Early life stress stimulates hippocampal reelin gene expression in a sex-specific manner: evidence for corticosterone-mediated action

Early life stress predisposes to the development of psychiatric disorders. In this context the hippocampal formation is of particular interest, because it is affected by stress on the structural and cognitive level. Since little is known how early life stress is translated on the molecular level, we mimicked early life stress in mouse models and analyzed the expression of the glycoprotein Reelin, a master molecule for development and differentiation of the hippocampus. From postnatal day 1 (P1) to P14, mouse pups were subjected to one of the following treatments: nonhandling (NH), handling (H), maternal separation (MS), and early deprivation (ED) followed by immediate (P15) or delayed (P70) real time RT-PCR analysis of reelin mRNA expression. We show that at P15, reelin mRNA levels were significantly increased in male H and ED groups when compared with the NH group. In contrast, no stress-induced alterations of reelin mRNA expression were found in female animals. This sex difference in stress-mediated stimulation of reelin expression was maintained into adulthood, since at P70 intergroup differences were still found in male, but not in female mice. On the cellular level, however, we did not find any significant differences in cell densities of Reelin-immunolabeled neurons between treatment groups or sexes, but an overall reduction of Reelin-expressing neurons in the adult hippocampus when compared to P15. To address the question whether corticosterone mediates the stress-induced up-regulation of reelin gene expression, we used age-matched hippocampal slice cultures derived from male and female mouse pups. Quantitative determination of mRNA levels revealed that corticosterone treatment significantly up-regulated reelin mRNA expression in male, but not in female hippocampi. Taken together, these results show a sex-specific regulation of reelin gene expression by early life experience, most likely mediated by corticosterone.     

Differential expression of molecular markers of synaptic plasticity in the hippocampus, prefrontal cortex, and amygdala in response to spatial learning, predator exposure, and stress-induced amnesia

We have studied the effects of spatial learning and predator stress-induced amnesia on the expression of calcium/calmodulin-dependent protein kinase II (CaMKII), brain-derived neurotrophic factor (BDNF) and calcineurin in the hippocampus, basolateral amygdala (BLA), and medial prefrontal cortex (mPFC). Adult male rats were given a single training session in the radial-arm water maze (RAWM) composed of 12 trials followed by a 30-min delay period, during which rats were either returned to their home cages or given inescapable exposure to a cat. Immediately following the 30-min delay period, the rats were given a single test trial in the RAWM to assess their memory for the hidden platform location. Under control (no stress) conditions, rats exhibited intact spatial memory and an increase in phosphorylated CaMKII (p-CaMKII), total CaMKII, and BDNF in dorsal CA1. Under stress conditions, rats exhibited impaired spatial memory and a suppression of all measured markers of molecular plasticity in dorsal CA1. The molecular profiles observed in the BLA, mPFC, and ventral CA1 were markedly different from those observed in dorsal CA1. Stress exposure increased p-CaMKII in the BLA, decreased p-CaMKII in the mPFC, and had no effect on any of the markers of molecular plasticity in ventral CA1. These findings provide novel observations regarding rapidly induced changes in the expression of molecular plasticity in response to spatial learning, predator exposure, and stress-induced amnesia in brainregions involved in different aspects of memory processing.     

Afferent-specific modulation of short-term synaptic plasticity by neurotrophins in dentate gyrus

Neurotrophins modulate synaptic transmission and plasticity in the adult brain. We here show a novel feature of this synaptic modulation, i.e. that two populations of excitatory synaptic connections to granule cells in the dentate gyrus, lateral perforant path (LPP) and medial perforant path (MPP), are differentially influenced by the neurotrophins BDNF and NT-3. Using field recordings and whole-cell patch-clamp recordings in hippocampal slices, we found that paired-pulse (PP) depression at MPP-granule cell synapses was impaired in BDNF knock-out (+/-) mice, but PP facilitation at LPP synapses to the same cells was not impaired. In accordance, scavenging of endogenous BDNF with TrkB-IgG fusion protein also impaired PP depression at MPP-granule cell synapses, but not PP facilitation at LPP-granule cell synapses. Conversely, in NT-3+/- mice, PP facilitation was impaired at LPP-granule cell synapses whilst PP depression at MPP-granule cell synapses was unaffected. These deficits could be reversed by application of exogenous neurotrophins in an afferent-specific manner. Our data suggest that BDNF and NT-3 differentially regulate the synaptic impact of different afferent inputs onto single target neurons in the CNS.     

Neutralization of neutrophin-3 in the ventral tegmental area or nucleus accumbens differentially modulates cocaine-induced behavioral plasticity in rats

These experiments were designed to assess the influence of neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF) in the mesoaccumbens dopamine system on the initiation of behavioral sensitization to cocaine. A neutralizing antibody for NT-3, BDNF or their vehicle was administered into the ventral tegmental area (VTA) or nucleus accumbens prior to each of four daily injections of 15 mg/kg cocaine. Behavioral sensitization was operationally defined as a significant increase in the behavioral response to cocaine relative to the first daily injection. Results indicated that the NT-3 antibody had differential effects when administered into the VTA or nucleus accumbens. Intra-VTA microinjection of anti-NT-3 resulted in enhanced sensitization to repeated cocaine injections in that the cocaine-induced behavioral response in the anti-NT-3 group was significantly greater than the vehicle group following the second and third daily injections of cocaine. Administration of anti-NT-3 into the nucleus accumbens increased the behavioral response to cocaine over all 4 days of cocaine administration, with no sensitization of this behavioral response. In contrast, pretreatment with anti-BDNF into the VTA or nucleus accumbens had no influence on the initiation of behavioral sensitization to cocaine. Taken together, these data indicate that neutralization of NT-3 in the VTA enhances cocaine-induced behavioral sensitization, while administration of the NT-3 antibody into the nucleus accumbens increases the hyperactive behavioral response induced by cocaine but impairs the further development of behavioral sensitization.     

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。     

Acute stress-induced impairment of spatial memory is associated with decreased expression of neural cell adhesion molecule in the hippocampus and prefrontal cortex.

BACKGROUND: There is an extensive literature describing how stress disturbs cognitive processing and can exacerbate psychiatric disorders. There is, however, an insufficient understanding of the molecular mechanisms involved in stress effects on brain and behavior. METHODS: Rats were given spatial memory training in a hippocampus-dependent water maze task. We investigated how a fear-provoking experience (predator exposure) would affect their spatial memory and neural cell adhesion molecule (NCAM) levels in the hippocampus, prefrontal cortex (PFC), amygdala, and cerebellum. RESULTS: Whereas the control (nonstress) group exhibited excellent memory for the hidden platform location in the water maze, the cat-exposed (stress) group exhibited a profound impairment of memory and a marked suppression of levels of the NCAM-180 isoform in the hippocampus. Predator stress produced a more global reduction of NCAM levels in the PFC but had no effect on NCAM levels in the amygdala and cerebellum. CONCLUSIONS: This work provides a novel perspective into dynamic and structure-specific changes in the molecular events involved in learning, memory, and stress. The selective suppression of NCAM-180 in the hippocampus and the more general suppression of NCAM in the PFC provide insight into the mechanisms underlying the great sensitivity of these two structures to be disturbed by stress.     

Microinfusion of a corticotrophin-releasing hormone receptor 1 antisense oligodeoxynucleotide into the dorsal hippocampus attenuates stress responses at specific times after stress exposure

Corticotrophin-releasing hormone (CRH) plays a key role in the adjustment of neuroendocrine and behavioural adaptations to stress. Dysregulation in CRH systems has been implicated in a variety of stress-related psychiatric disorders such as post-traumatic stress disorder (PTSD). The present study examined the relationship between stress-induced PTSD-like behavioural response patterns and levels of CRH, CRH receptor (CHR-R)1 and phosphorylated extracellular signal-regulated kinase (pERK1/2) in the rat hippocampus subregions. The effects of pharmacological manipulations on behavioural, physiological and response patterns of brain-derived neurotrophic factor (BDNF) and pERK1/2 expression using a CRH receptor (CRH-R)1-antisense oligodeoxynucleotide (CRH-R1-ASODN) were evaluated. CRH and CRH-R1 mRNA and pERK1/2 protein levels were assessed in the hippocampus subregions 7 days after exposure to predator scent stress (PSS). The effects of CRH-ASODN versus CRH-Scrambled-ODN microinfusion to the dorsal hippocampus either 1 h or 48 h post-exposure on behavioural tests (elevated plus maze and acoustic startle response) were evaluated 7 days later, 14 days after PSS exposure. Localised brain expression of BDNF and ERK1/2 was subsequently assessed. All data were analysed in relation to individual behaviour patterns. A distinct pattern associated with extreme behavioural response (EBR) was revealed in the bioassay of behavioural study subjects, classified according to their individual patterns of behavioural response at 7 days. These EBR individuals displayed significantly higher CRH and CRH-R1 mRNA levels in the CA1 and CA3 areas, mediating down-regulation of pERK1/2 protein levels. Microinfusion of a CRH-R1-ASODN into the dorsal hippocampus 48 h after stress exposure, although not immediately after exposure (1 h), significantly reduced behavioural disruption and was associated with concomitant up-regulation of BDNF and pERK1/2 protein levels compared to CRH-R1-Scrambled -ODN controls. CRH/CRH-R1 is actively involved in the neurobiological response to predator scent stress processes and thus warrants further study as a potential therapeutic avenue for the treatment of anxiety-related disorders.     

Brain-derived neurotrophic factor-mediated effects on mitochondrial respiratory coupling and neuroprotection share the same molecular signalling pathways

Intracerebral injection of ibotenate into mouse pups induced grey matter lesions and white matter cysts; co-administration of brain-derived neurotrophic factor (BDNF) produced a dose-dependent reduction in these lesions. In contrast, glial cell line-derived neurotrophic factor (GDNF) had no significant effect, whereas nerve growth factor (NGF) or interleukin-1β (IL-1β) resulted in dose-dependent exacerbation. The neuroprotective effects of BDNF were abolished by co-administration of anti-BDNF antibody or MEK inhibitors, or ABT-737, a BH3 mimetic and Bcl-2 antagonist. The actions of BDNF, GDNF and NGF were measured in a parallel in vitro study on the oxidative metabolism of mouse brain mitochondria. BDNF produced a concentration-dependent increase in the respiratory control index (RCI, a measure of respiratory coupling efficiency, ATP synthesis, and organelle integrity) when co-incubated with synaptosomes containing signal transduction pathways; but GDNF failed to modify RCI, and NGF had only weak effects. BDNF had no effect on pure mitochondria, and enhanced oxidation only when complex I substrates were used. The effect of BDNF was inhibited by anti-BDNF antibody, MEK inhibitors or ABT-737, and also by IL-1β, indicating that the mitochondrial effects are mediated via the same MEK-Bcl-2 pathway as the neuroprotection. The complex I inhibitor rotenone, a compound implicated in the aetiology of Parkinson's disease, inhibited both the in vitro mitochondrial and in vivo neuroprotective effects of BDNF. The ability of BDNF to modify brain metabolism and the efficiency of oxygen utilization via a MEK-Bcl-2 pathway may be an important component of the neuroprotective action observed with this neurotrophin.     

Neuroendocrine plasticity in GnRH release during rat estrous cycle: correlation with molecular markers of synaptic remodeling

Morphological changes in the gonadotropin releasing hormone (GnRH) neurons in the preoptic area (POA) and their terminals in the median eminence-arcuate (ME-ARC) region are reported to occur during ovarian cycle that may be involved in the GnRH release into the portal blood during preovulatory surge. However, the neuronal substrates participating in altered GnRH neuronal plasticity are poorly understood. The present study was designed to determine whether morphological changes occurring in the GnRH neuron cell bodies in the POA and their terminals in the ME-ARC region of hypothalamus with pulsatile GnRH release in cycling female rats are associated with expression of intrinsic determinants of neuronal plasticity. The plasticity markers studied are polysialylated neural cell adhesion molecule (PSA-NCAM), high molecular weight isoforms of NCAM, growth associated protein (GAP-43), glial fibrillary acidic protein (GFAP) and synaptophysin. Regularly cycling female rats were sacrificed at diestrous, i.e., when GnRH release is low, and at proestrous, i.e., when preovulatory GnRH surge occurs, using perfusion fixation method for immunohistochemical staining of GnRH cells. GnRH cell bodies and their terminals from the POA and ME-ARC region respectively, were localized using immunohistochemical technique in proestrous and diestrous phase of estrous cycle and our results showed a marked increase in the GnRH nerve terminals length and immunoreactivity in the ME-ARC region from proestrous phase rats as compared to diestrous rats. Immunoblot analyses of the POA and ME-ARC region of the hypothalamus revealed a significant increase in the content of PSA-NCAM, NCAM-180, NCAM-140, GAP-43 and synaptophysin from proestrous phase rats as compared to diestrous phase rats. The ME-ARC region showed more pronounced increase in the protein expression of these markers of neuronal plasticity as compared to the POA, whereas, hippocampal region did not show any significant change in the content of these markers showing specificity of the changes to the GnRH system. GFAP content was significantly decreased in the POA with a marginal increase in the GFAP level from the ME-ARC region. These results demonstrate the involvement of synaptic proteins in the dynamic plasticity of the ME-ARC region of hypothalamus, allowing GnRH nerve terminals to release the neurohormone into the pituitary portal blood on the day of proestrous.     

Novel role for aspartoacylase in regulation of BDNF and timing of postnatal oligodendrogenesis

Neuronal growth factors are thought to exert a significant degree of control over postnatal oligodendrogenesis, but mechanisms by which these factors coordinateoligodendrocyte development with the maturation of neural networks are poorly characterized. We present here a developmental analysis of aspartoacylase (Aspa)-null tremor rats and show a potential role for this hydrolytic enzyme in the regulation of a postnatal neurotrophic stimulus that impacts on early stages of oligodendrocyte differentiation. Abnormally high levels of brain-derived neurotrophic factor (BDNF) expression in the Aspa-null Tremor brain are associated with dysregulated oligodendrogenesis at a stage in development normally characterized by high levels of Aspa expression. BDNF promotes the survival of proliferating cells during the early stages of oligodendrocyte maturation in vitro, but seems to compromise the ability of these cells to populate the cortex in vivo. Aspartoacylase activity in oligodendrocytes is shown to provide for the negative regulation of BDNF in neurons, thereby determining the availability of a developmental stimulus via a mechanism that links oligodendroglial differentiation with neuronal maturation.     

Effects of neural stem cells on synaptic proteins and memory in a mouse model of Alzheimer's disease

Transplanting neural stem cells (NSC) to the damaged brain has been regarded as a potential treatment for neurodegenerative diseases such as Alzheimer's disease (AD), a condition characterized by memory loss. We hypothesized that transplantation of NSC into the hippocampal regions of APP + PS1 transgenic (Tg) mice, a well‐established model of AD, would enhance the expression of synaptic proteins, which may be helpful for improving cognitive function. Our results showed that NSC transplantation significantly improved spatial learning and memory function in Tg mice. The results obtained by real‐time RT‐PCR, immunofluorescence, and Western blot analyses demonstrated that the expression of synaptophysin (SYN) and that of growth‐associated protein‐43 (GAP‐43) in Tg‐NSC mice, 8 weeks after transplantation, were significantly improved compared with what was observed in Tg‐Veh (control) mice. This finding was confirmed by the increase in the number of synapses in Tg‐NSC mice as observed via electron microscopy. Our results suggest that NSC‐induced changes can recover memory loss in APP + PS1 transgenic mice, possibly by establishing new neural circuits resulting from the engrafted NSC. © 2013 Wiley Periodicals, Inc.     

补肾壮阳胶囊对精神分裂症模型大鼠海马胶质细胞源性神经营养因子表达的影响

目的 探讨补肾壮阳胶囊(WSKY)对地卓西平马来酸盐(MK801)建立的精神分裂症模型大鼠海马胶质细胞源性神经营养因子(GDNF)表达的影响.方法 将40只6周龄SD雄性大鼠随机分为3组:对照组(生理盐水腹腔注射+生理盐水灌胃)、模型组(M K801腹腔注射+生理盐水灌胃)及WSKY+MK801组(MK801腹腔注射+WSKY灌胃,而根据WSKY剂量的不同又分为3个亚组);各组相应处理两周后运用Western Blot和RT-PCR技术分别检测各组大鼠海马区GDNF蛋白及mRNA的表达.结果 与对照组相比较,模型组的GDNF蛋白及mRNA的表达下降,差异有统计学意义(P<0.05);而与模型组相比,WSKY+MK801组中较高剂量WSKY可致GDNF蛋白及其mRNA的表达增加,差异有统计学意义(P<0.05).结论 MK801可致大鼠海马GDNF表达减少,而补肾壮阳胶囊可上调大鼠海马GDNF的表达.     

Association of the BDNF C270T polymorphism with schizophrenia: Updated meta‐analysis

Brain‐derived neurotrophic factor (BDNF) has been suggested to play a role in the pathophysiology of schizophrenia. The C270T polymorphism (rs56164415) in the BDNF 5′‐non‐coding region has been extensively investigated for an association with schizophrenia, but with conflicting results. An updated meta‐analysis was therefore performed of 13 case–control association studies (3505 patients and 3992 controls). An association was found between the T allele and schizophrenia. The association was significant in the East Asian population, but not in the Caucasian population. It is suggested that the BDNF C270T polymorphism contributes to schizophrenia susceptibility, especially in East Asian subjects.     

神经细胞黏附分子在GDNF保护大鼠多巴胺能神经元中的作用

目的研究神经细胞黏附分子(neural cell adhesion molecule,NCAM)在胶质细胞系源性神经营养因子(glial cell line-derived neurotrophic factor,GDNF)保护帕金森(Parkinson's disease,PD)模型大鼠受损多巴胺(dopamine,DA)能神经元中的作用。方法右侧纹状体内立体定位注射6-羟多巴胺(6-OHDA)制备早期PD模型,而后分为4组:对照组(同侧黑质内注射PBS)、NCAM组(同侧黑质内仅注射anti-NCAM抗体)、GDNF组(同侧黑质内注射GDNF)、NCAM阻断组(同侧黑质内注射anti-NCAM抗体30min后注射GDNF),采用免疫组织化学染色技术和免疫印迹技术,观察各组酪氨酸羟化酶(tyrosine hydroxylase,TH)的表达变化。结果GDNF组黑质致密部TH阳性神经元数目及表达的量明显多于PBS组,差别有统计学意义;NCAM阻断组与GDNF组相比,该处TH阳性神经元数目及表达的量明显减少,差别有统计学意义。结论NCAM参与了GDNF保护DA能神经元的作用。     

胶质细胞系源性神经营养因子对帕金森病大鼠黑质钙结合蛋白表达的影响

目的研究胶质细胞系源性神经营养因子(GDNF)对帕金森病(PD)大鼠黑质钙结合蛋白(CB)表达的影响,以及神经细胞黏附分子(NCAM)在其中的作用。方法制作PD模型大鼠36只,分为GD-NF组、NCAM阻断组和对照组,每组12只。采用免疫组化染色和免疫印迹法,检测各组大鼠黑质CB阳性细胞数和CB表达量。结果GDNF组黑质处CB阳性神经元数(46.50±6.28)及表达量(33770.60±6929.76)明显高于对照组[(27.00±8.60)、(18281.00±5266.78)](均P<0.05);与NCAM阻断组[(44.00±13.37)、(30857.00±7484.87)]相比差异无统计学意义(均P>0.05)。结论GDNF可上调PD大鼠黑质CB的表达,从而保护受损的多巴胺能神经元,NCAM对这一作用无明显影响。     

Light modulates hippocampal function and spatial learning in a diurnal rodent species: A study using male nile grass rat (Arvicanthis niloticus)

The effects of light on cognitive function have been well‐documented in human studies, with brighter illumination improving cognitive performance in school children, healthy adults, and patients in early stages of dementia. However, the underlying neural mechanisms are not well understood. The present study examined how ambient light affects hippocampal function using the diurnal Nile grass rats (Arvicanthis niloticus) as the animal model. Grass rats were housed in either a 12:12 h bright light–dark (brLD, 1,000 lux) or dim light‐dark (dimLD, 50 lux) cycle. After 4 weeks, the dimLD group showed impaired spatial memory in the Morris Water Maze (MWM) task. The impairment in their MWM performance were reversed when the dimLD group were transferred to the brLD condition for another 4 weeks. The results suggest that lighting conditions influence cognitive function of grass rats in a way similar to that observed in humans, such that bright light is beneficial over dim light for cognitive performance. In addition to the behavioral changes, grass rats in the dimLD condition exhibited reduced expression of brain‐derived neurotrophic factor (BDNF) in the hippocampus, most notably in the CA1 subregion. There was also a reduction in dendritic spine density in CA1 apical dendrites in dimLD as compared to the brLD group, and the reduction was mostly in the number of mushroom and stubby spines. When dimLD animals were transferred to the brLD condition for 4 weeks, the hippocampal BDNF and dendritic spine density significantly increased. The results illustrate that not only does light intensity affect cognitive performance, but that it also impacts hippocampal structural plasticity. These studies serve as a starting point to further understand how ambient light modulates neuronal and cognitive functions in diurnal species. A mechanistic understanding of the effects of light on cognition can help to identify risk factors for cognitive decline and contribute to the development of more effective prevention and treatment of cognitive impairment in clinical populations.     

Decreased levels of brain-derived neurotrophic factor in the remitted state of unipolar depressive disorder

Hasselbalch BJ, Knorr U, Bennike B, Hasselbalch SG, Greisen Søndergaard MH, Vedel Kessing L. Decreased levels of brain‐derived neurotrophic factor in the remitted state of unipolar depressive disorder. Objective: Decreased levels of peripheral brain‐derived neurotrophic factor (BDNF) have been associated with depression. It is uncertain whether abnormally low levels of BDNF in blood are present beyond the depressive state and whether levels of BDNF are associated with the course of clinical illness. Method: Whole‐blood BDNF levels were measured in blood samples from patients with unipolar disorder in a sustained state of clinical remission and in a healthy control group. Participants were recruited via Danish registers, a method that benefits from the opportunity to obtain well‐matched community‐based samples as well as providing a high diagnostic validity of the patient sample. Results: A total of 85 patients and 50 controls were included in the study. In multiple linear regression analyses, including the covariates age, gender, 17‐item Hamilton Depression Rating Scale scores, body‐mass index, education, smoking and physical exercise, patients with unipolar depressive disorder had decreased levels of BDNF compared to healthy control individuals [B = ?7.4, 95% CI (?11.2, ?3.7), = 0.21 P < 0.001]. No association between course of clinical illness and BDNF levels was present. Conclusion: Whole‐blood BDNF levels seem to be decreased in patients remitted from unipolar depressive disorder, suggesting that neurotrophic changes may exist beyond the depressive state.