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。     

Acute administration of estrogen and progesterone impairs the acquisition of the spatial morris water maze in ovariectomized rats

Although several markers of synaptic efficacy are enhanced during proestrus, spatial water maze performance is impaired. Because levels of both estrogen and progesterone are elevated in proestrus, the nature of their individual and combined effects on spatial learning was examined. Long-Evans hooded rats were ovariectomized postpubertally and pretrained on a water maze with a visible platform (nonspatial). Following pretraining, rats were administered estrogen (5 microg sc) or oil 48 and 24 h prior to testing and progesterone (500 microg sc) or oil 4 h prior to testing. Rats were tested on a water maze in a different room with a submerged platform (spatial) for 16 trials with random start location in a single testing day. Latency and path length to the target platform were significantly greater in estrogen plus progesterone-treated animals than in controls. Neither estrogen nor progesterone alone significantly impaired performance relative to controls on either measure. Swim speed was not significantly affected by any of the hormone treatments. Performance on a nonspatial cue task was not significantly altered by ovarian steroids. Thus, the combination of estrogen and progesterone produces deficits in the acquisition of the Morris water maze that may be specific to spatial reference memory. These deficits could be due to hormonal influences on extrahippocampal structures or to detrimental effects on behavior resulting from the increased synaptic activity intrinsic to the hippocampus proper.     

大鼠血管性痴呆模型海马组织中线粒体的变化

目的:观察血管性痴呆模型(Vascular dementia,VD)大鼠海马组织内线粒体超微结构、线粒体膜电位与空间学习记忆能力的变化。方法:健康成年雄性Wistar大鼠30只,随机分为假手术组(SHAM)和血管性痴呆(VD)组,每组15只。VD组行双侧颈总动脉结扎手术制备血管性痴呆动物模型,SHAM组手术步骤同VD组,但不结扎颈总动脉。于术后第29天起行Morris水迷宫测试大鼠空间学习记忆功能,第1-5天为定位航行试验,评估大鼠空间学习能力,第6天进行空间探索试验,评估大鼠空间记忆功能。采用透射电镜技术、流式细胞学技术分别检测大鼠海马组织线粒体形态和功能变化。结果:与SHAM组相比,血管性痴呆模型组大鼠Morris水迷宫试验中逃避潜伏期明显延长(P0.01),在目标象限中停留时间显著缩短(P0.01),空间学习记忆能力受损,血管性痴呆模型组大鼠海马组织线粒体超微结构有明显损伤,线粒体膜电位明显下降(P0.01)。结论:线粒体损伤是血管性痴呆空间学习记忆功能障碍的重要机制之一。     

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。     

反复饥饿对大鼠空间学习及海马神经元骨架蛋白磷酸化的影响

为了进一步研究饥饿处理对大鼠空间学习、记忆的影响,通过饥饿2 d、恢复喂食3 d的方法,连续60 d,用Morris水迷宫检测大鼠的空间学习能力.免疫印迹检测神经元骨架蛋白—tau蛋白和神经细丝(Neurofilament,NF)磷酸化水平与分布变化,以及骨架蛋白磷酸化调节的关键酯酶磷酸酯酶PP-2A催化亚单位蛋白水平与分布.反复饥饿的大鼠空间学习能力明显差于对照组(P0.05),tau蛋白在Ser199/202位点和Ser396/404位点发生了过度磷酸化(P0.05),NF磷酸化水平无明显改变,PP-2A的催化亚单位蛋白水平下调(P0.05).反复饥饿可以引起大鼠出现空间学习记忆障碍,下调PP-2A催化亚单位蛋白水平,PP-2A活性抑制及tau蛋白发生过度磷酸化.     

β- 淀粉样多肽低分子量寡聚体对大鼠学习记忆功能的影响

目的:探究Aβ低分子量寡聚体对大鼠学习记忆功能的影响;方法:双侧海马内一次性注射Aβ低分子量寡聚体,15天后开始进行行为测试,测试方法采用跳台实验法、穿梭实验法和Morris水迷宫法;结果:跳台实验结果显示,与对照组比较,Aβ组跳台潜伏期短,错误次数多,差异有统计学意义(P<0.05);穿梭实验结果显示,与对照组比较,Aβ组由明箱进入暗箱的潜伏期短,错误次数多,差异有统计学意义(P<0.05);水迷宫实验结果显示,与对照组比较,Aβ组潜伏期长,跨越原平台次数少,差异有统计学意义(P<0.01);结论:Aβ组大鼠学习记忆能力和空间分辨能力降低,Aβ低分子量寡聚体在大鼠体内表现出较强的毒性作用。     

Protective effects of methanol extract of Acori graminei rhizoma and Uncariae Ramulus et Uncus on ischemia-induced neuronal death and cognitive impairments in the rat

Acori graminei rhizoma (AGR) and Uncariae Ramulus et Uncus (URE) have been widely used as herbal medicine against ischemia. In order to investigate whether AGR and URE influenced cerebral ischemia-induced neuronal and cognitive impairments, we examined the effect of AGR and URE on ischemia-induced cell death in the striatum, cortex and hippocampus, and on the impaired learning and memory in the Morris water maze and radial eight-arm maze in rats. After middle cerebral artery occlusion (MCAO) for 2 h, rats were administered saline, AGR or URE (100 mg/kg, p.o.) daily for three weeks, followed by their training to the tasks. In the water maze test, the animals were trained to find a platform in a fixed position during 6 days and then received a 60-s probe trial in which the platform was removed from the pool on the 7th day. In the radial eight-arm maze, animals were tested six times per week for 1 week. Rats with ischemic insults showed impaired learning and memory on the tasks. Pretreatment with AGR and URE produced a significant improvement in escape latency to find the platform in the Morris water maze and in the number of choice errors in the radial arm maze test. Consistent with behavioral data, pretreatments with AGR and URE significantly reduced ischemia-induced cell death in the hippocampal CA1 area. These results demonstrated that AGR and URE have a protective effect against ischemia-induced neuronal loss and learning and memory damage. Our studies suggest that AGR and URE may be useful in the treatment of vascular dementia.     

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.     

Effects of the neurogenesis stimulator Ro 25-6981 upon formation of spatial skill in adult rats depend on the term of its administration and the animals' ability to learn

Effect of administration of selective N-methyl-D-aspartate (NMDA) receptor antagonist Ro 25-6981 on learning and memory in a dose which is known to stimulate neoneurogenesis was assessed in adult rats with different abilities to formation of spatial skills in different time periods after the antagonist injection. Wistar male rats were trained to find hidden platform in the Morris water maze for 5 consecutive days. Rats' learning ability for spatial skill formation was evaluated depending on platform speed achievements. In re-training sessions (cues and platform location changed), it was found that all rats received Ro 25-6981 13 days before the re-training demonstrated impaired spatial memory. At the same time the inhibitor injected 29 days before re-training selectively facilitated the formation of spatial skill in animals with initially low learning abilities.     

小鼠动物实验方法系列专题(一)——Morris水迷宫实验在小鼠表型分析中的应用

本文以C57和129Sv小鼠为例介绍了Morris水迷宫实验的基本原理和实验步骤。该实验是研究鼠类空间学习记忆功能的重要实验:通过连续多日训练鼠类以水池壁的标记物进行定位导航游泳寻找水中隐藏平台的方法检测小鼠的空间学习能力;接着撤除平台,分析小鼠在水迷宫里搜索原隐藏平台的行为来检测小鼠的空间记忆功能。结果发现,两种小鼠均可成功完成实验,C57综合表现优于129Sv小鼠。Morris水迷宫是对小鼠空间学习和记忆功能研究的重要工具。     

A link between maze learning and hippocampal expression of neuroleukin and its receptor gp78

Neuroleukin (NLK) is a multifunctional protein involved in neuronal growth and survival, cell motility and differentiation, and glucose metabolism. We report herein that hippocampal expression of NLK and its receptor gp78 is associated with maze learning in rats. First, mRNA levels of NLK and gp78 were significantly increased in hippocampi of male Fischer-344 rats following training in the Stone T-maze and the Morris water maze. Second, a parallel increase was found in hippocampal NLK and gp78 proteins after maze learning. Third, NLK and gp78 mRNA and protein expression in hippocampus was reduced in a group of aged rats that showed more errors during the acquisition of the Stone maze task as compared with young rats. Finally, application of recombinant NLK to hippocampal neurons significantly enhanced glutamate-induced ion currents, functional molecular changes that have been correlated with learning in vivo. Taken together, our results identify a novel association of hippocampal expression of NLK and its receptor gp78 with rat maze learning. Interaction of NLK with gp78 and subsequent signaling may strengthen synaptic mechanisms underlying learning and memory formation.     

慢性复合应激增强大鼠空间学习和记忆能力

本文观察了慢性复合应激对大鼠学习与记忆功能的影响。实验采用成年 Wistar 大鼠, 将其随机分成应激组和对照组。采用垂直旋转、睡眠剥夺、噪音刺激和夜间光照4 种应激原, 无规律地交替刺激动物 6 周, 每天6 h, 制作慢性复合应激动物模型。采用 Morris 水迷宫和 Y- 迷宫测试大鼠学习与记忆成绩,并用 Cresyl violet 染色法对大鼠海马结构进行神经细胞计数。结果显示,应激组动物慢性复合应激后, 在 Morris 水迷宫内寻找隐蔽平台所需的时间(潜伏期)比对照组的明显地短(P<0.05), 表明应激鼠的空间记忆能力明显强于对照鼠;在 Y- 迷宫内寻找安全区的正确率比对照组的明显地高(P<0.05), 表明应激鼠的明暗分辨学习能力明显强于对照鼠; 应激鼠慢性复合应激后, 其海马结构齿状回、CA3 和CA1 区神经细胞密度极明显地高于对照鼠(P<0.001)。这些结果提示, 慢性复合应激可增强大鼠空间记忆能力和明暗分辨学习能力。本文并对慢性复合应激模式增强大鼠学习和记忆能力的可能原因进行了讨论。     

Spatial working memory and hippocampal size across pregnancy in rats

The present experiments investigated the effects of pregnancy on performance in the Morris water maze and on hippocampal volume. In the first study, pregnant rats (in between the first and second trimester) outperformed nonpregnant rats on the Morris water maze on 1 day of testing. In the second study, rats were tested in a working memory variation of the maze in which the spatial location of the platform varied. Pregnant females traveled shorter distances than nonpregnant females during the first two trimesters, but performed worse than nonpregnant females during the third trimester. Latency measures showed a similar profile. Group differences in performance were not related to changes in swim speed. However, changes in performance in pregnant females may be related to estrogen, progesterone, and/or corticosterone levels during pregnancy, with low levels of estradiol and high levels of progesterone being associated with better performance. There were no significant differences between pregnant and nonpregnant animals on any of the brain measures, although pregnant animals tended to have a smaller hippocampus than nonpregnant animals. These results indicate that pregnancy can affect performance, possibly related to the hormonal changes that accompany pregnancy.     

The effect of a caudal hippocampus lesion on learning in a Morris water maze in Bank Voles (Clethrionomys glareolus)

The involvement of the caudal hippocampus in spatial learning is presently uncertain, compared to the well established role of the dorsal region. Therefore voles (Clethrionomys glareolus) with large (about 1/3 of the whole hippocampus) caudal cytotoxic lesions were tested in the Morris water maze. A version of the test intended to measure long term spatial memory was used. The lesion inhibited the learning process, as well as reducing the accuracy of platform location memory at early stages of training. The data obtained indicate the involvement of this area in control of spatial learning in rodents.     

Non-steroidal anti-inflammatory agents, tolmetin and sulindac attenuate quinolinic acid (QA)-induced oxidative stress in primary hippocampal neurons and reduce QA-induced spatial reference memory deficits in male Wistar rats

Accumulating evidence suggests that anti-inflammatory agents and antioxidants have neuroprotective properties and may be beneficial in the treatment of neurodegenerative disorders. In the present study, the possible neuroprotective properties of tolmetin and sulindac were investigated using quinolinic acid (QA)-induced neurotoxicity as well as behavioral studies. QA, a metabolite of the tryptophan-kynurenine pathway, significantly induces lipid peroxidation, superoxide anion generation and decreases cell viability in primary hippocampal neurons established from one day old rat pups. However, co-incubation of the neurons with tolmetin or sulindac markedly reduces oxidative stress and enhances cell viability. Animals were trained in a Morris water maze for four consecutive days and thereafter received 0.6 micromol of QA intrahippocampally. The animals were divided into groups and were treated with either tolmetin or sulindac (5 mg/kg twice a day for five days). During test trials, the time taken for each rat to find the submerged platform was recorded over a period of two weeks. Animals were thereafter sacrificed and the hippocampi analyzed for protein carbonyl and glutathione content. The results show that both sulindac and tolmetin reduce the QA-induced spatial memory deficit and sulindac treated animals respond better in the water maze compared to the tolmetin treated animals. Both agents also reduce protein oxidation in rat hippocampus and attenuate the decrease in hippocampal glutathione content induced by QA. This study indicates that the antioxidant properties of tolmetin and sulindac may be beneficial in the treatment of neurodegenerative disorders such as Alzheimer's disease.     

染料木素对卵巢切除大鼠学习记忆能力的影响

目的：探讨染料木素对卵巢切除大鼠学习记忆能力的影响及作用机制。方法：将40只SD雌性大鼠随机分为用假手术组、去卵巢对照组、染料木素高剂量、低剂量组、17β-雌二醇组,切除卵巢建立学习和记忆能力受损的模型。灌胃给药6周后Morris水迷宫测定各组大鼠学习记忆能力,免疫组化法观察大鼠海马微管相关蛋白（tau蛋白）阳性表达情况,测定大鼠脑组织中乙酰胆碱酯酶（AchE）、乙酰胆碱转移酶（ChaT）、超氧化物歧化酶（SOD）的活性及丙二醛（MDA）的含量,观察海马组织超微结构变化。结果：大鼠切除卵巢后Morris水迷宫测定的学习记忆能力显著下降,微管相关蛋白（tau蛋白）异常磷酸化阳性表达率增高,前脑皮质中超氧化物歧化酶（SOD）、乙酰胆碱转移酶（ChaT）活性降低,丙二醛（MDA）含量、乙酰胆碱酯酶（AchE）活性增高。低剂量的染料木素可以发挥类雌激素样作用,改善去卵巢大鼠的以上症状。结论：染料木素对卵巢切除导致的学习和记忆能力下降有改善作用,低剂量效果显著,其可能的机制是：抑制了脑内AchE的活性,使乙酰胆碱的降解减少;增强脑组织抗氧化能力;稳定微管相关蛋白（tau蛋白）,降低tau蛋白异常磷酸化水平。     

电休克对大鼠空间记忆及海马p-ERK活性的影响

目的:观察电休克对大鼠空间记忆和海马磷酸化细胞外调节蛋白激酶(p-ERK)活性的影响。方法:大鼠随机分为电休克组和伪电休克组,每组12只。电休克组每天给予电痉挛刺激,伪电休克组每天给予假电痉挛刺激,共10天;第11天用水迷宫检测各组大鼠的空间学习记忆,然后每组大鼠再随机分为两组,每组6只。一组于学习后1小时处死取海马用Western blot法检测p-ERK活性,另一组于48小时后行水迷宫空间位置探寻实验检测大鼠的存储记忆。结果:电休克组的潜伏期显著长于伪电休克组(P0.01)。电休克组在隐匿平台周围区域/相反区域的搜寻时间无显著性差异(P0.05);伪电休克组在隐匿平台周围区域/相反区域的搜寻时间有显著性差异(P0.05)。电休克组海马p-ERK活性较伪电休克组显著下降(P0.01)。结论:电休克可导致大鼠显著空间记忆障碍,海马p-ERK活性的降低可能是其机制之一。     

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。