Determining factors for optimal neuronal and glial Golgi-Cox staining

A refined Golgi-Cox method for the staining of embryonic neurons in the mouse brain

The Golgi-Cox stain remains a valuable technique used to investigate the morphology of individual neurons. Despite this, Golgi-Cox staining protocols are predominantly designed to impregnate adult neurons. Protocols optimised for the staining of immature embryonic mouse neurons have been previously developed but have limitations, including being time-consuming and being reliant on the use of expensive commercial kits. Here, we present a simple and inexpensive method for Golgi-Cox staining of embryonic neurons in the mouse brain. We identified that a 60 minute, 4 % paraformaldehyde (PFA) brain fixation step, followed by a wash with distilled water prior to immersion in Golgi-Cox solution was critical to the success of the stain. By altering the duration of the wash step, the visualisation of different populations across the neuraxis of neurons could be emphasised. Shorter washes enabled cortical neurons to be readily distinguished, whereas extending the wash steps was needed to enable subcortical neurons to be delineated.

Reshaping the gut microbiota: A novel oppinion of Eucommiae cortex polysaccharide alleviate learning and memory impairments in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD), which is a chronic neurodegenerative disorder, is marked by the progressive deteriorations in learning and memory capabilities. The microbiota-gut-brain axis has come to be regarded as a crucial element in relation to the pathogenesis as well as the treatment of AD. Eucommiae cortex polysaccharides (EPs), being among the most plentiful substances present in the Eucommiae cortex, show the potential to exert immunomodulatory and neuroprotective function. However, whether EPs are protective against AD and their mechanism of action remain to be investigated OBJECTIVES: We hypothesize that EPs can regulate brain glutamine metabolism through gut microbiota and the butyric acid metabolized by them, improve oxidative stress and autophagy in the brain, and thus alleviate AD.

METHODS

In the present study, we used EPs (0.25 % w/w in food) and fecal microbiota transplantation, as well as butyrate supplementation (0.1 M in water), to intervene in AD mice. Multi-omics were used to determine the mechanism by which EPs improve AD-related learning and memory impairments.

RESULTS

Our results suggest that EPs, functioning as a prebiotic, alleviated learning and memory impairments in AD mice. Mechanistically, EPs are able to reshape the gut microbiota, promote the growth of gut microbiota involved in short-chain fatty acid metabolism, particularly butyrate-producing microbes. The butyrate produced by these microbes improves the brain microenvironment by modulating oxidative stress and autophagy mediated by brain glutamate metabolism, improving learning and memory impairments in AD mice, and inhibiting the formation and deposition of beta-amyloid proteins. Fecal microbiota transplantation (FMT) and butyrate supplementation further confirm this conclusion.

CONCLUSIONS

Our results highlighted that EPs can alleviate learning and memory impairments in AD with a gut microbiota-dependent manner and that butyric acid metabolized by butyric acid-metabolizing bacteria in the gut plays a central role in regulating brain glutamine metabolism to improve brain microenvironmental homeostasis. Meanwhile, the present study provides new insights into the treatment of AD with natural products.

GPR158 in pyramidal neurons mediates social novelty behavior via modulating synaptic transmission in male mice

Impairment in social communication skills is a hallmark feature of autism spectrum disorder (ASD). The role of G-protein-coupled receptor 158 (GPR158) in ASD remains largely unexplored. In this study, we observed that both constitutive and cell-/tissue-specific knockouts of Gpr158 in pyramidal neurons or the medial prefrontal cortex (mPFC) result in impaired novelty preference, while sociability remains unaffected in male mice. Notably, the loss of GPR158 leads to a significant decline in excitatory synaptic transmission, characterized by a reduction in glutamate vesicles, as well as the expression and phosphorylation of GluN2B in the mPFC. We successfully rescue the phenotype of social novelty deficits either by reintroducing GPR158 in the mPFC of Gpr158 deficient mice or by chemogenetic activation of pyramidal neurons where Gpr158 is specifically ablated. Our findings indicate that GPR158 in pyramidal neurons plays a specific role in modulating social novelty and may represent a potential target for treating social disorders.

A Deep Learning-based Pipeline for Segmenting the Cerebral Cortex Laminar Structure in Histology Images

Characterizing the anatomical structure and connectivity between cortical regions is a critical step towards understanding the information processing properties of the brain and will help provide insight into the nature of neurological disorders. A key feature of the mammalian cerebral cortex is its laminar structure. Identifying these layers in neuroimaging data is important for understanding their global structure and to help understand the connectivity patterns of neurons in the brain. We studied Nissl-stained and myelin-stained slice images of the brain of the common marmoset (Callithrix jacchus), which is a new world monkey that is becoming increasingly popular in the neuroscience community as an object of study. We present a novel computational framework that first acquired the cortical labels using AI-based tools followed by a trained deep learning model to segment cerebral cortical layers. We obtained a Euclidean distance of 1274.750 ± 156.400 μ m for the cortical labels acquisition, which was in the acceptable range by computing the half Euclidean distance of the average cortex thickness ( 1800.630 μ m ). We compared our cortical layer segmentation pipeline with the pipeline proposed by Wagstyl et al. (PLoS biology, 18(4), e3000678 2020) adapted to 2D data. We obtained a better mean95 th percentile Hausdorff distance (95HD) of  92.150 μ m . Whereas a mean 95HD of  94.170 μ m was obtained from Wagstyl et al. We also compared our pipeline's performance against theirs using their dataset (the BigBrain dataset). The results also showed better segmentation quality, 85.318 % Jaccard Index acquired from our pipeline, while 83.000 % was stated in their paper.

A combinatorial method to visualize the neuronal network in the mouse spinal cord: combination of a modified Golgi-Cox method and synchrotron radiation micro-computed tomography

Exploring the three-dimensional (3D) morphology of neurons is essential to understanding spinal cord function and associated diseases comprehensively. However, 3D imaging of the neuronal network in the broad region of the spinal cord at cellular resolution remains a challenge in the field of neuroscience. In this study, to obtain high-resolution 3D imaging of a detailed neuronal network in the mass of the spinal cord, the combination of synchrotron radiation micro-computed tomography (SRμCT) and the Golgi-cox staining were used. We optimized the Golgi-Cox method (GCM) and developed a modified GCM (M-GCM), which improved background staining, reduced the number of artefacts, and diminished the impact of incomplete vasculature compared to the current GCM. Moreover, we achieved high-resolution 3D imaging of the detailed neuronal network in the spinal cord through the combination of SRμCT and M-GCM. Our results showed that the M-GCM increased the contrast between the neuronal structure and its surrounding extracellular matrix. Compared to the GCM, the M-GCM also diminished the impact of the artefacts and incomplete vasculature on the 3D image. Additionally, the 3D neuronal architecture was successfully quantified using a combination of SRμCT and M-GCM. The SRμCT was shown to be a valuable non-destructive tool for 3D visualization of the neuronal network in the broad 3D region of the spinal cord. Such a combinatorial method will, therefore, transform the presentation of Golgi staining from 2 to 3D, providing significant improvements in the 3D rendering of the neuronal network.

Optimized Golgi-Cox Staining Validated in the Hippocampus of Spared Nerve Injury Mouse Model

Golgi-Cox staining has been used extensively in neuroscience. Despite its unique ability to identify neuronal interconnections and neural processes, its lack of consistency and time-consuming nature reduces its appeal to researchers. Here, using a spared nerve injury (SNI) mouse model and control mice, we present a modified Golgi-Cox staining protocol that can stain mouse hippocampal neurons within 8 days. In this improved procedure, the mouse brain was fixed with 4% paraformaldehyde and then stored in a modified Golgi-Cox solution at 37 ± 2°C. The impregnation period was reduced from 5–14 days to 36–48 h. Brain slices prepared in this way could be preserved long-term at –80°C for up to 8 weeks. In addition to minimizing frequently encountered problems and reducing the time required to conduct the method, our modified protocol maintained, and even improved, the quality of traditional Golgi-Cox staining as applied to hippocampal neuronal morphology in SNI mice.