Sim2基因对PC12细胞分化的影响

[摘要] 目的 探讨位于Down综合征关键位点的Sim2基因对PC12细胞分化的影响及其机制。 方法 以pcDNA3-mSim2真核表达载体稳定转染PC12细胞,以倒置相差显微镜镜观察PC12细胞神经突起的变化;以RT-PCR方法检测神经元分化相关基因GAP43和Synapsin I mRNA表达水平的变化;流式细胞仪检测GAP43蛋白的表达。 结果 RT-PCR结果显示, pcDNA3-mSim2转染后,mSim2 mRNA表达明显上调;与对照组相比,转染mSim2的PC12细胞突起数量显著减少,长度明显变短;GAP43和Synapsin I mRNA表达水平明显降低（P<0.05）;流式细胞仪检测发现,转染mSim2的PC12细胞GAP43蛋白表达水平显著降低（P<0.05）。 结论 Sim2基因可通过影响神经元的分化参与Down综合征的发生。     

Effect of mouse Sim2 gene on the cell cycle of PC12 cells

Sim2 gene plays an important role in the pathogenesis of Down syndrome (DS). To observe the effect of mouse Sim2 (mSim2) on the cell cycle of PC12 cells in vitro and explore the role of Sim2 in the pathogenesis of DS, we cloned the full open reading frame of mSim2 into the pcDNA3 vector and transfected it into PC12 cells, before analysing the effect of mSim2 on the cell cycle. A eukaryotic expression vector of mSim2 (pcDNA3-mSim2) was successfully constructed. There was notable expression of mSim2 mRNA in the cells transfected with pcDNA3-Sim2. Flow cytometry showed that there were more cells in G(0)/G(1) phase in the Sim2-transfected cells than that in the controls (P < 0.01), and significantly fewer in G(2)/M phase (P < 0.01). The mRNA and protein expressions of cyclin E decreased in the Sim2-transfected cells, while p27 expression increased significantly (P < 0.01). It is concluded that Sim2 may play an important role in the pathogenesis of DS by inhibiting the cell cycle, which is related to the decreased expression of cyclin E and increased expression of p27.     

Sim2基因对PC12细胞周期的影响

观察Sim2基因对PC12细胞周期及细胞周期调控蛋白表达水平影响,初步阐明Sim2基因在Down综合征发病机制中的作用.以脂质体法将pcDNA3-mSim2真核表达载体瞬时转染PC12细胞;以RT-PCR方法检测mSim2基因在PC12细胞的表达;流式细胞仪观察细胞周期分布的变化;RT-PCR和免疫组织化学方法分别检测细胞周期调节蛋白Ｅ（cyclin E）和p27 mRNA和蛋白水平的表达变化.RT-PCR结果显示,瞬时转染pcDNA3-mSim2的PC12细胞中有明显的mSim2 mRNA表达;流式细胞仪检测发现,与对照组和空载体组相比,转染mSim2后,处于G₀/G₁期的PC12细胞百分比明显升高（Ｐ<0.01）,而G₂/M期的细胞百分比明显降低 (Ｐ<0.01);在mRNA和蛋白水平上,转染mSim2的细胞细胞周期蛋白E表达较对照组明显降低;而p27的表达明显升高(Ｐ<0.01).以上结果表明,mSim2基因可能通过影响神经元前体细胞的增殖在Down综合征发病机制中发挥了重要作用.     

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.     

Fluoride and Arsenic Exposure Impairs Learning and Memory and Decreases mGluR5 Expression in the Hippocampus and Cortex in Rats

Fluoride and arsenic are two common inorganic contaminants in drinking water that are associated with impairment in child development and retarded intelligence. The present study was conducted to explore the effects on spatial learning, memory, glutamate levels, and group I metabotropic glutamate receptors (mGluRs) expression in the hippocampus and cortex after subchronic exposure to fluoride, arsenic, and a fluoride and arsenic combination in rats. Weaned male Sprague-Dawley rats were assigned to four groups. The control rats drank tap water. Rats in the three exposure groups drank water with sodium fluoride (120 mg/L), sodium arsenite (70 mg/L), and a sodium fluoride (120 mg/L) and sodium arsenite (70 mg/L) combination for 3 months. Spatial learning and memory was measured in Morris water maze. mGluR1 and mGluR5 mRNA and protein expression in the hippocampus and cortex was detected using RT-PCR and Western blot, respectively. Compared with controls, learning and memory ability declined in rats that were exposed to fluoride and arsenic both alone and combined. Combined fluoride and arsenic exposure did not have a more pronounced effect on spatial learning and memory compared with arsenic and fluoride exposure alone. Compared with controls, glutamate levels decreased in the hippocampus and cortex of rats exposed to fluoride and combined fluoride and arsenic, and in cortex of arsenic-exposed rats. mGluR5 mRNA and protein expressions in the hippocampus and mGluR5 protein expression in the cortex decreased in rats exposed to arsenic alone. Interestingly, compared with fluoride and arsenic exposure alone, fluoride and arsenic combination decreased mGluR5 mRNA expression in the cortex and protein expression in the hippocampus, suggesting a synergistic effect of fluoride and arsenic. These data indicate that fluoride and arsenic, either alone or combined, can decrease learning and memory ability in rats. The mechanism may be associated with changes of glutamate level and mGluR5 expression in cortex and hippocampus.     

慢性复合应激对大鼠学习和记忆及海马神经元神经颗粒素表达的影响

目的探讨慢性复合应激对大鼠学习和记忆功能及海马内神经元神经颗粒素(neurogranin,Ng)表达的影响。方法成年雄性Wistar大鼠随机分为对照组和复合应激组,复合应激组动物每天无规律交替暴露于复合应激原环境中,为期6周。应激结束后,用Morris水迷宫测试大鼠空间学习和记忆成绩,同时用免疫组织化学方法观察海马各亚区Ng表达的变化,并用RT-PCR技术分析各组大鼠海马Ng mRNA水平的变化。结果Morris水迷宫测试显示,应激组动物寻找隐蔽平台潜伏期明显短于对照组(P<0.05);应激组大鼠海马DG和CA3区Ng的蛋白表达水平明显高于对照组(P<0.05),而两组海马CA1区的Ng的免疫反应性无明显差别;与对照组相比,应激组动物的Ng mRNA水平亦明显上调(P<0.05)。结论慢性复合性应激大鼠的学习与记忆能力增强;Ng在海马中的表达和Ng mRNA转录水平增高,提示Ng参与了该增强机制。     

戊四氮点燃癫痫大鼠空间学习记忆改变及海马突触素、突触后致密物PSD-95表达的变化

目的探讨戊四氮点燃癫痫对大鼠空间学习记忆的影响及可能的分子机制。方法戊四氮(pentylenetet-razol,PTZ)点燃建立慢性癫痫(chronic epileptic,CEP)模型,Morris水迷宫进行行为学检测,免疫组织化学方法观察大鼠海马CA1、CA3区突触素(synaptophysin,P38)和突触后致密物95(postsynaptic density 95,PSD-95)的表达,并用计算机图像分析系统对免疫反应结果进行处理。结果水迷宫试验检测癫痫组大鼠空间学习记忆能力受损;免疫组化结果表明其海马CA1、CA3区P38和PSD-95免疫反应产物较对照组明显减少(P<0.01,P<0.05)。结论戊四氮点燃癫痫大鼠伴有学习记忆功能减退,其海马神经元P38和PSD-95的表达减少可能参与了空间学习记忆受损。     

TRP 对KA 诱导的AD 模型大鼠学习记忆的影响及其作用机制

目的:观察雷公藤甲素(Triptolide,TRP)对海人藻酸(Kainic acid,KA)海马内注射后大鼠学习记忆的影响及其作用机制。方法:采用Morris水迷宫筛选空间学习记忆能力正常的SD雄性大鼠90只(200～220g)。将实验动物分成3组:右侧海马注射生理盐水后生理盐水灌胃对照组(NS+NS)、右侧海马注射海人藻酸后生理盐水灌胃干预组(KA+NS)、右侧海马注射海人藻酸后雷公藤甲素灌胃干预组(KA+TRP)。动物存活1天,3天,5天,7天,14天,每个时间点6只,处死前分别于各相应时间点用Morris水迷宫检测各组动物空间位置记忆能力;免疫组织化学方法结合图像分析技术检测海马CA1区神经元COX-2的表达。结果:与NS组(NS+NS)比较,KA组(KA+NS)大鼠逃避潜伏期延长(P<0.05),跨越原平台次数减少(P<0.05);海马CA1区的神经元COX-2表达升高(P<0.05);TRP组(TRP+KA)与KA组比较,大鼠的平均逃避潜伏期从第5天起缩短(P<0.05),跨越原平台次数增多(P<0.05),海马CA1区神经元COX-2表达在5天,7天时下调(P<0.05)。结论:KA海马内注射,可以导致大鼠学习记忆功能障碍及上调海马CA1区神经元COX-2表达;雷公藤甲素干预治疗,能够改善动物的学习和记忆能力,能抑制KA诱导的海马CAl区神经元COX-2的表达。     

Altered expression of NCAM in hippocampus and cortex may underlie memory and learning deficits in rats with streptozotocin-induced diabetes mellitus

Neurological and structural changes are paralleled by cognitive deficits in diabetes mellitus. The present study was designed to evaluate the expression of neural cell adhesion molecules (NCAM) in the hippocampus, cortex and cerebellum and to examine cognitive functions in diabetic rats. Diabetes was induced in male albino rats via intraperitoneal streptozotocin injection. Learning and memory behaviors were investigated using a passive avoidance test and a spatial version of the Morris water maze test. NCAM expression was detected in the hippocampus, cortex and cerebellum by an immunoblotting method. The diabetic rats developed significant impairment in learning and memory behaviours as indicated by deficits in passive avoidance and water maze tests as compared to control rats. Expression of NCAM 180 and 120 kDa were found to be higher in hippocampus and cortex of diabetic rat brains compared to those of control, whereas expression of NCAM 140 kDa decreased in these brain regions. Our findings suggest that streptozotocin-induced diabetes impairs cognitive functions and causes an imbalance in expression of NCAM in those brain regions involved in learning and memory. Altered expression of NCAM in hippocampus may be an important cause of learning and memory deficits that occur in diabetes mellitus.     

Alpha1-adrenergic receptor antagonist tamsulosin ameliorates aging-induced memory impairment by enhancing neurogenesis and suppressing apoptosis in the hippocampus of old-aged rats

Age-related memory decline is closely associated with decreased neurogenesis and increased apoptosis in the hippocampus. Noradrenaline exerts its effect by selectively binding to and activating adrenergic receptors (ARs). Tamsulosin, α₁-AR antagonist, is reported to have access to the brain and interact with α₁-AR. In this study, the effects of tamsulosin on short-term and spatial learning memory in terms of neurogenesis and apoptosis were investigated using rats. Step-down avoidance test for short-term memory and radial 8-arm maze test for spatial learning memory were conducted. Neurogenesis was detected by 5-bromo-2’-deoxyuridine (BrdU) immunohistochemistry and apoptosis was evaluated by caspase-3 immunohistochemisty and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNE) staining. Western blot for protein kinase C (PKC), cAMP-responsive element-binding protein (CREB), brain-derived neurotrophic factor (BDNF), tyrosine kinase B (TrkB), phosphatidylinositol 3-kinase (PI 3-kinase), Akt, Bcl-2, and Bax was conducted. In the aged rats, short-term and spatial learning memory was declined. Hippocampal nerogenesis was suppressed and hippocampal apoptosis was enhanced in the aged rats. In addition, phosphorylation of PKCα, CREB, PI-3 kinase, and Akt was decreased in the hippocampus of old-aged rats. Tamsulosin activated PKC/CREB and PI-3 kinase/Akt pathways. With these pathways, BDNF-TrkB signaling enhanced hippocampal neurogenesis and suppressed apoptosis in the old-aged rats. As the results, tamsulosin improved performance of short-term and spatial learning memory in the aged rats.     

Acetyl-L-carnitine ameliorates spatial memory deficits induced by inhibition of phosphoinositol-3 kinase and protein kinase C

Glycogen synthase kinase-3β (GSK-3β) plays a crucial role in memory deficits and tau hyperphosphorylation as seen in Alzheimer's disease, the most common dementia in the aged population. We reported that ventricular co-injection of wortmannin and GF-109203X (WT/GFX) can induce tau hyperphosophorylation and memory impairment of rats through activation of GSK-3 [Liu S. J., Zhang A. H., Li H. L., Wang Q., Deng H. M., Netzer W. J., Xu H. X. and Wang J. Z. (2003) J. Neurochem. 87, 1333]. In the present study, we found that feeding the rats with Acetyl-L-Carnitine (ALCAR, 50 mg/day·rat, per os) for 2 weeks rescued the WT/GFX-induced spatial memory retention impairment of the rats by antagonizing GSK-3β activation independent of Akt, PKCζ and Erk1/2. We also found that ALCAR arrested microtubule-associated protein tau hyperphosphorylation at multiple Alzheimer's disease sites in vivo and in vitro. Moreover, ALCAR enhanced the expression of several memory-associated proteins including c-Fos, synapsin I in rat hippocampus. These results suggest that ALCAR could ameliorate WT/GFX-induced spatial memory deficits through inhibition tau hyperphosphorylation and modulation of memory-associated proteins.     

The effect of sevoflurane on the expression of M1 acetylcholine receptor in the hippocampus and cognitive function of aged rats

Our aim is to investigate the effect of 1.5 and 3.0% sevoflurane on the expression of M(1) acetylcholine receptor (mAChR M(1)) in the hippocampus and the cognitive function of aged rats. Forty Sprague-Dawley (SD) rats of 12-month old were randomly divided into five groups. All SD rats received 1.5 or 3.0% sevoflurane in a special glass anesthesia box for 2 h, respectively, except for the normal control group. Y-maze was used to test the ability of learning and memory after being received sevoflurane for 1 or 7 days at the same moment portion. The expression of mAChR M(1) in the hippocampus of rats was tested by RT-PCR. The results showed that 3% sevoflurane induced the decline of cognitive function and significantly decreased the mAChR M(1) expression at mRNA levels at 1 day in the 3.0% sevoflurane I group when compared with the normal control group. However, there was no significant difference among the other groups when compared with normal control group. Therefore, administration of sevoflurane might temporally affect the ability of cognitive function of rats through suppressing the mAChR M(1) expression at mRNA levels in hippocampus.     

Spatial Memory Impairment Is Associated with Hippocampal Insulin Signals in Ovariectomized Rats

Estrogen influences memory formation and insulin sensitivity. Meanwhile, glucose utilization directly affects learning and memory, which are modulated by insulin signals. Therefore, this study investigated whether or not the effect of estrogen on memory is associated with the regulatory effect of this hormone on glucose metabolism. The relative expression of estrogen receptor β (ERβ) and glucose transporter type 4 (GLUT4) in the hippocampus of rats were evaluated by western blot. Insulin level was assessed by ELISA and quantitative RT-PCR, and spatial memory was tested by the Morris water maze. Glucose utilization in the hippocampus was measured by 2-NBDG uptake analysis. Results showed that ovariectomy impaired the spatial memory of rats. These impairments are similar as the female rats treated with the ERβ antagonist tamoxifen (TAM). Estrogen blockade by ovariectomy or TAM treatment obviously decreased glucose utilization. This phenomenon was accompanied by decreased insulin level and GLUT4 expression in the hippocampus. The female rats were neutralized with hippocampal insulin with insulin antibody, which also impaired memory and local glucose consumption. These results indicated that estrogen blockade impaired the spatial memory of the female rats. The mechanisms by which estrogen blockade impaired memory partially contributed to the decline in hippocampal insulin signals, which diminished glucose consumption.     

电针对糖尿病大鼠学习记忆障碍及海马NT-3表达的影响

目的观察电针对糖尿病性认知功能障碍大鼠学习记忆的改善作用,及其对海马神经营养因子-3（NT-3）mRNA和免疫反应阳性细胞表达的影响。方法采用2％链脲佐菌素（streptozotocin,STZ）构建糖尿病大鼠模型,将模型大鼠随机分为电针组（EA）、对照组（DM）与正常组（CN）进行比较。电针4周后糖尿病测定血糖水平,并用Morris水迷宫法观察电针对糖尿病大鼠学习记忆的影响,应用RT-PCR和免疫组化方法检测海马NT-3mRNA和免疫反应阳性细胞的表达水平。结果对照组血糖、上台潜伏期高于正常组和电针组（P〈0．01）,对照组NT-3mRNA和免疫反应阳性细胞的表达明显低于正常组和电针组（P〈0．01）;电针组NT-3表达明显高于对照组（P〈0．01）。结论电针能在一定程度上降低血糖,促进海马NT-3mRNA和免疫反应阳性细胞的表达,改善糖尿病认知功能障碍者的学习和认知功能。     

Prenatal stress in rat causes long-term spatial memory deficit and hippocampus MRI abnormality: differential effects of postweaning enriched environment

Prenatal stress (PS) can cause long-term hippocampus alternations in structure and plasticity in adult offspring. Enriched environment (EE) has an effect in rescuing a variety of neurological disorders. Pregnant dams were left undisturbed (prenatal control, PC) or restrained 6h per day from days 14 to 21 (prenatal stress, PS). Control and prenatal stressed offspring rats were subjected to a standard rearing environment (SE) or an EE on postnatal days 22-120 (PC/SE PC/EE, PS/SE, and PS/EE; n=5, each group). At ～4 months of age, all rats underwent Morris water maze test and brain MRI examination. Hippocampi were then dissected for biochemical analyses, including, Western blot for NMDA receptor (NR) subunits and synaptophysin and RT-PCR forβ1 integrin and tissue-plasminogen activator (t-PA). MRI showed all 5 rats in the PS/SE group and 5 in the PS/EE group exhibited increased signals in bilateral hippocampus and increased T2 time in the PS/SE group. Exposure to EE treatment on postnatal days 22-120 counteracted the deficit in spatial memory and increased NR1 protein expression, but it did not affect the rate of high signals and increased T2 time, decreased NR2, synaptophysin, β1 integrin and t-PA mRNA expressions in PS adult offspring. The results of this study indicate PS in rats causes long-term spatial memory deficits and gross hippocampus pathology. Postnatal EE treatment has differential benefits in terms of spatial learning, signaling molecules, and gross hippocampus pathology.     

The expression of TRH, its receptors and degrading enzyme is differentially modulated in the rat limbic system during training in the Morris water maze

TRH administration induces arousal, improves cognition, and modulates glutamatergic and cholinergic transmission in hippocampal neurons. To study the possible involvement of TRH neurons in learning and memory processes, gene expression of TRH, its receptors, and pyroglutamyl peptidase (PPII), were measured in limbic regions of water-maze trained rats. Hypothalamus and amygdala showed changes related to the task but not specific to spatial learning while in hippocampus, pro-TRH and TRH-R1 mRNA levels were specifically increased in those animals trained to find a hidden platform. Variation of TRH content and mRNA levels of pro-TRH, TRH-R1, TRH-R2 and PPII are observed in conditions known to activate TRH hypophysiotropic neurons. Changes in some of these parameters could indicate the activation of TRHergic neurons and their possible involvement in some memory related process. Male Wistar rats were immersed (10 times) for 1, 3 or 5 days in a Morris water-maze containing, or not (yoked control) a platform and sacrificed 5, 30 and 60 min after last trial. TRH content and TSH serum levels were determined by radioimmunoassay; mRNA levels of pro-TRH, TRH-R1, TRH-R2, and PPII, by RT-PCR. Exclusive changes due to spatial training were observed in posterior hippocampus of rats trained for 5 days sacrificed after 60min: decreased TRH content and increased mRNA levels of pro-TRH and TRH-R1, particularly in CA3 region (measured by in situ hybridization). The hypothalamus-pituitary axis responded in both yoked and trained animals (increasing serum TSH levels and pro-TRH expression, due to swim-stress); in the amygdala of both groups, pro-TRH expression increased while diminished that of both receptors and PPII. Differential expression of these parameters suggests involvement of TRH hippocampal neurons in memory formation processes while changes in amygdala could relate to TRH anxiolytic role. The differential modulation in anterior and posterior portions of the hippocampus is discussed.     

Impact of early developmental arsenic exposure on promotor CpG-island methylation of genes involved in neuronal plasticity

Epigenetic mechanisms are crucial to regulate the expression of different genes required for neuronal plasticity. Neurotoxic substances such as arsenic, which induces cognitive deficits in exposed children before any other manifestation of toxicity, could interfere with the epigenetic modulation of neuronal gene expression required for learning and memory. This study assessed in Wistar rats the effects that developmental arsenic exposure had on DNA methylation patterns in hippocampus and frontal cortex. Animals were exposed to arsenic in drinking water (3 and 36ppm) from gestation until 4 months of age, and DNA methylation in brain cells was determined by flow cytometry, immunohistochemistry and methylation-specific polymerase chain reaction (PCR) of the promoter regions of reelin (RELN) and protein phosphatase 1 (PP1) at 1, 2, 3 and 4 months of age. Immunoreactivity to 5 methyl-cytosine was significantly higher in the cortex and hippocampus of exposed animals compared to controls at 1 month, and DNA hypomethylation was observed the following months in the cortex at high arsenic exposure. Furthermore, we observed a significant increase in the non-methylated form of PP1 gene promoter at 2 and 3 months of age, either in cortex or hippocampus. In order to determine whether this exposure level is associated with memory deficits, a behavioral test was performed at the same age points, revealing progressive and dose-dependent deficits of fear memory. Our results demonstrate alterations of the methylation pattern of genes involved in neuronal plasticity in an animal model of memory deficit associated with arsenic exposure.     

Protective effects of Ginkgo biloba leaf extract on aluminum-induced brain dysfunction in rats

This study examined the protective effects of Ginkgo biloba extract (GbE) on the learning and memory function in aluminum-treated rats and potential mechanisms. Wistar rats were given daily aluminum chloride 500 mg/kg, i.g, for one month, followed by continuous exposure via the drinking water containing 1600 ppm aluminum chloride for up to 5 months. The ability of spatial learning and memory was tested by Morris water maze. Aluminum administration significantly increased escape latency and searching distance, indicative of brain dysfunction. GbE treatment (50-200 mg/kg, i.g) significantly protected against aluminum-induced brain dysfunction, as evidenced by decreased escape latency and searching distance compared with the Al alone group. To examine the mechanisms of the protection, the expressions of amyloid precursor protein (APP) and caspase-3 in brain regions were examined by immunohistochemistry. GbE treatment reduced the contents of APP and caspase-3 in hippocampus of aluminum-treated rats in a dose-dependent manner. At the highest dose of GbE (200 mg/kg), the immunostain for APP and caspase-3 was returned to normal levels. In summary, this study demonstrates that GbE is effective in improving the ability of spatial learning and memory of aluminum-intoxicated rats. This protection appears to be due to a decreased expression of APP and caspase-3 in rat brain, resulting in a decrease in the production of insoluble fragments of Abeta-amyloid.     

Reduction of Phosphorylated Synapsin I (Ser-553) Leads to Spatial Memory Impairment by Attenuating GABA Release after Microwave Exposure in Wistar Rats

Background

Abnormal release of neurotransmitters after microwave exposure can cause learning and memory deficits. This study investigated the mechanism of this effect by exploring the potential role of phosphorylated synapsin I (p-Syn I).

Methods

Wistar rats, rat hippocampal synaptosomes, and differentiated (neuronal) PC12 cells were exposed to microwave radiation for 5 min at a mean power density of 30 mW/cm². Sham group rats, synaptosomes, and cells were otherwise identically treated and acted as controls for all of the following post-exposure analyses. Spatial learning and memory in rats was assessed using the Morris Water Maze (MWM) navigation task. The protein expression and presynaptic distribution of p-Syn I and neurotransmitter transporters were examined via western blotting and immunoelectron microscopy, respectively. Levels amino acid neurotransmitter release from rat hippocampal synaptosomes and PC12 cells were measured using high performance liquid chromatograph (HPLC) at 6 hours after exposure, with or without synapsin I silencing via shRNA transfection.

Results

In the rat experiments, there was a decrease in spatial memory performance after microwave exposure. The expression of p-Syn I (ser-553) was decreased at 3 days post-exposure and elevated at later time points. Vesicular GABA transporter (VGAT) was significantly elevated after exposure. The GABA release from synaptosomes was attenuated and p-Syn I (ser-553) and VGAT were both enriched in small clear synaptic vesicles, which abnormally assembled in the presynaptic terminal after exposure. In the PC12 cell experiments, the expression of p-Syn I (ser-553) and GABA release were both attenuated at 6 hours after exposure. Both microwave exposure and p-Syn I silencing reduced GABA release and maximal reduction was found for the combination of the two, indicating a synergetic effect.

Conclusion

p-Syn I (ser-553) was found to play a key role in the impaired GABA release and cognitive dysfunction that was induced by microwave exposure.     

负重爬梯与有氧跑台运动对糖尿病大鼠学习记忆能力的影响及其机制探讨

目的：研究负重爬梯与有氧跑台运动对糖尿病大鼠学习记忆能力的改善效果并探索其可能分子机制。方法：40只雄性大鼠,随机分为正常对照组（NC）、糖尿病对照组（DC）、糖尿病负重爬梯组（DL）和糖尿病有氧跑台组（DA）,以单次腹腔注射链脲佐菌素构建糖尿病大鼠模型。DL组在晚上进行负重爬梯训练,10次/组×3组/天,每次间歇2 min,6天/周×6周;DA组在同一时间进行20 m/min的跑台训练,30 min/d。于造模成功和运动干预结束后采用Morris水迷宫检测大鼠的学习记忆能力;第2次水迷宫测试结束后断颈处死大鼠,采用RT-QPCR法检测大鼠海马内脑源性神经营养因子（BDNF）、TRKB、CREB mRNA表达水平。结果：与NC组相比,DC组大鼠海马BDNF、CREB基因表达显著下降,学习记忆能力显著降低。与DC组相比,DL和DA组大鼠海马BDNF、CREB基因表达显著上调,学习能力显著提高;DL大鼠海马TrkB基因显著上调,大鼠空间记忆能力显著改善,而DA组大鼠海马TrkB基因无显著变化,大鼠空间记忆能力无改善,与DA组相比,DL组大鼠海马TRKB、CREB基因显著上调。结论：有氧跑台运动与负重爬梯运动介导BDNF/TrkB/CREB信号通路对糖尿病大鼠的学习能力均有促进作用,而负重爬梯运动对糖尿病大鼠记忆能力的改善优于有氧运动方式。