alcoholism can damage the cerebellum, which is associated with motor coordination, as well as motor learning. Binge drinking is common among preadolescents and adolescents, and this type of ethanol exposure may lead to long-term nervous system damage. In the current study, we analyzed the effects of periadolsecent/adolescent ethanol exposure on motor function in both male and female Sprague–Dawley rats. To simulate binge drinking, animals received an intraperitoneal injection of 25% (v/v) ethanol (3 g/kg) on postnatal days (PND) 25, 26, 29, 30, 33, 34, 37 and 38. On PND 42 and PND 61 animals were tested on their ability to traverse both square and round beams. There were no significant differences in the time to traverse the beams, or the amount of foot slips, between treated and untreated animals. On PND 48 and PND 62, animals were tested using a horizontal ladder walking apparatus. On PND 48 there were no differences in the ability of treated and untreated animals to traverse the ladder. On PND 62, there were no differences in the time to traverse the ladder, but ethanol treated animals had more foot slips than controls. On PND 43, we conducted footprint analysis of control and treated animals, which included measurements of stride length, paw overlap, and angle of foot placement. There was a significant difference in the angle of foot placement between treated and control animals, and this finding was significant for both male and female animals. There was also a significant overall difference in paw overlap between treatment groups. Although this effect was manifested in male animals there was no significant difference in females. These findings suggest that adolescent ethanol exposure can produce long-lasting effects on motor coordination, and that overall, effects are similar in males and females. In a second set of experiments, male rats received i.p. ethanol (3 g/kg) for 7 days (P31–37) or 4 days (P31,33,35,37). No significant differences were detected by footprint analysis when compared to control animals. However, ethanol treated animals had significantly less cerebellar Purkinje cells at 3 weeks after the last ethanol exposure. Altered motor function suggests a possible neurodegenerative effect in the cerebellum initiated by adolescent ethanol exposure, and may depend on the extent of exposure during the preadolescent and/or adolescent brain periods.