Changes in tau phosphorylation levels in the hippocampus and frontal cortex following chronic stress

Studies have indicated that early-life or early-onset depression is associated with a 2- to 4-fold increased risk of developing Alzheimers disease (AD). In AD, aggregation of an abnormally phosphorylated form of the tau protein may be a key pathological event. Tau is known to play a major role in promoting microtubule assembly and stabilization, and in maintaining the normal morphology of neurons. Several studies have reported that stress may induce tau phosphorylation. The main aim of the present study was to investigate possible alterations in the tau protein in the hippocampus and frontal cortex of 32 male Sprague-Dawley rats exposed to chronic unpredictable mild stress (CUMS) and then re-exposed to CUMS to mimic depression and the recurrence of depression, respectively, in humans. We evaluated the effects of CUMS, fluoxetine, and CUMS re-exposure on tau and phospho-tau. Our results showed that a single exposure to CUMS caused a significant reduction in sucrose preference, indicating a state of anhedonia. The change in behavior was accompanied by specific alterations in phospho-tau protein levels, but fluoxetine treatment reversed the CUMS-induced impairments. Moreover, changes in sucrose preference and phospho-tau were more pronounced in rats re-exposed to CUMS than in those subjected to a single exposure. Our results suggest that changes in tau phosphorylation may contribute to the link between depression and AD.     

皮质酮与慢性不可预见性应激诱导的两种抑郁症模型比较

目的从行为学及分子水平比较皮质酮(CORT)与慢性不可预见性应激(CUMS)诱导的抑郁症模型的异同,为抑郁症发病机制研究及抗抑郁药物的筛选与评价模型提供一定的参考。方法将30只雄性C57BL/6小鼠随机分成对照组(Ctrl)、慢性不可预见应激组(CUMS)和皮质酮注射应激组(CORT)组,制作应激模型21d,期间每3d对小鼠进行称重。21d模型制作结束后,对小鼠进行行为学测试,并于第22天,通过眼眶取血收集动物血清,并用ELISA法测定血清皮质酮含量。眼眶取血后脱颈椎处死动物,取出动物的胸腺和脾脏进行称重,计算脏器指数;取出脑组织,置于液氮罐保存,尼氏(Nissl)染色法观察小鼠大脑海马区神经元损伤情况;采用Western blotting、RT-PCR方法测定抑郁症相关蛋白及基因的表达。结果与对照组相比,两种抑郁症模型组开场实验中的行为学指标均改变,强迫游泳和悬尾实验的累积不动时间显著升高。两个模型组的胸腺指数无明显变化,而CORT组的脾脏指数较对照组下降。CUMS和CORT组小鼠血清皮质酮含量高于对照组,CORT组与CUMS组相比有升高趋势,但差异无显著性。CUMS和CORT两种模型均使海马CA1、CA3和DG区神经元密度降低,CORT模型变化更明显。两模型组的促肾上腺素释放激素(CRH)的mRNA和蛋白的表达量均显著性增加,脑源性神经营养因子(BDNF)、磷酸化转录因子环磷腺苷反应元件结合蛋白(p-CREB)和磷酸化细胞外信号调节激酶(p-ERK)的蛋白表达水平均呈现明显地抑制,但CUMS和CORT两组之间差异无显著性。结论 CORT模型和CUMS模型均能成功构建抑郁症模型,且与下丘脑-垂体-肾上腺(HPA)轴紊乱有关,两种模型在小鼠海马结构改变及大脑BDNF-pCREB和ERK信号通路激活等方面差异无显著性。提示,CORT模型可用于抑郁症机制的研究及抗抑郁药的筛选与评价,尤其可用于以HPA轴功能紊乱所引起的抑郁症分子机制探讨。     

Chronic immobilization stress induces anxiety- and depression-like behaviors and decreases transthyretin in the mouse cortex

In this study, we examined the changes in gene expression in the mouse cortex following chronic stress and behavioral tests. Mice were subjected to immobilization stress for 2 h per day for 15 consecutive days and the behavior of the mice was examined. The mice in the experimental group were more anxious and depressive than the control mice. The expression of mRNA in the cortex was analyzed by microarray analysis and 63 genes were found to show a greater than twofold change in expression between the control and experimental groups. Transthyretin was further investigated because its expression showed the greatest fold change. Transthyretin mRNA expression decreased in a chronic stress-specific manner, and protein levels were reduced in the cortex but not in the choroid plexus.     

Chronic mild restraint stress rats decreased CMKLR1 expression in distinct brain region

Inflammation contributes to the pathophysiology of depression. Chemokine-like receptor-1 (CMKLR1) plays an important role both in the development of inflammation and in the mechanism of antidepressant effect of Omega-3 polyunsaturated fatty acids (Omega-3 PUFAs), ecosapeatanolicacid (EPA). The present study was to investigate the modification of CMKLR1 in chronic restraint stress (CRS) rats. CMKLR1 was examined in different brain region from CRS rats by using western blot and quantitative real-time PCR. The CMKLR1 expression in the hippocampus, prefrontal cortex and cerebellum was determined on 3, 7, 10 and 21 days of repeated restraint stress and was compared to controls. The results showed that the protein and mRNA level of CMKLR1 in the prefrontal cortex and hippocampus were significantly increased on day 3 and then decreased on day 7, 10 and 21 in the CRS rats. The protein and mRNA level of CMKLR1 in cerebellum was similar to that of control group throughout the whole experiment. Changed expression of brain CMKLR1 is suggested to be involved in the mechanism of depression.     

慢性不可预见性应激对大鼠大脑皮质及海马酪氨酸硝基化的影响

目的：探讨慢性应激能否使SD大鼠大脑皮质神经细胞产生蛋白质酪氨酸硝基化。方法：将40只SD大鼠随机分为对照组和慢性不可预见性应激组各20只,用慢性不可预见性应激模型法造模,时间分为1周、2周和3周,每周用Open-field法给予行为学评分,并用组织化学和免疫组织化学法染色观察大脑神经细胞形态和其蛋白质酪氨酸硝基化的变化。结果：慢性不可预见性应激组与对照组神经细胞形态有明显的不同,且出现蛋白质酪氨酸硝基化,两组相比具有显著统计学意义。结论：慢性不可预见性应激模型鼠的大脑皮质神经细胞发生慢性应激损伤,是有效的慢性应激模型,其发生机制至少部分与NO~ 的产生而导致神经细胞蛋白质酪氨酸硝基化有关。     

脑室亚低温对急性脑梗塞脑组织兔细胞凋亡和Caspase-3表达的影响

目的检测低温组和常温组家兔大脑中动脉脑梗塞周边缺血区脑组织细胞凋亡和Caspase-3表达,探讨脑室内低温对家兔大脑中动脉梗塞模型脑组织细胞凋亡影响。方法选用4-6个月龄雄性家兔20只,随机分为常温组(10只)和低温组(10只)。应用线栓法建立大脑中动脉闭塞(MCAO)模型,进行脑室内穿刺低温液体灌注亚低温干预,术后动物行为观察,SP和Western blot法检测各组脑组织Caspase-3的表达,TUNEL方法检测细胞凋亡。结果术后24h神经病学体征评分低温组明显优于常温组(P0.05),低温组的TUNEL染色凋亡细胞数和Caspase-3染色阳性细胞数明显低于常温组(P0.05),Western blot表明低温组脑组织中Caspase-3的表达水平明显低于常温组(P0.05)。结论脑室内穿刺低温干预对急性脑梗塞动物模型有脑保护作用。     

The effect of aging on the neuronal population within area 17 of adult rat cerebral cortex

The brains of Sprague-Dawley rats in various age groups from 3 to 33 months were fixed by perfusion with standard aldehyde solutions in order to determine the effects of aging on neuronal numbers. Several indices of cortical volume were then measured to determine whether neuronal packing densities were affected by age-related change in cortical volume. The lengths, heights and widths of individual hemispheres for 160 animals ranging in age from 1 day to 36 months were first determined, after which blocks of tissue were removed from area 17 of some of the brains. These blocks were osmicated, embedded in Araldite and sectioned at 1 micrometer to ascertain, in the vertical plane, the thickness of area 17 and, in the tangential plane, the packing density of the clusters of apical dendrites extending from layer V pyramidal neurons. Results indicate the overall dimensions of the cerebral hemispheres increased until 3 months of age, after which there was no further increase in size. Between 3 and 33 months of age there was no age-related change in either the thickness of area 17 or in the separation between dendritic clusters, indicating the volume of area 17 did not change after 3 months of age. Within individual age groups the amount of variation present is greater than that among age groups. Since the number of nucleus-containing neuronal profiles per unit area of layers II/III, IV, V, VIa and VIb was similar in two groups of three animals at 3 and 33 months of age and the diameters of neuronal nuclei were unchanged, there seems to be no significant change in the number of neurons contained in these layers of rat visual cortex between 3 and 33 months of age. It is therefore concluded that no neurons are lost from area 17 as the mature cerebral cortex ages.     

The effect of aging on the neuronal population within area 17 of adult rat cerebral cortex

The brains of Sprague-Dawley rats in various age groups from 3 to 33 months were fixed by perfusion with standard aldehyde solutions in order to determine the effects of aging on neuronal numbers. Several indices of cortical volume were then measured to determine whether neuronal packing densities were affected by age-related change in cortical volume. The lengths, heights and widths of individual hemispheres for 160 animals ranging in age from 1 day to 36 months were first determined, after which blocks of tissue were removed from area 17 of some of the brains. These blocks were osmicated, embedded in Araldite and sectioned at 1 micrometer to ascertain, in the vertical plane, the thickness of area 17 and, in the tangential plane, the packing density of the clusters of apical dendrites extending from layer V pyramidal neurons. Results indicate the overall dimensions of the cerebral hemispheres increased until 3 months of age, after which there was no further increase in size. Between 3 and 33 months of age there was no age-related change in either the thickness of area 17 or in the separation between dendritic clusters, indicating the volume of area 17 did not change after 3 months of age. Within individual age groups the amount of variation present is greater than that among age groups. Since the number of nucleus-containing neuronal profiles per unit area of layers II/III, IV, V, VIa and VIb was similar in two groups of three animals at 3 and 33 months of age and the diameters of neuronal nuclei were unchanged, there seems to be no significant change in the number of neurons contained in these layers of rat visual cortex between 3 and 33 months of age. It is therefore concluded that no neurons are lost from area 17 as the mature cerebral cortex ages.     

A Golgi study on the neuronal organization of the interhemispheric cortex in the mouse

Summary The intrinsic neurons in the interhemispheric cortex (IHC) were studied by the rapid Golgi method in the young mouse. In each of the five layers of the IHC, a wide variety of intrinsic neurons were observed. They were classified into several groups according mainly to the patterns of axonal and dendritic distribution.The Cajal-Retzius cells were most frequently seen in layer I. The dendrites and axons of these neurons ran irregularly in the plane parallel to the pial surface of the IHC. Many neurons in layers II–V were observed to send their axons to layer I. Some of these neurons took the form of the inverted pyramidal neurons. The axons of some neurons in layers II, III and IV formed dense axonal plexuses usually in layer III and rarely in layer II. The dendrites of many neurons in layers IV and V extended into the cingulum. The stellate neurons embedded in the cingulum might be the dislocated neurons of layer V.     

Long-term increases in neuronal activity in the motor cortex evoked by simultaneous stimulation of the thalamus and somatosensory cortex in cats

Experiments on anesthetized cats were used to study the activity of motor cortex neurons (field 4γ) in response to separate and simultaneous stimulation of the ventrolateral nucleus of the thalamus and the somatosensory cortex (field 2) of the brain. Long-term potentiation of motor cortex neuron activity in response to simultaneous stimulation of the ventrolateral nucleus and somatosensory cortex arose only in regions receiving corticocortical projections from the stimulation site in the somatosensory cortex of the brain, while regions lacking corticocortical projections from the somatosensory cortex showed no such effect. Experiments demonstrated that the duration of increased motor cortex neuron activity following stimulation of the ventrolateral nucleus of the thalamus and somatosensory cortex was greater than one hour after recording was started. These data led to the conclusion that simultaneous stimulation of corticocortical and thalamocortical afferents can alter the level of neuronal activity in the motor cortex only in regions with convergent sensory inputs from the thalamus and somatosensory cortex of the brain. Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 84, No. 5–6, pp. 460–468, May–June, 1998.     

Canal-neck interaction in vestibular neurons of the cat's cerebral cortex

Summary Interaction of semicircular canal and neck proprioceptive inputs was studied in the cerebral cortex of awake, intact cats. Neuronal responses were recorded extracellularly in the anterior suprasylvian gyrus of the left hemisphere. Stimulations consisted of horizontal rotations in the dark applied as sinusoids or position ramps. There were three stimulus conditions: (1) Pure canal stimulation; rotation of whole body. (2) Pure neck stimulation; rotation of trunk about stationary head. (3) Canalneck interaction; rotation of head about stationary trunk.(1) We recorded 105 neurons with either Type I or Type II canal response. These showed often pronounced non-linearities such as a clear firing increase upon rotation in the on-direction and hardly any decrease in the opposite direction. The responses reflected mostly angular velocity, but angular position signals were also obtained. (2) In 79 neurons, either Type I or Type II neck responses were obtained. They coded either angular velocity, velocity plus position, or position. (3) Canal-neck convergence was found in 67 of 88 neurons tested. In the majority of neurons, interaction was dantagonistic in the sense that the canal and neck responses tended to cancel each other during rotation of the head about the stationary trunk. These neurons could signal trunk rotation in space rather than head in space or head relative to trunk. Most of the remaining neurons showed a synergistic interaction such that the response upon head rotation was enhanced as compared to whole body or trunk rotation. These neurons might be involved in the dual task of monitoring head rotation in space and relative to trunk. Interaction was compatible with linear summation of canal and neck inputs in 70% of the neurons. In part of these, however, the assumption had to be made that the interaction had taken place already at some stage prior to the cortical neurons investigated. The response characteristics of cortical canal neurons are discussed in comparison to vestibular nuclear neurons. Furthermore, parallels are drawn between the observed canal-neck interactions in the cortical neurons and (i) interactions of canal and neck dependent postural reflexes in the decerebrate cat, and (ii) interactions of canal and neck induced turning sensations in man.     

脑缺血大鼠大脑皮质NMDA受体的早期表达

目的　探讨脑缺血和缺血再灌注早期大脑皮质NMDA受体的变化规律。方法　健康雄性SD大鼠 4 8只 ,随机分为 6组 :假手术对照组、单纯脑缺血 1 5min、2 0min和 30min组及脑缺血 1 5min再灌流 30min和 2 4h组 ;4血管脑缺血动物模型 ;连续冰冻冠状切片观察 ,NR1 免疫组化染色特异性地显著NMDA受体的变化 ,图象分析及计算阳性单位PU值。结果　①单纯脑缺血各组PU值分别为 7 5 5± 1 81、6 91± 2 5 3和 6 0 9± 1 5 0 ,与对照组PU值 9 0 4± 1 5 7相比呈下降趋势 (P≤ 0 0 5 ) ;②再灌流 30min和 2 4h组PU值分别为 5 76± 2 2 4和 4 73± 1 34,与对照组PU值相比明显减少 36 2 9%～ 4 7 6 8% ,有统计学意义(P <0 0 5 ) ;③再灌流 0min、30min和 2 4h组两两比较 ,除 2 4h和 0min组相比NR1 阳性反应物减少有统计学意义 (P <0 0 5 )外 ,其它组别间NMDA受体下降的变化无显著性差异 (P >0 0 5 )。结论　脑缺血和缺血再灌流早期NMDA受体都存在下行调节 ,这种调节可能是一种保护性作用     

The effects of acupuncture (PC6) on chronic mild stress-induced memory loss

A previous study reported that the PC6 acupuncture point can alleviate chronic mild stress (CMS)-induced anxiety [17]. Following the previous study, this study examined the effects of the PC6 acupuncture point on CMS-induced memory loss. The memory storage and acetylcholinesterase (AchE) activity in the hippocampus were measured, respectively, using a passive avoidance test (PAT) and AchE immunohistochemistry. In the PAT (retention test), the CMS group showed a markedly lower latency time than the control (post (72h): P<0.01, post (96h): P<0.05, post (120h): P<0.001). However, acupuncture at PC6 significantly recovered the impairment of memory compared to the CMS group (post (120h): P<0.001). Exposure to CMS also significantly decreased the AchE activity in the hippocampus compared to the control rats. Acupuncture stimulation at the PC6 point on the pericardium channels (3min), but not at other points (TE5), produced memory improvements and an increase in AchE reactivity in the hippocampus compared to the CMS group. These results show that the acupuncture point is effective in restoring the CMS-related biochemical and behavioral impairments, such as learning and memory.     

Upregulation of glutamate receptors in rat cerebral cortex with neuronal migration disorders

Neuronal migration disorders (NMDs) constitute the main pathologic substrate of medically intractable epilepsy in human. This study is designed to investigate the changes in expression of glutamate receptor subtypes on radiation-induced NMD in rats. The lesion was produced by intrauterine irradiation (240 cGy) on E17 rats, and then 10 weeks old rats were used for the study. The pathologic and immuno-histochemical findings for glutamate receptor subunit proteins on NMD cortex were correlated with development of behavioral seizures and EEG abnormality. Spontaneous seizures uncommonly occurred in NMD rats (5%); however, clinical stages of seizures were significantly increased in NMD rats by an administration of kainic acid. Brains taken from irradiated rats revealed gross and histopathologic features of NMD. Focal cortical dysplasia was identified by histopathology and immunohistochemistry with neurofilament protein (NF-M/H). Significantly strong NR1 and NR2A/B immunoreactivities were demonstrated in cytomegalic and heterotopic neurons of NMD rats. The results of the present study indicate that epileptogenesis of NMD might be caused by upregulation of glutamate receptor expression in dysplastic neurons of the rat cerebral cortex with NMDs.     

Behavioral and neurobiological studies on the male progeny of maternal rats exposed to chronic unpredictable stress before pregnancy

Studies have shown that maternal chronic stress or depression is linked to an increased risk for affective disorders in progeny. However, the impact of maternal chronic stress before pregnancy on their progeny in animal models has not been well studied. We investigated the behaviors and the neurobiology in 60-day-old male progeny of maternal rats exposed to a 21-day chronic unpredictable stress (CUS) before pregnancy, with male progeny of unstressed maternal rats as the control. Sucrose consumption test showed that both sucrose intake and sucrose consumption percentage of the CUS progeny were lower than those of the control progeny (P < 0.05). The number of times crossing the removed hidden platform in the CUS progeny was significantly fewer than that in the control progeny in Morris water maze test (P < 0.05). The level of 5-hydroxytryptamine (5-HT) in the hypothalamus was reduced but the level of norepinephrine (NE) in the hippocampus was increased in CUS progeny when compared to the control (P < 0.05). Western blotting showed that the relative level of phosphorylated CREB (P-CREB) in the CUS progeny was lower than that in the control progeny (P < 0.05). There were significant positive correlations between sucrose consumption percentage and the level of 5-HT in hypothalamus P < 0.05) or the level of P-CREB in hippocampus (P < 0.05). In conclusion, depression or stressful events before pregnancy was also associated with high risk of depression in progeny, and the down-regulation of P-CREB in the hippocampus might be one of the mechanisms underlying depression in the CUS progeny.     

Lipid peroxidation in the adrenal cortex in exhausting stress

Laboratory of Biochemistry of the Endocrine Glands, Institute of Biochemistry, Academy of Sciences of the Belorussian SSR, Grodno. (Presented by Academician of the Academy of Medical Sciences of the USSR Yu. A. Pankov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 109, No. 5, pp. 430–432, May, 1990.     

Altered aortic vascular reactivity in the unpredictable chronic mild stress model of depression in mice: UCMS causes relaxation impairment to ACh

Major depression is an independent risk factor for the development of cardiovascular disease. This impact of depression on vascular function seems to be mediated by the endothelial dysfunction, defined as an impairment of endothelium-dependent vasorelaxation, which represents a reliable predictor of atherosclerosis and has been regularly found to be associated with depression. This study aimed at investigating aortic vascular reactivity in mice submitted to the unpredictable chronic mild stress (UCMS) procedure, a reliable model of depression. The results confirm the effectiveness of the UCMS procedure to induce neuroendocrine, physical and behavioral depression-like alterations as well as a significant decrease of acetylcholine-induced vasorelaxation without any effect on phenylephrine-induced vasoconstriction. In this study, we reveal an altered vascular reactivity in an animal model of depression, demonstrating an endothelial dysfunction reminiscent to the one found in depressed patients.     

Tyrosine hydroxylase-immunoreactive intrinsic neurons in the rat cerebral cortex

Summary Using specific antisera against the catecholamine synthesizing enzyme, tyrosine hydroxylase (TH), in combination with the peroxidase-antiperoxidase method and/or the avidin-biotin complex method, we have found a new group of TH immunoreactive (TH-I) neurons in the rat cerebral cortex. Numerous TH-I cells were observed all over the isocortex, that is, frontal, temporal, parietal and occipital regions, and in some parts of the allocortex such as the anterior cingulate cortex, the retrosplenial cortex and anterior part of the insular cortex. In contrast, they were rare in the perirhinal cortex, posterior part of the insular cortex, piriform cortex, entorhinal cortex and hippocampal formation. TH-I cells were situated throughout all cortical layers, but were most concentrated in layer II/III. Although TH-I cells were heterogeneous in shape, the majority were bipolar. All TH-I cells so far examined appeared to be of the nonpyramidal type. The majority of these intrinsic TH-I neurons also contained the GABA-like immunoreactivity and thus could be regarded as a subpopulation of cortical GABAergic neurons.     

Alterations in cortical thickness and neuronal density in the frontal cortex of Albert Einstein

Neuronal density, neuron size, and the number of neurons under 1 mm² of cerebral cortical surface area were measured in the right pre-frontal cortex of Albert Einstein and five elderly control subjects. Measurement of neuronal density used the optical dissector technique on celloidin-embedded cresyl violet-stained sections. The neurons counted provided a systematic random sample for the measurement of cell body cross-sectional area. Einstein's cortex did not differ from the control subjects in the number of neurons under 1 mm² of cerebral cortex or in mean neuronal size. Because Einstein's cortex was thinner than the controls he had a greater neuronal density.     

Spatial correlation between sensory regions and the drainage fields of pial veins in rat cerebral cortex

Summary Visual and somatosensory evoked potentials were mapped in the cerebral cortex of adult rats and, after filling the cerebral arteries and veins with dye, the mappings were then compared to the distribution of pial veins. A close relationship was found between the position, size and shape of the occipital venous drainage field and the distribution of visual evoked potentials with high amplitudes and short latencies. Accordingly, such potentials evoked by stimulation of the forepaw and the tailroot were confined to the fronto-parietal drainage field. In the case of individual variations in the expansion and shape of sensory areas, the medial and lateral borders of the occipital drainage field and the medial border of the fronto-parietal drainage field covaried. Only at the common border between these two drainage fields, visual evoked potentials with small amplitudes and long latencies extended into the parietal drainage field and overlapped with somatosensory evoked potentials. This overlapping area corresponds in position to the anterior part of the peristriate cortex. A comparison between the vascular organization and cytoarchitectonic maps of the rat cortex indicates that other parts of the characteristic pattern of venous drainage fields may also correlate with the cytoarchitectonic and functional organization of the cerebral cortex. These observations suggest that during morphogenesis the formation of sensory projections to the cerebral cortex may interact with the angiogenesis, mainly with the development of veins.Fellow of the Alexander von Humboldt Stiftung