Changes in the Neuronal Architecture of the Hippocampus in a 6-Hydroxydopamine-Lesioned Rat Model of Parkinson Disease

PURPOSE

Parkinson disease (PD) is a progressive neurodegenerative disorder in which dopaminergic (DAergic) systems are destroyed (particularly in the nigrostriatal system), causing both motor and nonmotor symptoms. Hippocampal neuroplasticity is altered in PD animal models, resulting in nonmotor dysfunctions. However, little is known about the precise mechanism underlying the hippocampal dysfunctions in PD.

METHODS

Striatal 6-hydroxydopamine (6-OHDA) infusions were performed unilaterally in adult Sprague Dawley rats. Both motor and nonmotor symptoms alongside the expression of tyrosine hydroxylase (TH) in the substantia nigra and striatum were confirmed in 6-OHDA-lesioned rats. The neuronal architecture in the hippocampus was analyzed by Golgi staining.

RESULTS

During the 7-8 weeks after infusion, the 6-OHDA-lesioned rats exhibited motor and nonmotor dysfunctions (especially anxiety/depression-like behaviors). Rats with unilateral 6-OHDA infusion displayed reduced TH+ immunoreactivity in the ipsilateral nigrostriatal pathway of the brain. Golgi staining revealed that striatal 6-OHDA infusion significantly decreased the dendritic complexity (i.e., number of crossing dendrites, total dendritic length, and branch points) in the ipsilateral hippocampal conus ammonis 1 (CA1) apical/basal and dentate gyrus (DG) subregions. Additionally, the dendritic spine density and morphology were significantly altered in the CA1 apical/basal and DG subregions following striatal 6-OHDA infusion. However, alteration of microglial and astrocytic distributions did not occur in the hippocampus following striatal 6-OHDA infusion.

CONCLUSION

The present study provides anatomical evidence that the structural plasticity in the hippocampus is altered in the late phase following striatal 6-OHDA infusion in rats, possibly as a result of the prolonged suppression of the DAergic system, and independent of neuroinflammation.

Comparison of Golgi-Cox and Intracellular Loading of Lucifer Yellow for Dendritic Spine Density and Morphology Analysis in the Mouse Brain

Dendritic spines are small protrusions on dendrites that serve as the postsynaptic site of the majority of excitatory synapses. These structures are important for normal synaptic transmission, and alterations in their density and morphology have been documented in various disease states. Over 130 years ago, Ramón y Cajal used Golgi-stained tissue sections to study dendritic morphology. Despite the array of technological advances, including iontophoretic microinjection of Lucifer yellow (LY) fluorescent dye, Golgi staining continues to be one of the most popular approaches to visualize dendritic spines. Here, we compared dendritic spine density and morphology among pyramidal neurons in layers 2/3 of the mouse medial prefrontal cortex (mPFC) and pyramidal neurons in hippocampal CA1 using three-dimensional digital reconstructions of (1) brightfield microscopy z-stacks of Golgi-impregnated dendrites and (2) confocal microscopy z-stacks of LY-filled dendrites. Analysis of spine density revealed that the LY microinjection approach enabled detection of approximately three times as many spines as the Golgi staining approach in both brain regions. Spine volume measurements were larger using Golgi staining compared to LY microinjection in both mPFC and CA1. Spine length was mostly comparable between techniques in both regions. In the mPFC, head diameter was similar for Golgi staining and LY microinjection. However, in CA1, head diameter was approximately 50% smaller on LY-filled dendrites compared to Golgi staining. These results indicate that Golgi staining and LY microinjection yield different spine density and morphology measurements, with Golgi staining failing to detect dendritic spines and overestimating spine size.

Synaptic loss and progression in mice infected with Angiostrongylus cantonensis in the early stage

Background

Angiostrongylus cantonensis is also known as rat lungworm. Infection with this parasite is a zoonosis that can cause eosinophilic meningitis and/or eosinophilic meningoencephalitis in humans and may lead to fatal outcomes in severe cases. In this study, we explored the mechanisms of the impairments in the cognitive functions of mice infected with A. cantonensis.

Methods

In infected mice with different infective intensities at different timepoint postinfection, loss and recovery of cognitive functions such as learning and memory abilities were determined. Neuronal death and damage to synaptic structures were analyzed by Western blotting and IHC in infected mice with different infection intensities at different timepoint postinfection.

Results

The results of behavioral tests, pathological examinations, and Golgi staining showed that nerve damage caused by infection in mice occurred earlier than pathological changes of the brain. BDNF was expressed on 14 day post-infection. Cleaved caspase-3 increased significantly in the late stage of infection. However, IHC on NeuN indicated that no significant changes in the number of neurons were found between the infected and uninfected groups.

Conclusions

The synaptic loss caused by the infection of A. cantonensis provides a possible explanation for the impairment of cognitive functions in mice. The loss of cognitive functions may occur before severe immunological and pathological changes in the infected host.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02436-8.

Knockdown of Astrocytic Monocarboxylate Transporter 4 in the Motor Cortex Leads to Loss of Dendritic Spines and a Deficit in Motor Learning

Monocarboxylate transporters (MCTs) shuttle molecules, including L-lactate, involved in metabolism and cell signaling of the central nervous system. Astrocyte-specific MCT4 is a key component of the astrocyte-neuron lactate shuttle (ANLS) and is important for neuroplasticity and learning of the hippocampus. However, the importance of astrocyte-specific MCT4 in neuroplasticity of the M1 primary motor cortex remains unknown. In this study, we investigated astrocyte-specific MCT4 in motor learning and neuroplasticity of the M1 primary motor cortex using a cell-type specific shRNA knockdown of MCT4. Knockdown of astrocyte-specific MCT4 resulted in impaired motor performance and learning on the accelerating rotarod. In addition, MCT4 knockdown was associated with a reduction of neuronal dendritic spine density and spine width and decreased protein expression of PSD95, Arc, and cFos. Using near-infrared-conjugated 2-deoxyglucose uptake as a surrogate marker for neuronal activity, MCT4 knockdown was also associated with decreased neuronal activity in the M1 primary motor cortex and associated motor regions including the dorsal striatum and ventral thalamus. Our study supports a potential role for astrocyte-specific MCT4 and the ANLS in the neuroplasticity of the M1 primary motor cortex. Targeting MCT4 may serve to enhance neuroplasticity and motor repair in several neurological disorders, including Parkinson's disease and stroke.

A workflow for streamlined acquisition and correlation of serial regions of interest in array tomography

Background

Array tomography (AT) is a high-resolution imaging method to resolve fine details at the organelle level and has the advantage that it can provide 3D volumes to show the tissue context. AT can be carried out in a correlative way, combing light and electron microscopy (LM, EM) techniques. However, the correlation between modalities can be a challenge and delineating specific regions of interest in consecutive sections can be time-consuming. Integrated light and electron microscopes (iLEMs) offer the possibility to provide well-correlated images and may pose an ideal solution for correlative AT. Here, we report a workflow to automate navigation between regions of interest.

Results

We use a targeted approach that allows imaging specific tissue features, like organelles, cell processes, and nuclei at different scales to enable fast, directly correlated in situ AT using an integrated light and electron microscope (iLEM-AT). Our workflow is based on the detection of section boundaries on an initial transmitted light acquisition that serves as a reference space to compensate for changes in shape between sections, and we apply a stepwise refinement of localizations as the magnification increases from LM to EM. With minimal user interaction, this enables autonomous and speedy acquisition of regions containing cells and cellular organelles of interest correlated across different magnifications for LM and EM modalities, providing a more efficient way to obtain 3D images. We provide a proof of concept of our approach and the developed software tools using both Golgi neuronal impregnation staining and fluorescently labeled protein condensates in cells.

Conclusions

Our method facilitates tracing and reconstructing cellular structures over multiple sections, is targeted at high resolution ILEMs, and can be integrated into existing devices, both commercial and custom-built systems.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01072-7.

Acute MPTP Treatment Impairs Dendritic Spine Density in the Mouse Hippocampus

Among the animal models of Parkinson’s disease (PD), the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mouse model has shown both dopaminergic (DA) damage and related motor control defects, as observed in patients with PD. Recent studies have suggested that the DA system interacts with the synaptic plasticity of the hippocampus in PD. However, little is known about how alterations in the hippocampal structural plasticity are affected by the DA damage in MPTP-lesioned models. In the present study, we investigated alterations in dendritic complexity and spine density in the mouse hippocampus following acute MPTP treatment (22 mg/kg, intraperitoneally, four times/day, 2-h intervals). We confirmed that acute MPTP treatment significantly decreased initial motor function and persistently reduced the number of tyrosine hydroxylase-positive DA neurons in the substantia nigra. Golgi staining showed that acute MPTP treatment significantly reduced the spine density of neuronal dendrites in the cornu ammonis 1 (CA1) apical/basal and dentate gyrus (DG) subregions of the mouse hippocampus at 8 and 16 days after treatment, although it did not affect dendritic complexity (e.g., number of crossing dendrites, total dendritic length, and branch points per neuron) in both CA1 and DG subregions at all time points after treatment. Therefore, the present study provides anatomical evidence that acute MPTP treatment affects synaptic structure in the hippocampus during the late phase after acute MPTP treatment in mice, independent of any changes in the dendritic arborization of hippocampal neurons. These findings offer data for the ability of the acute MPTP-lesioned mouse model to replicate the non-nigrostriatal lesions of clinical PD.

Treadmill Exercise Reverses the Change of Dendritic Morphology and Activates BNDF-mTOR Signaling Pathway in the Hippocampus and Cerebral Cortex of Ovariectomized Mice

A decline of estrogen level leads to spatial learning and memory impairments, which mediated by hippocampus and cortex. Accumulating evidences demonstrated that aerobic exercise improved memory of postmenopausal women and ovariectomized (OVX) mice. However, the molecular mechanisms for this protection of exercise are not completely clear. Accordingly, the present study was designed to examine the effect of aerobic exercise on the dendritic morphology in the hippocampus and cerebral cortex, as well as the BNDF-mTOR signaling pathway of OVX mice. Adult female C57BL/6 mice were divided into four groups (n = 10/group): sham-operated (SHAM/CON), sham-operated with 8-week treadmill exercise (SHAM/EX), ovariectomized operated (OVX/CON), and ovariectomized operated with exercise (OVX/EX). Aerobic exercise improved the impairment of dendritic morphology significantly induced by OVX that was tested by Golgi staining, and it also upregulated the synaptic plasticity-related protein expression of PSD95 and GluR1 as well as activated BDNF-mTOR signaling pathway in the hippocampus and cerebral cortex. In conclusion, aerobic exercise reversed the change of dendritic morphology and increased the synaptic plasticity-related protein expression in the hippocampus and cerebral cortex of OVX mice. The positive effects induced by exercise might be mediated through the BDNF-mTOR signaling pathway.

The effect of aging and chronic microglia activation on the morphology and numbers of the cerebellar Purkinje cells

Reduced cerebellar volume and motor dysfunction have previously been observed in the GFAP-IL6 murine model of chronic neuroinflammation. This study aims to extend these findings by investigating the effect of microglial activation and ageing on the total number of Purkinje cells and the morphology of their dendritic arborization. Through comparison of transgenic GFAP-IL6 mice and their wild-type counterparts at the ages of 12 and 24-months, we were able to investigate the effects of ageing and chronic microglial activation on Purkinje cells. Unbiased stereology was used to estimate the number of microglia in Iba1⁺ stained tissue and Purkinje cells in calbindin stained tissue. Morphological analyses were made using 3D reconstructions of images acquired from the Golgi-stained cerebellar tissue. We found that the total number of microglia increased by approximately 5 times in the cerebellum of GFAP-IL6 mice compared to their WT littermates. The number of Purkinje cells decreased by as much as 50 % in aged wild type mice and 83 % in aged GFAP-IL6 mice. The remaining Purkinje cells in these cohorts were found to have significant reductions in their total dendritic length and number of branching points, indicating how the complexity of the Purkinje cell dendritic arbor reduces through age and inflammation. GFAP-IL6 mice, when compared to WT mice, had higher levels of microglial activation and more profound neurodegenerative changes in the cerebellum. The presence of constitutive IL6 production, driving chronic neuroinflammation, may account for these neurodegenerative changes in GFAP-IL6 mice.

LRP4 LDLα repeats of astrocyte enhance dendrite arborization of the neuron

The low-density lipoprotein receptor-related protein 4 (LRP4) is essential for inducing the neuromuscular junction (NMJ) formation in muscle fibers, and LRP4 plays a critical role in dendritic development and synaptogenesis in the central nervous system (CNS). As a single transmembrane protein, LRP4 contains an enormously sizeable extracellular domain (ECD), containing multiple LDLα repeats in the N-terminal of ECD. LRP4 only with extracellular domain acts as a similar mechanism of full-length LRP4 in muscles to stimulate acetylcholine receptor clustering. In this study, we elucidated that LDLα repeats of LRP4 maintained the body weight and survival rate. Dendritic branches of the pyramidal neurons in Lrp4-null mice with LRP4 LDLα repeats residue were more than in Lrp4-null mice without residual LRP4 domain. Supplement with conditioned medium from LRP4 LDLα overexpression cells, the primary culture pyramidal neurons achieved strong dendritic arborization ability. Besides, astrocytes with LRP4 LDLα repeats residue could promote pyramidal neuronal dendrite arborization in the primary co-cultured system. These observations signify that LRP4 LDLα repeats play a prominent underlying role in dendrite arborization.

Up-regulation of the p75 neurotrophin receptor is an essential mechanism for HIV-gp120 mediated synaptic loss in the striatum

Reduced synaptodendritic complexity appears to be a key feature in human immunodeficiency virus (HIV)-associated neurological disorder (HAND). Viral proteins, and in particular the envelope protein gp120, play a role in the pathology of synapses. Gp120 has been shown to increase both in vitro and in vivo the proneurotrophin brain-derived neurotrophic factor, which promotes synaptic simplification through the activation of the p75 neurotrophin receptor (p75NTR). To provide evidence that p75NTR plays a role in gp120-mediated loss of synapses in vivo, we intercrossed gp120tg mice with p75NTR null mice and used molecular, histological and behavioral analyses to establish a link between p75NTR and gp120-mediated synaptic simplification. Synaptosomes obtained from the striatum of gp120tg mice exhibited a significant increase in p75NTR levels concomitantly to a decrease in synaptic markers such as TrkB and PSD95. Analysis of striatal dendritic spines by Golgi staining revealed that gp120tg mice display a reduced proportion of mushroom-type spines in addition to fewer spines overall, when compared to wild type or gp120tg lacking one or two p75NTR alleles. Moreover, removal of one p75NTR allele in gp120 transgenic mice abolished the gp120-driven impairment on a task of striatal-dependent motor learning. These data indicate that p75NTR could be a key player in HIV-mediated synaptic simplification in the striatum.

Somato-dendritic morphology and axon origin site specify von Economo neurons as a subclass of modified pyramidal neurons in the human anterior cingulate cortex

Von Economo neurons (VENs) are modified pyramidal neurons characterized by an extremely elongated rod-shaped soma. They are abundant in layer V of the anterior cingulate cortex (ACC) and fronto-insular cortex (FI) of the human brain, and have long been described as a human-specific neuron type. Recently, VENs have been reported in the ACC of apes and the FI of macaque monkeys. The first description of the somato-dendritic morphology of VENs in the FI by Cajal in 1899 (Textura del Sistema Nervioso del Hombre y de los Vertebrados, Tomo II. Madrid: Nicolas Moya) strongly suggested that they were a unique neuron subtype with specific morphological features. It is surprising that a clarification of this extremely important observation has not yet been attempted, especially as possible misidentification of other oval or fusiform cells as VENs has become relevant in many recently published studies. Here, we analyzed sections of Brodmann area 24 (ACC) stained with rapid Golgi and Golgi-Cox in five adult human specimens, and confirmed Cajal's observations. In addition, we established a comprehensive morphological description of VENs. VENs have a distinct somato-dendritic morphology that allows their clear distinction from other modified pyramidal neurons. We established that VENs have a perpendicularly oriented, stick-shaped core part consisting of the cell body and two thick extensions - an apical and basal stem. The perpendicular length of the core part was 150-250 μm and the thickness was 10-21 μm. The core part was characterized by a lack of clear demarcation between the cell body and the two extensions. Numerous thin, spiny and horizontally oriented side dendrites arose from the cell body. The basal extension of the core part typically ended by giving numerous smaller dendrites with a brush-like branching pattern. The apical extension had a topology typical for apical dendrites of pyramidal neurons. The dendrites arising from the core part had a high dendritic spine density. The most distinct feature of VENs was the distant origin site of the axon, which arose from the ending of the basal extension, often having a common origin with a dendrite. Quantitative analysis found that VENs could be divided into two groups based on total dendritic length - small VENs with a peak total dendritic length of 1500-2500 μm and large VENs with a peak total dendritic length of 5000-6000 μm. Comparative morphological analysis of VENs and other oval and fusiform modified pyramidal neurons showed that on Nissl sections small VENs might be difficult to identify, and that oval and fusiform neurons could be misidentified as VENs. Our analysis of Golgi slides of Brodmann area 9 from a total of 32 adult human subjects revealed only one cell resembling VEN morphology. Thus, our data show that the numerous recent reports on the presence of VENs in non-primates in other layers and regions of the cortex need further confirmation by showing the dendritic and axonal morphology of these cells. In conclusion, our study provides a foundation for further comprehensive morphological and functional studies on VENs between different species.

Golgi-Cox Staining of Neuronal Dendrites and Dendritic Spines With FD Rapid GolgiStain™ Kit

The Golgi-Cox method has been one of the most effective techniques for studying the morphology of neuronal dendrites and dendritic spines. However, the reliability and time-consuming process of Golgi-Cox staining have been major obstacles to the widespread application of this technique. To overcome these shortcomings and to promote this invaluable technique, we developed the FD Rapid GolgiStain™ Kit based on the principle of the methods described by Ramón-Moliner in 1970 and Glaser and Van der Loos in 1981. The kit significantly improves and simplifies the Golgi-Cox technique. This kit is reliable for visualizing morphological details of neurons, allowing for analysis of various parameters of dendritic morphology-such as dendritic length and branching pattern and dendritic spine number, shape, and size-in both animal and postmortem human brains. A 40-min instructional video for tissue freezing, cryosectioning, and staining is provided. © 2019 by John Wiley & Sons, Inc.

Effect of α-lipoic acid on spatial memory and structural integrity of developing hippocampal neurons in rats subjected to sodium arsenite exposure

BACKGROUND

Exposure to arsenic has been reported to affect the nervous system in a number of ways. Various epidemiological studies suggest cognitive impairment in subjects following exposure to environmental arsenic. The goal of the present study was to determine if supplementation of exogenous α-lipoic acid (ALA) could ameliorate sodium arsenite (NaAsO₂) induced adverse effects on learning and memory and synaptic connectivity in rat hippocampus.

METHODS

Accordingly, NaAsO₂ alone (1.5/2.0 mg/kg bw) or NaAsO₂ along with ALA (70 mg/kg bw) was administered by intraperitoneal (i.p.) route from postnatal day (PND) 4-17 to Wistar rat pups (experimental groups) and the Control groups received either distilled water or no treatment at all. After carrying out Elevated Plus Maze (EPM) and Morris Water Maze (MWM) test, the fresh brain tissues were collected on PND 18 and processed for Golgi Cox staining.

RESULTS

Observations of MWM test revealed impaired learning and memory in iAs alone treated animals as against those co-exposed to iAs and ALA. In Golgi stained hippocampal sections of iAs alone treated animals, decreased dendritic arborization and reduced number of spines in pyramidal neurons (CA1) and granule cells (DG) was observed whereas neuronal morphology was preserved in the controls and ALA supplemented groups CONCLUSIONS: These observations are suggestive of beneficial effects of ALA on iAs induced effects on learning and memory as well as on hippocampal neuronal morphology.

Synaptic development of layer V pyramidal neurons in the prenatal human prefrontal neocortex: a Neurolucida-aided Golgi study

The prefrontal neocortex is involved in many high cognitive functions in humans. Deficits in neuronal and neurocircuitry development in this part of the cerebrum have been associated with various neuropsychiatric disorders in adolescents and adults. There are currently little available data regarding prenatal dendrite and spine formation on projecting neurons in the human prefrontal neocortex. Previous studies have demonstrated that Golgi silver staining can identify neurons in the frontal lobe and visual cortex in human embryos. In the present study, five fetal brains, at 19, 20, 26, 35, and 38 gestational weeks, were obtained via the body donation program at Xiangya School of Medicine, Central South University, China. Golgi-stained pyramidal neurons in layer V of Brodmann area 46 in fetuses were quantitatively analyzed using the Neurolucida morphometry system. Results revealed that somal size, total dendritic length, and branching points of these neurons increased from 26 to 38 gestational weeks. There was also a large increase in dendritic spines from 35 to 38 gestational weeks. These findings indicate that, in the human prefrontal neocortex, dendritic growth in layer V pyramidal neurons occurs rapidly during the third trimester of gestation. The use of human fetal brain tissue was approved by the Animal Ethics Committee of Xiangya School of Medicine, Central South University, China (approval No. 2011-045) on April 5, 2011.

Combined Treatment with Low-Dose Ionizing Radiation and Ketamine Induces Adverse Changes in CA1 Neuronal Structure in Male Murine Hippocampi

In children, ketamine sedation is often used during radiological procedures. Combined exposure of ketamine and radiation at doses that alone did not affect learning and memory induced permanent cognitive impairment in mice. The aim of this study was to elucidate the mechanism behind this adverse outcome. Neonatal male NMRI mice were administered ketamine (7.5 mg kg⁻¹) and irradiated (whole-body, 100 mGy or 200 mGy, ¹³⁷Cs) one hour after ketamine exposure on postnatal day 10. The control mice were injected with saline and sham-irradiated. The hippocampi were analyzed using label-free proteomics, immunoblotting, and Golgi staining of CA1 neurons six months after treatment. Mice co-exposed to ketamine and low-dose radiation showed alterations in hippocampal proteins related to neuronal shaping and synaptic plasticity. The expression of brain-derived neurotrophic factor, activity-regulated cytoskeleton-associated protein, and postsynaptic density protein 95 were significantly altered only after the combined treatment (100 mGy or 200 mGy combined with ketamine, respectively). Increased numbers of basal dendrites and branching were observed only after the co-exposure, thereby constituting a possible reason for the displayed alterations in behavior. These data suggest that the risk of radiation-induced neurotoxic effects in the pediatric population may be underestimated if based only on the radiation dose.

Step by Step Golgi-Cox Staining for Cryosection

Golgi staining, though invented hundreds of years ago, is still a reliable method to study the cytoarchitecture of the brain. Almost all published Golgi staining protocols and methods were used for microtome, and rarely applied in cryosection, which restricted the application of this technique. Currently, several commercial Golgi-stain kits are available for both vibratome section and cryosection, but these kits are costly, and it is still challenging for researchers to obtain significant results. In the present study, we described a protocol of Golgi-Cox Staining for Cryosection, with the modified cryosection protection solution based on the Golgi-Cox method, which makes cryosection easy to apply in the section of the Golgi-Cox impregnated tissue. Our methods provide a low-cost and simple option for Golgi staining, and it will facilitate researchers to obtain useful Golgi staining results for neuronal architecture studies.

The Original Histological Slides of Camillo Golgi and His Discoveries on Neuronal Structure

The metallic impregnation invented by Camillo Golgi in 1873 has allowed the visualization of individual neurons in their entirety, leading to a breakthrough in the knowledge on the structure of the nervous system. Professor of Histology and of General Pathology, Golgi worked for decades at the University of Pavia, leading a very active laboratory. Unfortunately, most of Golgi's histological preparations are lost. The present contribution provides an account of the original slides on the nervous system from Golgi's laboratory available nowadays at the Golgi Museum and Historical Museum of the University of Pavia. Knowledge on the organization of the nervous tissue at the time of Golgi's observations is recalled. Notes on the equipment of Golgi's laboratory and the methodology Golgi used for his preparations are presented. Images of neurons from his slides (mostly from hippocampus, neocortex and cerebellum) are here shown for the first time together with some of Golgi's drawings. The sections are stained with the Golgi impregnation and Cajal stain. Golgi-impregnated sections are very thick (some more than 150 μm) and require continuous focusing during the microscopic observation. Heterogeneity of neuronal size and shape, free endings of distal dendritic arborizations, axonal branching stand out at the microscopic observation of Golgi-impregnated sections and in Golgi's drawings, and were novel findings at his time. Golgi also pointed out that the axon only originates from cell bodies, representing a constant and distinctive feature of nerve cells which distinguishes them from glia, and subserving transmission at a distance. Dendritic spines can be seen in some cortical neurons, although Golgi, possibly worried about artifacts, did not identify them. The puzzling intricacy of fully impregnated nervous tissue components offered to the first microscopic observations still elicit nowadays the emotion Golgi must have felt looking at his slides.

An update on the Golgi staining technique improving cerebellar cell type specificity

The detailed morphological characterization of single cells was a major breakthrough in neuroscience during the turn of the twentieth century, enabling Ramon y Cajal to postulate the neuron doctrine. Even after 150 years, single cell analysis is an intriguing goal, newly motivated by the finding that autism might be caused by intricate and discreet changes in cerebellar morphology. Besides new single labelling technologies, the Golgi staining technique is still in use due to its whole cell labelling characteristics, its superior contrast performance over other methods and its apparent randomness of staining cells within a whole tissue block. However, the specificity and whole cell labelling of Golgi staining are also disputed controversially, and the method still has a poor reputation for being time consuming and needing high expenditures. We demonstrate here, how a classical Golgi technique can be adapted for staining different cerebellar cell types using a time-saving and efficient protocol, enabling the identification of the detailed morphological characteristics of single cells.

Temporal Dynamics of Acute Stress-Induced Dendritic Remodeling in Medial Prefrontal Cortex and the Protective Effect of Desipramine

Stressful events are associated with increased risk of mood disorders. Volumetric reductions have been reported in brain areas critical for the stress response, such as medial prefrontal cortex (mPFC), and dendritic remodeling has been proposed as an underlying factor. Here, we investigated the time-dependent effects of acute stress on dendritic remodeling within the prelimbic (PL) region of the PFC, and whether treatment with the antidepressant desipramine (DMI) may interfere. Rodents were subjected to foot-shock stress: dendritic length and spine density were analyzed 1 day, 7 days, and 14 days after stress. Acute stress produced increased spine density and decreased cofilin phosphorylation at 1 day, paralleled with dendritic retraction. An overall shift in spine population was observed at 1 day, resulting in a stress-induced increase in small spines. Significant atrophy of apical dendrites was observed at 1 day, which was prevented by chronic DMI, and at 14 days after stress exposure. Chronic DMI resulted in dendritic elaboration at 7 days but did not prevent the effects of FS-stress. Collectively, these data demonstrate that 1) acute stressors may induce rapid and sustained changes of PL neurons; and 2) chronic DMI may protect neurons from rapid stress-induced synaptic changes.

Chronic corticosterone administration reduces dendritic complexity in mature, but not young granule cells in the rat dentate gyrus

Background: Our previous work has shown that exposure to the stress hormone corticosterone (40 mg/kg CORT) for two weeks induces dendritic atrophy of pyramidal neurons in the hippocampal CA3 region and behavioral deficits. However, it is unclear whether this treatment also affects the dentate gyrus (DG), a subregion of the hippocampus comprising a heterogeneous population of young and mature neurons.

Objective: We examined the effect of CORT treatment on the dendritic complexity of mature and young granule cells in the DG.

Methods: We utilized a Golgi staining method to investigate the dendritic morphology and spine density of young neurons in the inner granular cell layer (GCL) and mature neurons in the outer GCL in response to CORT application. The expressions of glucocorticoid receptors during neuronal maturation were examined using Western blot analysis in a primary hippocampal neuronal culture.

Results: Sholl analysis revealed that CORT treatment decreased the number of intersections and shortened the dendritic length in mature, but not young, granule cells. However, the spine density of mature and young neurons was not affected. Western blot analysis showed a progressive increase in the protein levels of glucocorticoid receptors (GRs) in the cultured primary hippocampal neurons during neuronal maturation.

Conclusion: These data suggest that mature neurons are likely more vulnerable to chronic exposure to CORT; this may be due to their higher expression of GRs when compared to younger DG neurons.

Acupuncture improves dendritic structure and spatial learning and memory ability of Alzheimer's disease mice

Acupuncture can improve the cognitive state of Alzheimer's disease, but its mechanism is not clear. Dendritic atrophy and synaptic loss in Alzheimer's disease brain are positively correlated with cognitive damage. Therefore, we speculated that the effect of acupuncture on improving cognitive function may be associated with reduced dendritic damage in the brain. Acupuncture at Qihai (CV6), Zhongwan (CV12), Danzhong (CV17), bilateral Zusanli (ST36), and bilateral Xuehai (SP10) acupoints was performed once a day (1-day rest after 6-day treatment) for 14 consecutive days. Senescence-accelerated mouse prone 8 (SAMP8) mice without acupuncture and senescence-accelerated mouse resistant 1 (SAMR1) mice were used as normal controls. After 14 days of treatment, spatial learning and memory ability of mice was assessed in each group using the Morris water maze. Dendritic changes of pyramidal cells in the hippocampal CA1 region were analyzed by quantitative Golgi staining. Our results showed that acupuncture shortened escape latency and lengthened retention time of the former platform quadrant in SAMP8 mice. Further, SAMP8 mice exhibited a significant increase in the number of apical and basal dendritic branches and total length of apical and basal dendrites after acupuncture. These results suggest that acupuncture improves spatial learning and memory ability of middle-aged SAMP8 mice by ameliorating dendritic structure.

Studies for Improving a Rat Model of Alzheimer's Disease: Icv Administration of Well-Characterized β-Amyloid 1-42 Oligomers Induce Dysfunction in Spatial Memory

During the past 15 years, several genetically altered mouse models of human Alzheimer’s disease (AD) have been developed. These costly models have greatly facilitated the evaluation of novel therapeutic approaches. Injecting synthetic β-amyloid (Aβ) 1-42 species into different parts of the brain of non-transgenic rodents frequently provided unreliable results, owing to a lack of a genuine characterization of the administered Aβ aggregates. Previously, we have published a new rat AD-model in which protofibrillar-fibrillar Aβ1-42 was administered into rat entorhinal cortex (Sipos 2007). In order to develop a more reliable model, we have injected well-characterized toxic soluble Aβ1-42 species (oligomers, protofibrils and fibrils) intracerebroventricularly (icv) into rat brain. Studies of the distribution of fluorescent-labeled Aβ1-42 in the brain showed that soluble Aβ-species diffused into all parts of the rat brain. After seven days, the Aβ-treated animals showed a significant decrease of spatial memory in Morris water maze test and impairment of synaptic plasticity (LTP) measured in acute hippocampal slices. The results of histological studies (decreased number of viable neurons, increased tau levels and decreased number of dendritic spines) also supported that icv administration of well-characterized toxic soluble Aβ species into rat brain provides a reliable rat AD-model.

Valid statistical approaches for analyzing sholl data: Mixed effects versus simple linear models

BACKGROUND

The Sholl technique is widely used to quantify dendritic morphology. Data from such studies, which typically sample multiple neurons per animal, are often analyzed using simple linear models. However, simple linear models fail to account for intra-class correlation that occurs with clustered data, which can lead to faulty inferences.

NEW METHOD

Mixed effects models account for intra-class correlation that occurs with clustered data; thus, these models more accurately estimate the standard deviation of the parameter estimate, which produces more accurate p-values. While mixed models are not new, their use in neuroscience has lagged behind their use in other disciplines.

RESULTS

A review of the published literature illustrates common mistakes in analyses of Sholl data. Analysis of Sholl data collected from Golgi-stained pyramidal neurons in the hippocampus of male and female mice using both simple linear and mixed effects models demonstrates that the p-values and standard deviations obtained using the simple linear models are biased downwards and lead to erroneous rejection of the null hypothesis in some analyses.

COMPARISON WITH EXISTING METHODS

The mixed effects approach more accurately models the true variability in the data set, which leads to correct inference.

CONCLUSIONS

Mixed effects models avoid faulty inference in Sholl analysis of data sampled from multiple neurons per animal by accounting for intra-class correlation. Given the widespread practice in neuroscience of obtaining multiple measurements per subject, there is a critical need to apply mixed effects models more widely.

Tolerance of hyperammonemia in brain of Heteropneustes fossilis is supported by glutamate-glutamine cycle

This report presents analysis of molecular switches associated with tolerance to hyperammonemia in Heteropneustes fossilis because it tolerates about 100-fold more ammonia than mammals. Brains of Heteropneustes fossilis exposed to 100mM ammonium chloride were dissected after Zero hour as control, 16h and 20h exposure. The status of neuron and glia were analysed by Golgi staining, Luxol Fast Blue, and Nissl's staining. The expression patterns of genes associated to homeostasis of neuron and glia, management of oxidative stress and inflammation, ammonia metabolism and brain derived neurotrophic factor were analysed through reverse-transcriptase-polymerase chain reaction. After 20h of hyperammonemia glia were more degenerated than neurons. The expression of mRNA of lactate dehydrogenase (Ldh), super oxide dismutase (Sod), catalase (Catalase), arginase-I (Arg I), inducible nitric oxide (iNos), glutaminase (GA), and brain derived neurotrophic factor (Bdnf) was up-regulated than the control. The levels of mRNA of Arg II, glutamate dehydrogenase (Gdh), glutamine synthetase (GS), glial fibrillary acidic protein (Gfap), proliferating cell nuclear antigen (Pcna) and S100β were down-regulated than control due to hyperammonemia. It appears first observation on impact of hyperammonemia on the status of neurons, myelination and glial cells in brain of Heteropneustes fossilis by Golgi staining, Nissl's and Luxol Fast Blue staining. The distribution of ammonia and glutamate metabolising enzymes in brain supports multi-centric mechanism (s) of regulation. The expression of Arg I and Arg II gets inversely regulated and glutamate-glutamine cycle also operates in Heteropneustes fossilis against hyperammonemia in brain.

Sex-dependent changes in neuronal morphology and psychosocial behaviors after pediatric brain injury

Chronic social behavior problems after pediatric traumatic brain injury (TBI) significantly contribute to poor quality of life for survivors. Using a well-characterized mouse model of early childhood TBI, we have previously demonstrated that young brain-injured mice develop social deficits by adulthood. As biological sex may influence both normal and aberrant social development, we here evaluated potential sex differences in post-TBI psychosocial deficits by comparing the behavior of male and female mice at adulthood (8 weeks post-injury). Secondly, we hypothesized that pediatric TBI would influence neuronal morphology identified by Golgi-Cox staining in the hippocampus and prefrontal cortex, regions involved in social cognition and behavior, before the onset of social problems (3 weeks post-injury). Morphological analysis of pyramidal neurons in the ipsilateral prefrontal cortex and granule cells of the hippocampal dentate gyrus revealed a reduction in dendritic complexity after pediatric TBI. This was most apparent in TBI males, whereas neurons from females were less affected. At adulthood, consistent with previous studies, TBI males showed deficits in sociability and social recognition. TBI females also showed a reduction in sociability, but intact social recognition and increased sociosexual avoidance. Together, these findings indicate that sex is a determinant of regional neuroplasticity and social outcomes after pediatric TBI. Reduced neuronal complexity in the prefrontal cortex and hippocampus, several weeks after injury in male mice, appears to precede the subsequent emergence of social deficits. Sex-specific alterations in the social brain network are thus implicated as an underlying mechanism of social dysfunction after pediatric TBI.

EphA5 and EphA6: regulation of neuronal and spine morphology

Background

The Eph family of receptor tyrosine kinases plays important roles in neural development. Previous studies have implicated Eph receptors and their ligands, the ephrins, in neuronal migration, axon bundling and guidance to specific targets, dendritic spine formation and neural plasticity. However, specific contributions of EphA5 and EphA6 receptors to the regulation of neuronal cell morphology have not been well studied.

Results

Here we show that deletion of EphA5 and EphA6 results in abnormal Golgi staining patterns of cells in the brain, and abnormal spine morphology.

Conclusion

These observations suggest novel functions of these Eph receptors in the regulation of neuronal and spine structure in brain development and function.

L-3-n-butylphthalide Rescues Hippocampal Synaptic Failure and Attenuates Neuropathology in Aged APP/PS1 Mouse Model of Alzheimer's Disease

AIMS

Our previous studies showed that L-3-n-butylphthalide (L-NBP), an extract from seeds of Apium graveolens Linn (Chinese celery), improved cognitive ability in animal models of cerebral ischemia, vascular dementia, and Alzheimer's disease (AD). It is well known that cognitive deficit of AD is caused by synaptic dysfunction. In this study, we investigated the effect of L-NBP on hippocampal synaptic function in APP/PS1 AD transgenic mice and related mechanisms.

METHODS

Eighteen-month-old APP/PS1 transgenic (Tg) mice were administrated 15 mg/kg L-NBP by oral gavage for 3 months. Synaptic morphology and the thickness of postsynaptic density (PSD) in hippocampal neurons were investigated by electron microscope. The dendritic spines, Aβ plaques, and glial activation were detected by staining. The expressions of synapse-related proteins were observed by Western blotting.

RESULTS

L-NBP treatment significantly increased the number of synapses and apical dendritic thorns and the thickness of PSD, increased the expression levels of synapse-associated proteins including PSD95, synaptophysin (SYN), β-catenin, and GSK-3β, and attenuated Aβ plaques and neuroinflammatory responses in aged APP/PS1 Tg mice.

CONCLUSION

L-NBP may restore synaptic and spine function in aged APP Tg mice through inhibiting Aβ plaques deposition and neuroinflammatory response. Wnt/β-catenin signaling pathway may be involved in L-NBP-related restoration of synaptic function.

Mammillary Bodies in Alzheimer's Disease: A Golgi and Electron Microscope Study

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, characterized by irreversible memory decline, concerning no rarely spatial memory and orientation, alterations of the mood and personality, gradual loss of motor skills, and substantial loss of capacities obtained by previous long education. We attempted to describe the morphological findings of the mammillary bodies in early cases of AD. Samples were processed for electron microscopy and silver impregnation techniques. The nuclei of the mammillary bodies demonstrated a substantial decrease in the neuronal population and marked abbreviation of dendritic arbors. Decrease in spine density and morphological abnormalities of dendritic spines was also seen. Synaptic alterations were prominent. Alzheimer's pathology, such as deposits of amyloid-β peptide and neurofibrillary degeneration, was minimal. Electron microscopy revealed mitochondrial alterations and fragmentation of Golgi apparatus, associated frequently with synaptic pathology.

The hypothalamus in Alzheimer's disease: a Golgi and electron microscope study

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, characterized by irreversible decline of mental faculties, emotional and behavioral changes, loss of motor skills, and dysfunction of autonomic nervous system and disruption of circadian rhythms (CRs). We attempted to describe the morphological findings of the hypothalamus in early cases of AD, focusing our study mostly on the suprachiasmatic nucleus (SCN), the supraoptic nucleus (SON), and the paraventricular nucleus (PVN). Samples were processed for electron microscopy and silver impregnation techniques. The hypothalamic nuclei demonstrated a substantial decrease in the neuronal population, which was particularly prominent in the SCN. Marked abbreviation of dendritic arborization, in association with spinal pathology, was also seen. The SON and PVN demonstrated a substantial number of dystrophic axons and abnormal spines. Alzheimer's pathology, such as deposits of amyloid-β peptide and neurofibrillary degeneration, was minimal. Electron microscopy revealed mitochondrial alterations in the cell body and the dendritic branches. The morphological alterations of the hypothalamic nuclei in early cases of AD may be related to the gradual alteration of CRs and the instability of autonomic regulation.

Repeated administration of a synthetic cannabinoid receptor agonist differentially affects cortical and accumbal neuronal morphology in adolescent and adult rats

Recent studies demonstrate a differential trajectory for cannabinoid receptor expression in cortical and sub-cortical brain areas across postnatal development. In the present study, we sought to investigate whether chronic systemic exposure to a synthetic cannabinoid receptor agonist causes morphological changes in the structure of dendrites and dendritic spines in adolescent and adult pyramidal neurons in the medial prefrontal cortex (mPFC) and medium spiny neurons (MSN) in the nucleus accumbens (Acb). Following systemic administration of WIN 55,212-2 in adolescent (PN 37-40) and adult (P55-60) male rats, the neuronal architecture of pyramidal neurons and MSN was assessed using Golgi-Cox staining. While no structural changes were observed in WIN 55,212-2-treated adolescent subjects compared to control, exposure to WIN 55,212-2 significantly increased dendritic length, spine density and the number of dendritic branches in pyramidal neurons in the mPFC of adult subjects when compared to control and adolescent subjects. In the Acb, WIN 55,212-2 exposure significantly decreased dendritic length and number of branches in adult rat subjects while no changes were observed in the adolescent groups. In contrast, spine density was significantly decreased in both the adult and adolescent groups in the Acb. To determine whether regional developmental morphological changes translated into behavioral differences, WIN 55,212-2-induced aversion was evaluated in both groups using a conditioned place preference paradigm. In adult rats, WIN 55,212-2 administration readily induced conditioned place aversion as previously described. In contrast, adolescent rats did not exhibit aversion following WIN 55,212-2 exposure in the behavioral paradigm. The present results show that synthetic cannabinoid administration differentially impacts cortical and sub-cortical neuronal morphology in adult compared to adolescent subjects. Such differences may underlie the disparate development effects of cannabinoids on behavior.

Hybrid voltage sensor imaging of eGFP-F expressing neurons in chicken midbrain slices

BACKGROUND

Dendritic computation is essential for understanding information processing in single neurons and brain circuits. Optical methods are suited best to investigate function and biophysical properties of cellular compartments at high spatial and temporal resolution. Promising approaches include the use of voltage sensitive dyes, genetically encoded voltage sensors, or hybrid voltage sensors (hVoS) consisting of fluorescent proteins and voltage-dependent quenchers that, so far, are not available in avian neuroscience.

NEW METHOD

We have adapted a hVoS system for a chicken midbrain slice preparation by combining genetically expressed farnesylated eGFP with dipicrylamine (DPA). Depending on the cellular potential, DPA is shifted in the membrane, resulting in quenching of eGFP fluorescence linearly to the membrane potential by Förster resonance electron transfer.

RESULTS

In ovo electroporation resulted in labelled neurons throughout the midbrain with a high level of fine structural detail. After application of DPA, we were able to optically record electrically evoked action potentials with high signal-to-noise ratio and high spatio-temporal resolution.

COMPARISON WITH EXISTING METHODS

Standard methods available for avian neuroscience such as whole-cell patch clamp yield insufficient data for the analysis of dendritic computation in single neurons. The high spatial and temporal resolution of hVoS data overcomes this limitation. The results obtained by our method are comparable to hVoS data published for mammals.

CONCLUSIONS

With the protocol presented here, it is possible to optically record information processing in single avian neurons at such high spatial and temporal resolution, that cellular and subcellular events can be analysed.

RanBP9 overexpression reduces dendritic arbor and spine density

RanBP9 is a multi-domain scaffolding protein known to integrate extracellular signaling with intracellular targets. We previously demonstrated that RanBP9 enhances Aβ generation and amyloid plaque burden which results in loss of specific pre- and postsynaptic proteins in vivo in a transgenic mouse model. Additionally, we showed that the levels of spinophilin, a marker of dendritic spines were inversely proportional to the RanBP9 protein levels within the synaptosomes isolated from AD brains. In the present study, we found reduced dendritic intersections within the layer 6 pyramidal neurons of the cortex as well as the hippocampus of RanBP9 transgenic mice compared to age-matched wild-type (WT) controls at 12 months of age but not at 6months. Similarly, the dendritic spine numbers were reduced in the cortex at only 12 months of age by 30% (p<0.01), but not at 6months. In the hippocampus also the spine densities were reduced at 12 months of age (38%, p<0.01) in the RanBP9 transgenic mice. Interestingly, the levels of phosphorylated form of cofilin, an actin binding protein that plays crucial role in the regulation of spine numbers were significantly decreased in the cortical synaptosomes at only 12months of age by 26% (p<0.01). In the hippocampal synaptosomes, the decrease in cofilin levels were 36% (p<0.01) at 12 months of age. Thus dendritic arbor and spine density were directly correlated to the levels of phosphorylated form of cofilin in the RanBP9 transgenic mice. Similarly, cortical synaptosomes showed a 20% (p<0.01) reduction in the levels of spinophilin in the RanBP9 transgenic mice. These results provided the physical basis for the loss of synaptic proteins by RanBP9 and most importantly it also explains the impaired spatial learning and memory skills previously observed in the RanBP9 transgenic mice.

Distinct cerebellar engrams in short-term and long-term motor learning

Cerebellar motor learning is suggested to be caused by long-term plasticity of excitatory parallel fiber-Purkinje cell (PF-PC) synapses associated with changes in the number of synaptic AMPA-type glutamate receptors (AMPARs). However, whether the AMPARs decrease or increase in individual PF-PC synapses occurs in physiological motor learning and accounts for memory that lasts over days remains elusive. We combined quantitative SDS-digested freeze-fracture replica labeling for AMPAR and physical dissector electron microscopy with a simple model of cerebellar motor learning, adaptation of horizontal optokinetic response (HOKR) in mouse. After 1-h training of HOKR, short-term adaptation (STA) was accompanied with transient decrease in AMPARs by 28% in target PF-PC synapses. STA was well correlated with AMPAR decrease in individual animals and both STA and AMPAR decrease recovered to basal levels within 24 h. Surprisingly, long-term adaptation (LTA) after five consecutive daily trainings of 1-h HOKR did not alter the number of AMPARs in PF-PC synapses but caused gradual and persistent synapse elimination by 45%, with corresponding PC spine loss by the fifth training day. Furthermore, recovery of LTA after 2 wk was well correlated with increase of PF-PC synapses to the control level. Our findings indicate that the AMPARs decrease in PF-PC synapses and the elimination of these synapses are in vivo engrams in short- and long-term motor learning, respectively, showing a unique type of synaptic plasticity that may contribute to memory consolidation.

Rho GTPase-dependent plasticity of dendritic spines in the adult brain

Brain activity is associated with structural changes in the neural connections. However, in vivo imaging of the outer cortical layers has shown that dendritic spines, on which most excitatory synapses insist, are predominantly stable in adulthood. Changes in dendritic spines are governed by small GTPases of the Rho family through modulation of the actin cytoskeleton. Yet, while there are abundant data about this functional effect of Rho GTPases in vitro, there is limited evidence that Rho GTPase signaling in the brain is associated with changes in neuronal morphology. In the present work, both chronic in vivo two-photon imaging and Golgi staining reveal that the activation of Rho GTPases in the adult mouse brain is associated with little change of dendritic spines in the apical dendrites of primary visual cortex pyramidal neurons. On the contrary, considerable increase in spine density is observed (i) in the basal dendrites of the same neurons (ii) in both basal and apical dendrites of the hippocampal CA1 pyramidal cells. While confirming that Rho GTPase-dependent increase in spine density can be substantial, the study indicates region and dendrite selectivity with relative stability of superficial cortical circuits.