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The contribution of excitatory amino acids (AA) to ischemic brain injury has been widely described. In addition, we reported that a mixture of non-excitatory AA at plasmatic concentrations turns irreversible the depression of synaptic transmission caused by hypoxia. Here, we describe that the presence of seven non-excitatory AA (L-alanine, L-glutamine, glycine, L-histidine, L-serine, taurine, and L-threonine) during hypoxia provokes an irreversible neuronal membrane depolarization, after an initial phase of hyperpolarization. The collapse of the membrane potential correlates with a great increase in fiber volley amplitude. Nevertheless, we show that the presence of all seven AA is not necessary to cause the irreversible loss of fEPSP after hypoxia and that the minimal combination of AA able to provoke a solid, replicable effect is the mixture of L-alanine, glycine, L-glutamine, and L-serine. Additionally, L-glutamine seems necessary but insufficient to induce these harmful effects. We also prove that the deleterious effects of the AA mixtures on field potentials during hypoxia depend on both the identity and concentration of the individual AA in the mixture. Furthermore, we find that the accumulation of AA in the whole slice does not determine the outcome caused by the AA mixtures on the synaptic transmission during hypoxia. Finally, results obtained using pharmacological inhibitors and specific substrates of AA transporters suggest that system N and the alanine-serine-cysteine transporter 2 (ASCT2) participate in the non-excitatory AA-mediated deleterious effects during hypoxia. Thus, these AA transporters might represent therapeutical targets for the treatment of brain ischemia. [ABSTRACT FROM AUTHOR]

Background and Purpose: Metabotropic glutamate receptor 1 (mGlu1) is a promising therapeutic target for neurodegenerative CNS disorders including spinocerebellar ataxias (SCAs). Clinical reports have identified naturally‐occurring mGlu1 mutations in rare SCA subtypes and linked symptoms to mGlu1 mutations. However, how mutations alter mGlu1 function remains unknown, as does amenability of receptor function to pharmacological rescue. Here, we explored SCA‐associated mutation effects on mGlu1 cell surface expression, canonical signal transduction and allosteric ligand pharmacology. Experimental Approach: Orthosteric agonists, positive allosteric modulators (PAMs) and negative allosteric modulators (NAMs) were assessed at two functional endpoints (iCa2+ mobilisation and inositol 1‐phosphate [IP1] accumulation) in FlpIn Trex HEK293A cell lines expressing five mutant mGlu1 subtypes. Key pharmacological parameters including ligand potency, affinity and cooperativity were derived using operational models of agonism and allostery. Key Results: mGlu1 mutants exhibited differential impacts on mGlu1 expression, with a C‐terminus truncation significantly reducing surface expression. Mutations differentially influenced orthosteric ligand affinity, efficacy and functional cooperativity between allosteric and orthosteric ligands. Loss‐of‐function mutations L454F and N885del reduced orthosteric affinity and efficacy, respectively. A gain‐of‐function Y792C mutant mGlu1 displayed enhanced constitutive activity in IP1 assays, which manifested as reduced orthosteric agonist activity. The mGlu1 PAMs restored glutamate potency in iCa2+ mobilisation for loss‐of‐function mutations and mGlu1 NAMs displayed enhanced inverse agonist activity at Y792C relative to wild‐type mGlu1. Conclusion and Implications: Collectively, these data highlight distinct mechanisms by which mGlu1 mutations affect receptor function and show allosteric modulators may present a therapeutic strategy to restore aberrant mGlu1 function in rare SCA subtypes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Abnormal activation of Group I mGluRs induces central sensitization. • Blocking Group Ⅰ mGluRs can alleviate neuropathic pain. • The existing Group I mGluRs orthosteric site antagonists have limitations. • Allosteric Modulators exhibit natural advantages due to allosteric modulation. • Structure based drug discovery may promote drug discovery targeting Group I mGluRs. Neuropathic pain (NP) is a widespread public health problem that existing therapeutic treatments cannot manage adequately; therefore, novel treatment strategies are urgently required. G-protein-coupled receptors are important for intracellular signal transduction, and widely participate in physiological and pathological processes, including pain perception. Group I metabotropic glutamate receptors (mGluRs), including mGluR1 and mGluR5, are predominantly implicated in central sensitization, which can lead to hyperalgesia and allodynia. Many orthosteric site antagonists targeting Group I mGluRs have been found to alleviate NP, but their poor efficacy, low selectivity, and numerous side effects limit their development in NP treatment. Here we reviewed the advantages of Group I mGluRs negative allosteric modulators (NAMs) over orthosteric site antagonists based on allosteric modulation mechanism, and the challenges and opportunities of Group I mGluRs NAMs in NP treatment. This article aims to elucidate the advantages and future development potential of Group I mGluRs NAMs in the treatment of NP. [ABSTRACT FROM AUTHOR]

Background: Intermittent Theta Burst Stimulation (iTBS), a non-invasive brain stimulation technique, is recognized for its ability to modulate cortical neuronal activity. However, its effects over time and the dynamics following stimulation are less well understood. Understanding the temporal dynamics of iTBS effects is essential for optimizing the timing and frequency of stimulation in therapeutic applications. Objective: This study investigated the temporal changes in protein expression induced by iTBS in Neuro-2a cells. Methods: We analyzed protein expression in retinoic acid-differentiated Neuro-2a cells at multiple time points — 0.5, 3, 6, 12, and 24 hours post-iTBS — using Western blot and immunocytochemistry techniques. Results: Our findings reveal a significant early increase in neurotransmitter receptor subunits, neurotrophic factors, and cytoskeletal proteins within the first 0.5 hour following iTBS. Notably, proteins such as mGLuR1, NMDAR1, GABBR2, and β-tubulin III showed substantial increase in expression. However, the effects of iTBS on protein expression was not sustained at later timepoints. Conclusion: Our results suggest that iTBS can transiently alter the expression of specific proteins in Neuro-2a cells. Future research should investigate the potential benefits of repeated stimulations within the early time window to refine iTBS interventions, potentially expanding their research and clinical applications. [ABSTRACT FROM AUTHOR]

Neurodegeneration and neuroinflammation are key components in the pathogenesis of Japanese Encephalitis caused by Japanese Encephalitis Virus (JEV) infection. The N-methyl-D-aspartate (NMDA)-type glutamate receptor displays excitatory neurotoxic and pro-inflammatory properties in a cell context-dependent manner. Herein, potential roles of the NMDA receptor in excitatory neurotoxicity and neuroinflammation and effects of NMDA receptor blockade against JEV pathogenesis were investigated in rat microglia, neuron/glia, neuron cultures, and C57BL/6 mice. In microglia, JEV infection induced glutamate release and activated post-receptor NMDA signaling, leading to activation of Ca2+ mobilization and Calcium/Calmodulin-dependent Protein Kinase II (CaMKII), accompanied by pro-inflammatory NF-κB and AP-1 activation and cytokine expression. Additionally, increased Dynamin-Related Protein-1 protein phosphorylation, NAPDH Oxidase-2/4 expression, free radical generation, and Endoplasmic Reticulum stress paralleled with the reactive changes of microglia after JEV infection. JEV infection-induced biochemical and molecular changes contributed to microglia reactivity and pro-inflammatory cytokine expression. NMDA receptor antagonists MK801 and memantine alleviated intracellular signaling and pro-inflammatory cytokine expression in JEV-infected microglia. JEV infection induced neuronal cell death in neuron/glia culture associated with the concurrent production of pro-inflammatory cytokines. Conditioned media of JEV-infected microglia compromised neuron viability in neuron culture. JEV infection-associated neuronal cell death was alleviated by MK801 and memantine. Activation of NMDA receptor-related inflammatory changes, microglia activation, and neurodegeneration as well as reversal effects of memantine were revealed in the brains of JEV-infected mice. The current findings highlight a crucial role of the glutamate/NMDA receptor axis in linking excitotoxicity and neuroinflammation during the course of JEV pathogenesis, and proposes the anti-inflammatory and neuroprotective potential of NMDA receptor blockade. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease that causes muscle atrophy and primarily targets motor neurons (MNs). Approximately 20% of familial ALS cases are caused by gain-of-function mutations in superoxide dismutase 1 (SOD1), leading to MN degeneration and ion channel dysfunction. Previous studies have shown that n-Butylidenephthalide (BP) delays disease progression and prolongs survival in animal models of ALS. However, no studies have been conducted on models from human sources. Herein, we examined the protective efficacy of BP on MNs derived from induced pluripotent stem cells (iPSCs) of an ALS patient harboring the SOD1G85R mutation as well as on those derived from genetically corrected iPSCs (SOD1G85G). Our results demonstrated that the motor neurons differentiated from iPSC with SOD1G85R mutation exhibited characteristics of neuron degeneration (as indicated by the reduction of neurofilament expression) and ion channel dysfunction (in response to potassium chloride (KCl) and L-glutamate stimulation), in contrast to those derived from the gene corrected iPSC (SOD1G85G). Meanwhile, BP treatment effectively restored calcium ion channel function by reducing the expression of glutamate receptors including glutamate ionotropic receptor AMPA type subunit 3 (GluR3) and glutamate ionotropic receptor NMDA type subunit 1 (NMDAR1). Additionally, BP treatment activated autophagic pathway to attenuate neuron degeneration. Overall, this study supports the therapeutic effects of BP on ALS patient-derived neuron cells, and suggests that BP may be a promising candidate for future drug development. [ABSTRACT FROM AUTHOR]

Chemical synapses are the major sites of communication between neurons in the nervous system and mediate either excitatory or inhibitory signaling. At excitatory synapses, glutamate is the primary neurotransmitter and upon release from presynaptic vesicles, is detected by postsynaptic glutamate receptors, which include ionotropic AMPA and NMDA receptors. Here, we have developed methods to identify glutamatergic synapses in brain tissue slices, label AMPA receptors with small gold nanoparticles (AuNPs), and prepare lamella for cryo-electron tomography studies. The targeted imaging of glutamatergic synapses in the lamella is facilitated by fluorescent pre- and postsynaptic signatures, and the subsequent tomograms allow for the identification of key features of chemical synapses, including synaptic vesicles, the synaptic cleft, and AuNP-labeled AMPA receptors. These methods pave the way for imaging brain regions at high resolution, using unstained, unfixed samples preserved under near-native conditions. [ABSTRACT FROM AUTHOR]

The molecular mechanisms underlying the neurodevelopmental disorders (NDDs) caused by DDX3X variants remain poorly understood. In this study, we validated that de novo DDX3X variants are enriched in female developmental delay (DD) patients and mainly affect the evolutionarily conserved amino acids based on a meta-analysis of 46,612 NDD trios. We generated a ddx3x deficient zebrafish allele, which exhibited reduced survival rate, DD, microcephaly, adaptation defects, anxiolytic behaviors, social interaction deficits, and impaired spatial recognitive memory. As revealed by single-nucleus RNA sequencing and biological validations, ddx3x deficiency leads to reduced neural stem cell pool, decreased total neuron number, and imbalanced differentiation of excitatory and inhibitory neurons, which are responsible for the behavioral defects. Indeed, the supplementation of L-glutamate or glutamate receptor agonist ly404039 could partly rescue the adaptation and social deficits. Mechanistically, we reveal that the ddx3x deficiency attenuates the stability of the crebbp mRNA, which in turn causes downregulation of Notch signaling and defects in neurogenesis. Our study sheds light on the molecular pathology underlying the abnormal neurodevelopment and behavior of NDD patients with DDX3X mutations, as well as providing potential therapeutic targets for the precision treatment. [ABSTRACT FROM AUTHOR]

Photoreception is essential for the development of the visual system, shaping vision's first synapse to cortical development. Here, we find that the lighting environment controls developmental rod apoptosis via Opn4-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs). Using genetics, sensory environment manipulations, and computational approaches, we establish a pathway where light-dependent glutamate released from ipRGCs is detected via a transiently expressed glutamate receptor (Grik3) on rod precursors within the inner retina. Communication between these cells is mediated by hybrid neurites on ipRGCs that sense light before eye opening. These structures span the ipRGC-rod precursor distance over development and contain the machinery for photoreception (Opn4) and neurotransmitter release (Vglut2 & Syp). Assessment of the human gestational retina identifies conserved hallmarks of an ipRGC-to-rod axis, including displaced rod precursors, transient GRIK3 expression, and ipRGCs with deep-projecting neurites. This analysis defines an adaptive retrograde pathway linking the sensory environment to rod precursors via ipRGCs prior to eye opening. [Display omitted] • Light controls developing rod apoptosis through interactions with Opn4-expressing RGCs • ipRGCs project hybrid neurites into the developing inner retina, close to rods • Rods transiently express Grik3, allowing for signaling between ipRGCs and rods • Hallmarks of this retinal pathway are conserved between developing mice and humans Photoreception is crucial for the development of the visual system. D'Souza et al. identified a developmental light-dependent pathway that induces rod apoptosis through transient excitatory hybrid neurites on ipRGC photoreceptors, which appears conserved across mouse and human development. [ABSTRACT FROM AUTHOR]

Poplar is one of the fastest-growing temperate trees in the world and is widely used in ornamental horticulture for shade. The root is essential for tree growth and development and its utilization potential is huge. Calcium (Ca), as a signaling molecule, is involved in the regulation of plant root development. However, the detailed underlying regulatory mechanism is elusive. In this study, we analyzed the morphological and transcriptomic variations of 84K poplar (Populus alba x P. glandulosa) in response to different calcium concentrations and found that low Ca2+ (1 mmol • L-1) promoted lateral root development, while deficiency (0.1 mmol • L-1 Ca2+) inhibited lateral root development. Co-expression analysis showed that Ca2+ channel glutamate receptors (GLRs) were present in various modules with significance for root development. Two GLR paralogous genes, PagGLR3.3a and PagGLR3.3b, were mainly expressed in roots and up-regulated under Ca2+ deficiency. The CRISPR/Cas9-mediated signal gene (crispr-PagGLR3.3a, PagGLR3.3b) and double gene (crispr-PagGLR3.3ab) mutants presented more and longer lateral roots. Anatomical analysis showed that crispr-PagGLR3.3ab plants had more xylem cells and promoted the development of secondary vascular tissues. Further transcriptomic analysis suggested that knockout of PagGLR3.3a and PagGLR3.3b led to the up-regulation of several genes related to protein phosphorylation, auxin efflux, lignin and hemicellulose biosynthesis as well as transcriptional regulation, which might contribute to lateral root growth. This study not only provides novel insight into how the Ca2+ channels mediated root growth and development in trees, but also provides a directive breeding of new poplar species for biofuel and bioenergy production. [ABSTRACT FROM AUTHOR]

Early life, or juvenility, stands out as the most pivotal phase in neurodevelopment due to its profound impact over the long‐term cognition. During this period, significant changes are made in the brain's connections both within and between different areas, particularly in tandem with the development of more intricate behaviors. The hippocampus is among the brain regions that undergo significant postnatal remodeling, including dendritic arborization, synaptogenesis, the formation of complex spines and neuron proliferation. Given the crucial role of the hippocampus in spatial memory processing, it has been observed that spatial memory abilities continue to develop as the hippocampus matures, particularly before puberty. The N‐methyl‐d‐aspartate (NMDA) type of glutamate receptor channel is crucial for the induction of activity‐dependent synaptic plasticity and spatial memory formation in both rodents and humans. Although extensive evidence shows the role of NMDA receptors (NMDAr) in spatial memory and synaptic plasticity, the studies addressing the role of NMDAr in spatial memory of juveniles are sparse and mostly limited to adult males. In the present study, we, therefore, aimed to investigate the effects of systemic NMDAr blockade by the MK‐801 on spatial memory (novel object location memory, OLM) and hippocampal plasticity in the form of long‐term potentiation (LTP) of both male and female juvenile rats. Our results show the sex‐dimorphic role of NMDAr in spatial memory and plasticity during juvenility, as systemic NMDAr blockade impairs the OLM and LTP in juvenile males without an effect on juvenile females. Taken together, our results demonstrate that spatial memory and hippocampal plasticity are NMDAr‐dependent in juvenile males and NMDAr‐independent in juvenile females. These sex‐specific differences in the mechanisms of spatial memory and plasticity may imply gender‐specific treatment for spatial memory disorders even in children. [ABSTRACT FROM AUTHOR]

We used virus-mediated anterograde and retrograde tracing, optogenetic modulation, immunostaining, in situ hybridization, and patch-clamp recordings in acute brain slices to study the release mechanism and µ-opioid modulation of the dual glutamatergic/GABAergic inputs from the ventral tegmental area and supramammillary nucleus to the granule cells of the dorsal hippocampus of male and female mice. In keeping with previous reports showing that the two transmitters are released by separate active zones within the same terminals, we found that the short-term plasticity and pharmacological modulation of the glutamatergic and GABAergic currents are indistinguishable. We further found that glutamate and GABA release at these synapses are both virtually completely mediated by N- and P/Q-type calcium channels. We then investigated µ-opioid modulation of these synapses and found that activation of µ-opioid receptors (MORs) strongly inhibits the glutamate and GABA release, mostly through inhibition of presynaptic N-type channels. However, the modulation by MORs of these dual synapses is complex, as it likely includes also a disinhibition due to downmodulation of local GABAergic interneurons which make direct axo-axonic contacts with the dual glutamatergic/GABAergic terminals. We discuss how this opioid modulation may enhance LTP at the perforant path inputs, potentially contributing to reinforce memories of drug-associated contexts. [ABSTRACT FROM AUTHOR]

Amidine-containing compounds are primarily known as antiprotozoal agents (pentamidine, diminazene, furamidine) or as serine protease inhibitors (nafamostat, sepimostat, camostat, gabexate). DAPI is widely recognized as a fluorescent DNA stain. Recently, it has been shown that these compounds also act as NMDA receptor inhibitors. In this study, we examined the activity of these compounds and analyzed the mechanisms of action in relation to another important class of ionotropic glutamate receptors-calcium-permeable AMPA receptors (CP-AMPARs) and calcium-impermeable AMPA receptors (CIAMPARs) - using the whole-cell patch-clamp method on isolated male Wistar rat brain neurons. Gabexate and camostat were found to be inactive. Other compounds preferentially inhibited calcium-permeable AMPA receptors with IC50 values of 30-60 µM. DAPI and furamidine were also active against CIAMPARs with IC50s of 50-60 µM, while others showed poor activity. All active compounds acted as channel blockers, which are able for permeating into the cytoplasm on both CP- and CI-AMPARs. Specifically, sepimostat showed trapping in the closed CP-AMPAR channel. Furamidine and DAPI demonstrated a voltage-independent action on CI-AMPARs, indicating binding to an additional superficial site. While the majority of compounds inhibited glutamate-activated steady-state currents as well as kainate-activated currents on CI-AMPARs, pentamidine significantly potentiated glutamate-induced steadystate responses. The potentiating effect of pentamidine resembles the action of the positive allosteric modulator cyclothiazide although the exact binding site remains unclear. Thus, this study, together with our previous research on NMDA receptors, provides a comprehensive overview of this novel group of ionotropic glutamate receptors inhibitors with a complex pharmacological profile, remarkable diversity of effects and mechanisms of action. [ABSTRACT FROM AUTHOR]

Schizophrenia is a severe psychiatric disorder with high heritability, characterized by positive and negative symptoms as well as cognitive abnormalities. Dysfunction in glutamate synapse is strongly implicated in the pathophysiology of schizophrenia. However, the precise role of the perturbed glutamatergic system in contributing to the cognitive abnormalities of schizophrenia at the synaptic level remains largely unknown. Although our previous work found that Opcml promotes spine maturation and Opcml-deficient mice exhibit schizophrenia-related cognitive impairments, the synaptic mechanism remains unclear. By using whole-cell patch clamp recording, we found that decreased neuronal excitability and alterations in intrinsic membrane properties of CA1 PNs in Opcml-deficient mice. Furthermore, Opcml deficiency leads to impaired glutamatergic transmission in hippocampus, which is closely related to postsynaptic AMPA/NMDA receptors dysfunction, resulting in the disturbances of E/I balance. Additionally, we found that the aripiprazole which we used to ameliorate abnormal cognitive behaviors also rescued the impaired glutamatergic transmission in Opcml-deficient mice. These findings will help to understand the synaptic mechanism in schizophrenia pathogenesis, providing insights into schizophrenia therapeutics with glutamatergic disruption. [ABSTRACT FROM AUTHOR]

While many mRNAs contain more than one translation initiation site (TIS), the functions of most alternative TISs and their corresponding protein isoforms (proteoforms) remain undetermined. Here, we showed that alternative usage of CUG and AUG TISs in neuronal pentraxin receptor (NPR) mRNA produced two proteoforms, of which the ratio was regulated by RNA secondary structure and neuronal activity. Downstream AUG initiation truncated the N-terminal transmembrane domain and produced a secreted NPR proteoform sufficient in promoting synaptic clustering of AMPA-type glutamate receptors. Mutations that altered the ratio of NPR proteoforms reduced AMPA receptors in parvalbumin-positive interneurons and affected learning behaviors in mice. In addition to NPR, upstream AUU-initiated N-terminal extension of C1q-like synaptic organizers anchored these otherwise secreted factors to the membrane. Together, these results uncovered the plasticity of N-terminal signal sequences regulated by alternative TIS usage as a potentially widespread mechanism in diversifying protein localization and functions. [Display omitted] • NPR mRNA contains a CUG and an AUG TIS, each producing a distinct proteoform • Alternative TIS usage in NPR is regulated by RNA structures and neuronal activity • AUG initiation shortens the signal sequence and converts NPR to a secreted factor • Altering NPR proteoform ratio impacts AMPA receptors in PV+ neurons and behaviors Unlike most mRNAs that encode one protein, Lee et al. discover that several neuronal synaptic organizer mRNAs encode more than one protein product (proteoform) by using multiple translation initiation sites. Alternative translation initiation remodels the N-terminal signal sequence, diversifies proteoform localization and functions, and impacts animal behaviors. [ABSTRACT FROM AUTHOR]

The mechanisms of anxiety disorders, the most common mental illness, remain incompletely characterized. The ventral hippocampus (vHPC) is critical for the expression of anxiety. However, current studies primarily focus on vHPC neurons, leaving the role for vHPC astrocytes in anxiety largely unexplored. Here, genetically encoded Ca2+ indicator GCaMP6m and in vivo fiber photometry calcium imaging are used to label vHPC astrocytes and monitor their activity, respectively, genetic and chemogenetic approaches to inhibit and activate vHPC astrocytes, respectively, patch‐clamp recordings to measure glutamate currents, and behavioral assays to assess anxiety‐like behaviors. It is found that vHPC astrocytic activity is increased in anxiogenic environments and by 3‐d subacute restraint stress (SRS), a well‐validated mouse model of anxiety disorders. Genetic inhibition of vHPC astrocytes exerts anxiolytic effects on both innate and SRS‐induced anxiety‐related behaviors, whereas hM3Dq‐mediated chemogenetic or SRS‐induced activation of vHPC astrocytes enhances anxiety‐like behaviors, which are reversed by intra‐vHPC application of the ionotropic glutamate N‐methyl‐d‐aspartate receptor antagonists. Furthermore, intra‐vHPC or systemic application of the N‐methyl‐d‐aspartate receptor antagonist memantine, a U.S. FDA‐approved drug for Alzheimer's disease, fully rescues SRS‐induced anxiety‐like behaviors. The findings highlight vHPC astrocytes as critical regulators of stress and anxiety and as potential therapeutic targets for anxiety and anxiety‐related disorders. [ABSTRACT FROM AUTHOR]

Different populations of hypothalamic kisspeptin (KISS1) neurons located in the rostral periventricular area of the third ventricle (RP3V) and arcuate nucleus (ARC) are thought to generate the sex‐specific patterns of gonadotropin secretion. These neuronal populations integrate gonadal sex steroid feedback with internal and external cues relayed via the actions of neurotransmitters and neuropeptides. The excitatory amino acid neurotransmitter glutamate, the main excitatory neurotransmitter in the brain, plays a role in regulating gonadotropin secretion, at least partially through engaging KISS1 signaling. The expression and function of individual glutamate receptor subtypes in KISS1 neurons, however, are not well characterized. Here, we used GCaMP‐based calcium imaging and patch‐clamp electrophysiology to assess the impact of activating individual ionotropic (iGluR) and group I metabotropic (mGluR) glutamate receptors on KISS1 neuron activity in the mouse RP3V and ARC. Our results indicate that activation of all iGluR subtypes and of group I mGluRs, likely mGluR1, consistently drives activity in the majority of KISS1 neurons within the RP3V and ARC of males and females. Our results also revealed, somewhat unexpectedly, sex‐ and region‐specific differences. Indeed, activating (S)‐α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) type iGluRs evoked larger responses in female ARCKISS1 neurons than in their male counterparts whereas activating group I mGluRs induced larger responses in RP3VKISS1 neurons than in ARCKISS1 neurons in females. Together, our findings suggest that glutamatergic neurotransmission in KISS1 neurons, and its impact on the activity of these cells, might be sex‐ and region‐dependent in mice. [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]

N-methyl-D-aspartate (NMDA) receptors are ionotropic glutamate receptors involved in learning and memory. NMDA receptors primarily comprise two GluN1 and two GluN2 subunits. The GluN2 subunit dictates biophysical receptor properties, including the extent of receptor activation and desensitization. GluN2A- and GluN2D-containing receptors represent two functional extremes. To uncover the conformational basis of their functional divergence, we utilize single-molecule fluorescence resonance energy transfer to probe the extracellular domains of these receptor subtypes under resting and ligand-bound conditions. We find that the conformational profile of the GluN2 amino-terminal domain correlates with the disparate functions of GluN2A- and GluN2D-containing receptors. Changes at the pre-transmembrane segments inversely correlate with those observed at the amino-terminal domain, confirming direct allosteric communication between these domains. Additionally, binding of a positive allosteric modulator at the transmembrane domain shifts the conformational profile of the amino-terminal domain towards the active state, revealing a bidirectional allosteric pathway between extracellular and transmembrane domains. NMDA receptors convert chemical signals into electrical signals in the brain, and function is fine-tuned by the subunit composition. Here the authors use smFRET to uncover a bi-directional communication pathway between different parts of the receptor. [ABSTRACT FROM AUTHOR]

α‐Amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) ionotropic glutamate receptors (AMPARs) mediate rapid excitatory synaptic transmission in the mammalian brain, primarily driven by the neurotransmitter glutamate. The modulation of AMPAR activity, particularly calcium‐permeable AMPARs (CP‐AMPARs), is crucially influenced by various auxiliary subunits. These subunits are integral membrane proteins that bind to the receptor's core and modify its functional properties, including ion channel kinetics and receptor trafficking. This review comprehensively catalogs all known AMPAR auxiliary proteins, providing vital insights into the biochemical mechanisms governing synaptic modulation and the specific impact of CP‐AMPARs compared to their calcium‐impermeable AMPA receptor (CI‐AMPARs). Understanding the complex interplay between AMPARs and their auxiliary subunits in different brain regions is essential for elucidating their roles in cognitive functions such as learning and memory. Importantly, alterations in these auxiliary proteins' expression, function or interactions have been implicated in various neurological disorders. Aberrant signaling through CP‐AMPARs, in particular, is associated with severe synaptic dysfunctions across neurodevelopmental, neurodegenerative and psychiatric conditions. Targeting the distinct properties of AMPAR‐auxiliary subunit complexes, especially those involving CP‐AMPARs, could disclose new therapeutic strategies, potentially allowing for more precise interventions in treating complex neuronal disorders. [ABSTRACT FROM AUTHOR]

Activity-dependent modulations of N-methyl-D-aspartate glutamate receptor (NMDAR) trapping at synapses regulate excitatory neurotransmission and shape cognitive functions. Although NMDAR synaptic destabilization has been associated with severe neurological and psychiatric conditions, tuning NMDAR synaptic trapping to assess its clinical relevance for the treatment of brain conditions remains a challenge. Here, we report that ketamine (KET) and other clinically relevant NMDAR open channel blockers (OCBs) promote interactions between NMDAR and PDZ-domain-containing scaffolding proteins and enhance NMDAR trapping at synapses. We further show that KET-elicited trapping enhancement compensates for depletion in synaptic receptors triggered by autoantibodies from patients with anti-NMDAR encephalitis. Preventing synaptic depletion mitigates impairments in NMDAR-mediated CaMKII signaling and alleviates anxiety- and sensorimotor-gating-related behavioral deficits provoked by autoantibodies. Altogether, these findings reveal an unexpected dimension of OCB action and stress the potential of targeting receptor anchoring in NMDAR-related synaptopathies. [Display omitted] • Open channel blockers (OCBs) such as ketamine promote NMDAR synaptic trapping • OCB binding enhances interactions between NMDARs and scaffolding proteins • Ketamine prevents NMDAR depletion at synapses exposed to anti-NMDAR autoantibodies • Ketamine alleviates behavioral deficits provoked by anti-NMDAR autoantibodies Villéga, Fernandes, Jézéquel et al. report that NMDAR open channel blockers, such as ketamine, favor receptor trapping at excitatory synapses through enhanced interactions with scaffolding proteins. They further show that ketamine-elicited trapping enhancement alleviates NMDAR synaptic impairments and behavioral deficits caused by autoantibodies from patients with anti-NMDAR encephalitis. [ABSTRACT FROM AUTHOR]

Responding to burst stimulation of parallel fibers (PFs), cerebellar Purkinje neurons (PNs) generate a convolved synaptic response displaying a fast excitatory postsynaptic current (EPSCFast) followed by a slow EPSC (EPSCSlow). The latter is companied with a rise of intracellular Ca2+ and critical for motor coordination. The genesis of EPSCSlow in PNs results from activation of metabotropic type 1 glutamate receptor (mGluR1), oligomerization of stromal interaction molecule 1 (STIM1) on the membrane of endoplasmic reticulum (ER) and opening of transient receptor potential canonical 3 (TRPC3) channels on the plasma membrane. Neuronal nitric oxide synthase (nNOS) is abundantly expressed in PFs and granule neurons (GNs), catalyzing the production of nitric oxide (NO) hence regulating PF-PN synaptic function. We recently found that nNOS/NO regulates the morphological development of PNs through mGluR1-regulated Ca2+-dependent mechanism. This study investigated the role of nNOS/NO in regulating EPSCSlow. Electrophysiological analyses showed that EPSCSlow in cerebellar slices of nNOS knockout (nNOS−/−) mice was significantly larger than that in wildtype (WT) mice. Activation of mGluR1 in cultured PNs from nNOS−/− mice evoked larger TRPC3-channel mediated currents and intracellular Ca2+ rise than that in PNs from WT mice. In addition, nNOS inhibitor and NO-donor increased and decreased, respectively, the TRPC3-current and Ca2+ rise in PNs. Moreover, the NO-donor effectively decreased TRPC3 currents in HEK293 cells expressing WT STIM1, but not cells expressing a STIM1 with cysteine mutants. These novel findings indicate that nNOS/NO inhibits TRPC3-containig channel mediated cation influx during EPSCSlow, at least in part, by S-nitrosylation of STIM1. [ABSTRACT FROM AUTHOR]

Autosomal recessive spinocerebellar ataxia 13 (SCAR13) is a neurological disease characterized by psychomotor delay, mild to profound intellectual disability with poor or absent language, nystagmus, stance ataxia, and, if walking is acquired, gait ataxia. Epilepsy and polyneuropathy have also been documented in some patients. Cerebellar atrophy and/or ventriculomegaly may be present on brain MRI. SCAR13 is caused by pathogenic variants in the GRM1 gene encoding the metabotropic receptor of glutamate type 1 (mGlur1), which is highly expressed in Purkinje cerebellar cells, where it plays a fundamental role in cerebellar development. Here we discuss the case of an 8-year-old patient who presented with a severe neurodevelopmental disorder with balance disturbance, absence of independent walking, absence of language, diffuse hypotonia, mild nystagmus, and mild dysphagia. Whole-exome sequencing revealed a compound heterozygosity for two likely pathogenic variants in the GRM1 gene, responsible for the patient's phenotype, and made it possible to diagnose autosomal recessive spinocerebellar ataxia SCAR13. The detected (novel) variants appear to be causative of a particularly severe picture with regard to neurodevelopment, in the context of the typical neurological signs of spinocerebellar ataxia. [ABSTRACT FROM AUTHOR]

Vimentin intermediate filaments are dynamic structures that are able to move in cytoplasm owing to activity of the motor proteins, kinesin-1 and cytoplasmic dynein. How exactly motors interact with vimentin filaments remains unclear. In this work, I show that GRIP1 (Glutamate Receptor Interacting Protein 1), known as adapter for kinesin-1 on many cargoes in neurons, might also mediate kinesin-1 interaction with vimentin filaments. GRIP1 associates with vimentin filaments in various cells and co-immunoprecipitates with vimentin from cell lysates. Human endothelial cells knockout by GRIP1 gene lose focal adhesions and change their adhesive properties. Hypothetically, kinesin-1 engages GRIP1 to deliver vimentin filaments to the cell periphery so that they make contact with focal adhesions and stabilize them. [ABSTRACT FROM AUTHOR]

Ionotropic glutamate receptors (iGluRs), specifically α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid receptors (AMPARs), play a crucial role in orchestrating excitatory neurotransmission in the brain. AMPARs are intricate assemblies of subunits encoded by four paralogous genes: GRIA1‐4. Functional studies have established that rare GRIA variants can alter AMPAR currents leading to a loss‐ or gain‐of‐function. Patients affected by rare heterozygous GRIA variants tend to have family specific variants and only few recurrent variants have been reported. We deep‐phenotyped a cohort comprising eight unrelated children and adults, harboring a recurrent and well‐established disease‐causing GRIA1 variant (NM_001114183.1: c.1906G>A, p.(Ala636Thr)). Recurrent symptoms included motor and/or language delay, mild–severe intellectual disability, behavioral and psychiatric comorbidities, hypotonia and epilepsy. We also report challenges in social skills, autonomy, living and work situation, and occupational levels. Furthermore, we compared their clinical manifestations in relation to those documented in patients presenting with rare heterozygous variants at analogous positions within paralogous genes. This study provides unprecedented details on the neurodevelopmental outcomes, cognitive abilities, seizure profiles, and behavioral abnormalities associated with p.(Ala636Thr) refining and broadening the clinical phenotype. [ABSTRACT FROM AUTHOR]

Background Metabotropic glutamate receptor 5 (mGlu5) dysregulation has been implicated in the pathophysiology of trauma-related psychopathology, and there are direct interactions between the endocannabinoid and glutamatergic systems. However, relationships between cannabis use (CU) and mGlu5 have not been directly investigated in trauma-related psychopathology. Methods Using positron emission tomography with [18F]FPEB, we examined relationships between CU status and mGlu5 availability in vivo in a cross-diagnostic sample of individuals with trauma-related psychopathology (n = 55). Specifically, we tested whether mGlu5 availability in frontolimbic regions of interest (ROIs; dorsolateral prefrontal cortex, orbitofrontal cortex, ventromedial prefrontal cortex, amygdala, hippocampus) differed as a function of CU status. Results Past-year CU (n = 22) was associated with 18.62%–19.12% higher mGlu5 availability in frontal and 14.24%–16.55% higher mGlu5 in limbic ROIs relative to participants with no recent CU. Similarly, past-month or monthly CU (n  =  16) was associated with higher mGlu5 availability in frontal (18.05%–20.62%) and limbic (15.53%–16.83%) ROIs. mGlu5 availability in the orbitofrontal cortex and amygdala was negatively associated with depressive symptoms in the past-year CU group. In both CU groups, exploratory analyses showed negative correlations between mGlu5 availability and sadness across all ROIs and with perceptions of worthlessness and past failures (r 's = −.47 to.66, P 's = .006–.033) in the ventromedial prefrontal cortex. Participants with CU reported lower mean depressive symptoms (P 's = .006–.037) relative to those without CU. Conclusions These findings have substantial implications for our understanding of interactions between CU and glutamatergic neurotransmission in trauma-related psychopathology, underscoring the need for treatment development efforts to consider the effects of CU in this population. [ABSTRACT FROM AUTHOR]

Glyphosate (GLY) is a pesticide that severely alters nigrostriatal dopaminergic neurotransmission, inducing great increases in dopamine release from rat dorsal striatum. This GLY‐induced striatal dopamine overflow occurs through mechanisms not yet fully understood, hence the interest in evaluating the role of other neurotransmitter systems in such effects. So, the main objective of this mechanistic study was to evaluate the possible mediation of the glutamatergic, cholinergic, and nitrergic systems in the GLY‐induced in vivo dopamine release from rat dorsal striatum. The extracellular dopamine levels were measured by cerebral microdialysis and HPLC with electrochemical detection. Intrastriatal administration of GLY (5 mmol/L) significantly increased the dopamine release (1102%). Pretreatment with MK‐801 (50 or 400 μmol/L), a non‐competitive antagonist of NMDA receptors, significantly decreased the effect of GLY (by 70% and 74%, respectively), whereas AP‐5 (400 μmol/L), a competitive antagonist of NMDA receptors, or CNQX (500 μmol/L), an AMPA/kainate receptor antagonist, had no significant effect. Administration of the nitric oxide synthase inhibitors, L‐nitroarginine (L‐NAME, 100 μmol/L) or 7‐nitroindazole (7‐NI, 100 μmol/L), also did not alter the effect of GLY on dopamine release. Finally, pretreatment of the animals with mecamylamine, an antagonist of nicotinic receptors, decreased the effect of GLY on dopamine release by 49%, whereas atropine, a muscarinic antagonist, had no significant effect. These results indicate that GLY‐induced dopamine release largely depends on the activation of NMDA and nicotinic receptors in rat dorsal striatum. Future research is needed to determine the effects of this pesticide at environmentally relevant concentrations. Glyphosate (GLY) is a pesticide that severely alters nigrostriatal dopaminergic neurotransmission, inducing large increases in striatal dopamine release. In the present study, we confirmed that the intrastriatal administration of GLY increased the in vivo release of dopamine and that local administration of specific antagonists of NMDA and nicotinic receptors significantly decreased the effect of the pesticide. However, this inhibition was only partial, indicating that GLY is a pesticide that alters dopaminergic neurotransmission through several mechanisms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Inflammatory arthritis can cause peripheral nerve sensitization. • GBP can intervene in peripheral nerve sensitization caused by inflammatory arthritis. • NR2B may be the cause of peripheral sensitization in inflammatory arthritis. • GBP may alleviate pain through the downregulation of NR2B. • This study provides a theoretical basis for the inflammatory arthritis. Inflammatory arthritis leads to peripheral nerve sensitization, but the therapeutic effect is often unsatisfactory. Our preliminary studies have found that in mice with inflammatory arthritis, the use of ionotropic glutamate receptor antagonists can produce a good analgesic effect without altering foot swelling, suggesting that pain relief may be related to the improvement of neuropathic pain. However, the underlying mechanisms remain unclear. To further investigate the effects of neuropathic pain medications on inflammatory arthritis and the impact of the ionotropic glutamate receptor NR2B subunit (NR2B) on inflammatory arthritis, this study employed gabapentin (GBP) treatment on the inflammatory arthritis mouse model (the adjuvant induced arthritis, AIA), and we found a significant reduction in pain. Further studies revealed that in AIA, the expression levels of NR2B, TRPV1, pain-related molecules (substance P, PGE 2), inflammatory cytokines (IL-1, IL-6, TNF-α, and GM-CSF) and Ca2+ were elevated in the foot and dorsal root ganglia (DRG). GBP treatment was able to influence the downregulation of the expression levels of NR2B, TRPV1, pain-related molecules, inflammatory cytokines and Ca2+. Mechanistic studies have shown that GBP treatment affects the downregulation of NR2B, and the downregulation of NR2B expression leads to the downregulation of TRPV1, pain-related molecules and inflammatory cytokines, thereby alleviating pain. These results suggest that in peripheral sensitization caused by AIA, GBP can play a role in improving pain, and NR2B may be a key target of peripheral nerve sensitization induced by inflammatory arthritis. GBP provides a theoretical basis for the clinical treatment of inflammatory arthritis. [ABSTRACT FROM AUTHOR]

AMPA‐type glutamate receptors (AMPARs) mediate the majority of fast excitatory synaptic transmission in the mammalian brain. Ampakines, positive allosteric modulators of AMPAR, hold significant potential for the treatment of a wide range of neurological/neuropsychiatric disorders in which excitatory synaptic transmission is compromised. Low‐impact ampakines are a distinct subset of ampakines that accelerate channel opening yet minimally affect receptor desensitization, which may explain their lack of seizurogenic effects at therapeutic doses in preclinical models. CX1739 is a low‐impact ampakine that has shown efficacy in preclinical studies. The current clinical study examined the tolerability and pharmacokinetics of CX1739 in healthy male volunteers in a 2‐part study. Part A was a single dose escalation study (100‐1200 mg, 48 patients) and Part B was a multiple dose ascending study (300‐600 mg BID for 7‐10 days, 32 patients). CX1739 was well tolerated up to 900 mg once daily (QD) and 450 mg twice a day, with the prominent side effects being headache and nausea. Importantly, the half‐life of CX1739 was 6‐9 hours, and Tmax was 1‐5 hours. CX1739 Cmax and AUC were dose‐proportional. These findings thus set the stage for further explorations of this drug candidate in phase 2 clinical studies. [ABSTRACT FROM AUTHOR]

Afferent synapses between inner hair cells (IHCs) and the type I spiral ganglion neurons (SGNs) in the cochlea provide over 95% of sensory signals for auditory perception in the brain. However, these afferent synapses are particularly vulnerable to damage, for example from excitotoxicity, and exposure to noise in the environment which often leads to noise‐induced cochlear synaptopathy (NICS). In this study, we simulated excitotoxic trauma by incubating kainic acid, a non‐desensitizing agonist for AMPA type glutamate receptors on cultured cochleae. The possible protective effects of amitriptyline against NICS were examined. We found that, in IHCs, amitriptyline reversed the decrease of Ca2+ current and exocytosis caused by excitotoxic trauma. In SGNs, amitriptyline promoted the recovery of neurite loss caused by excitotoxic trauma. Furthermore, we found that the protective effects of amitriptyline are likely mediated by suppressing apoptosis factors that were upregulated during excitotoxic trauma. In conclusion, our results suggest that amitriptyline could protect afferent synapses in the cochlea from NICS, making it a potential drug candidate for hearing protection. [ABSTRACT FROM AUTHOR]

N-methyl-D-aspartate receptors (NMDARs) are glutamate receptors with key roles in synaptic communication and plasticity. The activation of synaptic NMDARs initiates plasticity and stimulates cell survival. In contrast, the activation of extrasynaptic NMDARs can promote cell death underlying a potential mechanism of neurodegeneration occurring in Alzheimer's disease (AD). The distribution of synaptic versus extrasynaptic NMDARs has emerged as an important parameter contributing to neuronal dysfunction in neurodegenerative diseases including AD. Here, we review the concept of extrasynaptic NMDARs, as this population is present in numerous neuronal cell membranes but also in the membranes of various non-neuronal cells. Previous evidence regarding the membranal distribution of synaptic versus extrasynaptic NMDRs in relation to AD mice models and in the brains of AD patients will also be reviewed. [ABSTRACT FROM AUTHOR]

Metabotropic glutamate receptor 4 (mGluR4) is widely regarded as an umami receptor activated by L-glutamate to exert essential functions. Numerous studies have shown that umami receptors participate in food intake regulation. However, little is known about mGluR4's role in mediating food ingestion and its possible molecular mechanism. Mandarin fish, a typical carnivorous fish, is sensitive to umami substances and is a promising vertebrate model organism for studying the umami receptor. In this study, we identified the mGluR4 gene and conducted evolutionary analyses from diverse fish species with different feeding habits. mGluR4 of mandarin fish was cloned and functionally expressed to investigate the effects of L-glutamate on mGluR4. We further explored whether the signal pathway mGluR4-Ca2+-ERK1/2 participates in the process in mandarin fish brain cells. The results suggest that L-glutamate could regulate Neuropeptide Y (Npy) via the mGluR4-Ca2+-ERK1/2 signaling pathway in mandarin fish. Our findings unveil the role of mGluR4 in feeding decisions and its possible molecular mechanisms in carnivorous fishes. [ABSTRACT FROM AUTHOR]

Elucidating biological mechanisms contributing to bipolar disorder (BD) is key to improved diagnosis and treatment development. With converging evidence implicating the metabotropic glutamate receptor 5 (mGlu5) in the pathology of BD, here, we therefore test the hypothesis that recently identified deficits in mGlu5 are associated with functional brain differences during emotion processing in BD. Positron emission tomography (PET) with [18F]FPEB was used to measure mGlu5 receptor availability and functional imaging (fMRI) was performed while participants completed an emotion processing task. Data were analyzed from 62 individuals (33 ± 12 years, 45 % female) who completed both PET and fMRI, including individuals with BD (n = 18), major depressive disorder (MDD: n = 20), and psychiatrically healthy comparisons (HC: n = 25). Consistent with some prior reports, the BD group displayed greater activation during fear processing relative to MDD and HC, notably in right lateralized frontal and parietal brain regions. In BD, (but not MDD or HC) lower prefrontal mGlu5 availability was associated with greater activation in bilateral pre/postcentral gyri and cuneus during fear processing. Furthermore, greater prefrontal mGlu5-related brain activity in BD was associated with difficulties in psychomotor function (r ≥ 0.904, p ≤ 0.005) and attention (r ≥ 0.809, p ≤ 0.028). The modest sample size is the primary limitation. Deficits in prefrontal mGlu5 in BD were linked to increased cortical activation during fear processing, which in turn was associated with impulsivity and attentional difficulties. These data further implicate an mGlu5-related mechanism unique to BD. More generally these data suggest integrating PET and fMRI can provide novel mechanistic insights. • Functional (fMRI) and molecular (PET) imaging performed in the same individuals with bipolar disorder (BD) and major depressive disorder (MDD). • Findings provide evidence of relationships between prefrontal mGlu5 and brain function during emotional processing that is unique to BD. • We propose a mechanism by which deficient prefrontal mGlu5 in BD contributes to alterations in clinically relevant brain function. • Understanding the role of mGlu5 in BD pathology could aid in the development of targeted, mechanistically informed treatments. [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]

The cerebellum plays an important role in diverse brain functions, ranging from motor learning to cognition. Recent studies have suggested that molecular and cellular heterogeneity within cerebellar lobules contributes to functional differences across the cerebellum. However, the specific relationship between molecular and cellular heterogeneity and diverse functional outputs of different regions of the cerebellum remains unclear. Here, we describe a previously unappreciated form of synaptic heterogeneity at parallel fiber synapses to Purkinje cells in the mouse cerebellum (both sexes). In contrast to uniform fast synaptic transmission, we found that the properties of slow synaptic transmission varied by up to threefold across different lobules of the mouse cerebellum, resulting in surprising heterogeneity. Depending on the location of a Purkinje cell, the time of peak of slow synaptic currents varied by hundreds of milliseconds. The duration and decay time of these currents also spanned hundreds of milliseconds, based on lobule. We found that, as a consequence of the heterogeneous synaptic dynamics, the same brief input stimulus was transformed into prolonged firing patterns over a range of timescales that depended on Purkinje cell location. [ABSTRACT FROM AUTHOR]

[Display omitted] • mGluR5 PAM pre-treatment prevents MK-801 induced increased extracellular glutamate. • mGluR5 PAM does not affect mPFC extracellular glutamate when given alone. • mGluR5 PAM may restore cognitive function by regulating mPFC glutamate. • Targeting mGluR5 with PAMs may treat neuropsychiatric disorder impairments. Potentiation of metabotropic glutamate receptor subtype 5 (mGluR5) function produces antipsychotic-like and pro-cognitive effects in animal models of schizophrenia and can reverse cognitive deficits induced by N-methyl-D-aspartate type glutamate receptor (NMDAR) antagonists. However, it is currently unknown if mGluR5 positive allosteric modulators (PAMs) can modulate NMDAR antagonist-induced alterations in extracellular glutamate levels in regions underlying these cognitive and behavioral effects, such as the medial prefrontal cortex (mPFC). We therefore assessed the ability of the mGluR5 PAM, 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl) benzamide (CDPPB), to reduce elevated extracellular glutamate levels induced by the NMDAR antagonist, dizocilpine (MK-801), in the mPFC. Male Sprague-Dawley rats were implanted with a guide cannula aimed at the mPFC and treated for ten consecutive days with MK-801 and CDPPB or their corresponding vehicles. CDPPB or vehicle was administered thirty minutes before MK-801 or vehicle each day. On the final day of treatment, in vivo microdialysis was performed, and samples were collected every thirty minutes to analyze extracellular glutamate levels. Compared to animals receiving only vehicle, administration of MK-801 alone significantly increased extracellular levels of glutamate in the mPFC. This effect was not observed in animals administered CDPPB before MK-801, nor in those administered CDPPB alone, indicating that CDPPB decreased extracellular glutamate release stimulated by MK-801. Results indicate that CDPPB attenuates MK-801 induced elevations in extracellular glutamate in the mPFC. This effect of CDPPB may underlie neurochemical adaptations associated with the pro-cognitive effects of mGluR5 PAMs in rodent models of schizophrenia. [ABSTRACT FROM AUTHOR]

Depression is a disabling and highly prevalent psychiatric illness. Multiple studies have linked glutamatergic dysfunction with the pathophysiology of depression, but the exact alterations in the glutamatergic system that contribute to depressive‐like behaviors are not fully understood. Recent evidence suggests that a decreased level in neuronal glutamate transporter (EAAT3), known to control glutamate levels and limit the activation of glutamate receptors at synaptic sites, may contribute to the manifestation of a depressive phenotype. Here, we tested the possibility that increased EAAT3 expression at excitatory synapses could reduce the susceptibility of mice to develop depressive‐like behaviors when challenged to a 5‐week unpredictable chronic mild stress (UCMS) protocol. Mice overexpressing EAAT3 in the forebrain (EAAT3glo/CMKII) and control littermates (EAAT3glo) were assessed for depressive‐like behaviors and long‐term memory performance after being subjected to UCMS conditions. We found that, after UCMS, EAAT3glo/CMKII mice did not exhibit depressive‐like behaviors or memory alterations observed in control mice. Moreover, we found that EAAT3glo/CMKII mice did not show alterations in phasic dopamine release in the nucleus accumbens neither in long‐term synaptic plasticity in the CA1 region of the hippocampus after UCMS, as observed in control littermates. Altogether these results suggest that forebrain EAAT3 overexpression may be related to a resilient phenotype, both at behavioral and functional level, to the deleterious effect of chronic stress, highlighting the importance of neuronal EAAT3 in the pathophysiology of depressive‐like behaviors. [ABSTRACT FROM AUTHOR]

Melanoma is the most aggressive type of skin cancer and is responsible for the majority of deaths from skin cancer. Therapeutic advances in the last few decades, notably the development of novel targeted therapies and immunotherapies have significantly improved patient outcomes; nonetheless, these options remain limited due to the onset of resistance to treatment modalities and relapse. In this review, we focus on the available therapeutic options, their benefits, and limitations. [ABSTRACT FROM AUTHOR]

Myocardial ischemia causes the release of bradykinin, which activates afferent nerve endings in the ventricular epicardium. This elicits a sympathetically mediated increase in arterial pressure and heart rate, referred to as the cardiogenic sympathetic afferent reflex. The rostroventrolateral medulla (RVLM) is a key sympathetic brain stem site for regulating cardiovascular activity. This study aimed to determine the importance of non‐barosensitive nociception sympathetic activity and the role of glutamate receptor activation of RVLM neurons in the cardiogenic sympathetic afferent reflex. We tested the hypothesis that inhibition of barosensitive sympathetic activity attenuates but does not abolish the reflex response to cardiac visceral afferents. Renal sympathetic nerve activity (RSNA), arterial pressure, and heart rate responses to epicardial bradykinin application were recorded in anesthetized rats before and after bilateral RVLM microinjection of either GABAA agonist muscimol, ionotropic glutamate receptor antagonist kynurenic acid, N‐methyl‐d‐aspartate (NMDA) receptor antagonist 2‐amino‐5‐ phosphonopentanoic acid (AP5), or non‐NMDA antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX). Baroreceptor loading‐induced inhibition of barosensitive activity attenuated the bradykinin‐induced RSNA response (93 ± 14% increase) and tachycardia (18 ± 3 bpm). While RVLM muscimol microinjection abolished the RSNA response (1.6 ± 4.2% from baseline, 0.49 ± 0.38 μV*s), surprisingly, it did not abolish the tachycardia (27 ± 4 bpm). Kynurenic acid microinjection blocked the arterial pressure and RSNA responses, while AP5 or CNQX only attenuated the responses. These data suggest that nociception‐sensitive sympathetic activity that does not appear to be barosensitive is also involved in the cardiogenic sympathetic afferent reflex. Importantly, while muscimol and kynurenic acid abolished the arterial pressure and RSNA response, neither affected the tachycardia, suggesting an alternate cardiac pathway independent of RVLM. [ABSTRACT FROM AUTHOR]

Group I metabotropic glutamate receptors (mGluRs) modulate postsynaptic neuronal excitability and epileptogenesis. We investigated roles of group I mGluRs on low extracellular Mg2+ concentration ([Mg2+]o)-induced epileptiform activity and neuronal cell death in the CA1 regions of isolated rat hippocampal slices without the entorhinal cortex using extracellular recording and propidium iodide staining. Exposure to Mg2+-free artificial cerebrospinal fluid can induce interictal epileptiform activity in the CA1 regions of rat hippocampal slices. MPEP, a mGluR 5 antagonist, significantly inhibited the spike firing of the low [Mg2+]o-induced epileptiform activity, whereas LY367385, a mGluR1 antagonist, did not. DHPG, a group 1 mGluR agonist, significantly increased the spike firing of the epileptiform activity. U73122, a PLC inhibitor, inhibited the spike firing. Thapsigargin, an ER Ca2+-ATPase antagonist, significantly inhibited the spike firing and amplitude of the epileptiform activity. Both the IP3 receptor antagonist 2-APB and the ryanodine receptor antagonist dantrolene significantly inhibited the spike firing. The PKC inhibitors such as chelerythrine and GF109203X, significantly increased the spike firing. Flufenamic acid, a relatively specific TRPC 1, 4, 5 channel antagonist, significantly inhibited the spike firing, whereas SKF96365, a relatively non-specific TRPC channel antagonist, did not. MPEP significantly decreased low [Mg2+]o DMEM-induced neuronal cell death in the CA1 regions, but LY367385 did not. We suggest that mGluR 5 is involved in low [Mg2+]oinduced interictal epileptiform activity in the CA1 regions of rat hippocampal slices through PLC, release of Ca2+ from intracellular stores and PKC and TRPC channels, which could be involved in neuronal cell death. [ABSTRACT FROM AUTHOR]

Acute organophosphorus compound (OP) poisoning induces symptoms of the cholinergic crises with the occurrence of severe epileptic seizures. Seizures are induced by hyperstimulation of the cholinergic system, but are enhanced by hyperactivation of the glutamatergic system. Overstimulation of muscarinic cholinergic receptors by the elevated acetylcholine causes glutamatergic hyperexcitation and an increased influx of Ca2+ into neurons through a type of ionotropic glutamate receptors, N‐methyl‐d‐aspartate (NMDA) receptors (NMDAR). These excitotoxic signaling processes generate reactive oxygen species, oxidative stress, and activation of the neuroinflammatory response, which can lead to recurrent epileptic seizures, neuronal cell death, and long‐term neurological damage. In this review, we illustrate the NMDAR structure, complexity of subunit composition, and the various receptor properties that change accordingly. Although NMDARs are in normal physiological conditions important for controlling synaptic plasticity and mediating learning and memory functions, we elaborate the detrimental role NMDARs play in neurotoxicity of OPs and focus on the central role NMDAR inhibition plays in suppressing neurotoxicity and modulating the inflammatory response. The limited efficacy of current medical therapies for OP poisoning concerning the development of pharmacoresistance and mitigating proinflammatory response highlights the importance of NMDAR inhibitors in preventing neurotoxic processes and points to new avenues for exploring therapeutics for OP poisoning. [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]

Ampakines—positive allosteric modulators of AMPA-type glutamate receptors (AMPARs)—are drug candidates that have shown substantial promise in pre-clinical models of various neurodegenerative and neuropsychiatric diseases. Much of the study of ampakines has focused on how these drugs modulate neuronal AMPARs to achieve certain therapeutic effects. However, astrocytes also express functional AMPARs and their physiology may be sensitive to modulation by ampakines. Herein, we investigate the effects of multiple ampakines on calcium levels in cortical astrocytes. We find that ampakines augment cytosolic calcium elevations in astrocytes to an extent far greater than that achieved by AMPA alone. This effect is amenable to competitive AMPAR blockade. Furthermore, calcium induction is sensitive to phospholipase Cβ antagonism and blockade of inositol triphosphate receptors located on the endoplasmic reticulum. Low-impact ampakines exerted weaker effects on cytosolic calcium levels in astrocytes and higher concentrations were required to observe an effect. Furthermore, high doses of the low-impact ampakine, CX717, were not toxic to cortical astrocytes at high concentrations, which may serve to differentiate low-impact ampakines from classical AMPAR positive modulators like cyclothiazide. As ampakines are further developed for clinical use, it would be prudent to determine the extent to and manner by which they affect astrocytes, as these effects may also underpin their therapeutic utility in CNS pathologies. [ABSTRACT FROM AUTHOR]

Ampakines are a class of orally available positive allosteric modulators of the AMPA-glutamate receptor (AMPAR) and have therapeutic implications for neurological/neuropsychiatric disorders in which AMPAR signaling is compromised. Low-impact ampakines are a distinct subclass of drugs that only modestly offset receptor desensitization and do not alter agonist binding affinity and thus lack the neurotoxicity and epileptogenic effects associated with other AMPAR modulators. In these studies, we describe the pre-clinical pharmacology of ampakine 1-(benzofurazan-5-ylcarbonyl)morpholine (CX717). CX717 modestly offsets desensitization in hippocampal patches and augments synaptic transmission in vivo. CX717 also enhances long-term potentiation in rats, which is crucial for learning and memory. CX717 enhances performance in the eight-arm radial maze and abrogates amphetamine-induced locomotor activity while being devoid of cataleptic activity in rats. CX717 also ameliorates alfentanil-induced respiratory depression in rats and is not toxic to cultured rat neurons. CX717 is active at doses of 0.3–10 mg/kg and lacked serious adverse events in safety studies in mice up to 2000 mg/kg. CX717 was also previously shown to be safe in humans and effective in reversing opiate-induced respiratory depression and hyperactivity and inattentiveness in adults with ADHD. These findings support the continued clinical investigation of CX717 in the treatment of ADHD, dementia, and opiate-induced respiratory depression. [ABSTRACT FROM AUTHOR]

For several decades, the dopamine hypothesis contributed to the discovery of numerous typical and atypical antipsychotics and was the sole hypothesis for the pathophysiology of schizophrenia. However, neither typical nor atypical antipsychotics, other than clozapine, have been effective in addressing negative symptoms and cognitive impairments, which are indices for the prognostic and disability outcomes of schizophrenia. Following the development of atypical antipsychotics, the therapeutic targets for antipsychotics expanded beyond the blockade of dopamine D2 and serotonin 5-HT2A receptors to explore the partial agonism of the D2 receptor and the modulation of new targets, such as D3, 5-HT1A, 5-HT7, and metabotropic glutamate receptors. Despite these efforts, to date, psychiatry has not successfully developed antipsychotics with antipsychotic properties proven to be superior to those of clozapine. The glutamate hypothesis, another hypothesis regarding the pathophysiology/pathomechanism of schizophrenia, was proposed based on clinical findings that N-methyl-D-aspartate glutamate receptor (NMDAR) antagonists, such as phencyclidine and ketamine, induce schizophrenia-like psychotic episodes. Large-scale genome-wide association studies (GWASs) revealed that approximately 30% of the risk genes for schizophrenia (the total number was over one hundred) encode proteins associated with glutamatergic transmission. These findings supported the validation of the glutamate hypothesis, which was inspired by the clinical findings regarding NMDAR antagonists. Additionally, these clinical and genetic findings suggest that schizophrenia is possibly a syndrome with complicated pathomechanisms that are affected by multiple biological and genetic vulnerabilities. The glutamate hypothesis has been the most extensively investigated pathophysiology/pathomechanism hypothesis, other than the dopamine hypothesis. Studies have revealed the possibility that functional abnormalities of the NMDAR play important roles in the pathophysiology/pathomechanism of schizophrenia. However, no antipsychotics derived from the glutamatergic hypothesis have yet been approved for the treatment of schizophrenia or treatment-resistant schizophrenia. Considering the increasing evidence supporting the potential pro-cognitive effects of glutamatergic agents and the lack of sufficient medications to treat the cognitive impairments associated with schizophrenia, these previous setbacks cannot preclude research into potential novel glutamate modulators. Given this background, to emphasize the importance of the dysfunction of the NMDAR in the pathomechanism and/or pathophysiology of schizophrenia, this review introduces the increasing findings on the functional abnormalities in glutamatergic transmission associated with the NMDAR. [ABSTRACT FROM AUTHOR]

α‐Amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptor (AMPAR) positive allosteric modulators (AMPAkines) have a multitude of promising therapeutic properties. The pharmaceutical development of high impact AMPAkines has, however, been limited by the appearance of calcium‐dependent neuronal toxicity and convulsions in vivo. Such toxicity is not observed at exceptionally high concentrations of low impact AMPAkines. Because most AMPAR are somewhat impermeable to calcium, the current study sought to examine the extent to which different mechanisms contribute to the rise in intracellular calcium in the presence of high impact ampakines. In the presence of AMPA alone, cytosolic calcium elevation is shown to be sodium‐dependent. In the presence of high impact AMPAkines such as cyclothiazide (CTZ) or CX614, however, AMPAR potentiation also activates an additional mechanism that induces calcium release from endoplasmic reticular (ER) stores. The pathway that connects AMPAR to the ER system involves a Gq‐protein, phospholipase Cβ‐mediated inositol triphosphate (InsP3) formation, and ultimately stimulation of InsP3‐receptors located on the ER. The same linkage was not observed using high concentrations of the low impact AMPAkines, CX516 (Ampalex), and CX717. We also demonstrate that CX614 produces neuronal hyper‐excitability at therapeutic doses, whereas the newer generation low impact AMPAkine CX1739 is safe at exceedingly high doses. Although earlier studies have demonstrated a functional linkage between AMPAR and G‐proteins, this report demonstrates that in the presence of high impact AMPAkines, AMPAR also couple to a Gq‐protein, which triggers a secondary calcium release from the ER and provides insight into the disparate actions of high and low impact AMPAkines. [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]

Background Depression is a heterogeneous disorder with high morbidity and disability rates that poses serious problems regarding mental health care. It is now well established that N-methyl D-aspartate receptor (NMDAR) modulators are being increasingly explored as potential therapeutic options for treating depression, although relatively little is known about their mechanisms of action. NMDARs are glutamate-gated ion channels that are ubiquitously expressed in the central nervous system (CNS), and they have been shown to play key roles in excitatory synaptic transmission. GluN2A, the predominant Glu2N subunit of functional NMDARs in neurons, is involved in various physiological processes in the CNS and is associated with diseases such as anxiety, depression, and schizophrenia. However, the role of GluN2A in the pathophysiology of depression has not yet been elucidated. Methods We reviewed several past studies to better understand the function of GluN2A in depression. Additionally, we also summarized the pathogenesis of depression based on the regulation of GluN2A expression, particularly its interaction with neuroinflammation and neurogenesis, which has received considerable critical attention and is highly implicated in the onset of depression. Results These evidence suggests that GluN2A overexpression impairs structural and functional synaptic plasticity, which contributes to the development of depression. Consequently, this knowledge is vital for the development of selective antagonists targeting GluN2A subunits using pharmacological and molecular methods. Conclusions Specific inhibition of the GluN2A NMDAR subunit is resistant to chronic stress-induced depressive-like behaviors, making them promising targets for the development of novel antidepressants. [ABSTRACT FROM AUTHOR]

Two-thirds of signaling hormones and one-third of approved drugs exert their effects by binding and modulating the G protein-coupled receptors (GPCRs) activation. While the activation mechanism for monomeric GPCRs has been well-established, little is known about GPCRs in dimeric form. Here, by combining transition pathway generation, extensive atomistic simulation-based Markov state models, and experimental signaling assays, we reveal an asymmetric, stepwise millisecond allosteric activation mechanism for the metabotropic glutamate receptor subtype 5 receptor (mGlu5), an obligate dimeric class C GPCR. The dynamic picture is presented that agonist binding induces dimeric ectodomains compaction, amplified by the precise association of the cysteine-rich domains, ultimately loosely bringing the intracellular 7-transmembrane (7TM) domains into proximity and establishing an asymmetric TM6-TM6 interface. The active inter-domain interface enhances their intra-domain flexibility, triggering the activation of micro-switches crucial for downstream signal transduction. Furthermore, we show that the positive allosteric modulator stabilizes both the active inter-domain 7TM interface and an open, extended intra-domain ICL2 conformation. This stabilization leads to the formation of a pseudo-cavity composed of the ICL2, ICL3, TM3, and C-terminus, which facilitates G protein coordination. Our strategy may be generalizable for characterizing millisecond events in other allosteric systems. Activation mechanism of GPCRs in dimeric form remains enigmatic. Here, the authors present a dynamic characterization of mGlu5, an obligate dimeric class C GPCR, suggesting an asymmetric, stepwise allosteric activation mechanism. [ABSTRACT FROM AUTHOR]

The anterior cingulate cortex (ACC) is a key cortical region for pain perception and emotion. Different forms of synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD), have been reported in the ACC. Synaptic tagging of LTP plays an important role in hippocampus-related associative memory. In this study, we demonstrate that synaptic tagging of LTD is detected in the ACC of adult male and female mice. This form of tagged LTD requires the activation of metabotropic glutamate receptor subtype 1 (mGluR1). The induction of tagged LTD is time-related with the strongest tagged LTD appearing when the interval between two independent stimuli is 30 min. Inhibitors of mGluR1 blocked the induction of tagged LTD; however, blocking N-methyl-d-aspartate receptors did not affect the induction of tagged LTD. Nimodipine, an inhibitor of L-type voltage–gated calcium channels, also blocked tagged LTD. In an animal model of amputation, we found that tagged LTD was either reduced or completely blocked. Together with our previous report of tagged LTP in the ACC, this study strongly suggests that excitatory synapses in the adult ACC are highly plastic. The biphasic tagging of synaptic transmission provides a new form of heterosynaptic plasticity in the ACC which has functional and pathophysiological significance in phantom pain. [ABSTRACT FROM AUTHOR]