Activation Of Neurons Research Articles

Dorsal bed nucleus of the stria terminalis GABA neurons are necessary for chronic unpredictable stress-induced depressive behaviors in adolescent male mice.

Previous studies have shown that neurons in the Bed Nucleus of the Stria Terminalis (BNST) respond to stress and play a key role in mental health. However, the cellular bases of BNST in adolescent depression remain elusive. Male C57BL/6 mice were randomly assigned to the control (Ctrl) or chronic unpredictable stress (CUS) groups. The CUS mice, aged 28 days, were subjected to diverse stressors at various times of the day for 12 days. Depression-like behaviors were assessed through the sucrose preference test (SPT) and tail suspension test (TST). Immunostaining was used to investigate the neural activity and subtypes in the brain. A chemogenetic tool was conducted to examine the role of specific neural activity in CUS-induced depression-like behaviors. CUS led to a significant decrease in preference for sucrose solution in the SPT and increased immobility time in the TST. C-Fos immunostaining showed hyperactivity of the GABAergic neurons within the dorsal BNST (dBNSTGABA). Chemogenetic activation of dBNSTGABA neurons increased depression-like behaviors. Conversely, chemogenetic inhibition of dBNSTGABA neurons led to a decrease in CUS-induced depression. These results suggest that adolescent CUS induces hyperactivity of dBNSTGABA neurons, subsequently giving rise to depression-like behaviors and that reducing dBNSTGABA neuronal activity might constitute a novel and efficacious therapeutic approach for adolescent depression.

Bilateral chemogenetic activation of intratelencephalic neurons in motor cortex reduces spontaneous locomotor activity in mice

Intra-telencephalic neurons are a crucial class of cortical principal neurons that heavily innervate the striatum and cortical areas bilaterally. Their extensive cortico-cortical and cortico-striatal connectivity enables sensorimotor integration within the telencephalon, but their role in motor control remains poorly understood. Here, we used a chemogenetic approach to explore the role of intra-telencephalic neurons in spontaneous locomotor activity. Bilateral chemogenetic activation of intra-telencephalic Tlx3+ neurons in the mouse motor cortex reduced spontaneous locomotor activity in the open field, increasing states of freezing and immobility. This anti-motor effect was achieved in separate experiments with either administration of two chemogenetic actuators, clozapine N-oxide and deschloroclozapine. A systemic administration of the dopamine D1 receptor agonist SKF82958 reversed the chemogenetic effect on locomotor activity. Selective chemogenetic stimulation of intra-telencephalic neurons was confirmed through post-mortem c-Fos quantification in cortical layer 5 Tlx3+ neurons. The results establish a causal link between the activity level of intra-telencephalic neurons in the motor cortex, spontaneous locomotor activity in the open field, and the dopamine system. The findings are compatible with the hypothesis that intra-telencephalic neurons regulate spontaneous motor behavior via its bilateral cortico-striatal projections.

Effect of galanin-like peptide on hypothalamic kisspeptin expression in female Zucker fatty rats.

Kisspeptin and galanin-like peptide (GALP) neurons in the hypothalamic arcuate nucleus (ARC) are involved in gonadotropin-releasing hormone (GnRH) neuron-mediated pulsatile luteinizing hormone (LH) secretion. Zucker fatty (ZF) rats display a leptin receptor gene abnormality and suppressed pulsatile LH secretion. ZF rats reportedly exhibit low hypothalamic GALP and kisspeptin expression, and GALP administration induces LH release in ZF rats. Therefore, we performed a histochemical analysis to determine whether GALP-induced LH release is mediated by kisspeptin neurons in ZF rats. All ZF rats were ovariectomized and subcutaneously implanted with an estradiol tube before the central injection of GALP or vehicle. GALP administration increased the plasma LH concentration. However, no significant difference was observed in the number of Kiss1 cells and the proportion of Fos-positive Kiss1 cells. The number of c-Fos-positive GnRH neurons significantly increased after GALP administration. Our results suggest that hypothalamic GALP neurons promote LH release by activating GnRH neurons without the activation of kisspeptin neurons in the ARC.

Glutamate-mediated antidepressant effects of Jieyu I Formula via modulation of PFCCaMKII-LHbCaMKII/GABA circuitry in lipopolysaccharide-induced depression model.

Jieyu I Formula (JY-I) is an improved version of the classic formula "Sini San" documented in the books Shanghan Lun, which is known for regulating the liver and treating depression. However, the disturbance of neuronal signal transmission in the neural circuit of the brain is closely related to the occurrence of depression, yet its neural mechanism is still unclear. This study aimed to observe the antidepressant effect of JY-I on depressed mice induced by lipopolysaccharide and its underlying central nervous system mechanisms, focusing on the prefrontal cortex (PFC) to lateral habenular nucleus (LHb) neural circuit in the depressed mice model. JY-I comprised herbs include Bupleurum chinense, Fructus Aurantii, Paeonia lactiflora, Lotus Seed Heart, Schisandra chinensis, and Hypericum perforatum, which are prepared in a ratio of 2:2:2:2:1:1. The mouse model of depression was induced by lipopolysaccharide. The antidepressant efficacy of JY-I was observed by behavioral tests. Observation of the PFC/LHb neuron activity in mice using in-vivo electrophysiological combined with optogenetic technology. Subsequently, the activity of the LHb neuron was observed using immunofluorescence staining analysis and western blot. Inject Rabies virus into the LHb brain region and observe the projection of the PFC from upstream brain regions received by the LHb. Using chemogenetic techniques to activate/inhibit the PFC-LHb neural circuit and investigate the effect of JY-I on depression-like behaviors. Depression-like behaviors in mice can be induced by intraperitoneal administration of lipopolysaccharide, the behavior changes were reversed with the administration of the JY-I. The combination of optogenetics and electrophysiological recording result indicates that JY-I activates glutamate (Glu) neurons in the PFC, thus maintaining an optimal excitatory/inhibitory (E/I) balance and ameliorating depression-like behaviors. Notably, the PFC, a crucial brain area for emotion regulation, exerts its antidepressant effect on downstream LHb region through the activation of Glu neurons. JY-I can significantly improve lipopolysaccharide-induced depression-like behaviors. JY-I exerts antidepressant effects by activating the PFC Glu neurons projecting to the LHb, revealing a promising therapeutic target for depression.

Neuroprotective potential of isofraxidin: Alleviating parkinsonian symptoms, inflammation and microglial activation.

Parkinson's disease (PD) is one of the most common neurodegenerative disorders. Previous research has confirmed that isofraxidin can reduce macrophage expression and inhibit peripheral inflammation. However, its effects on the central nervous system remain underexplored. This study aims to determine whether isofraxidin offers protective effects against PD. To assess the effects of isofraxidin, motor performance changes in LPS-induced PD mice were evaluated using rotarod, pole-climbing, and beam-walking tests. Striatal damage was examined through [18F]fluorodeoxyglucose ([18F]FDG) positron emission tomography (PET) imaging, and dopaminergic neurotoxicity was assessed using tyrosine hydroxylase (TH) staining. Microglial accumulation and activation were monitored with Iba-1 staining, while LPS-induced inflammation was examined via TNF-α and IL-1β staining. Isofraxidin pre-treatment significantly improved LPS-induced motor dysfunction, as evidenced by better performance in the rotarod, pole-climbing, and beam-walking tests. [18F]FDG PET imaging showed that isofraxidin restored glucose uptake in the striatum, countering LPS-induced damage. Furthermore, Iba-1 staining revealed that isofraxidin markedly inhibited LPS-induced microglial activation and accumulation. TNF-α and IL-1β staining indicated a reduction in inflammation with isofraxidin treatment. Additionally, TH staining supported the neuroprotective role of isofraxidin on dopaminergic neurons. Isofraxidin exhibits notable neuroprotective properties by mitigating LPS-induced parkinsonian behaviors, microglial activation, inflammation, and dopaminergic neuron damage. These results highlight isofraxidin's potential as a therapeutic intervention for PD.

The Aqueous Extract of Armadillidium vulgare Latreille Alleviates Neuropathic Pain via Inhibiting Neuron-Astrocyte Crosstalk Mediated by the IL-12-IFN-γ-IFNGR-CXCL10 Pathway

Ethnopharmacological relevanceArmadillidium vulgare Latreille (AV), the dried body of pillbug, was originally described in Shennong’s Classic of Materia Medica. As a common analgesic in animal-based traditional Chinese medicine, it is mainly used to relieve pain, promoting diuresis, relieving fatigue and so on. Our work demonstrated that AV could alleviate various types of acute and chronic pain including neuropathic pain (NP). And transcriptome sequencing analysis revealed that AV could suppress CXCL10 to alleviate NP, however, the upstream mechanisms governing CXCL10 synthesis remain vague.Aim of the study: The research’s goal was to identify the mechanism via which AV regulates CXCL10 to ameliorate NP. Materials and methodsChronic constriction injury (CCI) to the sciatic nerve was used to induce the NP model 14 days following surgery. To identify cell signaling pathways, various approaches were used, including transcriptome sequencing, western blotting, immunofluorescence, as well as ELISA. The in vitro assay involved the cultivation of neuron PC12 cells and astrocyte C6 cells. ResultsBoth in vivo and in vitro results demonstrated that IL-12/IL-18 enhanced IFN-γ production in spinal neurons, which acted on IFN-γ receptors on neurons and astrocytes to upregulate CXCL10 expression in these cells, illustrating the pivotal role of IL-12 in the crosstalk between neurons and astrocytes. The role of IL-12 in pain regulation was elucidated for the first time within the nervous system. Additionally, its synergistic interaction with IL-18 on the downstream IFN-γ-CXCL10 pathway dramatically altered the activation of neurons and astrocytes. And AV could suppress CXCL10 to alleviate NP by mediating the IL-12-IFN-γ-IFNGR signaling pathway. ConclusionsWe explored a new target for NP by regulating neuron-astrocyte crosstalk and provided a theoretical basis for AV in clinical use.

Cd99l2 regulates excitatory synapse development and restrains immediate-early gene activation.

Cd99 molecule-like 2 (Cd99l2) is a type I transmembrane protein that plays a role in the transmigration of leukocytes across vascular endothelial cells. Despite its high expression in the brain, the role of Cd99l2 remains elusive. We find that Cd99l2 is expressed primarily in neurons and positively regulates neurite outgrowth and the development of excitatory synapses. We demonstrate that Cd99l2 inversely regulates the expression of immediate-early genes (IEGs), including Arc, Egr1, and c-Fos, by inhibiting the activity of the transcription factors CREB and SRF. Neuronal inactivation increases the transport of Cd99l2 to the cell surface from recycling endosomes, thereby enhancing Cd99l2-mediated inhibitory signaling. Additionally, Cd99l2 knockout mice exhibit impaired excitatory synaptic transmission and plasticity in the hippocampus, along with deficits in spatial memory and contextual fear conditioning. Based on these findings, we propose that neuronal Cd99l2 functions as a synaptic cell adhesion molecule that inversely controls neuronal activation.

Single-Cell RNA-Sequencing of Zebrafish Olfactory Epithelium Identifies Odor-Responsive Candidate Olfactory Receptors.

Single-cell RNA-sequencing (scRNA-seq) is a powerful method to comprehensively overlook gene expression profiles of individual cells in various tissues, providing fundamental datasets for classification of cell types and further functional analyses. Here we adopted scRNA-seq analysis for the zebrafish olfactory sensory neurons which respond to water-borne odorants and pheromones to elicit various behaviors crucial for survival and species preservation. Firstly, a single-cell dissociation procedure of the zebrafish olfactory rosettes was optimized by using cold-active protease, minimizing artifactual neuronal activation. Secondly, various cell types were classified into distinct clusters, based on the expressions of well-defined marker genes. Notably, we validated non-overlapping expressions of different families of olfactory receptors among the clusters of olfactory sensory neurons. Lastly, we succeeded in estimating candidate olfactory receptors responding to a particular odor stimulus by carefully scrutinizing correlated expressions of immediate early genes. Thus, scRNA-seq is a useful measure for the analysis of olfactory sensory neurons not only in classifying functional cell types but also in identifying olfactory receptor genes for given odorants and pheromones.

The Intrinsic Neuronal Activation of the CXCR4 Signaling Axis Is Associated with a Pro-Regenerative State in Cervical Primary Sensory Neurons Conditioned by a Sciatic Nerve Lesion.

CXCL12 and CXCR4 proteins and mRNAs were monitored in the dorsal root ganglia (DRGs) of lumbar (L4-L5) and cervical (C7-C8) spinal segments of naïve rats, rats subjected to sham operation, and those undergoing unilateral complete sciatic nerve transection (CSNT) on post-operation day 7 (POD7). Immunohistochemical, Western blot, and RT-PCR analyses revealed bilaterally increased levels of CXCR4 protein and mRNA in both lumbar and cervical DRG neurons after CSNT. Similarly, CXCL12 protein levels increased, and CXCL12 mRNA was upregulated primarily in lumbar DRGs ipsilateral to the nerve lesion. Intrathecal application of the CXCR4 inhibitor AMD3100 following CSNT reduced CXCL12 and CXCR4 protein levels in cervical DRG neurons, as well as the length of afferent axons regenerated distal to the ulnar nerve crush. Furthermore, treatment with the CXCR4 inhibitor decreased levels of activated Signal Transducer and Activator of Transcription 3 (STAT3), a critical transforming factor in the neuronal regeneration program. Administration of IL-6 increased CXCR4 levels, whereas the JAK2-dependent STAT3 phosphorylation inhibitor (AG490) conversely decreased CXCR4 levels. This indicates a link between the CXCL12/CXCR4 signaling axis and IL-6-induced activation of STAT3 in the sciatic nerve injury-induced pro-regenerative state of cervical DRG neurons. The role of CXCR4 signaling in the axon-promoting state of DRG neurons was confirmed through in vitro cultivation of primary sensory neurons in a medium supplemented with CXCL12, with or without AMD3100. The potential involvement of conditioned cervical DRG neurons in the induction of neuropathic pain is discussed.

Spinally targeted paired associated stimulation with high-frequency peripheral component induces spinal level plasticity in healthy subjects

A novel variant of paired-associative stimulation (PAS) consisting of high-frequency peripheral nerve stimulation (PNS) and high-intensity transcranial magnetic stimulation (TMS) above the motor cortex, called high-PAS, can lead to improved motor function in patients with incomplete spinal cord injury. In PAS, the interstimulus interval (ISI) between the PNS and TMS pulses plays a significant role in the location of the intended effect of the induced plastic changes. While conventional PAS protocols (single TMS pulse often applied with intensity close to resting motor threshold, and single PNS pulse) usually require precisely defined ISIs, high-PAS can induce plasticity at a wide range of ISIs and also in spite of small ISI errors, which is helpful in clinical settings where precise ISI determination can be challenging. However, this also makes the determination of high-PAS level of plasticity induction more challenging and calls for more research on the mechanism of action of high-PAS. We sought to determine if the TMS-induced orthodromic activation in upper motor neurons and PNS-induced antidromic activation in lower motor neurons arriving simultaneously to the intervening synapses at the spinal cord level can be shown to induce acute changes at the targeted location, unlike an otherwise identical but cortically targeted equivalent. Ten healthy subjects participated in two separate sessions, where high-PAS induced activation was set to target spinal (SPINAL) or cortical (CORTICAL) levels with ISI manipulation between otherwise identically applied TMS and PNS pulses. The outcomes were assessed with motor-evoked potentials (MEPs) and Hoffmann (H)-reflex before (PRE), immediately after, and 30 and 60 min after (POST, POST30, POST60) the intervention. MEPs were significantly enhanced in both interventions. In the SPINAL but not in the CORTICAL session, maximal H-reflex amplitudes significantly increased at two timepoints, indicating an increase in spinal excitability. The H/M ratio (maximal H-reflex normalized to maximal M-wave) also showed a significant increase from PRE to POST30 timepoint in the SPINAL session when compared with the CORTICAL equivalent. These results confirm that spinally targeted high-PAS with individualized ISIs indeed has an effect at the spinal level in the sensorimotor system. High-PAS is a novel PAS variant that has shown promising results in motor rehabilitation of individuals with SCI and these new findings contribute to the understanding of its mechanism of action. This provides further evidence for high-PAS as an option for clinical settings to target plasticity at different levels of the corticospinal tract.

Dexmedetomidine accelerates photoentrainment and affects sleep structure through the activation of SCNVIP neurons

Dexmedetomidine (DexM), a highly selective α2-adrenoceptor agonist, significantly reduces postoperative adverse effects, including sleep and circadian rhythm disruptions. Vasoactive intestinal peptide neurons in the suprachiasmatic nucleus (SCNVIP) regulate the synchronization of circadian rhythms with the external environment in mammals. We investigate the effects of DexM on sleep and circadian rhythms, as well as the underlying mechanisms. Using electrophysiological and chemogenetic methods, along with locomotor activity and electroencephalogram/electromyogram recordings, we found that DexM accelerates the rate of re-entrainment following an 8-hour phase advance in the 12-hour light:12-hour dark cycle, increases the amount of non-rapid eye movement sleep, and decreases the mean duration of rapid eye movement sleep. Chemogenetic inhibition of SCNVIP neurons hinders the acceleration of re-entrainment and the changes in the sleep-wakefulness cycle induced by DexM. Electrophysiological results show that DexM increases the firing rate and the frequency of spontaneous glutamatergic postsynaptic currents while decreasing the frequency of spontaneous GABAergic PSCs in SCNVIP neurons through the α2-adrenergic receptor. Additionally, DexM reduces the frequency of miniature GABAergic PSCs in SCNVIP neurons. In conclusion, these findings suggest that DexM promotes sleep and maintains the coordination of circadian rhythms with the external environment by activating SCNVIP neurons through the α2-adrenoceptor.

Targeting Tiam1 enhances hippocampal-dependent learning and memory in the adult brain and promotes NMDA receptor-mediated synaptic plasticity and function.

Excitatory synapses and the actin-rich dendritic spines on which they reside are indispensable for information processing and storage in the brain. In the adult hippocampus, excitatory synapses must balance plasticity and stability to support learning and memory. However, the mechanisms governing this balance remain poorly understood. Tiam1 is an actin cytoskeleton regulator prominently expressed in the dentate gyrus (DG) throughout life. Previously, we showed that Tiam1 promotes dentate granule cell synapse and spine stabilization during development, but its role in the adult hippocampus remains unclear. Here, we deleted Tiam1 from adult forebrain excitatory neurons (Tiam1fKO ) and assessed the effects on hippocampal-dependent behaviors. Adult male and female Tiam1fKO mice displayed enhanced contextual fear memory, fear extinction, and spatial discrimination. Investigation into underlying mechanisms revealed that dentate granule cells from Tiam1fKO brain slices exhibited augmented synaptic plasticity and NMDA-type glutamate receptor (NMDAR) function. Additionally, Tiam1 loss in primary hippocampal neurons blocked agonist-induced NMDAR internalization, reduced filamentous actin levels, and promoted activity-dependent spine remodeling. Notably, strong NMDAR activation in wild-type hippocampal neurons triggered Tiam1 loss from spines. Our results suggest that Tiam1 normally constrains hippocampal-dependent learning and memory in the adult brain by restricting NMDAR-mediated synaptic plasticity in the DG. We propose that Tiam1 achieves this by limiting NMDAR availability at synaptic membranes and stabilizing spine actin cytoskeleton, and that these constraints can be alleviated by activity-dependent degradation of Tiam1. These findings reveal a previously unknown mechanism restricting hippocampal synaptic plasticity and highlight Tiam1 as a therapeutic target for enhancing cognitive function.Significance statement The precise and dynamic regulation of excitatory synapses within hippocampal circuits is indispensable for learning and memory. These specialized connections must remain malleable to support the acquisition of relevant new information, but stable enough to protect the loss of previously stored memories. Dysregulation of this intricate balance drives cognitive decline following central nervous system injury and disease. Here, we establish the Rac1 guanine nucleotide exchange factor Tiam1 as an essential regulator of this balance that functions in the adult hippocampus to limit learning and memory. Our findings identify a previously unknown mechanism for restricting hippocampal synaptic plasticity that represents a potential therapeutic target for improving cognitive function.

Coherent Changes in Neural Motor Network Activity during Levodopa-Induced Dyskinesia in a Rat Model of Parkinson's Disease.

Long-term use of levodopa, a metabolic precursor of dopamine (DA) for alleviation of motor symptoms in Parkinson's disease (PD), can cause a serious side effect known as levodopa-induced dyskinesia (LID). With the development of LID, high-frequency gamma oscillations (~100 Hz) are registered in the motor cortex (MCx) in patients with PD and rats with experimental PD. Studying alterations in the activity within major components of motor networks during transition from levodopa-off state to dyskinesia can provide useful information about their contribution to the development of abnormal gamma oscillations and LID. Freely moving rats with unilateral 6-hydroxydopamine hydrobromide (6-OHDA)-induced nigral DA cell lesions were administered a high dose of levodopa for 7 days. Local field potentials (LFPs) and neuronal activity were recorded from electrodes implanted in the motor cortex (MCx), ventromedial nucleus of the thalamus (VM), and substantia nigra pars reticulata nucleus (SNpr). Levodopa reduced the power of beta oscillations (30-36 Hz) associated with bradykinesia in PD rats in three divisions of the motor neural network (MCx, VM, and SNpr) and prompted subsequent emergence of robust high-frequency gamma oscillations (80-120 Hz) in VM and MCx, but not SNpr, LFPs. Gamma oscillations were strongly associated with the occurrence of abnormal involuntary movements (AIMs) and accompanied by an increase in spiking rates in the VM and MCx and enlarged spike-LFP synchronization with cortical gamma oscillations (68% in the VM and 34% in the MCx). In contrast, SNpr LFPs did not exhibit gamma oscillations during LID, and neuronal activity in most recordings (87%) was largely decreased and not synchronized with VM or MCx LFPs. Administration of the antidyskinetic drug 8-hydroxy-2-(dipropylamino)-tetraline hydrobromide (8-OH-DPAT) restored the initial characteristics of LFPs (30-36 Hz oscillations), rates of neuronal activity, and bradykinesia. Inhibition of VM neurons by the gamma-aminobutyric acid (GABA-A)-agonist muscimol during LID eliminated high gamma oscillations in the MCx and VM, but not dyskinesia, suggesting that gamma oscillations are not critical for the expression of AIMs. In contrast, chemogenetic activation of SNpr neurons during LID eliminated both gamma oscillations and dyskinesia. These findings suggest that levodopa treatment leads to crucial reduction of inhibitory control over motor networks due to a large decline in spiking of most SNpr GABAergic projecting neurons, which causes persistent hyperactivity in motor circuits, leading to the appearance of thalamocortical gamma oscillations and LID.

Assessment of human emotional reactions to visual stimuli "deep-dreamed" by artificial neural networks.

While the fact that visual stimuli synthesized by Artificial Neural Networks (ANN) may evoke emotional reactions is documented, the precise mechanisms that connect the strength and type of such reactions with the ways of how ANNs are used to synthesize visual stimuli are yet to be discovered. Understanding these mechanisms allows for designing methods that synthesize images attenuating or enhancing selected emotional states, which may provide unobtrusive and widely-applicable treatment of mental dysfunctions and disorders. The Convolutional Neural Network (CNN), a type of ANN used in computer vision tasks which models the ways humans solve visual tasks, was applied to synthesize ("dream" or "hallucinate") images with no semantic content to maximize activations of neurons in precisely-selected layers in the CNN. The evoked emotions of 150 human subjects observing these images were self-reported on a two-dimensional scale (arousal and valence) utilizing self-assessment manikin (SAM) figures. Correlations between arousal and valence values and image visual properties (e.g., color, brightness, clutter feature congestion, and clutter sub-band entropy) as well as the position of the CNN's layers stimulated to obtain a given image were calculated. Synthesized images that maximized activations of some of the CNN layers led to significantly higher or lower arousal and valence levels compared to average subject's reactions. Multiple linear regression analysis found that a small set of selected image global visual features (hue, feature congestion, and sub-band entropy) are significant predictors of the measured arousal, however no statistically significant dependencies were found between image global visual features and the measured valence. This study demonstrates that the specific method of synthesizing images by maximizing small and precisely-selected parts of the CNN used in this work may lead to synthesis of visual stimuli that enhance or attenuate emotional reactions. This method paves the way for developing tools that stimulate, in a non-invasive way, to support wellbeing (manage stress, enhance mood) and to assist patients with certain mental conditions by complementing traditional methods of therapeutic interventions.

Microglia‐Derived Vitamin D Binding Protein Mediates Synaptic Damage and Induces Depression by Binding to the Neuronal Receptor Megalin

AbstractVitamin D binding protein (VDBP) is a potential biomarker of major depressive disorder (MDD). This study demonstrates for the first time that VDBP is highly expressed in core emotion‐related brain regions of mice susceptible to chronic unpredictable mild stress (CUMS). Specifically, the overexpression of microglia (MG)‐derived VDBP in the prelimbic leads to depression‐like behavior and aggravates CUMS‐induced depressive phenotypes in mice, whereas conditional knockout of MG‐derived VDBP can reverse both neuronal damage and depression‐like behaviors. Mechanistically, the binding of MG‐derived VDBP with the neuronal receptor megalin mediates the downstream SRC signaling pathway, leading to neuronal and synaptic damage and depression‐like behaviors. These events may be caused by biased activation of inhibitory neurons and excitatory–inhibitory imbalance. Importantly, this study has effectively identified MG‐derived VDBP as a pivotal mediator in the interplay between microglia and neurons via its interaction with the neuronal receptor megalin and intricate downstream impacts on neuronal functions, thus offering a promising therapeutic target for MDD.

Enteroendocrine Cells Sense Sucrose and Alter Enteric Neuron Excitability via Insulin Signaling.

Neurosensory circuits of the gastrointestinal tract sense microbial and nutrient changes in the gut; however, studying these circuits in vivo is hindered by invasive techniques and ethical concerns. Here, an in vitro model of enteroendocrine cells (EECs) and calcium reporting enteric neurons (ENs) is established and validated for functional signaling. Both mechanical and sucrose stimulation of co-cultures increased the percentage of neurons undergoing a calcium flux, indicating an action potential. Neuronal activation is blocked with either a piezo or insulin receptor blocker. At baseline, a flow only stimulus elicited 51.9% of neurons to activate in co-culture, which is decreased to 15.1% with a piezo blocker. Piezo blocked and sucrose stimulated EECs increased neuronal activation to 43.9%, and an insulin blocker reduced response to 12.4%. Since a cell line is used to model the EEC in the previous experiments, primary rat duodenal epithelium enriched for EECs are also stimulated and found to produced measurable insulin. This work shows the ability of EECs to produce insulin and for ENs to sense insulin. These results inspire further work on how insulin production outside the pancreas effects diabetes, insulin as a neurotransmitter, and exploration of additional nutritional and microbiotic stimuli on enteroendocrine-to-neuronal signaling.

Neuronal nitric oxide synthase activation by tadalafil protects neurological impairments in a zebrafish larva model of hyperammonemia.

Hyperammonaemia (HA) is a metabolic disorder characterized by increased ammonia levels in the blood and is associated with severe neurological impairments. Some previous findings have shown the involvement of the nitric oxide pathway in HA-induced neurological impairments. The current study explored the impact of tadalafil on neurological impairments induced by HA in a zebrafish larval model due to its reported indirect interactions with the nitric oxide pathway. HA was induced in zebrafish larvae by ammonium acetate exposure from 2 to 9 days post fertilization (dpf). Locomotor and cognitive functions were analysed following the treatment. The levels of gamma-aminobutyric acid (GABA), glutamate, and dopamine were measured in the larval head. The expression of genes associated with apoptosis (baxa and bcl2a), selected neurotransmitter receptors and bdnf was analysed. The protein levels of CREB and nNOS were also quantified. Tadalafil incubation reversed the HA-associated locomotor and cognitive impairments in larvae. The treatment attenuated GABA, dopamine, and glutamate levels. An upregulation in the expression of grin1a, gria2b, drd1b, drd2b, bdnf, and bcl2a, and downregulation of gabrz, gabrd, gabrg2 and baxa was observed following tadalafil treatment. The protein expression showed increased nNOS, p-CREB(Ser133), and decreased p-nNOS(Ser847) levels in the larvae incubated with tadalafil. The study concluded that tadalafil mitigates HA-induced neurological impairments by activating neuronal nitric oxide synthase. The study highlighted the possible application of tadalafil in the symptomatic management of neurological impairments in HA provided its efficacy and safety are further ensured in higher mammals.

Enabling Electric Field Model of Microscopically Realistic Brain.

Modeling brain stimulation at the microscopic scale may reveal new paradigms for various stimulation modalities. We present the largest map to date of extracellular electric field distributions within a layer L2/L3 mouse primary visual cortex brain sample. This was enabled by the automated analysis of serial section electron microscopy images with improved handling of image defects, covering a volume of 250 × 140 × 90 μm³. The map was obtained by applying a uniform brain stimulation electric field at three different polarizations and accurately computing microscopic field perturbations using the boundary element fast multipole method. We used the map to identify the effect of microscopic field perturbations on the activation thresholds of individual neurons. Previous relevant studies modeled a macroscopically homogeneous cortical volume. Our result shows that the microscopic field perturbations - an 'electric field spatial noise' with a mean value of zero - only modestly influence the macroscopically predicted stimulation field strengths necessary for neuronal activation. The thresholds do not change by more than 10% on average. Under the stated limitations and assumptions of our method, this result essentially justifies the conventional theory of "invisible" neurons embedded in a macroscopic brain model for transcranial magnetic and transcranial electrical stimulation. However, our result is solely sample-specific and is only relevant to this relatively small sample with 396 neurons. It largely neglects the effect of the microcapillary network. Furthermore, we only considered the uniform impressed field and a single-pulse stimulation time course.

17β-estradiol alleviated ferroptotic neuroinflammation by suppressing ATF4 in mouse model of Parkinson’s disease

Neuroinflammation induced by activation of microglial is a vital contributor to progression of Parkinson’s disease (PD), emerging evidences suggested that ferroptosis played a pivotal role in microglial activation and subsequent dopaminergic neuron loss. Nevertheless, the fundamental pathogenesis of that ferroptosis contributes to PD is not yet sufficiently understood. Based on GEO dataset, ferroptosis related genes were found to be enriched in PD patients and MPTP mouse model of PD, among them, ATF4 was found to be dramatically differentially expressed. In our study, ectopic expression of ATF4 augmented MPP+-induced cytotoxic and activation of BV2 cells with upregulated intracellular L-ROS, TLR4 and pNF-κB. Ectopic ATF4 effectively promoted transformation of microglial into M1 pro-inflammatory phenotype. 17β-estradiol (E2) attenuated expression of ATF4 in BV2 cells, silence of ATF4 enhanced protective effect of E2 on MPP+-treated BV2 cells. In MPTP-induced PD mouse model, administration of E2 further abated expression of ATF4 and inhibited expressions of pro-inflammatory cytokines and activation of TLR4/NF-κB pathway. Overall, E2 effectively counteracted TLR4/NF-κB signaling pathway by restraining ATF4 and inhibited inflammatory response triggered by ferroptosis, ultimately exerted anti-PD effects.

Aged mice show a reduction in 5-HT neurons and decreased cellular activation in the dentate gyrus when exposed to acute running.

Serotonin (5-HT) is an important neurotransmitter for cognition and neurogenesis in the dentate gyrus (DG), which occurs via movement stimulation such as physical activity. Brain 5-HT function changes secondary to aging require further investigation. We evaluated whether aged animals would present changes in the number of 5-HT neurons in regions such as the dorsal (DRN) and median (MRN) raphe nuclei and possible changes in the rate of cellular activation in the DG in response to acute running, as a reduction in 5-HT neurons could contribute to a decline in neuronal activation in the DG in response to physical activity in aged mice. This study was conducted on adult (3months old) and aged (19months old) male and female mice. Immunohistochemistry, microscopic analysis, and treadmill-running tests were also performed. The data revealed that in aged mice, a reduction in the number of 5-HT neurons in the DRN and MRN of male and female mice was observed. The reduction in the DRN was greater in females. Furthermore, aged animals demonstrate a lower rate of c-Fos labeling in the DG when stimulated by physical exercise. These data indicate that aging may be associated with a reduction in the number of 5-HT neurons in the DRN and MRN, which may lead to a decline in 5-HT availability in the target regions, including the DG. The reduced c-Fos expression in the DG after running in aged mice indicates a decreased response to physical activity, which is potentially linked to serotonergic deficits.