帕罗西汀对皮质酮抑制成年大鼠海马细胞增殖的调制作用(英文)

目的慢性糖皮质激素治疗可能导致认知和情感变化,这或许是由于糖皮质激素对海马神经发生及细胞增殖的抑制作用造成。帕罗西汀是一种选择性血清素重摄取抑制剂,临床常用作减轻抑郁症状,近几年来发现它能促进海马神经发生。本研究探讨帕罗西汀与慢性糖皮质激素的相互作用。方法成年大鼠被分成四组,分别给予芝麻油、皮质酮、帕罗西汀或皮质酮和帕罗西汀十四天。溴脱氧尿嘧啶核苷(5-bromo-2-deoxyuridine,BrdU)免疫组化法被用于定量齿状回的细胞增殖。结果皮质酮抑制了海马的细胞增殖,帕罗西汀增加了海马的细胞增殖。同时给药组还显示帕罗西汀能逆转皮质酮的抑制作用。结论本研究结果对防止海马在类固醇治疗以后的损害或许有临床意义。     

行为学训练对海马损伤梗死大鼠齿状回区BrdU和Nestin表达的影响

目的 探讨行为学训练对海马损伤梗死大鼠齿状回区神经干细胞增殖的影响。方法 采用光化学法制成单侧海马损伤梗死模型大鼠72只,随机分为训练组（n=36）和自由活动组（n=36）,每个组设1、7、14、21、28及35d 6个亚组。另设正常对照组36只,与模型组对应分为1、7、14、21、28及35d 6个亚组。训练组大鼠于造模1d后给予水迷宫训练,自由活动组大鼠自由活动,不予水迷宫训练。免疫荧光双标记法观察各不同时间点大鼠海马齿状回区溴脱氧尿嘧啶核苷（Bromodeoxyuridine,BrdU）与巢蛋白（Nestin）的双标记表达情况。结果 正常对照组大鼠海马齿状回区有少量BrdU/Nestin双标记阳性细胞,训练组及自由活动组大鼠在7、14、21及28d海马损伤梗死侧齿状回区BrdU/Nestin双标记阳性细胞数量均有显著增多（P <0.01）;训练组大鼠7、14、21、28d时海马损伤梗死侧齿状回区的BrdU/Nestin双标记阳性细胞数量显著高于自由活动组（P <0.01）;至35d时,训练组及自由活动组大鼠海马损伤梗死侧齿状回区BrdU/Nestin双标记阳性细胞数量与正常对照组无明显差异（P >0.05）。结论 行为学训练能显著增强海马损伤梗死大鼠齿状回区神经干细胞的增殖,促进神经功能恢复。     

皮质酮对大鼠原代海马神经细胞的毒性作用

本文探讨了皮质酮（corticosterone，CORT）对大鼠原代海马神经细胞的毒性作用及作用机制。实验结果显示，CORT加入无血清DMEM培养基可剂量依赖地损伤原代培养海马神经细胞，LD50为3．2×10－6mol／L，而原代培养的皮层神经细胞只被高浓度皮质酮（10－5mol／L和10－4mol／L）所损伤，其LD50为8.5×10－5mol／L，比前者大近20倍。原代培养的海马神经细胞补充高浓度的葡萄糖或NMDA一受体拮抗剂MK－801可显著地拮抗CORT对海马神经细胞的毒性作用。同时，CORT处理的海马神经细胞胞内ATP水平明显降低，而补充高浓度葡萄糖（25mmol／L）可逆转CORT诱导的ATP耗竭。以上结果提示，CORT可选择地损伤海马神经细胞，这一损伤作用与葡萄糖浓度相关。实验结果进一步提示，CORT对海马神经细胞的毒性作用可能与其导致的能量水平低下和兴奋性氨基酸的堆积有关．     

有氧训练对阿尔茨海默病模型大鼠海马齿状回神经发生的影响

目的：观察有氧训练对β淀粉样蛋白25-35（Aβ25-35）诱导的阿尔茨海默病（AD）大鼠齿状回（DG）神经发生的影响。方法：SD大鼠48只,随机分为假手术组（侧脑室注射生理盐水）,有氧训练组（侧脑室注射Aβ25-35＋4周有氧训练）和实验组（侧脑室注射Aβ25-35）。3组大鼠行Morris水迷宫行为学检测,免疫组织化学方法检测海马DGBrdU阳性细胞数,以确定有氧训练对细胞存活的影响;微管相关蛋白免疫组化染色观察新生神经元的突起生长。结果：①与假手术组比,实验组逃避潜伏期显著延长（P〈0.05）;有氧训练组与实验组比,逃避潜伏期明显缩短（P〈0.05）;有氧训练组逃避潜伏期与假手术组比,差异无统计学意义。②与假手术组比,实验组DGBrdU阳性细胞数显著减少（P〈0.05）。③与假手术组比,实验组DG新生神经元突起的数量明显减少（P〈0.05）。④与实验组比,有氧训练可改善DGBrdU阳性细胞的显著减少（P〈0.05）、保护神经元突起的生长（P〈0.05）。结论：Aβ25-35能诱导AD大鼠模型的建立,损害新生神经元突起生长和新生神经元的存活;有氧训练可改善Aβ25-35损害的大鼠新生神经元突起生长和新生神经元的存活。     

电针对实验性癫痫大鼠海马神经元发生的影响

目的研究电针对实验性癫痫(EP)大鼠海马神经元发生的影响,探讨针刺抗癫痫的机制,为临床实践服务。方法以锂-匹罗卡品制备癫痫模型,电针督脉穴位“大椎”与“百会”,采用疏密波,频率为80Hz,电流强度50mA,时间20min。在6d,13d,27d三个时间点分别腹腔注射2次BrdU,每次间隔2h。所有动物均在最后一次注射BrdU后的24h经左心室灌注处死。取脑后,将脑组织入4%多聚甲醛后固定过夜,再入20%蔗糖4℃冰箱沉底。选择海马部位应用恒冷冰冻切片机冠状位连续切片,脑片漂片厚30μm,行免疫细胞化学染色。结果从13d开始,与未经电针处理的EP鼠比较,经电针处理后的EP鼠海马BrdU阳性细胞数明显减少,且差别有显著性意义(P<0.05)。另外,两组间的反复自发性痫性发作(SRSS)次数亦有显著性差异(P<0.05),经电针处理的EP鼠SRSS次数减少。结论电针可减少SRSS次数并抑制神经元的发生。推测电针的抑痫作用是通过抑制SE后的SRSS而减少神经元的发生。     

皮质酮对体外培养的大鼠海马神经元膜电位的影响

为探讨应激激素－皮质酮以违法乱纪 马神经细胞膜电位的影响,采用膜片钳全细胞记录的方法,测量了原代培养的大鼠马神经细胞膜的静脉电位。结果发现,在皮质酮的作用下,海马神经静息电位幅值明显降低,细胞膜呈去极化。     

皮质酮对体外培养的大鼠海马神经元膜电位的影响

为探讨应激激素--皮质酮对海马神经细胞膜电位的影响,采用膜片钳全细胞记录的方法,测量了原代培养的大鼠海马神经细胞膜的静息电位.结果发现,在皮质酮的作用下,海马神经细胞膜静息电位幅值明显降低,细胞膜呈去极化.推测,皮质酮可能通过抑制海马细胞的能量代谢,使细胞能量匮乏,导致膜去极化.     

慢性应激对大鼠海马CA3区锥体细胞顶树突及血清皮质酮浓度的影响

目的探讨慢性应激对大鼠海马CA3区锥体细胞结构和血清皮质酮浓度的影响。方法将20只雄性Sprague-Dawley大鼠按体质量随机分为应激组和对照组,每组10只。采用高尔基染色法及酶联免疫分析方法,观察慢性强迫游泳应激对大鼠海马CA3区锥体细胞顶树突和血清皮质酮浓度的影响。结果应激组大鼠海马CA3区锥体细胞顶树突的总长度[(112±10)μm]短于对照组[(168±34)μm],差异有统计学意义(P<0.01);一级树突直径[(9.0±1.1)μm]大于对照组[(5.7±0.9)μm],差异有统计学意义(P<0.01);血清皮质酮浓度[(13±14)μg/L]低于对照组[(30±16)μg/L],差异有统计学意义(P<0.05)。结论慢性强迫游泳可引起大鼠海马CA3区锥体细胞顶树突及血清皮质酮浓度的改变。     

EGF、bFGF、BDNF对大鼠海马神经干细胞增殖和分化的作用

目的：探讨EGF、bFGF、BDNF对大鼠海马神经干细胞（neural stem cells,NSCs)增殖和分化的作用。方法：建立大鼠海马NSCs原代和克隆培养模型，将EGF、bFGF单独或联合加入培养基中，应用相差显微镜及Nestin、GFAP、NSE免疫组织化学方法观察其对NSCs克隆形成及分化的影响，取EGF、bFGF联合作用传3代的NSCs进行贴壁培养，同时加入BDNF，观察其对NSCs定向分化的影响。结果：EGF促进海马NSCs增殖，但选移和分化少见；bFGF作用下NSCs迁移和分化明显；EGF、bFGF联合作用可形成大的NSCs克隆；EGF、bFGF、BDNF共同作用下可见典型的神经元样细胞，NSE染色阳性。结论：EGF促进大鼠海马NSCs的增殖，bFGF则主要促进其迁移和分化，BDNF可促进EGF、bFGF联合作用的NSCs定向分化为神经元。     

卡马西平对匹罗卡品诱导成年癫癎大鼠海马齿状回神经发生影响的研究

目的研究卡马西平对成年癫癎大鼠海马齿状回神经发生的影响。方法采用氯化锂和匹罗卡品联合诱导大鼠癫癎模型,于干预后第6d腹腔注射5-溴脱氧尿核苷嘧啶标记海马齿状回内源性神经前体细胞的增殖情况;用免疫组织化学方法及免疫荧光双标方法观察海马齿状回新生细胞的增殖、存活、分化及迁移情况。结果 （1）卡马西平可明显抑制癫癎大鼠海马齿状回新生细胞增殖;（2）卡马西平可明显促进癫癎大鼠海马齿状回新生细胞的存活;（3）卡马西平可增加癫癎大鼠海马齿状回新生神经元的数量,但不增加新生细胞分化为成熟神经元的比例;（4）卡马西平对新生神经细胞的异位迁移无抑制作用。结论卡马西平对癫癎大鼠海马齿状回神经发生的影响是其控制癫癎临床症状的可能机制之一。     

Stimulation of neurogenesis in the hippocampus of the adult rat by fluoxetine requires rhythmic change in corticosterone.

BACKGROUND: Fluoxetine stimulates proliferation of progenitor cells in the dentate gyrus of the adult hippocampus. There are suggestions that this action may underlie the therapeutic effects of such drugs in depression. Glucocorticoids also regulate neurogenesis, and there are multiple interactions between serotonin and corticoids. Diurnal cortisol rhythms are dysregulated in depression. We explored the role of diurnal variations in corticosterone on the ability of fluoxetine to alter neurogenesis in the dentate gyrus. METHODS: We manipulated plasma corticosterone by implanting corticosterone pellets or giving daily corticosterone injections to corticosterone-clamped adrenalectomized or intact rats that received fluoxetine or vehicle treatment. Proliferation of progenitor cells in the dentate gyrus was measured using BrdU or Ki-67. RESULTS: Our results strongly suggest that a diurnal rhythm in corticosterone is necessary for fluoxetine to stimulate neurogenesis in the adult dentate gyrus in the male rat. Preliminary data suggest this may be related to the 5-HT1A receptor. CONCLUSIONS: If altered neurogenesis in the dentate gyrus is part of the therapeutic response to antidepressants such as fluoxetine, the results we report suggest that concurrent manipulation of the HPA axis might improve sensitivity to selective serotonin reuptake inhibitors in some treatment-resistant patients.     

Modulation of adult hippocampal neurogenesis during myelin-directed autoimmune neuroinflammation

In chronic autoimmune diseases of the central nervous system (CNS) such as multiple sclerosis (MS) clinical signs of cognitive dysfunction have been associated with structural changes in the hippocampus. Moreover, experimental studies indicate that inflammatory responses within the CNS modulate the homeostasis of newborn cells in the adult dentate gyrus (DG). However, it remained open whether such changes happen regardless of the primary immunological target or whether a CNS antigen-directed T lymphocyte-mediated autoimmune response may exert a specific impact. We therefore induced experimental autoimmune encephalomyelitis (EAE), a common model of MS serving as a paradigm for a CNS-specific immune response, by immunizing C57BL/6 mice with encephalitogenic myelin oligodendrocyte glycoprotein (MOG) p35-55. In EAE animals, we found enhanced de novo generation and survival of doublecortin (DCX)-positive immature neurons when compared with controls immunized with CNS-irrelevant antigen (ovalbumine). However, despite activation of neurogenesis, we observed a reduced capacity of these cells to generate mature neurons. Moreover, the high number of newly born cells retained the expression of the glial marker GFAP. These effects were associated with downregulation of pro-neurogenic factors Neurogenin1 and Neurogenin2 and dysregulation of Notch, β-catenin, Sonic Hedgehog (Shh) signaling as suggested by altered gene expression of effector molecules. Thus, a CNS antigen-specific immune response leads to an aberrant differentiation of neural precursors associated with dysbalance of signaling pathways relevant for adult hippocampal neurogenesis. These results may further extend our understanding of disturbed regeneration in the course of chronic inflammatory CNS diseases such as MS.     

Age-dependent effect of prenatal stress on hippocampal cell proliferation in female rats

Stressors occurring during pregnancy can alter the developmental trajectory of offspring and lead to, among other deleterious effects, cognitive deficits and hyperactivity of the hypothalamo-pituitary-adrenal axis. A recent feature of the prenatal stress (PS) model is its reported influence on structural plasticity in hippocampal formation, which sustains both cognitive functions and stress responsiveness. Indeed, we and others have previously reported that males exposed to stress in utero are characterized by a decrease in hippocampal cell proliferation, and consequently neurogenesis, from adolescence to senescence. Recent studies in females submitted to PS have reported conflicting results, ranging from no effect to a decrease in cell proliferation. We hypothesized that changes in cell proliferation in PS female rats are age dependent. To address this issue, we examined the impact of PS on hippocampal cell proliferation in juvenile, young, middle-aged and old females. As hypothesized, we found an age-dependent effect of PS in female rats as cell proliferation was significantly decreased only when animals reached senescence, a time when adrenal gland weight also increased. These data suggest that the deleterious effects of PS on hippocampal cell proliferation in females are either specific to senescence or masked during adulthood by protective factors.     

Inverse relationship between adult hippocampal cell proliferation and synaptic rewiring in the dentate gyrus

Adult neurogenesis is a key feature of the hippocampal dentate gyrus (DG). Neurogenesis is accompanied by synaptogenesis as new cells become integrated into the circuitry of the hippocampus. However, little is known to what extent the embedding of new neurons rewires the pre-existing network. Here we investigate synaptic rewiring in the DG of gerbils (Meriones unguiculatus) under different rates of adult cell proliferation caused by different rearing conditions as well as juvenile methamphetamine treatment. Surprisingly, we found that an increased cell proliferation reduced the amount of synaptic rewiring. To help explain this unexpected finding, we developed a novel model of dentate network formation incorporating neurogenesis and activity-dependent synapse formation and remodelling. In the model, we show that homeostasis of neuronal activity can account for the inverse relationship between cell proliferation and synaptic rewiring.     

Electroconvulsive seizures induce endothelial cell proliferation in adult rat hippocampus.

BACKGROUND: Electroconvulsive seizures, an animal model for electroconvulsive treatment, induce a strong increase in neurogenesis in the dentate gyrus of adult rats. Hippocampal neurogenesis has previously been described as occurring in an angiogenic niche. This study examines the effect of electroconvulsive seizures on proliferation of vascular cells in rat hippocampus. METHODS: Rats were injected with bromodeoxyuridine to label proliferating cells in the dentate gyrus after single/multiple electroconvulsive seizures in a dose-response study and at various time points after single electroconvulsive seizures in a time-course study. RESULTS: A dose-response effect on the number of bromodeoxyuridine-labeled endothelial cells located in the granule cell layer, hilus, and molecular layer was noted, as was the case with the number of neural precursors in the subgranular zone. The time-course study revealed that endothelial cell and neural precursor proliferation occurred in concert in response to a single electroconvulsive seizure. CONCLUSIONS: Our data suggest that in response to electroconvulsive seizures, endothelial cell and neural proliferation is coregulated. The increase in endothelial cell proliferation may act to support the increased neural proliferation and neuronal activity or vice versa, possibly leading to structural changes within the hippocampus of importance for the antidepressant effect of electroconvulsive seizures.     

Short-term and long-term survival of new neurons in the rat dentate gyrus

New neurons continue to be generated in the dentate gyrus throughout adulthood. Previous studies have shown that a significant proportion of new granule cells labeled with the thymidine analogue bromodeoxyuridine (BrdU) are lost from the adult dentate gyrus within 2 weeks. How long this loss continues and the extent to which it represents cell death, as opposed to dilution of label, is unclear. To address these questions, adult rats were injected with BrdU, and BrdU labeling in the dentate gyrus was compared at several survival time points. Double labeling with BrdU and the cell cycle marker Ki-67 showed that BrdU is detectable for up to 4 days in some cells that continue to divide, indicating that any decrease in the number of BrdU-labeled cells after 4 days is likely to reflect cell death rather than BrdU dilution. Death of new cells in the granule cell layer occurred at a steady rate between 6 and 28 days after labeling, resulting in loss of 50% of BrdU-labeled cells over this 22-day period. New granule cells that survived this first month lived for at least 5 additional months. In contrast, 26% of the granule cells labeled with BrdU at the peak of dentate gyrus development on postnatal day (P) 6 died between 1 and 6 months after labeling. These findings suggest that granule cells born during adulthood that become integrated into circuits and survive to maturity are very stable and may permanently replace granule cells born during development.     

Passive avoidance training is correlated with decreased cell proliferation in the chick hippocampus

One-trial passive avoidance learning (PAL), where the aversive stimulus is the bitter-tasting substance methylanthranilate (MeA), affects neuronal and synaptic plasticity in learning-related areas of day-old domestic chicks (Gallus domesticus). Here, cell proliferation was examined in the chick forebrain by using 5-bromo-2-deoxyuridine (BrdU) at 24 h and 9 days after PAL. At 24 h post-BrdU injection, there was a significant reduction in labelling in MeA-trained chicks in both the dorsal hippocampus and area parahippocampalis, in comparison to controls. Moreover, double-immunofluorescence labelling for BrdU and the nuclear neuronal marker (NeuN) showed a reduction of neuronal cells in the dorsal hippocampus of the MeA-trained group compared with controls (35 and 49%, respectively). There was no difference in BrdU labelling in hippocampal regions between trained and control groups of chicks at 9 days post-BrdU injection; however, the number of BrdU-labelled cells was considerably lower than at 24 h post-BrdU injection, possibly due to migration of cells within the telencephalon rather than cell loss as apoptotic analyses at 24 h and 9 days post-BrdU injection did not demonstrate differences in cell death between treatment groups. Cortisol levels increased in the chick hippocampus of MeA-trained birds 20 min after PAL, suggesting the possibility of a stress-related mechanism of cell proliferation reduction in the hippocampus. In contrast to hippocampal areas, the olfactory bulb, an area strongly stimulated by the strong-smelling MeA, showed increased cell genesis in comparison to controls at both 24 h and 9 days post-training.     

Serotonin mediates oestrogen stimulation of cell proliferation in the adult dentate gyrus

Characterizing the mechanisms by which endogenous factors stimulate neurogenesis is of special interest in view of the possible implication of newly generated cells in hippocampal functions or disorders. The aim of this study was to determine whether serotonin (5-HT) and oestradiol (E2) act through a common pathway to increase cell proliferation in the adult dentate gyrus (DG). We also investigated the effects of long-lasting changes in oestrogen levels on cell proliferation. Combining ovariectomy with inhibition of 5-HT synthesis using p-chlorophenylalanine (PCPA) treatment produced approximately the same decreases in the number of bromodeoxyuridine (BrdU) and PSA-NCAM immunolabelled cells in the subgranular layer as ovariectomy alone. Administration of 5-hydroxytryptophan (5-HTP) restored cell proliferation primarily decreased by ovariectomy, whereas oestradiol was unable to reverse this change in ovariectomized rats treated with PCPA. These findings demonstrate that 5-HT mediates oestrogen stimulation of cell proliferation in adult dentate gyrus. However, increase in ovarian hormones during pregnancy has no effect on dentate cell proliferation. This finding suggests that concomitant changes in other factors, such as glucocorticoids, may counterbalance the positive regulation of cell proliferation by 5-HT and oestradiol. Finally, oestrogen may regulate structural plasticity by stimulating PSA-NCAM expression independently of neurogenesis, as shown for instance by the increases in the number of PSA-NCAM labelled cells in pregnants. As 5-HT and oestrogen are involved in mood disorders, our data suggest that the positive regulation of cell proliferation and neuroplasticity by these two factors may contribute to restore hippocampal connectivity in depressive patients.