Blocking beta 2-adrenergic receptor inhibits dendrite ramification in a mouse model of Alzheimer's disease

Dendrite ramification affects synaptic strength and plays a crucial role in memory. Previous studies revealed a correlation between beta 2-adrenergic receptor dysfunction and Alzheimer's disease(AD), although the mechanism involved is still poorly understood. The current study investigated the potential effect of the selective β2-adrenergic receptor antagonist, ICI 118551(ICI), on Aβ deposits and AD-related cognitive impairment. Morris water maze test results demonstrated that the performance of AD-transgenic(TG) mice treated with ICI(AD-TG/ICI) was significantly poorer compared with Na Cl-treated AD-TG mice(AD-TG/Na Cl), suggesting that β2-adrenergic receptor blockage by ICI might reduce the learning and memory abilities of mice. Golgi staining and immunohistochemical staining revealed that blockage of the β2-adrenergic receptor by ICI treatment decreased the number of dendritic branches, and ICI treatment in AD-TG mice decreased the expression of hippocampal synaptophysin and synapsin 1. Western blot assay results showed that the blockage of β2-adrenergic receptor increased amyloid-β accumulation by downregulating hippocampal α-secretase activity and increasing the phosphorylation of amyloid precursor protein. These findings suggest that blocking the β2-adrenergic receptor inhibits dendrite ramification of hippocampal neurons in a mouse model of AD.     

慢性给予应激水平的糖皮质激素对海马神经元和突触的影响

为探讨慢性给予应激水平糖皮质激素对大鼠海马的影响,在实验组大鼠饮用水中加入皮质醇,使动物皮质醇吸收量达每日10mg/kg,从而引起与应激动物相同的皮质醇水平,共21d,然后用免疫组织化学和免疫印迹法观察海马内caspase-3、synap-tophysin(Syn)和neurogranin(Ng)表达的变化。结果显示:(1)实验组大鼠海马结构中可见较多细胞出现核固缩的病理改变,但未见或偶见极个别caspase-3免疫反应阳性细胞;(2)与正常组Syn表达水平(1.2197±0.3443)和Ng表达水平(1.9330±0.3450)相比,实验组大鼠海马结构中Syn和Ng的表达明显减少(P<0.05),其表达水平分别为0.5512±0.0540和1.3375±0.3317。上述结果表明慢性给予应激水平的糖皮质激素可损伤海马功能,引起不依赖caspase-3的海马神经细胞退变、使海马突触数量减少以及改变海马突触效能可能是其作用的部分机制。     

Behavior‐associated Neuronal Activation After Kainic Acid‐induced Hippocampal Neurotoxicity is Modulated in Time

Kainic acid‐induced (KA) hippocampal damage leads to neuronal death and further synaptic plasticity. Formation of aberrant as well as of functional connections after such procedure has been documented. However, the impact of such structural plasticity on cell activation along time after damage and in face of a behavioral demand has not been explored. We evaluated if the mRNA and protein levels of plasticity‐related protein synaptophysin (Syp and SYP, respectively) and activity‐regulated cytoskeleton‐associated protein mRNA and protein levels (Arc and Arc, respectively) in the dentate gyrus were differentially modulated in time in response to a spatial‐exploratory task after KA‐induced hippocampal damage. In addition, we analyzed Arc+/NeuN+ immunopositive cells in the different experimental conditions. We infused KA intrahippocampally to young‐adult rats and 10 or 30 days post‐lesion (dpl) animals performed a hippocampus‐activating spatial‐exploratory task. Our results show that Syp mRNA levels significantly increase at 10dpl and return to control levels after 30dpl, whereas SYP protein levels are diminished at 10dpl, but significantly increase at 30dpl, as compared to 10dpl. Arc mRNA and protein levels are both increased at 30dpl as compared to sham. Also the number of NeuN+/Arc+ cells significantly increases at 30dpl in the group with a spatial‐exploratory demand. These results provide information on the long‐term modifications associated to structural plasticity and neuronal activation in the dentate gyrus after excitotoxic damage and in face of a spatial‐exploratory behavior. Anat Rec, 300:425–432, 2017. © 2016 Wiley Periodicals, Inc.     

卡马西平对癫痫模型大鼠海马损伤作用及对Fascin-1、突触素表达的影响

目的研究卡马西平对癫痫模型大鼠海马损伤的作用及对肌成束蛋白(Fascin-1)、突触素(SYP)表达的影响。方法选择54只无特定病原体动物(SPF)级SD健康大鼠,选取40只建立癫痫模型,分为模型组、低剂量组、中剂量组、高剂量组,每组10只,另设10只正常大鼠为正常组。低剂量组、中剂量组、高剂量组分别给予卡马西平(质量浓度2 g/L)15 mg/kg、30 mg/kg、50 mg/kg进行治疗,采用脑电图机观察大鼠潜伏期、持续时间、波幅指标,统计发作次数、发作总时间,苏木精-伊红染色法(HE)染色处理,观察海马区细胞凋亡指数,采用蛋白质印迹法(Western Blot)检测Fascin-1、突触素、Bcl-2、Bax表达水平。结果模型组潜伏期及Fascin-1、Bcl-2表达水平低于正常组、低剂量组、中剂量组、高剂量组,持续时间、波幅、海马区细胞凋亡指数及突触素、Bax表达水平高于正常组、低剂量组、中剂量组、高剂量组,差异均有统计学意义(P<0.05)。卡马西平各剂量组潜伏期高于模型组,持续时间、波幅、海马区细胞凋亡指数低于模型组,差异具有统计学意义(P<0.05)。中剂量组潜伏期、Fascin-1、Bcl-2表达水平高于低剂量组和高剂量组,持续时间、波幅、发作次数、发作总时间、海马区细胞凋亡指数及突触素、Bax表达水平低于低剂量组和高剂量组,差异有统计学意义(P<0.05)。结论卡马西平能降低癫痫模型大鼠海马损伤程度,起到一定的抗癫痫作用,可能与调控Fascin-1、突触素、Bcl-2、Bax表达水平有关。     

Organ of Corti explants direct tonotopically graded morphology of spiral ganglion neurons in vitro

The spiral ganglion is a compelling model system to examine how morphological form contributes to sensory function. While the ganglion is composed mainly of a single class of type I neurons that make simple one‐to‐one connections with inner hair cell sensory receptors, it has an elaborate overall morphological design. Specific features, such as soma size and axon outgrowth, are graded along the spiral contour of the cochlea. To begin to understand the interplay between different regulators of neuronal morphology, we cocultured neuron explants with peripheral target tissues removed from distinct cochlear locations. Interestingly, these “hair cell microisolates” were capable of both increasing and decreasing neuronal somata size, without adversely affecting survival. Moreover, axon characteristics elaborated de novo by the primary afferents in culture were systematically regulated by the sensory endorgan. Apparent peripheral nervous system (PNS)‐like and central nervous system (CNS)‐like axonal profiles were established in our cocultures allowing an analysis of putative PNS/CNS axon length ratios. As predicted from the in vivo organization, PNS‐like axon bundles elaborated by apical cocultures were longer than their basal counterparts and this phenotype was methodically altered when neuron explants were cocultured with microisolates from disparate cochlear regions. Thus, location‐dependent signals within the organ of Corti may set the “address” of neurons within the spiral ganglion, allowing them to elaborate the appropriate tonotopically associated morphological features in order to carry out their signaling function. J. Comp. Neurol. 524:2182–2207, 2016. © 2015 Wiley Periodicals, Inc.     

重复经颅磁刺激对脑缺血大鼠海马突触素表达及学习记忆的影响

目的:观察10 Hz重复经颅磁刺激(r TMS)对脑缺血大鼠海马突触素(SYN)的表达及学习记忆的影响。方法:将36只雄性SD大鼠随机分成假手术组、模型组和r TMS组,每组12只。制备双侧颈总动脉永久结扎脑缺血模型,假手术组不造成缺血,r TMS组给予10 Hz r TMS,共28次。采用Morris水迷宫评价学习记忆能力;利用电生理实验检测海马CA1区的长时程增强(LTP);Western blot检测海马SYN蛋白的含量。结果:与假手术组比较,模型组的逃避潜伏期明显延长,60 s内跨越平台次数减少;与模型组比较,r TMS组大鼠的逃避潜伏期缩短,60 s内跨越平台次数增加,f EPSP波幅提高,海马SYN蛋白的表达增高,差异有统计学意义(P0.05)。结论:r TMS能促进脑缺血大鼠海马SYN蛋白的表达和增强高频刺激引起的LTP,这可能是r TMS改善脑缺血损伤引起的学习记忆障碍的作用机制之一。     

麻黄碱对缺氧缺血性脑损伤后新生大鼠脑组织Nogo-A和突触素表达的影响

背景：围产期窒息所致的新生儿缺氧缺血性脑损伤（hypoxic ischemic brain damage HIBD）是严重威胁新生儿生命和健康的常见病之一,而髓鞘相关蛋白Nogo-A等抑制神经生长的因子的存在,形成了一个不利于神经再生与修复的微环境。新近研究表明,Nogo-A主要存在于髓磷脂和少突胶质中,调控着脑缺血损伤后神经锥再生抑制的病理发展过程,在中枢神经系统再生修复中起着重要作用。然而对于Nogo-A在缺氧缺血性脑组织中表达的干预尚需深入研究。 目的：探讨髓鞘相关蛋白Nogo-A和突触素在缺氧缺血性脑损伤新生大鼠脑组织的表达特点及麻黄碱对其表达的影响。 设计,时间和单位：完全随机设计,实验于2008年8月至2009年3月在重庆医科大学附属儿童医院儿研所免疫组化实验室完成,为重庆市重点实验室。 材料：Sprague-Dawley (SD) 妊娠大鼠由重庆医科大学附属儿童医院实验动物中心提供,分笼单独喂养,提供水和实验室饲料。96只自然分娩新生鼠由母鼠喂养。 方法：健康SD新生大鼠96只,随机分为假手术组,HIBD组和麻黄碱治疗组,每组32只。于7日龄行左侧颈总动脉结扎,吸入8%O2+ 92%N2混合气体行缺氧处理2小时,制成HIBD模型。假手术组只作左颈总动脉分离而不结扎,不作缺氧处理。麻黄碱组于建模成功后腹腔注射麻黄碱1.5 mg•kg-1,假手术组和HIBD组大鼠腹腔注射等量生理盐水。上述各组干预均为每日1次,共7日。 主要观察指标：术后1、2、3、4周,各组大鼠均随机抽取8只,于麻醉下处死取脑,HE染色观察脑组织病理变化,免疫组化法检测髓鞘相关蛋白Nogo-A和突触素表达情况。 结果：假手术组各时间点大鼠脑组织Nogo-A表达无明显变化,差异无统计学意义( P > 0.05);与假手术组相比,HIBD组术后各时间点脑组织Nogo-A表达均增高,差异有统计学意义( P < 0.01);与HIBD组相比,麻黄碱治疗组第2,3,4周Nogo-A表达明显减少,差异有统计学意义( P < 0.01)。与假手术组相比,HIBD组术后各时间点脑组织突触素表达均减少,差异有统计学意义( P < 0.01);与HIBD组相比,麻黄碱治疗组第1,2,3周突触素表达明显增加,差异有统计学意义( P < 0.01)。 结论：新生大鼠HIBD后脑组织Nogo-A表达增高,可能是中枢神经损伤后再生障碍的重要因素之一。麻黄碱可下调脑组HIBD后Nogo-A 的表达,促进突触素的表达,从而有利于新生动物HIBD后神经轴突的再生。     

Reflex and Morphological Changes in Spinal Preganglionic Neurons After Cord Injury in Rats

Autonomic dysreflexia manifested as episodic hypertension after spinal cord injury may occur because of changes in sympathetic preganglionic neurons (SPNs) in response to loss of bulbospinal inputs. We studied dysreflexia in rats one week after midthoracic spinal cord hemisection or complete transection. After cord hemisection at the fifth thoracic segment all rats had hemiparaplegia and after complete transection they were paraplegic and exhibited dysreflexia characterized by pressor responses to distension of the urinary bladder. Changes in morphology of SPNs retrogradely labelled by cholera toxin and Fluoro Gold were examined and changes also were assessed in expression of the synaptic vesicular protein synaptophysin. A comparison of SPNs rostral and caudal to the lesion revealed significant dendritic degeneration and decreased soma size after the loss of supraspinal input. Expression of synaptophysin was normally observed rostral to a cord hemisection but this immunoreactivity was increased caudal to the lesion. In conclusion significant structural changes in SPNs occur within a week after cord injury. The abnormal cardiovascular control and exaggerated reflex reactions may be due to new synapse formation on these SPNs.     

Spatial relationship between synapse loss and beta-amyloid deposition in Tg2576 mice

Although there is evidence that beta-amyloid impairs synaptic function, the relationship between beta-amyloid and synapse loss is not well understood. In this study we assessed synapse density within the hippocampus and the entorhinal cortex of Tg2576 mice at 6-18 months of age using stereological methods at both the light and electron microscope levels. Under light microscopy we failed to find overall decreases in the density of synaptophysin-positive boutons in any brain areas selected, but bouton density was significantly decreased within 200 mum of compact beta-amyloid plaques in the outer molecular layer of the dentate gyrus and Layers II and III of the entorhinal cortex at 15-18 months of age in Tg 2576 mice. Under electron microscopy, we found overall decreases in synapse density in the outer molecular layer of the dentate gyrus at both 6-9 and 15-18 months of age, and in Layers II and III of the entorhinal cortex at 15-18 months of age in Tg 2576 mice. However, we did not find overall changes in synapse density in the stratum radiatum of the CA1 subfield. Furthermore, in the two former brain areas we found a correlation between lower synapse density and greater proximity to beta-amyloid plaques. These results provide the first quantitative morphological evidence at the ultrastructure level of a spatial relationship between beta-amyloid plaques and synapse loss within the hippocampus and the entorhinal cortex of Tg2576 mice.     

Effects of Naotan Pill on repair of neural cells and cognitive disorders in juvenile rats following hypoxia and ischemia

BACKGROUND:Hypoxia and ischemia induce neuronal damage,decreased neuronal numbers and synaptophysin levels,and deficits in learning and memory functions.Previous studies have shown that lycium barbarum polysaccharide,the most effective component of barbary wolfberry fruit,has protective effects on neural cells in hypoxia-ischemia.OBJECTIVE:To investigate the effects of Naotan Pill on glutamate-treated neural cells and on cognitive function in juvenile rats following hypoxia-ischemia.DESIGN,TIME AND SETTING:The randomized,controlled,in vivo study was performed at the Cell Laboratory of Lanzhou University,Lanzhou Institute of Modern Physics of Chinese Academy of Sciences,and Department of Traditional Chinese Medicine of Gansu Provincial Rehabilitation Center Hospital,China from December 2005 to August 2006.The cellular neurobiology,in vitro experiment was conducted at the Institute of Human Anatomy,Histology,Embryology and Neuroscience,School of Basic Medical Sciences,Lanzhou University,and Department of Traditional Chinese Medicine of Gansu Provincial Rehabilitation Center Hospital,China from March 2007 to January 2008.MATERIALS:Naotan Pill,composed of barbary wolfberry fruit,danshen root,grassleaf sweetflag rhizome,and glossy privet fruit,was prepared by Gansu Provincial Rehabilitation Center,China.Rabbit anti-synaptophysin,choline acetyl transferase polyclonal antibody,streptavidin-biotin complex kit and diaminobenzidine kit (Boster,Wuhan,China),as well as glutamate (Hualian,Shanghai,China) were used in this study.METHODS:Cortical neural cells were isolated from neonatal Wistar rats.Neural cell damage models were induced using glutamate,and administered Naotan Pill prior to and following damage.A total of 54 juvenile Wistar rats were equally and randomly assigned into model,Naotan Pill,and sham operation groups.The left common carotid artery was ligated,and then rat models of hypoxic-ischemic injury were assigned to the model and Naotan Pill groups.At 2 days following model induction,rats in the Naotan Pill group were administered Naotan Pill suspension for 21 days.In the model and sham operation groups,rats received an equal volume of saline.MAIN OUTCOME MEASURES:Neural cell morphology was observed using an inverted phase contrast microscope.Survival rate of neural cells was measured by MTT assay.Synaptophysin and choline acetyl transferase expression was observed in the hippocampal CA1 region of juvenile rats using immunohistochemistry.Cognitive function was tested by the Morris water maze.RESULTS:Pathological changes were detected in glutamate-treated neural cells.Neural cell morphology remained normal after Naotan Pill intervention.Absorbance and survival rate of neural cells were significantly greater following Naotan Pill intervention,compared to glutamate-treated neural cells (P<0.05).Synaptophysin and choline acetyl transferase expression was lowest in the hippocampal CA1 region in the model group and highest in the sham operation group.Significant differences among groups were observed (P<0.05).Escape latency and swimming distance were significantly longer in the model group compared to the Naotan Pill group (P<0.05).CONCLUSION:Naotan Pill exhibited protective and repair effects on glutamate-treated neural cells.Naotan Pill upregulated synaptophysin and choline acetyl transferase expression in the hippocampus and improved cognitive function in rats following hypoxia-ischemia.