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Voltage distribution in sub-cellular micro-domains such as neuronal synapses, small protrusions, or dendritic spines regulates the opening and closing of ionic channels, energy production, and thus, cellular homeostasis and excitability. Yet how voltage changes at such a small scale in vivo remains challenging due to the experimental diffraction limit, large signal fluctuations, and the still limited resolution of fast voltage indicators. Here, we study the voltage distribution in nano-compartments using a computational approach based on the Poisson–Nernst–Planck equations for the electro-diffusion motion of ions, where inward and outward fluxes are generated between channels. We report a current–voltage (I–V) logarithmic relationship generalizing Nernst law that reveals how the local membrane curvature modulates the voltage. We further find that an influx current penetrating a cellular electrolyte can lead to perturbations from tens to hundreds of nanometers deep, depending on the local channel organization. Finally, we show that the neck resistance of dendritic spines can be completely shunted by the transporters located on the head boundary, facilitating ionic flow. To conclude, we propose that voltage is regulated at a subcellular level by channel organization, membrane curvature, and narrow passages. [ABSTRACT FROM AUTHOR]

Sevoflurane induces developmental neurotoxicity in mice; however, the underlying mechanisms remain unclear. Triggering receptor expressed on myeloid cells 2 (TREM2) is essential for microglia-mediated synaptic refinement during the early stages of brain development. We explored the effects of TREM2 on dendritic spine pruning during sevoflurane-induced developmental neurotoxicity in mice. Mice were anaesthetized with sevoflurane on postnatal days 6, 8, and 10. Behavioral performance was assessed using the open field test and Morris water maze test. Genetic knockdown of TREM2 and overexpression of TREM2 by stereotaxic injection were used for mechanistic experiments. Western blotting, immunofluorescence, electron microscopy, three-dimensional reconstruction, Golgi staining, and whole-cell patch-clamp recordings were performed. Sevoflurane exposures upregulated the protein expression of TREM2, increased microglia-mediated pruning of dendritic spines, and reduced synaptic multiplicity and excitability of CA1 neurons. TREM2 genetic knockdown significantly decreased dendritic spine pruning, and partially aggravated neuronal morphological abnormalities and cognitive impairments in sevoflurane-treated mice. In contrast, TREM2 overexpression enhanced microglia-mediated pruning of dendritic spines and rescued neuronal morphological abnormalities and cognitive dysfunction. TREM2 exerts a protective role against neurocognitive impairments in mice after neonatal exposures to sevoflurane by enhancing microglia-mediated pruning of dendritic spines in CA1 neurons. This provides a potential therapeutic target in the prevention of sevoflurane-induced developmental neurotoxicity.

Cognitive dysfunction and dementia are critical symptoms of Lewy Body dementias (LBD). Specifically, alpha-synuclein (αSyn) accumulation in the hippocampus leading to synaptic dysfunction is linked to cognitive deficits in LBD. Here, we investigated the pathological impact of αSyn on hippocampal neurons. We report that either αSyn overexpression or αSyn pre-formed fibrils (PFFs) treatment triggers the formation of cofilin-actin rods, synapse disruptors, in cultured hippocampal neurons and in the hippocampus of synucleinopathy mouse models and of LBD patients. In vivo, cofilin pathology is present concomitantly with synaptic impairment and cognitive dysfunction. Rods generation prompted by αSyn involves the co-action of the cellular prion protein (PrPC) and the chemokine receptor 5 (CCR5). Importantly, we show that CCR5 inhibition, with a clinically relevant peptide antagonist, reverts dendritic spine impairment promoted by αSyn. Collectively, we detail the cellular and molecular mechanism through which αSyn disrupts hippocampal synaptic structure and we identify CCR5 as a novel therapeutic target to prevent synaptic impairment and cognitive dysfunction in LBD.

Synaptic plasticity is important for learning and memory formation; it describes the strengthening or weakening of connections between synapses. The postsynaptic part of excitatory synapses resides in dendritic spines, which are small protrusions on the dendrites. One of the key features of synaptic plasticity is its correlation with the size of these spines. A long-lasting synaptic strength increase [long-term potentiation (LTP)] is only possible through the reconfiguration of the actin spine cytoskeleton. Here, we develop an experimentally informed three-dimensional computational model in a moving boundary framework to investigate this reconfiguration. Our model describes the reactions between actin and actin-binding proteins leading to the cytoskeleton remodeling and their effect on the spine membrane shape to examine the spine enlargement upon LTP. Moreover, we find that the incorporation of perisynaptic elements enhances spine enlargement upon LTP, exhibiting the importance of accounting for these elements when studying structural LTP. Our model shows adaptation to repeated stimuli resulting from the interactions between spine proteins and mechanical forces.

The outgrowth and stabilization of nascent dendritic spines are crucial processes underlying learning and memory. Most new spines retract shortly after growth; only a small subset is stabilized and integrated into the new circuit connections that support learning. New spine stabilization has been shown to rely upon activity-dependent molecular mechanisms that also contribute to long-term potentiation (LTP) of synaptic strength. Indeed, disruption of the activity-dependent targeting of the kinase CaMKIIα to the GluN2B subunit of the NMDA-type glutamate receptor disrupts both LTP and activity-dependent stabilization of new spines. Yet it is not known which of CaMKIIα's many enzymatic and structural functions are important for new spine stabilization. Here, we used two-photon imaging and photolysis of caged glutamate to monitor the activity-dependent stabilization of new dendritic spines on hippocampal CA1 neurons from mice of both sexes in conditions where CaMKIIα functional and structural interactions were altered. Surprisingly, we found that inhibiting CaMKIIα kinase activity either genetically or pharmacologically did not impair activity-dependent new spine stabilization. In contrast, shRNA knockdown of CaMKIIα abolished activity-dependent new spine stabilization, which was rescued by co-expressing shRNA-resistant full-length CaMKIIα, but not by a truncated monomeric CaMKIIα. Notably, overexpression of phospho-mimetic CaMKIIα-T286D, which exhibits activity-independent targeting to GluN2B, enhanced basal new spine survivorship in the absence of additional glutamatergic stimulation, even when kinase activity was disrupted. Together, our results support a model in which nascent dendritic spine stabilization requires structural and scaffolding interactions mediated by dodecameric CaMKIIα that are independent of its enzymatic activities.

Neuronal connectivity is essential for adaptive brain responses and can be modulated by dendritic spine plasticity and the intrinsic excitability of individual neurons. Dysregulation of these processes can lead to aberrant neuronal activity, which has been associated with numerous neurological disorders including autism, epilepsy, and Alzheimer's disease. Nonetheless, the molecular mechanisms underlying abnormal neuronal connectivity remain unclear. We previously found that the serine/threonine kinase Microtubule Affinity Regulating Kinase 2 (MARK2), also known as Partitioning Defective 1b (Par1b), is important for the formation of dendritic spines in vitro. However, despite its genetic association with several neurological disorders, the in vivo impact of MARK2 on neuronal connectivity and cognitive functions remains unclear. Here, we demonstrate that the loss of MARK2 in vivo results in changes to dendritic spine morphology, which in turn leads to a decrease in excitatory synaptic transmission. Additionally, the loss of MARK2 produces substantial impairments in learning and memory, reduced anxiety, and defective social behavior. Notably, MARK2 deficiency results in heightened seizure susceptibility. Consistent with this observation, electrophysiological analysis of hippocampal slices indicates underlying neuronal hyperexcitability in MARK2‐deficient neurons. Finally, RNAseq analysis reveals transcriptional changes in genes regulating synaptic transmission and ion homeostasis. These results underscore the in vivo role of MARK2 in governing synaptic connectivity, neuronal excitability, and cognitive functions. [ABSTRACT FROM AUTHOR]

Anxiety is a prominent non‐motor symptom of Parkinson's disease (PD). Changes in the B‐spectrum recordings in PD patients of the prefrontal cortex correlate with increased anxiety. Using a rodent model of PD, we reported alterations in glutamate synapses in the striatum and substantia nigra following dopamine (DA) loss. We hypothesize that DA loss will result in increased anxiety‐related behaviours and that this will be associated with alterations in glutamate synapses and transporters within the medial prefrontal cortex (mPFC). Following 4 weeks of progressive 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) administration, there was an increase in anxiety‐related behaviours and a 78% decrease in plasma corticosterone levels versus the vehicle (VEH)‐treated mice. This was associated with a 30% decrease in the density of dendritic spines in Layers Il/Ill, and a 53% decrease in the density of glutamate immuno‐gold labelling within vesicular glutamate transporter 1 (Vglut1)‐labelled nerve terminals and spines, with no change within vesicular glutamate transporter 2 (Vglut2) positive terminals/spines in the MPTP versus VEH groups. Our prior work determined that a decrease in striatal glutamate terminal density was associated with an increase in extracellular glutamate levels. There was an increase in protein expression of Vglut1 (40%), Vglut2 (37%) and glutamate aspartate transporter (GLAST) (225%), and a decrease in glutamate transporter 1 (GLT‐1) (50%) and excitatory amino acid carrier 1 (EAAC1) (51%), in the MPTP versus VEH groups within the mPFC. These data suggest that the decrease in dendritic spines within the mPFC following nigrostriatal DA loss may be due to increased extracellular glutamate levels (decrease in glutamate transporters), leading to an increase in anxiety‐related behaviours. [ABSTRACT FROM AUTHOR]

Introduction: Erlotinib is an epidermal growth factor receptor (EGFR) inhibitor that is approved by the FDA to treat non-small cell lung cancer (NSCLC). Several membrane receptors, including EGFR, interact with amyloid b (Ab), raising the possibility that erlotinib could have therapeutic effects on Alzheimer's disease (AD). However, the effects of erlotinib on Ab/tau-related pathology and cognitive function in mouse models of AD and its mechanisms of action have not been examined in detail. Methods: To investigate the effects of erlotinib on cognitive function and AD pathology, 3 to 6-month-old PS19 mice and 3 to 3.5-month-old 5xFAD mice and WT mice were injected with vehicle (5% DMSO + 10% PEG + 20% Tween80 + 65% D.W.) or erlotinib (20 mg/kg, i.p.) daily for 14 or 21 days. Then, behavioral tests, Golgi staining, immunofluorescence staining, western blotting ELISA, and real-time PCR were conducted. Results and discussion: We found that erlotinib significantly enhanced shortterm spatial memory and dendritic spine formation in 6-month-old P301S tau transgenic (PS19) mice. Importantly, erlotinib administration reduced tau phosphorylation at Ser202/Thr205 (AT8) and Thr231 (AT180) and further aggregation of tau into paired helical fragments (PHFs) and neurofibrillary tangles (NFTs) in 3-month-old and/or 6-month-old PS19 mice by suppressing the expression of the tau kinase DYRK1A. Moreover, erlotinib treatment decreased astrogliosis in 6-month-old PS19 mice and reduced proinflammatory responses in primary astrocytes (PACs) from PS19 mice. In 3- to 3.5-month-old 5xFAD mice, erlotinib treatment improved short-term spatial memory and hippocampal dendritic spine number and diminished Ab plaque deposition and tau hyperphosphorylation. Furthermore, erlotinib-treated 5xFAD mice exhibited significant downregulation of astrocyte activation, and treating PACs from 5xFAD mice with erlotinib markedly reduced cxcl10 (reactive astrocyte marker) and gbp2 (A1 astrocyte marker) mRNA levels and proinflammatory cytokine mRNA and protein levels. Taken together, our results suggest that erlotinib regulates tau/Ab-induced AD pathology, cognitive function, and Ab/tau-evoked astrogliosis and therefore could be a potent therapeutic drug for ameliorating AD symptoms. [ABSTRACT FROM AUTHOR]

High‐frequency oscillatory activity in cognition‐related neural circuits during wakefulness consistently induces the growth of dendritic spines and axonal terminals. Although these structural changes are essential for cognitive functions, it is hypothesized that if these newly expanded structures fail to establish functional connections, they may become superfluous. Sleep is believed to facilitate the reduction of such redundant structures to maintain neural homeostasis. However, the mechanisms underlying this pruning process during sleep remain poorly understood. In this study, that melatonin type 3 receptors (MT3Rs) are selectively expressed in the stellate neurons of the medial entorhinal cortex (MEC) is demonstrated, an area where high melatonin levels are detected during sleep. Activation of MT3Rs during sleep initiates the shrinkage of dendritic spines in stellate neurons by downregulating neural network activity and dephosphorylating synaptic proteins in the MEC. This process is disrupted when MT3R expression is knocked down or when MT3Rs are blocked during sleep. Notably, interference with MT3Rs in the MEC during sleep impairs the acquisition of spatial memory but does not affect object memory acquisition following sleep. These findings reveal novel molecular mechanisms involving melatonin and MT3Rs in the regulation of dendritic spine shrinkage during sleep, which is crucial for the acquisition and consolidation of spatial memory. [ABSTRACT FROM AUTHOR]

Background: Nicotine dependence is associated with glutamatergic neurotransmission in the caudate and putamen (CPu) of the forebrain which includes alterations in the structure of dendritic spines at glutamate synapses. These changes after nicotine exposure can lead to the development of habitual behaviors such as smoking. The present study investigated the hypothesis that cofilin, an actin-binding protein that is linked to the GluN2B subunits of N-methyl-D-aspartate (NMDA) receptors regulates the morphology of dendritic spines in the neurons of the CPu after repeated exposure to nicotine. Results: Adult male rats received subcutaneous injections of nicotine (0.3 mg/kg/day) or vehicle for seven consecutive days. DiI staining was conducted to observe changes in dendritic spine morphology. Repeated subcutaneous injections of nicotine decreased the phosphorylation of cofilin while increasing the formation of thin spines and filopodia in the dendrites of medium spiny neurons (MSN) in the CPu of rats. Bilateral intra-CPu infusion of the cofilin inhibitor, cytochalasin D (12.5 µg/µL/side), restored the thin spines and filopodia from mushroom types after repeated exposure to nicotine. Similar results were obtained from the bilateral intra-CPu infusion of the selective GluN2B subunit antagonist, Ro 25-6981 (4 µM/µL/side). Bilateral intra-CPu infusion of cytochalasin D that interferes with the actin-cofilin interaction attenuated the repeated nicotine-induced increase in locomotor sensitization in rats. Conclusions: These findings suggest that active cofilin alters the structure of spine heads from mushroom to thin spine/filopodia by potentiating actin turnover, contributing to behavioral sensitization after nicotine exposure. [ABSTRACT FROM AUTHOR]

Alzheimer disease (AD) is characterized by progressive loss of memory. Synaptic loss is now the best correlate of cognitive dysfunction in patients with Alzheimer's disease. Thus, restoration or limitation of synapse loss is a promising strategy for pharmacotherapy of AD. N–N substituted piperazines are widely used chemical compounds for drug interventions to treat different illnesses including CNS diseases such as drug abuse, mental and anxiety disorders. Piperazine derivatives are small molecules that are usually well tolerated and cross blood brain barrier (BBB). Thus, disubstituted piperazines are good tools for searching and developing novel disease-modifying drugs. Previously, we have determined the piperazine derivative, 51164, as an activator of TRPC6 in dendritic spines. We have demonstrated synaptoprotective properties of 51164 in AD mouse models. However, 51164 was not able to cross BBB. Within the current study, we identified a novel piperazine derivative, cmp2, that is structurally similar to 51164 but is able to cross BBB. Cmp2 binds central part of monomeric TRPC6 in similar way as hypeforin does. Cmp2 selectively activates TRPC6 but not structurally related TRPC3 and TRPC7. Novel piperazine derivative exhibits synaptoprotective properties in culture and slices and penetrates the BBB. In vivo study indicated cmp2 (10 mg/kg I.P.) reversed deficits in synaptic plasticity in the 5xFAD mice. Thus, we suggest that cmp2 is a novel lead compound for drug development. The mechanism of cmp2 action is based on selective TRPC6 stimulation and it is expected to treat synaptic deficiency in hippocampal neurons. [ABSTRACT FROM AUTHOR]

Acute traumatic event exposure is a direct cause of post-traumatic stress disorder (PTSD). Amygdala is suggested to be associated with the development of PTSD. In our previous findings, different activation patterns of GABAergic neurons and glutamatergic neurons in early or late stages after stress were found. However, the neural plastic mechanism underlying the role of basolateral amygdala (BLA) in post-traumatic stress disorder remains unclear. Therefore, this study mainly aimed at investigating time-dependent morphologic and electrophysiological changes in BLA during the development of PTSD. We used single prolonged stress (SPS) procedure to establish PTSD model of rats. The rats showed no alterations in anxiety behavior as well as in dendritic spine density or synaptic transmission in BLA 1 day after SPS. However, 10 days after SPS, rats showed enhancement of anxiety behavior, and spine density and frequency of miniature excitatory and inhibitory postsynaptic currents in BLA. Our results suggested that after traumatic stress, BLA displayed delayed increase in both spinogenesis and synaptic transmission, which seemed to facilitate the development of PTSD. [ABSTRACT FROM AUTHOR]

For a subset of individuals known as sign‐trackers, discrete Pavlovian cues associated with rewarding stimuli can acquire incentive properties and exert control over behaviour. Because responsiveness to cues is a feature of various neuropsychiatric conditions, rodent models of sign‐tracking may prove useful for exploring the neurobiology of individual variation in psychiatric vulnerabilities. Converging evidence points towards the involvement of dopaminergic neurotransmission in the nucleus accumbens core (NAc) in the development of sign‐tracking, yet whether this phenotype is associated with specific accumbal postsynaptic properties is unknown. Here, we examined dendritic spine structural organisation, as well as presynaptic and postsynaptic markers of activity, in the NAc core of male and female rats following a Pavlovian‐conditioned approach procedure. In contrast to our prediction that cue re‐exposure would increase spine density, experiencing the discrete lever‐cue without reward delivery resulted in lower spine density than control rats for which the lever was unpaired with reward during training; this effect was tempered in the most robust sign‐trackers. Interestingly, this same behavioural test (lever presentation without reward) resulted in increased levels of a marker of presynaptic activity (synaptophysin), and this effect was greatest in female rats. Whilst some behavioural differences were observed in females during initial Pavlovian training, final conditioning scores did not differ from males and were unaffected by the oestrous cycle. This work provides novel insights into how conditioning impacts the neuronal plasticity of the NAc core, whilst highlighting the importance of studying the behaviour and neurobiology of both male and female rats. [ABSTRACT FROM AUTHOR]

The motor cortex is essential for controlling the flexible movements underlying complex behaviors. Behavioral flexibility involves the ability to integrate and refine new movements, thereby expanding an animal’s repertoire. This review discusses recent strides in motor learning mechanisms across spatial and temporal scales, describing how neural networks are remodeled at the level of synapses, cell types, and circuits and across time as animals’ learn new skills. It highlights how changes at each scale contribute to the evolving structure and function of neural circuits that accompanies the expansion and refinement of motor skills. We review new findings highlighted by advanced imaging techniques that have opened new vistas in optical physiology and neuroanatomy, revealing the complexity and adaptability of motor cortical circuits, crucial for learning and control. At the structural level, we explore the dynamic regulation of dendritic spines mediating corticocortical and thalamocortical inputs to the motor cortex. We delve into the role of perisynaptic astrocyte processes in maintaining synaptic stability during learning. We also examine the functional diversity among pyramidal neuron subtypes, their dendritic computations and unique contributions to single cell and network function. Further, we highlight how cortical activation is characterized by increased consistency and reduced strength as new movements are learned and how external inputs contribute to these changes. Finally, we consider the motor cortex’s necessity as movements unfold over long time scales. These insights will continue to drive new research directions, enhancing our understanding of motor cortical circuit transformations that underpin behavioral changes expressed throughout an animal’s life. [ABSTRACT FROM AUTHOR]

Accumulative evidence suggested that the oxytocin system plays a role in socio-emotional disorders, although its role in neuroinflammation-induced anxiety remains unclear. In the present study, anxiety-like behavior was induced in cohorts of animals through repeated lipopolysaccharide (LPS, 0.5 mg/kg, daily, Escherichia coli O55:B5) i.p. injections for seven consecutive days. These different cohorts were subsequently used for anxiety-like behavior assessment with open field test, elevated plus maze, and novelty-suppressed feeding test or for electrophysiology (EEG) recordings of miniature excitatory postsynaptic currents (mEPSCs), miniature inhibitory postsynaptic currents (mIPSCs), or local field potential (LFP) in vivo or ex vivo settings. Samples of the anterior cingulate cortex (ACC) from some cohorts were harvested to conduct immunostaining or western blotting analysis of oxytocin, oxytocin receptor, CamkII, GABA, vGAT, vGLUT2, and c-fos. The dendritic spine density was assessed by Golgi-Cox staining. Repeated LPS injections induced anxiety-like behavior with concurrent decreases of oxytocin, vGLUT2, mEPSC, dendritic spine, c-fos, membrane excitability, and EEG beta and gamma oscillations, but increased oxytocin receptor and vGAT expressions in the ACC; all these changes were ameliorated by oxytocin intranasal or local brain (via cannula) administration. Taken together, our data suggested that oxytocin system may be a therapeutic target for developing treatment to tackle neuroinflammation-induced anxiety. • Repeated LPS injections induced anxiety-like behavior. • Repeated LPS injections induced down-regulation of oxytocin in ACC. • Oxytocin system could regulate excitation and inhibition balance in ACC. • Oxytocin system may be a therapeutic target for neuroinflammation-induced anxiety. [ABSTRACT FROM AUTHOR]

Autophagy is crucial for synaptic plasticity and the architecture of dendritic spines. However, the role of autophagy in schizophrenia (SCZ) and the mechanisms through which it affects synaptic function remain unclear. In this study, we identified 995 single nucleotide polymorphisms (SNPs) across 19 autophagy-related genes that are associated with SCZ. Gene Set Enrichment Analysis (GSEA) of data from the Gene Expression Omnibus public database revealed defective autophagy in patients with SCZ. Using a maternal immune activation (MIA) rat model, we observed that autophagy was downregulated during the weaning period, and early-life activation of autophagy with rapamycin restored abnormal behaviors and electrophysiological deficits in adult rats. Additionally, inhibition of autophagy with 3-Methyladenine (3-MA) during the weaning period resulted in aberrant behaviors, abnormal electrophysiology, increased spine density, and reduced microglia-mediated synaptic pruning. Furthermore, 3-MA treatment significantly decreased the expression and synaptosomal content of complement, impaired the recognition of C3b and CR3, indicating that autophagy deficiency disrupts complement-mediated synaptic pruning. Our findings provide evidence for a significant association between SCZ and defective autophagy, highlighting a previously underappreciated role of autophagy in regulating the synaptic and behavioral deficits induced by MIA. [ABSTRACT FROM AUTHOR]

Sleep is regulated by homeostatic processes, yet the biological basis of sleep pressure that accumulates during wakefulness, triggers sleep, and dissipates during sleep remains elusive. We explored a causal relationship between cellular synaptic strength and electroencephalography delta power indicating macro-level sleep pressure by developing a theoretical framework and a molecular tool to manipulate synaptic strength. The mathematical model predicted that increased synaptic strength promotes the neuronal “down state” and raises the delta power. Our molecular tool (synapse-targeted chemically induced translocation of Kalirin-7, SYNCit-K), which induces dendritic spine enlargement and synaptic potentiation through chemically induced translocation of protein Kalirin-7, demonstrated that synaptic potentiation of excitatory neurons in the prefrontal cortex (PFC) increases nonrapid eye movement sleep amounts and delta power. Thus, synaptic strength of PFC excitatory neurons dictates sleep pressure in mammals. [ABSTRACT FROM AUTHOR]

Communication in the form of nonverbal, social vocalization, or crying is evolutionary conserved in mammals and is impaired early in human infants that are later diagnosed with autism spectrum disorder (ASD). Defects in infant vocalization have been proposed as an early sign of ASD that may exacerbate ASD development. However, the neural mechanisms associated with early communicative deficits in ASD are not known. Here, we expressed a constitutively active mutant of Rheb (RhebS16H), which is known to upregulate two ASD core pathways, mTOR complex 1 (mTORC1) and ERK1/2, in Layer (L) 2/3 pyramidal neurons of the neocortex of mice of either sex. We found that cellular mosaic expression of RhebS16H in L2/3 pyramidal neurons altered the production of isolation calls from neonatal mice. This was accompanied by an expected misplacement of neurons and dendrite overgrowth, along with an unexpected increase in spine density and length, which was associated with increased excitatory synaptic activity. This contrasted with the known decrease in spine density in RhebS16H neurons of 1-month-old mice. Reducing the levels of the actin cross-linking and adaptor protein filamin A (FLNA), known to be increased downstream of ERK1/2, attenuated dendrite overgrowth and fully restored spine properties, synaptic connectivity, and the production of pup isolation calls. These findings suggest that upper-layer cortical pyramidal neurons contribute to communicative deficits in a condition known to affect two core ASD pathways and that these mechanisms are regulated by FLNA. [ABSTRACT FROM AUTHOR]

Background: Physical symptoms and aversion induced by opioid withdrawal strongly affect the management of opioid addiction. YTH N6-methyladenosine (m6A) RNA binding protein 1 (YTHDF1), an m6A-binding protein, from the periaqueductal gray (PAG) reportedly contributes to morphine tolerance and hyperalgesia. However, the role of YTHDF1 in morphine withdrawal remains unclear. Methods: A naloxone-precipitated morphine withdrawal model was established in C57/BL6 mice or transgenic mice. YTHDF1 was knocked down via adeno-associated virus transfection. Combined with the results of the single-cell RNA sequencing analysis, the changes in morphine withdrawal somatic signs and conditioned place aversion (CPA) scores were compared when YTHDF1 originating from different neurons in the ventrolateral periaqueductal gray (vlPAG) was knocked down. We further explored the role of inflammatory factors and transcription factors related to inflammatory response in morphine withdrawal. Results: Our results revealed that YTHDF1 expression was upregulated in the vlPAG of mice with morphine withdrawal and that the knockdown of vlPAG YTHDF1 attenuated morphine withdrawal-related somatic signs and aversion. The levels of NF-κB and p-NF-κB were reduced after the inhibition of YTHDF1 in the vlPAG. YTHDF1 from vlPAG inhibitory neurons, rather than excitatory neurons, facilitated morphine withdrawal responses. The inhibition of YTHDF1 in vlPAG somatostatin (Sst)-expressing neurons relieved somatic signs of morphine withdrawal and aversion, whereas the knockdown of YTHDF1 in cholecystokinin (Cck)-expressing or parvalbumin (PV)-expressing neurons did not change morphine withdrawal-induced responses. The activity of c-fos + neurons, the intensity of the calcium signal, the density of dendritic spines, and the frequency of mIPSCs in the vlPAG, which were increased in mice with morphine withdrawal, were decreased with the inhibition of YTHDF1 from vlPAG inhibitory neurons or Sst-expressing neurons. Knockdown of NF-κB in Sst-expressing neurons also alleviated morphine withdrawal-induced responses. Conclusions: YTHDF1 originating from Sst-expressing neurons in the vlPAG is crucial for the modulation of morphine withdrawal responses, and the underlying mechanism might be related to the regulation of the expression and phosphorylation of NF-κB. [ABSTRACT FROM AUTHOR]

Exploring the relationship between neuronal loss in adult visual cortex and its consequential changes in synaptic connection provides experimental evidence to elucidate impaired visual function upon traumatic brain injury. The primary visual cortex (V1) of 8-week-old C57BL/6 mice was sparsely infected with adeno-associated viruses (AAVs) encoding diphtheria toxin A (DTA) to induce neuronal apoptosis. Neuronal number and dendritic spine morphology of surviving pyramidal neurons in layers 2-4 of visual cortex were analyzed using immunofluorescence staining, Golgi staining and confocal microscopy after four weeks post-injection. Through stereotactic injection of different titers (E+11-13) of DTA-expressing viruses, mouse models were generated with various levels of neuronal loss (by 14~85%) in the adult visual cortex. The results revealed that low-titer (E+11) DTA-expressing AAV led to moderate reduction of neuronal number (by~18%, P＜0.01), mimicking the level of neuronal loss in patients with mild traumatic brain injury (16.5~2.9%). In this DTA group, while dendritic spine density of pyramidal neurons did not change in comparison to the control group, the proportion of mature spines reduced by ~19% (P＜0.0001). Neuronal loss in adult visual cortex impaired synaptic connection and probably compromised visual function in the brain. [ABSTRACT FROM AUTHOR]

Neuronal excitatory synapses are primarily located on small dendritic protrusions called spines. During synaptic plasticity underlying learning and memory, Ca2+ influx through postsynaptic NMDA-type glutamate receptors (NMDARs) initiates signaling pathways that coordinate changes in dendritic spine structure and synaptic function. During long-term potentiation (LTP), high levels of NMDAR Ca2+ influx promote increases in both synaptic strength and dendritic spine size through activation of Ca2+-dependent protein kinases. In contrast, during long-term depression (LTD), low levels of NMDAR Ca2+ influx promote decreased synaptic strength and spine shrinkage and elimination through activation of the Ca2+-dependent protein phosphatase calcineurin (CaN), which is anchored at synapses via the scaffold protein A-kinase anchoring protein (AKAP)150. In Alzheimer's disease (AD), the pathological agent amyloid-β (Aβ) may impair learning and memory through biasing NMDAR Ca2+ signaling pathways toward LTD and spine elimination. By employing AKAP150 knock-in mice of both sexes with a mutation that disrupts CaN anchoring to AKAP150, we revealed that local, postsynaptic AKAP–CaN–LTD signaling was required for Aβ-mediated impairment of NMDAR synaptic Ca2+ influx, inhibition of LTP, and dendritic spine loss. Additionally, we found that Aβ acutely engages AKAP–CaN signaling through activation of G-protein-coupled metabotropic glutamate receptor 1 (mGluR1) leading to dephosphorylation of NMDAR GluN2B subunits, which decreases Ca2+ influx to favor LTD over LTP, and cofilin, which promotes F-actin severing to destabilize dendritic spines. These findings reveal a novel interplay between NMDAR and mGluR1 signaling that converges on AKAP-anchored CaN to coordinate dephosphorylation of postsynaptic substrates linked to multiple aspects of Aβ-mediated synaptic dysfunction. [ABSTRACT FROM AUTHOR]

Accumulating evidence has shown that some hallucinogens, such as LSD, have fast and persistent effects on anxiety and depression. According to a proposed mechanism, LSD activates the TrkB and HTR2A signaling pathways, which enhance the density of neuronal dendritic spines and synaptic function, and thus promote brain function. Moreover, TrkB signaling is also known to be crucial for neural stem cell (NSC)-mediated neuroregeneration to repair dysfunctional neurons. However, the impact of LSD on neural stem cells remains to be elucidated. In this study, we observed that LSD and BDNF activated the TrkB pathway in human NSCs similarly to neurons. However, unlike BDNF, LSD did not promote NSC proliferation. These results suggest that LSD may activate an alternative mechanism to counteract the effects of BDNF-TrkB signaling on NSCs. Our findings shed light on the previously unrecognized cell type-specificity of LSD. This could be crucial for deepening our understanding of the mechanisms underlying the effects of LSD. [ABSTRACT FROM AUTHOR]

Pannexin 1 (PANX1) is an ion and metabolite membrane channel and scaffold protein enriched in synaptic compartments of neurons in the central nervous system. In addition to a well‐established link between PANX1 and synaptic plasticity, we recently identified a role for PANX1 in the regulation of dendritic spine stability. Notably, PANX1 and its interacting proteins are linked to neurological conditions involving dendritic spine loss. Understanding the dual role of PANX1 in synaptic function and morphology may help to shed light on these links. We explore potential mechanisms, including PANX1's interactions with postsynaptic receptors and cytoskeleton regulating proteins. Finally, we contextualize PANX1's dual role within neurological diseases involving dendritic spine and synapse dysfunction. [ABSTRACT FROM AUTHOR]

Introduction: Neuropathic pain (NP) conditions arising from injuries to the nervous system due to trauma, disease, or neurotoxins are chronic, severe, debilitating, and exceedingly difficult to treat. However, the mechanisms of NP are not yet clear. Here we explored the role of Dock4, an atypical Rac1 GEF, in the development of NP. Methods: Mechanical allodynia was assessed as paw withdrawal threshold by a dynamic plantar aesthesiometer. Immunofluorescence staining was conducted to investigate the expression and localization of Dock4, Rac1 and GluN2B. Quantitative analysis of Dock4, Rac1 and GluN2B were determined by qRT-PCR and Western blot assay. Spontaneous excitatory and inhibitory postsynaptic currents in spinal cord slices were examined using whole cell patch clam. Dendritic spine remodeling and synaptogenesis were detected in cultured dorsal spinal neurons. Results and discussion: We found that SNL caused markedly mechanical allodynia accompanied by increase of Dock4, GTP-Rac1and GluN2B, which was prevented by knockdown of Dock4. Electrophysiological tests showed that SNL facilitated excitatory synaptic transmission, however, this was also inhibited by Dock RNAi-LV. Moreover, knockdown of Dock4 prevented dendritic growth and synaptogenesis. Conclusion: In summary, our data indicated that Dock4 facilitated excitatory synaptic transmission by promoting the expression of GluN2B at the synaptic site and synaptogenesis, leading to the occurrence of NP. [ABSTRACT FROM AUTHOR]

Structural plasticity of dendritic spines in the nucleus accumbens (NAc) is crucial for learning from aversive experiences. Activation of NMDA receptors (NMDARs) stimulates Ca2+-dependent signaling that leads to changes in the actin cytoskeleton, mediated by the Rho family of GTPases, resulting in postsynaptic remodeling essential for learning. We investigated how phosphorylation events downstream of NMDAR activation drive the changes in synaptic morphology that underlie aversive learning. Large-scale phosphoproteomic analyses of protein kinase targets in mouse striatal/accumbal slices revealed that NMDAR activation resulted in the phosphorylation of 194 proteins, including RhoA regulators such as ARHGEF2 and ARHGAP21. Phosphorylation of ARHGEF2 by the Ca2+-dependent protein kinase CaMKII enhanced its RhoGEF activity, thereby activating RhoA and its downstream effector Rho-associated kinase (ROCK/Rho-kinase). Further phosphoproteomic analysis identified 221 ROCK targets, including the postsynaptic scaffolding protein SHANK3, which is crucial for its interaction with NMDARs and other postsynaptic scaffolding proteins. ROCK-mediated phosphorylation of SHANK3 in the NAc was essential for spine growth and aversive learning. These findings demonstrate that NMDAR activation initiates a phosphorylation cascade crucial for learning and memory. Editor's summary: A component of the strengthened synaptic transmission that occurs in learning and memory is the growth of protrusions on neurons called dendritic spines, which requires activation of the NMDAR family of receptors in the nucleus accumbens. Funahashi et al. delineated the signaling pathway downstream of NMDARs that mediated aversive learning, which enables the identification, prediction, and avoidance of dangerous situations. The authors characterized the proteins phosphorylated in response to NMDAR activation and the kinases responsible. Dendritic spine growth and aversive learning were attenuated when the cytoskeleton-regulating kinase ROCK was pharmacologically inhibited or genetically ablated or when the ROCK-mediated phosphorylation of a specific substrate, the scaffolding protein SHANK3, was blocked in the nucleus accumbens. Thus, the phosphorylation of SHANK3 by ROCK is crucial for the changes in the neuronal actin cytoskeleton that support aversive learning. —Wei Wong [ABSTRACT FROM AUTHOR]

Introduction: Autism spectrum disorder (ASD) is a neurodevelopmental condition that affects various regions of the brain. Repetitive transcranial magnetic stimulation (rTMS) is a safe and non-invasive method utilized for stimulating different brain areas. Our objective is to alleviate ASD symptoms using high-frequency rTMS (HF-rTMS) in a rat model of ASD induced by valproic acid (VPA). Methods: In this investigation, we applied HF-rTMS for ASD treatment, focusing on the hippocampus. Behavioral assessments encompassed core ASD behaviors, as well as memory and recognition tests, alongside evaluations of anxiety and stress coping strategies. Additionally, we analyzed oxidative stress and a related inflammation marker, as well as other biochemical components. We assessed brain-derived neurotrophic factor (BDNF), Microtubule-associated protein-2 (MAP-2), and synaptophysin (SYN). Finally, we examined dendritic spine density in the CA1 area of the hippocampus. Results: The results demonstrated that HF-rTMS successfully mitigated ASD symptoms, reducing oxidative stress and improving various biochemical factors, along with an increase in dendritic spine density. Discussion: Collectively, our data suggests that HF-rTMS may effectively alleviate ASD symptoms. These findings could be valuable in clinical research and contribute to a better understanding of the mechanisms underlying ASD. [ABSTRACT FROM AUTHOR]

Kelch‐like family member 17 (KLHL17), an actin‐associated adaptor protein, is linked to neurological disorders, including infantile spasms and autism spectrum disorders. The key morphological feature of Klhl17‐deficient neurons is impaired dendritic spine enlargement, resulting in the amplitude of calcium events being increased. Our previous studies have indicated an involvement of F‐actin and the spine apparatus in KLHL17‐mediated dendritic spine enlargement. Here, we show that KLHL17 further employs different mechanisms to control the expression of two types of glutamate receptors, that is, α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptor (AMPAR) and kainate receptors (KARs), to regulate dendritic spine enlargement and calcium influx. We deployed proteomics to reveal that KLHL17 interacts with N‐ethylmaleimide‐sensitive fusion protein (NSF) in neurons, with this interaction of KLHL17 and NSF enhancing NSF protein levels. Consistent with the function of NSF in regulating the surface expression of AMPAR, Klhl17 deficiency limits the surface expression of AMPAR, but not its total protein levels. The NSF pathway also contributes to synaptic F‐actin distribution and the dendritic spine enlargement mediated by KLHL17. KLHL17 is known to act as an adaptor mediating degradation of the KAR subunit GluK2 by the CUL3 ubiquitin ligase complex, and Klhl17 deficiency impairs activity‐dependent degradation of GluK2. Herein, we further demonstrate that GluK2 is critical to the increased amplitude of calcium influx in Klhl17‐deficient neurons. Moreover, GluK2 is also involved in KLHL17‐regulated dendritic spine enlargement. Thus, our study reveals that KLHL17 controls AMPAR and KAR expression via at least two mechanisms, consequently regulating dendritic spine enlargement. The regulatory effects of KLHL17 on these two glutamate receptors likely contribute to neuronal features in patients suffering from certain neurological disorders. [ABSTRACT FROM AUTHOR]

Autism is a neurodevelopmental disorder, the prevalence of which has increased dramatically in the United States over the past two decades. It is characterized by stereotyped behaviors and impairments in social interaction and communication. In this paper, we present evidence that autism can be viewed as a PIN1 deficiency syndrome. Peptidyl‐prolyl cis/trans isomerase, NIMA‐Interacting 1 (PIN1) is a peptidyl‐prolyl cis/trans isomerase, and it has widespread influences in biological organisms. Broadly speaking, PIN1 deficiency is linked to many neurodegenerative diseases, whereas PIN1 over‐expression is linked to cancer. Death‐associated protein kinase 1 (DAPK1) strongly inhibits PIN1, and the hormone melatonin inhibits DAPK1. Melatonin deficiency is strongly linked to autism. It has recently been shown that glyphosate exposure to rats inhibits melatonin synthesis as a result of increased glutamate release from glial cells and increased expression of metabotropic glutamate receptors. Glyphosate's inhibition of melatonin leads to a reduction in PIN1 availability in neurons. In this paper, we show that PIN1 deficiency can explain many of the unique morphological features of autism, including increased dendritic spine density, missing or thin corpus callosum, and reduced bone density. We show how PIN1 deficiency disrupts the functioning of powerful high‐level signaling molecules, such as nuclear factor erythroid 2‐related factor 2 (NRF2) and p53. Dysregulation of both of these proteins has been linked to autism. Severe depletion of glutathione in the brain resulting from chronic exposure to oxidative stressors and extracellular glutamate leads to oxidation of the cysteine residue in PIN1, inactivating the protein and further contributing to PIN1 deficiency. Impaired autophagy leads to increased sensitivity of neurons to ferroptosis. It is imperative that further research be conducted to experimentally validate whether the mechanisms described here take place in response to chronic glyphosate exposure and whether this ultimately leads to autism. [ABSTRACT FROM AUTHOR]

Resveratrol, a naturally occurring polyphenol that activates sirtuin 1 (SIRT1), has been shown to reduce overall levels of matrix metalloprotease‐9 (MMP‐9) in cerebrospinal fluid (CSF) samples from patients with Alzheimer's dementia (AD). Depending on the site of release, however, MMP‐9 has the potential to improve or impair cognition. In particular, its release from microglia or pericytes proximal to the blood brain barrier can damage the basement membrane, while neuronal activity‐dependent release of this protease from glutamatergic neurons can instead promote dendritic spine expansion and long‐term potentiation of synaptic plasticity. In the present study, we test the hypothesis that resveratrol reduces overall MMP‐9 levels in CSF samples from patients with APOE4, an allele associated with increased glial inflammation. We also examine the possibility that resveratrol reduces inflammation‐associated MMP release from cultured glia but spares neuronal activity‐dependent release from cultured cortical neurons. We observe that resveratrol decreases overall levels of MMP‐2 and MMP‐9 in CSF samples from AD patients. Resveratrol also reduces CSF levels of tissue inhibitor of metalloproteinases‐1 (TIMP‐1), glial‐derived protein that restricts long‐term potentiation of synaptic transmission, in individuals homozygous for APOE4. Consistent with these results, we observe that resveratrol reduces basal and lipopolysaccharide (LPS)‐stimulated MMP and TIMP‐1 release from cultured microglia and astrocytes. In contrast, however, resveratrol does not inhibit release of MMP‐9 from cortical neurons. Overall, these results are consistent with the possibility that while resveratrol reduces potentially maladaptive MMP and TIMP‐1 release from activated glia, neuroplasticity‐promoting MMP release from neurons is spared. In contrast, resveratrol reduces release of neurocan and brevican, extracellular matrix components that restrict neuroplasticity, from both neurons and glia. These data underscore the diversity of resveratrol's actions with respect to affected cell types and molecular targets and also suggest that further studies may be warranted to determine if its effects on glial MMP release could make it a useful adjunct for AD‐ and/or anti‐amyloid therapy‐related damage to the blood brain barrier. [ABSTRACT FROM AUTHOR]

Introduction: Neuroinflammation and microglial activation‐related dendritic injury contribute to the pathogenesis of Autism Spectrum Disorder (ASD). Previous studies show that Progranulin (PGRN) is a growth factor associated with inflammation and synaptic development, but the role of PGRN in autism and the mechanisms underlying changes in PGRN expression remain unclear. Aims: To investigate the impact of PGRN in autism, we stereotactically injected recombinant PGRN into the hippocampus of ASD model rats. Additionally, we explored the possibility that sortilin may be the factor behind the alterations in PGRN by utilizing SORT1 knockdown. Ultimately, we aimed to identify potential targets for the treatment of autism. Results: PGRN could alleviate inflammatory responses, protect neuronal dendritic spines, and ameliorate autism‐like behaviors. Meanwhile, elevated expression of sortilin and decreased levels of PGRN were observed in both ASD patients and rats. Enhanced sortilin levels facilitated PGRN internalization into lysosomes. Notably, suppressing SORT1 expression amplified PGRN levels, lessened microglial activation, and mitigated inflammation, thereby alleviating autism‐like behaviors. Conclusion: Collectively, our findings highlight elevated sortilin levels in ASD rat brains, exacerbating dendrite impairment by affecting PGRN expression. PGRN supplementation and SORT1 knockdown hold potential as therapeutic strategies for ASD. [ABSTRACT FROM AUTHOR]

Sensorimotor deficits following stroke remain a major cause of disability, but little is known about the specific pathological mechanisms. Exploring the pathological mechanisms and identifying potential therapeutic targets to promote functional rehabilitation after stroke are essential. CXCL10, also known as interferon-γ-inducible protein 10 (IP-10), plays an important role in multiple brain disorders by mediating synaptic plasticity, yet its role in stroke is still unclear. In this study, mice were subjected to photothrombotic (PT) stroke, and sensorimotor deficits were determined by the ladder walking tests, tape removal tests, and rotarod tests. The density of dendritic spines and synaptic plasticity was determined in Thy1-EGFP mice and evaluated by electrophysiology. We found that photothrombotic stroke induced sensorimotor deficits and upregulated the expression of CXCL10, whereas suppressing the expression of CXCL10 by adeno-associated virus (AAV) ameliorated sensorimotor deficits and increased the levels of synapse-related proteins, the density of dendritic spines, and synaptic strength. Furthermore, the cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulus of interferon genes (STING) pathway was activated by stroke and induced CXCL10 release, and cGAS or STING antagonists downregulated the levels of CXCL10 and improved synaptic plasticity after stroke. Collectively, our results indicate that cGAS-STING pathway activation promoted CXCL10 release and impaired synaptic plasticity during stroke recovery. NEW & NOTEWORTHY: Chemokine-mediated inflammatory response plays a critical role in stroke. CXCL10 plays an important role in multiple brain disorders by mediating synaptic plasticity, yet its role in stroke recovery is still unclear. Herein, we identified a new mechanism that cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulus of interferon genes (STING) pathway activation promoted CXCL10 release and impaired synaptic plasticity during stroke recovery. Our findings highlight the potential therapeutic strategy of targeting the cGAS-STING pathway to treat stroke. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate whether the dorsal claustrum receives afferent input from the intralaminar thalamic nuclei – centromedian nucleus, central lateral nucleus and paracentral nucleus. The intralaminar thalamic nuclei of eight cats were electrolytically lesioned. We obtained samples from the dorsal claustrum for electron microscopic analysis from the second to the seventh post-procedural day. Two types of degenerated synaptic boutons were observed: electron-dense which formed the majority of boutons, and electron-lucent comprising the remaining samples. Between the second and seventh post-procedural day, we observed a steady increase in the number of electron-dense boutons which were diffusely distributed throughout the dorsal claustrum. Electron-dense degenerated boutons formed asymmetrical contacts with dendritic spines as well as with small and medium-sized dendrites. In contrast, electron-lucent degenerated boutons were observed in earlier post-procedural periods and formed symmetrical axodendritic contacts. [ABSTRACT FROM AUTHOR]

Neuroinflammation is being increasingly recognized as a vital factor in the development of various neurological and neuropsychiatric diseases. Lipopolysaccharides (LPS), an outer membrane component of gram-negative bacteria, can trigger innate immune responses, resulting in neuroinflammation and subsequent cognitive deficits. The expression of glutamate receptors (GluRs) on glial cells can induce glial activation. Therefore, we hypothesized that repeated LPS exposure can increase GluR levels, promoting microglial activation and ultimately affecting synaptic plasticity and cognitive function. In this study, C57/BL6 mice were repeatedly exposed to LPS to construct a neuroinflammation animal model. The levels of GluRs, inflammatory cytokines, ionized calcium-binding adaptor molecule 1, postsynaptic density protein 95, synaptophysin 38, NMDA receptor 2 A, and NMDA receptor 2B (GluN2B) were measured in the hippocampi. Furthermore, dendritic spine density in the CA1 hippocampal region was determined. Repeated LPS exposure induced cognitive impairments and microglial activation and increased GluR1 and GluR2 levels. This was accompanied by a significant decrease in GluN2B expression and dendritic spine density in the hippocampi. However, CFM-2, an α-amino-3- hydroxy-5-methyl-4-isoxazolepropionate receptor antagonist, reversed these anomalies. Furthermore, minocycline, a microglial inhibitor, reversed these anomalies and downregulated GluR2 but not GluR1 expression. In summary, we demonstrated that GluR2 plays an essential role in microglia-induced neuroinflammation, resulting in synaptic plasticity and cognitive impairment induced by repeated exposure to LPS. [ABSTRACT FROM AUTHOR]

• Multiparameter DiOlistics facilitates contextual assessment of neuronal networks. • Tissue fixation enables higher throughput multiparameter staining of tissues. • Fixed tissue DiOlistics provides reliable imaging of dendrites and dendritic spines. DiOlistic labelling is a robust, unbiased ballistic method that utilises lipophilic dyes to morphologically label neurons. While its efficacy on freshly dissected tissue specimens is well-documented, applying DiOlistic labelling to stored, fixed brain tissue and its use in polychromatic multi-marker studies poses significant technical challenges. Here, we present an improved, step-by-step protocol for DiOlistic labelling of dendrites and dendritic spines in fixed mouse tissue. Our protocol encompasses the five key stages: Tissue Preparation, Dye Bullet Preparation, DiOlistic Labelling, Confocal Imaging, and Image Analysis. This method ensures reliable and consistent labelling of dendritic spines in fixed mouse tissue, combined with increased throughput of samples and multi-parameter staining and visualisation of tissue, thereby offering a valuable approach for neuroscientific research. [ABSTRACT FROM AUTHOR]

The molecular mechanisms and evolutionary changes accompanying synapse development are still poorly understood1,2. Here we generate a cross-species proteomic map of synapse development in the human, macaque and mouse neocortex. By tracking the changes of more than 1,000 postsynaptic density (PSD) proteins from midgestation to young adulthood, we find that PSD maturation in humans separates into three major phases that are dominated by distinct pathways. Cross-species comparisons reveal that human PSDs mature about two to three times slower than those of other species and contain higher levels of Rho guanine nucleotide exchange factors (RhoGEFs) in the perinatal period. Enhancement of RhoGEF signalling in human neurons delays morphological maturation of dendritic spines and functional maturation of synapses, potentially contributing to the neotenic traits of human brain development. In addition, PSD proteins can be divided into four modules that exert stage- and cell-type-specific functions, possibly explaining their differential associations with cognitive functions and diseases. Our proteomic map of synapse development provides a blueprint for studying the molecular basis and evolutionary changes of synapse maturation.

Suicide is a manner of death resulting from complex environmental and genetic risks that affect millions of people globally. Both structural and functional studies identified the hippocampus as one of the vulnerable brain regions contributing to suicide risk. We have identified the hippocampal tissue transcriptomes, gene ontology, cell type proportions, and dendritic spine morphology in controls (n = 28) and suicide decedents (n = 22). In addition, the transcriptomic signature in iPSC-derived neuronal precursor cells (NPCs) and neurons were also investigated in controls (n = 2) and suicide decedents (n = 2). The hippocampal tissue transcriptomic data revealed that NPAS4 gene expression was downregulated while ALDH1A2 , NAAA , and MLXIPL gene expressions were upregulated in hippocampal tissue of suicide decedents. The gene ontology identified 29 significant pathways including NPAS4 -associated gene ontology terms "excitatory post-synaptic potential", "regulation of postsynaptic membrane potential" and "long-term memory" indicating alteration of glutamatergic synapses in the hippocampus of suicide decedents. The cell type deconvolution identified decreased excitatory neuron proportion and an increased inhibitory neuron proportion providing evidence of excitation/inhibition imbalance in the hippocampus of suicide decedents. In addition, suicide decedents had increased dendric spine density in the hippocampus, due to an increase of thin (relatively unstable) dendritic spines, compared to controls. The transcriptomes of iPSC-derived hippocampal-like NPCs and neurons revealed 31 and 33 differentially expressed genes in NPC and neurons, respectively, of suicide decedents. Our findings will provide new insights into the hippocampal neuropathology of suicide. • NPAS4 was downregulated while ALDH1A2, NAAA , and MLXIPL gene expressions were upregulated in hippocampus of suicide deaths. • There is a decreased excitatory neuron and increased inhibitory neuron proportions in the hippocampus of suicide deaths. • Suicide deaths had increased dendric thin (relatively unstable) spine density in the hippocampus, compared to controls. • The iPSC-derived hippocampal-like NPCs and neurons revealed 31 and 33 differentially expressed genes each, in suicide deaths. [ABSTRACT FROM AUTHOR]

Abstract Loss-of-function mutations in the progranulin (GRN) gene are an autosomal dominant cause of Frontotemporal Dementia (FTD). These mutations typically result in haploinsufficiency of the progranulin protein. Grn +/– mice provide a model for progranulin haploinsufficiency and develop FTD-like behavioral abnormalities by 9–10 months of age. In previous work, we demonstrated that Grn +/– mice develop a low dominance phenotype in the tube test that is associated with reduced dendritic arborization of layer II/III pyramidal neurons in the prelimbic region of the medial prefrontal cortex (mPFC), a region key for social dominance behavior in the tube test assay. In this study, we investigated whether progranulin haploinsufficiency induced changes in dendritic spine density and morphology. Individual layer II/III pyramidal neurons in the prelimbic mPFC of 9–10 month old wild-type or Grn +/– mice were targeted for iontophoretic microinjection of fluorescent dye, followed by high-resolution confocal microscopy and 3D reconstruction for morphometry analysis. Dendritic spine density in Grn +/– mice was comparable to wild-type littermates, but the apical dendrites in Grn +/– mice had a shift in the proportion of spine types, with fewer stubby spines and more thin spines. Additionally, apical dendrites of Grn +/– mice had longer spines and smaller thin spine head diameter in comparison to wild-type littermates. These changes in spine morphology may contribute to altered circuit-level activity and social dominance deficits in Grn +/– mice.

During animal development, the spatiotemporal properties of molecular events largely determine the biological outcomes. Conventional gene analysis methods lack the spatiotemporal resolution for precise dissection of developmental mechanisms. Although optogenetic tools exist for manipulating designer proteins in cultured cells, few have been successfully applied to endogenous proteins in live animals. Here, we report OptoTrap, a light-inducible clustering system for manipulating endogenous proteins of diverse sizes, subcellular locations, and functions in Drosophila. This system turns on fast, is reversible in minutes or hours, and contains variants optimized for neurons and epithelial cells. By using OptoTrap to disrupt microtubules and inhibit kinesin-1 in neurons, we show that microtubules support the growth of highly dynamic dendrites and that kinesin-1 is required for patterning of low-and high-order dendritic branches in differential spatiotemporal domains. OptoTrap allows for precise manipulation of endogenous proteins in a spatiotemporal manner and thus holds promise for studying developmental mechanisms in a wide range of cell types and developmental stages. [ABSTRACT FROM AUTHOR]

Learning and memory require coordinated structural and functional plasticity at neuronal glutamatergic synapses located on dendritic spines. Here, we investigated how the endoplasmic reticulum (ER) controls postsynaptic Ca2+ signaling and long-term potentiation of dendritic spine size, i.e., sLTP that accompanies functional strengthening of glutamatergic synaptic transmission. In most ER-containing (ER+) spines, high-frequency optical glutamate uncaging (HFGU) induced long-lasting sLTP that was accompanied by a persistent increase in spine ER content downstream of a signaling cascade engaged by N-methyl-D-aspartate receptors (NMDARs), L-type Ca2+ channels (LTCCs), and Orai1 channels, the latter being activated by stromal interaction molecule 1 (STIM1) in response to ER Ca2+ release. In contrast, HFGU stimulation of ER-lacking (ER-) spines expressed only transient sLTP and exhibited weaker Ca2+ signals noticeably lacking Orai1 and ER contributions. Consistent with spine ER regulating structural metaplasticity, delivery of a second stimulus to ER-spines induced ER recruitment along with persistent sLTP, whereas ER+ spines showed no additional increases in size or ER content in response to sequential stimulation. Surprisingly, the physical interaction between STIM1 and Orai1 induced by ER Ca2+ release, but not the resulting Ca2+ entry through Orai1 channels, proved necessary for the persistent increases in both spine size and ER content required for expression of long-lasting late sLTP. [ABSTRACT FROM AUTHOR]

Activity-regulated cytoskeleton-associated protein (Arc/Arg3.1) is an immediate early gene that plays a vital role in learning and memory. Arc protein has structural and functional properties similar to viral Group-specific antigen (Gag) protein and mediates the intercellular RNA transfer through virus-like capsids. However, the regulators and secretion pathway through which Arc capsids maneuver cargos are unclear. Here, we identified that phosphatidylinositol-3-phosphate (PI3P) mediates Arc capsid assembly and secretion through the endosomal-multivesicular body (MVB) pathway. Indeed, reconstituted Arc protein preferably binds to PI3P. In HEK293T cells, Arc forms puncta that colocalize with FYVE, an endosomal PI3P marker, as well as Rab5 and CD63, early endosomal and MVB markers, respectively. Superresolution imaging resolves Arc accumulates within the intraluminal vesicles of MVB. CRISPR double knockout of RalA and RalB, crucial GTPases for MVB biogenesis and exocytosis, severely reduces the Arc-mediated RNA transfer efficiency. RalA/B double knockdown in cultured rat cortical neurons increases the percentage of mature dendritic spines. Intake of extracellular vesicles purified from Arc-expressing wild-type, but not RalA/B double knockdown, cells in mouse cortical neurons reduces their surface GlutA1 levels. These results suggest that unlike the HIV Gag, whose membrane targeting requires interaction with plasma-membrane-specific phosphatidyl inositol (4,5) bisphosphate (PI(4,5)P2), the assembly of Arc capsids is mediated by PI3P at endocytic membranes. Understanding Arc's secretion pathway helps gain insights into its role in intercellular cargo transfer and highlights the commonality and distinction of trafficking mechanisms between structurally resembled capsid proteins. [ABSTRACT FROM AUTHOR]

Background Methods Results Conclusion The potential neuroprotective effects of dexmedetomidine against ketamine‐induced neurotoxicity remain inconclusive. This study aims to investigate the influence of dexmedetomidine on ketamine‐induced neuronal apoptosis and neurodevelopmental toxicity.In vitro experiments employed concentrations of 0.1 uM for dexmedetomidine and 50 uM for ketamine individually as well as their combination. Changes in apoptotic proteins and dendritic development in neurons were assessed after a 6‐h exposure to the drugs with evaluations conducted 24 hs' post‐treatment. In vivo experiments entailed intraperitoneal administration starting from postnatal Day 7 (P7) continuously for 3 days (P7–P9) using dosages of 100 mg/kg for ketamine and 1 mg/kg for dexmedetomidine alone or combined. Learning, memory and motor coordination abilities were evaluated via rotary rod tests and shuttle box experiments at P30 and P60, respectively.Dexmedetomidine effectively mitigated ketamine‐induced apoptosis in hippocampal neurons but did not alleviate associated dendritic developmental abnormalities. Although causing reduced motor coordination in mice, no improvement was observed with regard to this effect or reaction speed when treated with dexmedetomidine alongside ketamine.This study demonstrates that while dexmedetomidine can mitigate ketamine‐induced neuronal apoptosis, it has limited impact on its associated neurodevelopmental toxicities. [ABSTRACT FROM AUTHOR]

Astrotactin 2 (ASTN2) is a transmembrane neuronal protein highly expressed in the cerebellum that functions in receptor trafficking and modulates cerebellar Purkinje cell (PC) synaptic activity. Individuals with ASTN2 mutations exhibit neurodevelopmental disorders, including autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), learning difficulties, and language delay. To provide a genetic model for the role of the cerebellum in ASD-related behaviors and study the role of ASTN2 in cerebellar circuit function, we generated global and PC-specific conditional Astn2 knockout (KO and cKO, respectively) mouse lines. Astn2 KO mice exhibit strong ASD-related behavioral phenotypes, including a marked decrease in separation-induced pup ultrasonic vocalization calls, hyperactivity, repetitive behaviors, altered behavior in the three-chamber test, and impaired cerebellar-dependent eyeblink conditioning. Hyperactivity and repetitive behaviors are also prominent in Astn2 cKO animals, but they do not show altered behavior in the three-chamber test. By Golgi staining, Astn2 KO PCs have region-specific changes in dendritic spine density and filopodia numbers. Proteomic analysis of Astn2 KO cerebellum reveals a marked upregulation of ASTN2 family member, ASTN1, a neuron-glial adhesion protein. Immunohistochemistry and electron microscopy demonstrate a significant increase in Bergmann glia volume in the molecular layer of Astn2 KO animals. Electrophysiological experiments indicate a reduced frequency of spontaneous excitatory postsynaptic currents (EPSCs), as well as increased amplitudes of both spontaneous EPSCs and inhibitory postsynaptic currents in the Astn2 KO animals, suggesting that pre-and postsynaptic components of synaptic transmission are altered. Thus, ASTN2 regulates ASD-like behaviors and cerebellar circuit properties. [ABSTRACT FROM AUTHOR]

Epigenetic mechanisms such as DNA methylation and hydroxymethylation play a significant role in depression. This research has shown that Ten‐eleven translocation 2 (Tet2) deficiency prompts depression‐like behaviors, but Tet2's transcriptional regulation remains unclear. In the study, bioinformatics is used to identify nuclear receptor subfamily 2 group E member 3 (Nr2e3) as a potential Tet2 regulator. Nr2e3 is found to enhance Tet2's transcriptional activity by binding to its promoter region. Nr2e3 knockdown in mouse hippocampus leads to reduced Tet2 expression, depression‐like behaviors, decreased hydroxymethylation of synaptic genes, and downregulation of synaptic proteins like postsynaptic density 95 KDa (PSD95) and N‐methy‐d‐aspartate receptor 1 (NMDAR1). Fewer dendritic spines are also observed. Nr2e3 thus appears to play an antidepressant role under stress. In search of potential treatments, small molecule compounds to increase Nr2e3 expression are screened. Azacyclonal (AZA) is found to enhance the Nr2e3/Tet2 pathway and exhibited antidepressant effects in stressed mice, increasing PSD95 and NMDAR1 expression and dendritic spine density. This study illuminates Tet2's upstream regulatory mechanism, providing a new target for identifying early depression biomarkers and developing treatments. [ABSTRACT FROM AUTHOR]

The morphology of dendritic spines, the postsynaptic compartment of most excitatory synapses, decisively modulates the function of neuronal circuits as also evident from human brain disorders associated with altered spine density or morphology. Actin filaments (F-actin) form the backbone of spines, and a number of actin-binding proteins (ABP) have been implicated in shaping the cytoskeleton in mature spines. Instead, only little is known about the mechanisms that control the reorganization from unbranched F-actin of immature spines to the complex, highly branched cytoskeleton of mature spines. Here, we demonstrate impaired spine maturation in hippocampal neurons upon genetic inactivation of cyclase-associated protein 1 (CAP1) and CAP2, but not of CAP1 or CAP2 alone. We found a similar spine maturation defect upon overactivation of inverted formin 2 (INF2), a nucleator of unbranched F-actin with hitherto unknown synaptic function. While INF2 overactivation failed in altering spine density or morphology in CAP-deficient neurons, INF2 inactivation largely rescued their spine defects. From our data we conclude that CAPs inhibit INF2 to induce spine maturation. Since we previously showed that CAPs promote cofilin1-mediated cytoskeletal remodeling in mature spines, we identified them as a molecular switch that control transition from filopodia-like to mature spines. [ABSTRACT FROM AUTHOR]

The widespread use of wireless communication devices has necessitated unavoidable exposure to radiofrequency electromagnetic fields (RF-EMF). In particular, increasing RF-EMF exposure among children is primarily driven by mobile phone use. Therefore, this study investigated the effects of 1850 MHz RF-EMF exposure at a specific absorption rate of 4.0 W/kg on cortical neurons in mice at postnatal day 28. The results indicated a significant reduction in the number of mushroom-shaped dendritic spines in the prefrontal cortex after daily exposure for 4 weeks. Additionally, prolonged RF-EMF exposure over 9 days led to a gradual decrease in postsynaptic density 95 puncta and inhibited neurite outgrowth in developing cortical neurons. Moreover, the expression levels of genes associated with synapse formation, such as synaptic cell adhesion molecules and cyclin-dependent kinase 5, were reduced in the cerebral cortexes of RF-EMF-exposed mice. Behavioral assessments using the Morris water maze revealed altered spatial learning and memory after the 4-week exposure period. These findings underscore the potential of RF-EMF exposure during childhood to disrupt synaptic function in the cerebral cortex, thereby affecting the developmental stages of the nervous system and potentially influencing later cognitive function. [ABSTRACT FROM AUTHOR]

Episodic memory in older adults is varied and perceived to rely on numbers of synapses or dendritic spines. We analyzed 2157 neurons among 128 older individuals from the Religious Orders Study and Rush Memory and Aging Project. Analysis of 55,521 individual dendritic spines by least absolute shrinkage and selection operator regression and nested model cross-validation revealed that the dendritic spine head diameter in the temporal cortex, but not the premotor cortex, improved the prediction of episodic memory performance in models containing β amyloid plaque scores, neurofibrillary tangle pathology, and sex. These findings support the emerging hypothesis that, in the temporal cortex, synapse strength is more critical than quantity for memory in old age. [ABSTRACT FROM AUTHOR]

Background: We recently reported that the dopamine (DA) analogue CA140 modulates neuroinflammatory responses in lipopolysaccharide-injected wild-type (WT) mice and in 3-month-old 5xFAD mice, a model of Alzheimer's disease (AD). However, the effects of CA140 on Aβ/tau pathology and synaptic/cognitive function and its molecular mechanisms of action are unknown. Methods: To investigate the effects of CA140 on cognitive and synaptic function and AD pathology, 3-month-old WT mice or 8-month-old (aged) 5xFAD mice were injected with vehicle (10% DMSO) or CA140 (30 mg/kg, i.p.) daily for 10, 14, or 17 days. Behavioral tests, ELISA, electrophysiology, RNA sequencing, real-time PCR, Golgi staining, immunofluorescence staining, and western blotting were conducted. Results: In aged 5xFAD mice, a model of AD pathology, CA140 treatment significantly reduced Aβ/tau fibrillation, Aβ plaque number, tau hyperphosphorylation, and neuroinflammation by inhibiting NLRP3 activation. In addition, CA140 treatment downregulated the expression of cxcl10, a marker of AD-associated reactive astrocytes (RAs), and c1qa, a marker of the interaction of RAs with disease-associated microglia (DAMs) in 5xFAD mice. CA140 treatment also suppressed the mRNA levels of s100β and cxcl10, markers of AD-associated RAs, in primary astrocytes from 5xFAD mice. In primary microglial cells from 5xFAD mice, CA140 treatment increased the mRNA levels of markers of homeostatic microglia (cx3cr1 and p2ry12) and decreased the mRNA levels of a marker of proliferative region-associated microglia (gpnmb) and a marker of lipid-droplet-accumulating microglia (cln3). Importantly, CA140 treatment rescued scopolamine (SCO)-mediated deficits in long-term memory, dendritic spine number, and LTP impairment. In aged 5xFAD mice, these effects of CA140 treatment on cognitive/synaptic function and AD pathology were regulated by dopamine D1 receptor (DRD1)/Elk1 signaling. In primary hippocampal neurons and WT mice, CA140 treatment promoted long-term memory and dendritic spine formation via effects on DRD1/CaMKIIα and/or ERK signaling. Conclusions: Our results indicate that CA140 improves neuronal/synaptic/cognitive function and ameliorates Aβ/tau pathology and neuroinflammation by modulating DRD1 signaling in primary hippocampal neurons, primary astrocytes/microglia, WT mice, and aged 5xFAD mice. [ABSTRACT FROM AUTHOR]

This article comprehensively reviews how cerebral hypoxia impacts the physiological state of neurons and dendritic spines through a series of molecular changes, and explores the causal relationship between these changes and neuronal functional impairment. As a severe pathological condition, cerebral hypoxia can significantly alter the morphology and function of neurons and dendritic spines. Specifically, dendritic spines, being the critical structures for neurons to receive information, undergo changes such as a reduction in number and morphological abnormalities under hypoxic conditions. These alterations further affect synaptic function, leading to neurotransmission disorders. This article delves into the roles of molecular pathways like MAPK, AMPA receptors, NMDA receptors, and BDNF in the hypoxia-induced changes in neurons and dendritic spines, and outlines current treatment strategies. Neurons are particularly sensitive to cerebral hypoxia, with their apical dendrites being vulnerable to damage, thereby affecting cognitive function. Additionally, astrocytes and microglia play an indispensable role in protecting neuronal and synaptic structures, regulating their normal functions, and contributing to the repair process following injury. These studies not only contribute to understanding the pathogenesis of related neurological diseases but also provide important insights for developing novel therapeutic strategies. Future research should further focus on the dynamic changes in neurons and dendritic spines under hypoxic conditions and their intrinsic connections with cognitive function. [ABSTRACT FROM AUTHOR]

One key function of the brain is to control our body's movements, allowing us to interact with the world around us. Yet, many motor behaviors are not innate but require learning through repeated practice. Among the brain's motor regions, the cortico-basal ganglia circuit is particularly crucial for acquiring and executing motor skills, and neuronal activity in these regions is directly linked to movement parameters. Cell-type-specific adaptations of activity patterns and synaptic connectivity support the learning of new motor skills. Functionally, neuronal activity sequences become structured and associated with learned movements. On the synaptic level, specific connections become potentiated during learning through mechanisms such as long-term synaptic plasticity and dendritic spine dynamics, which are thought to mediate functional circuit plasticity. These synaptic and circuit adaptations within the cortico-basal ganglia circuitry are thus critical for motor skill acquisition, and disruptions in this plasticity can contribute to movement disorders. Learning new motor skills involves significant changes in the connectivity and activity of brain motor circuits. In this review, Roth and Ding discuss recent findings on motor-learning-induced neural plasticity within the cortico-basal ganglia circuitry, highlighting the role of circuit adaptations and underlying synaptic plasticity mechanisms. [ABSTRACT FROM AUTHOR]