血管性痴呆大鼠海马突触结构参数的变化

目的 :观察血管性痴呆大鼠海马突触结构特点 ,探讨血管性痴呆学习记忆障碍的神经病理机制。方法 :采用永久性结扎双侧颈总动脉的方法建立血管性痴呆动物模型 ,利用Morris水迷宫和Y型电迷宫检验大鼠的学习记忆能力 ,应用透射电镜和形态计量学分析血管性痴呆大鼠海马GrayⅠ型突触的突触结构参数的变化。结果 :血管性痴呆大鼠海马CA1区GrayⅠ型突触的体积密度、面积密度、比表面和面数密度均减小 ,突触平均面积增大 ;突触界面曲率、突触间隙宽度、突触后致密物厚度均减小。结论 :永久性结扎双侧颈总动脉使大鼠海马CA1区GrayⅠ型突触数量减少和形态结构发生显著变化 ,导致学习记忆障碍     

Cognition and hippocampal synaptic plasticity in mice with a homozygous tau deletion

Tau has been implicated in the organization, stabilization, and dynamics of microtubules. In Alzheimer's disease and more than 20 neurologic disorders tau missorting, hyperphosphorylation, and aggregation is a hallmark. They are collectively referred to as tauopathies. Although the impact of human tauopathies on cognitive processes has been explored in transgenic mouse models, the functional consequences of tau deletion on cognition are far less investigated. Here, we subjected tau knock-out (KO) mice to a battery of neurocognitive, behavioral, and electrophysiological tests. Although KO and wild-type mice were indistinguishable in motor abilities, exploratory and anxiety behavior, KO mice showed impaired contextual and cued fear conditioning. In contrast, extensive spatial learning in the water maze resulted in better performance of KO mice during acquisition. In electrophysiological experiments, basal synaptic transmission and paired-pulse facilitation in the hippocampal CA1-region were unchanged. Interestingly, deletion of tau resulted in severe deficits in long-term potentiation but not long-term depression. Our results suggest a role of tau in certain cognitive functions and implicate long-term potentiation as the relevant physiological substrate.     

Loss of synaptotagmin IV results in a reduction in synaptic vesicles and a distortion of the Golgi structure in cultured hippocampal neurons

Fusion of synaptic vesicles with the plasma membrane is mediated by the SNARE (soluble NSF attachment receptor) proteins and is regulated by synaptotagmin (syt). There are at least 17 syt isoforms that have the potential to act as modulators of membrane fusion events. Synaptotagmin IV (syt IV) is particularly interesting; it is an immediate early gene that is regulated by seizures and certain classes of drugs, and, in humans, syt IV maps to a region of chromosome 18 associated with schizophrenia and bipolar disease. Syt IV has recently been found to localize to dense core vesicles in hippocampal neurons, where it regulates neurotrophin release. Here we have examined the ultrastructure of cultured hippocampal neurons from wild-type and syt IV −/− mice using electron tomography. Perhaps surprisingly, we observed a potential synaptic vesicle transport defect in syt IV −/− neurons, with the accumulation of large numbers of small clear vesicles (putative axonal transport vesicles) near the trans-Golgi network. We also found an interaction between syt IV and KIF1A, a kinesin known to be involved in vesicle trafficking to the synapse. Finally, we found that syt IV −/− synapses exhibited reduced numbers of synaptic vesicles and a twofold reduction in the proportion of docked vesicles compared to wild-type. The proportion of docked vesicles in syt IV −/− boutons was further reduced, 5-fold, following depolarization.     

Impaired hepatic granuloma formation in mice deficient in C-C chemokine receptor 2

Granulomas are characterized histologically by a nodular collection of macrophages with occasional admixture of epithelioid cells, multinucleate giant cells, and other immunocompetent cells. Chemokines are considered to play an important role in the recruitment of these constituent cells of granulomas. The present study has examined the effect of a deficiency of C-C chemokine receptor-2 (CCR2) on hepatic granuloma formation induced by a single injection of Zymosan A. In CCR2+/+ mice, the number and the size of granulomas gradually increased until they reached peak values at 10 days after the injection. In contrast, both the number and the size of granulomas were smaller in CCR2-/- mice than in CCR2+/+ mice from days 5 to 21. They showed low peaks at day 5, after which the number and the size of the granulomas gradually decreased. Immunohistochemical analysis of the constituent granuloma cells using cell type-specific monoclonal antibodies revealed rapid accumulation of blood monocytes, with subsequent differentiation to macrophages, in CCR2+/+ mice during days 2-10. This process was greatly impaired in CCR2-/- mice and granulomas remained small. At all time points, the percentage of polymorphonuclear cells in granulomas was higher in CCR2-/- mice than in CCR2+/+ mice. Interestingly, multinucleate giant cells were frequently observed in granulomas in CCR2-/- mice, whereas they rarely appeared in CCR2+/+ mice. Profiles of liver cytokine RNA levels as well as serum cytokine levels revealed reduced expression of the Th1 cytokine IFN-gamma in CCR2-/- mice. These data clearly indicate that signalling through CCR2 has many effects on the normal growth and development of hepatic granulomas.     

Genetic differences in hippocampal synaptic plasticity

Synaptic plasticity is considered a physiological substrate for learning and memory [Lynch MA (2004) Long-term potentiation and memory. Physiol Rev 84:87–136] that contributes to maladaptive learning in drug addiction [Schoenbaum G, Roesch MR, Stalnaker TA (2006) Orbitofrontal cortex, decision-making and drug addiction. Trends Neurosci 29:116–124]. Many studies have revealed that drug addiction has a strong hereditary component [Kosten TA, Ambrosio E (2002) HPA axis function and drug addictive behaviors: insights from studies with Lewis and Fischer 344 inbred rats. Psychoneuroendocrinology 27:35–69; Uhl GR (2004) Molecular genetic underpinnings of human substance abuse vulnerability: likely contributions to understanding addiction as a mnemonic process. Neuropharmacology 47 (Suppl 1):140–147], however the contribution of the genetic background to drug-induced changes in synaptic plasticity has been scarcely studied. The present study reports on an analysis of long-term potentiation (LTP) and depotentiation in Lewis (LEW) and Fischer-344 (F344) rats, two inbred rat strains that show different proneness to drugs of abuse and are considered an experimental model of genetic vulnerability to addiction [Kosten TA, Ambrosio E (2002) HPA axis function and drug addictive behaviors: insights from studies with Lewis and Fischer 344 inbred rats. Psychoneuroendocrinology 27:35–69]. The induction of saturated-LTP was similar in LEW and F344 rats treated with saline or cocaine. However, only slices from LEW saline-treated rats showed the reversal of LTP; thus, the depotentiation of saturated-LTP was not observed in cocaine-injected LEW rats and in F344 animals (treated either with cocaine or saline). These results suggest significant differences in hippocampal synaptic plasticity between Lewis and Fischer 344 rats.     

Y-Chromosomal effects on discrimination learning and hippocampal asymmetry in mice

From a four-way cross between unrelated inbred strains of mice, a random-breeding line was developed that segregated at two coat-color loci and carried Y chromosomes from different sources. Adult males were used for measurements of black-white discrimination learning and 7-day response retention in a water maze, body weight, brain weight, and left- and right-side hippocampus weight. Clear evidence was obtained of Y-linked influences on response acquisition, body weight, right-side hippocampus weight, and hippocampal asymmetry, whereas direct effects of autosome 9 were indicated with regard to right-side hippocampus weight only. However, epistatic interactions of the Y chromosome with autosome 9 were found for response acquisition and body weight and with autosome 4 for hippocampal asymmetry.     

海马CA1区穿孔突触数与联合学习成绩优良相关性

目的：研究联合学习是否伴有海马内突触的形态学变化。方法：对小鼠进行行为训练(联合学习),然后根据成绩分绩优组和绩低组。取海马CA1区辐射层作超薄切片,电镜观察,并定量研究单位切片面积内的突触数。结果：与对照组相比,绩优组的穿孔突触数显著增加了2倍,而绩低组无显著变化。结论：小鼠海马CA1区的穿孔突触增多是联合学习成绩优良的重要形态基础。     

Impaired dental cytodifferentiation in Glial cell-line derived growth factor (GDNF) deficient mice

Glial cell line-derived neurotrophic factor promotes the survival of multiple neuron types in the central and peripheral nervous system. Moreover, it plays a key role in the development of the enteric nervous system and in the kidney organogenesis. Glial cell line-derived neurotrophic factor and their receptors are expressed in the developing tooth as well as in the trigeminal ganglion. However, the precise role of this growth factor in tooth morphogenesis and cell differentiation, or in the development of trigeminal ganglion cells, is still elusive. Using structural and ultrastructural techniques we analyzed in detail the first molar tooth germ of glial cell line-derived neurotrophic factor deficient mice as well as the neuronal density in trigeminal ganglion. The length and width of first molar tooth germ in knockout deficient animals showed no differences in the knockout animals in comparison with age-matched heterozygous or wild-type littermates. Nevertheless, in mice lacking glial cell line-derived neurotrophic factor, both ameloblasts and odontoblasts failed to fully develop and differentiate, and the enamel matrix and predentin layers were absent. On the other hand, the number of trigeminal sensory neurons and the structure of the nerves supplying first molar tooth germ were largely normal. Present results suggest a new non-neuronal role for glial cell line-derived neurotrophic factor in tooth development. Glial cell line-derived neurotrophic factor seems not to be involved in tooth initiation and morphogenesis, whereas it seems essential for cytodifferentiation. Conversely, neither development of trigeminal neuron nor nerve fibers supplying teeth are directly dependent on glial cell line-derived neutrophic factor.     

5-羟色胺3A受体在成年小鼠海马中间神经元中的分布

目的:利用成年5-HT3AR-BACEGFP转基因小鼠,研究5-羟色胺3A受体(5-HT3AR)在海马中间神经元中的分布情况。方法:成年5-HT3AR-BACEGFP转基因小鼠经心脏灌注固定后,利用免疫荧光双标记方法,并结合激光共焦显微镜扫描技术,观察5-HT3AR在成年5-HT3AR-BACEGFP转基因小鼠海马中不同中间神经元内的表达和分布情况。结果:5-HT3AR在成年小鼠整个海马中都有分布,且主要在CA1区、CA2/CA3区和齿状回有大量5-HT3AR免疫阳性细胞;激光共聚焦显微镜下观察到5-HT3AR阳性产物在细胞核、细胞浆和树突上均有表达;免疫荧光双标实验结果表明5-HT3AR阳性产物在CB(calbindin),CR(calretinin),Reelin,Som(somatostatin),NPY(neuropeptide Y)和VIP(vasoactive intestinal peptide)免疫阳性神经元中表达,但在PV(parvalbumin)免疫阳性神经元中不表达。定量结果显示:几乎所有的VIP阳性神经元均表达5-HT3AR阳性,约3/4的CR阳性神经元表达5-HT3AR,约1/2的CB、Reelin、NPY和Som阳性神经元表达5-HT3AR阳性;约1/4的5-HT3AR阳性神经元中表达Reelin,1/5的表达Som,5-HT3AR/CB和5-HT3AR/CR双标神经元各占5-HT3AR阳性神经元的1/10左右。结论:5-HT3AR-BACEGFP转基因小鼠能够作为研究海马中5-HT3AR功能及其在中间神经元中的作用机制研究的工具鼠。     

A role for synaptopodin and the spine apparatus in hippocampal synaptic plasticity

Spines are considered sites of synaptic plasticity in the brain and are capable of remodeling their shape and size. A molecule that has been implicated in spine plasticity is the actin-associated protein synaptopodin. This article will review a series of studies aimed at elucidating the role of synaptopodin in the rodent brain. First, the developmental expression of synaptopodin mRNA and protein were studied; secondly, the subcellular localization of synaptopodin in hippocampal principal neurons was analyzed using confocal microscopy as well as electron microscopy and immunogold labelling; and, finally, the functional role of synaptopodin was investigated using a synaptopodin-deficient mouse. The results of these studies are: (1) synaptopodin expression by hippocampal principal neurons develops during the first postnatal weeks and increases in parallel with the maturation of spines in the hippocampus. (2) Synaptopodin is sorted to the spine compartment, where it is tightly associated with the spine apparatus, an enigmatic organelle believed to be involved in calcium storage or local protein synthesis. (3) Synaptopodin-deficient mice generated by gene targeting are viable but lack the spine apparatus organelle. These mice show deficits in synaptic plasticity as well as impaired learning and memory. Taken together, these data implicate synaptopodin and the spine apparatus in the regulation of synaptic plasticity in the hippocampus. Future studies will be aimed at finding the molecular link between synaptopodin, the spine apparatus organelle, and synaptic plasticity.     

Caspase-3 activity in hippocampal slices reflects changes in synaptic plasticity

Electrophysiological measures of the functional activity of neurons in field CA1 in conditions of paired-pulse stimulation of Sch?ffer collaterals were performed in relation to the involvement of caspase-3 in mediating neuroplasticity; the relationship between functional activity and caspase-3 activity in hippocampal slices from Wistar rats was addressed. Enzyme activity was assessed in each individual slice at the end of the electrophysiological experiment. The results obtained here showed that the highest level of enzyme activity was seen when the efficiency of interneuronal interactions decreased. Nerve cell excitability showed no changes; interactions increasing synaptic efficiency, particularly in paired-pulse stimulation, produced normal response amplitudes. Further deterioration of the functional state of slices and impairments in spike generation were accompanied by increases in caspase-3 activity to the normal level. Increases in the activity of another proteinase, cathepsin B, were generally seen in any deviation from normal functioning, though there was no correlation with any of the electrophysiological parameters. It is suggested that high caspase-3 activity in slices is linked with neuroplastic processes in synapses and has no direct relationship to nerve cell apoptosis. Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 94, No. 1, pp. 3–13, January, 2008.     

Nociception increases during opioid infusion in opioid receptor triple knock-out mice

Opioids are extensively used analgesics yet can paradoxically increase pain sensitivity in humans and rodents. This hyperalgesia is extensively conceptualized to be a consequence of opioid receptor activity, perhaps providing an adaptive response to analgesia, and to utilize N-methyl-D-aspartate (NMDA) receptors. These assumptions were tested here in opioid receptor triple knock-out (KO) mice lacking all three genes encoding opioid receptors (mu, delta, and kappa) by comparing their thermal nociceptive responses to the opioids morphine and oxymorphone with those of B6129F(1) controls. Injecting acute opioid bolus doses in controls caused maximal analgesia that was completely abolished in KO mice, confirming the functional consequence of the KO mouse opioid receptor deficiency. Continuous opioid infusion by osmotic pump in control mice also initially caused several consecutive days of analgesia that was shortly thereafter followed by several consecutive days of hyperalgesia. In contrast, continuously infusing KO mice with opioids caused no detectable analgesic response, but only immediate and steady declines in nociceptive thresholds culminating in several days of unremitting hyperalgesia. Finally, injecting the non-competitive NMDA receptor antagonist MK-801 during opioid infusion markedly reversed hyperalgesia in control but not KO mice. These data demonstrate that sustained morphine and oxymorphone delivery causes hyperalgesia independently of prior or concurrent opioid or NMDA receptor activity or opioid analgesia, indicating the contribution of mechanisms outside of current conceptions, and are inconsistent with proposals of hyperalgesia as a causative factor of opioid analgesic tolerance.     

PSD-95参与大鼠孕期铅暴露对子代海马突触影响的实验研究

目的:研究大鼠孕期铅暴露后子代海马突触变化与PSD-95表达改变的相关性,探讨铅暴露损伤学习记忆功能的机制。方法:通过饮用0.02%醋酸铅水溶液建立孕期铅暴露模型,利用原子吸收分光光度仪检测血铅,透射电镜技术检测海马突触密度,蛋白印记技术检测子代大鼠海马组织中VGLUT、VGAT和PSD-95的表达。结果:对照组和铅暴露组雄性21 d大鼠体重分别为(55.73±4.23)g和(56.01±5.97)g,无显著差异(P0.05);对照组与铅暴露组雄性21 d大鼠血铅分别为(10.2±2.1)μg/L和(301.2±34.8)μg/L,血铅水平明显升高(P0.01);对照组与铅暴露组雄性21 d大鼠单位面积突触数目分别为32.79±2.03和23.46±1.97,突触密度明显减少(P0.01);铅暴露后,VGAT的表达量没有明显变化(P0.05),VGLUT和PSD-95的表达量明显减少(P0.01)。结论:PSD-95表达减少引起海马兴奋性突触数目的下降是发育期铅暴露损伤学习记忆功能的可能机制。     

Impaired hippocampal long-term potentiation in melatonin MT2 receptor-deficient mice

The pineal product melatonin that acts on specific melatonin receptors has been implicated in pathobiological mechanisms of neuropsychiatric disorders including Alzheimer's disease. We used mice lacking melatonin MT(2) receptors (MT(2) knockouts) to investigate the role of these receptors in synaptic plasticity and learning-dependent behavior. In field CA1 of hippocampal slices from wild-type mice, theta burst stimulation induced robust and stable long-term potentiation that was smaller and decremental in slices from MT(2) knockouts. Tested in an elevated plus-maze on two consecutive days, wild-type mice showed shorter transfer latencies to enter a closed arm on the second day; this experience-dependent behavior did not occur in MT(2) knockouts. These results suggest that MT(2) receptors participate in hippocampal synaptic plasticity and in memory processes.     

小鼠海马CA1区轴棘突触树突棘头与突触后致密体大小的相关性

目的探讨小鼠海马CA1区兴奋性轴棘突触树突棘头与突触后致密体(postsynaptic density,PSD)是否存在大小的相关性.方法利用Golgi染色、超薄连续切片及NIH图像分析系统测量海马CA1区锥体细胞树突棘头及突触后致密体的大小.结果光镜下测量海马CA1区第2、3级顶树突的树突棘头平均面积为(0.429±0.230)μm2,频数分布为正偏态分布曲线.电镜所测树突棘头的平均体积为(0.032 63±0.024 03)μm3;PSD平均体积为(0.002 318±0.001 362)μm3,PSD与树突棘头体积之比为0.106±0.035.树突棘头体积频数分布曲线和PSD体积频数的分布曲线非常相似,两者呈显著的正相关.结论海马CA1区轴棘突触的树突棘头大小与其突触后致密体的大小具有显著的相关性.     

Ovarian morphometrics in TP53‐deficient mice

The objective of these investigations was to characterize ovarian responses to hormonal stimulation in TP53‐deficient mice. TP53‐deficient (KO) and wild‐type (WT) mice were induced to ovulate with pregnant mare serum gonadotropin followed by human chorionic gonadotropin. Effect of estradiol on ovarian morphology was determined in induced and control mice implanted with estradiol‐containing or placebo pellets. Blood was collected and mice were killed 7 days following implantation. Preserved ovaries were serially sectioned and stained. Numbers of follicles (all classifications) decreased with ovulation induction, but did not differ between WT and KO mice. Numbers of corpora lutea (CL) were less in ovulation‐induced KO mice treated with estradiol compared to WT mice. Area of individual CL and serum concentrations of progesterone were greater in ovulation‐induced KO mice given estradiol compared to WT mice. Ovulation‐induced KO mice had more, larger hemorrhagic follicles than similarly treated WT mice, but hemorrhagic follicles were not influenced by estradiol. Proliferation of ovarian surface epithelial cells did not differ between KO and WT mice induced to ovulate and given estradiol. Ovaries from TP53 gene knockout mice (n = 4) induced to ovulate and given a 21‐day estradiol implant three times over 58 days were observed for precursor lesions. There was no indication of precursor lesions in any TP53 KO or WT mouse. TP53 status did not influence recruitment of follicles, but TP53 deficiency hindered the ability of human chorionic gonadotropin to cause ovulation. Anat Rec, 290:59–64, 2007. © 2006 Wiley‐Liss, Inc.     

Epothilone D对体外培养的BTBR小鼠皮质神经元兴奋性突触结构的影响

目的： 探讨微管稳定剂埃博霉素D（Epo D）对孤独症谱系障碍BTBR小鼠皮质神经元兴奋性突触结构的影 响及机制。方法： 体外培养BTBR小鼠原代大脑皮质神经元,免疫荧光法检测所培养神经元的纯度;培养至相对 成熟的BTBR小鼠皮质神经元随机分为实验组（Epo D 组）、溶剂对照组（0.1% DMSO）干预24 h,再冷处理90 min 后行微管免疫荧光染色,观察微管的形态变化;免疫印迹检测微管稳定的标志蛋白（acetyl-tubulin、α-tubulin）、 微管相关蛋白（MAP2、STOP）的表达,及兴奋性突触结构前、后膜标志蛋白（VGLUT1、PSD95）、兴奋性谷氨 酸受体相关蛋白（GluN2B、mGluR5）的表达水平。结果：与对照组相比,10 nmol/L 的Epo D 可增加BTBR小鼠 皮质神经元微管的冷稳定性及微管稳定的标志蛋白、微管相关蛋白的表达;可以增加BTBR小鼠皮质神经元兴奋 性突触结构、兴奋性谷氨酸受体相关蛋白的表达,差异均有统计学意义。结论：微管稳定剂Epo D能改善体外培 养的BTBR小鼠皮质神经元兴奋性突触结构,其机制可能与增加微管稳定性有关。     

Impaired T cell function in RANTES-deficient mice

The chemokine RANTES is a chemoattractant for monocytes and T cells and is postulated to participate in many aspects of the immune response. To evaluate the biological roles of RANTES in vivo, we generated RANTES-deficient (-/-) mice and characterized their T cell function. In cutaneous delayed-type hypersensitivity assays, a 50% reduction in ear and footpad swelling was seen in -/- mice compared to +/+ mice. In vitro, polyclonal and antigen-specific T cell proliferation was decreased. Quantitative analysis using the fluorescent dye carboxy-fluorescein succinimidyl ester revealed that this proliferative defect was due both to fewer antigen-reactive T cells and to a reduction in the capacity of these cells to proliferate. In addition, IFN-gamma and IL-2 production by the -/- T cells was dramatically decreased. Together, these data suggest that RANTES is required for normal T cell functions as well as for recruiting monocytes and T cells to sites of inflammation.