大鼠慢性脑缺血后海马CA_1区HCN1及p38MAPK的表达

目的探讨慢性脑缺血后大鼠海马HCN1及p38MAPK表达变化及意义。方法双侧颈总动脉永久性结扎(two vessels occlusion,2VO)制备慢性脑缺血模型,40只雄性Wistar大鼠随机分为缺血1 m组和缺血2 m组,每组均设对照组,共4组。应用Morris水迷宫、HE染色、Western blot及免疫荧光双重染色观察各组大鼠认知功能改变、海马CA1区形态学变化、HCN1和p38MAPK定位及表达情况。结果与对照组相比,大鼠缺血1 m时即出现空间学习记忆能力障碍,且缺血2 m组较1 m组更加显著,具有统计学意义(P<0.05);缺血1 m组海马CA1区可见锥体细胞变性,排列松散,个别细胞脱失,伴炎细胞浸润及胶质细胞增生;缺血2 m组海马CA1区可见锥体细胞排列紊乱,细胞脱失明显;HCN1和p38MAPK共同表达于海马CA1区锥体细胞,并且随着缺血时间的延长,海马区p38MAPK表达上调、HCN1表达下调,具有显著性差异(P<0.05)。结论慢性脑缺血导致海马CA1区神经元损伤进而影响认知功能;HCN1和p38MAPK在海马CA1区锥体细胞共同表达;随着缺血时间延长p38MAPK表达上调,HCN1表达下调,推测是慢性脑缺血大鼠认知功能损伤机制之一。     

慢性前脑缺血大鼠学习、记忆功能的研究

目的 研究慢性持续性脑血流量下降对大鼠学习、记忆功能的影响。方法 采用双侧颈总动脉永久结扎方法制备慢性前脑缺血动物模型；利用激光多普勒血流仪检测各组大鼠术后不同时间点（术后24h、7d、15d、30d、60d、90d、120d）额叶皮质、海马枢局部及血流量(rCBF）；采用被动回避性条件反射－－跳台试验检验各组大鼠（时间点同前）学习能力；利用水迷宫方法检验各组大鼠记忆功能。结果 大鼠术后额叶皮质、海马区的cCBF明显下降，以术后24h最明显，主后120d时仍明显 于正常，呈慢性持续性下降的趋势。同时各实验组大鼠学习、记忆能力也明显下降，且有随时间推移而逐渐加重的倾向。结论 慢性持续性脑血流量下降可导致实验大鼠出现进行性认知功能障碍。     

胰岛素对脑缺血后鼠海马CA1区神经元凋亡及记忆影响

目的　观察胰岛素对全脑缺血后海马CA1区神经元凋亡及大鼠学习记忆力改变的影响 ,探讨胰岛素对全脑缺血后海马CA1区神经元产生中枢直接保护作用的机理。方法　利用 4 VO法制作大鼠全脑缺血模型。造成脑缺血 15min后行再灌注 ,于再灌注后即刻经脑室注入 1U胰岛素 ,利用免疫组化及原位标记法分别于全脑缺血后 1、3d观察海马CA1区Bcl 2、Bcl xl蛋白表达及神经元凋亡的情况 ;缺血后 8周 ,利用“Y”型迷宫测试大鼠的学习记忆功能。结果　全脑缺血后 3d ,缺血组大鼠海马CA1区Bcl 2、Bcl xl蛋白的表达呈阴性 ,海马CA1区原位标记阳性细胞计数为 14 3.5± 11.6。治疗组大鼠海马CA1区Bcl 2、Bcl xl蛋白呈阳性表达 ,海马CA1区原位标记阳性细胞计数为 75 .6±6 .7。全脑缺血后 8周 ,治疗组大鼠学习记忆力明显好于缺血组。结论　全脑缺血后脑室内注入胰岛素可促进海马CA1区Bcl 2、Bcl xl蛋白表达 ,减少神经元的凋亡 ,进而减轻脑缺血后大鼠的学习记忆力损害 ,这可能是其对全脑缺血后海马CA1区神经元产生中枢直接保护作用主要机理之一     

慢性脑缺血海马CA1区微血管LRP-1的表达及其对认知功能的影响

目的探讨慢性脑缺血大鼠海马CA1区微血管LRP—1表达与认知功能改变的相关性。方法应用双侧颈动脉结扎的方法制作SD大鼠慢性缺血模型;Morris水迷宫对大鼠的认知功能进行测试;免疫组化技术测定海马CA1区微血管LRP-1,Ⅷ因子相关抗原及GFAP的表达;放免技术对脑脊液Aβ蛋白的浓度进行测定。采用 MIAS图像分析系统对免疫组化结果进行平均光密度测定及微血管计数。结果术后1个月手术组大鼠认知功能已明显下降,寻找平台所需游走的距离较假手术显著延长。术后6个月手术组大鼠海马CA1区微血管LRP-1的表达较假手术组大鼠显著降低;GFAP的表达显著增强;但VIII因子相关抗原的表达及微血管计数两组之间无显著差异。微血管LRP-1表达与水迷宫成绩呈负相关。手术组大鼠脑脊液Aβ蛋白含量较假手术组显著下降。结论慢性缺血过程中,大鼠认知功能下降与海马CA1区微血管LRP-1的表达下降有显著相关性。     

脑缺血后大鼠海马CA1区神经元持续钠电流变化的研究

目的研究脑缺血后大鼠海马CA1区神经元持续钠电流的变化,探讨钠通道阻滞剂对缺血脑组织保护的机理。方法酶消化法急性分离SD大鼠(10~14d)海马CA1区神经元,全细胞膜片钳技术记录脑缺血对持续钠电流的影响。结果缺血3 min时持续钠电流增加到正常时的1.59±0.26倍(P﹤0.05),缺血5 min时增加到正常时的2.92±0.46倍(P﹤0.05)。结论脑缺血时钠通道开放,持续钠电流增加。     

依达拉奉对慢性脑低灌注大鼠脑自由基代谢及海马CA1区HIF-1α表达的影响

目的:观察依达拉奉对慢性脑低灌注大鼠前脑组织SOD、MDA代谢变化及海马CA1区HIF-1α表达的影响,并探讨其意义。方法:实验分假手术组,模型组及依达拉奉组,后两组采用永久性大鼠双侧劲总动脉结扎术(2-vesselocclusion,2VO)制备慢性脑低灌注模型,各组在术后八周后行水迷宫试验后断头,取前脑组织制备成10%脑组织匀浆检测其SOD活性及MDA含量,并采用免疫组化技术观察海马CA1区HIF-1α表达变化。结果:模型组与假手术组相比水迷宫完成时间显著延长(P<0.05),前脑组织SOD活性降低,MDA含量增加(P<0.01),海马CA1区可见HIF-1α少量表达。依达拉奉组较模型组水迷宫结果显著改善(P<0.01),前脑组织SOD活性增加,MDA含量减少(P<0.01),且海马CA1区可见HIF-1α大量表达。结论:慢性脑低灌注可显著损害大鼠空间学习记忆能力,依达拉奉可能通过抑制黄嘌呤氧化酶和次黄嘌呤氧化酶活性,降低羟自由基的浓度,促进HIF-1α表达等多种途径改善血管性认知障。     

缺氧诱导因子-1α在慢性脑缺血大鼠海马中的表达

目的　观察缺氧诱导因子 - 1α在慢性脑缺血大鼠海马中的表达 ,并探讨其表达的意义。方法　采用永久性双侧颈总动脉结扎术 ( 2 VO)制备大鼠慢性脑缺血的动物模型 ,运用 Western印迹和免疫组化检测 HIF- 1α的表达。结果　 Western印迹显示 2 VO1d后 HIF- 1α的表达即上调 ,2周后进一步升高 ,保持这一水平直至第 6周。免疫组化见海马各区均有免疫阳性细胞分布。结论　 HIF- 1α在慢性脑缺血大鼠海马中的表达上调 ,可能参与了慢性脑缺血的代偿机制。     

化学点燃癫痫大鼠在水迷宫中学习记忆能力与海马中bFGF表达的关系

目的 观察印防己毒(picrotoxin，PTX)化学点燃癫痫大鼠在水迷宫中学习记忆训练与大鼠海马中碱性成纤维细胞生长因子(basic fibroblast grouth factor，bFGF)表达变化的关系，为进一步研究癫瘸患者记忆损害及其治疗提供线索。方法 44只雄性SD大鼠随机分为点燃组和对照组，分别用PTX和生理盐水腹腔注射，根据点燃情况点燃组再分为全面发作(A)、频繁发作(B)及部分发作(C)3组和迷宫对照(D)组，后者再分为迷宫训练(E)组和对照组(F)。然后进行水迷宫行为测试评价其学习记忆能力。用免疫组化和原位杂交法测定各组大鼠海马中bFGF表达变化。结果 癫痫大鼠在水迷宫测定中，除B组第1天的成绩较对照组差外，其余各组及B组在第2、3、4、5天中寻找平台的潜伏期时间与对照组相比差异无显著性。点燃各组对平台空间位置记忆的能力较对照组要差，差异有显著性。大鼠海马中，bFGF免疫组化染色阳性细胞在点燃各组和E组表达增高，bFGFmRNA在点燃各组和E组表达增强，而以A、B、C组表达增高最明显。结论 首次用化学点燃模型研究癫瘸大鼠在水迷宫中的学习记忆能力，发现PTX化学点燃癫痫大鼠在水迷宫中学习记忆能力下降，发作频繁者学习记忆受损明显，与发作的严重程度无关。水迷宫训练可使化学点燃癫痫大鼠海马中bFGF表达增高，对记忆损害有保护作用。     

γ-氨基丁酸对慢性脑缺血致血管性痴呆大鼠学习记忆能力的影响

目的观察γ-氨基丁酸（GABA）对慢性脑缺血致血管性痴呆（VD）大鼠学习记忆能力及海马CA1区神经元形态学的影响。方法将SD大鼠随机分为假手术组、模型组、GABA组,采用双侧颈总动脉永久性结扎法建立VD模型。GABA组术后腹腔注射GABA0.5g.kg-1.d-1,连续注射60d;用Morris水迷宫实验检测大鼠空间学习记忆能力;Nissl染色观察大鼠海马CA1区神经元形态学变化。结果 GABA能明显改善VD大鼠学习记忆能力,也能减轻海马CA1区神经元损伤。结论 GABA能改善慢性脑缺血致VD大鼠的学习记忆能力,减轻海马神经元损伤可能是其机制之一。     

Deprivation of endogenous brain-derived neurotrophic factor results in impairment of spatial learning and memory in adult rats

Brain-derived neurotrophic factor (BDNF) is abundantly expressed in the hippocampus and cerebral cortex and is involved in synaptic plasticity and long-term potentiation (LTP). The present study was under taken to investigate whether endogenous BDNF was required for spatial learning and memory in a rat model. Antibodies to BDNF (anti-BDNF, n=7) or control immunoglobulin G (control, n=6) were delivered into the rat brain continuously for 7 days with an osmotic pump. The rats were then subjected to a battery of behavioral tests. The results show that the average escape latencies in the BDNF antibody treated group were dramatically longer than those of the control (F=13.3, p<0.001). The rats treated with control IgG swam for a significantly longer distance in the P quadrant (where the escape plane had been placed) compared with the other three quadrants (p<0.05). In contrast, anti-BDNF-treated rats swam an equivalent distance in all four quadrants. The average percentage of swimming distance in the P quadrant by anti-BDNF-treated rats was much less than that by control IgG treated rats (p<0.001). These results suggest that endogenous BDNF is required for spatial learning and memory in adult rats.     

The effect of steroid sulfatase inhibition on learning and spatial memory

Steroid sulfatase inhibitors can enhance the concentration of the neurosteroid DHEAS in rat brain. Previous studies have demonstrated that the steroid sulfatase inhibitor (p-O-sulfamoyl)-N-tetradecanoyl tyramine (DU-14) could reverse scopolamine induced amnesia in rats in a passive avoidance memory paradigm. The intent of this study was to determine whether chronic pretreatment with DU-14 could reverse scopolamine amnesia and/or enhance spacial memory in the place, probe and cued versions of the Morris water maze (MWM). Rats were divided into four groups and administered IP for 15 days either DU-14 (30.0 mg/Kg) or corn oil (1.0 ml/Kg) vehicle. On training days animals were administered either scopolamine (1.0 mg/Kg) or saline (1.0 ml/Kg). The groups administered DU-14 displayed a significant enhancement in learning and spacial memory in the place version of the MWM, when compared to respective vehicle-scopolamine and vehicle-saline groups. In the probe version, the DU-14-saline group remained in the target quadrant of the maze significantly longer than any of the other groups indicating enhanced retention. In the cued version of the MWM, treatment with DU-14 did not significantly change escape latency suggesting that the steroid sulfatase inhibitor did not alter motivation or locomotion. These results suggest that the chronic administration of steroid sulfatase inhibitors enhance learning and spatial memory in rats.     

Long-term potentiation in the hippocampal CA1 area and dentate gyrus plays different roles in spatial learning

NMDA receptor-dependent long-term potentiation (LTP) at hippocampal synapses has been considered a crucial component of the cellular basis for learning and memory. This form of LTP occurs in excitatory synapses in both the CA1 area and the dentate gyrus in the hippocampus. However, differential roles of LTP in these areas have not yet been identified. To address this issue, we enhanced the degree of LTP by expressing Ca2+-permeable AMPA receptors at either hippocampal CA1 or dentate gyrus synapses using Sindbis viral vectors (SINs) encoding both green fluorescent proteins and unedited GluR2 (GluR2Q) subunits, and examined their effects on rat spatial learning. The viral vectors were locally injected into the 8-week-old-rat brain in vivo bilaterally. The postsynaptic expression of Ca2+-permeable AMPA receptors enhanced the degree of LTP, and induced NMDA receptor-independent LTP in the presence of the NMDA receptor antagonist in SIN-infected regions in both CA1 and dentate gyrus in hippocampal slice preparations. However, the regional expression of Ca2+-permeable AMPA receptors caused opposite behavioural consequences on the Morris water maze task: rats with SIN-infected CA1 pyramidal cells showed shorter escape latency and better probe test performance, whereas those with SIN-infected dentate gyrus granule cells showed impaired performance. Thus, it was demonstrated that CA1 and dentate gyrus synapses play different functional roles in spatial learning despite their similar mechanism for LTP induction.     

Effects of electromagnetic radiation on spatial memory and synapses in rat hippocampal CA1

In this study,we investigated the effects of mobile phone radiation on spatial learning,reference memory,and morphology in related brain regions.After the near-field radiation(0.52-1.08 W/kg) was delivered to 8-week-old Wistar rats 2 hours per day for 1 month,behavioral changes were examined using the Morris water maze.Compared with the sham-irradiated rats,the irradiated rats exhibited impaired performance.Morphological changes were investigated by examining synaptic ultrastructural changes in the hippocampus.Using the physical dissector technique,the number of pyramidal neurons,the synaptic profiles,and the length of postsynaptic densities in the CA1 region were quantified stereologically.The morphological changes included mitochondrial degenerations,fewer synapses,and shorter postsynaptic densities in the radiated rats.These findings indicate that mobile phone radiation can significantly impair spatial learning and reference memory and induce morphological changes in the hippocampal CA1 region.     

Neonatal hippocampal damage in rats: Long-term spatial memory deficits and associations with magnitude of hippocampal damage

This study investigated the effects of neonatal hippocampal ablation on the development of spatial learning and memory abilities in rats. Newborn rats sustained bilateral electrolytic lesions of the hippocampus or were sham-operated on postnatal day 1 (PN1). At PN20–25, PN50–55, or PN90–95, separate groups of rats were tested in a Morris water maze on a visible “cue” condition (visible platform in a fixed location of the maze), a spatial “place” condition (submerged platform in a fixed location), or a no-contingency “random” condition (submerged platform in a random location). Rats were tested for 6 consecutive days, with 12 acquisition trials and 1 retention (probe) trial per day. During acquisition trials, the rat's latency to escape the maze was recorded. During retention trials (last trial for each day, no escape platform available), the total time the rat spent in the probe quadrant was recorded. Data from rats with hippocampal lesions tested as infants (PN20–25) or as adults (PN50–55 and PN90–95) converged across measures to reveal that 1) spatial (place) memory deficits were evident throughout developmental testing, suggesting that the deficits in spatial memory were long-lasting, if not permanent, and 2) behavioral performance measures under the spatial (place) condition were significantly correlated with total volume of hippocampal tissue damage, and with volume of damage to the right and anterior hippocampal regions. These results support the hypothesis that hippocampal integrity is important for the normal development of spatial learning and memory functions, and show that other brain structures do not assume hippocampal-spatial memory functions when the hippocampus is damaged during the neonatal period (even when testing is not begun until adulthood). Thus, neonatal hippocampal damage in rats may serve as a rodent model for assessing treatment strategies (e.g., pharmacological) relevant to human perinatal brain injury and developmental disabilities within the learning and memory realm. Hippocampus 7:403–415, 1997. © 1997 Wiley-Liss, Inc.     

Cardiac arrest with cardiopulmonary resuscitation reduces dendritic spine density in CA1 pyramidal cells and selectively alters acquisition of spatial memory

The hippocampus is highly sensitive to ischemia and is one of the most extensively damaged regions of brain during cardiac arrest. Damage to hippocampus can subsequently lead to learning and memory deficits. The current study used the Morris water maze to characterize spatial learning and memory deficits elicited by 8 min of cardiac arrest with cardiopulmonary resuscitation (CA/CPR) in mice, which is associated with a 25-50% decrease in CA1 neurons. Mice were trained to navigate the water maze prior to CA/CPR or sham surgery (SHAM). They were retested in the water maze on days 7 and 8 postsurgery; both CA/CPR and SHAM groups were able to perform the task at presurgical levels. However, when the hidden platform was moved to a new location, the SHAM mice were able to adapt more quickly to the change and swam a shorter distance in search of the platform than did CA/CPR mice. Thus, CA/CPR did not affect the ability of mice to retain a previously learned platform location, but it did affect their ability to learn a new platform location. This behavioural impairment was correlated with dendritic spine density in the CA1 region of the hippocampus. Data presented here suggest that morphological changes, such as spine density, that occur in neurons that survive CA/CPR may be associated with cognitive impairments.     

Intercellular adhesion molecule-1 expression in the hippocampal CA1 region of hyperlipidemic rats with chronic cerebral ischemia

Chronic cerebral ischemia is a pathological process in many cerebrovascular diseases and it is induced by long-term hyperlipidemia,hypertension and diabetes mellitus.After being fed a high-fat diet for 4 weeks,rats were subjected to permanent occlusion of bilateral common carotid arteries to establish rat models of chronic cerebral ischemia with hyperlipidemia.Intercellular adhesion molecule-1 expression in rat hippocampal CA1 region was determined to better understand the mechanism underlying the effects of hyperlipidemia on chronic cerebral ischemia.Water maze test results showed that the cognitive function of rats with hyperlipidemia or chronic cerebral ischemia,particularly in rats with hyperlipidemia combined with chronic cerebral ischemia,gradually decreased between 1 and 4 months after occlusion of the bilateral common carotid arteries.This correlated with pathological changes in the hippocampal CA1 region as detected by hematoxylin-eosin staining.Immunohistochemical staining showed that intercellular adhesion molecule-1 expression in the hippocampal CA1 region was noticeably increased in rats with hyperlipidemia or chronic cerebral ischemia,in particular in rats with hyperlipidemia combined with chronic cerebral ischemia.These findings suggest that hyperlipidemia aggravates chronic cerebral ischemia-induced neurological damage and cognitive impairment in the rat hippocampal CA1 region,which may be mediated,at least in part,by up-regulated expression of intercellular adhesion molecule-1.     

影响小鼠Morris水迷宫成绩的因素探讨及改进措施

Morris水迷宫自英国心理学家Richard Morris于1981年首次使用以来,已成为一种研究与海马功能直接相关的空间学习记忆机制的标准模式,能较准确地反映动物的空间参考记忆能力[1].Morris水迷宫能为考察实验动物空间认知能力提供较多的评价指标,全面记录其认知加工过程,客观地反映其认知水平.但是,Morris水迷宫的实施过程中还有很多影响其准确性和可靠性的因素存在,如实验动物的选择、实验设计、实验的实施过程等.因此,笔者现就影响小鼠Morris水迷宫成绩的若干因素(Morris水迷宫自身因素及小鼠主观因素等)进行综述,以期为实验工作者们减少误差提供一些帮助.     

丙戊酸钠对慢性酒中毒模型大鼠学习记忆损害的影响

目的探讨慢性酒中毒对大鼠学习记忆的影响及丙戊酸钠(VPA)的干预效应及其可能机制。方法将56只SD大鼠随机分为酒中毒模型组、VPA干预组、VPA对照组和正常对照组。以乙醇浓度梯度递增式的方式灌胃8周制作慢性酒中毒模型,而第5周始酒中毒模型组腹腔注射生理盐水,VPA干预组于第5～8周腹腔注射VPA,VPA对照组灌注等体积的生理盐水4周后第5～8周给予VPA。8周后每组随机选取7只采用Morris水迷宫和Y迷宫检测大鼠的学习记忆功能,其余7只用Westernblot检测海马脑源性神经营养因子(BDNF)蛋白的表达含量。结果与正常对照组相比,酒中毒模型组大鼠水迷宫的逃避潜伏期显著延长(P0.05),空间探索次数显著减少(P0.05);Y迷宫中2d的错误次数显著增加(P0.01);海马BDNF含量下降(P0.05)。与酒中毒模型组相比,VPA干预组大鼠的行为学成绩均得到改善(P0.01),海马BDNF含量显著增加(P0.01),与正常对照组的差异无统计学意义(P0.05)。VPA对照组与正常对照组各项指标的差异均无统计学意义(P0.05)。结论慢性酒中毒可以导致大鼠学习记忆障碍,而VPA对酒精诱导的学习记忆损害有干预作用,海马BDNF表达增加可能是其作用机制之一。