Autism Spectrum Disorder (ASD) is marked by early-onset neurodevelopmental anomalies, yet the temporal dynamics of genetic contributions to these processes remain insufficiently understood. This study aimed to elucidate the role of the Shank3 gene, known to be associated with monogenic causes of autism, in early developmental processes to inform the timing and mechanisms for potential interventions for ASD. Utilizing the Shank3B knockout (KO) mouse model, we examined Shank3 expression and its impact on neuronal maturation through Golgi staining for dendritic morphology and electrophysiological recordings to measure synaptic function in the anterior cingulate cortex (ACC) across different postnatal stages. Our longitudinal analysis revealed that, while Shank3B KO mice displayed normal neuronal morphology at one week postnatal, significant impairments in dendritic growth and synaptic activity emerged by two to three weeks. These findings highlight the critical developmental window during which Shank3 is essential for neuronal and synaptic maturation in the ACC.
Animals ; Nerve Tissue Proteins/metabolism* ; Mice, Knockout ; Dendrites/metabolism* ; Mice ; Synapses/metabolism* ; Gyrus Cinguli/metabolism* ; Male ; Mice, Inbred C57BL ; Autism Spectrum Disorder/genetics* ; Microfilament Proteins

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*

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: 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

PURPOSE: We report a case of herpes simplex keratitis after Descemet membrane endothelial keratoplasty (DMEK). CASE SUMMARY: A 67-year-old male underwent DMEK in his left eye due to pseudophakic bullous keratopathy. One week after DMEK, re-bubbling was performed due to partial detachment of Descemet's membrane at the corneal periphery. After re-bubbling, the cornea remained clear and the patient's visual acuity gradually improved. Two months after DMEK, the patient presented with mild discomfort and decreased visual acuity. The cornea showed an irregular, narrow dendrite with an epithelial defect and surrounding opacity. After confirming that Descemet's membrane was attached, the patient was started on oral valacyclovir for suspected herpes keratitis. Herpes simplex virus type 1 was eventually identified by polymerase chain reaction. The corneal lesion resolved after three weeks of antiviral treatment. CONCLUSIONS: Similar to penetrating keratoplasty, DMEK can trigger outbreaks of herpes simplex keratitis. Herpes simplex keratitis should remain on the clinician's differential diagnosis for patients who present with a corneal epithelial irregularity and decreased visual acuity following DMEK.
Aged ; Cornea ; Corneal Transplantation ; Dendrites ; Descemet Membrane ; Diagnosis, Differential ; Disease Outbreaks ; Herpes Simplex ; Herpesvirus 1, Human ; Humans ; Keratitis ; Keratitis, Herpetic ; Keratoplasty, Penetrating ; Male ; Polymerase Chain Reaction ; Visual Acuity

It is known that top-down associative inputs terminate on distal apical dendrites in layer 1 while bottom-up sensory inputs terminate on perisomatic dendrites of layer 2/3 pyramidal neurons (L2/3 PyNs) in primary sensory cortex. Since studies on synaptic transmission in layer 1 are sparse, we investigated the basic properties and cholinergic modulation of synaptic transmission in layer 1 and compared them to those in perisomatic dendrites of L2/3 PyNs of rat primary visual cortex. Using extracellular stimulations of layer 1 and layer 4, we evoked excitatory postsynaptic current/potential in synapses in distal apical dendrites (L1-EPSC/L1-EPSP) and those in perisomatic dendrites (L4-EPSC/L4-EPSP), respectively. Kinetics of L1-EPSC was slower than that of L4-EPSC. L1-EPSC showed presynaptic depression while L4-EPSC was facilitating. In contrast, inhibitory postsynaptic currents showed similar paired-pulse ratio between layer 1 and layer 4 stimulations with depression only at 100 Hz. Cholinergic stimulation induced presynaptic depression by activating muscarinic receptors in excitatory and inhibitory synapses to similar extents in both inputs. However, nicotinic stimulation enhanced excitatory synaptic transmission by ~20% in L4-EPSC. Rectification index of AMPA receptors and AMPA/NMDA ratio were similar between synapses in distal apical and perisomatic dendrites. These results provide basic properties and cholinergic modulation of synaptic transmission between distal apical and perisomatic dendrites in L2/3 PyNs of the visual cortex, which might be important for controlling information processing balance depending on attentional state.
Animals ; Automatic Data Processing ; Dendrites ; Depression ; Inhibitory Postsynaptic Potentials ; Kinetics ; Pyramidal Cells ; Rats ; Receptors, AMPA ; Receptors, Muscarinic ; Synapses ; Synaptic Transmission ; Visual Cortex

The thalamus is a brain structure known to modulate sensory information before relaying to the cortex. The unique ability of a thalamocortical (TC) neuron to switch between the high frequency burst firing and single spike tonic firing has been implicated to have a key role in sensory modulation including pain. Of the two firing modes, burst firing, especially maintaining certain burst firing properties, was suggested to be critical in controlling nociceptive behaviors. Therefore, understanding the factors that influence burst firing properties would offer important insight into understanding sensory modulation. Using computational modeling, we investigated how the balance of excitatory and inhibitory inputs into a TC neuron influence TC bursting properties. We found that intensity of inhibitory inputs and the timing of excitatory input delivery control the dynamics of bursting properties. Then, to reflect a more realistic model, excitatory inputs delivered at different dendritic locations—proximal, intermediate, or distal—of a TC neuron were also investigated. Interestingly, excitatory input delivered into a distal dendrite, despite the furthest distance, had the strongest influence in shaping burst firing properties, suggesting that not all inputs equally contribute to modulating TC bursting properties. Overall, the results provide computational insights in understanding the detailed mechanism of the factors influencing temporal pattern of thalamic bursts.
Brain ; Calcium Channels, T-Type ; Computational Biology ; Dendrites ; Fires ; Neurons ; Sensory Gating ; Thalamus

In this study, change of optical properties and microstructure of an Ag-Pd-In alloy according to Ag content was investigated. For this purpose, specimen alloys were prepared by adding 0–100 wt.% of Ag to the 50Pd-50In (wt.%) alloy. When the content of Ag was more than 40 wt.%, the color difference with pure gold specimen was increased(p < 0.001). L* value increased as the Ag content of the specimen increased, but a* and b* value increased until the addition of 20 wt.% Ag, and then decreased with increasing Ag content(p < 0.001). Ag-free specimen was single phase in the as-cast state, but when the content of Ag was more than 20 wt.%, the phase separation occurred and two phases of matrix and dendrite or granular structure were confirmed. The dendrite or granular structure was composed of the InPd phase, and the matrix was composed of the Ag-rich phase. From these results, it can be concluded that the specimens with Ag content of 20–70 wt.% have the Ag-rich matrix which has a high L* value and low a* and b* value, and have the dendrite structure which has a low L* value and high a* and b* value. As the content of Ag increased, the color changed from light yellow to silver white due to the increase in the ratio of the matrix to the dendrite or granular structure.
Alloys ; Dendrites ; Silver

GABAergic control over dopamine (DA) neurons in the substantia nigra is crucial for determining firing rates and patterns. Although GABA activates both GABA(A) and GABA(B) receptors distributed throughout the somatodendritic tree, it is currently unclear how regional GABA receptors in the soma and dendritic compartments regulate spontaneous firing. Therefore, the objective of this study was to determine actions of regional GABA receptors on spontaneous firing in acutely dissociated DA neurons from the rat using patch-clamp and local GABA-uncaging techniques. Agonists and antagonists experiments showed that activation of either GABA(A) receptors or GABA(B) receptors in DA neurons is enough to completely abolish spontaneous firing. Local GABA-uncaging along the somatodendritic tree revealed that activation of regional GABA receptors limited within the soma, proximal, or distal dendritic region, can completely suppress spontaneous firing. However, activation of either GABA(A) or GABA(B) receptor equally suppressed spontaneous firing in the soma, whereas GABA(B) receptor inhibited spontaneous firing more strongly than GABA(A) receptor in the proximal and distal dendrites. These regional differences of GABA signals between the soma and dendritic compartments could contribute to our understanding of many diverse and complex actions of GABA in midbrain DA neurons.
Animals ; Carisoprodol ; Dendrites ; Dopamine* ; Dopaminergic Neurons* ; Fires* ; gamma-Aminobutyric Acid ; Mesencephalon ; Neurons ; Rats ; Receptors, GABA ; Receptors, GABA-A ; Substantia Nigra ; Trees

Dopaminergic amacrine cells (DACs) are among the most well-characterized neurons in the mammalian retina, and their connections to AII amacrine cells have been described in detail. However, the stratification of DAC dendrites differs based on their location in the inner plexiform layer (IPL), raising the question of whether all AII lobules are modulated by dopamine release from DACs. The present study aimed to clarify the relationship between DACs and AII amacrine cells, and to further elucidate the role of dopamine at synapses with AII amacrine cell. In the rabbit retina, DAC dendrites were observed in strata 1, 3, and 5 of the IPL. In stratum 1, most DAC dendritic varicosities—the presumed sites of neurotransmitter release—made contact with the somata and lobular appendages of AII amacrine cells. However, most lobular appendages of AII amacrine cells localized within stratum 2 of the IPL exhibited little contact with DAC varicosities. In addition, double- or triple-labeling experiments revealed that DACs did not express the GABAergic neuronal markers anti-GABA, vesicular GABA transporter, or glutamic acid decarboxylase. These findings suggest that the lobular appendages of AII amacrine cells are involved in at least two different circuits. We speculate that the circuit associated with stratum 1 of the IPL is modulated by DACs, while that associated with stratum 2 is modulated by unknown amacrine cells expressing a different neuroactive substance. Our findings further indicate that DACs in the rabbit retina do not use GABA as a neurotransmitter, in contrast to those in other mammals.
Amacrine Cells* ; Dendrites ; Dopamine ; GABAergic Neurons ; gamma-Aminobutyric Acid ; Glutamate Decarboxylase ; Immunohistochemistry* ; Mammals ; Neurons ; Neurotransmitter Agents ; Retina* ; Synapses