NMDA Receptor Complex Research Articles

Analgesic activity of new ligands of the NMDA receptor complex

BACKGROUND: The activation of spinal cord NMDA receptors is a key factor in the pathogenesis of acute and chronic pain. Therefore, the use of existing NMDA antagonists in analgesic schemes and the development of new compounds targeting the NMDA receptor complex are gaining attention. New ligands of the glutamate NMDA receptor complex are derivatives of imidazole-4,5-dicarboxylic acid. The conformational rigidity of the molecules of imidazole-4,5-dicarboxylic acid derivatives allows for increased selectivity of interaction and reduced side effects. AIM: This study aimed to investigate the analgesic effect of new ligands of the glutamate NMDA receptor complex, which are derivatives of imidazole-4,5-dicarboxylic acid, in rats using the tail-flick test and the formalin test. MATERIALS AND METHODS: The analgesic activity of the compounds was examined in a model of acute somatic (thermal) pain in the tail-flick test and model of somatic pain induced by algogens in the formalin test. The tested compounds (IEM-303 and IEM-2044) were administered intraperitoneally at doses of 5, 10, 15, and 20 mg/kg. Мetamizole was used as the comparison drug. RESULTS: The experiments demonstrated a significant dose-dependent analgesic effect of the tested compounds on the experimental models of acute pain at doses of 5–20 mg/kg. The tail-flick latency increased by 1.4–1.7 times in the IEM-2044 and IEM-303 groups compared with the value in the control group. CONCLUSIONS: The analgesic activity of the tested compounds at 10–20 mg/kg doses was comparable to that of metamizole, indicating the prospect of developing these agents and further searching for effective and safe analgesics in this pharmacological class.

Mapping proteomic composition of excitatory postsynaptic sites in the cerebellar cortex.

Functions of the cerebellar cortex, from motor learning to emotion and cognition, depend on the appropriate molecular composition at diverse synapse types. Glutamate receptor distributions have been partially mapped using immunogold electron microscopy. However, information is lacking on the distribution of many other components, such as Shank2, a postsynaptic scaffolding protein whose cerebellar dysfunction is associated with autism spectrum disorders. Here, we used an adapted Magnified Analysis of the Proteome, an expansion microscopy approach, to map multiple glutamate receptors, scaffolding and signaling proteins at single synapse resolution in the cerebellar cortex. Multiple distinct synapse-selective distribution patterns were observed. For example, AMPA receptors were most concentrated at synapses on molecular layer interneurons and at climbing fiber synapses, Shank1 was most concentrated at parallel fiber synapses on Purkinje cells, and Shank2 at both climbing fiber and parallel fiber synapses on Purkinje cells but little on molecular layer interneurons. Our results are consistent with gene expression data but also reveal input-selective targeting within Purkinje cells. In specialized glomerular structures of the granule cell layer, AMPA receptors as well as most other synaptic components preferentially targeted to synapses. However, NMDA receptors and the synaptic GTPase activating protein SynGAP preferentially targeted to extrasynaptic sites. Thus, glomeruli may be considered integrative signaling units through which mossy fibers differentially activate synaptic AMPA and extrasynaptic NMDA receptor complexes. Furthermore, we observed NMDA receptors and SynGAP at adherens junctions, suggesting a role in structural plasticity of glomeruli. Altogether, these data contribute to mapping the cerebellar 'synaptome'.

Excitotoxicity and ALS: New therapy targets an old mechanism

Excitotoxicity-induced cell death in motor neurons is a major therapeutic target for amyotrophic lateral sclerosis (ALS). Yan etal.1 present a novel compound to specifically disrupt extra-synaptic NMDAR complexes, extending the lifespan of the SOD1G93A ALS mouse and ameliorating cell death.

Impairments of Spatial Memory and N-methyl-d-aspartate Receptors and Their Postsynaptic Signaling Molecules in the Hippocampus of Developing Rats Induced by As, Pb, and Mn Mixture Exposure.

Exposure to metal mixtures is recognized as a real-life scenario, needing novel studies that can assess their complex effects on brain development. There is still a significant public health concern associated with chronic low levels of metal exposure. In contrast to other metals, these three metals (As, Pb, and Mn) are commonly found in various environmental and industrial contexts. In addition to additive or synergistic interactions, concurrent exposure to this metal mixture may also have neurotoxic effects that differ from those caused by exposure to single components. The NMDA receptor and several important signaling proteins are involved in learning, memory, and synaptic plasticity in the hippocampus, including CaMKII, postsynaptic density protein-95 (PSD-95), synaptic Ras GTPase activating protein (SynGAP), a negative regulator of Ras-MAPK activity, and CREB. We hypothesized that alterations in the above molecular players may contribute to metal mixture developmental neurotoxicity. Thus, the aim of this study was to investigate the effect of these metals and their mixture at low doses (As 4 mg, Pb 4 mg, and Mn 10 mg/kg bw/p.o) on NMDA receptors and their postsynaptic signaling proteins during developing periods (GD6 to PD59) of the rat brain. Rats exposed to As, Pb, and Mn individually or at the same doses in a triple-metal mixture (MM) showed impairments in learning and memory functions in comparison to the control group rats. Declined protein expressions of NR2A, PSD-95, p- CaMKII, and pCREB were observed in the metal mix-exposed rats, while the expression of SynGAP was found to be enhanced in the hippocampus as compared to the controls on PD60. Thereby, our data suggest that alterations in the NMDA receptor complex and postsynaptic signaling proteins could explain the cognitive dysfunctions caused by metal-mixture-induced developmental neurotoxicity in rats. These outcomes indicate that incessant metal mixture exposure may have detrimental consequences on brain development.

P-076 - Evaluation of (R)- and (S)-18F-PF-NB1 in non-human primates for imaging the GluN2B subunits of NMDA receptor complex

P-076 - Evaluation of (R)- and (S)-18F-PF-NB1 in non-human primates for imaging the GluN2B subunits of NMDA receptor complex

Treatment resistance NMDA receptor pathway polygenic score is associated with brain glutamate in schizophrenia.

Dysfunction of glutamate neurotransmission has been implicated in the pathophysiology of schizophrenia and may be particularly relevant in severe, treatment-resistant symptoms. The underlying mechanism may involve hypofunction of the NMDA receptor. We investigated whether schizophrenia-related pathway polygenic scores, composed of genetic variants within NMDA receptor encoding genes, are associated with cortical glutamate in schizophrenia. Anterior cingulate cortex (ACC) glutamate was measured in 70 participants across 4 research sites using Proton Magnetic Resonance Spectroscopy (1H-MRS). Two NMDA receptor gene sets were sourced from the Molecular Signatories Database and NMDA receptor pathway polygenic scores were constructed using PRSet. The NMDA receptor pathway polygenic scores were weighted by single nucleotide polymorphism (SNP) associations with treatment-resistant schizophrenia, and associations with ACC glutamate were tested. We then tested whether NMDA receptor pathway polygenic scores with SNPs weighted by associations with non-treatment-resistant schizophrenia were associated with ACC glutamate. A higher NMDA receptor complex pathway polygenic score was significantly associated with lower ACC glutamate (β=-0.25, 95% CI=-0.49, -0.02, competitive p=0.03). When SNPs were weighted by associations with non-treatment-resistant schizophrenia, there was no association between the NMDA receptor complex pathway polygenic score and ACC glutamate (β=0.05, 95% CI=-0.18, 0.27, competitive p=0.79). These results provide initial evidence of an association between common genetic variation implicated in NMDA receptor function and ACC glutamate levels in schizophrenia. This association was specific to when the NMDA receptor complex pathway polygenic score was weighted by SNP associations with treatment-resistant schizophrenia.

Cognitive dysfunction and impaired neuroplasticity following repeated exposure to the synthetic cannabinoid JWH-018 in male mice.

Psychotic disorders have been reported in long-term users of synthetic cannabinoids. This study aims at investigating the long-lasting effects of repeated JWH-018 exposure. Male CD-1 mice were injected with vehicle, JWH-018 (6mg·kg-1 ), the CB1 -antagonist NESS-0327 (1mg·kg-1 ) or co-administration of NESS-0327 and JWH-018, every day for 7days. After 15 or 16 days washout, we investigated the effects of JWH-018 on motor function, memory, social dominance and prepulse inhibition (PPI). We also evaluated glutamate levels in dialysates from dorsal striatum, striatal dopamine content and striatal/hippocampal neuroplasticity focusing on the NMDA receptor complex and the neurotrophin BDNF. These measurements were accompanied by in vitro electrophysiological evaluations in hippocampal preparations. Finally, we investigated the density of CB1 receptors and levels of the endocannabinoid anandamide (AEA) and 2-arachidonoylglycerol (2-AG) and their main synthetic and degrading enzymes in the striatum and hippocampus. The repeated treatment with JWH-018 induced psychomotor agitation while reducing social dominance, recognition memory and PPI in mice. JWH-018 disrupted hippocampal LTP and decreased BDNF expression, reduced the synaptic levels of NMDA receptor subunits and decreased the expression of PSD95. Repeated exposure to JWH-018, reduced hippocampal CB1 receptor density and induced a long-term alteration in AEA and 2-AG levels and their degrading enzymes, FAAH and MAGL, in the striatum. Our findings suggest that repeated administration of a high dose of JWH-018 leads to the manifestation of psychotic-like symptoms accompanied by alterations in neuroplasticity and change in the endocannabinoid system.

Oxidative stress responses and their alterations in the Nrf2-NMDA receptor pathway in the brain of suicide victims.

Suicide is a global public health concern. There is evidence of an association between suicidal behavior and depressive disorders (DDs). An increasing number of studies have suggested that nuclear factor erythroid-derived 2-like 2 (Nrf2), a major endogenous regulator of the oxidative stress response, can be a novel target for the neurobiology of suicide-related disorders (including depression). This study aimed to investigate the relationship between oxidative stress progression, Nrf2 regulation, and N-methyl-D-aspartate receptor (NMDA) subunit composition in the hippocampus (Hp) and frontal cortex (FCx) of suicide victims (n=14) and matched controls (n=8). Furthermore, zinc and magnesium concentrations and their potency to inhibit [3H] MK-801 (radioactively labeled form of MK-801 - dizocilpine, a well-characterized NMDAR channel uncompetitive antagonist frequently used in receptor-binding assays) binding to NMDA receptor channels were measured. Our results revealed a statistically significant increase in protein carbonyl levels and thiobarbituric acid-reactive substances (TBARS) concentrations in Hp and FCx of suicide victims. Enhanced superoxide dismutase (SOD) activity (only in FCx) in suicides compared to controls was shown. These alterations were accompanied by an increase in Nrf2 protein levels in whole homogeneous tissue lysates and cytosolic fractions of Hp and FCx. Importantly, suicide victims presented a significant reduction in Nrf2 protein levels in the nuclear fraction of FCx. Finally, the observed decrease in N-methyl-D-aspartate receptor subunit 2B (GluN2B) and postsynaptic density proteins 95 (PSD-95) protein levels was associated with a statistically significant reduction in magnesium levels in the FCx of suicide victims. These results confirm for the first time that increased oxidative stress parameters are related to Nrf2 protein changes and alterations in the NMDA receptor complex in the pathophysiology of suicidal behavior.

Investigation of antiparkinsonian activity of new imidazole-4,5-dicarboxylic acid derivatives on the experimental model of catalepsy

Introduction: To study the antiparkinsonian activity of new ligands of the glutamate NMDA receptor complex – 1,2–substituted imidazole-4,5-dicarboxylic acids – on an experimental model of catalepsy caused by haloperidolintraabdominal injections in rats. Materials and methods: The experiments were performed on Wistar rats weighing 300-350 g, obtained from the Rappolovo nursery of the Russian Academy of Medical Sciences (Leningrad Region). The animals were kept in standard plastic cages in vivarium conditions with free access to water and food at a temperature of 22±2 °C and in the experiment were divided into several groups (6 animals each). All the experiments were carried out in the autumn-winter period. The animals were kept in accordance with the rules of laboratory practice (GLP), regulatory documents ”Sanitary Rules for the Device, Equipment and Maintenance of Vivarium” and the Order of the Ministry of Health and Social Development of the Russian Federation dated 23.08.2010 No. 708n “On Approval of the Rules of Laboratory Practice”. Imidazole-dicarboxylic acid derivatives (IEM-2295, IEM-2296) were injected intraperitoneally at doses from 5 mg/kg to 40 mg/kg simultaneously with haloperidol at a dose of 1 mg/kg, after which the duration and severity of catalepsy were evaluated after 30, 60, 120 minutes from 0 to 6 points according to the Morpurgo method. Results: The severity of catalepsy with the injection of IEM-2295 decreased on average to 3 points, while in the control group it remained at the level of 6 points throughout the observation. However, the severity of catalepsy with the introduction of IEM-2296 decreased to an average of 4 points, but the effect itself lasted longer than with the introduction of IEM-2295. Thus, it was noted that by the 120th minute of observation, the severity of catalepsy in rats receiving the IEM-2295 compound averaged 5 points, whereas in animals receiving IEM-2296 – 3 points. Discussion: Basing on the results of our work and similar experiments, we can conclude that the studied compounds, which are not channel blockers, have an active effect on dopaminergic neurotransmission, because of which the symptoms of catalepsy that occur when haloperidol is injected to rats were stopped to one degree or another. Conclusion: The studied substances exhibit antiparkinsonian activity on an experimental haloperidol model of catalepsy in rats and are promising for development as potential therapies for neurodegenerative diseases. Further study of these compounds and other ligands from the NMDA-blocker group in a wider sample on the catalepsy model, as well as on other models of Parkinsonism, is required. Graphical Abstract

Zinc as an inhibitor of NMDA receptor can exhibit antidepressant effect

Background : New antidepressant strategies are needed, due to unsatisfactory clinical efficacy and many side effects of commonly used drugs. Recent studies linking the pathophysiology of depression with glutamatergic imbalance. There is hyperactivity of the main excitatory system (glutamatergic) to its inhibition (GABAergic). N-methyl D-aspartate (NMDA) receptors as a part of glutamatergic synapses are potential targets for intervention. Antagonist administration for glutamatergic systems, such as zinc, can exhibit antidepressant effects.
 Objective : To observe the effect of zinc administration on NMDA receptors in depressed subjects
 Methods : In this paper, we provide a literature review. The method to achieve the objective consists of using literature exploration, which was conducted from February to June 2022 by searching the relevant studies from several databases.
 Results : Study trials both in human and animal subjects reveal that depression is associated with a lower concentration of zinc. Comparison between the lowest zinc intake with the highest zinc intake had significantly lower incidence of developing depression. Dietary zinc deficiency induces depression along with upregulation of the NMDA receptor complexes. Zinc’s antidepressant effects might be mediated through its action reducing NMDA channel-opening frequency.
 Conclusions : The presence of zinc may downregulate the glutamate response in binding to NMDA receptors. Because of numerous studies about the connection between zinc and depression, it seems that zinc may have the potency to develop new antidepressants. Since the capability of zinc administration to reduce depressive symptoms, it is expected leading to increased medication adherence, lower costs and better outcomes.

Convergent Energy State-Dependent Antagonistic Signaling by Cocaine- and Amphetamine-Regulated Transcript (CART) and Neuropeptide Y (NPY) Modulates the Plasticity of Forebrain Neurons to Regulate Feeding in Zebrafish.

Dynamic reconfiguration of circuit function subserves the flexibility of innate behaviors tuned to physiological states. Internal energy stores adaptively regulate feeding-associated behaviors and integrate opposing hunger and satiety signals at the level of neural circuits. Across vertebrate lineages, the neuropeptides cocaine- and amphetamine-regulated transcript (CART) and neuropeptide Y (NPY) have potent anorexic and orexic functions, respectively, and show energy-state-dependent expression in interoceptive neurons. However, how the antagonistic activities of these peptides modulate circuit plasticity remains unclear. Using behavioral, neuroanatomical, and activity analysis in adult zebrafish of both sexes, along with pharmacological interventions, we show that CART and NPY activities converge on a population of neurons in the dorsomedial telencephalon (Dm). Although CART facilitates glutamatergic neurotransmission at the Dm, NPY dampens the response to glutamate. In energy-rich states, CART enhances NMDA receptor (NMDAR) function by protein kinase A/protein kinase C (PKA/PKC)-mediated phosphorylation of the NR1 subunit of the NMDAR complex. Conversely, starvation triggers NPY-mediated reduction in phosphorylated NR1 via calcineurin activation and inhibition of cAMP production leading to reduced responsiveness to glutamate. Our data identify convergent integration of CART and NPY inputs by the Dm neurons to generate nutritional state-dependent circuit plasticity that is correlated with the behavioral switch induced by the opposing actions of satiety and hunger signals.SIGNIFICANCE STATEMENT Internal energy needs reconfigure neuronal circuits to adaptively regulate feeding behavior. Energy-state-dependent neuropeptide release can signal energy status to feeding-associated circuits and modulate circuit function. CART and NPY are major anorexic and orexic factors, respectively, but the intracellular signaling pathways used by these peptides to alter circuit function remain uncharacterized. We show that CART and NPY-expressing neurons from energy-state interoceptive areas project to a novel telencephalic region, Dm, in adult zebrafish. CART increases the excitability of Dm neurons, whereas NPY opposes CART activity. Antagonistic signaling by CART and NPY converge onto NMDA-receptor function to modulate glutamatergic neurotransmission. Thus, opposing activities of anorexic CART and orexic NPY reconfigure circuit function to generate flexibility in feeding behavior.

Targeting NMDA Receptor Complex in Management of Epilepsy.

N-methyl-D-aspartate receptors (NMDARs) are widely distributed in the central nervous system (CNS) and play critical roles in neuronal excitability in the CNS. Both clinical and preclinical studies have revealed that the abnormal expression or function of these receptors can underlie the pathophysiology of seizure disorders and epilepsy. Accordingly, NMDAR modulators have been shown to exert anticonvulsive effects in various preclinical models of seizures, as well as in patients with epilepsy. In this review, we provide an update on the pathologic role of NMDARs in epilepsy and an overview of the NMDAR antagonists that have been evaluated as anticonvulsive agents in clinical studies, as well as in preclinical seizure models.

P140Cap Regulates the Composition and Localization of the NMDAR Complex in Synaptic Lipid Rafts.

The NMDARs are key players in both physiological and pathologic synaptic plasticity because of their involvement in many aspects of neuronal transmission as well as learning and memory. The contribution in these events of different types of GluN2A-interacting proteins is still unclear. The p140Cap scaffold protein acts as a hub for postsynaptic complexes relevant to psychiatric and neurologic disorders and regulates synaptic functions, such as the stabilization of mature dendritic spine, memory consolidation, LTP, and LTD. Here we demonstrate that p140Cap directly binds the GluN2A subunit of NMDAR and modulates GluN2A-associated molecular network. Indeed, in p140Cap KO male mice, GluN2A is less associated with PSD95 both in ex vivo synaptosomes and in cultured hippocampal neurons, and p140Cap expression in KO neurons can rescue GluN2A and PSD95 colocalization. p140Cap is crucial in the recruitment of GluN2A-containing NMDARs and, consequently, in regulating NMDARs' intrinsic properties. p140Cap is associated to synaptic lipid-raft (LR) and to soluble postsynaptic membranes, and GluN2A and PSD95 are less recruited into synaptic LR of p140Cap KO male mice. Gated-stimulated emission depletion microscopy on hippocampal neurons confirmed that p140Cap is required for embedding GluN2A clusters in LR in an activity-dependent fashion. In the synaptic compartment, p140Cap influences the association between GluN2A and PSD95 and modulates GluN2A enrichment into LR. Overall, such increase in these membrane domains rich in signaling molecules results in improved signal transduction efficiency.SIGNIFICANCE STATEMENT Here we originally show that the adaptor protein p140Cap directly binds the GluN2A subunit of NMDAR and modulates the GluN2A-associated molecular network. Moreover, we show, for the first time, that p140Cap also associates to synaptic lipid rafts and controls the selective recruitment of GluN2A and PSD95 to this specific compartment. Finally, gated-stimulated emission depletion microscopy on hippocampal neurons confirmed that p140Cap is required for embedding GluN2A clusters in lipid rafts in an activity-dependent fashion. Overall, our findings provide the molecular and functional dissection of p140Cap as a new active member of a highly dynamic synaptic network involved in memory consolidation, LTP, and LTD, which are known to be altered in neurologic and psychiatric disorders.

Multiple roles of GluN2D-containing NMDA receptors in short-term potentiation and long-term potentiation in mouse hippocampal slices

The GluN2 subunits of N-methyl-d-aspartate receptors (NMDARs) are key drivers of synaptic plasticity in the brain, where the particular GluN2 composition endows the NMDAR complex with distinct pharmacological and physiological properties. Compared to GluN2A and GluN2B subunits, far less is known about the role of the GluN2D subunit in synaptic plasticity. In this study, we have used a GluN2C/2D selective competitive antagonist, UBP145, in combination with a GluN2D global knockout (GluN2D KO) mouse line to study the contribution of GluN2D-containing NMDARs to short-term potentiation (STP) and long-term potentiation (LTP) in the CA1 region of mouse hippocampal slices. We made several distinct observations: First, GluN2D KO mice have higher levels of LTP compared to wild-type (WT) mice, an effect that was occluded by blockade of GABA receptor-mediated inhibition or by using a strong LTP induction protocol. Second, UBP145 partially inhibited LTP in WT but not GluN2D KO mice. Third, UBP145 inhibited a component of STP, termed STP2, in WT but not GluN2D KO mice. Taken together, these findings suggest an involvement for GluN2D-containing NMDARs in both STP and LTP in mouse hippocampus.This article is part of the Neuropharmacology Special Issue on ‘Glutamate Receptors – NMDA receptors’.

The Implication of STEP in Synaptic Plasticity and Cognitive Impairments in Alzheimer's Disease and Other Neurological Disorders.

STriatal-Enriched protein tyrosine Phosphatase (STEP) is a tyrosine phosphatase that has been implicated in Alzheimer’s disease (AD), the most common form of dementia, and many other neurological diseases. The protein level and activity of STEP have been found to be elevated in most of these disorders, and specifically in AD as a result of dysregulation of different pathways including PP2B/DARPP32/PP1, PKA as well as impairments of both proteasomal and lysosomal systems. The upregulation in STEP leads to increased binding to, and dephosphorylation of, its substrates which are mainly found to be synaptic plasticity and thus learning and memory related proteins. These proteins include kinases like Fyn, Pyk2, ERK1/2 and both NMDA and AMPA receptor subunits GluN2B and GluA2. The dephosphorylation of these molecules results in inactivation of these kinases and internalization of NMDA and AMPA receptor complexes leading to synapse loss and cognitive impairments. In this study, we aim to review STEP regulation and its implications in AD as well as other neurological disorders and then summarize data on targeting STEP as therapeutic strategy in these diseases.

CYFIP1 Dosages Exhibit Divergent Behavioral Impact via Diametric Regulation of NMDA Receptor Complex Translation in Mouse Models of Psychiatric Disorders

BackgroundGene dosage imbalance caused by copy number variations (CNVs) is a prominent contributor to brain disorders. In particular, 15q11.2 CNV duplications and deletions have been associated with autism spectrum disorder and schizophrenia, respectively. The mechanism underlying these diametric contributions remains unclear. MethodsWe established both loss-of-function and gain-of-function mouse models of Cyfip1, one of four genes within 15q11.2 CNVs. To assess the functional consequences of altered CYFIP1 levels, we performed systematic investigations on behavioral, electrophysiological, and biochemical phenotypes in both mouse models. In addition, we utilized RNA immunoprecipitation sequencing (RIP-seq) analysis to reveal molecular targets of CYFIP1 in vivo. ResultsCyfip1 loss-of-function and gain-of function mouse models exhibited distinct and shared behavioral abnormalities related to autism spectrum disorder and schizophrenia. RIP-seq analysis identified messenger RNA targets of CYFIP1 in vivo, including postsynaptic NMDA receptor (NMDAR) complex components. In addition, these mouse models showed diametric changes in levels of postsynaptic NMDAR complex components at synapses because of dysregulated protein translation, resulting in bidirectional alteration of NMDAR-mediated signaling. Importantly, pharmacological balancing of NMDAR signaling in these mouse models with diametric Cyfip1 dosages rescues behavioral abnormalities. ConclusionsCYFIP1 regulates protein translation of NMDAR and associated complex components at synapses to maintain normal synaptic functions and behaviors. Our integrated analyses provide insight into how gene dosage imbalance caused by CNVs may contribute to divergent neuropsychiatric disorders.

Structural and functional brain-wide alterations in A350V Iqsec2 mutant mice displaying autistic-like behavior

IQSEC2 is an X-linked gene that is associated with autism spectrum disorder (ASD), intellectual disability, and epilepsy. IQSEC2 is a postsynaptic density protein, localized on excitatory synapses as part of the NMDA receptor complex and is suggested to play a role in AMPA receptor trafficking and mediation of long-term depression. Here, we present brain-wide structural volumetric and functional connectivity characterization in a novel mouse model with a missense mutation in the IQ domain of IQSEC2 (A350V). Using high-resolution structural and functional MRI, we show that animals with the A350V mutation display increased whole-brain volume which was further found to be specific to the cerebral cortex and hippocampus. Moreover, using a data-driven approach we identify putative alterations in structure–function relations of the frontal, auditory, and visual networks in A350V mice. Examination of these alterations revealed an increase in functional connectivity between the anterior cingulate cortex and the dorsomedial striatum. We also show that corticostriatal functional connectivity is correlated with individual variability in social behavior only in A350V mice, as assessed using the three-chamber social preference test. Our results at the systems-level bridge the impact of previously reported changes in AMPA receptor trafficking to network-level disruption and impaired social behavior. Further, the A350V mouse model recapitulates similarly reported brain-wide changes in other ASD mouse models, with substantially different cellular-level pathologies that nonetheless result in similar brain-wide alterations, suggesting that novel therapeutic approaches in ASD that result in systems-level rescue will be relevant to IQSEC2 mutations.

Serotonin 2B Receptor by Interacting with NMDA Receptor and CIPP Protein Complex May Control Structural Plasticity at Glutamatergic Synapses.

The serotonin 2B (5-HT2B) receptor coupled to Gq-protein contributes to the control of neuronal excitability and is implicated in various psychiatric disorders. The mechanisms underlying its brain function are not fully described. Using peptide affinity chromatography combined with mass spectrometry, we found that the PDZ binding motif of the 5-HT2B receptor located at its C-terminal end interacts with the scaffolding protein channel interacting PDZ protein (CIPP). We then showed, in COS-7 cells, that the association of the 5-HT2B receptor to CIPP enhanced receptor-operated inositol phosphate (IP) production without affecting its cell surface and intracellular levels. Co-immunoprecipitation experiments revealed that CIPP, the 5-HT2B receptor, and the NR1 subunit of the NMDA receptor form a macromolecular complex. CIPP increased 5-HT2B receptor clustering at the surface of primary cultured hippocampal neurons and prevented receptor dispersion following agonist stimulation, thus potentiating IP production and intracellular calcium mobilization in dendrites. CIPP or 5-HT2B receptor stimulation in turn dispersed NR1 clusters colocalized with 5-HT2B receptors and increased the density and maturation of dendritic spines. Collectively, our results suggest that the 5-HT2B receptor, the NMDA receptor, and CIPP may form a signaling platform by which serotonin can influence structural plasticity of excitatory glutamatergic synapses.

Early and Delayed Impact of Nanosilver on the Glutamatergic NMDA Receptor Complex in Immature Rat Brain.

Silver nanoparticles (AgNPs) are the one of the most extensively used nanomaterials. The strong antimicrobial properties of AgNPs have led to their use in a wide range of medical and consumer products. Although the neurotoxicity of AgNPs has been confirmed, the molecular mechanisms have not been extensively studied, particularly in immature organisms. Based on information gained from previous in vitro studies, in the present work, we examine whether ionotropic NMDA glutamate receptors contribute to AgNP-induced neurotoxicity in an animal model of exposure. In brains of immature rats subjected to a low dose of AgNPs, we identified ultrastructural and molecular alterations in the postsynaptic region of synapses where NMDA receptors are localized as a multiprotein complex. We revealed decreased expression of several NMDA receptor complex-related proteins, such as GluN1 and GluN2B subunits, scaffolding proteins PSD95 and SynGAP, as well as neuronal nitric oxide synthase (nNOS). Elucidating the changes in NMDA receptor-mediated molecular mechanisms induced by AgNPs, we also identified downregulation of the GluN2B-PSD95-nNOS-cGMP signaling pathway which maintains LTP/LTD processes underlying learning and memory formation during development. This observation is accompanied by decreased density of NMDA receptors, as assessed by a radioligand binding assay. The observed effects are reversible over the post-exposure time. This investigation reveals that NMDA receptors in immature rats are a target of AgNPs, thereby indicating the potential health hazard for children and infants resulting from the extensive use of products containing AgNPs.

ДЕЙСТВИЕ КОМБИНАЦИЙ МЕЛАТОНИНА С ПРОИЗВОДНЫМИ 3-ГИДРОКСИПИРИДИНА НА НЕЙРОНЫ I ВЕСТИБУЛЯРНОЙ ЗОНЫ КОРЫ БОЛЬШОГО МОЗГА У ЖИВОТНЫХ

Experiments with cats showed that new 3-hydroxypyridine derivative IBKhF-27, mexidol and melatonin, and combination of IBKhF-27 with melatonin and mexidol affected directly 84.8; 67.8; 77.4; 97.9 and 88.1 % neurons of the 1st vestibular zone of the cerebral cortex, respectively. Inhibition by IBKhF-27 was observed 1.4 times more often than by mexidol. Combinations of IBKhF-27 with melatonin and mexidol produced the inhibitive effects on neurons oftener than each component separately; the direct effect of IBKhF-27 with melatonin occurred oftener than each of these two components separately. Also, the inhibitive effect of IBKhF-27 with melatonin was seen more often than of melatonin combined with mexidol. In the presence of MK-801, specific noncompetitive antagonist of the NMDA-receptor complex and luzindol, specific antagonist of melatonin MT1- and MT2-receptors (before pneumomicroinjection dosages), the direct effect of IBKhF-27 with melatonin or mexidol on the spontaneous activity of neurons was prevented fully or attenuated materially in 95.3 and 88.2 % neurons, respectively. Consequently, 1st vestibular zone of the cerebral cortex has a great role in the central action of these combinations executed fully or partly through the NMDA-receptor complex and melatonin MT1-, MT2-receptors.