The perception of motion is an important function of vision. Neural wiring diagrams for extracting directional information have been obtained by connectome reconstruction. Direction selectivity in Drosophila is thought to originate in T4/T5 neurons through integrating inputs with different temporal filtering properties. Through genetic screening based on synaptic distribution, we isolated a new type of TmY neuron, termed TmY-ds, that form reciprocal synaptic connections with T4/T5 neurons. Its neurites responded to grating motion along the four cardinal directions and showed a variety of direction selectivity. Intriguingly, its direction selectivity originated from temporal filtering neurons rather than T4/T5. Genetic silencing and activation experiments showed that TmY-ds neurons are functionally upstream of T4/T5. Our results suggest that direction selectivity is generated in a tripartite circuit formed among these three neurons-temporal filtering, TmY-ds, and T4/T5 neurons, in which TmY-ds plays a role in the enhancement of direction selectivity in T4/T5 neurons.
Animals ; Neurites ; Drosophila ; Neurons ; Connectome

OBJECTIVE: To clarify the functional effects of differential expression of ring finger and tryptophan-aspartic acid 2 (RFWD2) on dendritic development and formation of dendritic spines in cerebral cortex neurons of mice. METHODS: Immunofluorescent staining was used to identify the location and global expression profile of RFWD2 in mouse brain and determine the co-localization of RFWD2 with the synaptic proteins in the cortical neurons. We also examined the effects of RFWD2 over-expression (RFWD2-Myc) and RFWD2 knockdown (RFWD2-shRNA) on dendritic development, dendritic spine formation and synaptic function in cultured cortical neurons. RESULTS: RFWD2 is highly expressed in the cerebral cortex and hippocampus of mice, and its expression level was positively correlated with the development of cerebral cortex neurons and dendrites. RFWD2 expression was detected on the presynaptic membrane and postsynaptic membrane of the neurons, and its expression levels were positively correlated with the length, number of branches and complexity of the dendrites. In cultured cortical neurons, RFWD2 overexpression significantly lowered the expressions of the synaptic proteins synaptophysin (P < 0.01) and postsynapic density protein 95 (P < 0.01), while RFWD2 knockdown significantly increased their expressions (both P < 0.05). Compared with the control and RFWD2-overexpressing cells, the neurons with RFWD2 knockdown showed significantly reduced number of dendritic spines (both P < 0.05). CONCLUSION RFWD2 can regulate the expression of the synaptic proteins, the development of the dendrites, the formation of the dendritic spines and synaptic function in mouse cerebral cortex neurons through ubiquitination of Pea3 family members and c-Jun, which may serve as potential treatment targets for neurological diseases.
Animals ; Aspartic Acid/metabolism* ; Cerebral Cortex ; Dendritic Spines/metabolism* ; Mice ; Neurons/metabolism* ; Synapses ; Tryptophan/metabolism*

OBJECTIVE: To investigate the mechanism of valproic acid (VPA) -induced impairment of the dendritic spines and synapses in the prefrontal cortex (PFC) for causing core symptoms of autism spectrum disorder (ASD) in mice. METHODS: Female C57 mice were subjected to injections of saline or VPA on gestational days 10 and 12, and the male offspring mice in the two groups were used as the normal control group and ASD model group (n=10), respectively. Another 20 male mice with fetal exposure to VPA were randomized into two groups for stereotactic injection of DMSO or Wortmannin into the PFC (n=10). Open field test, juvenile play test and 3-chamber test were used to evaluate autistic behaviors of the mice. The density of dendrite spines in the PFC was observed with Golgi staining. Western blotting and immunofluorescence staining were used to detect the expressions of p-PI3K, PI3K, p-AKT, AKT, p-mTOR, mTOR and the synaptic proteins PSD95, p-Syn, and Syn in the PFC of the mice. RESULTS: Compared with the normal control mice, the mice with fetal exposure to VPA exhibited obvious autism-like behaviors with significantly decreased density of total, mushroom and stubby dendritic spines (P < 0.05) and increased filopodia dendritic spines (P < 0.05) in the PFC. The VPA-exposed mice also showed significantly increased expressions of p-PI3K/PI3K, p-AKT/AKT, and p-mTOR/mTOR (P < 0.01) and lowered expressions of PSD95 and p-Syn/Syn in the PFC (P < 0.05 or 0.001). Wortmannin injection into the PFC obviously improved the ASD-like phenotype and dendritic spine development, down-regulated PI3K/Akt/mTOR signaling pathway and up-regulated the synaptic proteins in VPA-exposed mice. CONCLUSION In male mice with fetal exposure to VPA, excessive activation of PI3K/Akt/mTOR signaling pathway and decreased expressions of the synaptic proteins PSD95 and p-Syn cause dendritic spine damage and synaptic development disturbance in the PFC, which eventually leads to ASD-like phenotype.
Animals ; Autism Spectrum Disorder/chemically induced* ; Autistic Disorder/chemically induced* ; Dendritic Spines ; Disease Models, Animal ; Female ; Male ; Mice ; Phosphatidylinositol 3-Kinases ; Prefrontal Cortex ; Prenatal Exposure Delayed Effects ; Valproic Acid/adverse effects*

A transient ischemic attack (TIA) can cause reversible and delayed impairment of cognition, but the specific mechanisms are still unclear. Annexin a1 (ANXA1) is a phospholipid-binding protein. Here, we confirmed that cognition and hippocampal synapses were impaired in TIA-treated mice, and this could be rescued by multiple mild stimulations (MMS). TIA promoted the interaction of ANXA1 and CX3CR1, increased the membrane distribution of CX3CR1 in microglia, and thus enhanced the CX3CR1 and CX3CL1 interaction. These phenomena induced by TIA could be reversed by MMS. Meanwhile, the CX3CR1 membrane distribution and CX3CR1-CX3CL1 interaction were upregulated in primary cultured microglia overexpressing ANXA1, and the spine density was significantly reduced in co-cultured microglia overexpressing ANXA1 and neurons. Moreover, ANXA1 overexpression in microglia abolished the protection of MMS after TIA. Collectively, our study provides a potential strategy for treating the delayed synaptic injury caused by TIA.
Animals ; Annexin A1/metabolism* ; CX3C Chemokine Receptor 1/metabolism* ; Chemokine CX3CL1 ; Cognition ; Dendritic Spines/metabolism* ; Ischemic Attack, Transient ; Mice ; Microglia/metabolism*

The back-propagating action potential (bpAP) is crucial for neuronal signal integration and synaptic plasticity in dendritic trees. Its properties (velocity and amplitude) can be affected by dendritic morphology. Due to limited spatial resolution, it has been difficult to explore the specific propagation process of bpAPs along dendrites and examine the influence of dendritic morphology, such as the dendrite diameter and branching pattern, using patch-clamp recording. By taking advantage of Optopatch, an all-optical electrophysiological method, we made detailed recordings of the real-time propagation of bpAPs in dendritic trees. We found that the velocity of bpAPs was not uniform in a single dendrite, and the bpAP velocity differed among distinct dendrites of the same neuron. The velocity of a bpAP was positively correlated with the diameter of the dendrite on which it propagated. In addition, when bpAPs passed through a dendritic branch point, their velocity decreased significantly. Similar to velocity, the amplitude of bpAPs was also positively correlated with dendritic diameter, and the attenuation patterns of bpAPs differed among different dendrites. Simulation results from neuron models with different dendritic morphology corresponded well with the experimental results. These findings indicate that the dendritic diameter and branching pattern significantly influence the properties of bpAPs. The diversity among the bpAPs recorded in different neurons was mainly due to differences in dendritic morphology. These results may inspire the construction of neuronal models to predict the propagation of bpAPs in dendrites with enormous variation in morphology, to further illuminate the role of bpAPs in neuronal communication.
Action Potentials/physiology* ; Dendrites/physiology* ; Neurons/physiology* ; Neuronal Plasticity ; Pyramidal Cells/physiology*

Diffusion tensor imaging technology can provide information on the white matter of the brain, which can be used to explore changes in brain tissue structure, but it lacks the specific description of the microstructure information of brain tissue. The neurite orientation dispersion and density imaging make up for its shortcomings. But in order to accurately estimate the brain microstructure, a large number of diffusion gradients are needed, and the calculation is complex and time-consuming through maximum likelihood fitting. Therefore, this paper proposes a kind of microstructure parameters estimation method based on the proximal gradient network, which further avoids the classic fitting paradigm. The method can accurately estimate the parameters while reducing the number of diffusion gradients, and achieve the purpose of imaging quality better than the neurite orientation dispersion and density imaging model and accelerated microstructure imaging via convex optimization model.
Brain/diagnostic imaging* ; Diffusion Magnetic Resonance Imaging ; Diffusion Tensor Imaging ; Neurites ; White Matter

OBJECTIVE: To assess the value of Ploton silver staining and phalloidin-iFlour 488 staining in observation of the morphology of osteocyte dendrites of mice at different developmental stages. METHODS: The humerus and femurs were harvested from mice at 0 (P0), 5 (P5), 15 (P15), 21 (P21), 28 (P28), and 35 days (P35) after birth to prepare cryo-sections and paraffin sections. HE staining of P35 mouse femur sections served as a reference for observing osteocytes in the trabecular bone and cortical bone. The humeral sections at different developmental stages were stained with Ploton silver staining to observe the morphology of osteocytes and canaliculi, and the canalicular lengths in the cortical and trabecular bones of the humerus of the mice in each developmental stage were recorded. The cryo-sections of the humerus from P10 and P15 mice were stained with phalloidin iFlour-488 to observe the morphology of osteocytes and measurement of the length of osteocyte dendrites in the cortical bone. RESULTS: In the trabecular bone of the humerus of P0-P15 mice, Ploton silver staining only visualized the outline of the osteocytes, and the morphology of the canaliculi was poorly defined. In P21 or older mice, Ploton silver staining revealed the morphology of the trabecular bone osteocytes and the canaliculi, which were neatly arranged and whose lengths increased significantly with age (P21 CONCLUSIONS Mouse osteocyte dendrites elongate progressively and their arrangement gradually becomes regular with age. Ploton silver staining can clearly visualize the morphology of the osteocytes and the canaliculi in adult mice but not in mice in early stages of development. Phalloidin iFlour-488 staining for labeling the cytoskeleton can be applied for mouse osteocytes at all developmental stages and allows morphological observation of mouse osteocytes in early developmental stages.
Animals ; Bone and Bones ; Dendrites ; Mice ; Osteocytes ; Phalloidine ; Silver Staining

Alzheimer's disease (AD) is the most common neurodegenerative disorder causing dementia worldwide, and is mainly characterized by aggregated β-amyloid (Aβ). Increasing evidence has shown that plant extracts have the potential to delay AD development. The plant sterol β-Sitosterol has a potential role in inhibiting the production of platelet Aβ, suggesting that it may be useful for AD prevention. In the present study, we aimed to investigate the effect and mechanism of β-Sitosterol on deficits in learning and memory in amyloid protein precursor/presenilin 1 (APP/PS1) double transgenic mice. APP/PS1 mice were treated with β-Sitosterol for four weeks, from the age of seven months. Brain Aβ metabolism was evaluated using ELISA and Western blotting. We found that β-Sitosterol treatment can improve spatial learning and recognition memory ability, and reduce plaque load in APP/PS1 mice. β-Sitosterol treatment helped reverse dendritic spine loss in APP/PS1 mice and reversed the decreased hippocampal neuron miniature excitatory postsynaptic current frequency. Our research helps to explain and support the neuroprotective effect of β-Sitosterol, which may offer a novel pharmaceutical agent for the treatment of AD. Taken together, these findings suggest that β-Sitosterol ameliorates memory and learning impairment in APP/PS1 mice and possibly decreases Aβ deposition.
Alzheimer Disease ; Amyloid ; Animals ; Blood Platelets ; Blotting, Western ; Brain ; Cognition Disorders ; Dementia ; Dendritic Spines ; Enzyme-Linked Immunosorbent Assay ; Excitatory Postsynaptic Potentials ; Learning ; Memory ; Metabolism ; Mice ; Mice, Transgenic ; Neurodegenerative Diseases ; Neurons ; Neuroprotective Agents ; Plant Extracts ; Plants ; Plaque, Amyloid ; Spatial Learning

Neurons are the structural and functional unit of the nervous system. Precisely regulated dendrite morphogenesis is the basis of neural circuit assembly. Numerous studies have been conducted to explore the regulatory mechanisms of dendritic morphogenesis. According to their action regions, we divide them into two categories: the intrinsic and extrinsic regulators of neuronal dendritic morphogenesis. Intrinsic factors are cell type-specific transcription factors, actin polymerization or depolymerization regulators and regulators of the secretion or endocytic pathways. These intrinsic factors are produced by neuron itself and play an important role in regulating the development of dendrites. The extrinsic regulators are either secreted proteins or transmembrane domain containing cell adhesion molecules. They often form receptor-ligand pairs to mediate attractive or repulsive dendritic guidance. In this review, we summarize recent findings on the intrinsic and external molecular mechanisms of dendrite morphogenesis from multiple model organisms, including , and mice. These studies will provide a better understanding on how defective dendrite development and maintenance are associated with neurological diseases.
Animals ; Caenorhabditis elegans ; cytology ; Dendrites ; Mice ; Morphogenesis ; Nervous System Diseases ; physiopathology ; Neurons ; cytology ; Transcription Factors ; metabolism

OBJECTIVE: Synaptic vesicle mobilization and neurite outgrowth regulation molecules were examined in modulation of effects of methylphenidate (MPH) in Spontaneous Hypertensive Rats (SHRs), a model for attention-deficit hyperactivity disorder (ADHD). METHODS: We compared the changes in the protein expression level of Cyclin dependent kinase 5 (Cdk5) and molecular substrates of Cdk5; tropomyosin receptor kinase B (TrkB), syntaxin 1A (STX1A) and synaptosomal-associated protein 25 (SNAP25). Comparisons were made in prefrontal cortex of vehicle (distilled water i.p. for 7 days)-treated SHRs, vehicle-treated Wistar Kyoto Rats (WKYs) and MPH (2 mg/kg i.p. for 7 days) treated SHRs. RESULTS: The Cdk5 level of vehicle-treated SHRs was significantly decreased compared to the Cdk5 level of vehicle-treated WKY rats, but was restored to the expression level of vehicle-treated WKYs in MPH-treated SHR. The ratio of p25/p35 was significantly decreased in MPH-treated SHR compared to vehicle-treated SHR. Moreover, TrkB, STX1A and SNAP25 of vehicle-treated SHRs were significantly decreased compared to vehicle-treated WKY rats, but were restored to the expression level of vehicle-treated WKYs in MPH-treated SHR. CONCLUSION: The results show that Cdk5, TrkB, STX1A, and SNAP25 were involved in the modulation of MPH effects in prefrontal cortex of SHRs and play important role in treatment of ADHD.
Animals ; Cyclin-Dependent Kinase 5 ; Methylphenidate ; Neurites ; Phosphotransferases ; Prefrontal Cortex ; Rats ; Rats, Inbred WKY ; Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins ; Synaptic Vesicles ; Synaptosomal-Associated Protein 25 ; Syntaxin 1 ; Tropomyosin ; Water