Neurotransmitter Research Articles

EPCO-38. IDENTIFYING THE MOLECULAR SIGNATURE OF INFILTRATING EDGE IN GLIOBLASTOMA AS DRIVERS OF TUMOUR INVASION AND RECURRENCE

Abstract Complete tumour resection in glioblastoma patients is not possible. Residual therapy-resistant edge-derived cells drive tumour recurrence and infiltrative expansion in glioblastoma. Features that are specific to malignant edge-derived cells may serve as predictive biomarkers to allow individual tailoring of the treatment plan to slow down tumour invasion and prevent tumour recurrence in GBM patients following standard therapy. Intratumoural spatial heterogeneity facilitates therapeutic resistance and recurrence in glioblastoma. Our knowledge on glioblastoma heterogeneity is mostly restricted to the surgically resectable tumour core, while the functional characterization of tumour cells at the infiltrating edge remains largely elusive due to the presence of normal functional brain tissue in the peritumoural lesion. Edge-derived cells exhibit larger capacity for infiltrative expansion and are the main drivers of treatment failure and tumour recurrence, making them action targets for novel treatment approaches in glioblastoma. To resolve the transcriptional heterogeneity of GBM within the spatial context, we profiled gene expression of different tumour regions (“edge” and “core”) obtained at initial surgical resection from primary and recurrent IDH-WT GBM patients with Visium 10x and GeoMx. We show that infiltrative edge-derived cells are spatially segregated and are characterized by regionally shared distinct genomic and transcriptomic signatures that promote invasiveness and underly disease recurrence. Tumour edge is enriched for neuronal signatures, while tumour core displays larger transcriptional subpopulation diversity and abundance of proliferative cells with a high capacity for self-renewal, consistent with the proliferative and cancer stem cell-enriched phenotype in early GBM progressors. Upregulated DEGs of tumour edge cells are significantly associated with ion regulation of transport, chemical synaptic transmission, and nervous system development. These modules may represent tumour cell hijacking of neuronal programs specifically at the tumour periphery as described in the context of glioma-neuron synaptic communication and formation of neurite-like microtubes. Upregulation of ion regulation transport at the tumour periphery indicates enhanced neuronal activity and excitability driving infiltrating growth.

Comparative specialization of intrinsic cardiac neurons in humans, mice and pigs

AbstractIntrinsic cardiac neurons (ICNs) play a crucial role in the proper functioning of the heart; yet a paucity of data pertaining to human ICNs exist. We took a multidisciplinary approach to complete a detailed cellular comparison of the structure and function of ICNs from mice, pigs and humans. Immunohistochemistry of whole and sectioned ganglia, transmission electron microscopy, intracellular microelectrode recording and dye filling for quantitative morphometry were used to define the neurophysiology, histochemistry and ultrastructure of these neurons across species. The densely packed, smaller ICNs of mouse lacked dendrites, formed axosomatic connections and had high synaptic efficacy constituting an obligatory synapse. At pig ICNs, a convergence of subthreshold cholinergic inputs onto extensive dendritic arbors supported greater summation and integration of synaptic input. Human ICNs were tonically firing, with synaptic stimulation evoking large suprathreshold EPSPs like mouse, and subthreshold potentials like pig. Ultrastructural examination of synaptic terminals revealed conserved architecture, yet small clear vesicles were larger in pigs and humans. The presence and localization of ganglionic neuropeptides was distinct, with abundant vasoactive intestinal polypeptide observed in human but not pig or mouse ganglia, and little substance P or calcitonin gene‐related peptide in pig ganglia. Action potential waveforms were similar, but human ICNs had larger after‐hyperpolarizations. Intrinsic excitability differed; 95% of human neurons were tonic, all pig neurons were phasic, and both phasic and tonic phenotypes were observed in mouse. In combination, this publicly accessible, multimodal atlas of ICNs from mice, pigs and humans identifies similarities and differences in the evolution of ICNs. imageKey points Intrinsic cardiac neurons (ICNs) are essential to the regulation of cardiac function. We investigated the neurochemistry, morphology, ultrastructure, membrane physiology and synaptic transmission of ICNs from donated human hearts in parallel with identical studies of ICNs from mice and pigs to create a publicly accessible cellular atlas detailing the structure and function of these neurons across species. In addition to presenting foundational data on human ICNs, this comparative study identifies both conserved and derived attributes of these neurons within mammals. The findings have significant implications for understanding the regulation of cardiac autonomic function in humans and may greatly influence strategies for neuromodulation in conditions such as atrial fibrillation and heart failure.

Genome-wide meta-analysis conducted in three large biobanks expands the genetic landscape of lumbar disc herniations

Given that lumbar disc herniation (LDH) is a prevalent spinal condition that causes significant individual suffering and societal costs, the genetic basis of LDH has received relatively little research. Our aim is to increase understanding of the genetic factors influencing LDH. We perform a genome-wide association analysis (GWAS) of LDH in the FinnGen project and in Estonian and UK biobanks, followed by a genome-wide meta-analysis to combine the results. In the meta-analysis, we identify 41 loci that have not been associated with LDH in prior studies on top of the 23 known risk loci. We detect LDH-associated loci in the vicinity of genes related to inflammation, disc-related structures, and synaptic transmission. Overall, our research contributes to a deeper understanding of the genetic factors behind LDH, potentially paving the way for the development of new therapeutics, prevention methods, and treatments for symptomatic LDH in the future.

PKA regulation of neuronal function requires the dissociation of catalytic subunits from regulatory subunits

Protein kinase A (PKA) plays essential roles in diverse cellular functions. However, the spatiotemporal dynamics of endogenous PKA upon activation remain debated. The classical model predicts that PKA catalytic subunits dissociate from regulatory subunits in the presence of cAMP, whereas a second model proposes that catalytic subunits remain associated with regulatory subunits following physiological activation. Here, we report that different PKA subtypes, as defined by the regulatory subunit, exhibit distinct subcellular localization at rest in CA1 neurons of cultured hippocampal slices. Nevertheless, when all tested PKA subtypes are activated by norepinephrine, presumably via the β-adrenergic receptor, catalytic subunits translocate to dendritic spines but regulatory subunits remain unmoved. These differential spatial dynamics between the subunits indicate that at least a significant fraction of PKA dissociates. Furthermore, PKA-dependent regulation of synaptic plasticity and transmission can be supported only by wildtype, dissociable PKA, but not by inseparable PKA. These results indicate that endogenous PKA regulatory and catalytic subunits dissociate to achieve PKA function in neurons.

Exploring the potential pharmacological mechanism of aripiprazole against hyperprolactinemia based on network pharmacology and molecular docking

The current primary therapeutic approach for schizophrenia is antipsychotic medication, and antipsychotic-induced hyperprolactinemia occurs in 40–80% of patients with schizophrenia. Aripiprazole, an atypical antipsychotic belonging to the quinolinone derivative class, can reduce the likelihood of developing hyperprolactinemia, but the pharmacological mechanisms of this reduction are unknown. This study aimed to explore the molecular mechanism of action of aripiprazole in treating hyperprolactinemia based on network pharmacology and molecular docking techniques. This study identified a total of 151 potential targets for aripiprazole from the DrugBank, TCMSP, BATMAN-TCM, TargetNet, and SwissTargetPrediction databases. Additionally, 71 hyperprolactinemia targets were obtained from the PharmGKB, DrugBank, TTD, GeneCards, OMIM, and DisGENET databases. Utilizing Venny 2.1.0 software, an intersection of 27 genes was identified between aripiprazole and hyperprolactinemia. To construct a common target protein–protein interaction (PPI) network, the common targets obtained from both sources were input into the STRING database. The resulting PPI network was then imported into Cytoscape 3.7.2 software, which identified eight core targets associated with aripiprazole’s treatment of hyperprolactinemia. Subsequently, a PPI network was established for these targets. Enrichment analysis of the key targets was conducted using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes in the DAVID database. Additionally, molecular docking verification of the interaction between aripiprazole and the core targets was performed using AutoDock Vina software. Aripiprazole’s intervention in hyperprolactinemia primarily targets the following core proteins: Solute Carrier Family 6 Member 3 (SLC6A3), monoamine oxidase (MAO-B), Dopamine D2 receptor (DRD2), 5-hydroxytryptamine (serotonin) receptor 2A (HTR2A), 5-hydroxytryptamine (serotonin) receptor 2C (HTR2C), cytochrome P450 2D6 (CYP2D6), Dopamine D1 receptor (DRD1), Dopamine D4 receptor (DRD4). These targets are predominantly involved in biological processes such as the adenylate cyclase-activating adrenergic receptor signaling pathway, G-protein coupled receptor signaling pathway coupled to cyclic nucleotide second messenger, phospholipase C-activating G-protein coupled receptor signaling pathway, chemical synaptic transmission, and response to xenobiotic stimulus. Primary enrichment occurs in signaling pathways such as the neuroactive ligand-receptor interaction and serotonergic synapse pathways. Molecular docking results demonstrate a favorable affinity between aripiprazole and the core target proteins MAO-B, DRD2, SLC6A3, HTR2C, HTR2A, CYP2D6, DRD4, and DRD1. Network pharmacology predicted potential targets and signaling pathways for aripiprazole’s intervention in hyperprolactinemia, offering theoretical support and a reference basis for optimizing clinical strategies and drug development involving aripiprazole.

Transcriptomic and de novo proteomic analyses of organotypic entorhino-hippocampal tissue cultures reveal changes in metabolic and signaling regulators in TTX-induced synaptic plasticity

Understanding the mechanisms of synaptic plasticity is crucial for elucidating how the brain adapts to internal and external stimuli. A key objective of plasticity is maintaining physiological activity states during perturbations by adjusting synaptic transmission through negative feedback mechanisms. However, identifying and characterizing novel molecular targets orchestrating synaptic plasticity remains a significant challenge. This study investigated the effects of tetrodotoxin (TTX)-induced synaptic plasticity within organotypic entorhino-hippocampal tissue cultures, offering insights into the functional, transcriptomic, and proteomic changes associated with network inhibition via voltage-gated sodium channel blockade. Our experiments demonstrate that TTX treatment induces substantial functional plasticity of excitatory synapses, as evidenced by increased miniature excitatory postsynaptic current (mEPSC) amplitudes and frequencies in both dentate granule cells and CA1 pyramidal neurons. Correlating transcriptomic and proteomic data, we identified novel targets for future research into homeostatic plasticity, including cytoglobin, SLIT-ROBO Rho GTPase Activating Protein 3, Transferrin receptor, and 3-Hydroxy-3-Methylglutaryl-CoA Synthase 1. These data provide a valuable resource for future studies aiming to understand the orchestration of homeostatic plasticity by metabolic pathways in distinct cell types of the central nervous system.

Functional implications of the exon 9 splice insert in GluK1 kainate receptors

Kainate receptors are key modulators of synaptic transmission and plasticity in the central nervous system. Different kainate receptor isoforms with distinct spatiotemporal expressions have been identified in the brain. The GluK1-1 splice variant receptors, which are abundant in the adult brain, have an extra fifteen amino acids inserted in the amino-terminal domain (ATD) of the receptor resulting from alternative splicing of exon 9. However, the functional implications of this post-transcriptional modification are not yet clear. We employed a multi-pronged approach using cryogenic electron microscopy, electrophysiology, and other biophysical and biochemical tools to understand the structural and functional impact of this splice insert in the extracellular domain of GluK1 receptors. Our study reveals that the splice insert alters the key gating properties of GluK1 receptors and their modulation by the cognate auxiliary Neuropilin and tolloid-like (Neto) proteins 1 and 2. Mutational analysis identified the role of crucial splice residues that influence receptor properties and their modulation. Furthermore, the cryoEM structure of the variant shows that the presence of exon 9 in GluK1 does not affect the receptor architecture or domain arrangement in the desensitized state. Our study thus provides the first detailed structural and functional characterization of GluK1-1a receptors, highlighting the role of the splice insert in modulating receptor properties and their modulation.

Stochastic neuropeptide signals compete to calibrate the rate of satiation.

Neuropeptides have important roles in neural plasticity, spiking and behaviour1. Yet, many fundamental questions remain regarding their spatiotemporal transmission, integration and functions in the awake brain. Here we examined how MC4R-expressing neurons in the paraventricular nucleus of the hypothalamus (PVHMC4R) integrate neuropeptide signals to modulate feeding-related fast synaptic transmission and titrate the transition to satiety2-6. We show that hunger-promoting AgRP axons release the neuropeptide NPY to decrease the second messenger cAMP in PVHMC4R neurons, while satiety-promoting POMC axons release the neuropeptide αMSH to increase cAMP. Each release event is all-or-none, stochastic and can impact multiple neurons within an approximately 100-µm-diameter region. After release, NPY and αMSH peptides compete to control cAMP-the amplitude and persistence of NPY signalling is blunted by high αMSH in the fed state, while αMSH signalling is blunted by high NPY in the fasted state. Feeding resolves this competition by simultaneously elevating αMSH release and suppressing NPY release7,8, thereby sustaining elevated cAMP in PVHMC4R neurons throughout a meal. In turn, elevated cAMP facilitates potentiation of feeding-related excitatory inputs with each bite to gradually promote satiation across many minutes. Our findings highlight biochemical modes of peptide signal integration and information accumulation to guide behavioural state transitions.

Functional implications of the exon 9 splice insert in GluK1 kainate receptors.

Kainate receptors are key modulators of synaptic transmission and plasticity in the central nervous system. Different kainate receptor isoforms with distinct spatiotemporal expressions have been identified in the brain. The GluK1-1 splice variant receptors, which are abundant in the adult brain, have an extra fifteen amino acids inserted in the amino-terminal domain (ATD) of the receptor resulting from alternative splicing of exon 9. However, the functional implications of this post-transcriptional modification are not yet clear. We employed a multi-pronged approach using cryogenic electron microscopy, electrophysiology, and other biophysical and biochemical tools to understand the structural and functional impact of this splice insert in the extracellular domain of GluK1 receptors. Our study reveals that the splice insert alters the key gating properties of GluK1 receptors and their modulation by the cognate auxiliary Neuropilin and tolloid-like (Neto) proteins 1 and 2. Mutational analysis identified the role of crucial splice residues that influence receptor properties and their modulation. Furthermore, the cryoEM structure of the variant shows that the presence of exon 9 in GluK1 does not affect the receptor architecture or domain arrangement in the desensitized state. Our study thus provides the first detailed structural and functional characterization of GluK1-1a receptors, highlighting the role of the splice insert in modulating receptor properties and their modulation.

Advances in Graphene Field Effect Transistors (FETs) for Amine Neurotransmitter Sensing

Amine neurotransmitters (NTs) are crucial in the central nervous system, and dysregulation in their levels is implicated in a spectrum of neurological disorders. Thus, a precise and timely assessment of their concentrations is critical for early diagnosis and treatment efficacy monitoring. Graphene-based field effect transistors (GFETs) have become a ground-breaking instrument in the detection of these NTs because of their exceptional electrical characteristics and adaptability. This paper summarises the significant advancements in GFET biosensors in amine NT detection and highlights developments in the selectivity, sensitivity, and limit of detection (LOD) attained by selecting various graphene materials and functionalisation approaches.

Bio‐Realistic Synaptic‐Replicated “V” Type Oxygen Vacancy Memristor

AbstractThe development of an artificial synaptic device is essential for the construction of a brain‐like neuromorphic computing architecture. In this study, the goal is to create a multi‐layer HfOx memristor with a “V” type oxygen vacancy (Vo) distribution to mimic the function of calcium ions (Ca2+) during synaptic information transmission. By adjusting voltage and compliance current (Icc), the HfOx memristor can open or close different levels of volt‐controlled Ca2+ channels, thus enabling the replication of synaptic structure, neurotransmitter release/acceptor, and information transmission. A mathematical model is adopted to describe the behavior of volt‐controlled Ca2+ channels, which demonstrates that the device exhibits consistent characteristics with biological synapses. The device forms an “hourglass” conductive filament (CF) within its middle functional layer, allowing for precise control over filament formation and positioning. This results in ultra‐low power consumption for erasing (581 fJ), fast erasing speed (10 ns), and a low resistance difference coefficient of only 1.8%. Furthermore, the device successfully simulates the physical dynamics of Ca2+ during short‐term potentiation (STP) and long‐term potentiation (LTP) in biological synapses while replicating various guided synaptic behaviors. This study provides a straightforward method for memristors to realize bio‐realistic artificial neuromorphic applications.

Identification of Sequential Molecular Mechanisms and Key Biomarkers in Early Glaucoma by Integrated Bioinformatics Analysis.

Glaucoma is a neurodegenerative disease characterized by progressive optic nerve degeneration and retinal ganglion cell (RGC) loss. In early glaucoma, before obvious axon loss, highly organized pathological processes in RGCs occur sequentially, involving axons, dendrites and synaptic terminals. The optic nerve head (ONH) is the critical structure of early glaucomatous neurodegeneration. Taking advantage of high-throughput data from the ONH and the weighted gene coexpression network analysis (WGCNA) method, the current study aims to gain insight into the full scope of pathological events in early glaucoma and define their chronological sequence. The expression profiles of GSE26299, GSE110019, and GSE139605, which measure ONH gene expression in different glaucoma models, were downloaded from the Gene Expression Omnibus (GEO) database. In GSE26299, which uses 10.5-month-old DBA/2J mice, WGCNA was utilized to construct a gene coexpression network, and the most significant modules of early (NOE), moderate (MOD) and severe (SEV) glaucoma were identified. The differentially expressed genes (DEGs) of GSE110019 and GSE139605 significantly overlapped with the correlated module of the MOD group, so the 3 gene sets were analyzed together. Pathway enrichment analysis via the GO, KEGG, and Reactome pathways was subsequently performed, followed by protein‒protein interaction (PPI) analysis to screen key genes associated with each stage. Several hub gene expression patterns were identified in a glucocorticoid-induced glaucoma (GIG) model via quantitative PCR and immunostaining. The pink module was positively correlated with the NOE group (r = 0.48, p = 4e-04) and negatively correlated with the glaucoma stage (r = -0.88, p = 3e-17). The genes in the pink module were enriched in the synaptic transmission and axonal transport pathways. The tan module was negatively correlated with the NOE group (r = -0.43, p = 0.002) and positively correlated with the glaucoma stage (r = 0.77, p = 7e-11). The genes in the tan module were associated with pathways such as tight junctions, retinol metabolism, and linoleic acid metabolism. The purple module was positively correlated with the MOD group (r = 0.64, p = 5e-07). The common genes among the purple module and the DEGs of the two other datasets were enriched in pathways related to mitotic cell division, cytokine activity, and the extracellular matrix (ECM). The hub genes identified by PPI included Nrn1, Cplx1, Timp1, and Cdk1. Quantitative PCR and immunostaining confirmed that Limk1 expression was increased in the ONH of GIG mice. In early glaucomatous neuropathy, intrinsic changes in RGCs precede the activation of glial cells and ECM remodeling. These latter events are common pathological changes observed in the ONH in both cats and mice. Our study may provide new targets for the early detection and treatment of glaucoma.

Unraveling the Role of Wnt Signaling Pathway in the Pathogenesis of Autism Spectrum Disorder (ASD): A Systematic Review.

Autism spectrum disorder (ASD), or simply autism, is a neurodevelopmental disorder characterized by social communication deficit, restricted interests, and repetitive behavior. Several studies suggested a link between autism and the dysregulation of the Wnt signaling pathway which is mainly involved in cell fate determination, cell migration, cell polarity, neural patterning, and organogenesis. Despite the absence of effective therapy, significant progress has been made in understanding the pathogenesis of ASD. Neuropharmacological studies showed that drugs acting on the Wnt pathway like Canagliflozin can alleviate autistic-like behavior in animal models. Hence, this pathway could potentially be a futuristic therapeutic target to mitigate autism's symptoms. This systematic review aims to collect and analyze evidence that elucidates how alterations in the Wnt pathway may contribute to the pathogenesis of autism in animal models at the molecular, cellular, and physiological levels. Comprehensive searches were conducted across multiple databases, including PubMed, Web of Science, Embase, and Scopus to identify relevant studies up to March 2024. The inclusion criteria encompassed experimental studies that focused on the link between autism and this pathway, and the quality assessment was ensured by SYRCLE's risk of bias tools. Collectively, the included articles highlighted the possible implication of this pathway in the abnormalities found in autism, which impacted processes such as energy metabolism, oxidative stress, and neurogenesis. These alterations could underlie autistic behavior by affecting synaptic transmission and mitochondrial function.

Transcriptomic evidence of black soybean ethanolic extract and 2-aminobutyric acid in suppressing neuroinflammation and enhancing synaptic transmission

IntroductionRecently, the awareness of the beneficial utilization of natural bioactive compounds in treating neuroinflammation has gained particular attention. We aimed to understand the anti-neuroinflammatory effect of black soybeans (Glycine max (L.) Merr) ethanolic extract (BBEE) and its bioactive compound, 2-aminobutyric acid (2-AB), against LPS-induced SH-SY5Y cells. MethodCell viability and the optimum therapeutic dose were confirmed by MTT assay. We conducted a whole-transcriptomic analysis of BBEE and 2-AB in LPS-induced SH-SY5Y cells using microarray normalized with SST-RMA. DEGs were selected based on p-value < 0.05 and fold change > 2, and validated by RT-qPCR and immunocytochemical analyses. ResultsWe found that both BBEE and 2-AB down-regulated the expression of inflammatory cytokines IL6 and TNFA under LPS-induced conditions. This was also observed in the microarray data, showing downregulation of several inflammatory pathways, such as NF-kB, and IL6-JAK/STAT3-signaling pathways. In contrast, it upregulated the expression of CALML3, GRIN2, and GRIA2 gene expressions, which influence the AMPK and CAMK2 signaling pathways, indicating the potential of BBEE in neurotransmission and synaptic function. Also, immunofluorescence analysis revealed that 2-AB treatment significantly increased PSD-95 and Ca2+ levels, suggesting its effect on synaptic transmission essential for brain function. ConclusionOur findings suggest the potential anti-neuroinflammatory effects of BBEE and 2-AB, which may offer therapeutic and preventive benefits in mitigating neurological disorders. Given that BB is widely consumed in many Asian countries, our study may encourage its incorporation into the daily diet to slow inflammation-induced neurodegenerative disorders, reduce age-related cognitive decline, and enhance overall brain function.

The role and advance of ubiquitination and deubiquitination in depression pathogenesis and treatment.

Depression is a common neuropsychiatric disease that is characterized by long-term, repeated low mood, pain and despair, pessimism, and even suicidal tendencies. Increasing evidence has shown that ubiquitination and deubiquitination are closely related to the occurrence of depression, including pathological morphogenesis, neuroplasticity, synaptic transmission, neuroinflammation, and so forth. The development of depression is regulated by intracellular proteins that undergo various posttranslational modifications, including ubiquitination, which falls under the epigenetics category. Although there have been studies and reviews of literature on epigenetics and depression, a systematic review of ubiquitination modification and depression has not been reported. In addition, with the deepening of research on depression and ubiquitination, the development of drugs targeting the ubiquitin system has gradually increased, but it is still not mature, so there is an urgent need to find new antidepressant drug targets. E3 ubiquitin ligases and deubiquitinating enzymes can regulate the occurrence and development of depression in a variety of ways, which may be a direction for the treatment of depression in the future. Therefore, this review describes the latest progress of ubiquitination and deubiquitination in the regulation of depression, summarizes the published signal pathways of ubiquitination and deubiquitination involved in depression, emphasizes the targets and mechanisms of E3 ubiquitin ligases and deubiquitinase in the regulation of depression, and further discusses the therapeutic targets of targeting ubiquitination modification systems to regulate depression.

Plastic Events of the Vestibular Nucleus: the Initiation of Central Vestibular Compensation.

Vestibular compensation is a physiological response of the vestibular organs within the inner ear. This adaptation manifests during consistent exposure to acceleration or deceleration, with the vestibular organs incrementally adjusting to such changes. The molecular underpinnings of vestibular compensation remain to be fully elucidated, yet emerging studies implicate associations with neuroplasticity and signal transduction pathways. Throughout the compensation process, the vestibular sensory neurons maintain signal transmission to the central equilibrium system, facilitating adaptability through alterations in synaptic transmission and neuronal excitability. Notable molecular candidates implicated in this process include variations in ion channels and neurotransmitter profiles, as well as neuronal and synaptic plasticity, metabolic processes, and electrophysiological modifications. This study consolidates the current understanding of the molecular events in vestibular compensation, augments the existing research landscape, and evaluates contemporary therapeutic strategies. Furthermore, this review posits potential avenues for future research that could enhance our comprehension of vestibular compensation mechanisms.

Norepinephrine triggers glutamatergic long-term potentiation in hypothalamic paraventricular nucleus magnocellular neuroendocrine cells through postsynaptic β1-AR/PKA signaling pathway in vitro in rats.

Norepinephrine (NE) modulates synaptic transmission and long-term plasticity through distinct subtype adrenergic receptor (AR)-mediated-intracellular signaling cascades. However, the role of NE modulates glutamatergic long-term potentiation (LTP) in the hypothalamic paraventricular nucleus (PVN) magnocellular neuroendocrine cells (MNCs) is unclear. We here investigate the effect of NE on high frequency stimulation (HFS)-induced glutamatergic LTP in rat hypothalamic PVN MNCs in vitro, by whole-cell patch-clamp recording, biocytin staining and pharmacological methods. Delivery of HFS induced glutamatergic LTP with a decrease in N2/N1 ratio in the PVN MNCs, which was enhanced by application of NE (100 nM). HFS-induced LTP was abolished by the blockade of N-methyl-D-aspartate receptors (NMDAR) with D-APV, but it was rescued by the application of NE. NE failed to rescue HFS-induced LTP of MNCs in the presence of a selective β1-AR antagonist, CGP 20712. However, application of β1-AR agonist, dobutamine HCl rescued HFS-induced LTP of MNCs in the absence of NMDAR activity. In the absence of NMDAR activity, NE failed to rescue HFS-induced MNC LTP when protein kinase A (PKA) was inhibited by extracellular applying KT5720 or intracellular administration of PKI. These results indicate that NE activates β1-AR and triggers HFS to induce a novel glutamatergic LTP of hypothalamic PVN NMCs via the postsynaptic PKA signaling pathway in vitro in rats.

Microglia-Dependent Peripheral Neuropathic Pain in Adulthood Following Adolescent Exposure to Morphine in Male Rats

Persistent effects of adolescent morphine exposure on neurobiological processes and behaviors in adulthood have been partially identified. Hypersensitivity following adolescent exposure to morphine is a complex and multifaceted phenomenon whose underlying mechanisms remain largely unknown. This study aimed to investigate the involvement of microglia in neuropathic pain sensitivity following adolescent morphine exposure, focused on hippocampal genes expression and plasticity. To achieve this, adolescent male Wistar rats received morphine, along with minocycline, to inhibit microglial activity. The allodynia and hyperalgesia of adult rats were evaluated using von-Frey filaments and the Hargreaves plantar test in both baseline and neuropathic pain conditions. Hippocampal genes expression was analyzed following the behavioral tests. The plasticity of the Schaffer-CA1 hippocampal synapses was also assessed using field potential recording following neuropathy. Results showed that adolescent morphine exposure exacerbated the allodynia and hyperalgesia in both baseline and neuropathic pain states in adult rats, which was significantly reduced by the co-administration of minocycline during adolescence. Neuropathy in adult rats was found to increase hippocampal expression of inflammatory mediators, but adolescent morphine prevented this effect. Additionally, we observed a reduction in the baseline synaptic transmission and long-term potentiation (LTP) at the Schaffer-CA1 hippocampal synapses after neuropathy in adult rats following adolescent exposure to morphine. The reduction of synaptic activity was not altered by the co-administration of minocycline with morphine during adolescence. It is concluded that microglia play an important role in mediating hypersensitivity induced by adolescent morphine exposure, although hippocampal microglia may not be directly involved in this process.

Neuronal connectivity, behavioral, and transcriptional alterations associated with the loss of MARK2.

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 invitro. However, despite its genetic association with several neurological disorders, the invivo impact of MARK2 on neuronal connectivity and cognitive functions remains unclear. Here, we demonstrate that the loss of MARK2 invivo 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 invivo role of MARK2 in governing synaptic connectivity, neuronal excitability, and cognitive functions.

Spatially resolved transcriptomic signatures of hippocampal subregions and Arc-expressing ensembles in active place avoidance memory

The rodent hippocampus is a spatially organized neuronal network that supports the formation of spatial and episodic memories. We conducted bulk RNA sequencing and spatial transcriptomics experiments to measure gene expression changes in the dorsal hippocampus following the recall of active place avoidance (APA) memory. Through bulk RNA sequencing, we examined the gene expression changes following memory recall across the functionally distinct subregions of the dorsal hippocampus. We found that recall induced differentially expressed genes (DEGs) in the CA1 and CA3 hippocampal subregions were enriched with genes involved in synaptic transmission and synaptic plasticity, while DEGs in the dentate gyrus (DG) were enriched with genes involved in energy balance and ribosomal function. Through spatial transcriptomics, we examined gene expression changes following memory recall across an array of spots encompassing putative memory-associated neuronal ensembles marked by the expression of the IEGs Arc, Egr1, and c-Jun. Within samples from both trained and untrained mice, the subpopulations of spatial transcriptomic spots marked by these IEGs were transcriptomically and spatially distinct from one another. DEGs detected between Arc + and Arc− spots exclusively in the trained mouse were enriched in several memory-related gene ontology terms, including “regulation of synaptic plasticity” and “memory.” Our results suggest that APA memory recall is supported by regionalized transcriptomic profiles separating the CA1 and CA3 from the DG, transcriptionally and spatially distinct IEG expressing spatial transcriptomic spots, and biological processes related to synaptic plasticity as a defining the difference between Arc + and Arc− spatial transcriptomic spots.