地塞米松致子代大鼠海马轴突发育损伤

为了探讨地塞米松对子代大鼠海马轴突的影响,建立了孕期地塞米松暴露（prenatal dexamethasone exposure, PDE）模型。Wistar大鼠于孕中晚期皮下注射地塞米松（0.2 mg·kg^-1·d^-1）,部分子代于孕20天（GD20）、出生后12周（PW12）处死取海马样本,检测海马糖皮质激素受体（glucocorticoid receptor, GR）活化指标以及轴突损伤指标。PDE子代胎鼠海马GR活化,GR、糖皮质激素调节激酶1（glucocorticoid-regulated kinase 1, SGK1）和FK506结合蛋白（FK506 binding protein 5, FKBP5）表达显著增加。轴突损伤指标包括生长相关蛋白43（growth associated protein-43,GAP43）、信号素3A（semaphorin 3A, SEMA3A）和集聚蛋白（agrin）表达明显升高。而PDE成年子代大鼠海马GR无明显活化,轴突损伤指标GAP43、SEMA3A和AGRIN表达明显升高。研究结果证实PDE通过活化胎海马GR引起轴突发育损伤,且轴突损伤可延续至出生后。     

核磁共振磁场照射对子代大鼠海马突触形态的影响

研究观察了孕期磁共振磁场照射对子代大鼠海马突触超微结构的影响。SD孕鼠妊娠第12-18d给予0．35T核磁共振(magnetic resonance imaging,MRI)磁场照射。测量1、2和5月龄雌性仔鼠海马CAl区和齿状回的突触结构参数,用立体计量学方法进行定量测定。结果显示,磁场照射可引起2月龄子代大鼠海马CAl区突触间隙增宽．齿状回突触活性区长度变短、突触界面曲率和活性区面密度减小;5月龄子代大鼠CAl区突触间隙增宽,突触后致密物变薄,突触界面曲率减小,齿状回突触间隙增宽。结果提示,妊娠期接受MRI磁场照射可引起海马突触超微结构的改变。对这些结构变化与行为损害之间的关系进行了讨论。     

产前850-1900MHz手机暴露对子代大鼠齿状回PCNA和DCX表达的影响

目的：探讨产前手机暴露对子代大鼠海马齿状回增殖细胞核抗原（PCNA）和双皮质素（DCX）表达的影响。方法：构建孕鼠手机射频暴露模型,分为对照组、短时暴露组和长时暴露组（n=6）,短时和长时暴露组于孕第1-17天分别给予6 h/d和24 h/d的手机通话暴露,观察孕鼠的孕期长短、孕期体重增长和各组的胎儿数、胎儿出生体重。1月龄子代大鼠行焦油紫染色观察海马齿状回细胞形态,免疫组化观察齿状回PCNA和DCX表达,Western blot检测DCX和脑源性神经营养因子（BDNF）表达。结果：各组孕鼠的孕期、妊娠期体重增长和各组的胎儿数、胎儿出生体重无显著差异,长时暴露组子代大鼠的齿状回多形细胞层锥形细胞和DCX阳性细胞出现形态改变。与对照组、短时暴露组比较,长时暴露组子代大鼠齿状回PCNA阳性细胞和DCX、BDNF表达均明显减少（P<0.05）。结论：产前长时手机暴露可能通过改变子代大鼠海马BDNF而影响齿状回的PCNA和DCX表达。     

孕期大鼠暴露PFOS对胎鼠肝脏毒性的影响

目的:研究在孕期暴露PFOS对胎鼠的肝脏毒性的影响.方法:将孕期为12天的16只SD雌性大鼠,随机分为4组给予不同剂量的PFOS[0(对照),5,10,20 mg·kg-1],连续灌胃7天,在GD19天时对母鼠和胎鼠的体重、胎鼠肝脏的生化指标、母鼠血清的生化指标进行了相应的检测.结果:与对照组相比,母鼠体重在20 mg·kg-1组显著下降(P＜0.001);胎鼠的体重和体长在20mg·kg-1组显著下降(P＜0.001);胎鼠的肝脏重量降低,呈剂量依赖性,并伴有肝细胞浊肿、变性甚至坏死;10 mg· kg-1组胎鼠肝脏中的酶活性(ALT、AST、GGT和ALP等)显著升高(P＜0.001);母鼠血清的大部分生化指标未发生明显变化.结论:孕期大鼠暴露在PFOS的环境下会严重损伤胎鼠的肝脏功能.     

围产期食物限制对子代成年大鼠海马CA1区突触可塑性的影响

围产期食物限制导致子代大鼠学习和记忆能力等的神经生物学变化,但其机制并不清楚。将成年Wistar雌性大鼠与雄性大鼠同笼,受孕后随机分为对照组 (n=9) 和食物限制组 (n=8) 。对照组母鼠在妊娠期和哺乳期自由进食和饮水,食物限制组母鼠从妊娠的第7天到子代大鼠出生后21天进行食物限制,食物限制量为对照组大鼠的50%。子代雄性大鼠成年后,通过Morris 水迷宫测试空间学习和记忆能力。之后,在海马CA1区在体记录场兴奋性突触后电位 (field excitatory postsynaptic potential,fEPSP),并采用免疫组织化学方法观察海马CA1区神经元型一氧化氮合酶 (nNOS) 阳性细胞密度的变化。结果表明,围产期食物限制降低了子代大鼠出生后第1、7、10、14和21天的体重,并减弱了成年子代大鼠的学习和记忆能力,海马CA1区fEPSP的斜率和nNOS阳性细胞的密度也明显降低。结果提示,围产期食物限制可能通过抑制NO的产生降低了海马突触可塑性,从而影响了子代大鼠的学习和记忆能力。     

HIV-1 gp120对鼠海马长时程增强效应的影响

为了探讨人类免疫缺陷病毒Ⅰ型(HIV-1)的包膜糖蛋白gp120对鼠海马脑片CA1区的突触传递及可塑性的影响,应用离体脑片记录技术,记录大鼠海马CA1区的兴奋性突触后电位(excitatory postsynaptic potential,EPSP),研究了gp120对高频电刺激Schaffer侧支引起的鼠长时程增强效应(long-term potentiation,LTP)的影响.结果发现:gp120对大鼠海马CA1区LTP产生抑制作用,对其基础EPSP没有影响,而且这种抑制效应随着gp120浓度增大而增强,即具有剂量依赖性.PKA/PKC蛋白激酶抑制剂H7可以反转这种抑制效应.提示:gp120可能是通过抑制海马CA1区的LTP而参与艾滋病相关性痴呆(HIV-1 associated dementia,HAD)的形成.     

应激诱发的海马神经元突触增强参与大鼠的新环境学习

本文旨在研究应激对海马新环境空间学习记忆的损伤作用机制.在大鼠海马CA1区埋植电极,刺激schaffer侧枝记录CA1区树突层的兴奋性突触后场电位(field excitatory postsynaptic potential,fEPSP),探索应激对火鼠新环境空间学习的突触可塑性的影响.同时研究了再次新环境空间学习时...     

在体大鼠海马Schaffer-CA1条件化双通路与海马组合突触可塑性

在戊巴比妥钠麻醉的Sprague-Dawley大鼠上,运用海马Schaffer-CA1双通路条件化作用(低频配对,600对脉冲,5Hz,配对刺激相应的兴奋性突触后电位峰值时间间隔为10ms)在两条Schaffer-CA1条件化通路上同时诱导出突触可塑性,呈现出海马组合突触可塑性。结果显示:不管海马Schaffer-CA1双通路独立与否,双通路条件化作用均可以同时诱导出长时程增强(long-term potentiation,LTP)和长时程抑制(long-term depression,LTD),呈现出LTP/LTD组合突触可塑性。结果表明:海马Schaffer-CA1双通路技术,可实现海马突触可塑性的双向诱导,可塑性的方向取决于突触的自身状态。由此提示,与传统的高频诱导LTP低频诱导LTD相比,在海马Schaffer-CA1双通路条件化作用诱导出的组合突触可塑性可以更好地编码海马相关的学习记忆,体现了海马突触可塑性的灵活性与稳定性。     

皮质酮对大鼠海马脑片CA1区长时程增强效应的影响

目的：探讨糖皮质激素对海马神经突触可塑性的影响。方法：高浓度（10^-5mol/L)皮质酮直接作用于大鼠海马脑片,记录CA1区LTP）。结果：海马脑片CA1区LTP的形成受到抑制。结论：应激时过量糖皮质激素会直接影响海马神经突触可塑性。     

D-半乳糖合并Meynert基底核损毁对海马长时程增强和突触形态的影响

目的 :研究D 半乳糖合并Meynert基底核损毁Alzheimer病 (AD)大鼠模型海马突触可塑性的变化。方法 :通过0 .96 %D 半乳糖致亚急性损伤及鹅膏蕈氨酸损毁Meynert基底核建立AD动物模型 ,应用行为学测试、电生理学方法和电镜观察 ,研究AD模型大鼠海马突触形态结构和长时程增强现象 (long termpotentiation ,LTP)的变化。结果 :①AD模型大鼠在Morris水迷宫的学习记忆能力明显低于对照组 ;②AD大鼠海马CA1区突触的数密度、面密度明显减少 ;③AD模型大鼠海马齿状回产生的LTP较对照组明显降低。结论 :海马突触结构改变和功能可塑性的降低可能与AD大鼠的学习记忆能力下降有关     

Prenatal corticosteroid exposure affects hippocampal plasticity and reduces lifespan

Synthetic corticosteroids, such as dexamethasone, are frequently administered to pregnant women at risk for preterm delivery. Endogenous corticosteroids are essential for normal development, but exposure to therapeutic doses at critical developmental stages may have adverse effects on the central nervous system. Major concern has arisen about long-term effects of corticosteroid treatment on brain plasticity, particularly in the hippocampus. Therefore, we analyzed the molecular, cellular, and behavioral effects of prenatal dexamethasone treatment on the adult hippocampus. Pregnant mice were treated at embryonic day 15.5 with a single dose of dexamethasone or saline. Adult offspring was analyzed for hippocampal neuron loss, cell proliferation, and NMDA receptor subunit expression. Hippocampal function was assessed in the Morris water maze and synaptic plasticity in the CA1 field by determining frequency dependence of LTP and LTD in hippocampal slices. Prenatal dexamethasone treatment decreased hippocampal cell proliferation in the dentate gyrus. Treated mice showed reduced LTD, impaired spatial learning, and a marked reduction in lifespan. Our data show long-term adverse effects of prenatal dexamethasone treatment on hippocampal function in mice and suggest accelerated aging. These findings indicate that it is important to be restrictive with corticosteroid administration during fetal development because of the lifelong consequences.     

Maternal dietary loads of α-tocopherol depress protein kinase C signaling and synaptic plasticity in rat postnatal developing hippocampus and promote permanent deficits in adult offspring

Vitamin E (α-tocopherol) supplementation has been tested as prophylaxis against gestational disorders associated with oxidative damage. However, recent evidence showing that high maternal α-tocopherol intake can adversely affect offspring development raises concerns on the safety of vitamin E extradosages during pregnancy. Besides acting as an antioxidant, α-tocopherol depresses cell proliferation and modulates cell signaling through inhibiting protein kinase C (PKC), a kinase that is deeply involved in neural maturation and plasticity. Possible effects of α-tocopherol loads in the maturing brain, where PKC dysregulation is associated to developmental dysfunctions, are poorly known. Here, supranutritional doses of α-tocopherol were fed to pregnant and lactating dams to evaluate the effects on PKC signaling and morphofunctional maturation in offspring hippocampus. Results showed that maternal supplementation potentiates hippocampal α-tocopherol incorporation in offspring and leads to marked decrease of PKC phosphorylation throughout postnatal maturation, accompanied by reduced phosphorylation of growth-associated protein-43 and myristoylated alanine-rich C kinase substrate, two PKC substrates involved in neural development and plasticity. Although processes of neuronal maturation, synapse formation and targeting appeared unaffected, offspring of supplemented mothers displayed a marked reduction of long-term synaptic plasticity in juvenile hippocampus. Interestingly, this impairment persisted in adulthood, when a deficit in hippocampus-dependent, long-lasting spatial memory was also revealed. In conclusion, maternal supplementation with elevated doses of α-tocopherol can influence cell signaling and synaptic plasticity in developing hippocampus and promotes permanent adverse effects in adult offspring. The present results emphasize the need to evaluate the safety of supranutritional maternal intake of α-tocopherol in humans.     

Cdk5 is required for memory function and hippocampal plasticity via the cAMP signaling pathway

Memory formation is modulated by pre- and post-synaptic signaling events in neurons. The neuronal protein kinase Cyclin-Dependent Kinase 5 (Cdk5) phosphorylates a variety of synaptic substrates and is implicated in memory formation. It has also been shown to play a role in homeostatic regulation of synaptic plasticity in cultured neurons. Surprisingly, we found that Cdk5 loss of function in hippocampal circuits results in severe impairments in memory formation and retrieval. Moreover, Cdk5 loss of function in the hippocampus disrupts cAMP signaling due to an aberrant increase in phosphodiesterase (PDE) proteins. Dysregulation of cAMP is associated with defective CREB phosphorylation and disrupted composition of synaptic proteins in Cdk5-deficient mice. Rolipram, a PDE4 inhibitor that prevents cAMP depletion, restores synaptic plasticity and memory formation in Cdk5-deficient mice. Collectively, our results demonstrate a critical role for Cdk5 in the regulation of cAMP-mediated hippocampal functions essential for synaptic plasticity and memory formation.     

SHH信号通路在海马神经可塑性及相关神经系统疾病中的作用

音猬因子（sonic hedgehog,SHH）是一种分泌蛋白质,可在发育过程中控制神经祖细胞、神经元和神经胶质细胞的形成。研究发现,海马是学习和记忆中至关重要的大脑区域,SHH在海马神经元回路的形成和可塑性中发挥重要作用,可介导海马神经的发生和突触的可塑性调节。海马神经元树突中SHH受体的激活是跨神经元信号通路的组成部分,该信号通路可加速轴突的生长并增强谷氨酸从突触前末端的释放。SHH信号通路转导受损可导致中枢神经系统损伤和相关疾病（如自闭症、抑郁症和神经退行性疾病等）发生。因此,控制SHH信号通路转导,如使用SHH通路抑制剂或激动剂可能有助于相关疾病的治疗。综述了SHH信号通路的海马神经可塑性及其在中枢神经系统发育和相关疾病中的影响,以期为阐明SHH信号转导受损导致的海马神经受损和中枢神经系统相关疾病的机制奠定一定的理论依据。     

Maternal infection and fever during late gestation are associated with altered synaptic transmission in the hippocampus of juvenile offspring rats

Prenatal exposure to infection is known to affect brain development and has been linked to increased risk for schizophrenia. The goal of this study was to investigate whether maternal infection and associated fever near term disrupts synaptic transmission in the hippocampus of the offspring. We used LPS to mimic bacterial infection and trigger the maternal inflammatory response in near-term rats. LPS was administered to rats on embryonic days 15 and 16 and hippocampal synaptic transmission was evaluated in the offspring on postnatal days 20-25. Only offspring from rats that showed a fever in response to LPS were tested. Schaffer collateral-evoked field excitatory postsynaptic potentials (fEPSPs) and fiber volleys in CA1 of hippocampal slices appeared smaller in offspring from the LPS group compared with controls, but, when the fEPSPs were normalized to the amplitude of fiber volleys, they were larger in the LPS group. In addition, intrinsic excitability of CA1 pyramidal neurons was heightened, as antidromic field responses in the LPS group were greater than those from control. Short-, but not long-term plasticity was impaired since paired-pulse facilitation of the fEPSP was attenuated in the LPS group, whereas no differences in long-term potentiation were noted. These results suggest that LPS-induced inflammation during pregnancy produces in the offspring a reduction in presynaptic input to CA1 with compensatory enhancements in postsynaptic glutamatergic response and pyramidal cell excitability. Neurodevelopmental disruption triggered by prenatal infection can have profound effects on hippocampal synaptic transmission, likely contributing to the memory and cognitive deficits observed in schizophrenia.     

Effects of isoflurane exposure during pregnancy on postnatal memory and learning in offspring rats

Emerging evidence has demonstrated that exposure to anesthetics early in life caused neurohistopathologic changes and persistent behavioral impairments. In this study, a maternal fetal rat model was developed to study the effects of isoflurane exposure during pregnancy on postnatal memory and learning in the offspring. Pregnant rats at gestational day 14 were either exposed to 1.3% isoflurane in a humidified 100% oxygen carrier gas or simply humidified 100% oxygen without any inhalational anesthetic for 2 h every day before delivery. Four weeks later, spatial learning and memory of the offspring were examined using the Morris Water Maze. The expression levels of GAP-43 and NPY in the hippocampal CA1 region of the pups were determined by immunohistochemistry and RT-PCR. Simultaneously, the ultrastructure changes in synapse of the hippocampus were also observed by transmission electron microscopy (TEM). Isoflurane exposure during pregnancy impaired postnatal spatial memory and learning in the offspring as shown by the longer escape latency and the fewer original platform crossings in the Morris Water Maze test. The number and optical densities of GAP-43 and NPY positive cells, as well as the levels of GAP-43 and NPY mRNA, decreased significantly in the hippocampus of isoflurane-exposed pups. Furthermore, TEM studies showed remarkable changes in synaptic ultrastructure of hippocampus. These results indicate that isoflurane exposure during pregnancy could cause postnatal spatial memory and learning impairments in offspring rats, which may be partially explained by the down-regulation of GAP-43 and NPY in the hippocampal area.     

Ryanodine receptor 1 mediated dexamethasone-induced chondrodysplasia in fetal rats

BackgroundOsteoarthritis is caused by cartilage dysplasia and has fetal origin. Prenatal dexamethasone exposure (PDE) induced chondrodysplasia in fetal rats by inhibiting transforming growth factor β (TGFβ) signaling. This study aimed to determine the effect of dexamethasone on fetal cartilage development and illustrate the underlying molecular mechanism.MethodsDexamethasone (0.2 mg/kg.d) was injected subcutaneously every morning in pregnant rats from gestational day (GD) 9 to GD21. Harvested fetal femurs and tibias at GD21 for immunofluorescence and gene expression analysis. Fetal chondrocytes were treated with dexamethasone (100, 250 and 500 nM), endoplasmic reticulum stress (ERS) inhibitor, and ryanodine receptor 1 (RYR1) antagonist for subsequent analyses.ResultsIn vivo, prenatal dexamethasone exposure (PDE) decreased the total length of the fetal cartilage, the proportion of the proliferation area and the cell density and matrix content in fetal articular cartilage. Moreover, PDE increased RYR1 expression and intracellular calcium levels and elevated the expression of ERS-related genes, while downregulated the TGFβ signaling pathway and extracellular matrix (ECM) synthesis in fetal chondrocytes. In vitro, we verified dexamethasone significantly decreased ECM synthesis through activating RYR 1 mediated-ERS.ConclusionsPDE inhibited TGFβ signaling pathway and matrix synthesis through RYR1 / intracellular calcium mediated ERS, which ultimately led to fetal dysplasia. This study confirmed the molecular mechanism of ERS involved in the developmental toxicity of dexamethasone and suggested that RYR1 may be an early intervention target for fetal-derived adult osteoarthritis.     

Maternal omega-3 intake differentially affects the endocannabinoid system in the progeny`s neocortex and hippocampus: Impact on synaptic markers

Omega-3 (n-3) polyunsaturated fatty acids (PUFA) and the endocannabinoid system (ECS) modulate several functions through neurodevelopment including synaptic plasticity mechanisms. The interplay between n-3PUFA and the ECS during the early stages of development, however, is not fully understood. This study investigated the effects of maternal n-3PUFA supplementation (n-3Sup) or deficiency (n-3Def) on ECS and synaptic markers in postnatal offspring. Female rats were fed with a control, n-3Def, or n-3Sup diet from 15 days before mating and during pregnancy. The cerebral cortex and hippocampus of mothers and postnatal 1-2 days offspring were analyzed. In the mothers, a n-3 deficiency reduced CB1 receptor (CB1R) protein levels in the cortex and increased CB2 receptor (CB2R) in both cortex and hippocampus. In neonates, a maternal n-3 deficiency reduced the hippocampal CB1R amount while it increased CB2R. Additionally, total GFAP isoform expression was increased in both cortex and hippocampus in neonates of the n-3Def group. Otherwise, maternal n-3 supplementation increased the levels of n-3-derived endocannabinoids, DHEA and EPEA, in the cortex and hippocampus and reduced 2-arachidonoyl-glycerol (2-AG) concentrations in the cortex of the offspring. Furthermore, maternal n-3 supplementation also increased PKA phosphorylation in the cortex and ERK phosphorylation in the hippocampus. Synaptophysin immunocontent in both regions was also increased. In vitro assays showed that the increase of synaptophysin in the n-3Sup group was independent of CB1R activation. The findings show that variations in maternal dietary omega-3 PUFA levels may impact differently on the ECS and molecular markers in the cerebral cortex and hippocampus of the progeny.     

小鼠海马内HDAC2的表达及其与NMDA受体、PSD-95的共定位

目的探讨组蛋白去乙酰化酶2（HDAC2）在成年C57BL/6小鼠海马内的分布及其与突触后致密区（PSD）蛋白成员的共定位,为揭示HDAC2与PSD蛋白复合物之间的内在联系及在海马相关的学习记忆过程中可能起到的调控作用提供形态学依据。方法应用免疫组化方法观察HDAC2在C57BL/6小鼠海马各区的表达分布。应用免疫荧光双标技术研究HDAC2与PSD蛋白成员N-甲基-D-天冬氨酸（NMDA）受体亚单位1（NR1）、PSD-95之间是否存在共定位。结果 HDAC2在小鼠海马CA1～CA3区锥体细胞和齿状回颗粒细胞均具有明显表达,而在各区的始层、辐射层、腔隙-分子层以及齿状回多形细胞层表达均较少。免疫荧光双标染色图片的重叠表明,HDAC2与NR1、PSD-95在小鼠海马CA1～CA3区锥体细胞层和齿状回颗粒细胞层内均可见显著共表达现象,其他区域偶见散在分布的双染神经元。结论 HDAC2在小鼠海马锥体细胞层和颗粒细胞层表达丰富,并与PSD蛋白成员间存在共定位现象。本实验结果为探讨HDAC2对谷氨酸能突触后神经元依赖的突触可塑性的调节机制提供了形态学依据。