脑缺血与慢性应激对依赖海马的学习记忆的影响

目的 对比脑缺血与慢性应激所致认知损害及海马病变的强弱,为临床改善脑卒中后认知障碍(poststroke cognitive impairment,PSCI)提供参考.方法 40只成年雄性SD大鼠平均分为4组:对照组、应激组、缺血组与缺血加应激组,缺血手术采用改良的选择性大脑中动脉栓塞术;应激处理采用连续3周的慢性不可预见性温和应激;Moms水迷宫实验评价依赖海马的学习记忆功能;免疫组织化学染色及半定量RT-PCR观察海马CA3区脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)的表达变化.结果 应激或缺血均可使大鼠学习功能明显下降,表现为与同时点对照组比较,逃避潜伏期显著延长,二者的综合作用更明显.慢性应激对学习功能的影响强于脑缺血损伤.应激或缺血均减弱记忆功能,但二者的作用差异无统计学意义.与对照相比,缺血显著增加海马CA3区BDNF的表达(27.0±2.5与20.1±2.1),应激降低BDNF的表达(15.2±1.8与20.1±2.1),二者综合作用仍显著降低BDNF的表达(8.2±1.5),差异均具有统计学意义(F=52.87,P＜0.05).结论 缺血与应激均降低大鼠学习记忆功能,应激对认知功能的损害高于缺血,而缺血与应激的综合作用对认知功能损害与抑制BDNF表达作用更明显,提示进行PSCI的综合治疗时,要重视心理社会应激干预和抑郁状态的改善.     

重复经颅磁刺激对抑郁模型大鼠行为学及海马BDNF表达的影响

目的探讨重复经颅磁刺激(repetitive transcranial magnetic stimulation,rTMS)对慢性应激抑郁模型大鼠行为学及海马脑源性神经营养因子(brain derived neurotrophic factor,BDNF)的影响,探讨rTMS抗抑郁作用的可能机制。方法 40只雄性SPF级Sprague-Dawley大鼠经过初次筛选后,随机分为造模组(n=30)和空白对照组(n=8),造模组应用孤养联合慢性不可预见性温和应激(chronic unpredictable mild stress,CUMS)方法建立大鼠抑郁模型,筛选造模成功的大鼠24只随机分为rTMS组、伪刺激组和抑郁对照组,每组8只,抑郁对照组不给予rTMS干预,rTMS组和伪刺激组分别接受10 Hz的rTMS刺激和伪刺激干预3周。分别于造模前、造模后和干预后进行体质量测量、蔗糖水消耗实验和旷场实验评估,在干预后,检测大鼠海马CA3区BDNF阳性染色的细胞数及海马BDNF m RNA的表达水平。结果造模后,rTMS组、伪刺激组和抑郁对照组大鼠的体质量减分率较空白对照组降低(P0.01),体质量增加缓慢(P0.01)。干预后,r TMS组大鼠体质量减分率、蔗糖水消耗量、旷场实验的水平运动评分以及垂直运动评分较伪刺激组和抑郁对照组均增高(均P0.05),与空白对照组差异并无统计学意义(均P0.05)。干预后,rTMS组大鼠海马CA3区BDNF阳性细胞数目较伪刺激组和抑郁对照组增加(P0.01),伪刺激组和抑郁对照组较空白对照组减少(P0.01);r TMS组大鼠海马BDNF m RNA的相对表达量较伪刺激组和抑郁对照组增多(P0.01),伪刺激组和抑郁对照组较空白对照组减少(P0.01)。结论 rTMS干预能够改善CUMS抑郁模型大鼠的抑郁样行为,可能与增加海马BDNF的表达导致海马神经元再生有关。     

文拉法辛对慢性应激抑郁大鼠海马区可塑性相关蛋白mRNA表达的影响

目的 观察文拉法辛对慢性应激抑郁大鼠海马区可塑性相关蛋白mRNA表达的影响.方法 用慢性不可预见应激(CUS)方法建立大鼠抑郁模型,给予2种剂量(5 mg/kg体质量和10 mg/kg体质量)的抗抑郁剂文拉法辛,用反转录-聚合酶链反应检测大鼠海马区脑源性神经营养因子(BDNF)、转录因子环磷腺苷反应元件结合蛋白(CREB)及神经细胞黏附分子(NCAM)mRNA表达的变化.正常对照组、抑郁模型组、抑郁模型后注射生理盐水14 d组及28 d组各10只,抑郁模型后小剂量文拉法辛(5 mg/kg体质量)治疗14 d组及28 d组、抑郁模型后大剂量文拉法辛(10 mg/kg体质量)治疗14 d组及28 d组各11只.结果 抑郁模型大鼠体质量、蔗糖水消耗量及旷场实验结果均明显低于正常对照组,提示抑郁模型大鼠在第28天建立成功.慢性不可预见应激28 d后,抑郁模型大鼠海马区BDNF(0.18±0.09)、CREB(0.10±0.05)及NCAM(0.08±0.04)mRNA表达水平均明显低于正常组[吸光度比值分别为(0.41±0.12)、(0.26±0.05)及(0.24±0.08);P均＜0.05 ].5 mg/kg体质量文拉法辛明显增加海马区3种可塑性相关蛋白mRNA的表达;10 mg/kg文拉法辛轻度降低海马区3种可塑性相关蛋白mRNA的表达.结论 文拉法辛在一定剂量范围内调节海马区的神经可塑性,BDNF、CREB及NCAM在抑郁症的病因及治疗中发挥重要作用.     

不同剂量文拉法辛对抑郁模型大鼠海马区pCREB和BDNF表达的影响

目的探讨不同剂量文拉法辛对慢性应激抑郁大鼠海马区磷酸化转录因子环磷腺苷反应元件结合蛋白(pCREB)和脑源性神经营养因子(BDNF)表达的影响。方法用慢性不可预见应激(CUS)方法建立大鼠抑郁模型,按处理措施不同实验大鼠共分8组各10只,即正常对照组(NC)、抑郁模型组注射生理盐水0 d组(MD0)、14d组(MD1)及28 d组(MD2)、小剂量(5 mg/kg)抗抑郁剂文拉法辛治疗14 d组(LV1)及28 d组(LV2)、大剂量(10mg/kg)文拉法辛治疗14 d组(HV1)及28 d组(HV2)。用免疫组织化学和Western Blot方法检测大鼠海马区pCREB和BDNF表达的情况。结果抑郁模型组(MD0、MD1、MD2)大鼠海马区pCREB和BDNF阳性细胞数目和积分光密度(IOD)均显著低于NC组(P均<0.05),5 mg/kg文拉法辛明显增加大鼠海马区pCREB和BDNF的表达(P<0.05),但10 mg/kg文拉法辛对海马区pCREB和BDNF表达的影响无统计学意义(P>0.05)。结论文拉法辛在5 mg/kg剂量时调节海马区的神经可塑性,pCREB和BDNF可能在抑郁症发生机制中发挥重要的作用。     

慢性应激与氟西汀对大鼠海马结构与杏仁核神经营养因子蛋白与核酸表达的影响

目的观察慢性温和未预知应激抑郁模型及氟西汀对大鼠海马与杏仁核神经元BDNF／Trk与NT-3／TrkC表达的影响。方法将32只SD雄性大鼠随机均分为正常组、慢性应激模型组、氟西汀组与生理盐水组。选用慢性轻度不可预见性应激加孤养造模，分别采用免疫组织化学、定量逆转录聚合酶链反应检测慢性应激与氟西汀处理的大鼠海马与杏仁核BDNF／TrkB蛋白和信使核酸的表达。结果与其相应的对照组相比，两干预组海马海马回区（CA）与齿状核（DG）BDNF表达呈现相反的变化，而杏仁核的表达则相似。慢性应激组与氟西汀组NT-3在海马与齿状核受调节的方向迥异。TrkB与TrkC表达水平与其配体调节方向略有差别。结论慢性温和未预知应激与氟西汀对海马与杏仁核BDNF／Trk与NT-3／TrkC表达的不同调节方向，可能反映慢性应激抑郁模型动物的病理过程与氟西汀治疗效应之间的差异。     

慢性应激抑郁模型大鼠强迫游泳后海马中c-fos的表达

目的 研究慢性应激对强迫游泳大鼠海马神经元c-fos表达的影响。方法 采用特异性抗体的免疫组织化学方法,在大鼠慢性应激抑郁模型基础上,观察急性强迫游泳应激后海马神经元c-fos的表达情况。结果 抑郁模型大鼠接受急性强迫游泳应激后,海马CA3区和齿状回(DG)内FOS蛋白的表达在各主要时点均比对照组降低,图像分析提示,上述两区域的FOS阳性神经元对应切面面积比明显降低(P<0.05),平均目标灰度值显著增加(P<0.05)。结论 慢性应激使大鼠在急性强迫游泳应激后海马CA3区和DG内c-fos的表达降低。     

发育期癫大鼠移植骨髓源性神经干细胞对海马BDNF和bFGF表达的影响

目的将骨髓源性神经干细胞(BMSCs)移植到发育期癫大鼠海马区,观察大鼠海马脑源性神经营养因子(BDNF)和碱性成纤维生长因子(bFGF)表达的变化。方法选择21日龄发育期大鼠,分离大鼠骨髓基质细胞,在特定条件下培养使其诱导分化为神经干细胞(NSC)。建立戊四氮(PTZ)点燃癫大鼠模型,将BMSCs经侧脑室注射移植至癫大鼠海马区;侧脑室注射磷酸缓冲液(PBS)作为对照。分为4组(均n=8):对照组(无癫发作),PTZ致组(癫造模,无治疗),假手术组(癫+PBS侧脑室注射),治疗组(癫+NSC侧脑室注射)。于3、7和14 d处理后用免疫组化法检测大鼠海马区BDNF和bFGF表达。结果致组大鼠海马区(齿状回、CA1区)BDNF和bFGF表达较对照组增加(P0.05),治疗组海马区(齿状回、CA1区)BDNF和bFGF表达较假手术组也有所增加(P0.05)。结论 BMSCs移植可以增加PTZ致大鼠海马BDNF和bFGF表达,从而发挥对癫后脑损伤的保护作用。     

慢性应激抑郁模型大鼠强迫游泳后海马中HsP70的表达

目的研究慢性应激对强迫游泳大鼠海马神经元热休克蛋白70(Hsp70)表达的影响。方法将50 只大鼠随机分为实验组和对照组各25只。实验组大鼠通过21天的应激刺激制作抑郁动物模型,此期间对照组大 鼠正常饲养。此后所有大鼠逐只进行急性强迫应激刺激。采用特异性抗体的免疫组织化学方法,观察2组大鼠在 强迫游泳后2 h、6 h、18 h、24 h和48 h各时点海马神经元Hsp70的表达情况。结果慢性应激抑郁大鼠模型接受 急性强迫游泳应激后,海马CA3区和齿状回(DG)内Hsp70蛋白的表达较对照组强迫游泳后显著降低(P<0．05)。 结论慢性应激使大鼠在急性强迫游泳应激后海马CA3区和DG内Hsp70的表达降低。     

慢性应激抑郁大鼠海马CA1神经元突触可塑性研究

目的 探讨慢性轻度不可预见应激(chronic unpredictable mild stress,CUMS)抑郁模型大鼠海马CA1区神经元的突触可塑性改变.方法 将20只雄性Sprague-Dawley (SD)大鼠随机等分为CUMS组和对照组,前者连续28天每天随机接受不同的应激,对照组同样条件下饲养但不给应激,至第28天进行行为测评后处死,在日立(H7500)透射电镜下测量海马CA1神经元突触界面结构参数.结果 CUMS抑郁大鼠海马CA1神经元突触活性区长度(216.64±20.19 nm)及突触后致密物厚度(42.4±5.23 nm)显著小于对照组(321.58±12.27nm,69.6±4.77 nm),差异有统计学意义(P＜0.05),突触界面曲率及宽度与对照组差异无统计学意义(P＞0.05).结论 慢性应激性抑郁大鼠存在海马CA1区神经元突触可塑性的改变.这提示抑郁症的发病机制可能与海马神经元突触可塑性相关.     

无抽搐电休克治疗大鼠抑郁症的谷氨酸能机制研究

目的 观察抑郁大鼠电休克治疗后海马内谷氨酸含量以及N-甲基-D天门冬氨酸(NMDA)受体的表达,探讨电休克治疗抑郁症的谷氨酸能神经机制.方法 36只SD大鼠随机分为无抽搐电休克组(电休克组)、抑郁模型对照组(抑郁组)、对照组,每组12只.前两组采用孤养加慢性不可预见性应激建立抑郁模型,建模后电休克组在丙泊酚麻醉下行无抽搐电休克治疗,隔天1次共2周.检测各组海马谷氰酸含量和海马CA1区、CA3区NMDA受体2B亚单位(NMDA-NR2B)的表达.结果 ①电休克治疗后电休克组大鼠水平移动格数、垂直竖立次数和糖水消耗量都高于抑郁组(P＜0.01).②电休克组大鼠海马内谷氨酸含量低于抑郁组(P＜0.01),而抑郁组高于正常组(P＜0.01).③电休克组大鼠海马CA1区和CA3区NMDA-NR2B的表达量高于正常组(P＜0.05),而抑郁组低于正常组(P＜0.01).结论 无抽搐电休克治疗可抑制抑郁症模型大鼠海马内谷氨酸含量的升高并使NMDA-NR2B的表达量上调,这可能足其抗抑郁机制之一.     

Expression of brain-derived neurotrophic factor in rat hippocampus following focal cerebral ischemic injury

BACKGROUND： The functional role of brain-derived neurotrophic factor （BDNF） is enhanced following cerebral ischemic injury providing neurons with an important self-protection mechanism in early stage ischemia/hypoxia. OBJECTIVE： To investigate the expression pattern of BDNF in different rat hippocampal regions following focal cerebral ischemic injury. DESIGN, TIME AND SETTING： We performed a comparative and neurobiological study of animals in the Department of Histology and Embryology and the Central Laboratory, Hebei Medical University from March to December 2003. MATERIALS： Forty healthy Sprague Dawley rats were randomly divided into a cerebral ischemia group and a sham operation group, with 20 rats per group. METHODS： In the cerebral ischemia group, we occluded the right middle cerebral artery with a suture, threading it to a depth of 17-19 mm. In the sham operation group, the threading depth was approximately 10mm. MAIN OUTCOME MEASURES： We analyzed the expression of BDNF in different hippocampal regions by immunohistochemical staining of brain sections taken on post-operative days 7, 14, 21 and 30. RESULTS： Sham operation group： We observed a number of a few BDNF-positive cells with light staining in the hippocampal CA1 CA4 regions and dentate gyms. Cerebral ischemia group： compared with the sham operation group, BDNF increased on day 7, significantly increased on day 14, and reached a peak on day 21 （P 〈 0.05）. Furthermore, irnmunologically reactive products were darkly stained, and neurons had long axons. BDNF was particularly highly expressed in the hippocampal CA3 and CA4 regions and dentate gyms. CONCLUSION： Cerebral ischemic injury can damage hippocampal neurons. Neurons can increase their anti-ischemic capacity by increasing BDNF expression in the hippocampal CA3 and CA4 regions and dentate gyms.     

Sex and ovarian steroids modulate brain-derived neurotrophic factor (BDNF) protein levels in rat hippocampus under stressful and non-stressful conditions

Abnormal levels of brain-derived neurotrophic factor (BDNF) are associated with major depression, a disorder with a higher incidence in women than men. Stress affects BDNF levels in various brain regions and thus, a heightened stress response in females could contribute to the development of depression. As well, ovarian hormones directly affect brain levels of BDNF mRNA and protein. Two experiments were performed to investigate the effects of stress and sex and gonadal hormones on BDNF protein levels in CA1, CA3, and dentate gyrus (DG) subregions of the hippocampus. In the first experiment, male and female Sprague-Dawley rats were subjected to one hour of restraint stress or control handling prior to sacrifice. In the second experiment, fifty-one female rats were ovariectomized and separated into stress and control conditions, as described for the first experiment. Stressed and handled groups received a single injection of estrogen (E; 53h prior to stress), estrogen and progesterone (EP; E given at 53h and P given 5h prior to stress), or vehicle (OVX). In both experiments BDNF protein was quantified using an enzyme-linked immunosorbent enzyme assay (ELISA) in micropunches of hippocampus. Gonadally intact females had significantly higher levels of BDNF in CA3, but significantly lower levels in DG, relative to males. In CA3, stress significantly decreased BDNF in both males and females. In DG of ovariectomized female rats, the effects of stress were significantly different following EP vs. vehicle treatment. Thus, stress increased BDNF levels in EP-treated rats but decreased BDNF levels in vehicle-treated rats. Reduced trophic support in DG in the presence of estrogen and progesterone could jeopardize neurogenesis and under certain conditions could be a contributing factor to the hippocampal atrophy associated with stress-induced affective disorders. These results emphasize the need to consider sex, gonadal steroids, and hippocampal subregion when examining the effects of stress on the brain.     

Synergetic effects of quetiapine and venlafaxine in preventing the chronic restraint stress-induced decrease in cell proliferation and BDNF expression in rat hippocampus

Clinical studies show better response rates of patients with depression and schizophrenia to combinations of atypical antipsychotics and antidepressants, compared to responses to either type of drugs alone. Animal studies demonstrate that some antipsychotics and antidepressants increase neurogenesis and BDNF expression in the hippocampus, which is reduced in volume in patients with depression or schizophrenia. We hypothesized that the better therapeutic effects of combined treatment seen in schizophrenia and depression patients are related to the additive or synergistic effects of combined treatment on hippocampal neurogenesis and BDNF expression. To test this hypothesis, we investigated the effects of chronic administration of quetiapine, venlafaxine, and their combination, on hippocampal cell proliferation and BDNF expression in rats, when subjected to chronic restraint stress (CRS) during the last 2 weeks of a 3-week drug administration period. We found (1) CRS decreased hippocampal cell proliferation and BDNF expression; (2) chronic administration of quetiapine or venlafaxine dose-dependently prevented these decreases in hippocampal cell proliferation and BDNF expression caused by CRS (6 h/day for 14 days); (3) the combination of lower doses of quetiapine (5 mg/kg) and venlafaxine (2.5 mg/kg) increased hippocampal cell proliferation and prevented BDNF decrease in stressed rats, whereas each of the drugs exerted mild or no effects; (4) individual higher doses of quetiapine (10 mg/kg) or venlafaxine (5 mg/kg) exerted effects comparable to those produced by their combination. These results support our hypothesis and can lead to future studies to develop new therapeutic approaches for treatment-resistant depression and the negative symptoms of schizophrenia.     

Long‐term lithium treatment increases intracellular and extracellular brain‐derived neurotrophic factor (BDNF) in cortical and hippocampal neurons at subtherapeutic concentrations

Objectives

The putative neuroprotective effects of lithium treatment rely on the fact that it modulates several homeostatic mechanisms involved in the neurotrophic response, autophagy, oxidative stress, inflammation, and mitochondrial function. Lithium is a well‐established therapeutic option for the acute and long‐term management of bipolar disorder and major depression. The aim of this study was to evaluate the effects of subtherapeutic and therapeutic concentrations of chronic lithium treatment on brain‐derived neurotrophic factor (BDNF) synthesis and secretion.

Methods

Primary cultures of cortical and hippocampal neurons were treated with different subtherapeutic (0.02 and 0.2 mM) and therapeutic (2 mM) concentrations of chronic lithium treatment in cortical and hippocampal cell culture.

Results

Lithium treatment increased the intracellular protein expression of cortical neurons (10% at 0.02 mM) and hippocampal neurons (28% and 14% at 0.02 mM and 0.2 mM, respectively). Extracellular BDNF of cortical neurons increased 30% and 428% at 0.02 and 0.2 mM, respectively and in hippocampal neurons increased 44% at 0.02 mM.

Conclusion

The present study indicates that chronic, low‐dose lithium treatment up‐regulates BDNF production in primary neuronal cell culture.     

Phenytoin reverses the chronic stress-induced impairment of memory consolidation for water maze training and depression of LTP in rat hippocampal CA1 region, but does not affect motor activity

Previous studies have shown that phenytoin can protect hippocampal structure from damage by chronic stress, while whether it can reverse the hippocampal malfunction induced by chronic stress is unknown. We investigated the effects of phenytoin on motor activity of stressed rats and on the long-term memory of water maze spatial training, which is known to depend on hippocampal function. We also explored whether phenytoin could protect long-term potentiation (LTP) in hippocampal CA1 region from depression of chronic stressed rats. Isolated hippocampal slices of rats were used to observe the changes of LTP in hippocampal CA1 field with electrophysiological technique. The results showed that the motor activity of chronic forced-swimming rats was markedly higher than that of control rats, and phenytoin could not affect this change. The performance of water maze spatial training indicated that chronic stress damages long-term memory but not short-term memory, and phenytoin could reverse this long-term memory deficit. The increases of LTP after HFS in control and stress-phenytoin groups were significantly greater than those in stress-saline group (P < 0.05). There were no significant differences between control group and stress-phenytoin group (P > 0.05) and between control and control-phenytoin groups (P > 0.05). These findings provided the first evidence with behavioral and electrophysiological technique that phenytoin could reverse the hippocampal-dependent memory deficit and depression of LTP induced by chronic stress, which may be helpful for exploring the pathogenesis and improving the therapy of depression.     

Post-stress changes in BDNF and Bcl-2 immunoreactivities in hippocampal neurons: effect of chronic administration of olanzapine

In the present study, we used a repeated restraint stress animal model to observe the changes in the expression of brain-derived neurotrophic factor (BDNF) and B cell lymphoma protein-2 (Bcl-2) in hippocampal neurons of rats, monitored the time course of the expression over 3 weeks post-stress period, and examined the effects of the chronic administration of olanzapine on the time course. Olanzapine is an atypical antipsychotic drug that has been shown to be neuroprotective in previous in vitro studies. We found: (1) the repeated restraint stress decreases the levels of expression of BDNF and Bcl-2 in hippocampal neurons; (2) the stress-induced decreases spontaneously recover to their pre-stress levels in 3 weeks after the last stress exposure; (3) administration of olanzapine for 1 week returns the expression of Bcl-2 to its pre-stress level, and the administration for 3 weeks causes an excessive expression of BDNF in hippocampal neurons. In the context of the lower levels of BDNF and Bcl-2, and structural brain abnormalities observed in patients with schizophrenia, our findings suggest that BDNF and Bcl-2 may be involved in the pathophysiology of schizophrenia and in the therapeutic action of atypical antipsychotic drugs.     

Regulation of brain-derived neurotrophic factor (BDNF) in the chronic unpredictable stress rat model and the effects of chronic antidepressant treatment

Chronic unpredictable stress (CUS) is a widely used animal model of depression. The present study was undertaken to investigate behavioral, physiological and molecular effects of CUS and/or chronic antidepressant treatment (venlafaxine or imipramine) in the same set of animals. Anhedonia, a core symptom of depression, was assessed by measuring consumption of a palatable solution. Exposure to CUS reduced intake of a palatable solution and this effect was prevented by chronic antidepressant treatment. Moreover, chronic antidepressant treatment decreased depressive-like behavior in a modified forced swim test in stressed rats. Present evidence suggests a role for brain-derived neurotrophic factor (BDNF) in depression. BDNF mRNA levels in the ventral and dorsal hippocampus were assessed by in situ hybridization. Exposure to CUS was not correlated with a decrease but rather with an increase in BDNF mRNA expression in both the dentate gyrus of the dorsal hippocampus and the CA3 region of the ventral hippocampus indicating that there is no simple link between depression-like behaviors per se and brain BDNF levels in rats. However, a significant increase in BDNF mRNA levels in the dentate gyrus of the dorsal hippocampus correlated with chronic antidepressant treatment emphasizing a role for BDNF in the mechanisms underlying antidepressant activity.     

Overexpression of brain-derived neurotrophic factor in the hippocampus protects against post-stroke depression

Post-stroke depression is associated with reduced expression of brain-derived neurotrophic factor(BDNF). In this study, we evaluated whether BDNF overexpression affects depression-like behavior in a rat model of post-stroke depression. The middle cerebral artery was occluded to produce a model of focal cerebral ischemia. These rats were then subjected to isolation-housing combined with chronic unpredictable mild stress to generate a model of post-stroke depression. A BDNF gene lentiviral vector was injected into the hippocampus. At 7 days after injection, western blot assay and real-time quantitative PCR revealed that BDNF expression in the hippocampus was increased in depressive rats injected with BDNF lentivirus compared with depressive rats injected with control vector. Furthermore, sucrose solution consumption was higher, and horizontal and vertical movement scores were increased in the open field test in these rats as well. These findings suggest that BDNF overexpression in the hippocampus of post-stroke depressive rats alleviates depression-like behaviors.