Changes In Neuronal Morphology Research Articles

EARLY STRUCTURAL AND BEHAVIOURAL DIFFERENCES IN APPSWE/PS1ΔE9 MOUSE MODEL OF ALZHEIMER’S DISEASE

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by decline in cognitive functions, including memory impairment. We examined structural changes in neuronal morphology in CA1 region of the hippocampus in APPSwe/PS1ΔE9 (APP/PS1) mice. We further evaluated these structural changes with hippocampal dependent learning tasks. Golgi staining - Brains from 1 month old APP/PS1 mice (wild-type and transgenic) were fixed for Golgi staining and 100 μm serial sections were cut for spine and morphometric analyses. Novel-object recognition (NOR), Object-place recognition (OPR), Object-in-context recognition (OCR) were used to study different aspects of episodic memory. For analysis, the test phase in all the three tasks were converted into a discrimination ratio. The Morris water maze (MWM) - The mouse is trained to navigate a pool with opaque water and find the hidden platform. The reversal phase started on day 6, at which point the platform was moved to the opposite quadrant of the tank. Results at the probe trial represented spatial memory. Contextual fear conditioning (cFC) – It involves pairing of a conditioned stimulus with an aversive unconditioned stimulus (footshock). As a result of these pairings, animals freeze to the neutral stimulus such as the training context (CS) upon subsequent presentations. Apical dendritic spine loss, including reduction in mushroom spine density is seen as early as 1 month of age in CA1 region of the hippocampus of APP/PS1 mice. Significant deficits were observed upon hippocampal dependent episodic-like memory task requiring the binding of an object memory into a spatial context such as OCR and OPR. No difference was seen in NOR, which unlike the other components of episodic-like memory is considered not to critically rely on the hippocampus. In MWM, mice showed no difference in acquisition but had less preference for the target quadrant compared to the wildtype upon reversal learning. APP/PS1 mice also showed contextual fear learning deficits. Our study demonstrates that AD-relevant pathological changes affecting structural and behavioral features start early and progress with increasing age in APP/PS1 mice.

Molecular mechanisms of neuroinflammation initiation and development in a model of post-traumatic stress disorder

Neuroinflammation causes morphological and functional changes in the nervous tissue and it can be triggered by different kind of stressors. Progress of neuroinflammation as a result of post-traumatic stress disorder (PTSD) is associated with morphological changes in neurons and glial cells, as well as activation of microglia, however the exact molecular mechanisms of these changes are still unknown. In this review we discuss the connections between endocrine, immune and limbic systems during stress, the contributions of each system, the role of blood-brain barrier, as well as current methods and approaches in studying neuroinflammation.

Sustained Activation of JNK Induced by Quinolinic Acid Alters the BDNF/TrkB Axis in the Rat Striatum

Oxidative stress secondary to excitotoxicity is a common factor in the physiopathology of a variety of neurological disorders. In response to oxidative stress, several signaling pathways, such as MAPK, are activated or inactivated. Mitogen-activated protein kinase (MAPK) family activation must be finely regulated in time and intensity, as this pathway may either preserve cell survival or promote cell death. In the present study, the activation of MAPK in the excitotoxic injury induced by quinolinic acid (QUIN) was examined in vivo, at short and long times. We used different doses (30, 60, 120 and 240 nmol) of QUIN injected intrastriatally in the right rat striatum and the effect of this treatment on motor deficits, cellular damage, MAPK activation and BDNF/TrkB axis, were evaluated at 2 h and 7 days post-lesion. Higher doses of QUIN (120 and 240 nmol) induced rat motor deficits and caused morphological changes in neurons around the lesion core. QUIN decreased the activation of ERK1/2 in a dose-dependent manner at 7 days post-injection, and induced a sustained increase of c-Jun NH2-terminal kinase (JNK) activation from 2 h to 7 days post-injury. JNK activation was dependent on the QUIN-induced NMDAr activation (only 120 nmol). No significant difference in p38 activation with QUIN was observed. QUIN (120 and 240 nmol) decreased BDNF/TrkB levels at 7 days post-injury. JNK inhibition (by an intracerebroventricular injection of SP600125) prevented the QUIN-induced reduction in BDNF and TrkB at 7 day post-injury, suggesting a role for the QUIN-induced JNK activation on the observed decrease in BDNF levels.

Circadian Plasticity in the Brain of Insects and Rodents

In both vertebrate and invertebrate brains, neurons, glial cells and synapses are plastic, which means that the physiology and structure of these components are modified in response to internal and external stimuli during development and in mature brains. The term plasticity has been introduced in the last century to describe experience-dependent changes in synapse strength and number. These changes result from local functional and morphological synapse modifications; however, these modifications also occur more commonly in pre- and postsynaptic neurons. As a result, neuron morphology and neuronal networks are constantly modified during the life of animals and humans in response to different stimuli. Nevertheless, it has been discovered in flies and mammals that the number of synapses and size and shape of neurons also oscillate during the day. In most cases, these rhythms are circadian since they are generated by endogenous circadian clocks; however, some rhythmic changes in neuron morphology and synapse number and structure are controlled directly by environmental cues or by both external cues and circadian clocks. When the circadian clock is involved in generating cyclic changes in the nervous system, this type of plasticity is called circadian plasticity. It seems to be important in processing sensory information, in learning and in memory. Disruption of the clock may affect major brain functions.

Gastrodin Attenuates Bilateral Common Carotid Artery Occlusion-Induced Cognitive Deficits via Regulating Aβ-Related Proteins and Reducing Autophagy and Apoptosis in Rats.

Gastrodin (GAS), an active constituent extracted from Gastrodia elata Blume, is used to treat ischemic stroke, epilepsy, dizziness, and dementia for centuries in China. This study examined its effects on vascular dementia (VD) and the underlying molecular mechanisms. VD was established by ligation of bilateral common carotid artery occlusion (BCCAO). A total of 7 days after BCCAO surgery, GAS (15, 30, and 60 mg/kg) was orally administered for 28 consecutive days to evaluate therapeutic effects. Cognitive function was tested by the Morris water maze. The neuronal morphological changes were examined via Hematoxylin–Eosin staining. Flow cytometry was used for evaluating apoptosis in the hippocampi. The target protein expression was examined by Western blot. The results showed that BCCAO induced cognitive impairment, hippocampus CA1 and CA3 pyramidal neuron damage, beta-amyloid (Aβ) deposition, excessive autophagy, and apoptosis. GAS treatment significantly improved BCCAO-induced cognitive deficits and hippocampus neuron damage. Molecular analysis revealed that GAS exerted the protective effect via reducing the levels of Aβ1–40/42, APP, and β-site APP-cleaving enzyme 1 expression, and increasing Aβ-related protein, a disintegrin and metalloprotease 10, and insulin degrading enzyme expression. Meanwhile, GAS inhibited excessive autophagy via decreasing Beclin-1, LC3-II, and p62 levels. Furthermore, GAS inhibited apoptosis through the downregulation of Bax and upregulation of Bcl-2. Moreover, P38 MAPK signaling pathway was involved in the process. Our findings demonstrate that GAS was effective in the treatment of BCCAO-induced VD via targeting Aβ-related protein formation and inhibiting autophagy and apoptosis of hippocampus neurons.

Profound seasonal changes in brain size and architecture in the common shrew

The seasonal changes in brain size of some shrews represent the most drastic reversible transformation in the mammalian central nervous system known to date. Brain mass decreases 10–26% from summer to winter and regrows 9–16% in spring, but the underlying structural changes at the cellular level are not yet understood. Here, we describe the volumetric differences in brain structures between seasons and sexes of the common shrew (Sorex araneus) in detail, confirming that changes in different brain regions vary in the magnitude of change. Notably, shrews show a decrease in hypothalamus, thalamus, and hippocampal volume and later regrowth in spring, whereas neocortex and striatum volumes decrease in winter and do not recover in size. For some regions, males and females showed different patterns of seasonal change from each other. We also analyzed the underlying changes in neuron morphology. We observed a general decrease in soma size and total dendrite volume in the caudoputamen and anterior cingulate cortex. This neuronal retraction may partially explain the overall tissue shrinkage in winter. While not sufficient to explain the entire seasonal process, it represents a first step toward understanding the mechanisms beneath this remarkable phenomenon.

Lowbush cranberry acts through DAF-16/FOXO signaling to promote increased lifespan and axon branching in aging posterior touch receptor neurons.

Medicinal berries are appreciated for their health benefits, in traditional ecological knowledge and nutrition science. Determining the cellular mechanisms underlying the effects of berry supplementation may contribute to our understanding of aging. Here, we report that lowbush cranberry (Vaccinium vitis-idaea) treatment causes marked nuclear localization of the central aging-related transcription factor DAF-16/FOXO in aged Caenorhabditis elegans. Further, functional DAF-16 is required for the lifespan extension, improved mechanosensation, and posterior touch receptor neuron morphological changes induced by lowbush cranberry treatments. DAF-16 is not observed in nuceli nor required for lifespan extension in lifespan-extending Alaskan blueberry treatments and, while DAF-16 is not visibly induced into the nucleus in lifespan-extending Alaskan chaga treatments, it is required for chaga-induced lifespan extension. These findings underscore the importance of DAF-16 in the aging of whole organisms and touch receptor neurons and also, importantly, indicate that this critical pathway is not always activated upon consumption of functional foods that impact aging.

Electroacupuncture plus Gastrodin Improves Learning-memory Ability Possibly by Up-regulating Expression of SIRT 1 and PGC-1 ɑ in Hippocampal CA 1 Region of Alzheimer's Disease Rats

To observe the effect of electroacupuncture (EA) combined with Gastrodin on learning-memory ability and expression of silent information regulator 2 homologous protein 1(SIRT 1) and peroxisome proliferator activated receptor γ coactivator (PGC-1 ɑ) of hippocampal CA 1 region in Alzheimer's disease(AD) rats, so as to explore its mechanism under-lying improvement of AD. Sixty male SD rats were randomly divided into normal control (normal), sham operation (sham), model, EA, Gastrodin and EA＋ Gastrodin groups (n＝10 in each). The AD model was established by intraperitoneal injection of D-Galactose (120 mg•kg－1•d－1) combined with bilateral hippocampal injection of β amyloid 1-40(Aβ 1-40). EA was applied at "Baihui"(GV 20), "Dazhui"(GV 14) and "Zusanli"(ST 36) for 30 min, once daily for 4 weeks. For rats of the Gastro-din group and EA＋ Gastrodin group, intraperitoneal injection of gastrodin(10 mg/kg) was conducted once daily for 4 weeks. Morris water maze tests were used to assess the rat's learning-memory ability. Nissl staining was used to assess the morphological changes of neurons in the hippocampal CA 1 area. The expression of SIRT 1 and PGC-1 ɑ of hippocampal CA 1 region was mea-sured by immunohistochemical staining. 1) Morris water maze tests showed that, compared with the normal and sham group, the escape latency was significantly prolonged (P<0.05), and the percentage of platform quadrant residence duration and the platform crossing times were considerably decreased in the model group (P<0.05). After the intervention, the escape latency was obviously shortened (P<0.05), and the percentage of platform quadrant residence duration and the platform crossing times were markedly increased in the EA, Gastrodin and EA＋Gastrodin groups relevant to the model group (P<0.05). 2) Nissl staining showed that, in comparison with the normal group or sham group, the number of cells in the hippocampal CA 1 area was decreased and the arrangement was disorganized in the model group. The number of cells in CA 1 area was relatively higher in the 3 treatment groups than in the model group. 3) The expression levels of SIRT 1 and PGC-1 ɑ proteins in the hippocampal CA 1 area were significantly down-regulated in the model group than in the normal and sham groups (P<0.05). After the intervention, the expression levels of SIRT 1 and PGC-1 ɑ in the EA, Gastrodin and EA＋Gastrodin groups were significantly up-regulated compared with the model group (P<0.05). The effects of EA＋Gastrodin were significantly superior to those of simple EA and simple Gastrodin in shortening the escape latency, up-regulating the expression levels of SIRT 1 and PGC-1 ɑ as well as in increasing the percentage of platform quadrant residence time and platform crossing times (P<0.05). Both EA and Gastrodin can improve the learning-memory ability of AD rats, which may be related to their effects in up-regulating the expression of SIRT 1 and PGC-1 ɑ and reducing neuronal injury in the CA 1 region of hippocampus, suggesting a protective role of EA on hippocampal neurons. The effect of EA combined with Gastrodin is markedly better than that of EA and Gastrodin alone.

Toxoplasmic Infection-induced Injury in the Ileal Myenteric Plexus in Rats Depends on the Dose of Toxoplasma gondii Oocysts

Introduction The present study evaluated the effects of different inocula of Toxoplasma gondii oocysts on the ileal myenteric plexus in rats. Materials and Methods Male Wistar rats, 60 days old, were distributed into four groups: control group (CG; which received saline solution) and groups that were infected with 100 (TG100), 1000 (TG1000), and 5000 (TG5000) T. gondii oocysts. Thirty days after infection, the rats were sacrificed, and the ileum was collected to make whole-mount preparations that were subjected to immunofluorescence staining to observe the general neuronal population (HuC/D), nitrergic neurons (nNOS), and enteric glial cells (S100). Morphometric and quantitative analyses of myenteric neurons were performed. Results The infections with different T. gondii inocula did not cause neuronal or glial loss, but cause neuronal hypertrophy in general population and nitrergic subpopulation in infected groups. Conclusion: Changes in neuronal morphology were observed in the TG5000 group, including the presence of vacuoles, translocation of Hu protein to the nucleus, and dendritic distortions, suggesting functional alterations in these cells.

Deletion of Tsc2 in Nociceptors Reduces Target Innervation, Ion Channel Expression, and Sensitivity to Heat.

The mechanistic target of rapamycin complex 1 (mTORC1) is known to regulate cellular growth pathways, and its genetic activation is sufficient to enhance regenerative axon growth following injury to the central or peripheral nervous systems. However, excess mTORC1 activation may promote innervation defects, and mTORC1 activity mediates injury-induced hypersensitivity, reducing enthusiasm for the pathway as a therapeutic target. While mTORC1 activity is required for full expression of some pain modalities, the effects of pathway activation on nociceptor phenotypes and sensory behaviors are currently unknown. To address this, we genetically activated mTORC1 in mouse peripheral sensory neurons by conditional deletion of its negative regulator Tuberous Sclerosis Complex 2 (Tsc2). Consistent with the well-known role of mTORC1 in regulating cell size, soma size and axon diameter of C-nociceptors were increased in Tsc2-deleted mice. Glabrous skin and spinal cord innervation by C-fiber neurons were also disrupted. Transcriptional profiling of nociceptors enriched by fluorescence-associated cell sorting (FACS) revealed downregulation of multiple classes of ion channels as well as reduced expression of markers for peptidergic nociceptors in Tsc2-deleted mice. In addition to these changes in innervation and gene expression, Tsc2-deleted mice exhibited reduced noxious heat sensitivity and decreased injury-induced cold hypersensitivity, but normal baseline sensitivity to cold and mechanical stimuli. Together, these data show that excess mTORC1 activity in sensory neurons produces changes in gene expression, neuron morphology and sensory behavior.

Intracerebroventricular administration of growth hormone induces morphological changes in pyramidal neurons of the hippocampus and prefrontal cortex in adult rats.

A growing body of evidence suggests that growth hormone (GH) affects synaptic plasticity at both the molecular and electrophysiological levels. However, unclear is whether plasticity that is stimulated by GH is associated with changes in neuron structure. This study investigated the effect of intracerebroventricular (ICV) administration of GH on the morphology of pyramidal neurons of the CA1 region of the dorsal hippocampus and layer III of the prefrontal cortex. Male Wistar rats received daily ICV injections of GH (120 ng) for 7 days, and they were euthanized 21 days later. Changes in neuronal morphology were evaluated using Golgi-Cox staining and subsequent Sholl analysis. GH administration increased total dendritic length in the CA1 region of the dorsal hippocampus and prefrontal cortex. The Sholl analysis revealed an increase in dendritic length of the third to eighth branch orders in the hippocampus and from the third to sixth branch orders in the prefrontal cortex. Interestingly, GH treatment increased the density of dendritic spines in both brain regions, favoring the presence of mushroom-like spines only in the CA1 hippocampal region. Our results indicated that GH induces changes in the length of dendritic trees and the density of dendritic spines in two high-plasticity brain regions, suggesting that GH-induced synaptic plasticity at the molecular and electrophysiological levels may be associated with these structural changes in neurons.

Biophysics Model of Heavy-Ion Degradation of Neuron Morphology in Mouse Hippocampal Granular Cell Layer Neurons.

Exposure to heavy-ion radiation during cancer treatment or space travel may cause cognitive detriments that have been associated with changes in neuron morphology and plasticity. Observations in mice of reduced neuronal dendritic complexity have revealed a dependence on radiation quality and absorbed dose, suggesting that microscopic energy deposition plays an important role. In this work we used morphological data for mouse dentate granular cell layer (GCL) neurons and a stochastic model of particle track structure and microscopic energy deposition (ED) to develop a predictive model of high-charge and energy (HZE) particle-induced morphological changes to the complex structures of dendritic arbors. We represented dendrites as cylindrical segments of varying diameter with unit aspect ratios, and developed a fast sampling method to consider the stochastic distribution of ED by δ rays (secondary electrons) around the path of heavy ions, to reduce computational times. We introduce probabilistic models with a small number of parameters to describe the induction of precursor lesions that precede dendritic snipping, denoted as snip sites. Predictions for oxygen (16O, 600 MeV/n) and titanium (48Ti, 600 MeV/n) particles with LET of 16.3 and 129 keV/μm, respectively, are considered. Morphometric parameters to quantify changes in neuron morphology are described, including reduction in total dendritic length, number of branch points and branch numbers. Sholl analysis is applied for single neurons to elucidate dose-dependent reductions in dendritic complexity. We predict important differences in measurements from imaging of tissues from brain slices with single neuron cell observations due to the role of neuron death through both soma apoptosis and excessive dendritic length reduction. To further elucidate the role of track structure, random segment excision (snips) models are introduced and a sensitivity study of the effects of the modes of neuron death in predictions of morphometric parameters is described. An important conclusion of this study is that δ rays play a major role in neuron morphological changes due to the large spatial distribution of damage sites, which results in a reduced dependence on LET, including modest difference between 16O and 48Ti, compared to damages resulting from ED in localized damage sites.

Puerarin Up-regulates Methyl-CpG Binding Protein 2 Phosphorylation in Hippocampus of Vascular Dementia Rats.

To observe the effect of puerarin on methyl-CpG binding protein 2 (MeCP2) phosphorylation (pMeCP2) in the hippocampus of a rat model of vascular dementia (VD). Thirty-six healthy Sprague-Dawley rats were randomly assigned to the sham-operated group, dementia group and puerarintreated group using a random number table (n=12 per group). The modifified permanent bilateral common carotid artery occlusion method was used to establish the VD model. The sham-operated and dementia groups were given 2 mL/d of saline, while the puerarin-treated group was given 100 mg/(kg•d) of puerarin for 17 days. The learning and memory abilities were evaluated by the Morris water maze test. Hematoxylin-eosin staining, immunohistochemical (IHC) staining and Western blot analysis were carried out to observe changes in neuron morphology and in level of pMeCP2 in the hippocampus, respectively. The morphologies of rat hippocampal neurons in the puerarintreated group were markedly improved compared with the dementia group. The escape latency of the dementia group was significantly longer than the sham-operated group (P<0.05), while the puerarin-treated group was obviously shorter than the dementia group (P<0.05). Cross-platform times of the dementia group were signifificantly decreased compared with the sham-operated group (P<0.05), while the puerarin-treated group was obviously increased compared with the dementia group (P<0.05). IHC staining showed no significant difference in the number of MeCP2 positive cells among 3 groups (P>0.05). The number of pMeCP2 positive cells in the CA1 region of hippocampus in the dementia group was signifificantly increased compared with the sham-operated group, and the puerarin-treated group was signifificantly increased compared with the dementia group (both P<0.05). Western blot analysis showed no signifificant difference of MeCP2 expression among 3 groups (P>0.05). The expression of pMeCP2 in the dementia group was signifificantly increased compared with the sham-operated group, while it in the puerarin-treated group was signifificantly increased compared with the dementia group (P<0.05). Puerarin could play a role in the protection of nerve cells through up-regulating pMeCP2 in the hippocampus, improving neuron morphologies, and enhancing learning and memory ablities in a rat model of VD.

The Brain Cells on the Carbon Nanotubes: Morphological and Functional Changes in Neurons and Glia

Carbon Nanotubes (CNT) are promising material for research and medical application. Because of the electrochemical nature of CNT, it is considered as a potentially effective nanomaterial in neuroscience. By the way, properties of these CNT are dependent on how they are synthesized or which functional groups they have. As the nature of CNT varies, the effect on brain cells can have different features from cell to cell. Also, the diversity should be concerned to not only neurons also glia in the brain. Therefore, we focus on studies for understanding the functional and morphological changes of neurons and glia in the effects of CNT.

Roles of the dopaminergic system in the medial prefrontal cortex for stress resilience and its relevance to stress-induced changes in neuronal morphology

Roles of the dopaminergic system in the medial prefrontal cortex for stress resilience and its relevance to stress-induced changes in neuronal morphology

The protective effect of the activation of NMDAR1/ERK1/2 signal pathway induced by levodopa on visual cortical neurons in monocular deprivation rats

Objective: To investigate the protection effects of the activation of NMDAR1(NMDA receptor 1)/ERK1/2 signal pathway on visual cortex nerve cells induced by levodopa in amblyopia rats. Methods: SD rats of SPF grade, were randomly divided into for groups of 9, group A. Control, B. MD group, C. L-levodopa(20 mg·kg(-1))+MD group, D. H-levodopa (80 mg·kg(-1))+MD group, E. H-levodopa+MD+MK801 group, F. H-levodopa+MD+PD98059 group, G. MD+MK801 group, H. MD+PD98059 group, I. MD+DMSO group. Amblyopia rats were made by suture of the right eye. Levodopa was used to treatment amblyopia by gavage, and intervened by intracerebroventricular injection of MK801 and PD98059 respectively. The expression of NR1, p-ERK1/2, ERK1/2, NGF and c-FOS were detected by Western blotting. Nissl staining was used to detect morphological changes of neurons. Neuronal apoptosis was detected by TUNEL method, and detected the expression of Caspase-3, NGF and c-FOS by immunohistochemical staining. One/Two way Chi-square analysis was used for data analysis. LSD-t test was used as comparison between every two groups. Results: The morphology of Nissl bodies in neurons was complete and clear in A group, and the size of Nissl bodies got smaller, and caused karyopyknosis and loss of neurons in visual cortex of B group. Compared with A group, the apoptosis of visual cortical neurons(23.09±2.00 vs. 2.20±0.35, t=12.120, P=0.000) and the number of Caspase-3 postive cells (22.70±1.50 vs. 3.30±0.54, t=12.120, P=0.000)were significantly increased, the expression of NGF(0.31±0.04 vs. 0.74±0.09, t=7.674, P=0.000) and c-FOS(0.25±0.03 vs. 0.57±0.07, t=5.919, P=0.000) and the rats of NGF(8.30±0.82 vs. 35.18±2.01, t=12.37, P=0.0000) and c-FOS (10.84±1.02 vs. 35.68±2.55, t=9.056, P=0.0001) postive cell were decreased significantly in B group. After treatment with levodopa, the morphology of neurons recovered, the apoptosis of visual cortical neurons relieved, the expression of NR1(0.75±0.09 vs. 0.40±0.05, t=8.528, P=0.001) and p-ERK1/2(2.13±0.26 vs. 0.68±0.17, t=3.488, P=0.008) were increased significantly, and the rats of NGF (18.07±0.87 vs. 8.30±0.82, t=8.18, P=0.0000) and c-FOS (19.78±0.91 vs. 10.84±1.02, t=6.543, P=0.0001) postive cells were significantly increased. MK-801 or PD98059 intervention could effectively attenuate the effect of levodopa. It could effectively down-regulated the expression of NR1 (0.53±0.06 vs. 0.95±0.12, t=5.647, P=0.005) and p-ERK1/2(1.52±0.18 vs. 2.58±0.30, t=3.091, P=0.013) interference with MK801 or PD98059 in MD rats. MK-801 or PD98059 intervention further promote the Nissl body volume reduced, neurons karyopyknosis, the apoptosis of visual cortical neurons and Caspase-3 expression, and restrain the expression of NGF and c-FOS. Conclusion: Levodopa played a protective role in visual cortex nerve cells of amblyopia rats at least partially through activation of NMDA-ERK1/2 signal pathway. (Chin J Ophthalmol, 2017, 53: 931-940).

Neuronal Cell Morphology in Primary Cerebellar Granule Cells Using High-Content Analysis.

Neurite outgrowth, one of the underlying cellular processes that defines the development and functionality of the mammalian nervous system, is also a sensitive indicator of neuronal cell health. From screening libraries of putative neurotherapeutic compounds to analyzing the millions of environmental pollutants for which we have inadequate neurotoxicity safety data, the large volume of chemical compounds that require evaluation is a major obstacle for manual imaging and analysis methods. In this context, high-content analysis (HCA) has emerged as a sensitive and accurate method for detecting changes in neuronal cell morphology within a format applicable to screening large chemical libraries. Advances in HCA technologies have enabled the automated imaging and quantitative analysis of neurite outgrowth morphology within a 96-well plate in less than 5 min. Traditionally, neurite outgrowth assessment has been conducted on immortalized cell lines such as pheochromocytoma (PC-12) cells that differentiate into neuron-like cells upon culture with nerve growth factor. Unfortunately, they do not retain all the in vivo characteristics of physiological neuronal tissue, including lack of synapse formation. As researchers refine neurite outgrowth quantitative analysis using HCA, an emerging question is how to quantify this biology in more complex models that more faithfully recapitulate in vivo environments. Primary neurons provide several benefits relative to neuronal cell lines, including the elaboration of axons from secondary dendrites and formation of both pre- and postsynaptic junctions. This chapter reviews techniques for evaluating neurite outgrowth using the ArrayScan HCA platform within a model system of primary cultures of rodent cerebellar granule cells.

Pharmacologic activation of cholinergic alpha7 nicotinic receptors mitigates depressive-like behavior in a mouse model of chronic stress

BackgroundIt has been shown that chronic stress-induced depression is associated with exaggerated inflammatory response in the brain. Alpha7 nicotinic acetylcholine receptors (α7nAChRs) regulate the cholinergic anti-inflammatory pathway, but the role of cholinergic signaling and α7nAChR in chronic stress has not yet been examined.MethodsIn this study, we used a well-documented model of depression in which mice were exposed to 6 h of restraint stress for 21 consecutive days. Components of cholinergic signaling and TLR4 signaling were analyzed in the hippocampus. The main targets of neuroinflammation and neuronal damage were also evaluated after a series of tests for depression-like behavior.ResultsChronic restraint stress (CRS) induced alterations in components of central cholinergic signaling in hippocampus, including increases in choline acetyltransferase protein expression and decreases in nuclear STAT3 signaling. CRS also increased TLR4 signaling activity, interleukin-1β, and tumor necrosis factor-α expression, microglial activation, and neuronal morphologic changes. Cholinergic stimulation with the α7nAChR agonist DMXBA significantly alleviated CRS-induced depressive-like behavior, neuroinflammation, and neuronal damage, but these effects were abolished by the selective α7nAChR antagonist α-bungarotoxin. Furthermore, activation of α7nAChRs restored the central cholinergic signaling function, inhibited TLR4-mediated inflammatory signaling and microglial activity, and increased the number of regulatory T cells in the hippocampus.ConclusionsThese findings provide evidence that α7nAChR activation mitigates CRS-induced neuroinflammation and cell death, suggesting that α7nAChRs could be a new therapeutic target for the prevention and treatment of depression.

Physiological significance of multipolar cells generated from neural stem cells and progenitors for the establishment of neocortical cytoarchitecture.

Neurogenesis encompasses an entire set of events that leads to the generation of newborn neurons from neural stem cells and more committed progenitor cells, including cell division, the production of migratory precursors and their progeny, differentiation and integration into circuits. In particular, the precise control of neuronal migration and morphological changes is essential for the development of the neocortex. Postmitotic cells within the intermediate zone have been found to transiently assume a characteristic "multipolar" morphology, after which a multipolar-to-bipolar transition occurs before the cells enter the cortical plate; however, the importance of this multipolar phase in the establishment of mature cortical cytoarchitecture and the precise genetic control of this phase remains largely unknown. Thus, this review article focuses on the multipolar phase in the developing neocortex. It begins by summarizing the molecular mechanism that underlies multipolar migration for the regulation of each step in multipolar phase in intermediate zone. The physiological significance of this multipolar phase in the establishment of mature cortical lamination and neurodevelopmental disorders associated with migration defects is then described.

Functional characterisation of filamentous actin probe expression in neuronal cells.

Genetically encoded filamentous actin probes, Lifeact, Utrophin and F-tractin, are used as tools to label the actin cytoskeleton. Recent evidence in several different cell types indicates that these probes can cause changes in filamentous actin dynamics, altering cell morphology and function. Although these probes are commonly used to visualise actin dynamics in neurons, their effects on axonal and dendritic morphology has not been systematically characterised. In this study, we quantitatively analysed the effect of Lifeact, Utrophin and F-tractin on neuronal morphogenesis in primary hippocampal neurons. Our data show that the expression of actin-tracking probes significantly impacts on axonal and dendrite growth these neurons. Lifeact-GFP expression, under the control of a pBABE promoter, caused a significant decrease in total axon length, while another Lifeact-GFP expression, under the control of a CAG promoter, decreased the length and complexity of dendritic trees. Utr261-EGFP resulted in increased dendritic branching but Utr230-EGFP only accumulated in cell soma, without labelling any neurites. Lifeact-7-mEGFP and F-tractin-EGFP in a pEGFP-C1 vector, under the control of a CMV promoter, caused only minor changes in neuronal morphology as detected by Sholl analysis. The results of this study demonstrate the effects that filamentous actin tracking probes can have on the axonal and dendritic compartments of neuronal cells and emphasise the care that must be taken when interpreting data from experiments using these probes.