Bidirectional effects of inhibiting or activating NMDA receptors on extinction after cocaine self-administration in rats

PubMed Central

Hafenbreidel, Madalyn; Todd, Carolynn Rafa; Twining, Robert C.; Tuscher, Jennifer J.; Mueller, Devin

2014-01-01

Rationale Extinction of drug seeking is facilitated by NMDA receptor (NMDAr) agonists, but it remains unclear whether extinction is dependent on NMDAr activity. Objectives We investigated the necessity of NMDArs for extinction of cocaine seeking, and whether extinction altered NMDAr expression within extinction-related neuroanatomical loci. Methods Rats were trained to lever press for i.v. infusions of cocaine or sucrose reinforcement prior to extinction training or withdrawal. Results Administration of the NMDAr competitive antagonist CPP prior to four brief extinction sessions impaired subsequent extinction retention. In contrast, post-extinction administration of the NMDAr coagonist D-serine attenuated lever pressing across days as compared to saline administration, indicative of facilitated consolidation of extinction. Furthermore, expression of the NMDAr subunits, GluN2A and GluN2B, was not altered in the ventromedial prefrontal cortex. However, both GluN2A and GluN2B subunit expression in the nucleus accumbens was increased following cocaine self-administration, and this increased expression was relatively resistant to modulation by extinction. Conclusions Our findings demonstrate that extinction of cocaine seeking is bidirectionally mediated by NMDArs and suggest that selective modulation of NMDAr activity could facilitate extinction-based therapies for treatment of cocaine abuse. PMID:24847958

Making of a Synapse: Recurrent Roles of Drebrin A at Excitatory Synapses Throughout Life.

PubMed

Aoki, Chiye; Sherpa, Ang D

2017-01-01

Mature excitatory synapses are composed of more than 1500 proteins postsynaptically and hundreds more that operate presynaptically. Among them, drebrin is an F-actin-binding protein that increases noticeably during juvenile synaptogenesis. Electron microscopic analysis reveals that drebrin is highly enriched specifically on the postsynaptic side of excitatory synapses. Since dendritic spines are structures specialized for excitatory synaptic transmission, the function of drebrin was probed by analyzing the ultrastructural characteristics of dendritic spines of animals with genetic deletion of drebrin A (DAKO), the adult isoform of drebrin. Electron microscopic analyses revealed that these brains are surprisingly intact, in that axo-spinous synaptic junctions are well-formed and not significantly altered in number. This normal ultrastructure may be because drebrin E, the alternate embryonic isoform, compensates for the genetic deletion of drebrin A. However, DAKO results in the loss of homeostatic plasticity of N-methyl-D-aspartate receptors (NMDARs). The NMDAR activation-dependent trafficking of the NR2A subunit-containing NMDARs from dendritic shafts into spine head cytoplasm is greatly diminished within brains of DAKO. Conversely, within brains of wild-type rodents, spines respond to NMDAR blockade with influx of F-actin, drebrin A, and NR2A subunits of NMDARs. These observations indicate that drebrin A facilitates the trafficking of NMDAR cargos in an F-actin-dependent manner to mediate homeostatic plasticity. Analysis of the brains of transgenic mice used as models of Alzheimer's disease (AD) reveals that the loss of drebrin from dendritic spines predates the emergence of synaptic dysfunction and cognitive impairment, suggesting that this form of homeostatic plasticity contributes toward cognition. Two studies suggest that the nature of drebrin's interaction with NMDARs is dependent on the receptor's subunit composition. Drebrin A can be found co-clustering with NR2B-containing NMDARs at the plasma membrane, while NR2A-containing NMDARs co-traffic into the spine cytoplasm but do not co-cluster at the plasma membrane. Most recently, we encountered a physiological condition that supports this idea. When adolescent female rats are reared under a condition of restricted food access and ad libitum wheel access, they paradoxically become excessive runners, choosing to run, even during the limited hours of food availability. This behavioral pattern is termed activity-based anorexia (ABA) and has served as an animal model for anorexia nervosa. Those animals that exhibit the greatest ABA vulnerability, in that they lose the most amount of body weight and run with greatest exuberance to the point of risking their lives, exhibit the highest levels of NR2B-NMDARs and drebrin at the postsynaptic membrane of hippocampal pyramidal neurons. Those animals that exhibit the greatest resilience to ABA, in that they run minimally under such condition, thereby losing minimal amount of weight, exhibit the highest level of NR2A-NMDARs in the spine cytoplasm and lowest levels of drebrin at the postsynaptic membrane. This pattern suggests that drebrin has dual roles: retention of NR2A-NMDARs in the reserve pool and trafficking of NR2B-NMDARs to the postsynaptic membrane, ultimately contributing to an individual's reactivity to stress. Altogether, these observations indicate that drebrin is a protein that is important for synaptic plasticity and deserves the attention of neuroscientists studying the neurobiological basis of cognition and stress reactivity.

GluN1 and GluN2A NMDA Receptor Subunits Increase in the Hippocampus during Memory Consolidation in the Rat.

PubMed

Cercato, Magali C; Vázquez, Cecilia A; Kornisiuk, Edgar; Aguirre, Alejandra I; Colettis, Natalia; Snitcofsky, Marina; Jerusalinsky, Diana A; Baez, María V

2016-01-01

It is widely accepted that NMDA receptors (NMDAR) are required for learning and memory formation, and for synaptic plasticity induction. We have previously shown that hippocampal GluN1 and GluN2A NMDAR subunits significantly increased following habituation of rats to an open field (OF), while GluN2B remained unchanged. Similar results were obtained after CA1-long-term potentiation (LTP) induction in rat hippocampal slices. Other studies have also shown NMDAR up regulation at earlier and later time points after LTP induction or learning acquisition. In this work, we have studied NMDAR subunits levels in the hippocampus and prefrontal cortex (PFC) after OF habituation and after object recognition (OR), to find out whether rising of NMDAR subunits is a general and structure-specific feature during memory formation. In 1, 2 and 3 month old rats there was an increase in hippocampal GluN1 and GluN2A, but not in GluN2B levels 70 min after OF habituation. This rise overlaps with early phase of memory consolidation, suggesting a putative relationship between them. The increases fell down to control levels 90 min after training. Similar results were obtained in the hippocampus of adult rats 70 min after OR training, without changes in PFC. Following OF test or OR discrimination phase, NMDAR subunits remained unchanged. Hence, rising of hippocampal GluN1 and GluN2A appears to be a general feature after novel "spatial/discrimination" memory acquisition. To start investigating the dynamics and possible mechanisms of these changes, we have studied hippocampal neuron cultures stimulated by KCl to induce plasticity. GluN1 and GluN2A increased both in dendrites and neuronal bodies, reaching a maximum 75 min later and returning to control levels at 90 min. Translation and/or transcription and mobilization differentially contribute to this rise in subunits in bodies and dendrites. Our results showed that the NMDAR subunits increase follows a similar time course both in vitro and in vivo . These changes happen in the hippocampus where a spatial representation of the environment is being formed making possible short term and long term memories (STM and LTM); appear to be structure-specific; are preserved along life; and could be related to synaptic tagging and/or to memory consolidation of new spatial/discrimination information.

NMDA receptor subunits and associated signaling molecules mediating antidepressant-related effects of NMDA-GluN2B antagonism

PubMed Central

Kiselycznyk, Carly; Jury, Nicholas; Halladay, Lindsay; Nakazawa, Kazu; Mishina, Masayoshi; Sprengel, Rolf; Grant, Seth G.N.; Svenningsson, Per; Holmes, Andrew

2015-01-01

Drugs targeting the glutamate N-methyl-D-aspartate receptor (NMDAR) may be efficacious for treating mood disorders, as exemplified by the rapid antidepressant effects produced by single administration of the NMDAR antagonist ketamine. Though the precise mechanisms underlying the antidepressant-related effects of NMDAR antagonism remain unclear, recent studies implicate specific NMDAR subunits, including GluN2A and GluN2B, as well as the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR) subunit glutamate receptor interacting molecule, PSD-95. Here, integrating mutant and pharmacological in mice, we investigated the contribution of these subunits and molecules to antidepressant-related behaviors and the antidepressant-related effects of the GluN2B blocker, Ro 25-6981. We found that global deletion of GluA1 or PSD-95 reduced forced swim test (FST) immobility, mimicking the antidepressant-related effect produced by systemically administered Ro 25-6981 in C57BL/6J mice. Moreover, the FST antidepressant-like effects of systemic Ro 25-6981 were intact in mutants with global GluA1 deletion or GluN1 deletion in forebrain interneurons, but were absent in mutants constitutively lacking GluN2A or PSD-95. Next, we found that microinfusing Ro 25-6981 into the medial prefrontal cortex (mPFC), but not basolateral amygdala, of C57BL/6J mice was sufficient to produce an antidepressant-like effect. Together, these findings extend and refine current understanding of the mechanisms mediating antidepressant-like effects produced by NMDAR-GluN2B antagonists, and may inform the development of a novel class of medications for treating depression that target the GluN2B subtype of NMDAR. PMID:25800971

Atomoxetine affects transcription/translation of the NMDA receptor and the norepinephrine transporter in the rat brain – an in vivo study

PubMed Central

Udvardi, Patrick T; Föhr, Karl J; Henes, Carolin; Liebau, Stefan; Dreyhaupt, Jens; Boeckers, Tobias M; Ludolph, Andrea G

2013-01-01

Attention-deficit/hyperactivity disorder (ADHD) is the most frequently diagnosed neurodevelopmental disorder. The norepinephrine transporter (NET) inhibitor atomoxetine, the first nonstimulant drug licensed for ADHD treatment, also acts as an N-methyl-D-aspartate receptor (NMDAR) antagonist. The compound’s effects on gene expression and protein levels of NET and NMDAR subunits (1, 2A, and 2B) are unknown. Therefore, adolescent Sprague Dawley rats were treated with atomoxetine (3 mg/kg, intraperitoneal injection [ip]) or saline (0.9%, ip) for 21 consecutive days on postnatal days (PND) 21–41. In humans, atomoxetine’s earliest clinical therapeutic effects emerge after 2–3 weeks. Material from prefrontal cortex, striatum (STR), mesencephalon (MES), and hippocampus (HC) was analyzed either directly after treatment (PND 42) or 2 months after termination of treatment (PND 101) to assess the compound’s long-term effects. In rat brains analyzed immediately after treatment, protein analysis exhibited decreased levels of the NET in HC, and NMDAR subunit 2B in both STR and HC; the transcript levels were unaltered. In rat brains probed 2 months after final atomoxetine exposure, messenger RNA analysis also revealed significantly reduced levels of genes coding for NMDAR subunits in MES and STR. NMDAR protein levels were reduced in STR and HC. Furthermore, the levels of two SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, synaptophysin and synaptosomal-associated protein 25, were also significantly altered in both treatment groups. This in vivo study detected atomoxetine’s effects beyond NET inhibition. Taken together, these data reveal that atomoxetine seems to decrease glutamatergic transmission in a brain region-specific manner. Long-term data show that the compound’s impact is not due to an acute pharmacological effect but lasts or even amplifies after a drug-free period of 2 months, leading to altered development of synaptic composition. These alterations might contribute to atomoxetine’s clinical effects in the treatment of ADHD, a neurodevelopmental disorder in which synaptic processes and especially a dysregulated glutamatergic metabolism seem to be involved. PMID:24348020

A Metabotropic-Like Flux-Independent NMDA Receptor Regulates Ca2+ Exit from Endoplasmic Reticulum and Mitochondrial Membrane Potential in Cultured Astrocytes.

PubMed

Montes de Oca Balderas, Pavel; Aguilera, Penélope

2015-01-01

Astrocytes were long thought to be only structural cells in the CNS; however, their functional properties support their role in information processing and cognition. The ionotropic glutamate N-methyl D-aspartate (NMDA) receptor (NMDAR) is critical for CNS functions, but its expression and function in astrocytes is still a matter of research and debate. Here, we report immunofluorescence (IF) labeling in rat cultured cortical astrocytes (rCCA) of all NMDAR subunits, with phenotypes suggesting their intracellular transport, and their mRNA were detected by qRT-PCR. IF and Western Blot revealed GluN1 full-length synthesis, subunit critical for NMDAR assembly and transport, and its plasma membrane localization. Functionally, we found an iCa2+ rise after NMDA treatment in Fluo-4-AM labeled rCCA, an effect blocked by the NMDAR competitive inhibitors D(-)-2-amino-5-phosphonopentanoic acid (APV) and Kynurenic acid (KYNA) and dependent upon GluN1 expression as evidenced by siRNA knock down. Surprisingly, the iCa2+ rise was not blocked by MK-801, an NMDAR channel blocker, or by extracellular Ca2+ depletion, indicating flux-independent NMDAR function. In contrast, the IP3 receptor (IP3R) inhibitor XestosponginC did block this response, whereas a Ryanodine Receptor inhibitor did so only partially. Furthermore, tyrosine kinase inhibition with genistein enhanced the NMDA elicited iCa2+ rise to levels comparable to those reached by the gliotransmitter ATP, but with different population dynamics. Finally, NMDA depleted the rCCA mitochondrial membrane potential (mΔψ) measured with JC-1. Our results demonstrate that rCCA express NMDAR subunits which assemble into functional receptors that mediate a metabotropic-like, non-canonical, flux-independent iCa2+ increase.

Functional Adaptation of the N-Methyl-d-aspartate Receptor to Inhibition by Ethanol Is Modulated by Striatal-Enriched Protein Tyrosine Phosphatase and p38 Mitogen-Activated Protein Kinase

PubMed Central

Coultrap, Steven J.; Browning, Michael D.; Proctor, William R.

2011-01-01

The hippocampal N-methyl-d-aspartate receptor (NMDAR) activity plays important roles in cognition and is a major substrate for ethanol-induced memory dysfunction. This receptor is a glutamate-gated ion channel, which is composed of NR1 and NR2 subunits in various brain areas. Although homomeric NR1 subunits form an active ion channel that conducts Na+ and Ca2+ currents, the incorporation of NR2 subunits allows this channel to be modulated by the Src family of kinases, phosphatases, and by simple molecules such as ethanol. We have found that short-term ethanol application inhibits the NMDAR activity via striatal enriched protein tyrosine phosphatase (STEP)-regulated mechanisms. The genetic deletion of the active form of STEP, STEP61, leads to marked attenuation of ethanol inhibition of NMDAR currents. In addition, STEP61 negatively regulates Fyn and p38 mitogen-activated protein kinase (MAPK), and these proteins are members of the NMDAR super molecular complex. Here we demonstrate, using whole-cell electrophysiological recording, Western blot analysis, and pharmacological manipulations, that neurons exposed to a 3-h, 45 mM ethanol treatment develop an adaptive attenuation of short-term ethanol inhibition of NMDAR currents in brain slices. Our results suggest that this adaptation of NMDAR responses is associated with a partial inactivation of STEP61, an activation of p38 MAPK, and a requirement for NR2B activity. Together, these data indicate that altered STEP61 and p38 MAPK signaling contribute to the modulation of ethanol inhibition of NMDARs in brain neurons. PMID:21680777

NR2A- and NR2B-Containing NMDA Receptors in the Prelimbic Medial Prefrontal Cortex Differentially Mediate Trace, Delay, and Contextual Fear Conditioning

ERIC Educational Resources Information Center

Gilmartin, Marieke R.; Kwapis, Janine L.; Helmstetter, Fred J.

2013-01-01

Activation of "N"-methyl-D-aspartate receptors (NMDAR) in the prelimbic medial prefrontal cortex (PL mPFC) is necessary for the acquisition of both trace and contextual fear memories, but it is not known how specific NR2 subunits support each association. The NR2B subunit confers unique properties to the NMDAR and may differentially…

Combining galantamine and memantine in multitargeted, new chemical entities potentially useful in Alzheimer's disease.

PubMed

Simoni, Elena; Daniele, Simona; Bottegoni, Giovanni; Pizzirani, Daniela; Trincavelli, Maria L; Goldoni, Luca; Tarozzo, Glauco; Reggiani, Angelo; Martini, Claudia; Piomelli, Daniele; Melchiorre, Carlo; Rosini, Michela; Cavalli, Andrea

2012-11-26

Herein we report on a novel series of multitargeted compounds obtained by linking together galantamine and memantine. The compounds were designed by taking advantage of the crystal structures of acetylcholinesterase (AChE) in complex with galantamine derivatives. Sixteen novel derivatives were synthesized, using spacers of different lengths and chemical composition. The molecules were then tested as inhibitors of AChE and as binders of the N-methyl-d-aspartate (NMDA) receptor (NMDAR). Some of the new compounds were nanomolar inhibitors of AChE and showed micromolar affinities for NMDAR. All compounds were also tested for selectivity toward NMDAR containing the 2B subunit (NR2B). Some of the new derivatives showed a micromolar affinity for NR2B. Finally, selected compounds were tested using a cell-based assay to measure their neuroprotective activity. Three of them showed a remarkable neuroprotective profile, inhibiting the NMDA-induced neurotoxicity at subnanomolar concentrations (e.g., 5, named memagal, IC(50) = 0.28 nM).

NMDA receptor dysfunction in autism spectrum disorders.

PubMed

Lee, Eun-Jae; Choi, Su Yeon; Kim, Eunjoon

2015-02-01

Abnormalities and imbalances in neuronal excitatory and inhibitory synapses have been implicated in diverse neuropsychiatric disorders including autism spectrum disorders (ASDs). Increasing evidence indicates that dysfunction of NMDA receptors (NMDARs) at excitatory synapses is associated with ASDs. In support of this, human ASD-associated genetic variations are found in genes encoding NMDAR subunits. Pharmacological enhancement or suppression of NMDAR function ameliorates ASD symptoms in humans. Animal models of ASD display bidirectional NMDAR dysfunction, and correcting this deficit rescues ASD-like behaviors. These findings suggest that deviation of NMDAR function in either direction contributes to the development of ASDs, and that correcting NMDAR dysfunction has therapeutic potential for ASDs. Copyright © 2014 Elsevier Ltd. All rights reserved.

Role of Fyn-mediated NMDA receptor function in prediabetic neuropathy in mice

PubMed Central

Suo, Meng; Wang, Ping

2016-01-01

Diabetic neuropathy is a common complication of diabetes. This study evaluated the role of Fyn kinase and N-methyl-d-aspartate receptors (NMDARs) in the spinal cord in diabetic neuropathy using an animal model of high-fat diet-induced prediabetes. We found that prediabetic wild-type mice exhibited tactile allodynia and thermal hypoalgesia after a 16-wk high-fat diet, relative to normal diet-fed wild-type mice. Furthermore, prediabetic wild-type mice exhibited increased tactile allodynia and thermal hypoalgesia at 24 wk relative to 16 wk. Such phenomena were correlated with increased expression and activation of NR2B subunit of NMDARs, as well as Fyn-NR2B interaction in the spinal cord. Fyn−/− mice developed prediabetes after 16-wk high-fat diet treatment and exhibited thermal hypoalgesia, without showing tactile allodynia or altered expression and activation of NR2B subunit, relative to normal diet-fed Fyn−/− mice. Finally, intrathecal administrations of Ro 25-6981 (selective NR2B subunit-containing NMDAR antagonist) dose-dependently alleviated tactile allodynia, but not thermal hypoalgesia, at 16 and 24 wk in prediabetic wild-type mice. Our results suggested that Fyn-mediated NR2B signaling plays a critical role in regulation of prediabetic neuropathy and that the increased expression/function of NR2B subunit-containing NMDARs may contribute to the progression of neuropathy in type 2 diabetes. PMID:27146985

Fractionating spatial memory with glutamate receptor subunit-knockout mice.

PubMed

Bannerman, David M

2009-12-01

In recent years, the contribution that different glutamate receptor subtypes and subunits make to spatial learning and memory has been studied extensively using genetically modified mice in which key proteins are knocked out. This has revealed dissociations between different aspects of spatial memory that were not previously apparent from lesion studies. For example, studies with GluA1 AMPAR [AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) receptor] subunit-knockout mice have revealed the presence of a GluA1-dependent, non-associative short-term memory mechanism that is important for performance on spatial working memory tasks, and a GluA1-independent, long-term associative memory mechanism which underlies performance on spatial reference memory tasks. Within this framework we have also studied the contributions of different GluN2-containing NMDARs [NMDA (N-methyl-D-aspartate) receptors] to spatial memory. Studies with GluN2 NMDAR mutants have revealed different contributions from GluN2A- and GluN2B-containing NMDARs to spatial learning. Furthermore, comparison of forebrain- and hippocampus-specific GluN2B-knockout mice has demonstrated that both hippocampal and extra-hippocampal NMDARs make important contributions to spatial memory performance.

Behavioral Deficits and Subregion-Specific Suppression of LTP in Mice Expressing a Population of Mutant NMDA Receptors throughout the Hippocampus

ERIC Educational Resources Information Center

Chen, Philip E.; Errington, Michael L.; Kneussel, Matthias; Chen, Guiquan; Annala, Alexander J.; Rudhard, York H.; Rast, Georg F.; Specht, Christian G.; Tigaret, Cezar M.; Nassar, Mohammed A.; Morris, Richard G.M.; Bliss, Timothy V. P.; Schoepfer, Ralf

2009-01-01

The NMDA receptor (NMDAR) subunit GluN1 is an obligatory component of NMDARs without a known functional homolog and is expressed in almost every neuronal cell type. The NMDAR system is a coincidence detector with critical roles in spatial learning and synaptic plasticity. Its coincidence detection property is crucial for the induction of…

NR2B-containing NMDA receptors promote neural progenitor cell proliferation through CaMKIV/CREB pathway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Mei, E-mail: limeihit@163.com; Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing; Zhang, Dong-Qing

2011-08-12

Highlights: {yields} The NR2B component of the NMDARs is important for the NSPC proliferation. {yields} pCaMKIV and pCREB exist in NSPCs. {yields} The CaMKIV/CREB pathway mediates NSPC proliferation. -- Abstract: Accumulating evidence indicates the involvement of N-methyl-D-aspartate receptors (NMDARs) in regulating neural stem/progenitor cell (NSPC) proliferation. Functional properties of NMDARs can be markedly influenced by incorporating the regulatory subunit NR2B. Here, we aim to analyze the effect of NR2B-containing NMDARs on the proliferation of hippocampal NSPCs and to explore the mechanism responsible for this effect. NSPCs were shown to express NMDAR subunits NR1 and NR2B. The NR2B selective antagonist, Romore » 25-6981, prevented the NMDA-induced increase in cell proliferation. Moreover, we demonstrated that the phosphorylation levels of calcium/calmodulin-dependent protein kinase IV (CaMKIV) and cAMP response element binding protein (CREB) were increased by NMDA treatment, whereas Ro 25-6981 decreased them. The role that NR2B-containing NMDARs plays in NSPC proliferation was abolished when CREB phosphorylation was attenuated by CaMKIV silencing. These results suggest that NR2B-containing NMDARs have a positive role in regulating NSPC proliferation, which may be mediated through CaMKIV phosphorylation and subsequent induction of CREB activation.« less

Reciprocal and activity-dependent regulation of surface AMPA and NMDA receptors in cultured neurons

PubMed Central

Li, Guo Hua; Jackson, Michael F; Orser, Beverley A; MacDonald, John F

2010-01-01

Activation of NMDA receptors (NMDARs) can modulate excitatory synaptic transmission in the central nervous system by dynamically altering the number of synaptic AMPA receptors (AMPARs). The surface expression of NMDARs themselves is also subject to modulation in an activity-dependent manner. In addition to NMDAR-induced changes in AMPAR expression, AMPARs have also been found to regulate their own surface expression, independently of NMDARs. However, whether or not AMPARs and NMDARs might reciprocally regulate their surface expression has not previously been systematically explored. We utilized surface biotinylation assays and stimulation protocols intended to selectively stimulate various glutamate receptor subpopulations (e.g. AMPARs vs NMDARs; synaptic vs extrasynaptic). We reveal that activation of synaptic NMDARs increases the surface expression of both NMDAR and AMPAR subunits, while activation of extrasynaptic NMDAR produces the opposite effect. Surprisingly, we find that selective activation of AMPARs reduces the surface expression of not only AMPARs but also of NMDARs. These results suggest that both AMPARs and NMDARs at synaptic sites are subject to modulation by multiple signalling pathways in an activity-dependent way. PMID:21383896

NMDA-Type Glutamate Receptor Activation Promotes Vascular Remodeling and Pulmonary Arterial Hypertension.

PubMed

Dumas, Sébastien J; Bru-Mercier, Gilles; Courboulin, Audrey; Quatredeniers, Marceau; Rücker-Martin, Catherine; Antigny, Fabrice; Nakhleh, Morad K; Ranchoux, Benoit; Gouadon, Elodie; Vinhas, Maria-Candida; Vocelle, Matthieu; Raymond, Nicolas; Dorfmüller, Peter; Fadel, Elie; Perros, Frédéric; Humbert, Marc; Cohen-Kaminsky, Sylvia

2018-05-29

Excessive proliferation and apoptosis resistance in pulmonary vascular cells underlie vascular remodeling in pulmonary arterial hypertension (PAH). Specific treatments for PAH exist, mostly targeting endothelial dysfunction, but high pulmonary arterial pressure still causes heart failure and death. Pulmonary vascular remodeling may be driven by metabolic reprogramming of vascular cells to increase glutaminolysis and glutamate production. The N -methyl-d-aspartate receptor (NMDAR), a major neuronal glutamate receptor, is also expressed on vascular cells, but its role in PAH is unknown. We assessed the status of the glutamate-NMDAR axis in the pulmonary arteries of patients with PAH and controls through mass spectrometry imaging, Western blotting, and immunohistochemistry. We measured the glutamate release from cultured pulmonary vascular cells using enzymatic assays and analyzed NMDAR regulation/phosphorylation through Western blot experiments. The effect of NMDAR blockade on human pulmonary arterial smooth muscle cell proliferation was determined using a BrdU incorporation assay. We assessed the role of NMDARs in vascular remodeling associated to pulmonary hypertension, in both smooth muscle-specific NMDAR knockout mice exposed to chronic hypoxia and the monocrotaline rat model of pulmonary hypertension using NMDAR blockers. We report glutamate accumulation, upregulation of the NMDAR, and NMDAR engagement reflected by increases in GluN1-subunit phosphorylation in the pulmonary arteries of human patients with PAH. K v channel inhibition and type A-selective endothelin receptor activation amplified calcium-dependent glutamate release from human pulmonary arterial smooth muscle cell, and type A-selective endothelin receptor and platelet-derived growth factor receptor activation led to NMDAR engagement, highlighting crosstalk between the glutamate-NMDAR axis and major PAH-associated pathways. The platelet-derived growth factor-BB-induced proliferation of human pulmonary arterial smooth muscle cells involved NMDAR activation and phosphorylated GluN1 subunit localization to cell-cell contacts, consistent with glutamatergic communication between proliferating human pulmonary arterial smooth muscle cells via NMDARs. Smooth-muscle NMDAR deficiency in mice attenuated the vascular remodeling triggered by chronic hypoxia, highlighting the role of vascular NMDARs in pulmonary hypertension. Pharmacological NMDAR blockade in the monocrotaline rat model of pulmonary hypertension had beneficial effects on cardiac and vascular remodeling, decreasing endothelial dysfunction, cell proliferation, and apoptosis resistance while disrupting the glutamate-NMDAR pathway in pulmonary arteries. These results reveal a dysregulation of the glutamate-NMDAR axis in the pulmonary arteries of patients with PAH and identify vascular NMDARs as targets for antiremodeling treatments in PAH. © 2018 American Heart Association, Inc.

Do Mice Habituate to “Gentle Handling?” A Comparison of Resting Behavior, Corticosterone Levels and Synaptic Function in Handled and Undisturbed C57BL/6J Mice

PubMed Central

Longordo, Fabio; Fan, Jing; Steimer, Thierry; Kopp, Caroline; Lüthi, Anita

2011-01-01

Study Objectives: “Gentle handling” has become a method of choice for 4-6 h sleep deprivation in mice, with repeated brief handling applied before sleep deprivation to induce habituation. To verify whether mice do indeed habituate, we assess how 6 days of repeated brief handling impact on resting behavior, on stress, and on the subunit content of N-methyl-D-aspartate receptors (NMDARs) at hippocampal synapses, which is altered by sleep loss. We discuss whether repeated handling biases the outcome of subsequent sleep deprivation. Design: Adult C57BL/6J mice, maintained on a 12 h-12 h light-dark cycle, were left undisturbed for 3 days, then handled during 3 min daily for 6 days in the middle of the light phase. Mice were continuously monitored for their resting time. Serum corticosterone levels and synaptic NMDAR subunit composition were quantified. Results: Handling caused a ∼25% reduction of resting time throughout all handling days. After six, but not after one day of handling, mice had elevated serum corticosterone levels. Six-day handling augmented the presence of the NR2A subunit of NMDARs at hippocampal synapses. Conclusion: Repeated handling induces behavioral and neurochemical alterations that are absent in undisturbed animals. The persistently reduced resting time and the delayed increase in corticosterone levels indicate that mice do not habituate to handling over a 1-week period. Handling-induced modifications bias effects of gentle handling-induced sleep deprivation on sleep homeostasis, stress, glutamate receptor composition and signaling. A standardization of sleep deprivation procedures involving gentle handling will be important for unequivocally specifying how acute sleep loss affects brain function. Citation: Longordo F; Fan J; Steimer T; Kopp C; Lüthi A. Do mice habituate to “gentle handling?” A comparison of resting behavior, corticosterone levels and synaptic function in handled and undisturbed C57BL/6J mice. SLEEP 2011;34(5):679-681. PMID:21532962

Phylogenetic analysis of ionotropic L-glutamate receptor genes in the Bilateria, with special notes on Aplysia californica.

PubMed

Greer, Justin B; Khuri, Sawsan; Fieber, Lynne A

2017-01-11

The neurotransmitter L-Glutamate (L-Glu) acting at ionotropic L-Glu receptors (iGluR) conveys fast excitatory signal transmission in the nervous systems of all animals. iGluR-dependent neurotransmission is a key component of the synaptic plasticity that underlies learning and memory. During learning, two subtypes of iGluR, α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPAR) and N-methyl-D-aspartate receptors (NMDAR), are dynamically regulated postsynaptically in vertebrates. Invertebrate organisms such as Aplysia californica (Aplysia) are well-studied models for iGluR-mediated function, yet no studies to date have analyzed the evolutionary relationships between iGluR genes in these species and those in vertebrates, to identify genes that may mediate plasticity. We conducted a thorough phylogenetic analysis spanning Bilateria to elucidate these relationships. The expression status of iGluR genes in the Aplysia nervous system was also examined. Our analysis shows that ancestral genes for both NMDAR and AMPAR subtypes were present in the common bilaterian ancestor. NMDAR genes show very high conservation in motifs responsible for forming the conductance pore of the ion channel. The number of NMDAR subunits is greater in vertebrates due to an increased number of splice variants and an increased number of genes, likely due to gene duplication events. AMPAR subunits form an orthologous group, and there is high variability in the number of AMPAR genes in each species due to extensive taxon specific gene gain and loss. qPCR results show that all 12 Aplysia iGluR subunits are expressed in all nervous system ganglia. Orthologous NMDAR subunits in all species studied suggests conserved function across Bilateria, and potentially a conserved mechanism of neuroplasticity and learning. Vertebrates display an increased number of NMDAR genes and splice variants, which may play a role in their greater diversity of physiological responses. Extensive gene gain and loss of AMPAR genes may result in different physiological properties that are taxon specific. Our results suggest a significant role for L-Glu mediated responses throughout the Aplysia nervous system, consistent with L-Glu's role as the primary excitatory neurotransmitter.

Cortical afferents onto the nucleus Reticularis thalami promote plasticity of low-threshold excitability through GluN2C-NMDARs.

PubMed

Fernandez, Laura M J; Pellegrini, Chiara; Vantomme, Gil; Béard, Elidie; Lüthi, Anita; Astori, Simone

2017-09-25

Thalamus and cortex represent a highly integrated processing unit that elaborates sensory representations. Interposed between cortex and thalamus, the nucleus Reticularis thalami (nRt) receives strong cortical glutamatergic input and mediates top-down inhibitory feedback to thalamus. Despite growing appreciation that the nRt is integral for thalamocortical functions from sleep to attentional wakefulness, we still face considerable gaps in the synaptic bases for cortico-nRt communication and plastic regulation. Here, we examined modulation of nRt excitability by cortical synaptic drive in Ntsr1-Cre x ChR2 tg/+ mice expressing Channelrhodopsin2 in layer 6 corticothalamic cells. We found that cortico-nRt synapses express a major portion of NMDA receptors containing the GluN2C subunit (GluN2C-NMDARs). Upon repetitive photoactivation (10 Hz trains), GluN2C-NMDARs induced a long-term increase in nRt excitability involving a potentiated recruitment of T-type Ca 2+ channels. In anaesthetized mice, analogous stimulation of cortical afferents onto nRt produced long-lasting changes in cortical local field potentials (LFPs), with delta oscillations being augmented at the expense of slow oscillations. This shift in LFP spectral composition was sensitive to NMDAR blockade in the nRt. Our data reveal a novel mechanism involving plastic modification of synaptically recruited T-type Ca 2+ channels and nRt bursting and indicate a critical role for GluN2C-NMDARs in thalamocortical rhythmogenesis.

Activity-induced synaptic delivery of the GluN2A-containing NMDA receptor is dependent on endoplasmic reticulum chaperone Bip and involved in fear memory

PubMed Central

Zhang, Xiao-min; Yan, Xun-yi; Zhang, Bin; Yang, Qian; Ye, Mao; Cao, Wei; Qiang, Wen-bin; Zhu, Li-jun; Du, Yong-lan; Xu, Xing-xing; Wang, Jia-sheng; Xu, Fei; Lu, Wei; Qiu, Shuang; Yang, Wei; Luo, Jian-hong

2015-01-01

The N-methyl-D-aspartate receptor (NMDAR) in adult forebrain is a heterotetramer mainly composed of two GluN1 subunits and two GluN2A and/or GluN2B subunits. The synaptic expression and relative numbers of GluN2A- and GluN2B-containing NMDARs play critical roles in controlling Ca2+-dependent signaling and synaptic plasticity. Previous studies have suggested that the synaptic trafficking of NMDAR subtypes is differentially regulated, but the precise molecular mechanism is not yet clear. In this study, we demonstrated that Bip, an endoplasmic reticulum (ER) chaperone, selectively interacted with GluN2A and mediated the neuronal activity-induced assembly and synaptic incorporation of the GluN2A-containing NMDAR from dendritic ER. Furthermore, the GluN2A-specific synaptic trafficking was effectively disrupted by peptides interrupting the interaction between Bip and GluN2A. Interestingly, fear conditioning in mice was disrupted by intraperitoneal injection of the interfering peptide before training. In summary, we have uncovered a novel mechanism for the activity-dependent supply of synaptic GluN2A-containing NMDARs, and demonstrated its relevance to memory formation. PMID:26088419

A Rare Variant Identified Within the GluN2B C-Terminus in a Patient with Autism Affects NMDA Receptor Surface Expression and Spine Density.

PubMed

Liu, Shuxi; Zhou, Liang; Yuan, Hongjie; Vieira, Marta; Sanz-Clemente, Antonio; Badger, John D; Lu, Wei; Traynelis, Stephen F; Roche, Katherine W

2017-04-12

NMDA receptors (NMDARs) are ionotropic glutamate receptors that are crucial for neuronal development and higher cognitive processes. NMDAR dysfunction is involved in a variety of neurological and psychiatric diseases; however, the mechanistic link between the human pathology and NMDAR dysfunction is poorly understood. Rare missense variants within NMDAR subunits have been identified in numerous patients with mental or neurological disorders. We specifically focused on the GluN2B NMDAR subunit, which is highly expressed in the hippocampus and cortex throughout development. We analyzed several variants located in the GluN2B C terminus and found that three variants in patients with autism (S1415L) or schizophrenia (L1424F and S1452F) (S1413L, L1422F, and S1450F in rodents, respectively) displayed impaired binding to membrane-associated guanylate kinase (MAGUK) proteins. In addition, we observed a deficit in surface expression for GluN2B S1413L. Furthermore, there were fewer dendritic spines in GluN2B S1413L-expressing neurons. Importantly, synaptic NMDAR currents in neurons transfected with GluN2B S1413L in GluN2A/B-deficient mouse brain slices revealed only partial rescue of synaptic current amplitude. Functional properties of GluN2B S1413L in recombinant systems revealed no change in receptor properties, consistent with synaptic defects being the result of reduced trafficking and targeting of GluN2B S1413L to the synapse. Therefore, we find that GluN2B S1413L displays deficits in NMDAR trafficking, synaptic currents, and spine density, raising the possibility that this mutation may contribute to the phenotype in this autism patient. More broadly, our research demonstrates that the targeted study of certain residues in NMDARs based on rare variants identified in patients is a powerful approach to studying receptor function. SIGNIFICANCE STATEMENT We have used a "bedside-to-bench" approach to investigate the functional regulation of NMDA receptors (NMDARs). Using information from deep sequencing of patients with neurological or psychiatric disorders, we investigated missense variants identified in the intracellular C-terminal domain of the GluN2B NMDAR subunit. We found several variants that displayed altered properties. In particular, one variant identified in a patient with autism, human GluN2B S1415L, displayed reduced surface expression and binding to PSD-95. Furthermore expression of GluN2B S1415L (S1413L in mouse) showed a deficit in rescue of synaptic NMDAR currents and fewer dendritic spines, consistent with other reports of spine abnormalities being associated with autism. More broadly, we demonstrate that using patient data is an effective approach to probing the structure/function relationship of NMDARs. Copyright © 2017 the authors 0270-6474/17/374094-10$15.00/0.

Separate functional properties of NMDARs regulate distinct aspects of spatial cognition.

PubMed

Sanders, Erin M; Nyarko-Odoom, Akua O; Zhao, Kevin; Nguyen, Michael; Liao, Hong Hong; Keith, Matthew; Pyon, Jane; Kozma, Alyssa; Sanyal, Mohima; McHail, Daniel G; Dumas, Theodore C

2018-06-01

N -methyl-d-aspartate receptors (NMDARs) at excitatory synapses are central to activity-dependent synaptic plasticity and learning and memory. NMDARs act as ionotropic and metabotropic receptors by elevating postsynaptic calcium concentrations and by direct intracellular protein signaling. In the forebrain, these properties are controlled largely by the auxiliary GluN2 subunits, GluN2A and GluN2B. While calcium conductance through NMDAR channels and intracellular protein signaling make separate contributions to synaptic plasticity, it is not known if these properties individually influence learning and memory. To address this issue, we created chimeric GluN2 subunits containing the amino-terminal domain and transmembrane domains from GluN2A or GluN2B fused to the carboxy-terminal domain of GluN2B (termed ABc) or GluN2A ATD (termed BAc), respectively, and expressed these mutated GluN2 subunits in transgenic mice. Expression was confirmed at the mRNA level and protein subunit translation and translocation into dendrites were observed in forebrain neurons. In the spatial version of the Morris water maze, BAc mice displayed signs of a learning deficit. In contrast, ABc animals performed similarly to wild-types during training, but showed a more direct approach to the goal location during a long-term memory test. There was no effect of ABc or BAc expression in a nonspatial water escape task. Since background expression is predominantly GluN2A in mature animals, the results suggest that spatial learning is more sensitive to manipulations of the amino-terminal domain and transmembrane domains (calcium conductance) and long-term memory is regulated more by the carboxy-terminal domain (intracellular protein signaling). © 2018 Sanders et al.; Published by Cold Spring Harbor Laboratory Press.

Abeta oligomers induce neuronal oxidative stress through an N-methyl-D-aspartate receptor-dependent mechanism that is blocked by the Alzheimer drug memantine.

PubMed

De Felice, Fernanda G; Velasco, Pauline T; Lambert, Mary P; Viola, Kirsten; Fernandez, Sara J; Ferreira, Sergio T; Klein, William L

2007-04-13

Oxidative stress is a major aspect of Alzheimer disease (AD) pathology. We have investigated the relationship between oxidative stress and neuronal binding of Abeta oligomers (also known as ADDLs). ADDLs are known to accumulate in brain tissue of AD patients and are considered centrally related to pathogenesis. Using hippocampal neuronal cultures, we found that ADDLs stimulated excessive formation of reactive oxygen species (ROS) through a mechanism requiring N-methyl-d-aspartate receptor (NMDA-R) activation. ADDL binding to neurons was reduced and ROS formation was completely blocked by an antibody to the extracellular domain of the NR1 subunit of NMDA-Rs. In harmony with a steric inhibition of ADDL binding by NR1 antibodies, ADDLs that were bound to detergent-extracted synaptosomal membranes co-immunoprecipitated with NMDA-R subunits. The NR1 antibody did not affect ROS formation induced by NMDA, showing that NMDA-Rs themselves remained functional. Memantine, an open channel NMDA-R antagonist prescribed as a memory-preserving drug for AD patients, completely protected against ADDL-induced ROS formation, as did other NMDA-R antagonists. Memantine and the anti-NR1 antibody also attenuated a rapid ADDL-induced increase in intraneuronal calcium, which was essential for stimulated ROS formation. These results show that ADDLs bind to or in close proximity to NMDA-Rs, triggering neuronal damage through NMDA-R-dependent calcium flux. This response provides a pathologically specific mechanism for the therapeutic action of memantine, indicates a role for ROS dysregulation in ADDL-induced cognitive impairment, and supports the unifying hypothesis that ADDLs play a central role in AD pathogenesis.

Inflammatory sensitization of nociceptors depends on activation of NMDA receptors in DRG satellite cells.

PubMed

Ferrari, Luiz Fernando; Lotufo, Celina Monteiro; Araldi, Dionéia; Rodrigues, Marcos A; Macedo, Larissa P; Ferreira, Sérgio H; Parada, Carlos Amilcar

2014-12-23

The present study evaluated the role of N-methyl-D-aspartate receptors (NMDARs) expressed in the dorsal root ganglia (DRG) in the inflammatory sensitization of peripheral nociceptor terminals to mechanical stimulation. Injection of NMDA into the fifth lumbar (L5)-DRG induced hyperalgesia in the rat hind paw with a profile similar to that of intraplantar injection of prostaglandin E2 (PGE2), which was significantly attenuated by injection of the NMDAR antagonist D(-)-2-amino-5-phosphonopentanoic acid (D-AP-5) in the L5-DRG. Moreover, blockade of DRG AMPA receptors by the antagonist 6,7-dinitroquinoxaline-2,3-dione had no effect in the PGE2-induced hyperalgesia in the paw, showing specific involvement of NMDARs in this modulatory effect and suggesting that activation of NMDAR in the DRG plays an important role in the peripheral inflammatory hyperalgesia. In following experiments we observed attenuation of PGE2-induced hyperalgesia in the paw by the knockdown of NMDAR subunits NR1, NR2B, NR2D, and NR3A with antisense-oligodeoxynucleotide treatment in the DRG. Also, in vitro experiments showed that the NMDA-induced sensitization of cultured DRG neurons depends on satellite cell activation and on those same NMDAR subunits, suggesting their importance for the PGE2-induced hyperalgesia. In addition, fluorescent calcium imaging experiments in cultures of DRG cells showed induction of calcium transients by glutamate or NMDA only in satellite cells, but not in neurons. Together, the present results suggest that the mechanical inflammatory nociceptor sensitization is dependent on glutamate release at the DRG and subsequent NMDAR activation in satellite glial cells, supporting the idea that the peripheral hyperalgesia is an event modulated by a glutamatergic system in the DRG.

Dynorphin up-regulation in the dentate granule cell mossy fiber pathway following chronic inhibition of GluN2B-containing NMDAR is associated with increased CREB (Ser 133) phosphorylation, but is independent of BDNF/TrkB signaling pathways.

PubMed

Rittase, W Bradley; Dong, Yu; Barksdale, DaRel; Galdzicki, Zygmunt; Bausch, Suzanne B

2014-05-01

Emerging evidence suggests that neuronal responses to N-methyl-d-aspartate (NMDAR) activation/inactivation are influenced by subunit composition. For example, activation of synaptic NMDAR (comprised of GluN2A>GluN2B) phosphorylates cAMP-response-element-binding protein (CREB) at Ser 133, induces BDNF expression and promotes neuronal survival. Activation of extrasynaptic NMDAR (comprised of GluN2B>GluN2) dephosphorylates CREB (Ser 133), reduces BDNF expression and triggers neuronal death. These results led us to hypothesize that chronic inhibition of GluN2B-containing NMDAR would increase CREB (Ser 133) phosphorylation, increase BDNF levels and subsequently alter downstream dynorphin (DYN) and neuropeptide Y (NPY) expression. We focused on DYN and NPY because these neuropeptides can decrease excitatory neurotransmission and seizure occurrence and we reported previously that seizure-like events are reduced following chronic treatment with GluN2B antagonists. Consistent with our hypothesis, chronic treatment (17-21days) of hippocampal slice cultures with the GluN2B-selective antagonists ifenprodil or Ro25,6981 increased both CREB (Ser 133) phosphorylation and granule cell mossy fiber pathway DYN expression. Similar treatment with the non-subtype-selective NMDAR antagonists d-APV or memantine had no significant effect on either CREB (Ser 133) phosphorylation or DYN expression. In contrast to our hypothesis, BDNF levels were decreased following chronic treatment with Ro25,6981, but not ifenprodil, d-APV or memantine. Blockade of BDNF actions and TrkB activation did not significantly augment hilar DYN expression in vehicle-treated cultures and had no effect in Ro25,6981 treated cultures. These findings suggest that chronic exposure to GluN2B-selective NMDAR antagonists increased DYN expression through a putatively pCREB-dependent, but BDNF/TrkB-independent mechanism. Published by Elsevier Inc.

Biochemical principles underlying the stable maintenance of LTP by the CaMKII/NMDAR complex.

PubMed

Lisman, John; Raghavachari, Sridhar

2015-09-24

Memory involves the storage of information at synapses by an LTP-like process. This information storage is synapse specific and can endure for years despite the turnover of all synaptic proteins. There must, therefore, be special principles that underlie the stability of LTP. Recent experimental results suggest that LTP is maintained by the complex of CaMKII with the NMDAR. Here we consider the specifics of the CaMKII/NMDAR molecular switch, with the goal of understanding the biochemical principles that underlie stable information storage by synapses. Consideration of a variety of experimental results suggests that multiple principles are involved. One switch requirement is to prevent spontaneous transitions from the off to the on state. The highly cooperative nature of CaMKII autophosphorylation by Ca(2+) (Hill coefficient of 8) and the fact that formation of the CaMKII/NMDAR complex requires release of CaMKII from actin are mechanisms that stabilize the off state. The stability of the on state depends critically on intersubunit autophosphorylation, a process that restores any loss of pT286 due to phosphatase activity. Intersubunit autophosphorylation is also important in explaining why on state stability is not compromised by protein turnover. Recent evidence suggests that turnover occurs by subunit exchange. Thus, stability could be achieved if a newly inserted unphosphorylated subunit was autophosphorylated by a neighboring subunit. Based on other recent work, we posit a novel mechanism that enhances the stability of the on state by protection of pT286 from phosphatases. We posit that the binding of the NMNDAR to CaMKII forces pT286 into the catalytic site of a neighboring subunit, thereby protecting pT286 from phosphatases. A final principle concerns the role of structural changes. The binding of CaMKII to the NMDAR may act as a tag to organize the binding of further proteins that produce the synapse enlargement that underlies late LTP. We argue that these structural changes not only enhance transmission, but also enhance the stability of the CaMKII/NMDAR complex. Together, these principles provide a mechanistic framework for understanding how individual synapses produce stable information storage. This article is part of a Special Issue entitled SI: Brain and Memory. Copyright © 2014 Elsevier B.V. All rights reserved.

Rett-like Severe Encephalopathy Caused by a De Novo GRIN2B Mutation Is Attenuated by D-serine Dietary Supplement.

PubMed

Soto, David; Olivella, Mireia; Grau, Cristina; Armstrong, Judith; Alcon, Clara; Gasull, Xavier; Gómez de Salazar, Macarena; Gratacòs-Batlle, Esther; Ramos-Vicente, David; Fernández-Dueñas, Víctor; Ciruela, Francisco; Bayés, Àlex; Sindreu, Carlos; López-Sala, Anna; García-Cazorla, Àngels; Altafaj, Xavier

2018-01-15

N-Methyl-D-aspartate receptors (NMDARs) play pivotal roles in synaptic development, plasticity, neural survival, and cognition. Despite recent reports describing the genetic association between de novo mutations of NMDAR subunits and severe psychiatric diseases, little is known about their pathogenic mechanisms and potential therapeutic interventions. Here we report a case study of a 4-year-old Rett-like patient with severe encephalopathy carrying a missense de novo mutation in GRIN2B(p.P553T) coding for the GluN2B subunit of NMDAR. We generated a dynamic molecular model of mutant GluN2B-containing NMDARs. We expressed the mutation in cell lines and primary cultures, and we evaluated the putative morphological, electrophysiological, and synaptic plasticity alterations. Finally, we evaluated D-serine administration as a therapeutic strategy and translated it to the clinical practice. Structural molecular modeling predicted a reduced pore size of mutant NMDARs. Electrophysiological recordings confirmed this prediction and also showed gating alterations, a reduced glutamate affinity associated with a strong decrease of NMDA-evoked currents. Moreover, GluN2B(P553T)-expressing neurons showed decreased spine density, concomitant with reduced NMDA-evoked currents and impaired NMDAR-dependent insertion of GluA1 at stimulated synapses. Notably, the naturally occurring coagonist D-serine was able to attenuate hypofunction of GluN2B(p.P553T)-containing NMDARs. Hence, D-serine dietary supplementation was initiated. Importantly, the patient has shown remarkable motor, cognitive, and communication improvements after 17 months of D-serine dietary supplementation. Our data suggest that hypofunctional NMDARs containing GluN2B(p.P553T) can contribute to Rett-like encephalopathy and that their potentiation by D-serine treatment may underlie the associated clinical improvement. Copyright © 2017 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

SRC Inhibition Reduces NR2B Surface Expression and Synaptic Plasticity in the Amygdala

ERIC Educational Resources Information Center

Sinai, Laleh; Duffy, Steven; Roder, John C.

2010-01-01

The Src protein tyrosine kinase plays a central role in the regulation of N-methyl-d-aspartate receptor (NMDAR) activity by regulating NMDAR subunit 2B (NR2B) surface expression. In the amygdala, NMDA-dependent synaptic plasticity resulting from convergent somatosensory and auditory inputs contributes to emotional memory; however, the role of Src…

NMDA receptor GluN2A subunit deletion protects against dependence-like ethanol drinking.

PubMed

Jury, Nicholas J; Radke, Anna K; Pati, Dipanwita; Kocharian, Adrina; Mishina, Masayoshi; Kash, Thomas L; Holmes, Andrew

2018-06-25

The N-methyl- D -aspartate receptor (NMDAR) is mechanistically involved in the behavioral and neurophysiological effects of alcohol, but the specific role of the GluN2A subunit remains unclear. Here, we exposed mice with constitutive GluN2A gene knockout (KO) to chronic intermittent ethanol vapor (CIE) and tested for EtOH consumption/preference using a two-bottle choice paradigm, as well as NMDAR-mediated transmission at basolateral amygdala synapses via ex vivo slice electrophysiology. Results showed that GluN2A KO mice attained comparable blood EtOH levels in response to CIE exposure, but did not exhibit the significant increase in EtOH drinking that was observed in CIE-exposed wildtypes. GluN2A KO mice also showed no alterations in BLA NMDAR-mediated synaptic transmission after CIE, relative to air-exposed, whereas C57BL/6 J mice showed an attenuated synaptic response to GluN2B antagonism. Taken together, these data add to mounting evidence supporting GluN2A-containing NMDARs as a mechanism underlying relative risk for developing EtOH dependence after repeated EtOH exposure. Copyright © 2018. Published by Elsevier B.V.

Parafascicular thalamic nucleus deep brain stimulation decreases NMDA receptor GluN1 subunit gene expression in the prefrontal cortex.

PubMed

Fernández-Cabrera, Mónica R; Selvas, Abraham; Miguéns, Miguel; Higuera-Matas, Alejandro; Vale-Martínez, Anna; Ambrosio, Emilio; Martí-Nicolovius, Margarita; Guillazo-Blanch, Gemma

2017-04-21

The rodent parafascicular nucleus (PFn) or the centromedian-parafascicular complex of primates is a posterior intralaminar nucleus of the thalamus related to cortical activation and maintenance of states of consciousness underlying attention, learning and memory. Deep brain stimulation (DBS) of the PFn has been proved to restore arousal and consciousness in humans and to enhance performance in learning and memory tasks in rats. The primary expected effect of PFn DBS is to induce plastic changes in target neurons of brain areas associated with cognitive function. In this study, Wistar rats were stimulated for 20mins in the PFn following a DBS protocol that had previously facilitated memory in rats. NMDA and GABA B receptor binding, and gene expression of the GluN1subunit of the NMDA receptor (NMDAR) were assessed in regions related to cognitive functions, such as the prefrontal cortex and hippocampus. The results showed that PFn DBS induced a decrease in NMDAR GluN1 subunit gene expression in the cingulate and prelimbic cortices, but no significant statistical differences were found in the density of NMDA or GABA B receptors in any of the analyzed regions. Taken together, our findings suggest a possible role for the NMDAR GluN1 subunit in the prefrontal cortex in the procognitive actions of the PFn DBS. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

The selectivity of conantokin-G for ion channel inhibition of NR2B subunit-containing NMDA receptors is regulated by amino acid residues in the S2 region of NR2B

PubMed Central

Sheng, Zhenyu; Liang, Zhong; Geiger, James H.; Prorok, Mary; Castellino, Francis J.

2009-01-01

The conantokins are short, naturally-occurring peptides that inhibit ion flow through N-methyl-D-aspartate receptor (NMDAR) channels. One member of this peptide family, conantokin-G (con-G), specifically antagonizes NR2B-containing NMDAR channels, whereas other known conantokins are less selective inhibitors with regard to the nature of the NR2 subunit of the NMDAR complex. In order to define the molecular determinants of NR2B that govern con-G selectivity, we evaluated the ability of con-G to inhibit NMDAR ion channels expressed in human embryonic kidney (HEK)293 cells transfected with NR1, in combination with various NR2A/2B chimeras and point mutants, by electrophysiology using cells voltage-clamped in the whole cell configuration. We found that a variant of the con-G-insensitive subunit, NR2A, in which the 158 residues comprising the S2 peptide segment (E657-I814) were replaced by the corresponding S2 region of NR2B (E658-I815), results in receptors that are highly sensitive to inhibition by con-G. Of the 22 amino acids that are different between the NR2A-S2 and the NR2B-S2 regions, exchange of one of these, M739 of NR2B for the equivalent K738 of NR2A, was sufficient to completely import the inhibitory activity of con-G into NR1b/NR2A-containing NMDARs. Some reinforcement of this effect was found by substitution of a second amino acid, K755 of NR2B for Y754 of NR2A. The discovery of the molecular determinants of NR2B selectivity with con-G has implications for the design of subunit-selective neurobiological probes and drug therapies, in addition to advancing our understanding of NR2B- versus NR2A-mediated neurological processes. PMID:19427876

Ionotropic NMDA receptor signaling is required for the induction of long-term depression in the mouse hippocampal CA1 region.

PubMed

Babiec, Walter E; Guglietta, Ryan; Jami, Shekib A; Morishita, Wade; Malenka, Robert C; O'Dell, Thomas J

2014-04-09

Previous studies have provided strong support for the notion that NMDAR-mediated increases in postsynaptic Ca(2+) have a crucial role in the induction of long-term depression (LTD). This view has recently been challenged, however, by findings suggesting that LTD induction is instead attributable to an ion channel-independent, metabotropic form of NMDAR signaling. Thus, to explore the role of ionotropic versus metabotropic NMDAR signaling in LTD, we examined the effects of varying extracellular Ca(2+) levels or blocking NMDAR channel ion fluxes with MK-801 on LTD and NMDAR signaling in the mouse hippocampal CA1 region. We find that the induction of LTD in the adult hippocampus is highly sensitive to extracellular Ca(2+) levels and that MK-801 blocks NMDAR-dependent LTD in the hippocampus of both adult and immature mice. Moreover, MK-801 inhibits NMDAR-mediated activation of p38-MAPK and dephosphorylation of AMPAR GluA1 subunits at sites implicated in LTD. Thus, our results indicate that the induction of LTD in the hippocampal CA1 region is dependent on ionotropic, rather than metabotropic, NMDAR signaling.

The NR1-4 C-terminus interferes with N-methyl-D-aspartate receptor-mediated excitotoxicity: evidence against a typical T/SXV-PDZ interaction.

PubMed

Mattar, P A; Holmes, K D; Dekaban, G A

2005-01-01

The N-methyl-D-aspartate receptor (NMDAR) plays a key role in the neural plasticity that underlies learning and memory in vivo. The plasticity exhibited by NMDARs may also contribute to disease pathogenesis, as a number of disorders are caused or exacerbated by exaggerated NMDAR activity. The NMDAR is composed of two obligatory types of subunits, NR1 and NR2. These transmembrane proteins include large intracellular C-termini that have yet to be fully characterized. We have developed a three-color fluorescence system in order to visualize NMDAR expression in living cells. Using excitotoxicity as a proxy for exaggerated NMDAR activity, we analyzed the effect of over-expressing NR1-4 and NR2A C-terminal domains on exaggerated NMDAR function. We demonstrate that a determinant within the C-terminal domain of NR1-4 (C02') is important for NMDAR excitotoxicity, whereas no novel determinants were identified in the NR2A C-terminus. Through the use of heterologous cells, and by examining the interaction between the prototypical NMDAR-binding partner postsynaptic density-95 (PSD-95), we show that this effect is unlikely to be mediated through a classical interaction with PSD-95.

The NMDA receptor as a target for cognitive enhancement

PubMed Central

Collingridge, Graham L.; Volianskis, Arturas; Bannister, Neil; France, Grace; Hanna, Lydia; Mercier, Marion; Tidball, Patrick; Fang, Guangyu; Irvine, Mark W.; Costa, Blaise M.; Monaghan, Daniel T.; Bortolotto, Zuner A.; Molnár, Elek; Lodge, David; Jane, David E.

2015-01-01

NMDA receptors (NMDAR) play an important role in neural plasticity including long-term potentiation and long-term depression, which are likely to explain their importance for learning and memory. Cognitive decline is a major problem facing an ageing human population, so much so that its reversal has become an important goal for scientific research and pharmaceutical development. Enhancement of NMDAR function is a core strategy toward this goal. In this review we indicate some of the major ways of potentiating NMDAR function by both direct and indirect modulation. There is good evidence that both positive and negative modulation can enhance function suggesting that a subtle approach correcting imbalances in particular clinical situations will be required. Excessive activation and the resultant deleterious effects will need to be carefully avoided. Finally we describe some novel positive allosteric modulators of NMDARs, with some subunit selectivity, and show initial evidence of their ability to affect NMDAR mediated events. PMID:22796429

Surface expression of NMDA receptor changes during memory consolidation in the crab Neohelice granulata

PubMed Central

Hepp, Yanil; Salles, Angeles; Carbo-Tano, Martin

2016-01-01

The aim of the present study was to analyze the surface expression of the NMDA-like receptors during the consolidation of contextual learning in the crab Neohelice granulata. Memory storage is based on alterations in the strength of synaptic connections between neurons. The glutamatergic synapses undergo various forms of N-methyl-D aspartate receptor (NMDAR)-dependent changes in strength, a process that affects the abundance of other receptors at the synapse and underlies some forms of learning and memory. Here we propose a direct regulation of the NMDAR. Changes in NMDAR's functionality might be induced by the modification of the subunit's expression or cellular trafficking. This trafficking does not only include NMDAR's movement between synaptic and extra-synaptic localizations but also the cycling between intracellular compartments and the plasma membrane, a process called surface expression. Consolidation of contextual learning affects the surface expression of the receptor without affecting its general expression. The surface expression of the GluN1 subunit of the NMDAR is down-regulated immediately after training, up-regulated 3 h after training and returns to naïve and control levels 24 h after training. The changes in NMDAR surface expression observed in the central brain are not seen in the thoracic ganglion. A similar increment in surface expression of GluN1 in the central brain is observed 3 h after administration of the competitive GABAA receptor antagonist, bicuculline. These consolidation changes are part of a plasticity event that first, during the down-regulation, stabilizes the trace and later, at 3-h post-training, changes the threshold for synapse activation. PMID:27421895

Bisphenol-A rapidly enhanced passive avoidance memory and phosphorylation of NMDA receptor subunits in hippocampus of young rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu Xiaohong, E-mail: xuxh63@zjnu.cn; Li Tao; Luo Qingqing

Bisphenol-A (BPA), an endocrine disruptor, is found to influence development of brain and behaviors in rodents. The previous study indicated that perinatal exposure to BPA impaired learning-memory and inhibited N-methyl-D-aspartate receptor (NMDAR) subunits expressions in hippocampus during the postnatal development in rats; and in cultured hippocampal neurons, BPA rapidly promotes dynamic changes in dendritic morphology through estrogen receptor-mediated pathway by concomitant phosphorylation of NMDAR subunit NR2B. In the present study, we examined the rapid effect of BPA on passive avoidance memory and NMDAR in the developing hippocampus of Sprague-Dawley rats at the age of postnatal day 18. The results showedmore » that BPA or estradiol benzoate (EB) rapidly extended the latency to step down from the platform 1 h after footshock and increased the phosphorylation levels of NR1, NR2B, and mitogen-activated extracellular signal-regulated kinase (ERK) in hippocampus within 1 h. While 24 h after BPA or EB treatment, the improved memory and the increased phosphorylation levels of NR1, NR2B, ERK disappeared. Furthermore, pre-treatment with an estrogen receptors (ERs) antagonist, ICI182,780, or an ERK-activating kinase inhibitor, U0126, significantly attenuated EB- or BPA-induced phosphorylations of NR1, NR2B, and ERK within 1 h. These data suggest that BPA rapidly enhanced short-term passive avoidance memory in the developing rats. A non-genomic effect via ERs may mediate the modulation of the phosphorylation of NMDAR subunits NR1 and NR2B through ERK signaling pathway. - Highlights: > BPA rapidly extended the latency to step down from platform 1 h after footshock. > BPA rapidly increased pNR1, pNR2B, and pERK in hippocampus within 1 h. > ERs antagonist or MEK inhibitor attenuated BPA-induced pNR1, pNR2B, and pERK.« less

Time-Dependent Alterations in the Expression of NMDA Receptor Subunits along the Dorsoventral Hippocampal Axis in an Animal Model of Nascent Psychosis.

PubMed

Dubovyk, Valentyna; Manahan-Vaughan, Denise

2018-04-10

Psychosis is a mental condition that is characterized by hallucinations, delusions, disordered thought, as well as socio-emotional and cognitive impairments. Once developed, it tends to progress into a chronic psychotic illness. Here, the duration of untreated psychosis plays a crucial role: the earlier the treatment begins, relative to the first episode of the disease, the better the patient's functional prognosis. To what extent the success of early interventions relate to progressive changes at the neurotransmitter receptor level is as yet unclear. In fact, very little is known as to how molecular changes develop, transform, and become established following the first psychotic event. One neurotransmitter receptor for which a specific role in psychosis has been discussed is the N-methyl-d-aspartate receptor (NMDAR). This receptor is especially important for information encoding in the hippocampus. The hippocampus is one of the loci of functional change in psychosis, to which a role in the pathophysiology of psychosis has been ascribed. Here, we examined whether changes in NMDAR subunit expression occur along the dorsoventral axis of the hippocampus 1 week and 3 months after systemic treatment with an NMDAR antagonist (MK801) that initiates a psychosis-like state in adult rats. We found early (1 week) upregulation of the GluN2B levels in the dorso-intermediate hippocampus and late (3 month) downregulation of GluN2A expression across the entire CA1 region. The ventral hippocampus did not exhibit subunit expression changes. These data suggest that a differing vulnerability of the hippocampal longitudinal axis may occur in response to MK801-treatment and provide a time-resolved view of the putative development of pathological changes of NMDAR subunit expression in the hippocampus that initiate with an emulated first episode and progress through to the chronic stabilization of a psychosis-like state in rodents.

Uncoupling the widespread occurrence of anti-NMDAR1 autoantibodies from neuropsychiatric disease in a novel autoimmune model.

PubMed

Pan, Hong; Oliveira, Bárbara; Saher, Gesine; Dere, Ekrem; Tapken, Daniel; Mitjans, Marina; Seidel, Jan; Wesolowski, Janina; Wakhloo, Debia; Klein-Schmidt, Christina; Ronnenberg, Anja; Schwabe, Kerstin; Trippe, Ralf; Mätz-Rensing, Kerstin; Berghoff, Stefan; Al-Krinawe, Yazeed; Martens, Henrik; Begemann, Martin; Stöcker, Winfried; Kaup, Franz-Josef; Mischke, Reinhard; Boretius, Susann; Nave, Klaus-Armin; Krauss, Joachim K; Hollmann, Michael; Lühder, Fred; Ehrenreich, Hannelore

2018-02-09

Autoantibodies of the IgG class against N-methyl-D-aspartate-receptor subunit-NR1 (NMDAR1-AB) were considered pathognomonic for anti-NMDAR encephalitis. This view has been challenged by the age-dependent seroprevalence (up to >20%) of functional NMDAR1-AB of all immunoglobulin classes found in >5000 individuals, healthy or affected by different diseases. These findings question a merely encephalitogenic role of NMDAR1-AB. Here, we show that NMDAR1-AB belong to the normal autoimmune repertoire of dogs, cats, rats, mice, baboons, and rhesus macaques, and are functional in the NMDAR1 internalization assay based on human IPSC-derived cortical neurons. The age dependence of seroprevalence is lost in nonhuman primates in captivity and in human migrants, raising the intriguing possibility that chronic life stress may be related to NMDAR1-AB formation, predominantly of the IgA class. Active immunization of ApoE -/- and ApoE +/+ mice against four peptides of the extracellular NMDAR1 domain or ovalbumin (control) leads to high circulating levels of specific AB. After 4 weeks, the endogenously formed NMDAR1-AB (IgG) induce psychosis-like symptoms upon MK-801 challenge in ApoE -/- mice, characterized by an open blood-brain barrier, but not in their ApoE +/+ littermates, which are indistinguishable from ovalbumin controls. Importantly, NMDAR1-AB do not induce any sign of inflammation in the brain. Immunohistochemical staining for microglial activation markers and T lymphocytes in the hippocampus yields comparable results in ApoE -/- and ApoE +/+ mice, irrespective of immunization against NMDAR1 or ovalbumin. These data suggest that NMDAR1-AB of the IgG class shape behavioral phenotypes upon access to the brain but do not cause brain inflammation on their own.

Peripheral inflammation increased the synaptic expression of NMDA receptors in spinal dorsal horn.

PubMed

Yang, Xian; Yang, Hong-Bin; Xie, Qin-Jian; Liu, Xiao-Hua; Hu, Xiao-Dong

2009-07-01

Considerable evidence has indicated that the aberrant, sustained enhancement of spinal NMDA receptors (NMDARs) function is closely associated with behavioral sensitization during inflammatory pain. However, the molecular mechanisms underlying inflammation-induced NMDARs hyperfunction remain poorly understood. The present study performed immunoblotting analysis to evaluate the possible changes in the protein expression of spinal NMDARs after injection of complete Freund's adjuvant (CFA) in mice. We found that CFA did not affect the total protein level of NMDARs subunit NR1 in spinal dorsal horn. However, NR1 immunoreactivity at synapses significantly increased after CFA injection, which was correlated in the time course with the development of mechanical allodynia. Inhibition of spinal NMDARs with D-APV completely eliminated the CFA-induced increase in NR1 immunoreactive density at synapses, and direct application of NMDA onto the spinal cord of naïve mice mimicked the effects of CFA, suggesting the importance of NMDARs activity in regulating the synaptic content of NR1 during inflammatory pain. Moreover, cAMP-dependent protein kinase (PKA) downstream to NMDARs was also required for NR1 synaptic expression because inhibition of PKA activity abolished the enhancement of synaptic NR1 immunoreactivity evoked by either CFA or NMDA. Thus, our data suggested that NMDARs- and PKA-dependent increase in NR1 synaptic expression represented an important mechanism for the hyperfunction of spinal NMDARs following peripheral inflammation.

Impaired discrimination learning in interneuronal NMDAR-GluN2B mutant mice.

PubMed

Brigman, Jonathan L; Daut, Rachel A; Saksida, Lisa; Bussey, Timothy J; Nakazawa, Kazu; Holmes, Andrew

2015-06-17

Previous studies have established a role for N-methyl-D-aspartate receptor (NMDAR) containing the GluN2B subunit in efficient learning behavior on a variety of tasks. Recent findings have suggested that NMDAR on GABAergic interneurons may underlie the modulation of striatal function necessary to balance efficient action with cortical excitatory input. Here we investigated how loss of GluN2B-containing NMDAR on GABAergic interneurons altered corticostriatal-mediated associative learning. Mutant mice (floxed-GluN2B×Ppp1r2-Cre) were generated to produce loss of GluN2B on forebrain interneurons and phenotyped on a touchscreen-based pairwise visual learning paradigm. We found that the mutants showed normal performance during Pavlovian and instrumental pretraining, but were significantly impaired on a discrimination learning task. Detailed analysis of the microstructure of discrimination performance revealed reduced win→stay behavior in the mutants. These results further support the role of NMDAR, and GluN2B in particular, on modulation of striatal function necessary for efficient choice behavior and suggest that NMDAR on interneurons may play a critical role in associative learning.

Learning in the Absence of Experience-Dependent Regulation of NMDAR Composition

ERIC Educational Resources Information Center

Lebel, David; Sidhu, Nishchal; Barkai, Edi; Quinlan, Elizabeth M.

2006-01-01

Olfactory discrimination (OD) learning consists of two phases: an initial N-methyl-d-aspartate (NMDA) receptor--sensitive rule-learning phase, followed by an NMDA receptor (NMDAR)--insensitive pair-learning phase. The rule-learning phase is accompanied by changes in the composition and function of NMDARs at synapses in the piriform cortex,…

STEP activation by Gαq coupled GPCRs opposes Src regulation of NMDA receptors containing the GluN2A subunit

PubMed Central

Tian, Meng; Xu, Jian; Lei, Gang; Lombroso, Paul J.; Jackson, Michael F.; MacDonald, John F.

2016-01-01

N-methyl-D-aspartate receptors (NMDARs) are necessary for the induction of synaptic plasticity and for the consolidation of learning and memory. NMDAR function is tightly regulated by functionally opposed families of kinases and phosphatases. Herein we show that the striatal-enriched protein tyrosine phosphatase (STEP) is recruited by Gαq-coupled receptors, including the M1 muscarinic acetylcholine receptor (M1R), and opposes the Src tyrosine kinase-mediated increase in the function of NMDARs composed of GluN2A. STEP activation by M1R stimulation requires IP3Rs and can depress NMDA-evoked currents with modest intracellular Ca2+ buffering. Src recruitment by M1R stimulation requires coincident NMDAR activation and can augment NMDA-evoked currents with high intracellular Ca2+ buffering. Our findings suggest that Src and STEP recruitment is contingent on differing intracellular Ca2+ dynamics that dictate whether NMDAR function is augmented or depressed following M1R stimulation. PMID:27857196

Role of sigma 1 receptor in high fat diet-induced peripheral neuropathy.

PubMed

Song, Tieying; Zhao, Jianhui; Ma, Xiaojing; Zhang, Zaiwang; Jiang, Bo; Yang, Yunliang

2017-09-26

The neurobiological mechanisms of obesity-induced peripheral neuropathy are poorly understood. We evaluated the role of Sigma-1 receptor (Sig-1R) and NMDA receptor (NMDARs) in the spinal cord in peripheral neuropathy using an animal model of high fat diet-induced diabetes. We examined the expression of Sig-1R and NMDAR subunits GluN2A and GluN2B along with postsynaptic density protein 95 (PSD-95) in the spinal cord after 24-week HFD treatment in both wild-type and Sig-1R-/- mice. Finally, we examined the effects of repeated intrathecal administrations of selective Sig-1R antagonists BD1047 in HFD-fed wild-type mice on peripheral neuropathy. Wild-type mice developed tactile allodynia and thermal hypoalgesia after 24-week HFD treatment. HFD-induced peripheral neuropathy correlated with increased expression of GluN2A and GluN2B subunits of NMDARs, PDS-95, and Sig-1R, as well as increased Sig-1R-NMDAR interaction in the spinal cord. In contrast, Sig-1R-/- mice did not develop thermal hypoalgesia or tactile allodynia after 24-week HFD treatment, and the levels of GluN2A, GluN2B, and PSD-95 were not altered in the spinal cord of HFD-fed Sig-1R-/- mice. Finally, repeated intrathecal administrations of selective Sig-1R antagonists BD1047 in HFD-fed wild-type mice attenuated peripheral neuropathy. Our results suggest that obesity-associated peripheral neuropathy may involve Sig-1R-mediated enhancement of NMDAR expression in the spinal cord.

Ethanol-mediated facilitation of AMPA receptor function in the dorsomedial striatum: implications for alcohol drinking behavior.

PubMed

Wang, Jun; Ben Hamida, Sami; Darcq, Emmanuel; Zhu, Wenheng; Gibb, Stuart L; Lanfranco, Maria Fe; Carnicella, Sebastien; Ron, Dorit

2012-10-24

We found previously that acute ex vivo as well as repeated cycles of in vivo ethanol exposure and withdrawal, including excessive voluntary consumption of ethanol, produces a long-lasting increase in the activity of NR2B-containing NMDA receptors (NR2B-NMDARs) in the dorsomedial striatum (DMS) of rats (Wang et al., 2010a). Activation of NMDARs is required for the induction of long-term potentiation (LTP) of AMPA receptor (AMPAR)-mediated synaptic response. We therefore examined whether the ethanol-mediated upregulation of NMDAR activity alters the induction of LTP in the DMS. We found that ex vivo acute exposure of striatal slices to, and withdrawal from, ethanol facilitates the induction of LTP in DMS neurons, which is abolished by the inhibition of NR2B-NMDARs. We also report that repeated systemic administration of ethanol causes an NR2B-NMDAR-dependent facilitation of LTP in the DMS. LTP is mediated by the insertion of AMPAR subunits into the synaptic membrane, and we found that repeated systemic administration of ethanol, as well as cycles of excessive ethanol consumption and withdrawal, produced a long-lasting increase in synaptic localization of the GluR1 and GluR2 subunits of AMPARs in the DMS. Importantly, we report that inhibition of AMPARs in the DMS attenuates operant self-administration of ethanol, but not of sucrose. Together, our data suggest that aberrant synaptic plasticity in the DMS induced by repeated cycles of ethanol exposure and withdrawal contributes to the molecular mechanisms underlying the development and/or maintenance of excessive ethanol consumption.

Disease-associated missense mutations in GluN2B subunit alter NMDA receptor ligand binding and ion channel properties.

PubMed

Fedele, Laura; Newcombe, Joseph; Topf, Maya; Gibb, Alasdair; Harvey, Robert J; Smart, Trevor G

2018-03-06

Genetic and bioinformatic analyses have identified missense mutations in GRIN2B encoding the NMDA receptor GluN2B subunit in autism, intellectual disability, Lennox Gastaut and West Syndromes. Here, we investigated several such mutations using a near-complete, hybrid 3D model of the human NMDAR and studied their consequences with kinetic modelling and electrophysiology. The mutants revealed reductions in glutamate potency; increased receptor desensitisation; and ablation of voltage-dependent Mg 2+ block. In addition, we provide new views on Mg 2+ and NMDA channel blocker binding sites. We demonstrate that these mutants have significant impact on excitatory transmission in developing neurons, revealing profound changes that could underlie their associated neurological disorders. Of note, the NMDAR channel mutant GluN2B V618G unusually allowed Mg 2+ permeation, whereas nearby N615I reduced Ca 2+ permeability. By identifying the binding site for an NMDAR antagonist that is used in the clinic to rescue gain-of-function phenotypes, we show that drug binding may be modified by some GluN2B disease-causing mutations.

Role of Major NMDA or AMPA Receptor Subunits in MK-801 Potentiation of Ethanol Intoxication

PubMed Central

Palachick, Benjamin; Chen, Yi-Chyan; Enoch, Abigail J.; Karlsson, Rose-Marie; Mishina, Masayoshi; Holmes, Andrew

2008-01-01

Background The glutamate system plays a major role in mediating EtOH’s effects on brain and behavior, and is implicated in the pathophysiology of alcohol-related disorders. N-methyl-D-aspartate receptor (NMDAR) antagonists such as MK-801 (dizocilpine) interact with EtOH at the behavioral level, but the molecular basis of this interaction is unclear. Methods We first characterized the effects of MK-801 treatment on responses to the ataxic (accelerating rotarod), hypothermic and sedative/hypnotic effects of acute EtOH administration in C57BL/6J and 129/SvImJ inbred mice. Effects of another NMDAR antagonist, phencyclidine, on EtOH-induced sedation/hypnosis were also assessed. Gene knockout of the NMDAR subunit NR2A or L-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate GluR1 or pharmacological antagonism of the NMDAR subunit NR2B (via Ro 25-6981) was employed to examine whether inactivating any one of these glutamate signaling molecules modified MK-801’s effect on EtOH-related behaviors. Results MK-801 markedly potentiated the ataxic effects of 1.75 g/kg EtOH and the sedative/hypnotic effects of 3.0 g/kg EtOH, but not the hypothermic effects of 3.0 g/kg EtOH, in C57BL/6J and 129/SvImJ mice. Phencyclidine potentiated EtOH-induced sedation/hypnosis in both inbred strains. Neither NR2A nor GluR1 KO significantly altered basal EtOH-induced ataxia, hypothermia, or sedation/hypnosis. Ro 25-6981 modestly increased EtOH-induced sedation/hypnosis. The ability of MK-801 to potentiate EtOH-induced ataxia and sedation/hypnosis was unaffected by GluR1 KO or NR2B antagonism. NR2A KO partially reduced MK-801 + EtOH-induced sedation/hypnosis, but not ataxia or hypothermia. Conclusions Data confirm a robust and response-specific potentiating effect of MK-801 on sensitivity to EtOH’s intoxicating effects. Inactivation of three major components of glutamate signaling had no or only partial impact on the ability of MK-801 to potentiate behavioral sensitivity to EtOH. Further work to elucidate the mechanisms underlying NMDAR × EtOH interactions could ultimately provide novel insight into the role of NMDARs in alcoholism and its treatment. PMID:18565157

Prefrontal NMDA receptors expressed in excitatory neurons control fear discrimination and fear extinction.

PubMed

Vieira, Philip A; Corches, Alex; Lovelace, Jonathan W; Westbrook, Kevin B; Mendoza, Michael; Korzus, Edward

2015-03-01

N-methyl-D-aspartate receptors (NMDARs) are critically involved in various learning mechanisms including modulation of fear memory, brain development and brain disorders. While NMDARs mediate opposite effects on medial prefrontal cortex (mPFC) interneurons and excitatory neurons, NMDAR antagonists trigger profound cortical activation. The objectives of the present study were to determine the involvement of NMDARs expressed specifically in excitatory neurons in mPFC-dependent adaptive behaviors, specifically fear discrimination and fear extinction. To achieve this, we tested mice with locally deleted Grin1 gene encoding the obligatory NR1 subunit of the NMDAR from prefrontal CamKIIα positive neurons for their ability to distinguish frequency modulated (FM) tones in fear discrimination test. We demonstrated that NMDAR-dependent signaling in the mPFC is critical for effective fear discrimination following initial generalization of conditioned fear. While mice with deficient NMDARs in prefrontal excitatory neurons maintain normal responses to a dangerous fear-conditioned stimulus, they exhibit abnormal generalization decrement. These studies provide evidence that NMDAR-dependent neural signaling in the mPFC is a component of a neural mechanism for disambiguating the meaning of fear signals and supports discriminative fear learning by retaining proper gating information, viz. both dangerous and harmless cues. We also found that selective deletion of NMDARs from excitatory neurons in the mPFC leads to a deficit in fear extinction of auditory conditioned stimuli. These studies suggest that prefrontal NMDARs expressed in excitatory neurons are involved in adaptive behavior. Copyright © 2015 Elsevier Inc. All rights reserved.

Acute Mechanisms Underlying Antibody Effects in Anti–N-Methyl-D-Aspartate Receptor Encephalitis

PubMed Central

Moscato, Emilia H; Peng, Xiaoyu; Jain, Ankit; Parsons, Thomas D; Dalmau, Josep; Balice-Gordon, Rita J

2014-01-01

Objective A severe but treatable form of immune-mediated encephalitis is associated with antibodies in serum and cerebrospinal fluid (CSF) against the GluN1 subunit of the N-methyl-D-aspartate receptor (NMDAR). Prolonged exposure of hippocampal neurons to antibodies from patients with anti-NMDAR encephalitis caused a reversible decrease in the synaptic localization and function of NMDARs. However, acute effects of the antibodies, fate of the internalized receptors, type of neurons affected, and whether neurons develop compensatory homeostatic mechanisms were unknown and are the focus of this study. Methods Dissociated hippocampal neuron cultures and rodent brain sections were used for immunocytochemical, physiological, and molecular studies. Results Patient antibodies bind to NMDARs throughout the rodent brain, and decrease NMDAR cluster density in both excitatory and inhibitory hippocampal neurons. They rapidly increase the internalization rate of surface NMDAR clusters, independent of receptor activity. This internalization likely accounts for the observed decrease in NMDAR-mediated currents, as no evidence of direct blockade was detected. Once internalized, antibody-bound NMDARs traffic through both recycling endosomes and lysosomes, similar to pharmacologically induced NMDAR endocytosis. The antibodies are responsible for receptor internalization, as their depletion from CSF abrogates these effects in hippocampal neurons. We find that although anti-NMDAR antibodies do not induce compensatory changes in glutamate receptor gene expression, they cause a decrease in inhibitory synapse density onto excitatory hippocampal neurons. Interpretation Our data support an antibody-mediated mechanism of disease pathogenesis driven by immunoglobulin-induced receptor internalization. Antibody-mediated downregulation of surface NMDARs engages homeostatic synaptic plasticity mechanisms, which may inadvertently contribute to disease progression. Ann Neurol 2014;76:108–119 PMID:24916964

Impaired Discrimination Learning in Mice Lacking the NMDA Receptor NR2A Subunit

ERIC Educational Resources Information Center

Brigman, Jonathan L.; Feyder, Michael; Saksida, Lisa M.; Bussey, Timothy J.; Mishina, Masayoshi; Holmes, Andrew

2008-01-01

N-Methyl-D-aspartate receptors (NMDARs) mediate certain forms of synaptic plasticity and learning. We used a touchscreen system to assess NR2A subunit knockout mice (KO) for (1) pairwise visual discrimination and reversal learning and (2) acquisition and extinction of an instrumental response requiring no pairwise discrimination. NR2A KO mice…

Prolonged ketamine exposure induces increased activity of the GluN2B-containing N-methyl-d-aspartate receptor in the anterior cingulate cortex of neonatal rats.

PubMed

Kokane, Saurabh S; Gong, Kerui; Jin, Jianhui; Lin, Qing

2017-09-01

Ketamine is a commonly used anesthetic among pediatric patients due to its high efficacy. However, it has been demonstrated by several preclinical studies that, widespread accelerated programmed death of neurons (neuroapoptosis) occurs due to prolonged or repeated exposure to ketamine specifically in the neonatal brain. Therefore, an emphasis on understanding the molecular mechanisms underlying this selective vulnerability of the neonatal brain to ketamine-induced neuroapoptosis becomes important in order to identify potential therapeutic targets, which would help prevent or at least ameliorate this neuroapoptosis. In this study, we demonstrated that repeated ketamine administration (6 injections of 20mg/kg dose given over 12h time period) in neonatal (postnatal day 7; PND 7) Sprague-Dawley rats induced a progressive increase in N-methyl-d-aspartate receptor (NMDAR)-mediated excitatory postsynaptic currents (EPSCs) in the neurons of the anterior cingulate cortex (ACC) for up to 6h after the last ketamine dose. Specifically, we observed that the increased EPSCs were largely mediated by GluN2B-containing NMDARs in the neurons of the ACC. Along with increased synaptic transmission, there was also a significant increase in the expression of the GluN2B-containing NMDARs as well. Taken together, these results showed that after repeated exposure to ketamine, the synaptic transmission mediated by GluN2B-containing NMDARs was significantly increased in the neonatal brain. This was significant as it showed for the first time that ketamine had subunit-specific effects on GluN2B-containing NMDARs, potentially implicating the involvement of these subunits in the increased vulnerability of immature neurons of the neonatal brain to ketamine-induced neuroapoptosis. Copyright © 2017 Elsevier Inc. All rights reserved.

Curcumin Modulates the NMDA Receptor Subunit Composition Through a Mechanism Involving CaMKII and Ser/Thr Protein Phosphatases.

PubMed

Mallozzi, Cinzia; Parravano, Mariacristina; Gaddini, Lucia; Villa, Marika; Pricci, Flavia; Malchiodi-Albedi, Fiorella; Matteucci, Andrea

2018-05-30

Curcumin is one of the major compounds contained in turmeric, the powdered rhizome of Curcuma longa. Results obtained in various experimental models indicate that curcumin has the potential to treat a large variety of neuronal diseases. Excitotoxicity, the toxicity due to pathological glutamate receptors stimulation, has been considered to be involved in several ocular pathologies including ischemia, glaucoma, and diabetic retinopathy. The NMDA receptor (NMDAR), a heteromeric ligand-gated ion channel, is composed of GluN1 and GluN2 subunits. There are four GluN2 subunits (GluN2A-D), which are major determinants of the functional properties of NMDARs. It is widely accepted that GluN2B has a pivotal role in excitotoxicity while the role of GluN2A remains controversial. We previously demonstrated that curcumin is neuroprotective against NMDA-induced excitotoxicity with a mechanism involving an increase of GluN2A subunit activity. In this paper, we investigate the mechanisms involved in curcumin-induced GluN2A increase in retinal cultures. Our results show that curcumin treatment activated CaMKII with a time-course that paralleled those of GluN2A increase. Moreover, KN-93, a CaMKII inhibitor, was able to block the effect of curcumin on GluN2A expression. Finally, in our experimental model, curcumin reduced ser/thr phosphatases activity. Using okadaic acid, a specific PP1 and PP2A blocker, we observed an increase in GluN2A levels in cultures. The ability of okadaic acid to mimic the effect of curcumin on GluN2A expression suggests that curcumin might regulate GluN2A expression through a phosphatase-dependent mechanism. In conclusion, our findings indicate curcumin modulation of CaMKII and/or ser/thr phosphatases activities as a mechanism involved in GluN2A expression and neuroprotection against excitotoxicity.

Genetically encoding a light switch in an ionotropic glutamate receptor reveals subunit-specific interfaces.

PubMed

Zhu, Shujia; Riou, Morgane; Yao, C Andrea; Carvalho, Stéphanie; Rodriguez, Pamela C; Bensaude, Olivier; Paoletti, Pierre; Ye, Shixin

2014-04-22

Reprogramming receptors to artificially respond to light has strong potential for molecular studies and interrogation of biological functions. Here, we design a light-controlled ionotropic glutamate receptor by genetically encoding a photoreactive unnatural amino acid (UAA). The photo-cross-linker p-azido-L-phenylalanine (AzF) was encoded in NMDA receptors (NMDARs), a class of glutamate-gated ion channels that play key roles in neuronal development and plasticity. AzF incorporation in the obligatory GluN1 subunit at the GluN1/GluN2B N-terminal domain (NTD) upper lobe dimer interface leads to an irreversible allosteric inhibition of channel activity upon UV illumination. In contrast, when pairing the UAA-containing GluN1 subunit with the GluN2A subunit, light-dependent inactivation is completely absent. By combining electrophysiological and biochemical analyses, we identify subunit-specific structural determinants at the GluN1/GluN2 NTD dimer interfaces that critically dictate UV-controlled inactivation. Our work reveals that the two major NMDAR subtypes differ in their ectodomain-subunit interactions, in particular their electrostatic contacts, resulting in GluN1 NTD coupling more tightly to the GluN2B NTD than to the GluN2A NTD. It also paves the way for engineering light-sensitive ligand-gated ion channels with subtype specificity through the genetic code expansion.

Evidence for a causative role of N-methyl-D-aspartate receptors in an in vitro model of alcohol withdrawal hyperexcitability.

PubMed

Thomas, M P; Monaghan, D T; Morrisett, R A

1998-10-01

Synaptic mechanisms underlying hyperexcitability due to withdrawal from chronic ethanol exposure were investigated in a hippocampal explant model system using electrophysiological techniques. Whole-cell voltage clamp recordings from CA1 pyramidal cells demonstrated that acute ethanol exposure inhibited N-methyl-D-aspartate receptor (NMDAR)-mediated excitatory postsynaptic currents by over 40%. Chronic ethanol exposure for 6 to 11 days at 35 or 75 mM induced no differences from control explants in the fast component of the population synaptic response (non-NMDAR-mediated). Prolonged field potential recordings (to 10 hr) were used to monitor the withdrawal process in vitro. Ethanol-exposed explants from both 35 and 75 mM groups displayed an increase (60% and 89%, respectively) in the NMDAR-mediated component of synaptic transmission on withdrawal from chronic exposure. Prolonged tonic-clonic electrographic seizure activity was consistently observed after ethanol withdrawal only after the increase in NMDAR function. This hyperexcitability was inhibited by the NMDAR antagonist D-2-amino-5-phosphonovaleric acid and returned once the NMDAR component was reestablished after antagonist washout. In situ hybridization studies suggest that expression of NR2B subunit mRNA may be enhanced in explants after chronic ethanol exposure. No lasting differences were observed in the NMDAR component after acute in vitro ethanol exposure and withdrawal. These data suggest that the occurance of ethanol withdrawal hyperexcitability in this system may be directly dependent on alterations in NMDAR function after chronic exposure. Since this region and others that contain ethanol sensitive NMDARs may serve as epileptic foci, long term alterations in NMDAR function may be expected to generate paroxysmal depolarizing shifts underlying ictal events after withdrawal from ethanol exposure.

Oxidative stress upregulates the NMDA receptor on cerebrovascular endothelium.

PubMed

Betzen, Christian; White, Robin; Zehendner, Christoph M; Pietrowski, Eweline; Bender, Bianca; Luhmann, Heiko J; Kuhlmann, Christoph R W

2009-10-15

N-methyl-d-aspartate receptor (NMDA-R)-mediated oxidative stress has been implicated in blood-brain barrier (BBB) disruption in a variety of neuropathological diseases. Although some interactions between both phenomena have been elucidated, possible influences of reactive oxygen species (ROS) on the NMDA-R itself have so far been neglected. The objective of this study was to examine how the cerebroendothelial NMDA-R is affected by exposure to oxidative stress and to assess possible influences on BBB integrity. RT-PCR confirmed several NMDA-R subunits (NR1, NR2B-D) expressed in the bEnd3 cell line (murine cerebrovascular endothelial cells). NR1 protein expression after exposure to ROS was observed via in-cell Western. The functionality of the expressed NMDA-R was determined by measuring DiBAC fluorescence in ROS-preexposed cells upon stimulation with the specific agonist NMDA. Finally, the effects on barrier integrity were evaluated using the ECIS system to detect changes in monolayer impedance upon NMDA-R stimulation after exposure to ROS. The expression of NR1 significantly (p<0.001) increased 72 h after 30 min exposure to superoxide (+33.8+/-7.5%), peroxynitrite (+84.9+/-10.7%), or hydrogen peroxide (+92.8+/-7.6%), resulting in increased cellular response to NMDA-R stimulation and diminished monolayer impedance. We conclude that oxidative stress upregulates NMDA-R on cerebrovascular endothelium and thus heightens susceptibility to glutamate-induced BBB disruption.

Neuropsychiatric lupus and auto-antibodies against ionotropic glutamate receptor (NMDAR)

PubMed Central

Cohen-Solal, J.F.G.; Diamond, B.

2010-01-01

Almost half of lupus patients will experience neuropsychiatric symptoms during the course of their disease. The etiology of the neuronal damages are still uncertain and probably multiple. Auto-antibodies reactive with brain have been postulated to play a role. The observation of pathogenic auto-antibodies binding the NR2A and NR2B subunits of the ionotropic glutamate receptor (NMDAR) illustrates this hypothesis. First studies showed that 40% of lupus patients possess serum titers of anti-NR2A/B antibody, but the presence of these auto-antibodies is not always associated with the occurrence of neuronal damages or neuropsychiatric symptoms. Nevertheless, their presence is observed in the cerebro-spinal fluid (CSF) of one half of the patients suffering from neurolupus. The presence in the serum of these auto-antibodies anti-NR2A/B of the NMDAR is preliminary to their presence in the CSF where their deleterious effect is observable. Their entry into the brain is dependent on a breach of the blood brain barrier (BBB). In conclusion, the serum titer of auto-antibodies against NR2A/B subunits is an indication of the potential for neuro-psychiatric manifestations during the course of the disease. PMID:20605660

Bacopa monnieri Extract (CDRI-08) Modulates the NMDA Receptor Subunits and nNOS-Apoptosis Axis in Cerebellum of Hepatic Encephalopathy Rats

PubMed Central

Mondal, Papia; Trigun, Surendra Kumar

2015-01-01

Hepatic encephalopathy (HE), characterized by impaired cerebellar functions during chronic liver failure (CLF), involves N-methyl-D-aspartate receptor (NMDAR) overactivation in the brain cells. Bacopa monnieri (BM) extract is a known neuroprotectant. The present paper evaluates whether BM extract is able to modulate the two NMDAR subunits (NR2A and NR2B) and its downstream mediators in cerebellum of rats with chronic liver failure (CLF), induced by administration of 50 mg/kg bw thioacetamide (TAA) i.p. for 14 days, and in the TAA group rats orally treated with 200 mg/kg bw BM extract from days 8 to 14. NR2A is known to impart neuroprotection and that of NR2B induces neuronal death during NMDAR activation. Neuronal nitric oxide synthase- (nNOS-) apoptosis pathway is known to mediate NMDAR led excitotoxicity. The level of NR2A was found to be significantly reduced with a concomitant increase of NR2B in cerebellum of the CLF rats. This was consistent with significantly enhanced nNOS expression, nitric oxide level, and reduced Bcl2/Bax ratio. Moreover, treatment with BM extract reversed the NR2A/NR2B ratio and also normalized the levels of nNOS-apoptotic factors in cerebellum of those rats. The findings suggest modulation of NR2A and NR2B expression by BM extract to prevent neurochemical alterations associated with HE. PMID:26413124

NMDA Receptors Mediate Olfactory Learning and Memory in Drosophila

PubMed Central

Xia, Shouzhen; Miyashita, Tomoyuki; Fu, Tsai-Feng; Lin, Wei-Yong; Wu, Chia-Lin; Pyzocha, Lori; Lin, Inn-Ray; Saitoe, Minoru; Tully, Tim; Chiang, Ann-Shyn

2011-01-01

Summary Background Molecular and electrophysiological properties of NMDARs suggest that they may be the Hebbian “coincidence detectors” hypothesized to underlie associative learning. Because of the nonspecificity of drugs that modulate NMDAR function or the relatively chronic genetic manipulations of various NMDAR subunits from mammalian studies, conclusive evidence for such an acute role for NMDARs in adult behavioral plasticity, however, is lacking. Moreover, a role for NMDARs in memory consolidation remains controversial. Results The Drosophila genome encodes two NMDAR homologs, dNR1 and dNR2. When coexpressed in Xenopus oocytes or Drosophila S2 cells, dNR1 and dNR2 form functional NMDARs with several of the distinguishing molecular properties observed for vertebrate NMDARs, including voltage/Mg2+-dependent activation by glutamate. Both proteins are weakly expressed throughout the entire brain but show preferential expression in several neurons surrounding the dendritic region of the mushroom bodies. Hypomorphic mutations of the essential dNR1 gene disrupt olfactory learning, and this learning defect is rescued with wild-type transgenes. Importantly, we show that Pavlovian learning is disrupted in adults within 15 hr after transient induction of a dNR1 antisense RNA transgene. Extended training is sufficient to overcome this initial learning defect, but long-term memory (LTM) specifically is abolished under these training conditions. Conclusions Our study uses a combination of molecular-genetic tools to (1) generate genomic mutations of the dNR1 gene, (2) rescue the accompanying learning deficit with a dNR1+ transgene, and (3) rapidly and transiently knockdown dNR1+ expression in adults, thereby demonstrating an evolutionarily conserved role for the acute involvement of NMDARs in associative learning and memory. PMID:15823532

Neuroadaptive changes in NMDAR1 gene expression after extinction of cocaine self-administration.

PubMed

Crespo, José A; Oliva, José M; Ghasemzadeh, M Benham; Kalivas, Peter W; Ambrosio, E

2002-06-01

The aim of the present work was to study the time course effects in levels of mRNA encoding N-methyl-d-aspartate receptor subunit 1 (NMDAR1) after long-term cocaine self-administration (1 mg/kg/ injection) and its extinction using a yoked-box procedure. NMDAR1 content was measured by quantitative in situ hybridization histochemistry in prefrontal cortex, caudate-putamen, nucleus accumbens, olfactory tubercle, and piriform cortex immediately after cessation of the last session of cocaine self-administration (Day 0) and 1, 5, and 10 days after the extinction period. The results show that long-term cocaine self-administration and its extinction alter NMDAR1 gene expression in these forebrain regions, and that the changes depend upon the brain region examined and the type of cocaine administration (contingent, noncontingent, and saline). Compared to saline and noncontingent cocaine administration, contingent cocaine produced an up-regulation in NMDAR1 gene expression on Day 0 in all the brain regions analyzed. NMDAR1 levels of contingent animals decreased progressively in the absence of cocaine, and the decrement persisted 10 days after the extinction of cocaine self-administration behavior in all the forebrain areas, with the exception of olfactory tubercle. In contrast, noncontingent cocaine administration did not produce any change in NMDAR1 gene expression on Day 0, and extinction resulted in an increase of NMDAR1 mRNA content on Days 1 and 5 and returned to control (saline) values on Day 10. These results suggest that an interaction between environmental stimuli and the pharmacological action of cocaine during drug self-administration and its extinction may represent an important factor in the regulation of cocaine effects on NMDAR1 gene expression.

NMDA receptors mediate olfactory learning and memory in Drosophila.

PubMed

Xia, Shouzhen; Miyashita, Tomoyuki; Fu, Tsai-Feng; Lin, Wei-Yong; Wu, Chia-Lin; Pyzocha, Lori; Lin, Inn-Ray; Saitoe, Minoru; Tully, Tim; Chiang, Ann-Shyn

2005-04-12

Molecular and electrophysiological properties of NMDARs suggest that they may be the Hebbian "coincidence detectors" hypothesized to underlie associative learning. Because of the nonspecificity of drugs that modulate NMDAR function or the relatively chronic genetic manipulations of various NMDAR subunits from mammalian studies, conclusive evidence for such an acute role for NMDARs in adult behavioral plasticity, however, is lacking. Moreover, a role for NMDARs in memory consolidation remains controversial. The Drosophila genome encodes two NMDAR homologs, dNR1 and dNR2. When coexpressed in Xenopus oocytes or Drosophila S2 cells, dNR1 and dNR2 form functional NMDARs with several of the distinguishing molecular properties observed for vertebrate NMDARs, including voltage/Mg(2+)-dependent activation by glutamate. Both proteins are weakly expressed throughout the entire brain but show preferential expression in several neurons surrounding the dendritic region of the mushroom bodies. Hypomorphic mutations of the essential dNR1 gene disrupt olfactory learning, and this learning defect is rescued with wild-type transgenes. Importantly, we show that Pavlovian learning is disrupted in adults within 15 hr after transient induction of a dNR1 antisense RNA transgene. Extended training is sufficient to overcome this initial learning defect, but long-term memory (LTM) specifically is abolished under these training conditions. Our study uses a combination of molecular-genetic tools to (1) generate genomic mutations of the dNR1 gene, (2) rescue the accompanying learning deficit with a dNR1+ transgene, and (3) rapidly and transiently knockdown dNR1+ expression in adults, thereby demonstrating an evolutionarily conserved role for the acute involvement of NMDARs in associative learning and memory.

Astrocytes regulate heterogeneity of presynaptic strengths in hippocampal networks

PubMed Central

Letellier, Mathieu; Park, Yun Kyung; Chater, Thomas E.; Chipman, Peter H.; Gautam, Sunita Ghimire; Oshima-Takago, Tomoko; Goda, Yukiko

2016-01-01

Dendrites are neuronal structures specialized for receiving and processing information through their many synaptic inputs. How input strengths are modified across dendrites in ways that are crucial for synaptic integration and plasticity remains unclear. We examined in single hippocampal neurons the mechanism of heterosynaptic interactions and the heterogeneity of synaptic strengths of pyramidal cell inputs. Heterosynaptic presynaptic plasticity that counterbalances input strengths requires N-methyl-d-aspartate receptors (NMDARs) and astrocytes. Importantly, this mechanism is shared with the mechanism for maintaining highly heterogeneous basal presynaptic strengths, which requires astrocyte Ca2+ signaling involving NMDAR activation, astrocyte membrane depolarization, and L-type Ca2+ channels. Intracellular infusion of NMDARs or Ca2+-channel blockers into astrocytes, conditionally ablating the GluN1 NMDAR subunit, or optogenetically hyperpolarizing astrocytes with archaerhodopsin promotes homogenization of convergent presynaptic inputs. Our findings support the presence of an astrocyte-dependent cellular mechanism that enhances the heterogeneity of presynaptic strengths of convergent connections, which may help boost the computational power of dendrites. PMID:27118849

A Special Extract of Bacopa monnieri (CDRI-08) Restores Learning and Memory by Upregulating Expression of the NMDA Receptor Subunit GluN2B in the Brain of Scopolamine-Induced Amnesic Mice

PubMed Central

Rai, Rakesh; Singh, Hemant K.; Prasad, S.

2015-01-01

In the present communication, we have investigated effects of the CDRI-08, a well characterized extract of Bacopa monnieri, on expression of the GluN2B subunit of NMDAR in various brain regions of the scopolamine-induced amnesic mice. Our behavioral data reveal that scopolamine-treated amnesic mice exhibit significant decline in the spatial memory compared to the normal control mice. Our RT-PCR and immunoblotting data revealed that the scopolamine treatment resulted in a significant downregulation of the NMDAR GluN2B subunit expression in prefrontal cortex and hippocampus. Our enzyme assay data revealed that scopolamine caused a significant increase in the acetylcholinesterase activity in both the brain regions. Further, oral administration of the CDRI-08 to scopolamine-treated amnesic mice restored the spatial memory which was found to be associated with significant upregulation of the GluN2B subunit expression and decline in the acetylcholinesterase activity in prefrontal cortex as well as hippocampus towards their levels in the normal control mice. Our study provides the evidence for the mechanism underlying role of the Bacopa monnieri extract (CDRI-08) in restoring spatial memory in amnesic mice, which may have therapeutic implications. PMID:26413117

Long term impairment of cognitive functions and alterations of NMDAR subunits after continuous microwave exposure.

PubMed

Wang, Hui; Tan, Shengzhi; Xu, Xinping; Zhao, Li; Zhang, Jing; Yao, Binwei; Gao, Yabing; Zhou, Hongmei; Peng, Ruiyun

2017-11-01

The long term effects of continuous microwave exposure cannot be ignored for the simulation of the real environment and increasing concerns about the negative cognitive effects of microwave exposure. In this study, 220 male Wistar rats were exposed by a 2.856GHz radiation source with the average power density of 0, 2.5, 5 and 10mW/cm 2 for 6min/day, 5days/week and up to 6weeks. The MWM task, the EEG analysis, the hippocampus structure observation and the western blot were applied until the 12months after microwave exposure to detect the spatial learning and memory abilities, the cortical electrical activity, changes of hippocampal structure and the NMDAR subunits expressions. Results found that the rats in the 10mW/cm 2 group showed the decline of spatial learning and memory abilities and EEG disorders (the decrease of EEG frequencies, and increase of EEG amplitudes and delta wave powers). Moreover, changes of basic structure and ultrastructure of hippocampus also found in the 10 and 5mW/cm 2 groups. The decrease of NR 2A, 2B and p-NR2B might contribute to the impairment of cognitive functions. Our findings suggested that the continuous microwave exposure could cause the dose-dependent long term impairment of spatial learning and memory, the abnormalities of EEG and the hippocampal structure injuries. The decrease of NMDAR key subunits and phosphorylation of NR 2B might contribute to the cognitive impairment. Copyright © 2017 Elsevier Inc. All rights reserved.

Case report of anti-N-methyl-D-aspartate receptor encephalitis in a middle-aged woman with a long history of major depressive disorder.

PubMed

Rong, Xia; Xiong, Zhenzhen; Cao, Bingrong; Chen, Juan; Li, Mingli; Li, Zhe

2017-08-31

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune disease involving antibodies against the NR1 subunits of NMDARs. The disease shows variable clinical presentation, and involves new-onset acute psychotic symptoms, making it difficult to differentiate from major depressive disorder with psychotic symptoms. Potential associations between this autoimmune disorder and onset or progression of major depressive disorder remains unclear. We present a rare case of a patient who had both major depressive disorder and anti-NMDAR encephalitis and in whom the encephalitis initially went undetected. The patient had been suffering from depressive disorder for more than 6 years without any treatment, when she was hospitalized for new-onset psychotic symptoms. She was initially diagnosed only with major depressive disorder with psychotic symptoms, but antipsychotics did not alleviate symptoms and the patient's psychiatric course began to fluctuate rapidly. Anti-NR1 IgG autoantibodies were detected in cerebrospinal fluid, and the combination of immunotherapy and antipsychotics proved more effective than antipsychotics alone. The patient was then also diagnosed with anti-NMDAR encephalitis. Our case suggests that clinicians should consider anti-NMDAR encephalitis when a patient with depressive disorder shows sudden fluctuations in psychiatric symptoms. It also highlights the need for research into possible relationships between anti-NMDAR encephalitis and major depressive disorder.

Role of the metabotropic P2Y(4) receptor during hypoglycemia: cross talk with the ionotropic NMDAR1 receptor.

PubMed

Cavaliere, Fabio; Amadio, Susanna; Angelini, Daniela F; Sancesario, Giuseppe; Bernardi, Giorgio; Volonté, Cinzia

2004-10-15

It is well established that both extracellular ATP and glutamate exert a critical role during metabolic impairment, that several P2 receptor subunits are directly involved in this action and that a strong relationship exists between glutamatergic and purinergic signals. Therefore, here we studied the molecular behavior of the purinergic metabotropic P2Y(4) and the glutamatergic ionotropic NMDAR1 receptors during hypoglycemic cell death. We find that these proteins are oppositely modulated during glucose starvation (P2Y(4) is induced, whereas NMDAR1 is inhibited) and that both P2 and NMDA antagonists can restore basal protein expression levels. Moreover, double immunofluorescence experiments with confocal laser microscopy reveal co-localization at the membrane level between the P2Y(4) and NMDAR1 receptors, in both homologous (cerebellar granule neurons) and heterologous (Hek-293) cellular systems. This is furthermore confirmed by co-immunoprecipitation experiments. Finally, when we express the P2Y(4) receptor in the heterologous SH-SY5Y neuronal cell line, hypoglycemia then causes severe cell death and simultaneous downregulation of the NMDAR1 protein. In summary, our work establishes a potential molecular interplay between P2Y(4) and NMDAR1 receptors during glucose deprivation and the causative role of the P2Y(4) during cell death.

NMDAR-1 staining in the lateral geniculate nucleus of normal and visually deprived cats.

PubMed

Ziburkus, J; Bickford, M E; Guido, W

2000-01-01

In normal adult cats, a monoclonal antibody directed toward the NR-1 subunit of the N-methyl-D-aspartate (NMDA) receptor (Pharmingen, clone 54.1) produced dense cellular and neuropil labeling throughout all layers of the lateral geniculate nucleus (LGN) and adjacent thalamic nuclei, including the thalamic reticular, perigeniculate, medial intralaminar, and ventral lateral geniculate nuclei. Cellular staining revealed well-defined somata, and in some cases proximal dendrites. NMDAR-1 cell labeling was also evident in the LGN of early postnatal kittens, suggesting that developing LGN cells possess this receptor subunit at or before eye opening. Within the A-layers of the adult LGN, staining encompassed a wide range of soma sizes. Soma size comparisons of NMDAR-1 stained cells with those stained with an antibody directed toward a nonphosphorylated neurofilament protein (SMI-32), which selectively stains Y-relay cells (Bickford et al., 1998), or an antibody to glutamic acid decarboxylase (GAD), which stains for GABAergic interneurons, suggested that NMDA receptors are utilized by relay cells and interneurons. NMDAR-1 staining was also observed in the LGN of cats with early monocular lid suture. Although labeling was apparent in both deprived and nondeprived A-layers of LGN, the distribution of soma sizes was significantly different. In the deprived A-layers of LGN, staining was limited to small- and medium-sized cells. Cells with relatively large soma were lacking. However, cell density measurements as well as soma size comparisons with cells stained for Nissl substance suggested these differences were due to deprivation-induced cell shrinkage and not to a loss of NMDAR-1 staining in Y-cells. Taken together, these results suggest that NMDA receptors are utilized by both relay cells and interneurons in LGN and that alterations in early visual experience do not necessarily affect the expression of NMDA receptors in the LGN.

Reduced expression of the NMDA receptor-interacting protein SynGAP causes behavioral abnormalities that model symptoms of Schizophrenia.

PubMed

Guo, Xiaochuan; Hamilton, Peter J; Reish, Nicholas J; Sweatt, J David; Miller, Courtney A; Rumbaugh, Gavin

2009-06-01

Abnormal function of NMDA receptors is believed to be a contributing factor to the pathophysiology of schizophrenia. NMDAR subunits and postsynaptic-interacting proteins of these channels are abnormally expressed in some patients with this illness. In mice, reduced NMDAR expression leads to behaviors analogous to symptoms of schizophrenia, but reports of animals with mutations in core postsynaptic density proteins having similar a phenotype have yet to be reported. Here we show that reduced expression of the neuronal RasGAP and NMDAR-associated protein, SynGAP, results in abnormal behaviors strikingly similar to that reported in mice with reduced NMDAR function. SynGAP mutant mice exhibited nonhabituating and persistent hyperactivity that was ameliorated by the antipsychotic clozapine. An NMDAR antagonist, MK-801, induced hyperactivity in normal mice but SynGAP mutants were less responsive, suggesting that NMDAR hypofunction contributes to this behavioral abnormality. SynGAP mutants exhibited enhanced startle reactivity and impaired sensory-motor gating. These mice also displayed a complete lack of social memory and a propensity toward social isolation. Finally, SynGAP mutants had deficits in cued fear conditioning and working memory, indicating abnormal function of circuits that control emotion and choice. Our results demonstrate that SynGAP mutant mice have gross neurological deficits similar to other mouse models of schizophrenia. Because SynGAP interacts with NMDARs, and the signaling activity of this protein is regulated by these channels, our data in dicate that SynGAP lies downstream of NMDARs and is a required intermediate for normal neural circuit function and behavior. Taken together, these data support the idea that schizophrenia may arise from abnormal signaling pathways that are mediated by NMDA receptors.

NMDA Receptor Activation Underlies the Loss of Spinal Dorsal Horn Neurons and the Transition to Persistent Pain after Peripheral Nerve Injury.

PubMed

Inquimbert, Perrine; Moll, Martin; Latremoliere, Alban; Tong, Chi-Kun; Whang, John; Sheehan, Gregory F; Smith, Brendan M; Korb, Erica; Athié, Maria C P; Babaniyi, Olusegun; Ghasemlou, Nader; Yanagawa, Yuchio; Allis, C David; Hof, Patrick R; Scholz, Joachim

2018-05-29

Peripheral nerve lesions provoke apoptosis in the dorsal horn of the spinal cord. The cause of cell death, the involvement of neurons, and the relevance for the processing of somatosensory information are controversial. Here, we demonstrate in a mouse model of sciatic nerve injury that glutamate-induced neurodegeneration and loss of γ-aminobutyric acid (GABA)ergic interneurons in the superficial dorsal horn promote the transition from acute to chronic neuropathic pain. Conditional deletion of Grin1, the essential subunit of N-methyl-d-aspartate-type glutamate receptors (NMDARs), protects dorsal horn neurons from excitotoxicity and preserves GABAergic inhibition. Mice deficient in functional NMDARs exhibit normal nociceptive responses and acute pain after nerve injury, but this initial increase in pain sensitivity is reversible. Eliminating NMDARs fully prevents persistent pain-like behavior. Reduced pain in mice lacking proapoptotic Bax confirmed the significance of neurodegeneration. We conclude that NMDAR-mediated neuron death contributes to the development of chronic neuropathic pain. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Synaptic Regulation of a Thalamocortical Circuit Controls Depression-Related Behavior.

PubMed

Miller, Oliver H; Bruns, Andreas; Ben Ammar, Imen; Mueggler, Thomas; Hall, Benjamin J

2017-08-22

The NMDA receptor (NMDAR) antagonist ketamine elicits a long-lasting antidepressant response in patients with treatment-resistant depression. Understanding how antagonism of NMDARs alters synapse and circuit function is pivotal to developing circuit-based therapies for depression. Using virally induced gene deletion, ex vivo optogenetic-assisted circuit analysis, and in vivo chemogenetics and fMRI, we assessed the role of NMDARs in the medial prefrontal cortex (mPFC) in controlling depression-related behavior in mice. We demonstrate that post-developmental genetic deletion of the NMDAR subunit GluN2B from pyramidal neurons in the mPFC enhances connectivity between the mPFC and limbic thalamus, but not the ventral hippocampus, and reduces depression-like behavior. Using intersectional chemogenetics, we show that activation of this thalamocortical circuit is sufficient to elicit a decrease in despair-like behavior. Our findings reveal that GluN2B exerts input-specific control of pyramidal neuron innervation and identify a medial dorsal thalamus (MDT)→mPFC circuit that controls depression-like behavior. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

GABAB-mediated rescue of altered excitatory-inhibitory balance, gamma synchrony and behavioral deficits following constitutive NMDAR-hypofunction.

PubMed

Gandal, M J; Sisti, J; Klook, K; Ortinski, P I; Leitman, V; Liang, Y; Thieu, T; Anderson, R; Pierce, R C; Jonak, G; Gur, R E; Carlson, G; Siegel, S J

2012-07-17

Reduced N-methyl-D-aspartate-receptor (NMDAR) signaling has been associated with schizophrenia, autism and intellectual disability. NMDAR-hypofunction is thought to contribute to social, cognitive and gamma (30-80 Hz) oscillatory abnormalities, phenotypes common to these disorders. However, circuit-level mechanisms underlying such deficits remain unclear. This study investigated the relationship between gamma synchrony, excitatory-inhibitory (E/I) signaling, and behavioral phenotypes in NMDA-NR1(neo-/-) mice, which have constitutively reduced expression of the obligate NR1 subunit to model disrupted developmental NMDAR function. Constitutive NMDAR-hypofunction caused a loss of E/I balance, with an increase in intrinsic pyramidal cell excitability and a selective disruption of parvalbumin-expressing interneurons. Disrupted E/I coupling was associated with deficits in auditory-evoked gamma signal-to-noise ratio (SNR). Gamma-band abnormalities predicted deficits in spatial working memory and social preference, linking cellular changes in E/I signaling to target behaviors. The GABA(B)-receptor agonist baclofen improved E/I balance, gamma-SNR and broadly reversed behavioral deficits. These data demonstrate a clinically relevant, highly translatable neural-activity-based biomarker for preclinical screening and therapeutic development across a broad range of disorders that share common endophenotypes and disrupted NMDA-receptor signaling.

PSD-95 stabilizes NMDA receptors by inducing the degradation of STEP61.

PubMed

Won, Sehoon; Incontro, Salvatore; Nicoll, Roger A; Roche, Katherine W

2016-08-09

Phosphorylation regulates surface and synaptic expression of NMDA receptors (NMDARs). Both the tyrosine kinase Fyn and the tyrosine phosphatase striatal-enriched protein tyrosine phosphatase (STEP) are known to target the NMDA receptor subunit GluN2B on tyrosine 1472, which is a critical residue that mediates NMDAR endocytosis. STEP reduces the surface expression of NMDARs by promoting dephosphorylation of GluN2B Y1472, whereas the synaptic scaffolding protein postsynaptic density protein 95 (PSD-95) stabilizes the surface expression of NMDARs. However, nothing is known about a potential functional interaction between STEP and PSD-95. We now report that STEP61 binds to PSD-95 but not to other PSD-95 family members. We find that PSD-95 expression destabilizes STEP61 via ubiquitination and degradation by the proteasome. Using subcellular fractionation, we detect low amounts of STEP61 in the PSD fraction. However, STEP61 expression in the PSD is increased upon knockdown of PSD-95 or in vivo as detected in PSD-95-KO mice, demonstrating that PSD-95 excludes STEP61 from the PSD. Importantly, only extrasynaptic NMDAR expression and currents were increased upon STEP knockdown, as is consistent with low STEP61 localization in the PSD. Our findings support a dual role for PSD-95 in stabilizing synaptic NMDARs by binding directly to GluN2B but also by promoting synaptic exclusion and degradation of the negative regulator STEP61.

PSD-95 stabilizes NMDA receptors by inducing the degradation of STEP61

PubMed Central

Won, Sehoon; Incontro, Salvatore; Nicoll, Roger A.; Roche, Katherine W.

2016-01-01

Phosphorylation regulates surface and synaptic expression of NMDA receptors (NMDARs). Both the tyrosine kinase Fyn and the tyrosine phosphatase striatal-enriched protein tyrosine phosphatase (STEP) are known to target the NMDA receptor subunit GluN2B on tyrosine 1472, which is a critical residue that mediates NMDAR endocytosis. STEP reduces the surface expression of NMDARs by promoting dephosphorylation of GluN2B Y1472, whereas the synaptic scaffolding protein postsynaptic density protein 95 (PSD-95) stabilizes the surface expression of NMDARs. However, nothing is known about a potential functional interaction between STEP and PSD-95. We now report that STEP61 binds to PSD-95 but not to other PSD-95 family members. We find that PSD-95 expression destabilizes STEP61 via ubiquitination and degradation by the proteasome. Using subcellular fractionation, we detect low amounts of STEP61 in the PSD fraction. However, STEP61 expression in the PSD is increased upon knockdown of PSD-95 or in vivo as detected in PSD-95–KO mice, demonstrating that PSD-95 excludes STEP61 from the PSD. Importantly, only extrasynaptic NMDAR expression and currents were increased upon STEP knockdown, as is consistent with low STEP61 localization in the PSD. Our findings support a dual role for PSD-95 in stabilizing synaptic NMDARs by binding directly to GluN2B but also by promoting synaptic exclusion and degradation of the negative regulator STEP61. PMID:27457929

Neurotoxic lupus autoantibodies alter brain function through two distinct mechanisms

PubMed Central

Faust, Thomas W.; Chang, Eric H.; Kowal, Czeslawa; Berlin, RoseAnn; Gazaryan, Irina G.; Bertini, Eva; Zhang, Jie; Sanchez-Guerrero, Jorge; Fragoso-Loyo, Hilda E.; Volpe, Bruce T.; Diamond, Betty; Huerta, Patricio T.

2010-01-01

Damaging interactions between antibodies and brain antigenic targets may be responsible for an expanding range of neurological disorders. In the case of systemic lupus erythematosus (SLE), patients generate autoantibodies (AAbs) that frequently bind dsDNA. Although some symptoms of SLE may arise from direct reactivity to dsDNA, much of the AAb-mediated damage originates from cross-reactivity with other antigens. We have studied lupus AAbs that bind dsDNA and cross-react with the NR2A and NR2B subunits of the NMDA receptor (NMDAR). In adult mouse models, when the blood–brain barrier is compromised, these NMDAR-reactive AAbs access the brain and elicit neuronal death with ensuing cognitive dysfunction and emotional disturbance. The cellular mechanisms that underlie these deleterious effects remain incompletely understood. Here, we show that, at low concentration, the NMDAR-reactive AAbs are positive modulators of receptor function that increase the size of NMDAR-mediated excitatory postsynaptic potentials, whereas at high concentration, the AAbs promote excitotoxicity through enhanced mitochondrial permeability transition. Other synaptic receptors are completely unaffected by the AAbs. NMDAR activation is required for producing both the synaptic and the mitochondrial effects. Our study thus reveals the mechanisms by which NMDAR-reactive AAbs trigger graded cellular alterations, which are likely to be responsible for the transient and permanent neuropsychiatric symptoms observed in patients with SLE. Our study also provides a model in which local AAb concentration determines the exact nature of the cellular response. PMID:20921396

Magnetofection™ of NMDA Receptor Subunits GluN1 and GluN2A Expression Vectors in Non-Neuronal Host Cells.

PubMed

Bruneau, Nadine; Szepetowski, Pierre

2017-01-01

The functional study of reconstituted NMDA receptors (NMDARs) in host cells requires that the corresponding vectors for the expression of the NMDAR subunits are co-transfected with high efficiency. Magnetofection™ is a technology used to deliver nucleic acids to cells. It is driven and site-specifically guided by the attractive forces of magnetic fields acting on magnetic nanoparticles that are associated with nucleic acid vectors. In magnetofection™, cationic lipids form self-assembled complexes with the nucleic acid vectors of interest. Those complexes are then associated with magnetic nanoparticles that are concentrated at the surface of cultured cells by applying a permanent magnetic field. Magnetofection™ is a simple method to transfect cultured cells with high transfection rates. Satisfactory expression levels are obtained with very low amounts of nucleic acid vector. Moreover, incubation time with host cells is less than 1 h, as compared with the several hours needed with standard transfection assays.

Developmental changes in NMDA receptor expression in the platyfish brain

NASA Technical Reports Server (NTRS)

Flynn, K. M.; Schreibman, M. P.; Magliulo-Cepriano, L.

1997-01-01

We have examined the distribution of the N-methyl-D-aspartate (NMDA) receptor in the brain of a freshwater teleost using an antibody against the R1 subunit of the receptor (NMDAR1). The primary site of localization was the nucleus olfactoretinalis (NOR), a significant gonadotropin releasing hormone (GnRH)-containing brain nucleus. The number of cells expressing NMDAR1 in this nucleus was dependent upon developmental stage, with pubescent and mature animals displaying significantly more stained cells than immature and senescent animals. This is the first reported observation of age- and maturity-related NMDA receptor association with GnRH-containing brain areas.

Neuropsychiatric disease relevance of circulating anti-NMDA receptor autoantibodies depends on blood-brain barrier integrity.

PubMed

Hammer, C; Stepniak, B; Schneider, A; Papiol, S; Tantra, M; Begemann, M; Sirén, A-L; Pardo, L A; Sperling, S; Mohd Jofrry, S; Gurvich, A; Jensen, N; Ostmeier, K; Lühder, F; Probst, C; Martens, H; Gillis, M; Saher, G; Assogna, F; Spalletta, G; Stöcker, W; Schulz, T F; Nave, K-A; Ehrenreich, H

2014-10-01

In 2007, a multifaceted syndrome, associated with anti-NMDA receptor autoantibodies (NMDAR-AB) of immunoglobulin-G isotype, has been described, which variably consists of psychosis, epilepsy, cognitive decline and extrapyramidal symptoms. Prevalence and significance of NMDAR-AB in complex neuropsychiatric disease versus health, however, have remained unclear. We tested sera of 2817 subjects (1325 healthy, 1081 schizophrenic, 263 Parkinson and 148 affective-disorder subjects) for presence of NMDAR-AB, conducted a genome-wide genetic association study, comparing AB carriers versus non-carriers, and assessed their influenza AB status. For mechanistic insight and documentation of AB functionality, in vivo experiments involving mice with deficient blood-brain barrier (ApoE(-/-)) and in vitro endocytosis assays in primary cortical neurons were performed. In 10.5% of subjects, NMDAR-AB (NR1 subunit) of any immunoglobulin isotype were detected, with no difference in seroprevalence, titer or in vitro functionality between patients and healthy controls. Administration of extracted human serum to mice influenced basal and MK-801-induced activity in the open field only in ApoE(-/-) mice injected with NMDAR-AB-positive serum but not in respective controls. Seropositive schizophrenic patients with a history of neurotrauma or birth complications, indicating an at least temporarily compromised blood-brain barrier, had more neurological abnormalities than seronegative patients with comparable history. A common genetic variant (rs524991, P=6.15E-08) as well as past influenza A (P=0.024) or B (P=0.006) infection were identified as predisposing factors for NMDAR-AB seropositivity. The >10% overall seroprevalence of NMDAR-AB of both healthy individuals and patients is unexpectedly high. Clinical significance, however, apparently depends on association with past or present perturbations of blood-brain barrier function.

Knockout of NMDA-receptors from parvalbumin interneurons sensitizes to schizophrenia-related deficits induced by MK-801

PubMed Central

Bygrave, A M; Masiulis, S; Nicholson, E; Berkemann, M; Barkus, C; Sprengel, R; Harrison, P J; Kullmann, D M; Bannerman, D M; Kätzel, D

2016-01-01

It has been suggested that a functional deficit in NMDA-receptors (NMDARs) on parvalbumin (PV)-positive interneurons (PV-NMDARs) is central to the pathophysiology of schizophrenia. Supportive evidence come from examination of genetically modified mice where the obligatory NMDAR-subunit GluN1 (also known as NR1) has been deleted from PV interneurons by Cre-mediated knockout of the corresponding gene Grin1 (Grin1ΔPV mice). Notably, such PV-specific GluN1 ablation has been reported to blunt the induction of hyperlocomotion (a surrogate for psychosis) by pharmacological NMDAR blockade with the non-competitive antagonist MK-801. This suggests PV-NMDARs as the site of the psychosis-inducing action of MK-801. In contrast to this hypothesis, we show here that Grin1ΔPV mice are not protected against the effects of MK-801, but are in fact sensitized to many of them. Compared with control animals, Grin1ΔPVmice injected with MK-801 show increased stereotypy and pronounced catalepsy, which confound the locomotor readout. Furthermore, in Grin1ΔPVmice, MK-801 induced medial-prefrontal delta (4 Hz) oscillations, and impaired performance on tests of motor coordination, working memory and sucrose preference, even at lower doses than in wild-type controls. We also found that untreated Grin1ΔPVmice are largely normal across a wide range of cognitive functions, including attention, cognitive flexibility and various forms of short-term memory. Taken together these results argue against PV-specific NMDAR hypofunction as a key starting point of schizophrenia pathophysiology, but support a model where NMDAR hypofunction in multiple cell types contribute to the disease. PMID:27070406

Changes in cortical N-methyl-D-aspartate receptors and post-synaptic density protein 95 in schizophrenia, mood disorders and suicide.

PubMed

Dean, Brian; Gibbons, Andrew S; Boer, Simone; Uezato, Akihito; Meador-Woodruff, James; Scarr, Elizabeth; McCullumsmith, Robert E

2016-03-01

In humans, depending on dose, blocking the N-methyl-D-aspartate receptor (NMDAR) with ketamine can cause psychomimetic or antidepressant effects. The overall outcome for drugs such as ketamine depends on dose and the number of its available binding sites in the central nervous system, and to understand something of the latter variable we measure NMDAR in the frontal pole, dorsolateral prefrontal, anterior cingulate and parietal cortices from people with schizophrenia, bipolar disorder, major depressive disorders and age/sex matched controls. We measured levels of NMDARs (using [(3)H]MK-801 binding) and NMDAR sub-unit mRNAs (GRINs: using in situ hybridisation) as well as post-synaptic density protein 95 (anterior cingulate cortex only; not major depressive disorders: an NMDAR post-synaptic associated protein) in bipolar disorder, schizophrenia and controls. Compared to controls, levels of NMDAR were lower in the outer laminae of the dorsolateral prefrontal cortex (-17%, p = 0.01) in people with schizophrenia. In bipolar disorder, levels of NMDAR binding (laminae IV-VI; -19%, p < 0.01) and GRIN2C mRNA (laminae I-VI; -27%, p < 0.05) were lower in the anterior cingulate cortex and NMDAR binding was lower in the outer lamina IV of the dorsolateral prefrontal cortex (-19%, p < 0.01). In major depressive disorders, levels of GRIN2D mRNA were higher in frontal pole (+22%, p < 0.05). In suicide completers, levels of GRIN2B mRNA were higher in parietal cortex (+20%, p < 0.01) but lower (-35%, p = 0.02) in dorsolateral prefrontal cortex while post-synaptic density protein 95 was higher (+26%, p < 0.05) in anterior cingulate cortex. These data suggest that differences in cortical NMDAR expression and post-synaptic density protein 95 are present in psychiatric disorders and suicide completion and may contribute to different responses to ketamine. © The Royal Australian and New Zealand College of Psychiatrists 2015.

Effects of maternally exposed coloring food additives on receptor expressions related to learning and memory in rats.

PubMed

Ceyhan, Betul Mermi; Gultekin, Fatih; Doguc, Duygu Kumbul; Kulac, Esin

2013-06-01

Exposure to artificial food colors and additives (AFCAs) has been implicated in the induction and severity of some childhood behavioral and learning disabilities. N-methyl-D-aspartate receptors (NMDARs) and nicotinic acetylcholine receptors (nACHRs) are thought to be effective in the learning and memory-generating process. In this study, we investigated the effects of intrauterine exposure to AFCAs on subunit concentrations of NMDARs and nAChRs isoforms in rats. We administered a mixture of AFCAs (Eritrosin, Ponceau 4R, Allura Red AC, Sunset Yellow FCF, Tartrazin, Amaranth, Brilliant Blue, Azorubin and Indigotin) to female rats before and during gestation. The concentration of NR2A and NR2B subunits and nAChR α7, α4β2 isoforms in their offspring's hippocampi were measured by Western Blotting. Expressions of NR2B and nAChR β2 were significantly increased (17% and 6.70%, respectively), whereas expression of nAChR α4 was significantly decreased (5.67%) in male experimental group compared to the male control group (p<0.05). In the female experimental group, AFCAs caused a 14% decrease in NR2B expression when compared to the female control group (p<0.05). Our results indicate that exposure to AFCAs during the fetal period may lead to alterations in expressions of NMDARs and nAChRs in adulthood. These alterations were different between male and female genders. Copyright © 2013 Elsevier Ltd. All rights reserved.

The N-Methyl-D-Aspartate Receptor in Heart Development: A Gene Knockdown Model Using siRNA

PubMed Central

Lie, Octavian V.; Bennett, Gregory D.; Rosenquist, Thomas H

2009-01-01

Antagonists of the N-methyl-D-aspartate receptor (NMDAR) may disrupt the development of the cardiac neural crest (CNC) and contribute to conotruncal heart defects. To test this interaction, a loss-of-function model was generated using small interfering RNAs (siRNA) directed against the critical NR1-subunit of this receptor in avian embryos. The coding sequence of the chicken NR1-gene and predicted protein sequences were characterized and found to be homologous with other vertebrate species. Analysis of its spatiotemporal expression demonstrated its expression within the neural tube at pre-migratory CNC sites. siRNA targeted to the NR1-mRNA in pre-migratory CNC lead to a significant decrease in NR1 protein expression. However, embryo survival and heart development were not adversely affected. These results indicate that the CNC may function normally in the absence of functional NMDAR, and that NMDAR antagonists may have a complex impact upon the CNC that transcends impairment of a single receptor type. PMID:19737608

Investigation of antidepressant-like and anxiolytic-like actions and cognitive and motor side effects of four N-methyl-D-aspartate receptor antagonists in mice.

PubMed

Refsgaard, Louise K; Pickering, Darryl S; Andreasen, Jesper T

2017-02-01

Evidence suggests that N-methyl-D-aspartate receptor (NMDAR) antagonists could be efficacious in treating depression and anxiety, but side effects constitute a challenge. This study evaluated the antidepressant-like and anxiolytic-like actions, and cognitive and motor side effects of four NMDAR antagonists. MK-801, ketamine, S-ketamine, RO 25-6981 and the positive control, citalopram, were tested for antidepressant-like and anxiolytic-like effects in mice using the forced-swim test, the elevated zero maze and the novelty-induced hypophagia test. Side effects were assessed using a locomotor activity test, the modified Y-maze and the rotarod test. All compounds increased swim distance in the forced-swim test. In the elevated zero maze, the GluN2B subtype-selective RO 25-6981 affected none of the measured parameters, whereas all other compounds showed anxiolytic-like effects. In the novelty-induced hypophagia test, citalopram and MK-801 showed anxiogenic-like action. All NMDAR antagonists induced hyperactivity. The high doses of ketamine and MK-801 impaired performance in the modified Y-maze test, whereas S-ketamine and RO 25-6891 showed no effects in this test. Only MK-801 impaired rotarod performance. The study supports that NMDARs could be a possible therapeutic target for treating depression and anxiety. However, selective antagonism of GluN2B subunit-containing NMDARs showed no effect on anxiety-like behaviours in this study.

Sexually dimorphic effects of NMDA receptor antagonism on brain-pituitary-gonad axis development in the platyfish

NASA Technical Reports Server (NTRS)

Flynn, Katherine M.; Miller, Shelly A.; Sower, Stacia A.; Schreibman, Martin P.

2002-01-01

The N-methyl-D-aspartate glutamate receptor (NMDAR) is found in hypothalamic nuclei involved in the regulation of reproduction in several species of mammals and fishes. NMDAR is believed to affect reproductive development and function by regulating gonadotropin releasing hormone (GnRH)-producing cells. These pathways are likely to be sexually dimorphic, as are several other neurotransmitter systems involved in reproductive function. In this report, male and female platyfish received intraperitoneal injections of 0, 5, 10, 20, 40 or 60 microg/g body wt. of the non-competitive NMDAR antagonist MK-801. Injections began at 6 weeks of age and continued thrice weekly until control animals reached puberty, as evidenced by anal fin maturation. The percent of pubescent animals was significantly affected by sex and treatment, with fewer MK-801-injected females in puberty than control females at each dose (P<0.001), and fewer pubescent females than males at 10, 20 and 40 microg/g (P<0.05). There were no MK-801-related effects in males. Histological analyses revealed typical immature gonads and pituitary glands in treated females, and typical mature morphology in control females and all males. Immunocytochemical distribution of the R1 subunit of the NMDAR within the brain-pituitary-gonad (BPG) axis was limited to GnRH-containing brain cells in all animals; however, NMDAR1 distribution was in an immature pattern in treated females and a mature pattern in all others. Neural concentrations of GnRH were unaffected by MK-801 treatment in both sexes. These data suggest that in the platyfish, NMDAR influence on reproductive development is sexually dimorphic and occurs at, or above, the level of GnRH-containing cells of the BPG axis.

Immunolocalization of NR1, NR2A, and PSD-95 in rat hippocampal subregions during postnatal development.

PubMed

Ling, Wei; Chang, Lirong; Song, Yizhi; Lu, Tao; Jiang, Yuhua; Li, Youxiang; Wu, Yan

2012-05-01

Although the expression of NMDARs and synaptic-associated proteins has been widely studied, the temporospatial distribution of NMDAR subunits and synaptic proteins in different hippocampal subregions during postnatal development still lacks detailed information, and the relationship between NR1 or NR2 subunits and PSD-95 family proteins is controversial. In this study, we used immunofluorescent staining to assess NR1 or NR2A and PSD-95 expressions and the relationship between them in CA1, CA3, and DG of rat hippocampus on postnatal (P) days: P0, P4, P7, P10, P14, P21, P28, P56. The results showed that from P0 to P56, NR1, NR2A, and PSD-95 expressions increased gradually, and the time points of their expression peak differed in CA1, CA3, and DG during postnatal development. Interestingly, although the expression of PSD-95 was positively correlated to both NR1 and NR2A, the NR1 and PSD-95 coexpressed puncta were greatest in CA3, while NR2A and PSD-95 coexpressed puncta were greatest in CA1, compared to other subregions. Surprisingly, at P21, among different strata of CA1, the area of highest expression of NR2A was dramatically changed from stratum pyramidale to stratum polymorphum and stratum moleculare, and returned to stratum pyramidale gradually on the later observed days again, indicating that P21 may be one critical timepoint during postnatal development in CA1. The specific temporospatial distribution pattern of NR1, NR2A, and PSD-95 might be related to the different physiological functions during postnatal development. Discovering the alteration of the relationship between PSD-95 and NMDAR subunits expression may be helpful for understanding mechanisms and therapy of neurodegenerative diseases. Copyright © 2011 Elsevier GmbH. All rights reserved.

Adenylyl Cyclase 1 Is Required for Ethanol-Induced Locomotor Sensitization and Associated Increases in NMDA Receptor Phosphorylation and Function in the Dorsal Medial Striatum

PubMed Central

Bosse, Kelly E.; Oginsky, Max F.; Susick, Laura L.; Ramalingam, Sailesh; Ferrario, Carrie R.

2017-01-01

Neuroadaptive responses to chronic ethanol, such as behavioral sensitization, are associated with N-methyl-D-aspartate receptor (NMDAR) recruitment. Ethanol enhances GluN2B-containing NMDAR function and phosphorylation (Tyr-1472) of the GluN2B-NMDAR subunit in the dorsal medial striatum (DMS) through a protein kinase A (PKA)–dependent pathway. Ethanol-induced phosphorylation of PKA substrates is partially mediated by calcium-stimulated adenylyl cyclase 1 (AC1), which is enriched in the dorsal striatum. As such, AC1 is poised as an upstream modulator of ethanol-induced DMS neuroadaptations that promote drug responding, and thus represents a therapeutic target. Our hypothesis is that loss of AC1 activity will prevent ethanol-induced locomotor sensitization and associated DMS GluN2B-NMDAR adaptations. We evaluated AC1’s contribution to ethanol-evoked locomotor responses and DMS GluN2B-NMDAR phosphorylation and function using AC1 knockout (AC1KO) mice. Results were mechanistically validated with the AC1 inhibitor, NB001. Acute ethanol (2.0 g/kg) locomotor responses in AC1KO and wild-type (WT) mice pretreated with NB001 (10 mg/kg) were comparable to WT ethanol controls. However, repeated ethanol treatment (10 days, 2.5 g/kg) failed to produce sensitization in AC1KO or NB001 pretreated mice, as observed in WT ethanol controls, following challenge exposure (2.0 g/kg). Repeated exposure to ethanol in the sensitization procedure significantly increased pTyr-1472 GluN2B levels and GluN2B-containing NMDAR transmission in the DMS of WT mice. Loss of AC1 signaling impaired ethanol-induced increases in DMS pGluN2B levels and NMDAR-mediated transmission. Together, these data support a critical and specific role for AC1 in striatal signaling that mediates ethanol-induced behavioral sensitization, and identify GluN2B-containing NMDARs as an important AC1 target. PMID:28838956

Ghrelin upregulates the phosphorylation of the GluN2B subunit of the NMDA receptor by activating GHSR1a and Fyn in the rat hippocampus.

PubMed

Berrout, Liza; Isokawa, Masako

2018-01-01

Ghrelin and its receptor GHSR1a have been shown to exert numerous physiological functions in the brain, in addition to the well-established orexigenic role in the hypothalamus. Earlier work indicated that ghrelin stimulated the phosphorylation of the GluN1 subunit of the NMDA receptor (NMDAR) and enhanced synaptic transmission in the hippocampus. In the present study, we report that the exogenous application of ghrelin increased GluN2B phosphorylation. This increase was independent of GluN2B subunit activity or NMDAR channel activity. However, it depended on the activation of GHSR1a and Fyn as it was blocked by D-Lys3-GHRP-6 and PP2, respectively. Inhibitors for G-protein-regulated second messengers, such as Rp-cAMP, H89, TBB, ryanodine, and thapsigargin, unexpectedly enhanced GluN2B phosphorylation, suggesting that cAMP, PKA, casein kinase II, and cytosolic calcium signaling may oppose to the effect of ghrelin on the phosphorylation of GluN2B. Our findings suggest that 1) GluN2B is likely a molecular target of ghrelin and GHSR1a-driven signaling cascades, and 2) the ghrelin-mediated phosphorylation of GluN2B depends on Fyn activation under complex negative regulation by other second messengers. Copyright © 2017 Elsevier B.V. All rights reserved.

Cortical GluN2B deletion attenuates punished suppression of food reward-seeking.

PubMed

Radke, Anna K; Nakazawa, Kazu; Holmes, Andrew

2015-10-01

Compulsive behavior, which is a hallmark of psychiatric disorders such as addiction and obsessive-compulsive disorder, engages corticostriatal circuits. Previous studies indicate a role for corticostriatal N-methyl-D-aspartate receptors (NMDARs) in mediating compulsive-like responding for drugs of abuse, but the specific receptor subunits controlling reward-seeking in the face of punishment remain unclear. The current study assessed the involvement of corticostriatal GluN2B-containing NMDARs in measures of persistent and punished food reward-seeking. Mice with genetic deletion of GluN2B in one of three distinct neuronal populations, cortical principal neurons, forebrain interneurons, or striatal medium spiny neurons, were tested for (1) sustained food reward-seeking when reward was absent, (2) reward-seeking under a progressive ratio schedule of reinforcement, and (3) persistent reward-seeking after a footshock punishment. Mutant mice with genetic deletion of GluN2B in cortical principal neurons demonstrated attenuated suppression of reward-seeking during punishment. These mice performed normally on other behavioral measures, including an assay for pain sensitivity. Mutants with interneuronal or striatal GluN2B deletions were normal on all behavioral assays. Current findings offer novel evidence that loss of GluN2B-containing NMDARs expressed on principal neurons in the cortex results in reduced punished food reward-seeking. These data support the involvement of GluN2B subunit in cortical circuits regulating cognitive flexibility in a variety of settings, with implications for understanding the basis of inflexible behavior in neuropsychiatric disorders including obsessive-compulsive disorders (OCD) and addictions.

Intra-hippocampal D-cycloserine rescues decreased social memory, spatial learning reversal, and synaptophysin levels in aged rats.

PubMed

Portero-Tresserra, Marta; Martí-Nicolovius, Margarita; Tarrés-Gatius, Mireia; Candalija, Ana; Guillazo-Blanch, Gemma; Vale-Martínez, Anna

2018-05-01

Aging is characterized by a decrease in N-methyl-D-aspartate receptors (NMDARs) in the hippocampus, which might be one of the factors involved in the age-dependent cognitive decline. D-Cycloserine (DCS), a partial agonist of the NMDAR glycine recognition site, could improve memory deficits associated to neurodegenerative disorders and cognitive deficits observed in normal aging. The aim of the present study was to explore whether DCS would reverse age-dependent memory deficits and decreases in NMDA receptor subunits (GluN1, GluN2A, and GluN2B) and the presynaptic protein synaptophysin in Wistar rats. We investigated the effects of pre-training infusions of DCS (10 μg/hemisphere) in the ventral hippocampus on two hippocampal-dependent learning tasks, the social transmission of food preference (STFP), and the Morris water maze (MWM). The results revealed that infusions of DCS administered before the acquisition sessions rescued deficits in the STFP retention and MWM reversal learning in old rats. DCS also significantly increased the hippocampal levels of synaptophysin in old rats, which correlated with STFP and MWM performance in all tests. Moreover, although the levels of the GluN1 subunit correlated with the MWM acquisition and reversal, DCS did not enhance the expression of such synaptic protein. The present behavioral results support the role of DCS as a cognitive enhancer and suggest that enhancing the function of NMDARs and synaptic plasticity in the hippocampus may be related to improvement in social memory and spatial learning reversal in aged animals.

Endocytosis and recycling of AMPA receptors lacking GluR2/3.

PubMed

Biou, Virginie; Bhattacharyya, Samarjit; Malenka, Robert C

2008-01-22

Excitatory synapses in the mammalian brain contain two types of ligand-gated ion channels: AMPA receptors (AMPARs) and NMDA receptors (NMDARs). AMPARs are responsible for generating excitatory synaptic responses, whereas NMDAR activation triggers long-lasting changes in these responses by modulating the trafficking of AMPARs toward and away from synapses. AMPARs are tetramers composed of four subunits (GluR1-GluR4), which current models suggest govern distinct AMPAR trafficking behavior during synaptic plasticity. Here, we address the roles of GluR2 and GluR3 in controlling the recycling- and activity-dependent endocytosis of AMPARs by using cultured hippocampal neurons prepared from knockout (KO) mice lacking these subunits. We find that synapses and dendritic spines form normally in cells lacking GluR2/3 and that upon NMDAR activation, GluR2/3-lacking AMPARs are endocytosed in a manner indistinguishable from GluR2-containing AMPARs in wild-type (WT) neurons. AMPARs lacking GluR2/3 also recycle to the plasma membrane identically to WT AMPARs. However, because of their permeability to calcium, GluR2-lacking but not WT AMPARs exhibited robust internalization throughout the dendritic tree in response to AMPA application. Dendritic endocytosis of AMPARs also was observed in GABAergic neurons, which express a high proportion of GluR2-lacking AMPARs. These results demonstrate that GluR2 and GluR3 are not required for activity-dependent endocytosis of AMPARs and suggest that the most important property of GluR2 in the context of AMPAR trafficking may be its influence on calcium permeability.

Mice with reduced NMDA receptor expression: more consistent with autism than schizophrenia?

PubMed

Gandal, M J; Anderson, R L; Billingslea, E N; Carlson, G C; Roberts, T P L; Siegel, S J

2012-08-01

Reduced NMDA-receptor (NMDAR) function has been implicated in the pathophysiology of neuropsychiatric disease, most strongly in schizophrenia but also recently in autism spectrum disorders (ASD). To determine the direct contribution of NMDAR dysfunction to disease phenotypes, a mouse model with constitutively reduced expression of the obligatory NR1 subunit has been developed and extensively investigated. Adult NR1(neo-/-) mice show multiple abnormal behaviors, including reduced social interactions, locomotor hyperactivity, self-injury, deficits in prepulse inhibition (PPI) and sensory hypersensitivity, among others. Whereas such phenotypes have largely been interpreted in the context of schizophrenia, these behavioral abnormalities are rather non-specific and are frequently present across models of diseases characterized by negative symptom domains. This study investigated auditory electrophysiological and behavioral paradigms relevant to autism, to determine whether NMDAR hypofunction may be more consistent with adult ASD-like phenotypes. Indeed, transgenic mice showed behavioral deficits relevant to all core ASD symptoms, including decreased social interactions, altered ultrasonic vocalizations and increased repetitive behaviors. NMDAR disruption recapitulated clinical endophenotypes including reduced PPI, auditory-evoked response N1 latency delay and reduced gamma synchrony. Auditory electrophysiological abnormalities more closely resembled those seen in clinical studies of autism than schizophrenia. These results suggest that NMDAR hypofunction may be associated with a continuum of neuropsychiatric diseases, including schizophrenia and autism. Neural synchrony abnormalities suggest an imbalance of glutamatergic and GABAergic coupling and may provide a target, along with behavioral phenotypes, for preclinical screening of novel therapeutics. © 2012 The Authors. Genes, Brain and Behavior © 2012 Blackwell Publishing Ltd and International Behavioural and Neural Genetics Society.

Methylphenidate Exerts Dose-Dependent Effects on Glutamate Receptors and Behaviors

PubMed Central

Cheng, Jia; Xiong, Zhe; Duffney, Lara J.; Wei, Jing; Liu, Aiyi; Liu, Sihang; Chen, Guo-Jun; Yan, Zhen

2014-01-01

Background Methylphenidate (MPH), a psychostimulant drug for the treatment of attention-deficit hyperactivity disorder (ADHD), produces the effects of increasing alertness and improving attention, while its misuse has been associated with an increased risk of aggression and psychosis. In this study, we sought to determine the molecular mechanism underlying the complex actions of MPH. Methods Adolescent (4-week-old) rats were given one injection of MPH at different doses. The impact of MPH on glutamatergic signaling in pyramidal neurons of prefrontal cortex (PFC) was measured. MPH-induced behavioral changes were also examined in parallel. Results We found that administration of low-dose (0.5 mg/kg) MPH selectively potentiated NMDAR-mediated excitatory synaptic currents (EPSCs) via adrenergic receptor activation, while the high-dose (10 mg/kg) MPH suppressed both NMDAR- and AMPAR-EPSCs. The dual effects of MPH on EPSCs were associated with bi-directional changes in the surface level of glutamate receptor subunits. Behavioral tests also indicated that low-dose MPH facilitated the PFC-mediated temporal order recognition memory (TORM) and attention, while animals injected with high-dose MPH exhibited significantly elevated locomotive activity. Inhibiting the function of SNAP-25, a key SNARE proteins involved in NMDAR exocytosis, blocked the increase of NMDAR-EPSC by low-dose MPH. In animals exposed to repeated stress, administration of low-dose MPH effectively restored NMDAR function and TORM via a mechanism dependent on SNAP-25. Conclusions Our results have provided a potential mechanism underlying the cognitive enhancing effects of low-dose MPH, as well as the psychosis-inducing effects of high-dose MPH. PMID:24832867

Glycine triggers a non-ionotropic activity of GluN2A-containing NMDA receptors to confer neuroprotection.

PubMed

Hu, Rong; Chen, Juan; Lujan, Brendan; Lei, Ruixue; Zhang, Mi; Wang, Zefen; Liao, Mingxia; Li, Zhiqiang; Wan, Yu; Liu, Fang; Feng, Hua; Wan, Qi

2016-10-03

Ionotropic activation of NMDA receptors (NMDARs) requires agonist glutamate and co-agonist glycine. Here we show that glycine enhances the activation of cell survival-promoting kinase Akt in cultured cortical neurons in which both the channel activity of NMDARs and the glycine receptors are pre-inhibited. The effect of glycine is reduced by shRNA-mediated knockdown of GluN2A subunit-containing NMDARs (GluN2ARs), suggesting that a non-ionotropic activity of GluN2ARs mediates glycine-induced Akt activation. In support of this finding, glycine enhances Akt activation in HEK293 cells over-expressing GluN2ARs. The effect of glycine on Akt activation is sensitive to the antagonist of glycine-GluN1 binding site. As a functional consequence, glycine protects against excitotoxicity-induced neuronal death through the non-ionotropic activity of GluN2ARs and the neuroprotective effect is attenuated by Akt inhibition. Thus, this study reveals an unexpected role of glycine in eliciting a non-ionotropic activity of GluN2ARs to confer neuroprotection via Akt activation.

Memory Enhancement by Targeting Cdk5 Regulation of NR2B

PubMed Central

Plattner, Florian; Hernandéz, Adan; Kistler, Tara M.; Pozo, Karine; Zhong, Ping; Yuen, Eunice Y.; Tan, Chunfeng; Hawasli, Ammar H.; Cooke, Sam F.; Nishi, Akinori; Guo, Ailan; Wiederhold, Thorsten; Yan, Zhen; Bibb, James A.

2014-01-01

SUMMARY Many psychiatric and neurological disorders are characterized by learning and memory deficits, for which cognitive enhancement is considered a valid treatment strategy. The N-methyl-D-aspartate receptor (NMDAR) is a prime target for the development of cognitive enhancers due to its fundamental role in learning and memory. In particular, the NMDAR subunit NR2B improves synaptic plasticity and memory when over-expressed in neurons. However, NR2B regulation is not well understood and no therapies potentiating NMDAR function have been developed. Here, we show that serine 1116 of NR2B is phosphorylated by cyclin-dependent kinase 5 (Cdk5). Cdk5-dependent NR2B phosphorylation is regulated by neuronal activity and controls the receptor’s cell surface expression. Disrupting NR2B-Cdk5 interaction using a small interfering peptide (siP) increases NR2B surface levels, facilitates synaptic transmission, and improves memory formation in vivo. Our results reveal a novel regulatory mechanism critical to NR2B function that can be targeted for the development of cognitive enhancers. PMID:24607229

Glycine triggers a non-ionotropic activity of GluN2A-containing NMDA receptors to confer neuroprotection

PubMed Central

Hu, Rong; Chen, Juan; Lujan, Brendan; Lei, Ruixue; Zhang, Mi; Wang, Zefen; Liao, Mingxia; Li, Zhiqiang; Wan, Yu; Liu, Fang; Feng, Hua; Wan, Qi

2016-01-01

Ionotropic activation of NMDA receptors (NMDARs) requires agonist glutamate and co-agonist glycine. Here we show that glycine enhances the activation of cell survival-promoting kinase Akt in cultured cortical neurons in which both the channel activity of NMDARs and the glycine receptors are pre-inhibited. The effect of glycine is reduced by shRNA-mediated knockdown of GluN2A subunit-containing NMDARs (GluN2ARs), suggesting that a non-ionotropic activity of GluN2ARs mediates glycine-induced Akt activation. In support of this finding, glycine enhances Akt activation in HEK293 cells over-expressing GluN2ARs. The effect of glycine on Akt activation is sensitive to the antagonist of glycine-GluN1 binding site. As a functional consequence, glycine protects against excitotoxicity-induced neuronal death through the non-ionotropic activity of GluN2ARs and the neuroprotective effect is attenuated by Akt inhibition. Thus, this study reveals an unexpected role of glycine in eliciting a non-ionotropic activity of GluN2ARs to confer neuroprotection via Akt activation. PMID:27694970

Suppressing aberrant GluN3A expression rescues NMDA receptor dysfunction, synapse loss and motor and cognitive decline in Huntington's disease models

PubMed Central

Marco, Sonia; Giralt, Albert; Petrovic, Milos M.; Pouladi, Mahmoud A.; Martínez-Turrillas, Rebeca; Martínez-Hernández, José; Kaltenbach, Linda S.; Torres-Peraza, Jesús; Graham, Rona K.; Watanabe, Masahiko; Luján, Rafael; Nakanishi, Nobuki; Lipton, Stuart A.; Lo, Donald C.; Hayden, Michael R.; Alberch, Jordi; Wesseling, John F.

2013-01-01

Huntington's disease is caused by an expanded polyglutamine repeat in huntingtin (Htt), but the pathophysiological sequence of events that trigger synaptic failure and neuronal loss are not fully understood. Alterations in NMDA-type glutamate receptors (NMDARs) have been implicated, yet it remains unclear how the Htt mutation impacts NMDAR function and direct evidence for a causative role is missing. Here we show that mutant Htt re-directs an intracellular store of juvenile NMDARs to the surface of striatal neurons by sequestering and disrupting the subcellular localization of the GluN3A subunit-specific endocytic adaptor PACSIN1. Overexpressing GluN3A in wild-type striatum mimicked the synapse loss observed in Huntington's disease mouse models, whereas genetic deletion of GluN3A prevented synapse degeneration, ameliorated motor and cognitive decline, and reduced striatal atrophy and neuronal loss in the YAC128 model. Furthermore, GluN3A deletion corrected the abnormally enhanced NMDAR currents, which have been linked to cell death in Huntington's disease and other neurodegenerative conditions. Our findings reveal an early pathogenic role of GluN3A dysregulation in Huntington's disease, and suggest that therapies targeting GluN3A or pathogenic Htt-PACSIN1 interactions might prevent or delay disease progression. PMID:23852340

Sexually dimorphic development and binding characteristics of NMDA receptors in the brain of the platyfish

NASA Technical Reports Server (NTRS)

Flynn, K. M.; Schreibman, M. P.; Yablonsky-Alter, E.; Banerjee, S. P.

1999-01-01

This study investigated age- and gender-specific variations in properties of the glutamate N-methyl-d-aspartate receptor (NMDAR) in a freshwater teleost, the platyfish (Xiphophorus maculatus). Prior localization of the immunoreactive (ir)-R1 subunit of the NMDAR protein (R1) in cells of the nucleus olfactoretinalis (NOR), a primary gonadotropin-releasing hormone (GnRH)-containing brain nucleus in the platyfish, suggests that NMDAR, as in mammals, is involved in modulation of the platyfish brain-pituitary-gonad (BPG) axis. The current study shows that the number of cells in the NOR displaying ir-R1 is significantly increased in pubescent and mature female platyfish when compared to immature and senescent animals. In males, there is no significant change in ir-R1 expression in the NOR at any time in their lifespan. The affinity of the noncompetitive antagonist ((3)H)MK-801 for the NMDAR is significantly increased in pubescent females while maximum binding of ((3)H)MK-801 to the receptor reaches a significant maximum in mature females. In males, both MK-801 affinity and maximum binding remain unchanged throughout development. This is the first report of gender differences in the association of NMDA receptors with neuroendocrine brain areas during development. It is also the first report to suggest NMDA receptor involvement in the development of the BPG axis in a nonmammalian vertebrate. Copyright 1999 Academic Press.

Intrathecal injection of the peptide myr-NR2B9c attenuates bone cancer pain via perturbing N-methyl-D-aspartate receptor-PSD-95 protein interactions in mice.

PubMed

Liu, Yue; Cui, Xinlong; Sun, Yu-E; Yang, Xuli; Ni, Kun; Zhou, Yu; Ma, Zhengliang; Gu, Xiaoping

2014-06-01

N-methyl-D-aspartate receptor (NMDARs)-dependent central sensitization plays an important role in cancer pain. Binding of NMDAR subunit 2B (NR2B) by postsynaptic density protein-95 (PSD-95) can couple NMDAR activity to intracellular enzymes, such as neuronal nitric oxide synthase (nNOS), facilitate downstream signaling pathways, and modulate NMDAR stability, contributing to synaptic plasticity. In this study, we investigated whether perturbing the specific interaction between spinal NR2B-containing NMDAR and PSD-95, using a peptide-mimetic strategy, could attenuate bone cancer-related pain behaviors. Osteosarcoma cells were implanted into the intramedullary space of the right femurs of C3H/HeJ mice to induce progressive bone cancer-related pain behaviors. Western blotting was applied to examine the expression of spinal phospho-Tyr1472 NR2B, nNOS, and PSD-95. We further investigated the effects of intrathecal injection of the mimetic peptide Myr-NR2B9c, which competitively disrupts the interaction between PSD-95 and NR2B, on nociceptive behaviors and on the upregulation of phospho-Tyr1472 NR2B, nNOS, and PSD-95 associated with bone cancer pain in the spinal cord. Inoculation of osteosarcoma cells induced progressive bone cancer pain and resulted in a significant upregulation of phospho-Tyr1472 NR2B, nNOS, and PSD-95. Intrathecal administration of Myr-NR2B9c attenuated bone cancer-evoked mechanical allodynia, thermal hyperalgesia, and reduced spinal phospho-Tyr1472 NR2B, nNOS, and PSD-95 expression. Intrathecal administration of Myr-NR2B9c reduced bone cancer pain. Internalization of spinal NR2B and dissociation NR2B-containing NMDARs activation from downstream nNOS signaling may contribute to the analgesic effects of Myr-NR2B9c. This approach may circumvent the negative consequences associated with blocking NMDARs, and may be a novel strategy for the treatment of bone cancer pain.

Juvenile treatment with a novel mGluR2 agonist/mGluR3 antagonist compound, LY395756, reverses learning deficits and cognitive flexibility impairments in adults in a neurodevelopmental model of schizophrenia.

PubMed

Li, Meng-Lin; Gulchina, Yelena; Monaco, Sarah A; Xing, Bo; Ferguson, Brielle R; Li, Yan-Chun; Li, Feng; Hu, Xi-Quan; Gao, Wen-Jun

2017-04-01

Schizophrenia (SCZ) is a neurodevelopmental psychiatric disorder, in which cognitive function becomes disrupted at early stages of the disease. Although the mechanisms underlying cognitive impairments remain unclear, N-methyl-D-aspartate receptors (NMDAR) hypofunctioning in the prefrontal cortex (PFC) has been implicated. Moreover, cognitive symptoms in SCZ are usually unresponsive to treatment with current antipsychotics and by onset, disruption of the dopamine system, not NMDAR hypofunctioning, dominates the symptoms. Therefore, treating cognitive deficits at an early stage is a realistic approach. In this study, we tested whether an early treatment targeting mGluR2 would be effective in ameliorating cognitive impairments in the methylazoxymethanol acetate (MAM) model of SCZ. We investigated the effects of an mGluR2 agonist/mGluR3 antagonist, LY395756 (LY39), on the NMDAR expression and function in juveniles, as well as cognitive deficits in adult rats after juvenile treatment. We found that gestational MAM exposure induced a significant decrease in total protein levels of the NMDAR subunit, NR2B, and a significant increase of pNR2BTyr1472 in the juvenile rat PFC. Treatment with LY39 in juvenile MAM-exposed rats effectively recovered the disrupted NMDAR expression. Furthermore, a subchronic LY39 treatment in juvenile MAM-exposed rats also alleviated the learning deficits and cognitive flexibility impairments when tested with a cross-maze based set-shifting task in adults. Therefore, our study demonstrates that targeting dysfunctional NMDARs with an mGluR2 agonist during the early stage of SCZ could be an effective strategy in preventing the development and progression in addition to ameliorating cognitive impairments of SCZ. Copyright © 2017 Elsevier Inc. All rights reserved.

Adenosine A2A receptors are required for glutamate mGluR5- and dopamine D1 receptor-evoked ERK1/2 phosphorylation in rat hippocampus: involvement of NMDA receptor.

PubMed

Krania, Paraskevi; Dimou, Eleni; Bantouna, Maria; Kouvaros, Stylianos; Tsiamaki, Eirini; Papatheodoropoulos, Costas; Sarantis, Konstantinos; Angelatou, Fevronia

2018-05-01

Interaction between mGluR5 and NMDA receptors (NMDAR) is vital for synaptic plasticity and cognition. We recently demonstrated that stimulation of mGluR5 enhances NMDAR responses in hippocampus by phosphorylating NR2B(Tyr1472) subunit, and this reaction was enabled by adenosine A 2A receptors (A 2A R) (J Neurochem, 135, 2015, 714). In this study, by using in vitro phosphorylation and western blot analysis in hippocampal slices of male Wistar rats, we show that mGluR5 stimulation or mGluR5/NMDARs co-stimulation synergistically activate ERK1/2 signaling leading to c-Fos expression. Interestingly, both reactions are under the permissive control of endogenous adenosine acting through A 2A Rs. Moreover, mGluR5-mediated ERK1/2 phosphorylation depends on NMDAR, which however exhibits a metabotropic way of function, since no ion influx through its ion channel is required. Furthermore, our results demonstrate that mGluR5 and mGluR5/NMDAR-evoked ERK1/2 activation correlates well with the mGluR5/NMDAR-evoked NR2B(Tyr1472) phosphorylation, since both phenomena coincide temporally, are Src dependent, and are both enabled by A 2A Rs. This indicates a functional involvement of NR2B(Tyr1472) phosphorylation in the ERK1/2 activation. Our biochemical results are supported by electrophysiological data showing that in CA1 region of hippocampus, the theta burst stimulation (TBS)-induced long-term potentiation coincides temporally with an increase in ERK1/2 activation and both phenomena are dependent on the tripartite A 2A , mGlu5, and NMDARs. Furthermore, we show that the dopamine D1 receptors evoked ERK1/2 activation as well as the NR2B(Tyr1472) phosphorylation are also regulated by endogenous adenosine and A 2A Rs. In conclusion, our results highlight the A 2A Rs as a crucial regulator not only for NMDAR responses, but also for regulating ERK1/2 signaling and its downstream pathways, leading to gene expression, synaptic plasticity, and memory consolidation. © 2017 International Society for Neurochemistry.

Sociability Deficits and Altered Amygdala Circuits in Mice Lacking Pcdh10, an Autism Associated Gene.

PubMed

Schoch, Hannah; Kreibich, Arati S; Ferri, Sarah L; White, Rachel S; Bohorquez, Dominique; Banerjee, Anamika; Port, Russell G; Dow, Holly C; Cordero, Lucero; Pallathra, Ashley A; Kim, Hyong; Li, Hongzhe; Bilker, Warren B; Hirano, Shinji; Schultz, Robert T; Borgmann-Winter, Karin; Hahn, Chang-Gyu; Feldmeyer, Dirk; Carlson, Gregory C; Abel, Ted; Brodkin, Edward S

2017-02-01

Behavioral symptoms in individuals with autism spectrum disorder (ASD) have been attributed to abnormal neuronal connectivity, but the molecular bases of these behavioral and brain phenotypes are largely unknown. Human genetic studies have implicated PCDH10, a member of the δ2 subfamily of nonclustered protocadherin genes, in ASD. PCDH10 expression is enriched in the basolateral amygdala, a brain region implicated in the social deficits of ASD. Previous reports indicate that Pcdh10 plays a role in axon outgrowth and glutamatergic synapse elimination, but its roles in social behaviors and amygdala neuronal connectivity are unknown. We hypothesized that haploinsufficiency of Pcdh10 would reduce social approach behavior and alter the structure and function of amygdala circuits. Mice lacking one copy of Pcdh10 (Pcdh10 +/- ) and wild-type littermates were assessed for social approach and other behaviors. The lateral/basolateral amygdala was assessed for dendritic spine number and morphology, and amygdala circuit function was studied using voltage-sensitive dye imaging. Expression of Pcdh10 and N-methyl-D-aspartate receptor (NMDAR) subunits was assessed in postsynaptic density fractions of the amygdala. Male Pcdh10 +/- mice have reduced social approach behavior, as well as impaired gamma synchronization, abnormal spine morphology, and reduced levels of NMDAR subunits in the amygdala. Social approach deficits in Pcdh10 +/- male mice were rescued with acute treatment with the NMDAR partial agonist d-cycloserine. Our studies reveal that male Pcdh10 +/- mice have synaptic and behavioral deficits, and establish Pcdh10 +/- mice as a novel genetic model for investigating neural circuitry and behavioral changes relevant to ASD. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Ionotropic glutamate receptors activate cell signaling in response to glutamate in Schwann cells.

PubMed

Campana, Wendy M; Mantuano, Elisabetta; Azmoon, Pardis; Henry, Kenneth; Banki, Michael A; Kim, John H; Pizzo, Donald P; Gonias, Steven L

2017-04-01

In the peripheral nervous system, Schwann cells (SCs) demonstrate surveillance activity, detecting injury and undergoing trans -differentiation to support repair. SC receptors that detect peripheral nervous system injury remain incompletely understood. We used RT-PCR to profile ionotropic glutamate receptor expression in cultured SCs. We identified subunits required for assembly of N -methyl-d-aspartic acid (NMDA) receptors (NMDA-Rs), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors, and kainate receptors. Treatment of SCs with 40-100 µM glutamate or with 0.5-1.0 µM NMDA robustly activated Akt and ERK1/2. The response was transient and bimodal; glutamate concentrations that exceeded 250 µM failed to activate cell signaling. Phosphoprotein profiling identified diverse phosphorylated proteins in glutamate-treated SCs in addition to ERK1/2 and Akt, including p70 S6-kinase, glycogen synthase kinase-3, ribosomal S6 kinase, c-Jun, and cAMP response element binding protein. Activation of SC signaling by glutamate was blocked by EGTA and dizocilpine and by silencing expression of the NMDA-R NR1 subunit. Phosphoinositide 3-kinase/PI3K functioned as an essential upstream activator of Akt and ERK1/2 in glutamate-treated SCs. When glutamate or NMDA was injected directly into crush-injured rat sciatic nerves, ERK1/2 phosphorylation was observed in myelinated and nonmyelinating SCs. Glutamate promoted SC migration by a pathway that required PI3K and ERK1/2. These results identified ionotropic glutamate receptors and NMDA-Rs, specifically, as potentially important cell signaling receptors in SCs.-Campana, W. M., Mantuano, E., Azmoon, P., Henry, K., Banki, M. A., Kim, J. H., Pizzo, D. P., Gonias, S. L. Ionotropic glutamate receptors activate cell signaling in response to glutamate in Schwann cells. © FASEB.

Absent anti-N-methyl-D-aspartate receptor NR1a antibodies in herpes simplex virus encephalitis and varicella zoster virus infections.

PubMed

Berger, Benjamin; Pytlik, Maximilian; Hottenrott, Tilman; Stich, Oliver

2017-02-01

A 2012 report and subsequent case series described anti-N-methyl-D-aspartate receptor (NMDAR) antibodies in patients during the acute phase and relapse of herpes simplex virus 1 (HSV1) encephalitis (HSV1E). However, the prevalence of this phenomenon is unknown and systematic studies on other viral infections of the nervous system are missing. We retrospectively analyzed serial cerebrospinal fluid (CSF) and serum samples of consecutive patients treated for neurological HSV1, HSV2 and varicella zoster virus (VZV) infections in our tertiary care university hospital between 2003 and 2013 for the presence of antibodies directed against the NR1a subunit of the NMDAR using indirect immunofluorescence. In total, 88 patients with the following infections were identified through an electronic database search: HSV1 (24 with encephalitis), HSV2 (6 with meningitis, 3 with encephalitis and 1 with myelitis), or VZV (3 with meningitis, 33 with encephalitis, 17 with radiculitis and 1 with myelitis). Two patients with HSV1E and HSV2E, respectively, experienced a clinical relapse. Clinical follow-up was for up to 85 months, and repetitive serum and CSF analyses for up to 43 months. However, at no time did any of the 88 patients exhibit anti-NMDAR NR1a antibodies. In this study, we did not detect anti-NMDAR NR1a antibodies in serial CSF and serum samples of HSV1E patients or patients with other viral infections (HSV2 and VZV). However, the presence of antibodies directed against other epitopes of the NMDAR and other neuronal cell surface antigens cannot be excluded, necessitating further studies.

A role for D-aspartate oxidase in schizophrenia and in schizophrenia-related symptoms induced by phencyclidine in mice

PubMed Central

Errico, F; D'Argenio, V; Sforazzini, F; Iasevoli, F; Squillace, M; Guerri, G; Napolitano, F; Angrisano, T; Di Maio, A; Keller, S; Vitucci, D; Galbusera, A; Chiariotti, L; Bertolino, A; de Bartolomeis, A; Salvatore, F; Gozzi, A; Usiello, A

2015-01-01

Increasing evidence points to a role for dysfunctional glutamate N-methyl-D-aspartate receptor (NMDAR) neurotransmission in schizophrenia. D-aspartate is an atypical amino acid that activates NMDARs through binding to the glutamate site on GluN2 subunits. D-aspartate is present in high amounts in the embryonic brain of mammals and rapidly decreases after birth, due to the activity of the enzyme D-aspartate oxidase (DDO). The agonistic activity exerted by D-aspartate on NMDARs and its neurodevelopmental occurrence make this D-amino acid a potential mediator for some of the NMDAR-related alterations observed in schizophrenia. Consistently, substantial reductions of D-aspartate and NMDA were recently observed in the postmortem prefrontal cortex of schizophrenic patients. Here we show that DDO mRNA expression is increased in prefrontal samples of schizophrenic patients, thus suggesting a plausible molecular event responsible for the D-aspartate imbalance previously described. To investigate whether altered D-aspartate levels can modulate schizophrenia-relevant circuits and behaviors, we also measured the psychotomimetic effects produced by the NMDAR antagonist, phencyclidine, in Ddo knockout mice (Ddo−/−), an animal model characterized by tonically increased D-aspartate levels since perinatal life. We show that Ddo−/− mice display a significant reduction in motor hyperactivity and prepulse inhibition deficit induced by phencyclidine, compared with controls. Furthermore, we reveal that increased levels of D-aspartate in Ddo−/− animals can significantly inhibit functional circuits activated by phencyclidine, and affect the development of cortico–hippocampal connectivity networks potentially involved in schizophrenia. Collectively, the present results suggest that altered D-aspartate levels can influence neurodevelopmental brain processes relevant to schizophrenia. PMID:25689573

Dysregulated NMDA-Receptor Signaling Inhibits Long-Term Depression in a Mouse Model of Fragile X Syndrome.

PubMed

Toft, Anna Karina Hugger; Lundbye, Camilla Johanne; Banke, Tue G

2016-09-21

Fragile X syndrome (FXS) is a neurodevelopmental disease. It is one of the leading monogenic causes of intellectual disability among boys with most also displaying autism spectrum disorder traits. Here we investigated the role of NMDA receptors on mGluR-dependent long-term depression (mGluR-LTD), a key biomarker in the disease, at four different developmental stages. First, we applied the mGluR agonist 3,5-dihydroxyphenylglycine in the absence or presence of the NMDAR blocker, APV, hereby unmasking the NMDAR component in this process. As expected, in the presence of APV, we found more LTD in the mouse KO than in WT. This, however, was only observed in the p30-60 age group. At all other age groups tested, mGluR-LTD was almost identical between KO and WT. Interestingly, at p60, in the absence of APV, no or very little LTD was found in KO that was completely restored by application of APV. This suggests that the underlying cause of the enhanced mGluR-LTD in KO (at p30) is caused by dysregulated NMDAR signaling. To investigate this further, we next used NMDAR-subunit-specific antagonists. Inhibition of GluN2B, but not GluN2A, blocked mGluR-LTD only in WT. This was in contrast in the KO where blocking GluN2B rescued mGluR-LTD, suggesting GluN2B-containing NMDARs in the KO are hyperactive. Thus, these findings suggest strong involvement of GluN2B-containing-NMDARs in the pathophysiology of FXS and highlight a potential path for treatment for the disease. There is currently no cure for fragile X, although medications targeting specific FXS symptoms do exist. The FXS animal model, the Fmr1 knock-out mouse, has demonstrated an increased mGluR5-mediated long-term depression (LTD) leading to several clinical trials of mGluR5 inhibitors/modulators, yet all have failed. In addition, surprisingly little information exists about the possible role of other ion channels/receptors, including NMDA receptors (NMDAR), in mGluR-LTD. Here we focus on NMDARs and their regulation of mGluR-mediated LTD at different developmental stages using several different NMDAR blockers/antagonists. Our findings suggest dysregulated NMDARs in the pathophysiology of FXS leading to altered mGluR-mediated LTD. Together, these data will help to develop new drug candidates that could lead to reversal of the FXS phenotype. Copyright © 2016 the authors 0270-6474/16/369817-11$15.00/0.

Cognitive-enhancing effects of hydrolysate of polygalasaponin in SAMP8 mice*

PubMed Central

Xu, Pan; Xu, Shu-ping; Wang, Ke-zhu; Lu, Cong; Zhang, Hong-xia; Pan, Rui-le; Qi, Chang; Yang, Yan-yan; Li, Ying-hui; Liu, Xin-min

2016-01-01

Objectives: The aim of the study is to evaluate the cognitive-enhancing effects of hydrolysate of polygalasaponin (HPS) on senescence accelerate mouse P8 (SAMP8) mice, an effective Alzheimer’s disease (AD) model, and to research the relevant mechanisms. Methods: The cognitive-enhancing effects of HPS on SAMP8 mice were assessed using Morris water maze (MWM) and step-through passive avoidance tests. Then N-methyl-D-aspartate (NMDA) receptor subunit expression for both the cortex and hippocampus of mice was observed using Western blotting. Results: HPS (25 and 50 mg/kg) improved the escape rate and decreased the escape latency and time spent in the target quadrant for the SAMP8 mice in the MWM after oral administration of HPS for 10 d. Moreover, it decreased error times in the passive avoidance tests. Western blotting showed that HPS was able to reverse the levels of NMDAR1 and NMDAR2B expression in the cortex or hippocampus of model mice. Conclusions: The present study suggested that HPS can improve cognitive deficits in SAMP8 mice, and this mechanism might be associated with NMDA receptor (NMDAR)-related pathways. PMID:27381727

The Molecular Motor KIF21B Mediates Synaptic Plasticity and Fear Extinction by Terminating Rac1 Activation.

PubMed

Morikawa, Momo; Tanaka, Yosuke; Cho, Hyun-Soo; Yoshihara, Masaharu; Hirokawa, Nobutaka

2018-06-26

Fear extinction is a component of cognitive flexibility that is relevant for important psychiatric diseases, but its molecular mechanism is still largely elusive. We established mice lacking the kinesin-4 motor KIF21B as a model for fear extinction defects. Postsynaptic NMDAR-dependent long-term depression (LTD) is specifically impaired in knockouts. NMDAR-mediated LTD-causing stimuli induce dynamic association of KIF21B with the Rac1GEF subunit engulfment and cell motility protein 1 (ELMO1), leading to ELMO1 translocation out of dendritic spines and its sequestration in endosomes. This process may essentially terminate transient activation of Rac1, shrink spines, facilitate AMPAR endocytosis, and reduce postsynaptic strength, thereby forming a mechanistic link to LTD expression. Antagonizing ELMO1/Dock Rac1GEF activity by the administration of 4-[3'-(2″-chlorophenyl)-2'-propen-1'-ylidene]-1-phenyl-3,5-pyrazolidinedione (CPYPP) significantly reverses the knockout phenotype. Therefore, we propose that KIF21B-mediated Rac1 inactivation is a key molecular event in NMDAR-dependent LTD expression underlying cognitive flexibility in fear extinction. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

The regulatory effect of electro-acupuncture on the expression of NMDA receptors in a SCI rat model.

PubMed

Tu, Wen-Zhan; Chen, Wen-Ci; Xia, Wan; He, Rong; Hu, Jie; Jiang, Ming-Chen; Jiang, Song-He

2017-05-15

In early spinal cord injury (SCI), glutamate receptors, including N-methyl-d-aspartate (NMDA) receptors (NMDARs), are over-stimulated by excessively released glutamate. The enhanced activity of NMDARs may cause cell death by overloading calcium (Ca 2+ ) into cells based on their high permeability to Ca 2+ . Studies in SCI animals have shown that treatment with electro-acupuncture (EA) is able to reduce cell death and to improve functional recovery. One possible mechanism of this neuroprotective effect is that EA has regulatory effect on NMDARs. To test whether EA could protect the spinal cord after SCI by decreasing the expression levels of NR1 and NR2A. We conducted EA treatment on a rat SCI model produced with a New York University (NYU) Impactor and measured hindlimb locomotor function by Basso, Beattie and Bresnahan Locomotor Rating Scale (BBB Scale). The expression of NR1 and NR2, the subunits of NMDARs, in the injured spinal cord was measured by Immunofluorescence stainings, western blot and real-time quantitative PCR (RT-qPCR). Our results showed that two days after the SCI the expression of NR1 and NR2 were dramatically enhanced at both protein and mNRA levels, which were significantly reduced by EA treatment at two specific acupoints, Dazhui (DU14) and Mingmen (DU4). EA is a potential therapeutic method for treating early SCI in human. Copyright © 2017 Elsevier Inc. All rights reserved.

A 16-year-old girl with anti-NMDA-receptor encephalitis and family history of psychotic disorders.

PubMed

Cleland, Neil; Lieblich, Samuel; Schalling, Martin; Rahm, Christoffer

2015-12-01

Autoimmune NMDA-R encephalitis (ANRE) shares clinical features with schizophrenia. Recent research also indicates that both disorders are associated with dysfunction of the N-Methyl-D-Aspartate glutamate receptors (NMDA-R) subunit 1. We present the case of Ms A, 16 years old. Ms A presented with acute personality change, bizarre behaviour, delusional ideas and atypical seizures. She had a family history of psychotic disorders, and autistic traits diagnosed in childhood. She was initially diagnosed with a psychotic disorder. Delayed testing of CSF indicated ANRE. As the patient was a Jehovah's witness the treating team was unable to use gammaglobulin therapy; they instead relied on combined plasmapheresis and rituximab. To exclude the possibility that the affected members of this family shared a gene coding for an abnormal configuration of the NMDA receptor subunit 1 we sequenced the region of the GRIN1 gene in DNA extracted from blood in both Ms A and her grandmother. Ms A's condition improved dramatically, though her long-term memory is still demonstrably impaired. No genetic abnormality was detected. This case emphasizes how important it is, for a first episode psychosis, to exclude ANRE and other autoimmune synaptic encephalitides, even in the face of significant family history, and if seronegative, the importance of testing for CSF autoantibodies.

Boutons containing vesicular zinc define a subpopulation of synapses with low AMPAR content in rat hippocampus.

PubMed

Sindreu, Carlos Balet; Varoqui, Hélène; Erickson, Jeffrey D; Pérez-Clausell, Jeús

2003-08-01

Cortical regions of the brain stand out for their high content in synaptic zinc, which may thus be involved in synaptic function. The relative number, chemical nature and transmitter receptor profile of synapses that sequester vesicular zinc are largely unknown. To address this, we combined pre-embedding zinc histochemistry and post-embedding immunogold electron microscopy in rat hippocampus. All giant mossy fibre (MF) terminals in the CA3 region and approximately 45% of boutons making axospinous synapses in stratum radiatum in CA1 contained synaptic vesicles that stained for zinc. Both types of zinc-positive boutons selectively expressed the vesicular zinc transporter ZnT-3. Zinc-positive boutons further immunoreacted to the vesicular glutamate transporter VGLUT-1, but not to the transmitter gamma-aminobutyric acid. Most dendritic spines in CA1 immunoreacted to alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR) subunits GluR1-3 (approximately 80%) and to N-methyl-D-aspartate receptor (NMDAR) subunits NR1 + NR2A/B (approximately 90%). Synapses made by zinc-positive boutons contained 40% less AMPAR particles than those made by zinc-negative boutons, whereas NMDAR counts were similar. Further analysis indicated that this was due to the reduced synaptic expression of both GluR1 and GluR2 subunits. Hence, the levels of postsynaptic AMPARs may vary according to the presence of vesicular zinc in excitatory afferents to CA1. Zinc-positive and zinc-negative synapses may represent two glutamatergic subpopulations with distinct synaptic signalling.

Altered expression of alternatively spliced isoforms of the mRNA NMDAR1 receptor in the visual cortex of strabismic cats.

PubMed

Yin, Z Q; Deng, Z M; Crewther, S G; Crewther, D P

2001-11-20

Although much has been written about the role of the NMDA receptor's role in experience dependent visual plasticity, the function of the NMDAR1 receptor subunit in the post-plasticity stage of development is still not well understood. However, in the well studied model of strabismic amblyopia where binocularity is reduced, but where most primary visual cortex neurons can be driven by one or other eye, the density of expression of NMDAR1 receptor protein is significantly reduced, compared to normals. This study aims to identify which of eight isoforms of the spliced heterogeneous variants of the NMDAR1 mRNA receptor gene are associated with this decrease in expression as a means of elucidating possible function. A series of digoxygenin-labelled oligonucleotide probes based on the human gene sequence have been used for in situ hybridization (ISH) of sections from the striate cortex of four adult cats. The probes were used to uniquely detect the expression of alternatively spliced mRNA variants in 66,487 cells from sections from the area centralis projection of two normal cats and two cats made esotropic as kittens by tenotomy at two weeks of age. As expected, total NMDAR1 mRNA isoform expression was significantly lower in the striate cortex of strabismic compared to normal cats. The proportion of cortical cells expressing the R1-a, R1-b, and R1-1 isoforms in strabismic animals was decreased while the proportion expressing R1-3 was increased, especially in layers V and VI. No significant difference in expression of the R1-2 and R1-4 isoforms was seen comparing strabismic and normal cats. These results confirm our previous findings and suggest that transcriptional inhibition of specific isoforms of NMDAR1 mRNA may underlie the change in receptor expression. This preferential reduction in the proportion of neurons bearing particular NMDAR1 isoforms, i.e. isoforms R1-a and b, and R1-1 with partial compensation through the expression of the R1-3 isoform, is more likely related to lowered proportion of binocularly activated neurons in the strabismic cat than to changes in eye dominance or the presence of amblyopia in one eye.

Ring finger protein 10 is a novel synaptonuclear messenger encoding activation of NMDA receptors in hippocampus

PubMed Central

Dinamarca, Margarita C; Guzzetti, Francesca; Karpova, Anna; Lim, Dmitry; Mitro, Nico; Musardo, Stefano; Mellone, Manuela; Marcello, Elena; Stanic, Jennifer; Samaddar, Tanmoy; Burguière, Adeline; Caldarelli, Antonio; Genazzani, Armando A; Perroy, Julie; Fagni, Laurent; Canonico, Pier Luigi; Kreutz, Michael R; Gardoni, Fabrizio; Luca, Monica Di

2016-01-01

Synapses and nuclei are connected by bidirectional communication mechanisms that enable information transfer encoded by macromolecules. Here, we identified RNF10 as a novel synaptonuclear protein messenger. RNF10 is activated by calcium signals at the postsynaptic compartment and elicits discrete changes at the transcriptional level. RNF10 is enriched at the excitatory synapse where it associates with the GluN2A subunit of NMDA receptors (NMDARs). Activation of synaptic GluN2A-containing NMDARs and induction of long term potentiation (LTP) lead to the translocation of RNF10 from dendritic segments and dendritic spines to the nucleus. In particular, we provide evidence for importin-dependent long-distance transport from synapto-dendritic compartments to the nucleus. Notably, RNF10 silencing prevents the maintenance of LTP as well as LTP-dependent structural modifications of dendritic spines. DOI: http://dx.doi.org/10.7554/eLife.12430.001 PMID:26977767

The group II metabotropic glutamate receptor agonist LY354740 and the D2 receptor antagonist haloperidol reduce locomotor hyperactivity but fail to rescue spatial working memory in GluA1 knockout mice.

PubMed

Boerner, Thomas; Bygrave, Alexei M; Chen, Jingkai; Fernando, Anushka; Jackson, Stephanie; Barkus, Chris; Sprengel, Rolf; Seeburg, Peter H; Harrison, Paul J; Gilmour, Gary; Bannerman, David M; Sanderson, David J

2017-04-01

Group II metabotropic glutamate receptor agonists have been suggested as potential anti-psychotics, at least in part, based on the observation that the agonist LY354740 appeared to rescue the cognitive deficits caused by non-competitive N-methyl-d-aspartate receptor (NMDAR) antagonists, including spatial working memory deficits in rodents. Here, we tested the ability of LY354740 to rescue spatial working memory performance in mice that lack the GluA1 subunit of the AMPA glutamate receptor, encoded by Gria1, a gene recently implicated in schizophrenia by genome-wide association studies. We found that LY354740 failed to rescue the spatial working memory deficit in Gria1 -/- mice during rewarded alternation performance in the T-maze. In contrast, LY354740 did reduce the locomotor hyperactivity in these animals to a level that was similar to controls. A similar pattern was found with the dopamine receptor antagonist haloperidol, with no amelioration of the spatial working memory deficit in Gria1 -/- mice, even though the same dose of haloperidol reduced their locomotor hyperactivity. These results with LY354740 contrast with the rescue of spatial working memory in models of glutamatergic hypofunction using non-competitive NMDAR antagonists. Future studies should determine whether group II mGluR agonists can rescue spatial working memory deficits with other NMDAR manipulations, including genetic models and other pharmacological manipulations of NMDAR function. © 2017 The Authors. European Journal of Neuroscience published by Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Roles of the SH2 and SH3 domains in the regulation of neuronal Src kinase functions.

PubMed

Groveman, Bradley R; Xue, Sheng; Marin, Vedrana; Xu, Jindong; Ali, Mohammad K; Bienkiewicz, Ewa A; Yu, Xian-Min

2011-02-01

Previous studies demonstrated that intra-domain interactions between Src family kinases (SFKs), stabilized by binding of the phosphorylated C-terminus to the SH2 domain and/or binding of the SH2 kinase linker to the SH3 domain, lock the molecules in a closed conformation, disrupt the kinase active site, and inactivate SFKs. Here we report that the up-regulation of N-methyl-D-aspartate receptors (NMDARs) induced by expression of constitutively active neuronal Src (n-Src), in which the C-terminus tyrosine is mutated to phenylalanine (n-Src/Y535F), is significantly reduced by dysfunctions of the SH2 and/or SH3 domains of the protein. Furthermore, we found that dysfunctions of SH2 and/or SH3 domains reduce auto-phosphorylation of the kinase activation loop, depress kinase activity, and decrease NMDAR phosphorylation. The SH2 domain plays a greater regulatory role than the SH3 domain. Our data also show that n-Src binds directly to the C-terminus of the NMDAR NR2A subunit in vitro, with a K(D) of 108.2 ± 13.3 nM. This binding is not Src kinase activity-dependent, and dysfunctions of the SH2 and/or SH3 domains do not significantly affect the binding. These data indicate that the SH2 and SH3 domains may function to promote the catalytic activity of active n-Src, which is important in the regulation of NMDAR functions. © 2010 The Authors Journal compilation © 2010 FEBS.

Glutamate Receptors within the Mesolimbic Dopamine System Mediate Alcohol Relapse Behavior.

PubMed

Eisenhardt, Manuela; Leixner, Sarah; Luján, Rafael; Spanagel, Rainer; Bilbao, Ainhoa

2015-11-25

Glutamatergic input within the mesolimbic dopamine (DA) pathway plays a critical role in the development of addictive behavior. Although this is well established for some drugs of abuse, it is not known whether glutamate receptors within the mesolimbic system are involved in mediating the addictive properties of chronic alcohol use. Here we evaluated the contribution of mesolimbic NMDARs and AMPARs in mediating alcohol-seeking responses induced by environmental stimuli and relapse behavior using four inducible mutant mouse lines lacking the glutamate receptor genes Grin1 or Gria1 in either DA transporter (DAT) or D1R-expressing neurons. We first demonstrate the lack of GluN1 or GluA1 in either DAT- or D1R-expressing neurons in our mutant mouse lines by colocalization studies. We then show that GluN1 and GluA1 receptor subunits within these neuronal subpopulations mediate the alcohol deprivation effect, while having no impact on context- plus cue-induced reinstatement of alcohol-seeking behavior. We further validated these results pharmacologically by demonstrating similar reductions in the alcohol deprivation effect after infusion of the NMDAR antagonist memantine into the nucleus accumbens and ventral tegmental area of control mice, and a rescue of the mutant phenotype via pharmacological potentiation of AMPAR activity using aniracetam. In conclusion, dopamine neurons as well as D1R-expressing medium spiny neurons and their glutamatergic inputs via NMDARs and AMPARs act in concert to influence relapse responses. These results provide a neuroanatomical and molecular substrate for relapse behavior and emphasize the importance of glutamatergic drugs in modulating relapse behavior. Here we provide genetic and pharmacological evidence that glutamate receptors within the mesolimbic dopamine system play an essential role in alcohol relapse. Using various inducible and site-specific transgenic mouse models and pharmacological validation experiments, we show that critical subunits of NMDARs and AMPARs expressed either in dopamine neurons or in dopamine receptor D1-containing neurons play an important role in the alcohol deprivation effect (the increase in alcohol intake after a period of abstinence) while having no impact on context- plus cue-induced reinstatement of alcohol-seeking responses. Medications targeting glutamatergic neurotransmission by selective inactivation of these glutamate receptors might have therapeutic efficacy. Copyright © 2015 the authors 0270-6474/15/3515523-16$15.00/0.

The role of GluN2A and GluN2B NMDA receptor subunits in AgRP and POMC neurons on body weight and glucose homeostasis.

PubMed

Üner, Aykut; Gonçalves, Gabriel H M; Li, Wenjing; Porceban, Matheus; Caron, Nicole; Schönke, Milena; Delpire, Eric; Sakimura, Kenji; Bjørbæk, Christian

2015-10-01

Hypothalamic agouti-related peptide (AgRP) and pro-opiomelanocortin (POMC) expressing neurons play critical roles in control of energy balance. Glutamatergic input via n-methyl-d-aspartate receptors (NMDARs) is pivotal for regulation of neuronal activity and is required in AgRP neurons for normal body weight homeostasis. NMDARs typically consist of the obligatory GluN1 subunit and different GluN2 subunits, the latter exerting crucial differential effects on channel activity and neuronal function. Currently, the role of specific GluN2 subunits in AgRP and POMC neurons on whole body energy and glucose balance is unknown. We used the cre-lox system to genetically delete GluN2A or GluN2B only from AgRP or POMC neurons in mice. Mice were then subjected to metabolic analyses and assessment of AgRP and POMC neuronal function through morphological studies. We show that loss of GluN2B from AgRP neurons reduces body weight, fat mass, and food intake, whereas GluN2B in POMC neurons is not required for normal energy balance control. GluN2A subunits in either AgRP or POMC neurons are not required for regulation of body weight. Deletion of GluN2B reduces the number of AgRP neurons and decreases their dendritic length. In addition, loss of GluN2B in AgRP neurons of the morbidly obese and severely diabetic leptin-deficient Lep (ob/ob) mice does not affect body weight and food intake but, remarkably, leads to full correction of hyperglycemia. Lep (ob/ob) mice lacking GluN2B in AgRP neurons are also more sensitive to leptin's anti-obesity actions. GluN2B-containing NMDA receptors in AgRP neurons play a critical role in central control of body weight homeostasis and blood glucose balance via mechanisms that likely involve regulation of AgRP neuronal survival and structure, and modulation of hypothalamic leptin action.

d-Aspartate oxidase influences glutamatergic system homeostasis in mammalian brain.

PubMed

Cristino, Luigia; Luongo, Livio; Squillace, Marta; Paolone, Giovanna; Mango, Dalila; Piccinin, Sonia; Zianni, Elisa; Imperatore, Roberta; Iannotta, Monica; Longo, Francesco; Errico, Francesco; Vescovi, Angelo Luigi; Morari, Michele; Maione, Sabatino; Gardoni, Fabrizio; Nisticò, Robert; Usiello, Alessandro

2015-05-01

We have investigated the relevance of d-aspartate oxidase, the only enzyme known to selectively degrade d-aspartate (d-Asp), in modulating glutamatergic system homeostasis. Interestingly, the lack of the Ddo gene, by raising d-Asp content, induces a substantial increase in extracellular glutamate (Glu) levels in Ddo-mutant brains. Consistent with an exaggerated and persistent N-methyl-d-aspartate receptor (NMDAR) stimulation, we documented in Ddo knockouts severe age-dependent structural and functional alterations mirrored by expression of active caspases 3 and 7 along with appearance of dystrophic microglia and reactive astrocytes. In addition, prolonged elevation of d-Asp triggered in mutants alterations of NMDAR-dependent synaptic plasticity associated to reduction of hippocampal GluN1 and GluN2B subunits selectively located at synaptic sites and to increase in the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-to-N-methyl-d-aspartate ratio. These effects, all of which converged on a progressive hyporesponsiveness at NMDAR sites, functionally resulted in a greater vulnerability to phencyclidine-induced prepulse inhibition deficits in mutants. In conclusion, our results indicate that d-aspartate oxidase, by strictly regulating d-Asp levels, impacts on the homeostasis of glutamatergic system, thus preventing accelerated neurodegenerative processes. Copyright © 2015 Elsevier Inc. All rights reserved.

Allosteric regulation in NMDA receptors revealed by the genetically encoded photo-cross-linkers

PubMed Central

Tian, Meilin; Ye, Shixin

2016-01-01

Allostery is essential to neuronal receptor function, but its transient nature poses a challenge for characterization. The N-terminal domains (NTDs) distinct from ligand binding domains are a major locus for allosteric regulation of NMDA receptors (NMDARs), where different modulatory binding sites have been observed. The inhibitor ifenprodil, and related phenylethanoamine compounds specifically targeting GluN1/GluN2B NMDARs have neuroprotective activity. However, whether they use differential structural pathways than the endogenous inhibitor Zn2+ for regulation is unknown. We applied genetically encoded unnatural amino acids (Uaas) and monitored the functional changes in living cells with photo-cross-linkers specifically incorporated at the ifenprodil binding interface between GluN1 and GluN2B subunits. We report constraining the NTD domain movement, by a light induced crosslinking bond that introduces minimal perturbation to the ligand binding, specifically impedes the transduction of ifenprodil but not Zn2+ inhibition. Subtle distance changes reveal interfacial flexibility and NTD rearrangements in the presence of modulators. Our results present a much richer dynamic picture of allostery than conventional approaches targeting the same interface, and highlight key residues that determine functional and subtype specificity of NMDARs. The light-sensitive mutant neuronal receptors provide complementary tools to the photo-switchable ligands for opto-neuropharmacology. PMID:27713495

Schizophrenia-Like Dopamine Release Abnormalities in a Mouse Model of NMDA Receptor Hypofunction.

PubMed

Nakao, Kazuhito; Jeevakumar, Vivek; Jiang, Sunny Zhihong; Fujita, Yuko; Diaz, Noelia B; Pretell Annan, Carlos A; Eskow Jaunarajs, Karen L; Hashimoto, Kenji; Belforte, Juan E; Nakazawa, Kazu

2018-01-31

Amphetamine-induced augmentation of striatal dopamine and its blunted release in prefrontal cortex (PFC) is a hallmark of schizophrenia pathophysiology. Although N-methyl-D-aspartate receptor (NMDAR) hypofunction is also implicated in schizophrenia, it remains unclear whether NMDAR hypofunction leads to dopamine release abnormalities. We previously demonstrated schizophrenia-like phenotypes in GABAergic neuron-specific NMDAR hypofunctional mutant mice, in which Ppp1r2-Cre dependent deletion of indispensable NMDAR channel subunit Grin1 is induced in corticolimbic GABAergic neurons including parvalbumin (PV)-positive neurons, in postnatal development, but not in adulthood. Here, we report enhanced dopaminomimetic-induced locomotor activity in these mutants, along with bidirectional, site-specific changes in in vivo amphetamine-induced dopamine release: nucleus accumbens (NAc) dopamine release was enhanced by amphetamine in postnatal Ppp1r2-Cre/Grin1 knockout (KO) mice, whereas dopamine release was dramatically reduced in the medial PFC (mPFC) compared to controls. Basal tissue dopamine levels in both the NAc and mPFC were unaffected. Interestingly, the magnitude and distribution of amphetamine-induced c-Fos expression in dopamine neurons was comparable between genotypes across dopaminergic input subregions in the ventral tegmental area (VTA). These effects appear to be both developmentally and cell-type specifically modulated, since PV-specific Grin1 KO mice could induce the same effects as seen in postnatal-onset Ppp1r2-Cre/Grin1 KO mice, but no such abnormalities were observed in somatostatin-Cre/Grin1 KO mice or adult-onset Ppp1r2-Cre/Grin1 KO mice. These results suggest that PV GABAergic neuron-NMDAR hypofunction in postnatal development confers bidirectional NAc hyper- and mPFC hypo-sensitivity to amphetamine-induced dopamine release, similar to that classically observed in schizophrenia pathophysiology. © The Author(s) 2018. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center.

Functional reorganization of visual cortex maps after ischemic lesions is accompanied by changes in expression of cytoskeletal proteins and NMDA and GABA(A) receptor subunits.

PubMed

Zepeda, Angelica; Sengpiel, Frank; Guagnelli, Miguel Angel; Vaca, Luis; Arias, Clorinda

2004-02-25

Reorganization of cortical representations after focal visual cortex lesions has been documented. It has been suggested that functional reorganization may rely on cellular mechanisms involving modifications in the excitatory/inhibitory neurotransmission balance and on morphological changes of neurons peripheral to the lesion. We explored functional reorganization of cortical retinotopic maps after a focal ischemic lesion in primary visual cortex of kittens using optical imaging of intrinsic signals. After 1, 2, and 5 weeks postlesion (wPL), we addressed whether functional reorganization correlated in time with changes in the expression of MAP-2, GAP-43, GFAP, GABA(A) receptor subunit alpha1 (GABA(A)alpha1), subunit 1 of the NMDA receptor (NMDAR1), and in neurotransmitter levels at the border of the lesion. Our results show that: (1) retinotopic maps reorganize with time after an ischemic lesion; (2) MAP-2 levels increase gradually from 1wPL to 5wPL; (3) MAP-2 upregulation is associated with an increase in dendritic-like structures surrounding the lesion and a decrease in GFAP-positive cells; (4) GAP-43 levels reach the highest point at 2wPL; (5) NMDAR1 and glutamate contents increase in parallel from 1wPL to 5wPL; (6) GABA(A)alpha1 levels increase from 1wPL to 2wPL but do not change after this time point; and (7) GABA contents remain low from 1wPL to 5wPL. This is a comprehensive study showing for the first time that functional reorganization correlates in time with dendritic sprouting and with changes in the excitatory/inhibitory neurotransmission systems previously proposed to participate in cortical remodeling and suggests mechanisms by which plasticity of cortical representations may occur.

Altered emotionality, hippocampus-dependent performance and expression of NMDA receptor subunit mRNAs in chronically stressed mice.

PubMed

Costa-Nunes, João; Zubareva, Olga; Araújo-Correia, Margarida; Valença, Andreia; Schroeter, Careen A; Pawluski, Jodi L; Vignisse, Julie; Steinbusch, Hellen; Hermes, Denise; Phillipines, Marjan; Steinbusch, Harry M W; Strekalova, Tatyana

2014-01-01

N-Methyl-D-aspartate receptor (NMDAR)-mediated neurotransmission in the hippocampus is implicated in cognitive and emotional disturbances during stress-related disorders. Here, using quantitative RT-PCR, we investigated the hippocampal expression of NR2A, NR2B and NR1 subunit mRNAs in a mouse stress paradigm that mimics clinically relevant conditions of simultaneously affected emotionality and hippocampus-dependent functions. A 2-week stress procedure, which comprised ethologically valid stressors, exposure to a rat and social defeat, was applied to male C57BL/6J mice. For predation stress, mice were introduced into transparent containers that were placed in a rat home cage during the night; social defeat was applied during the daytime using aggressive CD1 mice. This treatment impaired hippocampus-dependent performance during contextual fear conditioning. A correlation between this behavior and food displacement performance was demonstrated, suggesting that burrowing behavior is affected by the stress procedure and is hippocampus-dependent. Stressed mice (n = 22) showed behavioral invigoration and anomalous anxiolytic-like profiles in the O-maze and brightly illuminated open field, unaltered short-term memory in the step-down avoidance task and enhanced aggressive traits, as compared to non-stressed mice (n = 10). Stressed mice showed increased basal serum corticosterone concentrations, hippocampal mRNA expression for the NR2A subunit of the NMDAR and in the NR2A/NR2B ratio; mRNA expression of NR2B and NR1 was unchanged. Thus, stress-induced aberrations in both hippocampal-dependent performance and emotional abnormalities are associated with alterations in hippocampal mRNA NR2A levels and the NR2A/NR2B ratio and not with mRNA expression of NR2B or NR1.

Input- and subunit-specific AMPA receptor trafficking underlying long-term potentiation at hippocampal CA3 synapses.

PubMed

Kakegawa, Wataru; Tsuzuki, Keisuke; Yoshida, Yukari; Kameyama, Kimihiko; Ozawa, Seiji

2004-07-01

Hippocampal CA3 pyramidal neurons receive synaptic inputs from both mossy fibres (MFs) and associational fibres (AFs). Long-term potentiation (LTP) at these synapses differs in its induction sites and N-methyl-D-aspartate receptor (NMDAR) dependence. Most evidence favours the presynaptic and postsynaptic mechanisms for induction of MF LTP and AF LTP, respectively. This implies that molecular and functional properties differ between MF and AF synapses at both presynaptic and postsynaptic sites. In this study, we focused on the difference in the postsynaptic trafficking of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) between these synapses. To trace the subunit-specific trafficking of AMPARs at each synapse, GluR1 and GluR2 subunits were introduced into CA3 pyramidal neurons in hippocampal organotypic cultures using the Sindbis viral expression system. The electrophysiologically-tagged GluR2 AMPARs, produced by the viral-mediated transfer of the unedited form of GluR2 (GluR2Q), were inserted into both MF and AF postsynaptic sites in a neuronal activity-independent manner. Endogenous Ca(2+)-impermeable AMPARs at these synapses were replaced with exogenous Ca(2+)-permeable receptors, and Ca(2+) influx via the newly expressed postsynaptic AMPARs induced NMDAR-independent LTP at AF synapses. In contrast, no GluR1 AMPAR produced by the gene transfer was constitutively incorporated into AF postsynaptic sites, and only a small amount into MF postsynaptic sites. The synaptic trafficking of GluR1 AMPARs was triggered by the activity of Ca(2+)/calmodulin-dependent kinase II or high-frequency stimulation to induce LTP at AF synapses, but not at MF synapses. These results indicate that MF and AF postsynaptic sites possess distinct properties for AMPAR trafficking in CA3 pyramidal neurons.

The relationship between NMDA receptors and microwave-induced learning and memory impairment: a long-term observation on Wistar rats.

PubMed

Wang, Hui; Peng, Ruiyun; Zhao, Li; Wang, Shuiming; Gao, Yabing; Wang, Lifeng; Zuo, Hongyan; Dong, Ji; Xu, Xinping; Zhou, Hongmei; Su, Zhentao

2015-03-01

Abstract Purpose: To investigate whether high power microwave could cause continuous disorders to learning and memory in Wistar rats and to explore the underlying mechanisms. Eighty Wistar rats were exposed to a 2.856 GHz pulsed microwave source at a power density of 0 mW/cm(2) and 50 mW/cm(2) microwave for 6 min. The spatial memory ability, the structure of the hippocampus, contents of amino acids neurotransmitters in hippocampus and the expression of N-methyl-D-aspartic acid receptors (NMDAR) subunit 1, 2A and 2B (NR1, NR2A and NR2B) were detected at 1, 3, 6, 9, 12 and 18 months after microwave exposure. Our results showed that the microwave-exposed rats showed consistent deficiencies in spatial learning and memory. The level of amino acid neurotransmitters also decreased after microwave radiation. The ratio of glutamate (Glu) and gammaaminobutyric acid (GABA) significantly decreased at 6 months. Besides, the hippocampus showed varying degrees of degeneration of neurons, increased postsynaptic density and blurred synaptic clefts in the exposure group. The NR1 and NR2B expression showed a significant decrease, especially the NR2B expression. This study indicated that the content of amino acids neurotransmitters, the expression of NMDAR subunits and the variation of hippocampal structure might contribute to the long-term cognitive impairment after microwave exposure.

Contribution of NMDA receptor hypofunction in prefrontal and cortical excitatory neurons to schizophrenia-like phenotypes.

PubMed

Rompala, Gregory R; Zsiros, Veronika; Zhang, Shuqin; Kolata, Stefan M; Nakazawa, Kazu

2013-01-01

Pharmacological and genetic studies support a role for NMDA receptor (NMDAR) hypofunction in the etiology of schizophrenia. We have previously demonstrated that NMDAR obligatory subunit 1 (GluN1) deletion in corticolimbic interneurons during early postnatal development is sufficient to confer schizophrenia-like phenotypes in mice. However, the consequence of NMDAR hypofunction in cortical excitatory neurons is not well delineated. Here, we characterize a conditional knockout mouse strain (CtxGluN1 KO mice), in which postnatal GluN1 deletion is largely confined to the excitatory neurons in layer II/III of the medial prefrontal cortex and sensory cortices, as evidenced by the lack of GluN1 mRNA expression in in situ hybridization immunocytochemistry as well as the lack of NMDA currents with in vitro recordings. Mutants were impaired in prepulse inhibition of the auditory startle reflex as well as object-based short-term memory. However, they did not exhibit impairments in additional hallmarks of schizophrenia-like phenotypes (e.g. spatial working memory, social behavior, saccharine preference, novelty and amphetamine-induced hyperlocomotion, and anxiety-related behavior). Furthermore, upon administration of the NMDA receptor antagonist, MK-801, there were no differences in locomotor activity versus controls. The mutant mice also showed negligible levels of reactive oxygen species production following chronic social isolation, and recording of miniature-EPSC/IPSCs from layer II/III excitatory neurons in medial prefrontal cortex suggested no alteration in GABAergic activity. All together, the mutant mice displayed cognitive deficits in the absence of additional behavioral or cellular phenotypes reflecting schizophrenia pathophysiology. Thus, NMDAR hypofunction in prefrontal and cortical excitatory neurons may recapitulate only a cognitive aspect of human schizophrenia symptoms.

Input-Specific NMDAR-Dependent Potentiation of Dendritic GABAergic Inhibition.

PubMed

Chiu, Chiayu Q; Martenson, James S; Yamazaki, Maya; Natsume, Rie; Sakimura, Kenji; Tomita, Susumu; Tavalin, Steven J; Higley, Michael J

2018-01-17

Preservation of a balance between synaptic excitation and inhibition is critical for normal brain function. A number of homeostatic cellular mechanisms have been suggested to play a role in maintaining this balance, including long-term plasticity of GABAergic inhibitory synapses. Many previous studies have demonstrated a coupling of postsynaptic spiking with modification of perisomatic inhibition. Here, we demonstrate that activation of NMDA-type glutamate receptors leads to input-specific long-term potentiation of dendritic inhibition mediated by somatostatin-expressing interneurons. This form of plasticity is expressed postsynaptically and requires both CaMKIIα and the β2 subunit of the GABA-A receptor. Importantly, this process may function to preserve dendritic inhibition, as genetic deletion of NMDAR signaling results in a selective weakening of dendritic inhibition. Overall, our results reveal a new mechanism for linking excitatory and inhibitory input in neuronal dendrites and provide novel insight into the homeostatic regulation of synaptic transmission in cortical circuits. Copyright © 2017 Elsevier Inc. All rights reserved.

A Role for Prefrontal Cortical NMDA Receptors in Murine Alcohol-Heightened Aggression.

PubMed

Newman, Emily L; Terunuma, Miho; Wang, Tiffany L; Hewage, Nishani; Bicakci, Matthew B; Moss, Stephen J; DeBold, Joseph F; Miczek, Klaus A

2018-05-01

Alcohol is associated with nearly half of all violent crimes committed in the United States; yet, a potential neural basis for this type of pathological aggression remains elusive. Alcohol may act on N-methyl-d-aspartate receptors (NMDARs) within cortical circuits to impede processing and to promote aggression. Here, male mice were characterized as alcohol-heightened (AHAs) or alcohol non-heightened aggressors (ANAs) during resident-intruder confrontations after self-administering 1.0 g/kg alcohol (6% w/v) or water. Alcohol produced a pathological-like pattern of aggression in AHAs; these mice shifted their bites to more vulnerable locations on the body of a submissive animal, including the anterior back and ventrum after consuming alcohol. In addition, through immunoblotting, we found that AHAs overexpressed the NMDAR GluN2D subunit in the prefrontal cortex (PFC) as compared to ANAs while the two phenotypes expressed similar levels of GluN1, GluN2A and GluN2B. After identifying several behavioral and molecular characteristics that distinguish AHAs from ANAs, we tested additional mice for their aggression following preferential antagonism of GluN2D-containing NMDARs. In these experiments, groups of AHAs and ANAs self-administered 1.0 g/kg alcohol (6% w/v) or water before receiving intraperitoneal (i.p.) doses of ketamine or memantine, or infusions of memantine directly into the prelimbic (PLmPFC) or infralimbic medial PFC (ILmPFC). Moderate doses of IP ketamine, IP memantine, or intra-PLmPFC memantine increased aggression in AHAs, but only in the absence of alcohol. Prior alcohol intake blocked the pro-aggressive effects of ketamine or memantine. In contrast, only memantine, administered systemically or intra-PLmPFC, interacted with prior alcohol intake to escalate aggression in ANAs. Intra-ILmPFC memantine had no effect on aggression in either AHAs or ANAs. In sum, this work illustrates a potential role of GluN2D-containing NMDARs in the PLmPFC in alcohol-heightened aggression. GluN2D-containing NMDARs are highly expressed on cortical parvalbumin-containing interneurons, suggesting that, in a subset of individuals, alcohol may functionally alter signal integration within cortical microcircuits to dysregulate threat reactivity and promote aggression. This work suggests that targeting GluN2D-NMDARs may be of use in reducing the impact of alcohol-related violence in the human population.

NMDA channel gating is influenced by a tryptophan residue in the M2 domain but calcium permeation is not altered.

PubMed Central

Buck, D P; Howitt, S M; Clements, J D

2000-01-01

N-Methyl-D-aspartate (NMDA) receptors are susceptible to open-channel block by dizolcipine (MK-801), ketamine and Mg(2+) and are permeable to Ca(2+). It is thought that a tryptophan residue in the second membrane-associated domain (M2) may form part of the binding site for open-channel blockers and contribute to Ca(2+) permeability. We tested this hypothesis using recombinant wild-type and mutant NMDA receptors expressed in HEK-293 cells. The tryptophan was mutated to a leucine (W-5L) in both the NMDAR1 and NMDAR2A subunits. MK-801 and ketamine progressively inhibited currents evoked by glutamate, and the rate of inhibition was increased by the W-5L mutation. An increase in open channel probability accounted for the acceleration. Fluctuation analysis of the glutamate-evoked current revealed that the NMDAR1 W-5L mutation increased channel mean open time, providing further evidence for an alteration in gating. However, the equilibrium affinities of Mg(2+) and ketamine were largely unaffected by the W-5L mutation, and Ca(2+) permeability was not decreased. Therefore, the M2 tryptophan residue of the NMDA channel is not involved in Ca(2+) permeation or the binding of open-channel blockers, but plays an important role in channel gating. PMID:11053122

Absence of NMDA receptor antibodies in the rare association between Type 1 Narcolepsy and Psychosis

PubMed Central

Dauvilliers, Y.; Gaig, C.; Barateau, L.; Graus, F.; Iranzo, A.; Lopez, R.; Santamaria, J.

2016-01-01

Frequency and mechanisms underlying the association between narcolepsy type 1 (NT1) and psychosis remain unclear with potential role for a common immune pathway. We estimated the frequency of psychosis and its characteristics in NT1 at two European sleep centers (France, n = 381; Spain, n = 161) and measured IgG autoantibodies that recognize the GluN1 subunit of the NMDAR in 9 patients with NT1 with psychosis, and 25 NT1 patients without psychosis. Ten NT1 patients (6 in France, 4 in Spain) were diagnosed with comorbid psychosis, a frequency of 1.8%. One patient reported psychotic symptoms few months before narcolepsy onset, two patients few months after onset, and one patient one year after onset but after modafinil introduction. The six remaining patients reported long delays between NT1 and psychosis onset. Half the patients, mostly male adults, reported onset or worsening of psychotic symptoms after medication. We found no IgG antibodies to NR1/NR2B heteromers of the NMDARs in patients with NT1 with or without psychosis. To conclude, psychosis is rare in NT1, with limited evidence for a key impact of stimulants, and no association with anti-NMDAR antibodies. However, dramatic NT1 and schizophrenia exists especially in early onset NT1, which may lead to inappropriate diagnosis and management. PMID:27143278

Regulation of dopamine D1 receptor dynamics within the postsynaptic density of hippocampal glutamate synapses.

PubMed

Ladepeche, Laurent; Yang, Luting; Bouchet, Delphine; Groc, Laurent

2013-01-01

Dopamine receptor potently modulates glutamate signalling, synaptic plasticity and neuronal network adaptations in various pathophysiological processes. Although key intracellular signalling cascades have been identified, the cellular mechanism by which dopamine and glutamate receptor-mediated signalling interplay at glutamate synapse remain poorly understood. Among the cellular mechanisms proposed to aggregate D1R in glutamate synapses, the direct interaction between D1R and the scaffold protein PSD95 or the direct interaction with the glutamate NMDA receptor (NMDAR) have been proposed. To tackle this question we here used high-resolution single nanoparticle imaging since it provides a powerful way to investigate at the sub-micron resolution the dynamic interaction between these partners in live synapses. We demonstrate in hippocampal neuronal networks that dopamine D1 receptors (D1R) laterally diffuse within glutamate synapses, in which their diffusion is reduced. Disrupting the interaction between D1R and PSD95, through genetical manipulation and competing peptide, did not affect D1R dynamics in glutamatergic synapses. However, preventing the physical interaction between D1R and the GluN1 subunit of NMDAR abolished the synaptic stabilization of diffusing D1R. Together, these data provide direct evidence that the interaction between D1R and NMDAR in synapses participate in the building of the dopamine-receptor-mediated signalling, and most likely to the glutamate-dopamine cross-talk.

NADPH Oxidase Isoform 2 (NOX2) Is Involved in Drug Addiction Vulnerability in Progeny Developmentally Exposed to Ethanol.

PubMed

Contreras, Marcela L; de la Fuente-Ortega, Erwin; Vargas-Roberts, Sofía; Muñoz, Daniela C; Goic, Carolina A; Haeger, Paola A

2017-01-01

Ethanol exposure increases oxidative stress in developing organs, including the brain. Antioxidant treatment during maternal ethanol ingestion improves behavioral deficits in rodent models of fetal alcohol spectrum disorder (FASD). However, the impact of general antioxidant treatment in their adult offspring and the Specific Reactive Species (ROS)-dependent mechanism, are not fully understood. We hypothesized that pre and early postnatal ethanol exposure (PEE) modifies redox homeostasis, in particular NOX2 function during reward signaling in the mesocorticolimbic pathway, which reinforces the effects of alcohol. We developed a FASD rat model which was evaluated during adolescence (P21) and adulthood (P70). We first studied whether redox homeostasis is affected in PEE animals, by analyzing mRNA expression of SOD1, CAT, and Gpx1. We found that PEE reduced the mRNA levels of these three anti-oxidant enzymes in PFC and HIPP at P21 and in the VTA at P70. We also analyzed basal mRNA and protein expression of NOX2 subunits such as gp91phox, p22 phox, and p47 phox, in mesocorticolimbic brain areas of PEE rat brains. At P21, gp91 phox, and p47 phox levels in the VTA were decreased. At P70, gp91 phox mRNA levels was decreased in HIPP and both mRNA and protein levels were decreased in PFC. Since NOX2 is regulated by the N-methyl-D-aspartate Receptor (NMDAR), we analyzed NMDAR mRNA expression and found differential expression of NMDAR subunits (NR1 and NR2B) in the PFC that was age dependent, with levels decreased at P21 and increased at P70. The analysis also revealed decreased NR2B mRNA expression in HIPP and VTA at P70. Offspring from maternal ethanol users consumed 25% more ethanol in a free choice alcohol consumption test than control rats, and showed place preference for an alcohol-paired compartment. In vivo inhibition of NOX2 using apocynin in drinking water, or infusion of blocked peptide gp91 phox ds in the VTA normalized alcohol place preference, suggesting that NOX2 plays an important role in addictive like behavior. Taken together, PEE significantly affects the expression of antioxidant enzymes, NOX2, NMDAR in an age, and brain region dependent manner. Moreover, we demonstrate that NOX2 regulates alcohol seeking behavior.

Agmatine Prevents Adaptation of the Hippocampal Glutamate System in Chronic Morphine-Treated Rats.

PubMed

Wang, Xiao-Fei; Zhao, Tai-Yun; Su, Rui-Bin; Wu, Ning; Li, Jin

2016-12-01

Chronic exposure to opioids induces adaptation of glutamate neurotransmission, which plays a crucial role in addiction. Our previous studies revealed that agmatine attenuates opioid addiction and prevents the adaptation of glutamate neurotransmission in the nucleus accumbens of chronic morphine-treated rats. The hippocampus is important for drug addiction; however, whether adaptation of glutamate neurotransmission is modulated by agmatine in the hippocampus remains unknown. Here, we found that continuous pretreatment of rats with ascending doses of morphine for 5 days resulted in an increase in the hippocampal extracellular glutamate level induced by naloxone (2 mg/kg, i.p.) precipitation. Agmatine (20 mg/kg, s.c.) administered concurrently with morphine for 5 days attenuated the elevation of extracellular glutamate levels induced by naloxone precipitation. Furthermore, in the hippocampal synaptosome model, agmatine decreased the release and increased the uptake of glutamate in synaptosomes from chronic morphine-treated rats, which might contribute to the reduced elevation of glutamate levels induced by agmatine. We also found that expression of the hippocampal NR2B subunit, rather than the NR1 subunit, of N-methyl-D-aspartate receptors (NMDARs) was down-regulated after chronic morphine treatment, and agmatine inhibited this reduction. Taken together, agmatine prevented the adaptation of the hippocampal glutamate system caused by chronic exposure to morphine, including modulating extracellular glutamate concentration and NMDAR expression, which might be one of the mechanisms underlying the attenuation of opioid addiction by agmatine.

Hydrogen-rich saline controls remifentanil-induced hypernociception and NMDA receptor NR1 subunit membrane trafficking through GSK-3β in the DRG in rats.

PubMed

Zhang, Linlin; Shu, Ruichen; Wang, Chunyan; Wang, Haiyun; Li, Nan; Wang, Guolin

2014-07-01

Although NMDAR trafficking mediated by GSK-3β involvement in transmission of pronociceptive messages in the spinal cord has been confirmed by our previous studies, whether NMDAR trafficking is implicated in peripheral sensitization remains equivocal. It is demonstrated that inflammation is associated with spinal NMDAR-containing nociceptive neurons activation and the maintenance of opioid induced pain hypersensitivity. However, whether and how hydrogen-rich saline, as an effective anti-inflammatory drug, could prevent hyperalgesia through affecting peripheral sensitization caused by NMDAR activation remains to be explored. To test these effects, hydrogen-rich saline (2.5, 5 or 10 ml/kg) was administrated intraperitoneally after remifentanil infusion, NMDAR antagonist MK-801 or GSK-3β inhibitor TDZD-8 was administrated intravenously before remifentanil infusion in rats. We examined time course of hydrogen concentration in blood after hydrogen-rich saline administration. Mechanical and thermal hyperalgesia were evaluated by measuring PWT and PWL for 48 post-infusion hours, respectively. Western blotting and real-time qPCR assay were applied to analyze the NR1 membrane trafficking, GSK-3β expression and activity in DRG. Inflammatory mediators (TNF-α, IL-1β, and IL-6) expressions in DRG were also analyzed. We found that NR1 membrane trafficking in DRG increased, possibly due to GSK-3β activation after remifentanil infusion. We also discovered that hydrogen-rich saline not 2.5 ml/kg but 5 and 10 ml/kg could dose-dependently attenuate mechanical and thermal hyperalgesia without affecting baseline nociceptive threshold, reduce expressions of inflammatory mediators (TNF-α, IL-1β, and IL-6) and decrease NR1 trafficking mediated by GSK-3β, and minimal effective concentration was observed to be higher than 10 μmol/L, namely peak concentration in arterial blood after administration of HRS 2.5 ml/kg without any influence on hyperalgesia. Our results indicated that antihyperalgesic effect of hydrogen-rich saline might depend predominantly on its ability to reverse NR1 trafficking via inhibition of GSK-3β activity in DRG in a dose-dependent manner. Copyright © 2014 Elsevier Inc. All rights reserved.

A Molecular Determinant of Subtype-Specific Desensitization in Ionotropic Glutamate Receptors.

PubMed

Alsaloum, Matthew; Kazi, Rashek; Gan, Quan; Amin, Johansen; Wollmuth, Lonnie P

2016-03-02

AMPA and NMDA receptors are glutamate-gated ion channels that mediate fast excitatory synaptic transmission throughout the nervous system. In the continual presence of glutamate, AMPA and NMDA receptors containing the GluN2A or GluN2B subunit enter into a nonconducting, desensitized state that can impact synaptic responses and glutamate-mediated excitotoxicity. The process of desensitization is dramatically different between subtypes, but the basis for these differences is unknown. We generated an extensive sequence alignment of ionotropic glutamate receptors (iGluRs) from diverse animal phyla and identified a highly conserved motif, which we termed the "hydrophobic box," located at the extracellular interface of transmembrane helices. A single position in the hydrophobic box differed between mammalian AMPA and NMDA receptors. Surprisingly, we find that an NMDAR-to-AMPAR exchange mutation at this position in the rat GluN2A or GluN2B subunit had a dramatic and highly specific effect on NMDAR desensitization, making it AMPAR-like. In contrast, a reverse exchange mutation in AMPARs had minimal effects on desensitization. These experiments highlight differences in desensitization between iGluR subtypes and the highly specific contribution of the GluN2 subunit to this process. Rapid communication between cells in the nervous system depends on ion channels that are directly activated by neurotransmitter molecules. Here, we studied ionotropic glutamate receptors (iGluRs), which are ion channels activated by the neurotransmitter glutamate. By comparing the sequences of a vast number of iGluR proteins from diverse animal species, assisted by available structural information, we identified a highly conserved motif. We showed that a single amino acid difference in this motif between mammalian iGluR subtypes has dramatic effects on receptor function. These results have implications in both the evolution of synaptic function, as well as the role of iGluRs in health and disease. Copyright © 2016 the authors 0270-6474/16/362617-06$15.00/0.

The Pharmacological Inhibition of Fatty Acid Amide Hydrolase Prevents Excitotoxic Damage in the Rat Striatum: Possible Involvement of CB1 Receptors Regulation.

PubMed

Aguilera-Portillo, Gabriela; Rangel-López, Edgar; Villeda-Hernández, Juana; Chavarría, Anahí; Castellanos, Pilar; Elmazoglu, Zubeyir; Karasu, Çimen; Túnez, Isaac; Pedraza, Gibrán; Königsberg, Mina; Santamaría, Abel

2018-05-25

The endocannabinoid system (ECS) actively participates in several physiological processes within the central nervous system. Among such, its involvement in the downregulation of the N-methyl-D-aspartate receptor (NMDAr) through a modulatory input at the cannabinoid receptors (CBr) has been established. After its production via the kynurenine pathway (KP), quinolinic acid (QUIN) can act as an excitotoxin through the selective overactivation of NMDAr, thus participating in the onset and development of neurological disorders. In this work, we evaluated whether the pharmacological inhibition of fatty acid amide hydrolase (FAAH) by URB597, and the consequent increase in the endogenous levels of anandamide, can prevent the excitotoxic damage induced by QUIN. URB597 (0.3 mg/kg/day × 7 days, administered before, during and after the striatal lesion) exerted protective effects on the QUIN-induced motor (asymmetric behavior) and biochemical (lipid peroxidation and protein carbonylation) alterations in rats. URB597 also preserved the structural integrity of the striatum and prevented the neuronal loss (assessed as microtubule-associated protein-2 and glutamate decarboxylase localization) induced by QUIN (1 μL intrastriatal, 240 nmol/μL), while modified the early localization patterns of CBr1 (CB1) and NMDAr subunit 1 (NR1). Altogether, these findings support the concept that the pharmacological manipulation of the endocannabinoid system plays a neuroprotective role against excitotoxic insults in the central nervous system.

Simvastatin pretreatment protects cerebrum from neuronal injury by decreasing the expressions of phosphor-CaMK II and AQP4 in ischemic stroke rats.

PubMed

Zhu, Min-xia; Lu, Chao; Xia, Chun-mei; Qiao, Zhong-wei; Zhu, Da-nian

2014-12-01

Excitotoxicity and cytotoxic edema are the two major factors resulting in neuronal injury during brain ischemia and reperfusion. Ca2+/calmodulin-dependent protein kinase II (CaMK II), the downstream signal molecular of N-methyl-D-aspartate receptors (NMDARs), is a mediator in the excitotoxicity. Aquaporin 4 (AQP4), expressed mainly in the brain, is an important aquaporin to control the flux of water. In a previous study, we had reported that pretreatment of simvastatin protected the cerebrum from ischemia and reperfusion injury by decreasing neurological deficit score and infarct area (Zhu et al. PLoS One 7:e51552, 2012). The present study used a middle cerebral artery occlusion (MCAO) model to further explore the pleiotropic effect of simvastatin via CaMK II and AQP4. The results showed that simvastatin reduced degenerated cells and brain edema while decreasing the protein expressions of phosphor-CaMK II and AQP4, and increasing the ratios of Bcl-2/Bax, which was independent of cholesterol-lowering effect. Immunocomplexes formed between the subunit of NMDARs-NR3A and AQP4 were detected for the first time. It was concluded that simvastatin could protect the cerebrum from neuronal excitotoxicity and cytotoxic edema by downregulating the expressions of phosphor-CaMK II and AQP4, and that the interaction between NR3A and AQP4 might provide the base for AQP4 involving in the signaling pathways mediated by NMDARs.

Enhanced Polyubiquitination of Shank3 and NMDA receptor in a mouse model of Autism

PubMed Central

Bangash, M Ali; Park, Joo Min; Melnikova, Tatiana; Wang, Dehua; Jeon, Soo Kyeong; Lee, Deidre; Syeda, Sbaa; Kim, Juno; Kouser, Mehreen; Schwartz, Joshua; Cui, Yiyuan; Zhao, Xia; Speed, Haley E.; Kee, Sara E.; Tu, Jian Cheng; Hu, Jia-Hua; Petralia, Ronald S.; Linden, David J.; Powell, Craig M.; Savonenko, Alena; Xiao, Bo; Worley, Paul F.

2011-01-01

Summary We have created a mouse genetic model that mimics a human mutation of Shank3 that deletes the C-terminus and is associated with autism. Expressed as a single copy [Shank3(+/ΔC) mice], Shank3ΔC protein interacts with the WT gene product and results in >90 % reduction of Shank3 at synapses. This “gain of function” phenotype is linked to increased polyubiquitination of WT Shank3 and its redistribution into proteasomes. Similarly, the NR1 subunit of the NMDA receptor is reduced at synapses with increased polyubiquitination. Assays of post-synaptic density proteins, spine morphology and synapse number are unchanged in Shank3(+/ΔC) mice, but the amplitude of NMDAR responses is reduced together with reduced NMDAR-dependent LTP and LTD. Reciprocally, mGluR-dependent LTD is markedly enhanced. Shank3(+/ΔC) mice show behavioral deficits suggestive of autism and reduced NMDA receptor function. These studies reveal a mechanism distinct from haploinsufficiency by which mutations of Shank3 can evoke an autism-like disorder. PMID:21565394

Enhanced polyubiquitination of Shank3 and NMDA receptor in a mouse model of autism.

PubMed

Bangash, M Ali; Park, Joo Min; Melnikova, Tatiana; Wang, Dehua; Jeon, Soo Kyeong; Lee, Deidre; Syeda, Sbaa; Kim, Juno; Kouser, Mehreen; Schwartz, Joshua; Cui, Yiyuan; Zhao, Xia; Speed, Haley E; Kee, Sara E; Tu, Jian Cheng; Hu, Jia-Hua; Petralia, Ronald S; Linden, David J; Powell, Craig M; Savonenko, Alena; Xiao, Bo; Worley, Paul F

2011-05-27

We have created a mouse genetic model that mimics a human mutation of Shank3 that deletes the C terminus and is associated with autism. Expressed as a single copy [Shank3(+/ΔC) mice], Shank3ΔC protein interacts with the wild-type (WT) gene product and results in >90% reduction of Shank3 at synapses. This "gain-of-function" phenotype is linked to increased polyubiquitination of WT Shank3 and its redistribution into proteasomes. Similarly, the NR1 subunit of the NMDA receptor is reduced at synapses with increased polyubiquitination. Assays of postsynaptic density proteins, spine morphology, and synapse number are unchanged in Shank3(+/ΔC) mice, but the amplitude of NMDAR responses is reduced together with reduced NMDAR-dependent LTP and LTD. Reciprocally, mGluR-dependent LTD is markedly enhanced. Shank3(+/ΔC) mice show behavioral deficits suggestive of autism and reduced NMDA receptor function. These studies reveal a mechanism distinct from haploinsufficiency by which mutations of Shank3 can evoke an autism-like disorder. Copyright © 2011 Elsevier Inc. All rights reserved.

Sustained neuronal activity generated by glial plasticity

PubMed Central

Pirttimaki, Tiina M.; Hall, Stephen D.; Parri, H. Rheinallt

2011-01-01

Astrocytes release gliotransmitters, notably glutamate, that can affect neuronal and synaptic activity. In particular, astrocytic glutamate release results in the generation of N-methyl D-aspartate receptor (NMDA-R) mediated slow inward currents (SICs) in neurons. However, factors underlying the emergence of SICs, and their physiological roles are largely unknown. Here we show that, in acute slices of rat somatosensory thalamus, stimulation of Lemniscal or cortical afferents results in a sustained increase of SICs in thalamocortical (TC) neurons that outlasts the duration of the stimulus by an hour. This long term enhancement (LTE) of astrocytic glutamate release is induced by group I metabotropic glutamate receptors (mGluRs), and is dependent on astrocytic intracellular calcium ([Ca2+]i). Neuronal SICs are mediated by extrasynaptic NR2B subunit-containing NMDA-Rs and are capable of eliciting bursts. These are distinct from T-type Ca2+ channel dependent bursts of action potentials, and are synchronized in neighboring TC neurons. These findings describe a previously unrecognized form of excitatory, non-synaptic plasticity in the central nervous system (CNS) that feeds forward to generate local neuronal firing long after stimulus termination. PMID:21613477

Neurological effects of inorganic arsenic exposure: altered cysteine/glutamate transport, NMDA expression and spatial memory impairment.

PubMed

Ramos-Chávez, Lucio A; Rendón-López, Christian R R; Zepeda, Angélica; Silva-Adaya, Daniela; Del Razo, Luz M; Gonsebatt, María E

2015-01-01

Inorganic arsenic (iAs) is an important natural pollutant. Millions of individuals worldwide drink water with high levels of iAs. Chronic exposure to iAs has been associated with lower IQ and learning disabilities as well as memory impairment. iAs is methylated in tissues such as the brain generating mono and dimethylated species. iAs methylation requires cellular glutathione (GSH), which is the main antioxidant in the central nervous system (CNS). In humans, As species cross the placenta and are found in cord blood. A CD1 mouse model was used to investigate effects of gestational iAs exposure which can lead to oxidative damage, disrupted cysteine/glutamate transport and its putative impact in learning and memory. On postnatal days (PNDs) 1, 15 and 90, the expression of membrane transporters related to GSH synthesis and glutamate transport and toxicity, such as xCT, EAAC1, GLAST and GLT1, as well as LAT1, were analyzed. Also, the expression of the glutamate receptor N-methyl-D-aspartate (NMDAR) subunits NR2A and B as well as the presence of As species in cortex and hippocampus were investigated. On PND 90, an object location task was performed to associate exposure with memory impairment. Gestational exposure to iAs affected the expression of cysteine/glutamate transporters in cortex and hippocampus and induced a negative modulation of NMDAR NR2B subunit in the hippocampus. Behavioral tasks showed significant spatial memory impairment in males while the effect was marginal in females.

Neurological effects of inorganic arsenic exposure: altered cysteine/glutamate transport, NMDA expression and spatial memory impairment

PubMed Central

Ramos-Chávez, Lucio A.; Rendón-López, Christian R. R.; Zepeda, Angélica; Silva-Adaya, Daniela; Del Razo, Luz M.; Gonsebatt, María E.

2015-01-01

Inorganic arsenic (iAs) is an important natural pollutant. Millions of individuals worldwide drink water with high levels of iAs. Chronic exposure to iAs has been associated with lower IQ and learning disabilities as well as memory impairment. iAs is methylated in tissues such as the brain generating mono and dimethylated species. iAs methylation requires cellular glutathione (GSH), which is the main antioxidant in the central nervous system (CNS). In humans, As species cross the placenta and are found in cord blood. A CD1 mouse model was used to investigate effects of gestational iAs exposure which can lead to oxidative damage, disrupted cysteine/glutamate transport and its putative impact in learning and memory. On postnatal days (PNDs) 1, 15 and 90, the expression of membrane transporters related to GSH synthesis and glutamate transport and toxicity, such as xCT, EAAC1, GLAST and GLT1, as well as LAT1, were analyzed. Also, the expression of the glutamate receptor N-methyl-D-aspartate (NMDAR) subunits NR2A and B as well as the presence of As species in cortex and hippocampus were investigated. On PND 90, an object location task was performed to associate exposure with memory impairment. Gestational exposure to iAs affected the expression of cysteine/glutamate transporters in cortex and hippocampus and induced a negative modulation of NMDAR NR2B subunit in the hippocampus. Behavioral tasks showed significant spatial memory impairment in males while the effect was marginal in females. PMID:25709567

Hunger States Control the Directions of Synaptic Plasticity via Switching Cell Type-Specific Subunits of NMDA Receptors.

PubMed

Qi, Yong; Yang, Yunlei

2015-09-23

It remains largely unknown whether and how hunger states control activity-dependent synaptic plasticity, such as long-term potentiation (LTP) and long-term depression (LTD). We here report that both LTP and LTD of excitatory synaptic strength within the appetite control circuits residing in hypothalamic arcuate nucleus (ARC) behave in a manner of hunger states dependence and cell type specificity. For instance, we find that tetanic stimulation induces LTP at orexigenic agouti-related protein (AgRP) neurons in ad libitum fed mice, whereas it induces LTD in food-deprived mice. In an opposite direction, the same induction protocol induces LTD at anorexigenic pro-opiomelanocortin (POMC) neurons in fed mice but weak LTP in deprived mice. Mechanistically, we also find that food deprivation increases the expressions of NR2C/NR2D/NR3-containing NMDA receptors (NMDARs) at AgRP neurons that contribute to the inductions of LTD, whereas it decreases their expressions at POMC neurons. Collectively, our data reveal that hunger states control the directions of activity-dependent synaptic plasticity by switching NMDA receptor subpopulations in a cell type-specific manner, providing insights into NMDAR-mediated interactions between energy states and associative memory. Significance statement: Based on the experiments performed in this study, we demonstrate that activity-dependent synaptic plasticity is also under the control of energy states by regulating NMDAR subpopulations in a cell type-specific manner. We thus propose a reversible memory configuration constructed from energy states-dependent cell type-specific bidirectional conversions of LTP and LTD. Together with the distinct functional roles played by NMDAR signaling in the control of food intake and energy states, these findings reveal a new reciprocal interaction between energy states and associative memory, one that might serve as a target for therapeutic treatments of the energy-related memory disorders or vice versa. Copyright © 2015 the authors 0270-6474/15/3513171-12$15.00/0.

Benzoate, a D-amino acid oxidase inhibitor, for the treatment of early-phase Alzheimer disease: a randomized, double-blind, placebo-controlled trial.

PubMed

Lin, Chieh-Hsin; Chen, Ping-Kun; Chang, Yue-Cune; Chuo, Liang-Jen; Chen, Yan-Syun; Tsai, Guochuan E; Lane, Hsien-Yuan

2014-05-01

N-methyl-D-aspartate receptor (NMDAR)-mediated neurotransmission is vital for learning and memory. Hypofunction of NMDAR has been reported to play a role in the pathophysiology of Alzheimer disease (AD), particularly in the early phase. Enhancing NMDAR activation might be a novel treatment approach. One of the methods to enhance NMDAR activity is to raise the levels of NMDA coagonists by blocking their metabolism. This study examined the efficacy and safety of sodium benzoate, a D-amino acid oxidase inhibitor, for the treatment of amnestic mild cognitive impairment and mild AD. We conducted a randomized, double-blind, placebo-controlled trial in four major medical centers in Taiwan. Sixty patients with amnestic mild cognitive impairment or mild AD were treated with 250-750 mg/day of sodium benzoate or placebo for 24 weeks. Alzheimer's Disease Assessment Scale-cognitive subscale (the primary outcome) and global function (assessed by Clinician Interview Based Impression of Change plus Caregiver Input) were measured every 8 weeks. Additional cognition composite was measured at baseline and endpoint. Sodium benzoate produced a better improvement than placebo in Alzheimer's Disease Assessment Scale-cognitive subscale (p = .0021, .0116, and .0031 at week 16, week 24, and endpoint, respectively), additional cognition composite (p = .007 at endpoint) and Clinician Interview Based Impression of Change plus Caregiver Input (p = .015, .016, and .012 at week 16, week 24, and endpoint, respectively). Sodium benzoate was well-tolerated without evident side-effects. Sodium benzoate substantially improved cognitive and overall functions in patients with early-phase AD. The preliminary results show promise for D-amino acid oxidase inhibition as a novel approach for early dementing processes. Copyright © 2014 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Memantine, a Low-Affinity NMDA Receptor Antagonist, Protects against Methylmercury-Induced Cytotoxicity of Rat Primary Cultured Cortical Neurons, Involvement of Ca2+ Dyshomeostasis Antagonism, and Indirect Antioxidation Effects.

PubMed

Liu, Wei; Xu, Zhaofa; Yang, Tianyao; Xu, Bin; Deng, Yu; Feng, Shu

2017-09-01

Methylmercury (MeHg) is an extremely dangerous environmental pollutant that induces severe toxic effects in the central nervous system. Neuronal damage plays critical roles mediating MeHg-induced loss of brain function and neurotoxicity. The molecular mechanisms of MeHg neurotoxicity are incompletely understood. The objective of the study is to explore mechanisms that contribute to MeHg-induced neurocyte injuries focusing on neuronal Ca 2+ dyshomeostasis and alteration of N-methyl-D-aspartate receptors (NMDARs) expression, as well as oxidative stress in primary cultured cortical neurons. In addition, the neuroprotective effects of memantine against MeHg cytotoxicity were also investigated. The cortical neurons were exposed to 0, 0.01, 0.1, 1, or 2 μM methylmercury chloride (MeHgCl) for 0.5-12 h, or pre-treated with 2.5, 5, 10, or 20 μM memantine for 0.5-6 h, respectively; cell viability and LDH release were then quantified. For further experiments, 2.5, 5, and 10 μM of memantine pre-treatment for 3 h followed by 1 μM MeHgCl for 6 h were performed for evaluation of neuronal injuries, specifically addressing apoptosis; intracellular free Ca 2+ concentrations; ATPase activities; calpain activities; expressions of NMDAR subunits (NR1, NR2A, NR2B); NPSH levels; and ROS formation. Exposure of MeHgCl resulted in toxicity of cortical neurons, which were shown as a loss of cell viability, high levels of LDH release, morphological changes, and cell apoptosis. Moreover, intracellular Ca 2+ dyshomeostasis, ATPase activities inhibition, calpain activities, and NMDARs expression alteration were observed with 1 μM MeHgCl administration. Last but not least, NPSH depletion and reactive oxygen species (ROS) overproduction showed an obvious oxidative stress in neurons. However, memantine pre-treatment dose-dependently antagonized MeHg-induced neuronal toxic effects, apoptosis, Ca 2+ dyshomeostasis, NMDARs expression alteration, and oxidative stress. In conclusion, the cytoprotective effects of memantine against MeHg appeared to be mediated not only via its NMDAR binding properties and Ca 2+ homeostasis maintenance but also by indirect antioxidation effects.

Prediction of N-Methyl-D-Aspartate Receptor GluN1-Ligand Binding Affinity by a Novel SVM-Pose/SVM-Score Combinatorial Ensemble Docking Scheme

PubMed Central

Leong, Max K.; Syu, Ren-Guei; Ding, Yi-Lung; Weng, Ching-Feng

2017-01-01

The glycine-binding site of the N-methyl-D-aspartate receptor (NMDAR) subunit GluN1 is a potential pharmacological target for neurodegenerative disorders. A novel combinatorial ensemble docking scheme using ligand and protein conformation ensembles and customized support vector machine (SVM)-based models to select the docked pose and to predict the docking score was generated for predicting the NMDAR GluN1-ligand binding affinity. The predicted root mean square deviation (RMSD) values in pose by SVM-Pose models were found to be in good agreement with the observed values (n = 30, r2 = 0.928–0.988,  = 0.894–0.954, RMSE = 0.002–0.412, s = 0.001–0.214), and the predicted pKi values by SVM-Score were found to be in good agreement with the observed values for the training samples (n = 24, r2 = 0.967,  = 0.899, RMSE = 0.295, s = 0.170) and test samples (n = 13, q2 = 0.894, RMSE = 0.437, s = 0.202). When subjected to various statistical validations, the developed SVM-Pose and SVM-Score models consistently met the most stringent criteria. A mock test asserted the predictivity of this novel docking scheme. Collectively, this accurate novel combinatorial ensemble docking scheme can be used to predict the NMDAR GluN1-ligand binding affinity for facilitating drug discovery. PMID:28059133

Prediction of N-Methyl-D-Aspartate Receptor GluN1-Ligand Binding Affinity by a Novel SVM-Pose/SVM-Score Combinatorial Ensemble Docking Scheme.

PubMed

Leong, Max K; Syu, Ren-Guei; Ding, Yi-Lung; Weng, Ching-Feng

2017-01-06

The glycine-binding site of the N-methyl-D-aspartate receptor (NMDAR) subunit GluN1 is a potential pharmacological target for neurodegenerative disorders. A novel combinatorial ensemble docking scheme using ligand and protein conformation ensembles and customized support vector machine (SVM)-based models to select the docked pose and to predict the docking score was generated for predicting the NMDAR GluN1-ligand binding affinity. The predicted root mean square deviation (RMSD) values in pose by SVM-Pose models were found to be in good agreement with the observed values (n = 30, r 2  = 0.928-0.988,  = 0.894-0.954, RMSE = 0.002-0.412, s = 0.001-0.214), and the predicted pK i values by SVM-Score were found to be in good agreement with the observed values for the training samples (n = 24, r 2  = 0.967,  = 0.899, RMSE = 0.295, s = 0.170) and test samples (n = 13, q 2  = 0.894, RMSE = 0.437, s = 0.202). When subjected to various statistical validations, the developed SVM-Pose and SVM-Score models consistently met the most stringent criteria. A mock test asserted the predictivity of this novel docking scheme. Collectively, this accurate novel combinatorial ensemble docking scheme can be used to predict the NMDAR GluN1-ligand binding affinity for facilitating drug discovery.

Prediction of N-Methyl-D-Aspartate Receptor GluN1-Ligand Binding Affinity by a Novel SVM-Pose/SVM-Score Combinatorial Ensemble Docking Scheme

NASA Astrophysics Data System (ADS)

Leong, Max K.; Syu, Ren-Guei; Ding, Yi-Lung; Weng, Ching-Feng

2017-01-01

The glycine-binding site of the N-methyl-D-aspartate receptor (NMDAR) subunit GluN1 is a potential pharmacological target for neurodegenerative disorders. A novel combinatorial ensemble docking scheme using ligand and protein conformation ensembles and customized support vector machine (SVM)-based models to select the docked pose and to predict the docking score was generated for predicting the NMDAR GluN1-ligand binding affinity. The predicted root mean square deviation (RMSD) values in pose by SVM-Pose models were found to be in good agreement with the observed values (n = 30, r2 = 0.928-0.988,  = 0.894-0.954, RMSE = 0.002-0.412, s = 0.001-0.214), and the predicted pKi values by SVM-Score were found to be in good agreement with the observed values for the training samples (n = 24, r2 = 0.967,  = 0.899, RMSE = 0.295, s = 0.170) and test samples (n = 13, q2 = 0.894, RMSE = 0.437, s = 0.202). When subjected to various statistical validations, the developed SVM-Pose and SVM-Score models consistently met the most stringent criteria. A mock test asserted the predictivity of this novel docking scheme. Collectively, this accurate novel combinatorial ensemble docking scheme can be used to predict the NMDAR GluN1-ligand binding affinity for facilitating drug discovery.

Memantine and Ketamine Differentially Alter NMDA Receptor Desensitization

PubMed Central

Povysheva, Nadezhda V.; Azofeifa, Andrea M.

2017-01-01

Memantine and ketamine are clinically useful NMDA receptor (NMDAR) open channel blockers that inhibit NMDARs with similar potency and kinetics, but display vastly different clinical profiles. This discrepancy has been hypothesized to result from inhibition by memantine and ketamine of overlapping but distinct NMDAR subpopulations. For example, memantine but not ketamine may inhibit extrasynaptic NMDARs more effectively than synaptic NMDARs. However, the basis for preferential NMDAR inhibition depending on subcellular location has not been investigated systematically. We integrated recordings from heterologously expressed single NMDAR subtypes, kinetic modeling, and recordings of synaptically evoked NMDAR responses in acute brain slices to investigate mechanisms by which channel blockers may distinguish NMDAR subpopulations. We found that memantine and ketamine differentially alter NMDAR desensitization and that memantine stabilizes a Ca2+-dependent desensitized state. As a result, inhibition by memantine of GluN1/2A receptors in tsA201 cells and of native synaptic NMDARs in cortical pyramidal neurons from mice of either sex increased in conditions that enhanced intracellular Ca2+ accumulation. Therefore, differential inhibition by memantine and ketamine based on NMDAR location is likely to result from location dependence of the intensity and duration of NMDAR activation. Modulation of Ca2+-dependent NMDAR desensitization is an unexplored mechanism of inhibitory action with the potential to endow drugs with NMDAR selectivity that leads to superior clinical profiles. Our results suggest that designing compounds to target specific receptor states, rather than specific receptor types, may be a viable strategy for future drug development. SIGNIFICANCE STATEMENT Memantine and ketamine are NMDA receptor (NMDAR) channel-blocking drugs with divergent clinical effects. Understanding mechanistically their differential actions may advance our understanding of nervous system disorders and suggest strategies for the design of more effective drugs. Here, we show that memantine and ketamine have contrasting effects on NMDAR desensitization. Ketamine binding decreases occupancy of desensitized states of the GluN1/2B NMDAR subtype. In contrast, memantine binding increases occupancy of GluN1/2A and native NMDAR desensitized states entered after accumulation of intracellular Ca2+, a novel inhibitory mechanism. These properties may contribute to inhibition of distinct NMDAR subpopulations by memantine and ketamine and help to explain their differential clinical effects. Our results suggest stabilization of Ca2+-dependent desensitized states as a new strategy for pharmaceutical neuroprotection. PMID:28877967

Memantine and Ketamine Differentially Alter NMDA Receptor Desensitization.

PubMed

Glasgow, Nathan G; Povysheva, Nadezhda V; Azofeifa, Andrea M; Johnson, Jon W

2017-10-04

Memantine and ketamine are clinically useful NMDA receptor (NMDAR) open channel blockers that inhibit NMDARs with similar potency and kinetics, but display vastly different clinical profiles. This discrepancy has been hypothesized to result from inhibition by memantine and ketamine of overlapping but distinct NMDAR subpopulations. For example, memantine but not ketamine may inhibit extrasynaptic NMDARs more effectively than synaptic NMDARs. However, the basis for preferential NMDAR inhibition depending on subcellular location has not been investigated systematically. We integrated recordings from heterologously expressed single NMDAR subtypes, kinetic modeling, and recordings of synaptically evoked NMDAR responses in acute brain slices to investigate mechanisms by which channel blockers may distinguish NMDAR subpopulations. We found that memantine and ketamine differentially alter NMDAR desensitization and that memantine stabilizes a Ca 2+ -dependent desensitized state. As a result, inhibition by memantine of GluN1/2A receptors in tsA201 cells and of native synaptic NMDARs in cortical pyramidal neurons from mice of either sex increased in conditions that enhanced intracellular Ca 2+ accumulation. Therefore, differential inhibition by memantine and ketamine based on NMDAR location is likely to result from location dependence of the intensity and duration of NMDAR activation. Modulation of Ca 2+ -dependent NMDAR desensitization is an unexplored mechanism of inhibitory action with the potential to endow drugs with NMDAR selectivity that leads to superior clinical profiles. Our results suggest that designing compounds to target specific receptor states, rather than specific receptor types, may be a viable strategy for future drug development. SIGNIFICANCE STATEMENT Memantine and ketamine are NMDA receptor (NMDAR) channel-blocking drugs with divergent clinical effects. Understanding mechanistically their differential actions may advance our understanding of nervous system disorders and suggest strategies for the design of more effective drugs. Here, we show that memantine and ketamine have contrasting effects on NMDAR desensitization. Ketamine binding decreases occupancy of desensitized states of the GluN1/2B NMDAR subtype. In contrast, memantine binding increases occupancy of GluN1/2A and native NMDAR desensitized states entered after accumulation of intracellular Ca 2+ , a novel inhibitory mechanism. These properties may contribute to inhibition of distinct NMDAR subpopulations by memantine and ketamine and help to explain their differential clinical effects. Our results suggest stabilization of Ca 2+ -dependent desensitized states as a new strategy for pharmaceutical neuroprotection. Copyright © 2017 the authors 0270-6474/17/379686-19$15.00/0.

Undifferentiated embryonic stem cells express ionotropic glutamate receptor mRNAs

PubMed Central

Pachernegg, Svenja; Joshi, Illah; Muth-Köhne, Elke; Pahl, Steffen; Münster, Yvonne; Terhag, Jan; Karus, Michael; Werner, Markus; Ma-Högemeier, Zhan-Lu; Körber, Christoph; Grunwald, Thomas; Faissner, Andreas; Wiese, Stefan; Hollmann, Michael

2013-01-01

Ionotropic glutamate receptors (iGluRs) do not only mediate the majority of excitatory neurotransmission in the vertebrate CNS, but also modulate pre- and postnatal neurogenesis. Most of the studies on the developmental role of iGluRs are performed on neural progenitors and neural stem cells (NSCs). We took a step back in our study by examining the role of iGluRs in the earliest possible cell type, embryonic stem cells (ESCs), by looking at the mRNA expression of the major iGluR subfamilies in undifferentiated mouse ESCs. For that, we used two distinct murine ES cell lines, 46C ESCs and J1 ESCs. Regarding 46C ESCs, we found transcripts of kainate receptors (KARs) (GluK2 to GluK5), AMPA receptors (AMPARs) (GluA1, GluA3, and GluA4), and NMDA receptors (NMDARs) (GluN1, and GluN2A to GluN2D). Analysis of 46C-derived cells of later developmental stages, namely neuroepithelial precursor cells (NEPs) and NSCs, revealed that the mRNA expression of KARs is significantly upregulated in NEPs and, subsequently, downregulated in NSCs. However, we could not detect any protein expression of any of the KAR subunits present on the mRNA level either in ESCs, NEPs, or NSCs. Regarding AMPARs and NMDARs, GluN2A is weakly expressed at the protein level only in NSCs. Matching our findings for iGluRs, all three cell types were found to weakly express pre- and postsynaptic markers of glutamatergic synapses only at the mRNA level. Finally, we performed patch-clamp recordings of 46C ESCs and could not detect any current upon iGluR agonist application. Similar to 46C ESCs, J1 ESCs express KARs (GluK2 to GluK5), AMPARs (GluA3), and NMDARs (GluN1, and GluN2A to GluN2D) at the mRNA level, but these transcripts are not translated into receptor proteins either. Thus, we conclude that ESCs do not contain functional iGluRs, although they do express an almost complete set of iGluR subunit mRNAs. PMID:24348335

Antagonism at the NR2B subunit of NMDA receptors induces increased connectivity of the prefrontal and subcortical regions regulating reward behavior.

PubMed

Gass, Natalia; Becker, Robert; Sack, Markus; Schwarz, Adam J; Reinwald, Jonathan; Cosa-Linan, Alejandro; Zheng, Lei; von Hohenberg, Christian Clemm; Inta, Dragos; Meyer-Lindenberg, Andreas; Weber-Fahr, Wolfgang; Gass, Peter; Sartorius, Alexander

2018-04-01

Evidence indicates that ketamine's rapid antidepressant efficacy likely results from its antagonism of NR2B-subunit-containing NMDA receptors (NMDAR). Since ketamine equally blocks NR2A- and NR2B-containing NMDAR, and has affinity to other receptors, NR2B-selective drugs might have improved therapeutic efficiency and side effect profile. We aimed to compare the effects of (S)-ketamine and two different types of NR2B-selective antagonists on functional brain networks in rats, in order to find common circuits, where their effects intersect, and that might explain their antidepressant action. The experimental design comprised four parallel groups of rats (N = 37), each receiving (S)-Ketamine, CP-101,606, Ro 25-6981 or saline. After compound injection, we acquired resting-state functional magnetic resonance imaging time series. We used graph theoretical approach to calculate brain network properties. Ketamine and CP-101,606 diminished the global clustering coefficient and small-worldness index. At the nodal level, all compounds induced increased connectivity of the regions mediating reward and cognitive aspects of emotional processing, such as ventromedial prefrontal cortex, septal nuclei, and nucleus accumbens. The dorsal hippocampus and regions involved in sensory processing and aversion, such as superior and inferior colliculi, exhibited an opposite effect. The effects common to ketamine and NR2B-selective compounds were localized to the same brain regions as those reported in depression, but in the opposite direction. The upregulation of the reward circuitry might partially underlie the antidepressant and anti-anhedonic effects of the antagonists and could potentially serve as a translational imaging phenotype for testing putative antidepressants, especially those targeting the NR2B receptor subtype.

Glutamatergic targets for new alcohol medications

PubMed Central

Spanagel, Rainer; Krystal, John H.

2013-01-01

Rationale An increasingly compelling literature points to a major role for the glutamate system in mediating the effects of alcohol on behavior and the pathophysiology of alcoholism. Preclinical studies indicate that glutamate signaling mediates certain aspects of ethanol’s intoxicating and rewarding effects, and undergoes adaptations following chronic alcohol exposure that may contribute to the withdrawal, craving and compulsive drug-seeking that drive alcohol abuse and alcoholism. Objectives We discuss the potential for targeting the glutamate system as a novel pharmacotherapeutic approach to treating alcohol use disorders, focusing on five major components of the glutamate system: the N-methyl-D-aspartate (NMDA) receptor and specific NMDA subunits, the glycineB site on the NMDA receptors (NMDAR), L-alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid ionotropic (AMPA) and kainate (KAR) receptors, metabotropic receptors (mGluR), and glutamate transporters. Results Chronic alcohol abuse produces a hyperglutamatergic state, characterized by elevated extracellular glutamate and altered glutamate receptors and transporters. Pharmacologically manipulating glutamatergic neurotransmission alters alcohol-related behaviors including intoxication, withdrawal, and alcohol-seeking, in rodents and human subjects. Blocking NMDA and AMPA receptors reduces alcohol consumption in rodents, but side-effects may limit this as a therapeutic approach. Selectively targeting NMDA and AMPA receptor subunits (e.g., GluN2B, GluA3), or the NMDAR glycineB site offers an alternative approach. Blocking mGluR5 potently affects various alcohol-related behaviors in rodents, and mGluR2/3 agonism also suppresses alcohol consumption. Finally, glutamate transporter upregulation may mitigate behavioral and neurotoxic sequelae of excess glutamate caused by alcohol. Conclusions Despite the many challenges that remain, targeting the glutamate system offers genuine promise for developing new treatments for alcoholism. PMID:23995381

Morphine and MK-801 administration leads to alternative NMDAR1 splicing and associated changes in reward seeking behavior and nociception on an operant orofacial assay

PubMed Central

Anderson, Ethan M.; Del Valle-Pinero, Arseima Y.; Suckow, Shelby K.; Nolan, Todd A.; Neubert, John K.; Caudle, Robert M.

2012-01-01

The NMDA receptor plays a large role in opioid-induced plastic changes in the nervous system. The expression levels of its NR1 subunit are altered dramatically by morphine but no changes in its alternative splicing have been reported. Changes in the splicing of the N1, C1, C2, and C2’ cassettes can alter the pharmacology and regulation of this receptor. Western blots run on brain tissue from rats made tolerant to morphine revealed altered splicing of the N1 cassettes in the accumbens and amygdala, and the C1 cassette in the amygdala and the dorsal hippocampus. After three days of withdrawal C2’-containing NR1 subunits were down-regulated in each of these areas. These were not due to acute doses of morphine and may represent long term alterations in drug-induced neuroplasticity. We also examined the effects of morphine tolerance on an operant orofacial nociception assay which forces an animal to endure an aversive heat stimulus in order to receive a sweet milk reward. Morphine decreased pain sensitivity as expected but also increased motivational reward seeking in this task. NMDAR antagonism potentiated this reward seeking behavior suggesting that instead of attenuating tolerance, MK-801 may actually alter the rewarding and/or motivational properties of morphine. When combined, MK-801 and morphine had an additive effect which led to altered splicing in the accumbens, amygdala, and the dorsal hippocampus. In conclusion, NR1 splicing may play a major role in the cognitive behavioral aspects especially in motivational reward seeking behaviors. PMID:22531378

Schizophrenia-like GABAergic gene expression deficits in cerebellar Golgi cells from rats chronically exposed to low-dose phencyclidine

PubMed Central

Bullock, W. Michael; Bolognani, Federico; Botta, Paolo; Valenzuela, C. Fernando; Perrone-Bizzozero, Nora I.

2009-01-01

One of the most consistent findings in schizophrenia is the decreased expression of the GABA synthesizing enzymes GAD67 and GAD65 in specific interneuron populations. This dysfunction is observed in distributed brain regions including the prefrontal cortex, hippocampus, and cerebellum. In an effort to understand the mechanisms for this GABA deficit, we investigated the effect of the N-methyl-D-aspartate receptor (NMDAR) antagonist phencyclidine (PCP), which elicits schizophrenia-like symptoms in both humans and animal models, in a chronic, low-dose exposure paradigm. Adult rats were given PCP at a dose of 2.58 mg/kg/day i.p. for a month, after which levels of various GABAergic cell mRNAs and other neuromodulators were examined in the cerebellum by RT-qPCR. Administration of PCP decreased the expression of GAD67, GAD65, and the presynaptic GABA transporter GAT-1, and increased GABAA receptor subunits similar to those seen in patients with schizophrenia. Additionally, we found that the mRNA levels of two Golgi cell selective NMDAR subunits, NR2B and NR2D, were decreased in PCP treated rats. Furthermore, we localized the deficits in GAD67 expression solely to these interneurons. Slice electrophysiological studies showed that spontaneous firing of Golgi cells was reduced by acute exposure to low dose PCP, suggesting that these neurons are particularly vulnerable to NMDA receptor antagonism. In conclusion, our results demonstrate that chronic exposure to low levels of PCP in rats mimics the GABAergic alterations reported in the cerebellum of patients with schizophrenia (Bullock et al., Am J Psychiatry 165: 1594-1603, 2008), further supporting the validity of this animal model. PMID:19651169

Peripheral Elevation of a Klotho Fragment Enhances Brain Function and Resilience in Young, Aging, and α-Synuclein Transgenic Mice.

PubMed

Leon, Julio; Moreno, Arturo J; Garay, Bayardo I; Chalkley, Robert J; Burlingame, Alma L; Wang, Dan; Dubal, Dena B

2017-08-08

Cognitive dysfunction and decreased mobility from aging and neurodegenerative conditions, such as Parkinson and Alzheimer diseases, are major biomedical challenges in need of more effective therapies. Increasing brain resilience may represent a new treatment strategy. Klotho, a longevity factor, enhances cognition when genetically and broadly overexpressed in its full, wild-type form over the mouse lifespan. Whether acute klotho treatment can rapidly enhance cognitive and motor functions or induce resilience is a gap in our knowledge of its therapeutic potential. Here, we show that an α-klotho protein fragment (αKL-F), administered peripherally, surprisingly induced cognitive enhancement and neural resilience despite impermeability to the blood-brain barrier in young, aging, and transgenic α-synuclein mice. αKL-F treatment induced cleavage of the NMDAR subunit GluN2B and also enhanced NMDAR-dependent synaptic plasticity. GluN2B blockade abolished αKL-F-mediated effects. Peripheral αKL-F treatment is sufficient to induce neural enhancement and resilience in mice and may prove therapeutic in humans. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Lack of Pannexin 1 Alters Synaptic GluN2 Subunit Composition and Spatial Reversal Learning in Mice.

PubMed

Gajardo, Ivana; Salazar, Claudia S; Lopez-Espíndola, Daniela; Estay, Carolina; Flores-Muñoz, Carolina; Elgueta, Claudio; Gonzalez-Jamett, Arlek M; Martínez, Agustín D; Muñoz, Pablo; Ardiles, Álvaro O

2018-01-01

Long-term potentiation (LTP) and long-term depression (LTD) are two forms of synaptic plasticity that have been considered as the cellular substrate of memory formation. Although LTP has received considerable more attention, recent evidences indicate that LTD plays also important roles in the acquisition and storage of novel information in the brain. Pannexin 1 (Panx1) is a membrane protein that forms non-selective channels which have been shown to modulate the induction of hippocampal synaptic plasticity. Animals lacking Panx1 or blockade of Pannexin 1 channels precludes the induction of LTD and facilitates LTP. To evaluate if the absence of Panx1 also affects the acquisition of rapidly changing information we trained Panx1 knockout (KO) mice and wild type (WT) littermates in a visual and hidden version of the Morris water maze (MWM). We found that KO mice find the hidden platform similarly although slightly quicker than WT animals, nonetheless, when the hidden platform was located in the opposite quadrant (OQ) to the previous learned location, KO mice spent significantly more time in the previous quadrant than in the new location indicating that the absence of Panx1 affects the reversion of a previously acquired spatial memory. Consistently, we observed changes in the content of synaptic proteins critical to LTD, such as GluN2 subunits of N-methyl-D-aspartate receptors (NMDARs), which changed their contribution to synaptic plasticity in conditions of Panx1 ablation. Our findings give further support to the role of Panx1 channels on the modulation of synaptic plasticity induction, learning and memory processes.

GluN2C/GluN2D subunit-selective NMDA receptor potentiator CIQ reverses MK-801-induced impairment in prepulse inhibition and working memory in Y-maze test in mice

PubMed Central

Suryavanshi, P S; Ugale, R R; Yilmazer-Hanke, D; Stairs, D J; Dravid, S M

2014-01-01

Background and Purpose Despite ample evidence supporting the N-methyl-d-aspartate receptor (NMDAR) hypofunction hypothesis of schizophrenia, progress in the development of effective therapeutics based on this hypothesis has been limited. Facilitation of NMDA receptor function by co-agonists (d-serine or glycine) only partially alleviates the symptoms in schizophrenia; other means to facilitate NMDA receptors are required. NMDA receptor sub-types differ in their subunit composition, with varied GluN2 subunits (GluN2A-GluN2D) imparting different physiological, biochemical and pharmacological properties. CIQ is a positive allosteric modulator that is selective for GluN2C/GluN2D-containing NMDA receptors (Mullasseril et al.). Experimental Approach The effect of systemic administration of CIQ was tested on impairment in prepulse inhibition (PPI), hyperlocomotion and stereotypy induced by i.p. administration of MK-801 and methamphetamine. The effect of CIQ was also tested on MK-801-induced impairment in working memory in Y-maze spontaneous alternation test. Key Results We found that systemic administration of CIQ (20 mg·kg−1, i.p.) in mice reversed MK-801 (0.15 mg·kg−1, i.p.)-induced, but not methamphetamine (3 mg·kg−1, i.p.)-induced, deficit in PPI. MK-801 increased the startle amplitude to pulse alone, which was not reversed by CIQ. In contrast, methamphetamine reduced the startle amplitude to pulse alone, which was reversed by CIQ. CIQ also partially attenuated MK-801- and methamphetamine-induced hyperlocomotion and stereotyped behaviours. Additionally, CIQ reversed the MK-801-induced working memory deficit in spontaneous alternation in a Y-maze. Conclusion and Implications Together, these results suggest that facilitation of GluN2C/GluN2D-containing receptors may serve as an important therapeutic strategy for treating positive and cognitive symptoms in schizophrenia. PMID:24236947

Hypothyroidism in the adult rat causes incremental changes in brain-derived neurotrophic factor, neuronal and astrocyte apoptosis, gliosis, and deterioration of postsynaptic density.

PubMed

Cortés, Claudia; Eugenin, Eliseo; Aliaga, Esteban; Carreño, Leandro J; Bueno, Susan M; Gonzalez, Pablo A; Gayol, Silvina; Naranjo, David; Noches, Verónica; Marassi, Michelle P; Rosenthal, Doris; Jadue, Cindy; Ibarra, Paula; Keitel, Cecilia; Wohllk, Nelson; Court, Felipe; Kalergis, Alexis M; Riedel, Claudia A

2012-09-01

Adult hypothyroidism is a highly prevalent condition that impairs processes, such as learning and memory. Even though tetra-iodothyronine (T(4)) treatment can overcome the hypothyroidism in the majority of cases, it cannot fully recover the patient's learning capacity and memory. In this work, we analyzed the cellular and molecular changes in the adult brain occurring with the development of experimental hypothyroidism. Adult male Sprague-Dawley rats were treated with 6-propyl-2-thiouracil (PTU) for 20 days to induce hypothyroidism. Neuronal and astrocyte apoptosis were analyzed in the hippocampus of control and hypothyroid adult rats by confocal microscopy. The content of brain-derived neurotrophic factor (BDNF) was analyzed using enzyme-linked immunosorbent assay (ELISA) and in situ hybridization. The glutamatergic synapse and the postsynaptic density (PSD) were analyzed by electron microscopy. The content of PSD proteins like tyrosine receptor kinase B (TrkB), p75, and N-methyl-D-aspartate receptor (NMDAr) were analyzed by immunoblot. We observed that the hippocampus of hypothyroid adult rats displayed increased apoptosis levels in neurons and astrocyte and reactive gliosis compared with controls. Moreover, we found that the amount of BDNF mRNA was higher in the hippocampus of hypothyroid rats and the content of TrkB, the receptor for BDNF, was reduced at the PSD of the CA3 region of hypothyroid rats, compared with controls. We also observed that the glutamatergic synapses from the stratum radiatum of CA3 from hypothyroid rats, contained thinner PSDs than control rats. This observation was in agreement with a reduced content of NMDAr subunits at the PSD in hypothyroid animals. Our data suggest that adult hypothyroidism affects the hippocampus by a mechanism that alters the composition of PSD, reduces neuronal and astrocyte survival, and alters the content of the signaling neurotrophic factors, such as BDNF.

Regulated internalization of NMDA receptors drives PKD1-mediated suppression of the activity of residual cell-surface NMDA receptors.

PubMed

Fang, Xiao-Qian; Qiao, Haifa; Groveman, Bradley R; Feng, Shuang; Pflueger, Melissa; Xin, Wen-Kuan; Ali, Mohammad K; Lin, Shuang-Xiu; Xu, Jindong; Duclot, Florian; Kabbaj, Mohamed; Wang, Wei; Ding, Xin-Sheng; Santiago-Sim, Teresa; Jiang, Xing-Hong; Salter, Michael W; Yu, Xian-Min

2015-11-19

Constitutive and regulated internalization of cell surface proteins has been extensively investigated. The regulated internalization has been characterized as a principal mechanism for removing cell-surface receptors from the plasma membrane, and signaling to downstream targets of receptors. However, so far it is still not known whether the functional properties of remaining (non-internalized) receptor/channels may be regulated by internalization of the same class of receptor/channels. The N-methyl-D-aspartate receptor (NMDAR) is a principal subtype of glutamate-gated ion channel and plays key roles in neuronal plasticity and memory functions. NMDARs are well-known to undergo two types of regulated internalization - homologous and heterologous, which can be induced by high NMDA/glycine and DHPG, respectively. In the present work, we investigated effects of regulated NMDAR internalization on the activity of residual cell-surface NMDARs and neuronal functions. In electrophysiological experiments we discovered that the regulated internalization of NMDARs not only reduced the number of cell surface NMDARs but also caused an inhibition of the activity of remaining (non-internalized) surface NMDARs. In biochemical experiments we identified that this functional inhibition of remaining surface NMDARs was mediated by increased serine phosphorylation of surface NMDARs, resulting from the activation of protein kinase D1 (PKD1). Knockdown of PKD1 did not affect NMDAR internalization but prevented the phosphorylation and inhibition of remaining surface NMDARs and NMDAR-mediated synaptic functions. These data demonstrate a novel concept that regulated internalization of cell surface NMDARs not only reduces the number of NMDARs on the cell surface but also causes an inhibition of the activity of remaining surface NMDARs through intracellular signaling pathway(s). Furthermore, modulating the activity of remaining surface receptors may be an effective approach for treating receptor internalization-induced changes in neuronal functions of the CNS.

α7nAchR/NMDAR coupling affects NMDAR function and object recognition.

PubMed

Li, Shupeng; Nai, Qiang; Lipina, Tatiana V; Roder, John C; Liu, Fang

2013-12-20

The α7 nicotinic acetylcholine receptor (nAchR) and NMDA glutamate receptor (NMDAR) are both ligand-gated ion channels permeable to Ca2+ and Na+. Previous studies have demonstrated functional modulation of NMDARs by nAchRs, although the molecular mechanism remains largely unknown. We have previously reported that α7nAchR forms a protein complex with the NMDAR through a protein-protein interaction. We also developed an interfering peptide that is able to disrupt the α7nAchR-NMDAR complex and blocks cue-induced reinstatement of nicotine-seeking in rat models of relapse. In the present study, we investigated whether the α7nAchR-NMDAR interaction is responsible for the functional modulation of NMDAR by α7nAchR using both electrophysiological and behavioral tests. We have found that activation of α7nAchR upregulates NMDAR-mediated whole cell currents and LTP of mEPSC in cultured hippocampal neurons, which can be abolished by the interfering peptide that disrupts the α7nAchR-NMDAR interaction. Moreover, administration of the interfering peptide in mice impairs novel object recognition but not Morris water maze performance. Our results suggest that α7nAchR/NMDAR coupling may selectively affect some aspects of learning and memory.

Effects of the GluN2B-NMDA receptor antagonist Ro 25-6981 on two types of behavioral flexibility in rats.

PubMed

Clark, Emma; Antoniak, Kristen; Feniquito, Alyssandra; Dringenberg, Hans C

2017-02-15

Recent evidence has implicated N-methyl-d-aspartate receptors (NMDARs) in several aspects of learning and behavioral flexibility in rodents. Here, we examined the effects of treatment with Ro 25-6981, a selective antagonist of NMDARs containing GluN2B subunits, on two types of behavioral flexibility in rats, spatial reversal learning and set-shifting (spatial vs. motor strategy). To examine spatial reversal learning, rats were trained to swim to a hidden platform in a water maze over four days. On the following day, the platform was moved to a new location in the maze. Administration of Ro 25-6981 (10mg/kg) selectively impaired the early phase of reversal learning, but all rats learned to navigate to the new platform location over 12 trials. To examine set-shifting, independent groups of rats were trained to either swim to a fixed location (spatial strategy) or use a motor response (e.g., "turn left"; motor strategy) to find a hidden escape platform in a cross-shaped water maze apparatus; after task acquisition, rats were trained on the second, novel strategy (set-shift) following treatment with either Ro 25-6981 (10mg/kg) or saline. Administration of Ro 25-6981 had no effect on the ability of rats to perform the set-shift and use the new strategy to locate the escape platform. These results suggest that, in rats, spatial reversal learning, but not set-shifting, is sensitive to Ro-25-6981 treatment. Thus, NMDARs-GluN2B signaling may play a selective role in some forms of behavioral plasticity, particularly for situations involving the updating of information in the spatial domain. Copyright © 2016 Elsevier B.V. All rights reserved.

The effect of soybean isoflavone on the dysregulation of NMDA receptor signaling pathway induced by β-amyloid peptides 1-42 in rats.

PubMed

Xi, Yuan-Di; Ding, Juan; Han, Jing; Zhang, Dan-Di; Liu, Jin-Meng; Feng, Ling-Li; Xiao, Rong

2015-05-01

Synaptic damage is the key factor of cognitive impairment. The purpose of this study was to understand the effect of soybean isoflavone (SIF) on synaptic damage induced by β-amyloid peptide 1-42 (Aβ1-42) in rats. Adult male Wistar rats were randomly divided into control, Aβ1-42, SIF, and SIF + Aβ1-42 (SIF pretreatment) groups according to body weight. SIF was treated orally by gavage in SIF and SIF + Aβ1-42 groups. After 14 days pretreatment with SIF or vehicle, Aβ1-42 was injected into the lateral cerebral ventricle of rats in Aβ1-42 and SIF + Aβ1-42 groups using miniosmotic pump. The level of Aβ1-42 and the expression of N-methyl-D-aspartic-acid receptor (NMDAR) were observed by immunohistochemistry. Reverse transcriptase polymerase chain reaction was used to detect the mRNA levels of NMDAR, calmodulin (CaM), calcium/CaM-dependent protein kinase II (CaMKII), cAMP-response element binding protein (CREB), and brain-derived neurotrophic factor (BDNF). The results showed that Aβ1-42 down-regulated mRNA and protein expression of the NR1 and NR2B subunits of NMDAR, SIF pretreatment could reverse these changes. The mRNA expression of CaM, CaMKII, CREB, and BDNF were down-regulated by Aβ1-42, but they were all regulated by SIF pretreatment. These results suggest that SIF pretreatment could antagonize the neuron damage in rats induced by Aβ1-42, and its mechanism might be associated with the NMDA receptor and CaM/CaMKII/CREB/BDNF signaling pathway, which are the synaptic plasticity-related molecules.

Age-related NMDA signaling alterations in SOD2 deficient mice.

PubMed

Carvajal, Francisco J; Mira, Rodrigo G; Rovegno, Maximiliano; Minniti, Alicia N; Cerpa, Waldo

2018-06-01

Oxidative stress affects the survival and function of neurons. Hence, they have a complex and highly regulated machinery to handle oxidative changes. The dysregulation of this antioxidant machinery is associated with a wide range of neurodegenerative conditions. Therefore, we evaluated signaling alterations, synaptic properties and behavioral performance in 2 and 6-month-old heterozygous manganese superoxide dismutase knockout mice (SOD2 +/- mice). We found that their low antioxidant capacity generated direct oxidative damage in proteins, lipids, and DNA. However, only 6-month-old heterozygous knockout mice presented behavioral impairments. On the other hand, synaptic plasticity, synaptic strength and NMDA receptor (NMDAR) dependent postsynaptic potentials were decreased in an age-dependent manner. We also analyzed the phosphorylation state of the NMDAR subunit GluN2B. We found that while the levels of GluN2B phosphorylated on tyrosine 1472 (synaptic form) remain unchanged, we detected increased levels of GluN2B phosphorylated on tyrosine 1336 (extrasynaptic form), establishing alterations in the synaptic/extrasynaptic ratio of GluN2B. Additionally, we found increased levels of two phosphatases associated with dephosphorylation of p-1472: striatal-enriched protein tyrosine phosphatase (STEP) and phosphatase and tensin homolog deleted on chromosome Ten (PTEN). Moreover, we found decreased levels of p-CREB, a master transcription factor activated by synaptic stimulation. In summary, we describe mechanisms by which glutamatergic synapses are altered under oxidative stress conditions. Our results uncovered new putative therapeutic targets for conditions where NMDAR downstream signaling is altered. This work also contributes to our understanding of processes such as synapse formation, learning, and memory in neuropathological conditions. Copyright © 2018 Elsevier B.V. All rights reserved.

Pin1 Modulates the Synaptic Content of NMDA Receptors via Prolyl-Isomerization of PSD-95.

PubMed

Antonelli, Roberta; De Filippo, Roberto; Middei, Silvia; Stancheva, Stefka; Pastore, Beatrice; Ammassari-Teule, Martine; Barberis, Andrea; Cherubini, Enrico; Zacchi, Paola

2016-05-18

Phosphorylation of serine/threonine residues preceding a proline regulates the fate of its targets through postphosphorylation conformational changes catalyzed by the peptidyl-prolyl cis-/trans isomerase Pin1. By flipping the substrate between two different functional conformations, this enzyme exerts a fine-tuning of phosphorylation signals. Pin1 has been detected in dendritic spines and shafts where it regulates protein synthesis required to sustain the late phase of long-term potentiation (LTP). Here, we demonstrate that Pin1 residing in postsynaptic structures can interact with postsynaptic density protein-95 (PSD-95), a key scaffold protein that anchors NMDA receptors (NMDARs) in PSD via GluN2-type receptor subunits. Pin1 recruitment by PSD-95 occurs at specific serine-threonine/proline consensus motifs localized in the linker region connecting PDZ2 to PDZ3 domains. Upon binding, Pin1 triggers structural changes in PSD-95, thus negatively affecting its ability to interact with NMDARs. In electrophysiological experiments, larger NMDA-mediated synaptic currents, evoked in CA1 principal cells by Schaffer collateral stimulation, were detected in hippocampal slices obtained from Pin1(-/-) mice compared with controls. Similar results were obtained in cultured hippocampal cells expressing a PSD-95 mutant unable to undergo prolyl-isomerization, thus indicating that the action of Pin1 on PSD-95 is critical for this effect. In addition, an enhancement in spine density and size was detected in CA1 principal cells of Pin1(-/-) or in Thy-1GFP mice treated with the pharmacological inhibitor of Pin1 catalytic activity PiB.Our data indicate that Pin1 controls synaptic content of NMDARs via PSD-95 prolyl-isomerization and the expression of dendritic spines, both required for LTP maintenance. PSD-95, a membrane-associated guanylate kinase, is the major scaffolding protein at excitatory postsynaptic densities and a potent regulator of synaptic strength and plasticity. The activity of PSD-95 is tightly controlled by several post-translational mechanisms including proline-directed phosphorylation. This signaling cascade regulates the fate of its targets through postphosphorylation conformational modifications catalyzed by the peptidyl-prolyl cis-/trans isomerase Pin1. Here, we uncover a new role of Pin1 in glutamatergic signaling. By interacting with PSD-95, Pin1 dampens PSD-95 ability to complex with NMDARs, thus negatively affecting NMDAR signaling and spine morphology. Our findings further emphasize the emerging role of Pin1 as a key modulator of synaptic transmission. Copyright © 2016 the authors 0270-6474/16/365437-11$15.00/0.

Prepuberal intranasal dopamine treatment in an animal model of ADHD ameliorates deficient spatial attention, working memory, amino acid transmitters and synaptic markers in prefrontal cortex, ventral and dorsal striatum.

PubMed

Ruocco, L A; Treno, C; Gironi Carnevale, U A; Arra, C; Mattern, C; Huston, J P; de Souza Silva, M A; Nikolaus, S; Scorziello, A; Nieddu, M; Boatto, G; Illiano, P; Pagano, C; Tino, A; Sadile, A G

2014-09-01

Intranasal application of dopamine (IN-DA) has been shown to increase motor activity and to release DA in the ventral (VS) and dorsal striatum (DS) of rats. The aim of the present study was to assess the effects of IN-DA treatment on parameters of DA and excitatory amino acid (EAA) function in prepuberal rats of the Naples high-excitability (NHE) line, an animal model for attention-deficit hyperactivity disorder (ADHD) and normal random bred (NRB) controls. NHE and NRB rats were daily administered IN-DA (0.075, 0.15, 0.30 mg/kg) or vehicle for 15 days from postnatal days 28-42 and subsequently tested in the Làt maze and in the Eight-arm radial Olton maze. Soluble and membrane-trapped L-glutamate (L-Glu) and L-aspartate (L-Asp) levels as well as NMDAR1 subunit protein levels were determined after sacrifice in IN-DA- and vehicle-treated NHE and NRB rats in prefrontal cortex (PFc), DS and VS. Moreover, DA transporter (DAT) protein and tyrosine hydroxylase (TH) levels were assessed in PFc, DS, VS and mesencephalon (MES) and in ventral tegmental area (VTA) and substantia nigra, respectively. In NHE rats, IN-DA (0.30 mg/kg) decreased horizontal activity and increased nonselective attention relative to vehicle, whereas the lower dose (0.15 mg/kg) increased selective spatial attention. In NHE rats, basal levels of soluble EAAs were reduced in PFc and DS relative to NRB controls, while membrane-trapped EAAs were elevated in VS. Moreover, basal NMDAR1 subunit protein levels were increased in PFc, DS and VS relative to NRB controls. In addition, DAT protein levels were elevated in PFc and VS relative to NRB controls. IN-DA led to a number of changes of EAA, NMDAR1 subunit protein, TH and DAT protein levels in PFc, DS, VS, MES and VTA, in both NHE and NRB rats with significant differences between lines. Our findings indicate that the NHE rat model of ADHD may be characterized by (1) prefrontal and striatal DAT hyperfunction, indicative of DA hyperactivty, and (2) prefrontal and striatal NMDA receptor hyperfunction indicative of net EAA hyperactivty. IN-DA had ameliorative effects on activity level, attention, and working memory, which are likely to be associated with DA action at inhibitory D2 autoreceptors, leading to a reduction in striatal DA hyperactivity and, possibly, DA action on striatal EAA levels, resulting in a decrease of striatal EAA hyperfunction (with persistence of prefrontal EAA hyperfunction). Previous studies on IN-DA treatment in rodents have indicated antidepressant, anxiolytic and anti-parkinsonian effects in relation to enhanced central DAergic activity. Our present results strengthen the prospects of potential therapeutic applications of intranasal  DA by indicating an enhancement of selective attention and working memory in a deficit model.

Myosin IIb-dependent Regulation of Actin Dynamics Is Required for N-Methyl-D-aspartate Receptor Trafficking during Synaptic Plasticity.

PubMed

Bu, Yunfei; Wang, Ning; Wang, Shaoli; Sheng, Tao; Tian, Tian; Chen, Linlin; Pan, Weiwei; Zhu, Minsheng; Luo, Jianhong; Lu, Wei

2015-10-16

N-Methyl-d-aspartate receptor (NMDAR) synaptic incorporation changes the number of NMDARs at synapses and is thus critical to various NMDAR-dependent brain functions. To date, the molecules involved in NMDAR trafficking and the underlying mechanisms are poorly understood. Here, we report that myosin IIb is an essential molecule in NMDAR synaptic incorporation during PKC- or θ burst stimulation-induced synaptic plasticity. Moreover, we demonstrate that myosin light chain kinase (MLCK)-dependent actin reorganization contributes to NMDAR trafficking. The findings from additional mutual occlusion experiments demonstrate that PKC and MLCK share a common signaling pathway in NMDAR-mediated synaptic regulation. Because myosin IIb is the primary substrate of MLCK and can regulate actin dynamics during synaptic plasticity, we propose that the MLCK- and myosin IIb-dependent regulation of actin dynamics is required for NMDAR trafficking during synaptic plasticity. This study provides important insights into a mechanical framework for understanding NMDAR trafficking associated with synaptic plasticity. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Developmental switch in the contribution of presynaptic and postsynaptic NMDA receptors to long-term depression

PubMed Central

Corlew, Rebekah; Wang, Yun; Ghermazien, Haben; Erisir, Alev; Philpot, Benjamin D.

2010-01-01

NMDA receptor (NMDAR) activation is required for many forms of learning and memory as well as sensory system receptive field plasticity, yet the relative contribution of pre- and postsynaptic NMDARs over cortical development remains unknown. Here we demonstrate a rapid developmental loss of functional presynaptic NMDARs in the neocortex. Presynaptic NMDARs enhance neurotransmitter release at synapses onto visual cortex pyramidal cells in young mice (< postnatal day 20; P20), but they have no apparent effect after the onset of the critical period for receptive field plasticity (>P21). Immuno-electron microscopy revealed that the loss of presynaptic NMDAR function is likely due in part to a 50% reduction in the prevalence of presynaptic NMDARs. Coincident with the observed loss of presynaptic NMDAR function, there is an abrupt change in the mechanisms of timing-dependent long-term depression (tLTD). Induction of tLTD before the onset of the critical period requires activation of pre- but not postsynaptic NMDARs, while the induction of tLTD in older mice requires activation of postsynaptic NMDARs. By demonstrating that both pre- and postsynaptic NMDARs contribute to the induction of synaptic plasticity, and that their relative roles shift over development, our findings define a novel, and perhaps general, property of synaptic plasticity in emerging cortical circuits. PMID:17855598

NMDA receptor content of synapses in stratum radiatum of the hippocampal CA1 area.

PubMed

Racca, C; Stephenson, F A; Streit, P; Roberts, J D; Somogyi, P

2000-04-01

Glutamate receptors activated by NMDA (NMDARs) or AMPA (AMPARs) are clustered on dendritic spines of pyramidal cells. Both the AMPAR-mediated postsynaptic responses and the synaptic AMPAR immunoreactivity show a large intersynapse variability. Postsynaptic responses mediated by NMDARs show less variability. To assess the variability in NMDAR content and the extent of their coexistence with AMPARs in Schaffer collateral-commissural synapses of adult rat CA1 pyramidal cells, electron microscopic immunogold localization of receptors has been used. Immunoreactivity of NMDARs was detected in virtually all synapses on spines, but AMPARs were undetectable, on average, in 12% of synapses. A proportion of synapses had a very high AMPAR content relative to the mean content, resulting in a distribution more skewed toward larger values than that of NMDARs. The variability of synaptic NMDAR content [coefficient of variation (CV), 0.64-0.70] was much lower than that of the AMPAR content (CV, 1.17-1.45). Unlike the AMPAR content, the NMDAR content showed only a weak correlation with synapse size. As reported previously for AMPARs, the immunoreactivity of NMDARs was also associated with the spine apparatus within spines. The results demonstrate that the majority of the synapses made by CA3 pyramidal cells onto spines of CA1 pyramids express both NMDARs and AMPARs, but with variable ratios. A less-variable NMDAR content is accompanied by a wide variability of AMPAR content, indicating that the regulation of expression of the two receptors is not closely linked. These findings support reports that fast excitatory transmission at some of these synapses is mediated by activation mainly of NMDARs.

Memantine block depends on agonist presentation at the NMDA receptor in substantia nigra pars compacta dopamine neurones

PubMed Central

Wild, A.R.; Akyol, E.; Brothwell, S.L.C.; Kimkool, P.; Skepper, J.N.; Gibb, A.J.; Jones, S.

2015-01-01

NMDA glutamate receptors (NMDARs) have critical functional roles in the nervous system but NMDAR over-activity can contribute to neuronal damage. The open channel NMDAR blocker, memantine is used to treat certain neurodegenerative diseases, including Parkinson’s disease (PD) and is well tolerated clinically. We have investigated memantine block of NMDARs in substantia nigra pars compacta (SNc) dopamine neurones, which show severe pathology in PD. Memantine (10 μM) caused robust inhibition of whole-cell (synaptic and extrasynaptic) NMDARs activated by NMDA at a high concentration or a long duration, low concentration. Less memantine block of NMDAR-EPSCs was seen in response to low frequency synaptic stimulation, while responses to high frequency synaptic stimulation were robustly inhibited by memantine; thus memantine inhibition of NMDAR-EPSCs showed frequency-dependence. By contrast, MK-801 (10 μM) inhibition of NMDAR-EPSCs was not significantly different at low versus high frequencies of synaptic stimulation. Using immunohistochemistry, confocal imaging and stereological analysis, NMDA was found to reduce the density of cells expressing tyrosine hydroxylase, a marker of viable dopamine neurones; memantine prevented the NMDA-evoked decrease. In conclusion, memantine blocked NMDAR populations in different subcellular locations in SNc dopamine neurones but the degree of block depended on the intensity of agonist presentation at the NMDAR. This profile may contribute to the beneficial effects of memantine in PD, as glutamatergic activity is reported to increase, and memantine could preferentially reduce over-activity while leaving some physiological signalling intact. PMID:23727219

Extrasynaptic targeting of NMDA receptors following D1 dopamine receptor activation and cocaine self-administration

PubMed Central

Ortinski, Pavel I.; Turner, Jill R.; Pierce, R. Christopher

2013-01-01

We previously showed that after repeated exposure to cocaine, D1-like dopamine receptor (D1DR) stimulation reverses plastic changes of AMPA receptor-mediated signaling in the nucleus accumbens shell. However, there is little information on the impact of cocaine self-administration on D1-NMDA receptor interactions in this brain region. Here, we assessed whether cocaine self-administration alters the effects of D1DR stimulation on synaptic and extrasynaptic NMDA receptors (NMDARs) using whole-cell patch-clamp recordings. In slices from cocaine-naïve rats, pre-treatment with a D1DR agonist decreased synaptic NMDAR receptor-mediated currents and increased the contribution of extrasynaptic NMDARs. In contrast, neither cocaine self-administration alone nor cocaine experience followed by D1DR stimulation had an effect on synaptic or extrasynaptic NMDAR signaling. Activation of extrasynaptic NMDARs relies on the availability of extracellular glutamate, which is regulated primarily by glutamate transporters. In cocaine-experienced animals, administration of a glutamate re-uptake blocker, DL-threo-β-benzyloxyaspartic acid (TBOA), revealed increased extrasynaptic NMDAR activity and stronger baseline activity of glutamate uptake transporters relative to cocaine-naïve rats. In cocaine-naïve rats, the D1DR-mediated increase in extrasynaptic NMDAR signaling was independent of the activity of glutamate re-uptake transporters. Taken together, these results indicate that cocaine experience blunts the influence of D1DRs on synaptic and extrasynaptic NMDAR signaling. Additionally, prior cocaine self-administration limits activation of the extrasynaptic NMDAR pool by increasing glutamate re-uptake. These findings outline a pattern of adaptive interactions between D1DRs and NMDARs in the nucleus accumbens shell and demonstrate up-regulation of extrasynaptic NMDAR signaling as a novel consequence of cocaine self-administration. PMID:23719812

Environmental Enrichment Mitigates Deficits after Repetitive Mild Traumatic Brain Injury.

PubMed

Liu, Xixia; Qiu, Jianhua; Alcon, Sasha; Hashim, Jumana; Meehan, William P; Mannix, Rebekah

2017-08-15

Although environmental enrichment has been shown to improve functional and histologic outcomes in pre-clinical moderate-to-severe traumatic brain injury (TBI), there are a paucity of pre-clinical data regarding enrichment strategies in the setting of repetitive mild traumatic brain injury (rmTBI). Given the vast numbers of athletes and those in the military who sustain rmTBI, the mounting evidence of the long-term and progressive sequelae of rmTBI, and the lack of targeted therapies to mitigate these sequelae, successful enrichment interventions in rmTBI could have large public health significance. Here, we evaluated enrichment strategies in an established pre-clinical rmTBI model. Seventy-one male C57BL/6 mice were randomized to two different housing conditions, environmental enrichment (EE) or normal condition (NC), then subjected to rmTBI injury (seven injuries in 9 days) or sham injury (anesthesia only). Functional outcomes in all four groups (NC-TBI, EE-TBI, NC-sham, and EE-sham) were assessed by motor, exploratory/anxiety, and mnemonic behavioral tests. At the synaptic level, N-methyl d-aspartate receptor (NMDAR) subunit expression of phosphorylated glutamate receptor 1 (GluR1), phosphorylated Ca 2+ /calmodulin-dependent protein kinase II (CaMKII), and calpain were evaluated by western blot. Compared to injured NC-TBI mice, EE-TBI mice had improved memory and decreased anxiety and exploratory activity post-injury. Treatment with enrichment also corresponded to normal NMDAR subunit expression, decreased GluR1 phosphorylation, decreased phosphorylated CaMKII, and normal calpain expression post-rmTBI. These data suggest that enrichment strategies may improve functional outcomes and mitigate synaptic changes post-rmTBI. Given that enrichment strategies are feasible in the clinical setting, particularly for athletes and soldiers for whom the risk of repetitive injury is greatest, these data suggest that clinical trials may be warranted.

Differential effects of TM4 tryptophan mutations on inhibition of N-methyl-d-aspartate receptors by ethanol and toluene.

PubMed

Smothers, C Thetford; Woodward, John J

2016-11-01

The voluntary use and abuse of alcohol and inhalants is a recognized health problem throughout the world. Previous studies have shown that these agents affect brain function in a variety of ways including direct inhibition of key ion channels that regulate neuronal excitability. Among these, the N-methyl-d-aspartate (NMDA) receptor is particularly important given its key role in glutamatergic synaptic transmission, neuronal plasticity and learning and memory. Previous studies from this laboratory and others have identified key residues within transmembrane (TM) domains of the NMDA receptor that appear to regulate its sensitivity to alcohol and anesthetics. In this study, we extend these findings and examine the role of a TM4 residue in modulating sensitivity of recombinant NMDA receptors to ethanol and toluene. HEK293 cells were transfected with GluN1-1a and either wild-type or tryptophan-substituted GluN2(A-D) subunits and whole-cell currents were recorded using patch-clamp electrophysiology in the absence or presence of ethanol or toluene. Both ethanol (100 mM) and toluene (1 or 3 mM) reversibly inhibited glutamate-activated currents from wild-type NMDARs with GluN2B containing receptors showing heightened sensitivity to either agent. Substitution of tryptophan (W) at positions 825, 826, 823 or 850 in the TM4 domain of GluN2A, GluN2B, GluN2C or GluN2D subunits; respectively, significantly reduced the degree of inhibition by ethanol. In contrast, toluene inhibition of glutamate-activated currents in cells expressing the TM4-W mutants was not different from that of the wild-type controls. These data suggest that despite similarities in their action on NMDARs, ethanol and toluene may act at different sites to reduce ion flux through NMDA receptors. Copyright © 2016 Elsevier Inc. All rights reserved.

Differential Effects of TM4 Tryptophan Mutations on Inhibition of N-Methyl-D-Aspartate Receptors by Ethanol and Toluene

PubMed Central

Smothers, C. Thetford; Woodward, John J.

2017-01-01

The voluntary use and abuse of alcohol and inhalants is a recognized health problem throughout the world. Previous studies have shown that these agents affect brain function in a variety of ways including direct inhibition of key ion channels that regulate neuronal excitability. Among these, the N-methyl-D-aspartate (NMDA) receptor is particularly important given its key role in glutamatergic synaptic transmission, neuronal plasticity and learning and memory. Previous studies from this laboratory and others have identified key residues within transmembrane (TM) domains of the NMDA receptor that appear to regulate its sensitivity to alcohol and anesthetics. In this study, we extend these findings and examine the role of a TM4 residue in modulating sensitivity of recombinant NMDA receptors to ethanol and toluene. HEK293 cells were transfected with GluN1-1a and either wild-type or tryptophan-substituted GluN2(A–D) subunits and whole-cell currents were recorded using patch-clamp electrophysiology in the absence or presence of ethanol or toluene. Both ethanol (100 mM) and toluene (1 or 3 mM) reversibly inhibited glutamate-activated currents from wild-type NMDARs with GluN2B containing receptors showing heightened sensitivity to either agent. Substitution of tryptophan (W) at positions 825, 826, 823 or 850 in the TM4 domain of GluN2A, GluN2B, GluN2C or GluN2D subunits; respectively, significantly reduced the degree of inhibition by ethanol. In contrast, toluene inhibition of glutamate-activated currents in cells expressing the TM4-W mutants was not different from that of the wild-type controls. These data suggest that despite similarities in their action on NMDARs, ethanol and toluene may act at different sites to reduce ion flux through NMDA receptors. PMID:27814790

IL-1ra alleviates inflammatory hyperalgesia through preventing phosphorylation of NMDA receptor NR-1 subunit in rats.

PubMed

Zhang, Rui-Xin; Li, Aihui; Liu, Bing; Wang, Linbo; Ren, Ke; Zhang, Haiqing; Berman, Brian M; Lao, Lixing

2008-04-01

Although it has been shown that pro-inflammatory cytokines such as interleukin-1beta (IL-1beta) facilitate perception of noxious inputs at the spinal level, the mechanisms have not been understood. This study determined the cell type that produces IL-1beta, the co-localization of IL-1 receptor type I (IL-1RI) and Fos and NR1 in the spinal cord, and the effects of IL-1 receptor antagonist (IL-1ra) on NR1 phosphorylation and hyperalgesia in a rat model of inflammatory pain. Phosphorylation of NR1, an essential subunit of the NMDA receptor (NMDAR), is known to modulate NMDAR activity and facilitate pain. Hyperalgesia was induced by injecting complete Freund's adjuvant (CFA, 0.08ml, 40microg Mycobacterium tuberculosis) into one hind paw of each rat. Paw withdrawal latency (PWL) was tested before CFA (-48h) for baseline and 2 and 24h after CFA to assess hyperalgesia. IL-1ra was given (i.t.) 24h before CFA to block the action of basal IL-1beta and 2h prior to each of two PWL tests to block CFA-induced IL-1beta. Spinal cords were removed for double immunostaining of IL-1beta/neuronal marker and IL-1beta/glial cell markers, IL-1RI/Fos and IL-1RI/NR1, and for Western blot to measure NR1 phosphorylation. The data showed that: (1) astrocytes produce IL-1beta, (2) IL-1RI is localized in Fos- and NR1-immunoreactive neurons within the spinal dorsal horn, and (3) IL-1ra at 0.01mg/rat significantly increased PWL (P<0.05) and inhibited NR1 phosphorylation compared to saline control. The results suggest that spinal IL-1beta is produced by astrocytes and enhances NR1 phosphorylation to facilitate inflammatory pain.

Pannexin 1 regulates bidirectional hippocampal synaptic plasticity in adult mice.

PubMed

Ardiles, Alvaro O; Flores-Muñoz, Carolina; Toro-Ayala, Gabriela; Cárdenas, Ana M; Palacios, Adrian G; Muñoz, Pablo; Fuenzalida, Marco; Sáez, Juan C; Martínez, Agustín D

2014-01-01

The threshold for bidirectional modification of synaptic plasticity is known to be controlled by several factors, including the balance between protein phosphorylation and dephosphorylation, postsynaptic free Ca(2+) concentration and NMDA receptor (NMDAR) composition of GluN2 subunits. Pannexin 1 (Panx1), a member of the integral membrane protein family, has been shown to form non-selective channels and to regulate the induction of synaptic plasticity as well as hippocampal-dependent learning. Although Panx1 channels have been suggested to play a role in excitatory long-term potentiation (LTP), it remains unknown whether these channels also modulate long-term depression (LTD) or the balance between both types of synaptic plasticity. To study how Panx1 contributes to excitatory synaptic efficacy, we examined the age-dependent effects of eliminating or blocking Panx1 channels on excitatory synaptic plasticity within the CA1 region of the mouse hippocampus. By using different protocols to induce bidirectional synaptic plasticity, Panx1 channel blockade or lack of Panx1 were found to enhance LTP, whereas both conditions precluded the induction of LTD in adults, but not in young animals. These findings suggest that Panx1 channels restrain the sliding threshold for the induction of synaptic plasticity and underlying brain mechanisms of learning and memory.

Pannexin 1 regulates bidirectional hippocampal synaptic plasticity in adult mice

PubMed Central

Ardiles, Alvaro O.; Flores-Muñoz, Carolina; Toro-Ayala, Gabriela; Cárdenas, Ana M.; Palacios, Adrian G.; Muñoz, Pablo; Fuenzalida, Marco; Sáez, Juan C.; Martínez, Agustín D.

2014-01-01

The threshold for bidirectional modification of synaptic plasticity is known to be controlled by several factors, including the balance between protein phosphorylation and dephosphorylation, postsynaptic free Ca2+ concentration and NMDA receptor (NMDAR) composition of GluN2 subunits. Pannexin 1 (Panx1), a member of the integral membrane protein family, has been shown to form non-selective channels and to regulate the induction of synaptic plasticity as well as hippocampal-dependent learning. Although Panx1 channels have been suggested to play a role in excitatory long-term potentiation (LTP), it remains unknown whether these channels also modulate long-term depression (LTD) or the balance between both types of synaptic plasticity. To study how Panx1 contributes to excitatory synaptic efficacy, we examined the age-dependent effects of eliminating or blocking Panx1 channels on excitatory synaptic plasticity within the CA1 region of the mouse hippocampus. By using different protocols to induce bidirectional synaptic plasticity, Panx1 channel blockade or lack of Panx1 were found to enhance LTP, whereas both conditions precluded the induction of LTD in adults, but not in young animals. These findings suggest that Panx1 channels restrain the sliding threshold for the induction of synaptic plasticity and underlying brain mechanisms of learning and memory. PMID:25360084

The major brain cholesterol metabolite 24(S)-hydroxycholesterol is a potent allosteric modulator of N-methyl-D-aspartate receptors.

PubMed

Paul, Steven M; Doherty, James J; Robichaud, Albert J; Belfort, Gabriel M; Chow, Brian Y; Hammond, Rebecca S; Crawford, Devon C; Linsenbardt, Andrew J; Shu, Hong-Jin; Izumi, Yukitoshi; Mennerick, Steven J; Zorumski, Charles F

2013-10-30

N-methyl-D-aspartate receptors (NMDARs) are glutamate-gated ion channels that are critical to the regulation of excitatory synaptic function in the CNS. NMDARs govern experience-dependent synaptic plasticity and have been implicated in the pathophysiology of various neuropsychiatric disorders including the cognitive deficits of schizophrenia and certain forms of autism. Certain neurosteroids modulate NMDARs experimentally but their low potency, poor selectivity, and very low brain concentrations make them poor candidates as endogenous ligands or therapeutic agents. Here we show that the major brain-derived cholesterol metabolite 24(S)-hydroxycholesterol (24(S)-HC) is a very potent, direct, and selective positive allosteric modulator of NMDARs with a mechanism that does not overlap that of other allosteric modulators. At submicromolar concentrations 24(S)-HC potentiates NMDAR-mediated EPSCs in rat hippocampal neurons but fails to affect AMPAR or GABAA receptors (GABA(A)Rs)-mediated responses. Cholesterol itself and other naturally occurring oxysterols present in brain do not modulate NMDARs at concentrations ≤10 μM. In hippocampal slices, 24(S)-HC enhances the ability of subthreshold stimuli to induce long-term potentiation (LTP). 24(S)-HC also reverses hippocampal LTP deficits induced by the NMDAR channel blocker ketamine. Finally, we show that synthetic drug-like derivatives of 24(S)-HC, which potently enhance NMDAR-mediated EPSCs and LTP, restore behavioral and cognitive deficits in rodents treated with NMDAR channel blockers. Thus, 24(S)-HC may function as an endogenous modulator of NMDARs acting at a novel oxysterol modulatory site that also represents a target for therapeutic drug development.

Activity-dependent regulation of NMDAR1 immunoreactivity in the developing visual cortex.

PubMed

Catalano, S M; Chang, C K; Shatz, C J

1997-11-01

NMDA receptors have been implicated in activity-dependent synaptic plasticity in the developing visual cortex. We examined the distribution of immunocytochemically detectable NMDAR1 in visual cortex of cats and ferrets from late embryonic ages to adulthood. Cortical neurons are initially highly immunostained. This level declines gradually over development, with the notable exception of cortical layers 2/3, where levels of NMDAR1 immunostaining remain high into adulthood. Within layer 4, the decline in NMDAR1 immunostaining to adult levels coincides with the completion of ocular dominance column formation and the end of the critical period for layer 4. To determine whether NMDAR1 immunoreactivity is regulated by retinal activity, animals were dark-reared or retinal activity was completely blocked in one eye with tetrodotoxin (TTX). Dark-rearing does not cause detectable changes in NMDAR1 immunoreactivity. However, 2 weeks of monocular TTX administration decreases NMDAR1 immunoreactivity in layer 4 of the columns of the blocked eye. Thus, high levels of NMDAR1 immunostaining within the visual cortex are temporally correlated with ocular dominance column formation and developmental plasticity; the persistence of staining in layers 2/3 also correlates with the physiological plasticity present in these layers in the adult. In addition, visual experience is not required for the developmental changes in the laminar pattern of NMDAR1 levels, but the presence of high levels of NMDAR1 in layer 4 during the critical period does require retinal activity. These observations are consistent with a central role for NMDA receptors in promoting and ultimately limiting synaptic rearrangements in the developing neocortex.

Meta-analysis of the association between N-methyl-d-aspartate receptor antibodies and schizophrenia, schizoaffective disorder, bipolar disorder, and major depressive disorder.

PubMed

Pearlman, Daniel M; Najjar, Souhel

2014-08-01

N-methyl-d-aspartate receptor (NMDAR) antibodies have been documented in the serum of individuals with primary psychiatric disorders from several independent cohorts, but these findings have not been systematically assessed in aggregate or in relation to methodological covariates. We searched MEDLINE, EMBASE, and PsycINFO for studies in any language that provided data on NMDAR antibody seropositivity or absolute serum titers in schizophrenia or schizoaffective, bipolar, or major depressive disorders. We used a random effects model to pool estimates across studies. Nine studies met the eligibility criteria. Five studies (3387 participants) provided data on NMDAR antibody seropositivity in psychiatric versus control groups based on high-specificity seropositivity thresholds (cell-based assays [CBAs]: 1:320 dilution, 1:200 dilution, visual score>1; enzyme-linked immunosorbent assay [ELISA]: 90(th) percentile of control titers). Meta-analysis showed significantly higher odds of NMDAR antibody seropositivity among those with schizophrenia or schizoaffective, bipolar, or major depressive disorders compared with healthy controls (odds ratio [OR], 3.10; 95% confidence interval [CI], 1.04-9.27; P=.043; I(2)=68%). Four studies (3194 participants) provided outcome data for these groups based on low-specificity seropositivity thresholds (CBAs 1:10 dilution; ELISA: 75(th) percentile of control titers). Meta-analysis showed greater heterogeneity and no significant between-group difference (OR, 2.31; 95% CI, 0.55-9.73; P=.25; I(2)=90%). Seropositive participants in psychiatric groups had various combinations of IgG, IgM, and IgA class antibodies against NR1, NR1/NR2B, and NR2A/NR2B subunits. Subgroup analysis revealed significantly higher odds of seropositivity among all participants based on 1:10 versus 1:320 dilution seropositivity thresholds (OR, 4.56; 95% CI, 2.41-8.62; P<.001; I(2)=0%; studies=2, n=2920), but no apparent difference between first-episode and chronic schizophrenia or schizoaffective disorder (OR, 1.15; 95% CI, 0.19-7.24; P=.88, I(2)=43%, studies=2, n=1108). Average NR2A/NR2B antibody titers determined by ELISA were significantly higher among participants with first-episode schizophrenia (P<.0001) and acute mania (P<.01) compared with healthy controls. Levels decreased by 58% at 8weeks in first-episode schizophrenia, and by about 13% at 4days in acute mania. Individuals with schizophrenia or schizoaffective, bipolar, or major depressive disorders are collectively about three times more likely to have elevated NMDAR antibody titers compared with healthy controls based on high-specificity, but not low-specificity, seropositivity thresholds, though considerable methodological and statistical heterogeneity exists. Evidence concerning the effect of disease state and time of serum acquisition is varied and consistent, respectively. Adequately powered longitudinal studies employing standardized assay methods and seropositivity threshold definitions, and quantifying NMDAR antibodies in both sera and cerebrospinal fluid are needed to further elucidate the clinical and pathophysiological implications of this association. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

The Subiculum: A Potential Site of Ictogenesis in a Neonatal Seizure Model

PubMed Central

Wang, Xin-Xin; Li, Yong-Hua; Gong, Hai-Qing; Liang, Pei-Ji; Zhang, Pu-Ming; Lu, Qin-Chi

2017-01-01

Studies have reported that the subiculum is one origin of interictal-like discharges in adult patients with temporal lobe epilepsy; however, whether the subiculum represents a site of ictogenesis for neonatal seizures remains unclear. In this study, multi-electrode recording techniques were used to record epileptiform discharges induced by low-Mg2+ or high-K+ artificial cerebrospinal fluid in neonatal mouse hippocampal slices, and the spatiotemporal dynamics of the epileptiform discharges were analyzed. The Na+–K+–2Cl− cotransporter 1 (NKCC1) blocker, bumetanide, was applied to test its effect upon epileptiform discharges in low-Mg2+ model. The effect of N-methyl-d-aspartate receptors (NMDARs) antagonist, d-AP5, upon the epileptiform discharges in high-K+ model was examined. We found that the neonatal subiculum not only relayed epileptiform discharges emanating from the hippocampus proper (HP) but also initiated epileptiform discharges (interictal- and ictal-like discharges) independently. The latency to onset of the first epileptiform discharge initiated in the subiculum was similar to that initiated in the HP. Bumetanide efficiently blocked seizures in the neonatal HP, but was less effectively in suppressing seizures initiated in the subiculum. In high-K+ model, d-AP5 was more effective in blocking seizures initiated in the subiculum than that initiated in the HP. Furthermore, Western blotting analysis showed that NKCC1 expression was lower in the subiculum than that in the HP, whereas the expression of NMDAR subunits, NR2A and NR2B, was higher in the subiculum than that in the HP. Our results revealed that the subiculum was a potential site of ictogenesis in neonatal seizures and possessed similar seizure susceptibility to the HP. GABAergic excitation resulting from NKCC1 may play a less dominant role during ictogenesis in the subiculum than that in the HP. The subicular ictogenesis may be related to the glutamatergic excitation mediated by NMDARs. PMID:28473802

NGL-2 Deletion Leads to Autistic-like Behaviors Responsive to NMDAR Modulation.

PubMed

Um, Seung Min; Ha, Seungmin; Lee, Hyejin; Kim, Jihye; Kim, Kyungdeok; Shin, Wangyong; Cho, Yi Sul; Roh, Junyeop Daniel; Kang, Jaeseung; Yoo, Taesun; Noh, Young Woo; Choi, Yeonsoo; Bae, Yong Chul; Kim, Eunjoon

2018-06-26

Netrin-G ligand 2 (NGL-2)/LRRC4, implicated in autism spectrum disorders and schizophrenia, is a leucine-rich repeat-containing postsynaptic adhesion molecule that interacts intracellularly with the excitatory postsynaptic scaffolding protein PSD-95 and trans-synaptically with the presynaptic adhesion molecule netrin-G2. Functionally, NGL-2 regulates excitatory synapse development and synaptic transmission. However, whether it regulates synaptic plasticity and disease-related specific behaviors is not known. Here, we report that mice lacking NGL-2 (Lrrc4 -/- mice) show suppressed N-Methyl-D-aspartate receptor (NMDAR)-dependent synaptic plasticity in the hippocampus. NGL-2 associates with NMDARs through both PSD-95-dependent and -independent mechanisms. Moreover, Lrrc4 -/- mice display mild social interaction deficits and repetitive behaviors that are rapidly improved by pharmacological NMDAR activation. These results suggest that NGL-2 promotes synaptic stabilization of NMDARs, regulates NMDAR-dependent synaptic plasticity, and prevents autistic-like behaviors from developing in mice, supporting the hypothesis that NMDAR dysfunction contributes to autism spectrum disorders. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Enhanced Dopamine-Dependent Hippocampal Plasticity after Single MK-801 Application

PubMed Central

Bartsch, Julia C; Fidzinski, Pawel; Huck, Jojanneke HJ; Hörtnagl, Heide; Kovács, Richard; Liotta, Agustin; Priller, Josef; Wozny, Christian; Behr, Joachim

2015-01-01

Dopaminergic hyperfunction and N-methyl-D-aspartate receptor (NMDAR) hypofunction have both been implicated in psychosis. Dopamine-releasing drugs and NMDAR antagonists replicate symptoms associated with psychosis in healthy humans and exacerbate symptoms in patients with schizophrenia. Though hippocampal dysfunction contributes to psychosis, the impact of NMDAR hypofunction on hippocampal plasticity remains poorly understood. Here, we used an NMDAR antagonist rodent model of psychosis to investigate hippocampal long-term potentiation (LTP). We found that single systemic NMDAR antagonism results in a region-specific, presynaptic LTP at hippocampal CA1-subiculum synapses that is induced by activation of D1/D5 dopamine receptors and modulated by L-type voltage-gated Ca2+ channels. Thereby, our findings may provide a cellular mechanism how NMDAR antagonism can lead to an enhanced hippocampal output causing activation of the hippocampus-ventral tegmental area-loop and overdrive of the dopamine system. PMID:25315194

Cholesterol modulates open probability and desensitization of NMDA receptors

PubMed Central

Korinek, Miloslav; Vyklicky, Vojtech; Borovska, Jirina; Lichnerova, Katarina; Kaniakova, Martina; Krausova, Barbora; Krusek, Jan; Balik, Ales; Smejkalova, Tereza; Horak, Martin; Vyklicky, Ladislav

2015-01-01

NMDA receptors (NMDARs) are glutamate-gated ion channels that mediate excitatory neurotransmission in the CNS. Although these receptors are in direct contact with plasma membrane, lipid–NMDAR interactions are little understood. In the present study, we aimed at characterizing the effect of cholesterol on the ionotropic glutamate receptors. Whole-cell current responses induced by fast application of NMDA in cultured rat cerebellar granule cells (CGCs) were almost abolished (reduced to 3%) and the relative degree of receptor desensitization was increased (by seven-fold) after acute cholesterol depletion by methyl-β-cyclodextrin. Both of these effects were fully reversible by cholesterol repletion. By contrast, the responses mediated by AMPA/kainate receptors were not affected by cholesterol depletion. Similar results were obtained in CGCs after chronic inhibition of cholesterol biosynthesis by simvastatin and acute enzymatic cholesterol degradation to 4-cholesten-3-one by cholesterol oxidase. Fluorescence anisotropy measurements showed that membrane fluidity increased after methyl-β-cyclodextrin pretreatment. However, no change in fluidity was observed after cholesterol enzymatic degradation, suggesting that the effect of cholesterol on NMDARs is not mediated by changes in membrane fluidity. Our data show that diminution of NMDAR responses by cholesterol depletion is the result of a reduction of the open probability, whereas the increase in receptor desensitization is the result of an increase in the rate constant of entry into the desensitized state. Surface NMDAR population, agonist affinity, single-channel conductance and open time were not altered in cholesterol-depleted CGCs. The results of our experiments show that cholesterol is a strong endogenous modulator of NMDARs. Key points NMDA receptors (NMDARs) are tetrameric cation channels permeable to calcium; they mediate excitatory synaptic transmission in the CNS and their excessive activation can lead to neurodegeneration. Although these receptors are in direct contact with plasma membrane, lipid–NMDAR interactions are little understood. Using cultured rat cerebellar granule cells, we show that acute and chronic pretreatments resulting in cell cholesterol depletion profoundly diminish NMDAR responses and increase NMDAR desensitization, and also that cholesterol enrichment potentiates NMDAR responses; however, cholesterol manipulation has no effect on the amplitude of AMPA/kainate receptor responses. Diminution of NMDAR responses by cholesterol depletion is the result of a reduction of the ion channel open probability, whereas the increase in receptor desensitization is the result of an increase in the rate constant of entry into the desensitized state. These results demonstrate the physiological role of membrane lipids in the modulation of NMDAR activity. PMID:25651798

Recent Progress in Understanding Subtype Specific Regulation of NMDA Receptors by G Protein Coupled Receptors (GPCRs)

PubMed Central

Yang, Kai; Jackson, Michael F.; MacDonald, John F.

2014-01-01

G Protein Coupled Receptors (GPCRs) are the largest family of receptors whose ligands constitute nearly a third of prescription drugs in the market. They are widely involved in diverse physiological functions including learning and memory. NMDA receptors (NMDARs), which belong to the ionotropic glutamate receptor family, are likewise ubiquitously expressed in the central nervous system (CNS) and play a pivotal role in learning and memory. Despite its critical contribution to physiological and pathophysiological processes, few pharmacological interventions aimed directly at regulating NMDAR function have been developed to date. However, it is well established that NMDAR function is precisely regulated by cellular signalling cascades recruited downstream of G protein coupled receptor (GPCR) stimulation. Accordingly, the downstream regulation of NMDARs likely represents an important determinant of outcome following treatment with neuropsychiatric agents that target selected GPCRs. Importantly, the functional consequence of such regulation on NMDAR function varies, based not only on the identity of the GPCR, but also on the cell type in which relevant receptors are expressed. Indeed, the mechanisms responsible for regulating NMDARs by GPCRs involve numerous intracellular signalling molecules and regulatory proteins that vary from one cell type to another. In the present article, we highlight recent findings from studies that have uncovered novel mechanisms by which selected GPCRs regulate NMDAR function and consequently NMDAR-dependent plasticity. PMID:24562329

Herpes simplex virus-induced anti-N-methyl-d-aspartate receptor encephalitis: a systematic literature review with analysis of 43 cases.

PubMed

Nosadini, Margherita; Mohammad, Shekeeb S; Corazza, Francesco; Ruga, Ezia Maria; Kothur, Kavitha; Perilongo, Giorgio; Frigo, Anna Chiara; Toldo, Irene; Dale, Russell C; Sartori, Stefano

2017-08-01

To conduct a systematic literature review on patients with biphasic disease with herpes simplex virus (HSV) encephalitis followed by anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. We conducted a case report and systematic literature review (up to 10 December 2016), focused on differences between herpes simplex encephalitis (HSE) and anti-NMDAR encephalitis phases, age-related characteristics of HSV-induced anti-NMDAR encephalitis, and therapy. For statistical analyses, McNemar's test, Fisher's test, and Wilcoxon rank sum test were used (two-tailed significance level set at 5%). Forty-three patients with biphasic disease were identified (31 children). Latency between HSE and anti-NMDAR encephalitis was significantly shorter in children than adults (median 24 vs 40.5d; p=0.006). Compared with HSE, anti-NMDAR encephalitis was characterized by significantly higher frequency of movement disorder (2.5% vs 75% respectively; p<0.001), and significantly lower rate of seizures (70% vs 30% respectively; p=0.001). Compared with adults, during anti-NMDAR encephalitis children had significantly more movement disorders (86.7% children vs 40% adults; p=0.006), fewer psychiatric symptoms (41.9% children vs 90.0% adults; p=0.025), and a slightly higher median modified Rankin Scale score (5 in children vs 4 in adults; p=0.015). During anti-NMDAR encephalitis, 84.6 per cent of patients received aciclovir (for ≤7d in 22.7%; long-term antivirals in 18.0% only), and 92.7 per cent immune therapy, but none had recurrence of HSE clinically or using cerebrospinal fluid HSV polymerase chain reaction (median follow-up 7mo). Our review suggests that movement disorder may help differentiate clinically an episode of HSV-induced anti-NMDAR encephalitis from HSE relapse. Compared with adults, children have shorter latency between HSE and anti-NMDAR encephalitis and, during anti-NMDAR encephalitis, more movement disorder, fewer psychiatric symptoms, and slightly more severe disease. According to our results, immune therapy given for HSV-induced anti-NMDAR encephalitis does not predispose patients to HSE recurrence. © 2017 Mac Keith Press.

Oscillatory Synchronous Inhibition in the Basolateral Amygdala and its Primary Dependence on NR2A-containing NMDA Receptors.

PubMed

Aroniadou-Anderjaska, Vassiliki; Pidoplichko, Volodymyr I; Figueiredo, Taiza H; Braga, Maria F M

2018-03-01

Synchronous, rhythmic firing of GABAergic interneurons is a fundamental mechanism underlying the generation of brain oscillations, and evidence suggests that NMDA receptors (NMDARs) play a key role in oscillatory activity by regulating the activity of interneurons. Consistent with this, derangement of brain rhythms in certain neuropsychiatric disorders, notably schizophrenia and autism, is associated with NMDAR hypofunction and loss of inhibitory interneurons. In the basolateral amygdala (BLA)-dysfunction of which is involved in a host of neuropsychiatric diseases-, principal neurons display spontaneous, rhythmic "bursts" of inhibitory activity, which could potentially be involved in the orchestration of oscillations in the BLA network; here, we investigated the role of NMDARs in these inhibitory oscillations. Rhythmic bursts of spontaneous IPSCs (0.5 Hz average burst frequency) recorded from rat BLA principal cells were blocked or significantly suppressed by D-AP5, and could be driven by NMDAR activation alone. BLA interneurons generated spontaneous bursts of suprathreshold EPSCs at a similar frequency, which were also blocked or reduced by D-AP5. PEAQX (GluN2A-NMDAR antagonist; 0.4 μM) or Ro-25-6981 (GluN2B-NMDAR antagonist; 5 μM) suppressed the IPSC and EPSC bursts; suppression by PEAQX was significantly greater than that by Ro-25-6981. Immunohistochemical labeling revealed the presence of both GluN2A- and GluN2B-NMDARs on GABAergic BLA interneurons, while, functionally, GluN2A-NMDARs have the dominant role, as suggested by a greater reduction of NMDA-evoked currents by PEAQX versus Ro-25-6981. Entrainment of BLA principal neurons in an oscillatory generation of inhibitory activity depends primarily on activation of GluN2A-NMDARs, and interneuronal GluN2A-NMDARs may play a significant role. Published by Elsevier Ltd.

[Chymotripsin-like activity and subunit composition of proteasomes in human cancers].

PubMed

Kondakova, I V; Spirina, L V; Koval, V D; Shashova, E E; Choinzonov, E L; Ivanova, E V; Kolomiets, L A; Chernyshova, A L; Slonimskaya, E M; Usynin, E A; Afanasyev, S G

2014-01-01

Activity of the proteasome, polyfunctional enzymatic complex, is known to undergo changes during cancer development. This phenomenon is, probably, caused by the changes in subunit composition of proteasomes. In present work, we studied chymotrypsin-like activity of proteasomes, subunit composition and their association in breast cancer, head and neck squamous cell carcinoma, endometrial cancer, renal cancer, bladder cancer, stomach cancer and colorectal cancer. The increase of proteasome activity was revealed in most cancer tissues compared with adjacent tissues except for the renal cell carcinoma. Changes in proteasome activity in cancer tissues compared with correspondent normal tissues were accompanied by modification of its subunit composition. High proteasome activity was observed in combination with an increased expression of immune subunits and/or proteasome activator PA28, associated with activity of 20S proteasome. In breast cancer, head and neck squamous cell carcinoma, bladder cancer, stomach cancer and colorectal cancer we additionally found higher expression of Rpt6 subunit of 26S proteasome. Correlations between chymotrypsin like proteasome activity and subunit expressions were found in human cancer tissues. In summary, we suggest that proteasome ac- tivation and changes in its subunit composition plays an important role in cancer pathogenesis.

D-Serine and D-Cycloserine Reduce Compulsive Alcohol Intake in Rats

PubMed Central

Seif, Taban; Simms, Jeffrey A; Lei, Kelly; Wegner, Scott; Bonci, Antonello; Messing, Robert O; Hopf, F Woodward

2015-01-01

There is considerable interest in NMDAR modulators to enhance memory and treat neuropsychiatric disorders such as addiction, depression, and schizophrenia. D-serine and D-cycloserine, the NMDAR activators at the glycine site, are of particular interest because they have been used in humans without serious adverse effects. Interestingly, D-serine also inhibits some NMDARs active at hyperpolarized potentials (HA-NMDARs), and we previously found that HA-NMDARs within the nucleus accumbens core (NAcore) are critical for promoting compulsion-like alcohol drinking, where rats consume alcohol despite pairing with an aversive stimulus such as quinine, a paradigm considered to model compulsive aspects of human alcohol use disorders (AUDs). Here, we examined the impact of D-serine and D-cycloserine on this aversion-resistant alcohol intake (that persists despite adulteration with quinine) and consumption of quinine-free alcohol. Systemic D-serine reduced aversion-resistant alcohol drinking, without altering consumption of quinine-free alcohol or saccharin with or without quinine. Importantly, D-serine within the NAcore but not the dorsolateral striatum also selectively reduced aversion-resistant alcohol drinking. In addition, D-serine inhibited EPSCs evoked at −70 mV in vitro by optogenetic stimulation of mPFC–NAcore terminals in alcohol-drinking rats, similar to reported effects of the NMDAR blocker AP5. Further, D-serine preexposure occluded AP5 inhibition of mPFC-evoked EPSCs, suggesting that D-serine reduced EPSCs by inhibiting HA-NMDARs. Systemic D-cycloserine also selectively reduced intake of quinine-adulterated alcohol, and D-cycloserine inhibited NAcore HA-NMDARs in vitro. Our results indicate that HA-NMDAR modulators can reduce aversion-resistant alcohol drinking, and support testing of D-serine and D-cycloserine as immediately accessible, FDA-approved drugs to treat AUDs. PMID:25801502

A Sustained Activation of Pancreatic NMDARs Is a Novel Factor of β-Cell Apoptosis and Dysfunction.

PubMed

Huang, Xiao-Ting; Yue, Shao-Jie; Li, Chen; Huang, Yan-Hong; Cheng, Qing-Mei; Li, Xiao-Hong; Hao, Cai-Xia; Wang, Ling-Zhi; Xu, Jian-Ping; Ji, Ming; Chen, Chen; Feng, Dan-Dan; Luo, Zi-Qiang

2017-11-01

Type 2 diabetes, which features β-cell failure, is caused by the decrease of β-cell mass and insulin secretory function. Current treatments fail to halt the decrease of functional β-cell mass. Strategies to prevent β-cell apoptosis and dysfunction are highly desirable. Recently, our group and others have reported that blockade of N-methyl-d-aspartate receptors (NMDARs) in the islets has been proposed to prevent the progress of type 2 diabetes through improving β-cell function. It suggests that a sustained activation of the NMDARs may exhibit deleterious effect on β-cells. However, the exact functional impact and mechanism of the sustained NMDAR stimulation on islet β-cells remains unclear. Here, we identify a sustained activation of pancreatic NMDARs as a novel factor of apoptotic β-cell death and function. The sustained treatment with NMDA results in an increase of intracellular [Ca2+] and reactive oxygen species, subsequently induces mitochondrial membrane potential depolarization and a decrease of oxidative phosphorylation expression, and then impairs the mitochondrial function of β-cells. NMDA specifically induces the mitochondrial-dependent pathway of apoptosis in β-cells through upregulation of the proapoptotic Bim and Bax, and downregulation of antiapoptotic Bcl-2. Furthermore, a sustained stimulation of NMDARs impairs β-cell insulin secretion through decrease of pancreatic duodenal homeobox-1 (Pdx-1) and adenosine triphosphate synthesis. The activation of nuclear factor-κB partly contributes to the reduction of Pdx-1 expression induced by overstimulation of NMDARs. In conclusion, we show that the sustained stimulation of NMDARs is a novel mediator of apoptotic signaling and β-cell dysfunction, providing a mechanistic insight into the pathological role of NMDARs activation in diabetes. Copyright © 2017 Endocrine Society.

A NMDA receptor glycine site partial agonist, GLYX-13, simultaneously enhances LTP and reduces LTD at Schaffer collateral-CA1 synapses in hippocampus.

PubMed

Zhang, Xiao-lei; Sullivan, John A; Moskal, Joseph R; Stanton, Patric K

2008-12-01

N-methyl-D-aspartate glutamate receptors (NMDARs) are a key route for Ca2+ influx into neurons important to both activity-dependent synaptic plasticity and, when uncontrolled, triggering events that cause neuronal degeneration and death. Among regulatory binding sites on the NMDAR complex is a glycine binding site, distinct from the glutamate binding site, which must be co-activated for NMDAR channel opening. We developed a novel glycine site partial agonist, GLYX-13, which is both nootropic and neuroprotective in vivo. Here, we assessed the effects of GLYX-13 on long-term synaptic plasticity and NMDAR transmission at Schaffer collateral-CA1 synapses in hippocampal slices in vitro. GLYX-13 simultaneously enhanced the magnitude of long-term potentiation (LTP) of synaptic transmission, while reducing long-term depression (LTD). GLYX-13 reduced NMDA receptor-mediated synaptic currents in CA1 pyramidal neurons evoked by low frequency Schaffer collateral stimulation, but enhanced NMDAR currents during high frequency bursts of activity, and these actions were occluded by a saturating concentration of the glycine site agonist d-serine. Direct two-photon imaging of Schaffer collateral burst-evoked increases in [Ca2+] in individual dendritic spines revealed that GLYX-13 selectively enhanced burst-induced NMDAR-dependent spine Ca2+ influx. Examining the rate of MK-801 block of synaptic versus extrasynaptic NMDAR-gated channels revealed that GLYX-13 selectively enhanced activation of burst-driven extrasynaptic NMDARs, with an action that was blocked by the NR2B-selective NMDAR antagonist ifenprodil. Our data suggest that GLYX-13 may have unique therapeutic potential as a learning and memory enhancer because of its ability to simultaneously enhance LTP and suppress LTD.

The effects of an intraperitoneal single low dose of ketamine in attenuating the postoperative skin/muscle incision and retraction-induced pain related to the inhibition of N-methyl-D-aspartate receptors in the spinal cord.

PubMed

Shen, Yu; Xu, Li; Liu, Ming; Lei, Yishan; Gu, Xiaoping; Ma, Zhengliang

2016-03-11

Chronic postoperative pain (CPOP) is a common clinical problem which might be related to central sensitization. It has been widely accepted that NMDA (N-methyl-D-aspartate) receptors are among the triggers of central sensitization. Ketamine is a non-competitive NMDA receptor antagonist that is widely used in alleviating postoperative pain, but its effect on CPOP has been rarely reported. In the present study, the skin/muscle incision and retraction (SMIR) model was used to investigate the role of NMDARs in chronic postoperative pain and the effect of an intraperitoneal single low dose ketamine (10mg/kg) of attenuating SMIR-induced CPOP. We assessed pain behaviours after a SMIR operation by paw withdrawal threshold (PWMT) and paw withdrawal latency (PWMTL). Western blotting were performed to examine the role of NMDARs in SMIR-induced CPOP and the effect of ketamine on the expression and phosphorylation of NMDARs. The SMIR operation induced long-lasting mechanical hyperalgesia, and the up-regulation of phosphorylated NMDARs and total NMDARs at the spinal level. A single intraperitoneal administration of low dose ketamine (10mg/kg) during surgery alleviated pain behaviors and inhibited the up-regulation of phosphorylated NMDARs and total NMDARs. Our datas suggested that NMDARs play important roles in SMIR-induced CPOP. A single intraperitoneal low dose of ketamine could attenuate SMIR-induced CPOP, which might be associated with the inhibition of NMDARs. Our finding might provide a new, simple method of addressing CPOP. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

NR2A- and NR2B-NMDA receptors and drebrin within postsynaptic spines of the hippocampus correlate with hunger-evoked exercise.

PubMed

Chen, Yi-Wen; Actor-Engel, Hannah; Sherpa, Ang Doma; Klingensmith, Lauren; Chowdhury, Tara G; Aoki, Chiye

2017-07-01

Hunger evokes foraging. This innate response can be quantified as voluntary wheel running following food restriction (FR). Paradoxically, imposing severe FR evokes voluntary FR, as some animals choose to run rather than eat, even during limited periods of food availability. This phenomenon, called activity-based anorexia (ABA), has been used to identify brain changes associated with FR and excessive exercise (EX), two core symptoms of anorexia nervosa (AN), and to explore neurobiological bases of AN vulnerability. Previously, we showed a strong positive correlation between suppression of FR-evoked hyperactivity, i.e., ABA resilience, and levels of extra-synaptic GABA receptors in stratum radiatum (SR) of hippocampal CA1. Here, we tested for the converse: whether animals with enhanced expression of NMDA receptors (NMDARs) exhibit greater levels of FR-evoked hyperactivity, i.e., ABA vulnerability. Four groups of animals were assessed for NMDAR levels at CA1 spines: (1) ABA, in which 4 days of FR was combined with wheel access to allow voluntary EX; (2) FR only; (3) EX only; and (4) control (CON) that experienced neither EX nor FR. Electron microscopy revealed that synaptic NR2A-NMDARs and NR2B-NMDARs levels are significantly elevated, relative to CONs'. Individuals' ABA severity, based on weight loss, correlated with synaptic NR2B-NMDAR levels. ABA resilience, quantified as suppression of hyperactivity, correlated strongly with reserve pools of NR2A-NMDARs in spine cytoplasm. NR2A- and NR2B-NMDAR measurements correlated with spinous prevalence of an F-actin binding protein, drebrin, suggesting that drebrin enables insertion of NR2B-NMDAR to and retention of NR2A-NMDARs away from synaptic membranes, together influencing ABA vulnerability.

Ephrin-B2 prevents N-methyl-D-aspartate receptor antibody effects on memory and neuroplasticity.

PubMed

Planagumà, Jesús; Haselmann, Holger; Mannara, Francesco; Petit-Pedrol, Mar; Grünewald, Benedikt; Aguilar, Esther; Röpke, Luise; Martín-García, Elena; Titulaer, Maarten J; Jercog, Pablo; Graus, Francesc; Maldonado, Rafael; Geis, Christian; Dalmau, Josep

2016-09-01

To demonstrate that ephrin-B2 (the ligand of EphB2 receptor) antagonizes the pathogenic effects of patients' N-methyl-D-aspartate receptor (NMDAR) antibodies on memory and synaptic plasticity. One hundred twenty-two C57BL/6J mice infused with cerebrospinal fluid (CSF) from patients with anti-NMDAR encephalitis or controls, with or without ephrin-B2, were investigated. CSF was infused through ventricular catheters connected to subcutaneous osmotic pumps over 14 days. Memory, behavioral tasks, locomotor activity, presence of human antibodies specifically bound to hippocampal NMDAR, and antibody effects on the density of cell-surface and synaptic NMDAR and EphB2 were examined at different time points using reported techniques. Short- and long-term synaptic plasticity were determined in acute brain sections; the Schaffer collateral pathway was stimulated and the field excitatory postsynaptic potentials were recorded in the CA1 region of the hippocampus. Mice infused with patients' CSF, but not control CSF, developed progressive memory deficit and depressive-like behavior along with deposits of NMDAR antibodies in the hippocampus. These findings were associated with a decrease of the density of cell-surface and synaptic NMDAR and EphB2, and marked impairment of long-term synaptic plasticity without altering short-term plasticity. Administration of ephrin-B2 prevented the pathogenic effects of the antibodies in all the investigated paradigms assessing memory, depressive-like behavior, density of cell-surface and synaptic NMDAR and EphB2, and long-term synaptic plasticity. Administration of ephrin-B2 prevents the pathogenic effects of anti-NMDAR encephalitis antibodies on memory and behavior, levels of cell-surface NMDAR, and synaptic plasticity. These findings reveal a strategy beyond immunotherapy to antagonize patients' antibody effects. Ann Neurol 2016;80:388-400. © 2016 American Neurological Association.

Cortical synaptic NMDA receptor deficits in α7 nicotinic acetylcholine receptor gene deletion models: Implications for neuropsychiatric diseases

PubMed Central

Lin, Hong; Hsu, Fu-Chun; Baumann, Bailey H.; Coulter, Douglas A.; Lynch, David R.

2014-01-01

Microdeletion of the human CHRNA7 gene (α7 nicotinic acetylcholine receptor, nAChR) as well as dysfunction in N-methyl-D-aspartate receptors (NMDARs) have been associated with cortical dysfunction in a broad spectrum of neurodevelopmental and neuropsychiatric disorders including schizophrenia. However, the pathophysiological roles of synaptic vs. extrasynaptic NMDARs and their interactions with α7 nAChRs in cortical dysfunction remain largely uncharacterized. Using a combination of in vivo and in vitro models, we demonstrate that α7 nAChR gene deletion leads to specific loss of synaptic NMDARs and their coagonist, D-serine, as well as glutamatergic synaptic deficits in mouse cortex. α7 nAChR null mice had decreased cortical NMDAR expression and glutamatergic synapse formation during postnatal development. Similar reductions in NMDAR expression and glutamatergic synapse formation were revealed in cortical cultures lacking α7 nAChRs. Interestingly, synaptic, but not extrasynaptic, NMDAR currents were specifically diminished in cultured cortical pyramidal neurons as well as in acute prefrontal cortical slices of α7 nAChR null mice. Moreover, D-serine responsive synaptic NMDAR-mediated currents and levels of the D-serine synthetic enzyme serine racemase were both reduced in α7 nAChR null cortical pyramidal neurons. Our findings thus identify specific loss of synaptic NMDARs and their coagonist, D-serine, as well as glutamatergic synaptic deficits in α7 nAChR gene deletion models of cortical dysfunction, thereby implicating α7 nAChR-mediated control of synaptic NMDARs and serine racemase/D-serine pathways in cortical dysfunction underlying many neuropsychiatric and neurodevelopmental disorders, particularly those associated with deletion of human CHRNA7. PMID:24326163

High sensitivity and specificity in proposed clinical diagnostic criteria for anti-N-methyl-D-aspartate receptor encephalitis.

PubMed

Ho, Alvin C C; Mohammad, Shekeeb S; Pillai, Sekhar C; Tantsis, Esther; Jones, Hannah; Ho, Reena; Lim, Ming; Hacohen, Yael; Vincent, Angela; Dale, Russell C

2017-12-01

To determine the validity of the proposed clinical diagnostic criteria for anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis in paediatric patients. The diagnostic criteria for anti-NMDAR encephalitis proposed by Graus et al. (2016) use clinical features and conventional investigations to facilitate early immunotherapy before antibody status is available. The criteria are satisfied if patients develop four out of six symptom groups within 3 months, together with at least one abnormal investigation (electroencephalography/cerebrospinal fluid) and reasonable exclusion of other disorders. We evaluated the validity of the criteria using a retrospective cohort of paediatric patients with encephalitis. Twenty-nine patients with anti-NMDAR encephalitis and 74 comparison children with encephalitis were included. As expected, the percentage of patients with anti-NMDAR encephalitis who fulfilled the clinical criteria increased over time. During the hospital inpatient admission, most patients (26/29, 90%) with anti-NMDAR encephalitis fulfilled the criteria, significantly more than the comparison group (3/74, 4%) (p<0.001). The median time of fulfilling the criteria in patients with anti-NMDAR encephalitis was 2 weeks from first symptom onset (range 1-6). The sensitivity of the criteria was 90% (95% confidence interval 73-98) and the specificity was 96% (95% confidence interval 89-99). The proposed diagnostic criteria for anti-NMDAR encephalitis have good sensitivity and specificity. Incomplete criteria do not exclude the diagnosis. The proposed clinical diagnostic criteria for anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis by Graus et al. (2016) have high sensitivity and specificity in paediatric patients. The median time of fulfilling the criteria in patients with anti-NMDAR was 2 weeks from first symptom onset. © 2017 Mac Keith Press.

Effects of Mg2+ on recovery of NMDA receptors from inhibition by memantine and ketamine reveal properties of a second site.

PubMed

Glasgow, Nathan G; Wilcox, Madeleine R; Johnson, Jon W

2018-05-12

Memantine and ketamine are NMDA receptor (NMDAR) open channel blockers that are thought to act via similar mechanisms at NMDARs, but exhibit divergent clinical effects. Both drugs act by entering open NMDARs and binding at a site deep within the ion channel (the deep site) at which the endogenous NMDAR channel blocker Mg 2+ also binds. Under physiological conditions, Mg 2+ increases the IC 50 s of memantine and ketamine through competition for binding at the deep site. Memantine also can inhibit NMDARs after associating with a second site accessible in the absence of agonist, a process termed second site inhibition (SSI) that is not observed with ketamine. Here we investigated the effects of 1 mM Mg 2+ on recovery from inhibition by memantine and ketamine, and on memantine SSI, of the four main diheteromeric NMDAR subtypes. We found that: recovery from memantine inhibition depended strongly on the concentration of memantine used to inhibit the NMDAR response; Mg 2+ accelerated recovery from memantine and ketamine inhibition through distinct mechanisms and in an NMDAR subtype-dependent manner; and Mg 2+ occupation of the deep site disrupted memantine SSI in a subtype-dependent manner. Our results support the hypothesis that memantine associates with, but does not inhibit at the second site. After associating with the second site, memantine can either slowly dissociate directly to the extracellular solution, or transit to the deep site, resulting in typical channel block. Memantine's relatively slow dissociation from the second site underlies the dependence of NMDAR recovery from inhibition on both memantine concentration and on Mg 2+ . Copyright © 2018 Elsevier Ltd. All rights reserved.

Immunocytochemical localization of the NMDA-R2A receptor subunit in the cat retina.

PubMed

Goebel, D J; Aurelia, J L; Tai, Q; Jojich, L; Poosch, M S

1998-10-19

Immunocytochemical studies were performed to determine the distribution and cellular localization of the NMDA-R2A receptor subunit (R2A) in the cat retina. R2A-immunoreactivity (R2A-IR) was noted in all layers of the retina, with specific localizations in the outer segments of red/green and blue cone photoreceptors, B-type horizontal cells, several types of amacrine cells, Müller cells and the majority of cells in the ganglion cell layer. In the inner nuclear layer, 48% of all cells residing in the amacrine cell layer were R2A-IR including a cell resembling the GABAergic A17 amacrine cell. Interestingly, the AII rod amacrine cell was devoid of R2A-IR. Although the localization of the R2A subunit was anticipated in ganglion cells, amacrines and Müller cells, the presence of this receptor subunit to the cells in the outer retina was not expected. Here, both the R2A and the R2B subunits were found to be present in the outer segments of cone photoreceptors and to the tips of rod outer segments. Although the function of these receptor subunits in rod and cone photoreceptors remains to be determined, the fact that both R2A and R2B receptor subunits are localized to cone outer segments suggests a possible alternative pathway for calcium entry into a region where this cation plays such a crucial role in the process of phototransduction. To further classify the cells that display NR2A-IR, we performed dual labeling experiments showing the relationship between R2A-labeled cells with GABA. Results showed that all GABAergic-amacrines and displaced amacrines express the R2A-subunit protein. In addition, approximately 11% of the NR2A-labeled amacrines, did not stain for GABA. These findings support pharmacological data showing that NMDA directly facilitates GABA release in retina and retinal cultures [I.L. Ferreira, C.B. Duarte, P.F. Santos, C.M. Carvalho, A.P. Carvalho, Release of [3H]GABA evoked by glutamate receptor agonist in cultured chick retinal cells: effect of Ca2+, Brain Res. 664 (1994) 252-256; G.D. Zeevalk, W.J. Nicklas, Action of the anti-ischemic agent ifenprodil on N-methyl-d-aspartate and kainate-mediated excitotoxicity, Brain Res. 522 (1990) 135-139; R. Huba, H.D. Hofmann, Transmitter-gated currents of GABAergic amacrine-like cells in chick retinal cultures, Vis. Neurosci. 6 (1991) 303-314; M. Yamashita, R. Huba, H.D. Hofmann, Early in vitro development of voltage- and transmitter-gated currents in GABAergic amacrine cells, Dev. Brain Res. 82 (1994) 95-102; R. Ientile, S. Pedale, V. Picciurro, V. Macaione, C. Fabiano, S. Macaione, Nitric oxide mediates NMDA-evoked [3H]GABA release from chick retina cells, FEBS Lett. 417 (1997) 345-348; R.C. Kubrusly, M.C. deMello, F.G. deMello, Aspartate as a selective NMDA agonist in cultured cells from the avian retina, Neurochem. Intl. 32 (1998) 47-52] or reduction of GABA in vivo [N.N. Osborn, A.J. Herrera, The effect of experimental ischaemia and excitatory amino acid agonist on the GABA and serotonin immunoreactivities in the rabbit retina, Neurosci. 59 (1994) 1071-1081]. Since the majority of GABAergic synapses in the inner retina are onto both rod and cone bipolar axon terminals [R.G. Pourcho, M.T. Owzcarzak, Distribution of GABA immunoreactivity in the cat retina: A light and electron-microscopic study, Vis. Neurosci. 2 (1989) 425-435], we hypothesize that the NMDA-receptor plays a crucial role in providing feedback inhibition onto rod and cone bipolar cells. Copyright 1998 Elsevier Science B.V.

Suppression of NMDA receptor function in mice prenatally exposed to valproic acid improves social deficits and repetitive behaviors.

PubMed

Kang, Jaeseung; Kim, Eunjoon

2015-01-01

Animals prenatally exposed to valproic acid (VPA), an antiepileptic agent, have been used as a model for autism spectrum disorders (ASDs). Previous studies have identified enhanced NMDA receptor (NMDAR) function in the brain of VPA rats, and demonstrated that pharmacological suppression of NMDAR function normalizes social deficits in these animals. However, whether repetitive behavior, another key feature of ASDs, can be rescued by NMDAR inhibition remains unknown. We report here that memantine, an NMDAR antagonist, administered to VPA mice rescues both social deficits and repetitive behaviors such as self-grooming and jumping. These results suggest that suppression of elevated NMDAR function in VPA animals normalizes repetitive behaviors in addition to social deficits.

Disruption of hippocampal–prefrontal cortex activity by dopamine D2R-dependent LTD of NMDAR transmission

PubMed Central

Banks, Paul James; Burroughs, Amelia Caroline; Barker, Gareth Robert Isaac; Brown, Jon Thomas; Warburton, Elizabeth Clea; Bashir, Zafar Iqbal

2015-01-01

Functional connectivity between the hippocampus and prefrontal cortex (PFC) is essential for associative recognition memory and working memory. Disruption of hippocampal–PFC synchrony occurs in schizophrenia, which is characterized by hypofunction of NMDA receptor (NMDAR)-mediated transmission. We demonstrate that activity of dopamine D2-like receptors (D2Rs) leads selectively to long-term depression (LTD) of hippocampal–PFC NMDAR-mediated synaptic transmission. We show that dopamine-dependent LTD of NMDAR-mediated transmission profoundly disrupts normal synaptic transmission between hippocampus and PFC. These results show how dopaminergic activation induces long-term hypofunction of NMDARs, which can contribute to disordered functional connectivity, a characteristic that is a hallmark of psychiatric disorders such as schizophrenia. PMID:26286993

NMDAR antagonists for the treatment of diabetes mellitus-Current status and future directions.

PubMed

Welters, Alena; Klüppel, Carina; Mrugala, Jessica; Wörmeyer, Laura; Meissner, Thomas; Mayatepek, Ertan; Heiss, Christian; Eberhard, Daniel; Lammert, Eckhard

2017-09-01

Diabetes mellitus is characterized by chronically elevated blood glucose levels accelerated by a progressive decline of insulin-producing β-cells in the pancreatic islets. Although medications are available to transiently adjust blood glucose to normal levels, the effects of current drugs are limited when it comes to preservation of a critical mass of functional β-cells to sustainably maintain normoglycemia. In this review, we recapitulate recent evidence on the role of pancreatic N-methyl-D-aspartate receptors (NMDARs) in β-cell physiology, and summarize effects of morphinan-based NMDAR antagonists that are beneficial for insulin secretion, glucose tolerance and islet cell survival. We further discuss NMDAR-mediated molecular pathways relevant for neuronal cell survival, which may also be important for the preservation of β-cell function and mass. Finally, we summarize the literature for evidence on the role of NMDARs in the development of diabetic long-term complications, and highlight beneficial pharmacologic aspects of NMDAR antagonists in diabetic nephropathy, retinopathy as well as neuropathy. © 2017 John Wiley & Sons Ltd.

Separate Functional Properties of NMDARs Regulate Distinct Aspects of Spatial Cognition

ERIC Educational Resources Information Center

Sanders, Erin M.; Nyarko-Odoom, Akua O.; Zhao, Kevin; Nguyen, Michael; Liao, Hong Hong Liao; Keith, Matthew; Pyon, Jane; Kozma, Alyssa; Sanyal, Mohima; McHail, Daniel G.; Dumas, Theodore C.

2018-01-01

N-methyl-D-aspartate receptors (NMDARs) at excitatory synapses are central to activity-dependent synaptic plasticity and learning and memory. NMDARs act as ionotropic and metabotropic receptors by elevating postsynaptic calcium concentrations and by direct intracellular protein signaling. In the forebrain, these properties are controlled largely…

The role of NMDA receptors in the pathophysiology and treatment of mood disorders.

PubMed

Ghasemi, Mehdi; Phillips, Cristy; Trillo, Ludwig; De Miguel, Zurine; Das, Devsmita; Salehi, Ahmad

2014-11-01

Mood disorders such as major depressive disorder and bipolar disorder are chronic and recurrent illnesses that cause significant disability and affect approximately 350 million people worldwide. Currently available biogenic amine treatments provide relief for many and yet fail to ameliorate symptoms for others, highlighting the need to diversify the search for new therapeutic strategies. Here we present recent evidence implicating the role of N-methyl-D-aspartate receptor (NMDAR) signaling in the pathophysiology of mood disorders. The possible role of NMDARs in mood disorders has been supported by evidence demonstrating that: (i) both BPD and MDD are characterized by altered levels of central excitatory neurotransmitters; (ii) NMDAR expression, distribution, and function are atypical in patients with mood disorders; (iii) NMDAR modulators show positive therapeutic effects in BPD and MDD patients; and (iv) conventional antidepressants/mood stabilizers can modulate NMDAR function. Taken together, this evidence suggests the NMDAR system holds considerable promise as a therapeutic target for developing next generation drugs that may provide more rapid onset relief of symptoms. Identifying the subcircuits involved in mood and elucidating the role of NMDARs subtypes in specific brain circuits would constitute an important step toward the development of more effective therapies with fewer side effects. Copyright © 2014 Elsevier Ltd. All rights reserved.

Gestational methylazoxymethanol exposure leads to NMDAR dysfunction in hippocampus during early development and lasting deficits in learning.

PubMed

Snyder, Melissa A; Adelman, Alicia E; Gao, Wen-Jun

2013-01-01

The N-methyl-D-aspartate (NMDA) receptor has long been associated with learning and memory processes as well as diseased states, particularly in schizophrenia (SZ). Additionally, SZ is increasingly recognized as a neurodevelopmental disorder with cognitive impairments often preceding the onset of psychosis. However, the cause of these cognitive deficits and what initiates the pathological process is unknown. Growing evidence has implicated the glutamate system and, in particular, N-methyl-D-aspartate receptor (NMDAR) dysfunction in the pathophysiology of SZ. Yet, the vast majority of SZ-related research has focused on NMDAR function in adults leaving the role of NMDARs during development uncharacterized. We used the prenatal methylazoxymethanol acetate (MAM, E17) exposure model to determine the alterations of NMDAR protein levels and function, as well as associated cognitive deficits during development. We found that MAM-exposed animals have significantly altered NMDAR protein levels and function in the juvenile and adolescent hippocampus. Furthermore, these changes are associated with learning and memory deficits in the Morris Water Maze. Thus, in the prenatal MAM-exposure SZ model, NMDAR expression and function is altered during the critical period of hippocampal development. These changes may be involved in disease initiation and cognitive impairment in the early stage of SZ.

Activation of extrasynaptic, but not synaptic, NMDA receptors modifies amyloid precursor protein expression pattern and increases amyloid-ß production.

PubMed

Bordji, Karim; Becerril-Ortega, Javier; Nicole, Olivier; Buisson, Alain

2010-11-24

Calcium is a key mediator controlling essential neuronal functions depending on electrical activity. Altered neuronal calcium homeostasis affects metabolism of amyloid precursor protein (APP), leading to increased production of β-amyloid (Aβ), and contributing to the initiation of Alzheimer's disease (AD). A linkage between excessive glutamate receptor activation and neuronal Aβ release was established, and recent reports suggest that synaptic and extrasynaptic NMDA receptor (NMDAR) activation may have distinct consequences in plasticity, gene regulation, and neuronal death. Here, we report for the first time that prolonged activation of extrasynaptic NMDAR, but not synaptic NMDAR, dramatically increased the neuronal production of Aβ. This effect was preceded by a shift from APP695 to Kunitz protease inhibitory domain (KPI) containing APPs (KPI-APPs), isoforms exhibiting an important amyloidogenic potential. Conversely, after synaptic NMDAR activation, we failed to detect any KPI-APP expression and neuronal Aβ production was not modified. Calcium imaging data showed that intracellular calcium concentration after extrasynaptic NMDAR stimulation was lower than after synaptic activation. This suggests distinct signaling pathways for each pool of receptors. We found that modification of neuronal APP expression pattern triggered by extrasynaptic NMDAR activation was regulated at an alternative splicing level involving calcium-/calmodulin-dependent protein kinase IV, but overall APP expression remained identical. Finally, memantine dose-dependently inhibited extrasynaptic NMDAR-induced KPI-APPs expression as well as neuronal Aβ release. Altogether, these data suggest that a chronic activation of extrasynaptic NMDAR promotes amyloidogenic KPI-APP expression leading to neuronal Aβ release, representing a causal risk factor for developing AD.

Autistic-like social behaviour in Shank2-mutant mice improved by restoring NMDA receptor function.

PubMed

Won, Hyejung; Lee, Hye-Ryeon; Gee, Heon Yung; Mah, Won; Kim, Jae-Ick; Lee, Jiseok; Ha, Seungmin; Chung, Changuk; Jung, Eun Suk; Cho, Yi Sul; Park, Sae-Geun; Lee, Jung-Soo; Lee, Kyungmin; Kim, Daesoo; Bae, Yong Chul; Kaang, Bong-Kiun; Lee, Min Goo; Kim, Eunjoon

2012-06-13

Autism spectrum disorder (ASD) is a group of conditions characterized by impaired social interaction and communication, and restricted and repetitive behaviours. ASD is a highly heritable disorder involving various genetic determinants. Shank2 (also known as ProSAP1) is a multi-domain scaffolding protein and signalling adaptor enriched at excitatory neuronal synapses, and mutations in the human SHANK2 gene have recently been associated with ASD and intellectual disability. Although ASD-associated genes are being increasingly identified and studied using various approaches, including mouse genetics, further efforts are required to delineate important causal mechanisms with the potential for therapeutic application. Here we show that Shank2-mutant (Shank2(-/-)) mice carrying a mutation identical to the ASD-associated microdeletion in the human SHANK2 gene exhibit ASD-like behaviours including reduced social interaction, reduced social communication by ultrasonic vocalizations, and repetitive jumping. These mice show a marked decrease in NMDA (N-methyl-D-aspartate) glutamate receptor (NMDAR) function. Direct stimulation of NMDARs with D-cycloserine, a partial agonist of NMDARs, normalizes NMDAR function and improves social interaction in Shank2(-/-) mice. Furthermore, treatment of Shank2(-/-) mice with a positive allosteric modulator of metabotropic glutamate receptor 5 (mGluR5), which enhances NMDAR function via mGluR5 activation, also normalizes NMDAR function and markedly enhances social interaction. These results suggest that reduced NMDAR function may contribute to the development of ASD-like phenotypes in Shank2(-/-) mice, and mGluR modulation of NMDARs offers a potential strategy to treat ASD.

Mechanisms underlying differential effectiveness of memantine and ketamine in rapid antidepressant responses

PubMed Central

Gideons, Erinn S.; Kavalali, Ege T.; Monteggia, Lisa M.

2014-01-01

Ketamine is an NMDA receptor (NMDAR) antagonist that elicits rapid antidepressant responses in patients with treatment-resistant depression. However, ketamine can also produce psychotomimetic effects that limit its utility as an antidepressant, raising the question of whether the clinically tolerated NMDAR antagonist memantine possesses antidepressant properties. Despite its similar potency to ketamine as an NMDAR antagonist, clinical data suggest that memantine does not exert rapid antidepressant actions for reasons that are poorly understood. In this study, we recapitulate the ketamine and memantine clinical findings in mice, showing that ketamine, but not memantine, has antidepressant-like effects in behavioral models. Using electrophysiology in cultured hippocampal neurons, we show that ketamine and memantine effectively block NMDAR-mediated miniature excitatory postsynaptic currents in the absence of Mg2+. However, in physiological levels of extracellular Mg2+, we identified key functional differences between ketamine and memantine in their ability to block NMDAR function at rest. This differential effect of ketamine and memantine extends to intracellular signaling coupled to NMDAR at rest, in that memantine does not inhibit the phosphorylation of eukaryotic elongation factor 2 or augment subsequent expression of BDNF, which are critical determinants of ketamine-mediated antidepressant efficacy. These results demonstrate significant differences between the efficacies of ketamine and memantine on NMDAR-mediated neurotransmission that have impacts on downstream intracellular signaling, which we hypothesize is the trigger for rapid antidepressant responses. These data provide a novel framework on the necessary functional requirements of NMDAR-mediated neurotransmission as a critical determinant necessary to elicit rapid antidepressant responses. PMID:24912158

Differential functions of NR2A and NR2B in short-term and long-term memory in rats.

PubMed

Jung, Ye-Ha; Suh, Yoo-Hun

2010-08-23

N-methyl-D-aspartate receptors (NMDARs) are glutamate receptors implicated in synaptic plasticity and memory function. The specific functions of NMDA receptor subunits NR2A and NR2B have not yet been fully determined in the different types of memory. Nine Wistar rats (8-weeks-old) were subjected to the Morris water maze task to evaluate the memory behaviorally. Quantitative analysis of NR1, NR2A, and NR2B levels in the right and left forebrain of rats was performed and subunit associations with different types of memory were investigated using the Morris water maze task. Right forebrain NR2A expression was significantly increased and correlated with faster escape time onto a hidden platform, indicating involvement of short-term memory, because of the training time interval. Right forebrain NR2B expression was positively associated with long-term memory lasting 24-h (h). In the left forebrain, NR2B expression was positively related to 72-h long-term memory. In conclusion, the functions of NR2A and NR2B receptors were differentially specialized in short-term and long-term memory, depending on the right or left forebrain.

Septal cholinergic neuromodulation tunes the astrocyte-dependent gating of hippocampal NMDA receptors to wakefulness

PubMed Central

Papouin, Thomas; Dunphy, Jaclyn; Tolman, Michaela; Dineley, Kelly T.; Haydon, Philip G.

2017-01-01

Summary The activation of the N-methyl D-aspartate receptor (NMDAR) is controlled by a glutamate-binding site and a distinct, independently regulated, co-agonist-binding site. In most brain regions, the NMDAR co-agonist is the astrocyte-derived gliotransmitter D-serine. We found that D-serine levels oscillate in mouse hippocampus as a function of wakefulness, in vitro and in vivo. This causes a full saturation of the NMDAR co-agonist site in the dark (active)-phase that dissipates to sub-saturating levels during the light (sleep)-phase, and influences learning performance throughout the day. We demonstrate that hippocampal astrocytes sense the wakefulness-dependent activity of septal cholinergic fibers through the α7-nicotinic acetylcholine receptor (α7nAChR), whose activation drives D-serine release. We conclude that astrocytes tune the gating of synaptic NMDARs to the vigilance state and demonstrate that this is directly relevant to schizophrenia, a disorder characterized by NMDAR and cholinergic hypofunctions. Indeed, bypassing cholinergic activity with a clinically-tested α7nAChR agonist successfully enhances NMDARs activation. PMID:28479102

Mechanisms of action and clinical efficacy of NMDA receptor modulators in mood disorders.

PubMed

Ghasemi, Mehdi; Phillips, Cristy; Fahimi, Atoossa; McNerney, Margaret Windy; Salehi, Ahmad

2017-09-01

Although the biogenic amine models have provided meaningful links between clinical phenomena and pharmacological management of mood disorders (MDs), the onset of action of current treatments is slow and a proportion of individuals fail to adequately respond. A growing number of investigations have focused on the glutamatergic system as a viable target. Herein we review the putative role of N-methyl-d-aspartate (NMDA) signaling in the pathophysiology of MDs. Prompting this focus are several lines of evidence: 1) altered glutamate and NMDA receptor (NMDAR) expression and functioning; 2) antidepressant effects of NMDAR signaling blockers; 3) interaction between conventional therapeutic regimens and NMDAR signaling modulators; 4) biochemical evidence of interaction between monoaminergic system and NMDAR signaling; 5) interaction between neurotrophic factors and NMDAR signaling in mood regulation; 6) cross-talk between NMDAR signaling and inflammatory processes; and 7) antidepressant effects of a number of NMDA modulators in recent clinical trials. Altogether, these studies establish a warrant for the refinement of novel compounds that target glutamatergic mechanisms for the treatment of MDs. Published by Elsevier Ltd.

Felbamate but not phenytoin or gabapentin reduces glutamate release by blocking presynaptic NMDA receptors in the entorhinal cortex

PubMed Central

Yang, Jian; Wetterstrand, Caroline; Jones, Roland S.G.

2007-01-01

Summary We have shown that a number of anticonvulsant drugs can reduce glutamate release at synapses in the rat entorhinal cortex (EC) in vitro. We have also shown that presynaptic NMDA receptors (NMDAr) tonically facilitate glutamate release at these synapses. In the present study we determined whether, phenytoin, gabapentin and felbamate may reduce glutamate release by blocking the presynaptic NMDAr. Whole cell patch clamp recordings of spontaneous excitatory postsynaptic currents (sEPSCs) were used as a monitor of presynaptic glutamate release. Postsynaptic NMDAr were blocked with internal dialysis with an NMDAr channel blocker. The antagonist, 2-AP5, reduced the frequency of sEPSCs by blocking the presynaptic facilitatory NMDAr, but did not occlude a reduction in sEPSC frequency by gabapentin or phenytoin. Felbamate also reduced sEPSC frequency, but this effect was occluded by prior application of 2-AP5. Thus, whilst all three drugs can reduce glutamate release, only the action of felbamate seems to be due to interaction with presynaptic NMDAr. PMID:17980555

A non-ionotropic activity of NMDA receptors contributes to glycine-induced neuroprotection in cerebral ischemia-reperfusion injury.

PubMed

Chen, Juan; Hu, Rong; Liao, Huabao; Zhang, Ya; Lei, Ruixue; Zhang, Zhifeng; Zhuang, Yang; Wan, Yu; Jin, Ping; Feng, Hua; Wan, Qi

2017-06-15

NMDA receptor (NMDAR) is known for its ionotropic function. But recent evidence suggests that NMDAR also has a non-ionotropic property. To determine the role of non-ionotropic activity of NMDARs in clinical relevant conditions, we tested the effect of glycine, a co-agonist of NMDARs, in rat middle cerebral artery occlusion (MCAO), an animal model of cerebral ischemia-reperfusion injury after the animals were injected with the NMDAR channel blocker MK-801 and the glycine receptor antagonist strychnine. We show that glycine reduces the infarct volume in the brain of ischemic stroke animals pre-injected with MK-801 and strychnine. The effect of glycine is sensitive to the antagonist of glycine-GluN1 binding site and blocked by Akt inhibition. In the neurobehavioral tests, glycine improves the functional recovery of stroke animals pre-injected with MK-801 and strychnine. This study suggests that glycine-induced neuroprotection is mediated in part by the non-ionotropic activity of NMDARs via Akt activation in cerebral ischemia-reperfusion injury.

Emerging structural insights into the function of ionotropic glutamate receptors

PubMed Central

Karakas, Erkan; Regan, Michael C.; Furukawa, Hiro

2015-01-01

Summary Ionotropic glutamate receptors (iGluRs) are ligand-gated ion channels that mediate excitatory neurotransmission crucial for brain development and function including learning and memory formation. Recently a wealth of structural studies on iGluRs, including AMPA receptors (AMPARs), kainate receptors, and NMDA receptors (NMDARs) became available.. These studies showed structures of non-NMDARs including AMPAR and kainate receptor in various functional states, thereby providing the first visual sense of how non-NMDAR iGluRs may function in the context of homotetramers. Furthermore, they provided the first view of heterotetrameric NMDAR ion channels, which illuminated the similarities with and differences from non-NMDARs, thus raising a mechanistic distinction between the two groups of iGluRs. Here we review mechanistic insights into iGluR functions gained through structural studies of multiple groups. PMID:25941168

Calpain inhibition reduces NMDA receptor rundown in rat substantia nigra dopamine neurons.

PubMed

Zhao, Jerry; Baudry, Michel; Jones, Susan

2018-05-04

Repeated activation of N-Methyl-d-aspartate receptors (NMDARs) causes a Ca 2+ -dependent reduction in NMDAR-mediated current in dopamine (DA) neurons of the substantia nigra pars compacta (SNc) in one week old rats; however, a Ca 2+ -dependent regulatory protein has not been identified. The role of the Ca 2+ -dependent cysteine protease, calpain, in mediating NMDAR current rundown was investigated. In brain slices from rats aged postnatal day 7-9 ('P7'), bath application of either of the membrane permeable calpain inhibitors, N-Acetyl-L-leucyl-L-leucyl-L-norleucinal (ALLN, 20 μM) or MDL-28170 (30 μM) significantly reduced whole-cell NMDAR current rundown. To investigate the role of the calpain-2 isoform, the membrane permeable calpain-2 inhibitor, Z-Leu-Abu-CONH-CH2-C6H3 (3, 5-(OMe)2 (C2I, 200 nM), was applied; C2I application significantly reduced whole cell NMDAR current rundown. Interestingly, ALLN but not C2I significantly reduced rundown of NMDA-EPSCs. These results suggest the calpain-2 isoform mediates Ca 2+ -dependent regulation of extrasynaptic NMDAR current in the first postnatal week, while calpain-1 might mediate rundown of synaptic NMDAR currents. One week later in postnatal development, at P12-P16 ('P14'), there was significantly less rundown in SNc-DA neurons, and no significant effect on rundown of either Ca 2+ chelation or treatment with the calpain inhibitor, ALLN, suggesting that the rundown observed in SNc-DA neurons from two week-old rats might be Ca 2+ -independent. In conclusion, Ca 2+ -dependent rundown of extrasynaptic NMDAR currents in SNc DA neurons involves calpain-2 activation, but Ca 2+ - and calpain-2-dependent NMDAR current rundown is developmentally regulated. Copyright © 2018 Elsevier Ltd. All rights reserved.

The Frequency of Autoimmune N-Methyl-D-Aspartate Receptor Encephalitis Surpasses That of Individual Viral Etiologies in Young Individuals Enrolled in the California Encephalitis Project

PubMed Central

Sheriff, Heather; Dalmau, Josep; Tilley, Drake H.; Glaser, Carol A.

2012-01-01

Background. In 2007, the California Encephalitis Project (CEP), which was established to study the epidemiology of encephalitis, began identifying cases of anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis. Increasing numbers of anti-NMDAR encephalitis cases have been identified at the CEP, and this form rivals commonly known viral etiologies as a causal agent. We report here the relative frequency and differences among encephalitides caused by anti-NMDAR and viral etiologies within the CEP experience. Methods. Demographic, frequency, and clinical data from patients with anti-NMDAR encephalitis are compared with those with viral encephalitic agents: enterovirus, herpes simplex virus type 1 (HSV-1), varicella-zoster virus (VZV), and West Nile virus (WNV). All examined cases presented to the CEP between September 2007 and February 2011 and are limited to individuals aged ≤30 years because of the predominance of anti-NMDAR encephalitis in this group. The diagnostic costs incurred in a single case are also included. Results. Anti-NMDAR encephalitis was identified >4 times as frequently as HSV-1, WNV, or VZV and was the leading entity identified in our cohort. We found that 65% of anti-NMDAR encephalitis occurred in patients aged ≤18 years. This disorder demonstrated a predilection, which was not observed with viral etiologies, for females (P < .01). Seizures, language dysfunction, psychosis, and electroencephalographic abnormalities were significantly more frequent in patients with anti-NMDAR encephalitis (P < .05), and autonomic instability occurred exclusively in this group. Discussion. Anti-NMDAR encephalitis rivals viral etiologies as a cause of encephalitis within the CEP cohort. This entity deserves a prominent place on the encephalitic differential diagnosis to avoid unnecessary diagnostic and treatment costs, and to permit a more timely treatment. PMID:22281844

Seizure-Induced Regulations of Amyloid-β, STEP61, and STEP61 Substrates Involved in Hippocampal Synaptic Plasticity

PubMed Central

Jang, Sung-Soo; Royston, Sara E.; Lee, Gunhee; Wang, Shuwei; Chung, Hee Jung

2016-01-01

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive decline. Pathologic accumulation of soluble amyloid-β (Aβ) oligomers impairs synaptic plasticity and causes epileptic seizures, both of which contribute to cognitive dysfunction in AD. However, whether seizures could regulate Aβ-induced synaptic weakening remains unclear. Here we show that a single episode of electroconvulsive seizures (ECS) increased protein expression of membrane-associated STriatal-Enriched protein tyrosine Phosphatase (STEP61) and decreased tyrosine-phosphorylation of its substrates N-methyl D-aspartate receptor (NMDAR) subunit GluN2B and extracellular signal regulated kinase 1/2 (ERK1/2) in the rat hippocampus at 2 days following a single ECS. Interestingly, a significant decrease in ERK1/2 expression and an increase in APP and Aβ levels were observed at 3-4 days following a single ECS when STEP61 level returned to the baseline. Given that pathologic levels of Aβ increase STEP61 activity and STEP61-mediated dephosphorylation of GluN2B and ERK1/2 leads to NMDAR internalization and ERK1/2 inactivation, we propose that upregulation of STEP61 and downregulation of GluN2B and ERK1/2 phosphorylation mediate compensatory weakening of synaptic strength in response to acute enhancement of hippocampal network activity, whereas delayed decrease in ERK1/2 expression and increase in APP and Aβ expression may contribute to the maintenance of this synaptic weakening. PMID:27127657

New perspectives in glutamate and anxiety.

PubMed

Riaza Bermudo-Soriano, Carlos; Perez-Rodriguez, M Mercedes; Vaquero-Lorenzo, Concepcion; Baca-Garcia, Enrique

2012-02-01

Anxiety and stress-related disorders, namely posttraumatic stress disorder (PTSD), generalized anxiety disorder (GAD), obsessive-compulsive disorder (ODC), social and specific phobias, and panic disorder, are a major public health issue. A growing body of evidence suggests that glutamatergic neurotransmission may be involved in the biological mechanisms underlying stress response and anxiety-related disorders. The glutamatergic system mediates the acquisition and extinction of fear-conditioning. Thus, new drugs targeting glutamatergic neurotransmission may be promising candidates for new pharmacological treatments. In particular, N-methyl-d-aspartate receptors (NMDAR) antagonists (AP5, AP7, CGP37849, CGP39551, LY235959, NPC17742, and MK-801), NMDAR partial agonists (DCS, ACPC), α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptors (AMPARs) antagonists (topiramate), and several allosteric modulators targeting metabotropic glutamate receptors (mGluRs) mGluR1, mGluR2/3, and mGluR5, have shown anxiolytic-like effects in several animal and human studies. Several studies have suggested that polyamines (agmatine, putrescine, spermidine, and spermine) may be involved in the neurobiological mechanisms underlying stress-response and anxiety-related disorders. This could mainly be attributed to their ability to modulate ionotropic glutamate receptors, especially NR2B subunits. The aim of this review is to establish that glutamate neurotransmission and polyaminergic system play a fundamental role in the onset of anxiety-related disorders. This may open the way for new drugs that may help to treat these conditions. Copyright © 2011 Elsevier Inc. All rights reserved.

Enhancing Effects of NMDA-Receptor Blockade on Extinction Learning and Related Brain Activation Are Modulated by BMI

PubMed Central

Golisch, Anne; Heba, Stefanie; Glaubitz, Benjamin; Tegenthoff, Martin; Lissek, Silke

2017-01-01

A distributed network including prefrontal and hippocampal regions is involved in context-related extinction learning as well as in renewal. Renewal describes the recovery of an extinguished response if the context of extinction differs from the context of recall. Animal studies have demonstrated that prefrontal, but not hippocampal N-methyl-D-aspartate receptor (NMDAR) antagonism disrupted extinction learning and processing of task context. However, human studies of NMDAR in extinction learning are lacking, while NMDAR antagonism yielded contradictory results in other learning tasks. This fMRI study investigated the role of NMDAR for human behavioral and brain activation correlates of extinction and renewal. Healthy volunteers received a single dose of the NMDAR antagonist memantine prior to extinction of previously acquired stimulus-outcome associations presented in either identical or novel contexts. We observed better, and partly faster, extinction learning in participants receiving the NMDAR antagonist compared to placebo. However, memantine did not affect renewal. In both extinction and recall, the memantine group showed a deactivation in extinction-related brain regions, particularly in the prefrontal cortex, while hippocampal activity was increased. This higher hippocampal activation was in turn associated with the participants' body mass index (BMI) and extinction errors. Our results demonstrate potentially dose-related enhancing effects of memantine and highlight involvement of hippocampal NMDAR in context-related extinction learning. PMID:28326025

NMDA receptors in mouse anterior piriform cortex initialize early odor preference learning and L-type calcium channels engage for long-term memory.

PubMed

Mukherjee, Bandhan; Yuan, Qi

2016-10-14

The interactions of L-type calcium channels (LTCCs) and NMDA receptors (NMDARs) in memories are poorly understood. Here we investigated the specific roles of anterior piriform cortex (aPC) LTCCs and NMDARs in early odor preference memory in mice. Using calcium imaging in aPC slices, LTCC activation was shown to be dependent on NMDAR activation. Either D-APV (NMDAR antagonist) or nifedipine (LTCC antagonist) reduced somatic calcium transients in pyramidal cells evoked by lateral olfactory tract stimulation. However, nifedipine did not further reduce calcium in the presence of D-APV. In mice that underwent early odor preference training, blocking NMDARs in the aPC prevented short-term (3 hr) and long-term (24 hr) odor preference memory, and both memories were rescued when BayK-8644 (LTCC agonist) was co-infused. However, activating LTCCs in the absence of NMDARs resulted in loss of discrimination between the conditioned odor and a similar odor mixture at 3 hr. Elevated synaptic AMPAR expression at 3 hr was prevented by D-APV infusion but restored when LTCCs were directly activated, mirroring the behavioral outcomes. Blocking LTCCs prevented 24 hr memory and spared 3 hr memory. These results suggest that NMDARs mediate stimulus-specific encoding of odor memory while LTCCs mediate intracellular signaling leading to long-term memory.

Traces of Memory: Reacquisition of Fear Following Forgetting Is NMDAr-Independent

ERIC Educational Resources Information Center

Li, Stella; Richardson, Rick

2013-01-01

Recent research shows that while initial learning is dependent on "N"-methyl-D-aspartate receptors (NMDArs), relearning can be NMDAr-independent. In the present study we examined whether this switch also occurs following forgetting. The developing animal exhibits much more rapid rates of forgetting than adults, so infant rats were used. It was…

CaMKII Regulates Synaptic NMDA Receptor Activity of Hypothalamic Presympathetic Neurons and Sympathetic Outflow in Hypertension.

PubMed

Li, De-Pei; Zhou, Jing-Jing; Zhang, Jixiang; Pan, Hui-Lin

2017-11-01

NMDAR activity in the hypothalamic paraventricular nucleus (PVN) is increased and critically involved in heightened sympathetic vasomotor tone in hypertension. Calcium/calmodulin-dependent protein kinase II (CaMKII) binds to and modulates NMDAR activity. In this study, we determined the role of CaMKII in regulating NMDAR activity of PVN presympathetic neurons in male spontaneously hypertensive rats (SHRs). NMDAR-mediated EPSCs and puff NMDA-elicited currents were recorded in spinally projecting PVN neurons in SHRs and male Wistar-Kyoto (WKY) rats. The basal amplitude of evoked NMDAR-EPSCs and puff NMDA currents in retrogradely labeled PVN neurons were significantly higher in SHRs than in WKY rats. The CaMKII inhibitor autocamtide-2-related inhibitory peptide (AIP) normalized the increased amplitude of NMDAR-EPSCs and puff NMDA currents in labeled PVN neurons in SHRs but had no effect in WKY rats. Treatment with AIP also normalized the higher frequency of NMDAR-mediated miniature EPSCs of PVN neurons in SHRs. CaMKII-mediated phosphorylation level of GluN2B serine 1303 (S1303) in the PVN, but not in the hippocampus and frontal cortex, was significantly higher in SHRs than in WKY rats. Lowering blood pressure with celiac ganglionectomy in SHRs did not alter the increased level of phosphorylated GluN2B S1303 in the PVN. In addition, microinjection of AIP into the PVN significantly reduced arterial blood pressure and lumbar sympathetic nerve discharges in SHRs. Our findings suggest that CaMKII activity is increased in the PVN and contributes to potentiated presynaptic and postsynaptic NMDAR activity to elevate sympathetic vasomotor tone in hypertension. SIGNIFICANCE STATEMENT Heightened sympathetic vasomotor tone is a major contributor to the development of hypertension. Although glutamate NMDA receptor (NMDAR)-mediated excitatory drive in the hypothalamus plays a critical role in increased sympathetic output in hypertension, the molecular mechanism involved in potentiated NMDAR activity of hypothalamic presympathetic neurons remains unclear. Here we show that the activity of calcium/calmodulin-dependent protein kinase II (CaMKII) is increased and plays a key role in the potentiated presynaptic and postsynaptic NMDAR activity of hypothalamic presympathetic neurons in hypertension. Also, the inhibition of CaMKII in the hypothalamus reduces elevated blood pressure and sympathetic nerve discharges in hypertension. This new knowledge extends our understanding of the mechanism of synaptic plasticity in the hypothalamus and suggests new strategies to treat neurogenic hypertension. Copyright © 2017 the authors 0270-6474/17/3710690-10$15.00/0.

Ethanol preconditioning of rat cerebellar cultures targets NMDA receptors to the synapse and enhances peroxiredoxin 2 expression.

PubMed

Mitchell, Robert M; Tajuddin, Nuzhath; Campbell, Edward M; Neafsey, Edward J; Collins, Michael A

2016-07-01

Epidemiological studies indicate that light-moderate alcohol (ethanol) consumers tend to have reduced risks of cognitive impairment and progression to dementia during aging. Exploring possible mechanisms, we previously found that moderate ethanol preconditioning (MEP, 20-30mM) of rat brain cultures for several days instigated neuroprotection against β-amyloid peptides. Our biochemical evidence implicated the NMDA receptor (NMDAR) as a potential neuroprotective "sensor", specifically via synaptic NMDAR signaling. It remains unclear how ethanol modulates the receptor and its downstream targets to engender neuroprotection. Here we confirm with deconvolution microscopy that MEP of rat mixed cerebellar cultures robustly increases synaptic NMDAR localization. Phospho-activation of the non-receptor tyrosine kinases Src and Pyk2, known to be linked to synaptic NMDAR, is also demonstrated. Additionally, the preconditioning enhances levels of an antioxidant protein, peroxiredoxin 2 (Prx2), reported to be downstream of synaptic NMDAR signaling, and NMDAR antagonism with memantine (earlier found to abrogate MEP neuroprotection) blocks the Prx2 elevations. To further link Prx2 with antioxidant-based neuroprotection, we circumvented the ethanol preconditioning-NMDAR pathway by pharmacologically increasing Prx2 with the naturally-occurring cruciferous compound, 3H-1,2-dithiole-3-thione (D3T). Thus, D3T pretreatment elevated Prx2 expression to a similar extent as MEP, while concomitantly preventing β-amyloid neurotoxicity; D3T also protected the cultures from hydrogen peroxide toxicity. The findings support a mechanism that couples synaptic NMDAR signaling, Prx2 expression and augmented antioxidant defenses in ethanol preconditioning-induced neuroprotection. That this mechanism can be emulated by a cruciferous vegetable constituent suggests that such naturally-occurring "neutraceuticals" may be useful in therapy for oxidative stress-related dementias. Copyright © 2016 Elsevier B.V. All rights reserved.

Differential effects of early-life NMDA receptor antagonism on aspartame-impaired insulin tolerance and behavior.

PubMed

Collison, Kate S; Inglis, Angela; Shibin, Sherin; Andres, Bernard; Ubungen, Rosario; Thiam, Jennifer; Mata, Princess; Al-Mohanna, Futwan A

2016-12-01

We have previously showed that lifetime exposure to aspartame, commencing in utero via the mother's diet, may impair insulin tolerance and cause behavioral deficits in adulthood via mechanisms which are incompletely understood. The role of the CNS in regulating glucose homeostasis has been highlighted by recent delineation of the gut-brain axis, in which N-methyl-d-aspartic acid receptors (NMDARs) are important in maintaining glucose homeostasis, in addition to regulating certain aspects of behavior. Since the gut-brain axis can be modulated by fetal programming, we hypothesized that early-life NMDAR antagonism may affect aspartame-induced glucose deregulation in adulthood, and may alter the aspartame behavioral phenotype. Accordingly, C57Bl/6J mice were chronically exposed to aspartame commencing in utero, in the presence and absence of maternal administration of the competitive NMDAR antagonist CGP 39551, from conception until weaning. Drug/diet interactions in adulthood glucocentric and behavioral parameters were assessed. Aspartame exposure elevated blood glucose and impaired insulin-induced glucose disposal during an insulin tolerance test, which could be normalized by NMDAR antagonism. The same effects were not observed in control diet mice, suggesting an early-life drug/diet interaction. Behavioral analysis of adult offspring indicated that NMDAR antagonism of control diet mice caused hyperlocomotion and impaired spatial navigation. Conversely hypolocomotion, reduced exploratory activity and increased anxiety-related behavior were apparent in aspartame diet mice with early-life NMDAR antagonism. significant drug/diet interactions in glucocentric and behavioral parameters were identified in aspartame-exposed mice with early-life NMDAR antagonism. This suggests a possible involvement of early NMDAR interactions in aspartame-impaired glucose homeostasis and behavioral deficits. Copyright © 2016 Elsevier Inc. All rights reserved.

Neurosteroid-like Inhibitors of N-Methyl-d-aspartate Receptor: Substituted 2-Sulfates and 2-Hemisuccinates of Perhydrophenanthrene.

PubMed

Slavikova, Barbora; Chodounska, Hana; Nekardova, Michaela; Vyklicky, Vojtech; Ladislav, Marek; Hubalkova, Pavla; Krausova, Barbora; Vyklicky, Ladislav; Kudova, Eva

2016-05-26

N-Methyl-d-aspartate receptors (NMDARs) display a critical role in various diseases of the central nervous system. The activity of NMDARs can be modulated by neurosteroids. Herein, we report a structure-activity relationship study for perhydrophenanthrene analogues possessing a framework that mimics the steroidal ring system. This study comprises the design, synthesis, and assessment of the biological activity of a library of perhydrophenanthrene 2-sulfates and 2-hemisuccinates (1-10). Their ability to modulate NMDAR-induced currents was tested on recombinant GluN1/GluN2B receptors. Our results demonstrate that such structural optimization leads to compounds that are inhibitors of NMDARs. Notably, compound 9 (IC50 = 15.6 μM) was assessed as a more potent inhibitor of NMDAR-induced currents than the known endogenous neurosteroid, pregnanolone sulfate (IC50 = 24.6 μM).

The sigma-1 receptor modulates NMDA receptor synaptic transmission and plasticity via SK channels in rat hippocampus

PubMed Central

Martina, Marzia; Turcotte, Marie-Eve B; Halman, Samantha; Bergeron, Richard

2007-01-01

The sigma receptor (σR), once considered a subtype of the opioid receptor, is now described as a distinct pharmacological entity. Modulation of N-methyl-d-aspartate receptor (NMDAR) functions by σR-1 ligands is well documented; however, its mechanism is not fully understood. Using patch-clamp whole-cell recordings in CA1 pyramidal cells of rat hippocampus and (+)pentazocine, a high-affinity σR-1 agonist, we found that σR-1 activation potentiates NMDAR responses and long-term potentiation (LTP) by preventing a small conductance Ca2+-activated K+ current (SK channels), known to shunt NMDAR responses, to open. Therefore, the block of SK channels and the resulting increased Ca2+ influx through the NMDAR enhances NMDAR responses and LTP. These results emphasize the importance of the σR-1 as postsynaptic regulator of synaptic transmission. PMID:17068104

The sigma-1 receptor modulates NMDA receptor synaptic transmission and plasticity via SK channels in rat hippocampus.

PubMed

Martina, Marzia; Turcotte, Marie-Eve B; Halman, Samantha; Bergeron, Richard

2007-01-01

The sigma receptor (sigmaR), once considered a subtype of the opioid receptor, is now described as a distinct pharmacological entity. Modulation of N-methyl-D-aspartate receptor (NMDAR) functions by sigmaR-1 ligands is well documented; however, its mechanism is not fully understood. Using patch-clamp whole-cell recordings in CA1 pyramidal cells of rat hippocampus and (+)pentazocine, a high-affinity sigmaR-1 agonist, we found that sigmaR-1 activation potentiates NMDAR responses and long-term potentiation (LTP) by preventing a small conductance Ca2+-activated K+ current (SK channels), known to shunt NMDAR responses, to open. Therefore, the block of SK channels and the resulting increased Ca2+ influx through the NMDAR enhances NMDAR responses and LTP. These results emphasize the importance of the sigmaR-1 as postsynaptic regulator of synaptic transmission.

Emerging structural insights into the function of ionotropic glutamate receptors.

PubMed

Karakas, Erkan; Regan, Michael C; Furukawa, Hiro

2015-06-01

Ionotropic glutamate receptors (iGluRs) are ligand-gated ion channels that mediate excitatory neurotransmission crucial for brain development and function, including learning and memory formation. Recently a wealth of structural studies on iGluRs including AMPA receptors (AMPARs), kainate receptors, and NMDA receptors (NMDARs) became available. These studies showed structures of non-NMDARs including AMPAR and kainate receptor in various functional states, thereby providing the first visual sense of how non-NMDAR iGluRs may function in the context of homotetramers. Furthermore, they provided the first view of heterotetrameric NMDAR ion channels, and this illuminated the similarities with and differences from non-NMDARs, thus raising a mechanistic distinction between the two groups of iGluRs. We review mechanistic insights into iGluR functions gained through structural studies of multiple groups. Copyright © 2015 Elsevier Ltd. All rights reserved.

Increased serum anti-N-methyl-D-aspartate receptor antibody immunofluorescence in psychiatric patients with past catatonia

PubMed Central

Lin, Chin-Chuen; Hung, Yi-Yung; Tsai, Meng-Chang

2017-01-01

Objective Anti-N-methyl-D-aspartate receptor (NMDAR) antibody was thought to be the cause of anti-NMDAR encephalitis, with manifestations similar to catatonia and schizophrenia. Anti-NMDAR antibody in neuropsychiatric patients who had catatonia before were investigated in a follow-up evaluation. The intensity of antibody immunofluorescence was quantified and compared with healthy controls. Method Nineteen patients (eight males and eleven females) agreed to be followed-up. Thirteen had the diagnosis of schizophrenia, two had the diagnosis of major depressive disorder, two had bipolar disorder, one had postpartum depression, and one had herpes simplex encephalitis. No patient had catatonia during the follow-up. Nineteen sex-matched healthy controls were recruited. Results Using Mann-Whitney U test, patients had greater intensity of anti-NMDAR antibody immunofluorescence than the healthy controls (121,979 ± 86,526 vs. 47,692 ± 26,102, p = 0.003). No correlation was found between immunofluorescence intensity and catatonia scales or symptom severity scores. Neuropsychiatric patients with past catatonia showed greater anti-NMDAR antibody response than the healthy controls. Conclusion NMDAR dysfunction might play a role in the mechanism underlying catatonia. Further studies are needed to confirm this finding. PMID:29073246

Increased serum anti-N-methyl-D-aspartate receptor antibody immunofluorescence in psychiatric patients with past catatonia.

PubMed

Lin, Chin-Chuen; Hung, Yi-Yung; Tsai, Meng-Chang; Huang, Tiao-Lai

2017-01-01

Anti-N-methyl-D-aspartate receptor (NMDAR) antibody was thought to be the cause of anti-NMDAR encephalitis, with manifestations similar to catatonia and schizophrenia. Anti-NMDAR antibody in neuropsychiatric patients who had catatonia before were investigated in a follow-up evaluation. The intensity of antibody immunofluorescence was quantified and compared with healthy controls. Nineteen patients (eight males and eleven females) agreed to be followed-up. Thirteen had the diagnosis of schizophrenia, two had the diagnosis of major depressive disorder, two had bipolar disorder, one had postpartum depression, and one had herpes simplex encephalitis. No patient had catatonia during the follow-up. Nineteen sex-matched healthy controls were recruited. Using Mann-Whitney U test, patients had greater intensity of anti-NMDAR antibody immunofluorescence than the healthy controls (121,979 ± 86,526 vs. 47,692 ± 26,102, p = 0.003). No correlation was found between immunofluorescence intensity and catatonia scales or symptom severity scores. Neuropsychiatric patients with past catatonia showed greater anti-NMDAR antibody response than the healthy controls. NMDAR dysfunction might play a role in the mechanism underlying catatonia. Further studies are needed to confirm this finding.

Non-Ionotropic NMDA Receptor Signaling Drives Activity-Induced Dendritic Spine Shrinkage.

PubMed

Stein, Ivar S; Gray, John A; Zito, Karen

2015-09-02

The elimination of dendritic spine synapses is a critical step in the refinement of neuronal circuits during development of the cerebral cortex. Several studies have shown that activity-induced shrinkage and retraction of dendritic spines depend on activation of the NMDA-type glutamate receptor (NMDAR), which leads to influx of extracellular calcium ions and activation of calcium-dependent phosphatases that modify regulators of the spine cytoskeleton, suggesting that influx of extracellular calcium ions drives spine shrinkage. Intriguingly, a recent report revealed a novel non-ionotropic function of the NMDAR in the regulation of synaptic strength, which relies on glutamate binding but is independent of ion flux through the receptor (Nabavi et al., 2013). Here, we tested whether non-ionotropic NMDAR signaling could also play a role in driving structural plasticity of dendritic spines. Using two-photon glutamate uncaging and time-lapse imaging of rat hippocampal CA1 neurons, we show that low-frequency glutamatergic stimulation results in shrinkage of dendritic spines even in the presence of the NMDAR d-serine/glycine binding site antagonist 7-chlorokynurenic acid (7CK), which fully blocks NMDAR-mediated currents and Ca(2+) transients. Notably, application of 7CK or MK-801 also converts spine enlargement resulting from a high-frequency uncaging stimulus into spine shrinkage, demonstrating that strong Ca(2+) influx through the NMDAR normally overcomes a non-ionotropic shrinkage signal to drive spine growth. Our results support a model in which NMDAR signaling, independent of ion flux, drives structural shrinkage at spiny synapses. Dendritic spine elimination is vital for the refinement of neural circuits during development and has been linked to improvements in behavioral performance in the adult. Spine shrinkage and elimination have been widely accepted to depend on Ca(2+) influx through NMDA-type glutamate receptors (NMDARs) in conjunction with long-term depression (LTD) of synaptic strength. Here, we use two-photon glutamate uncaging and time-lapse imaging to show that non-ionotropic NMDAR signaling can drive shrinkage of dendritic spines, independent of NMDAR-mediated Ca(2+) influx. Signaling through p38 MAPK was required for this activity-dependent spine shrinkage. Our results provide fundamental new insights into the signaling mechanisms that support experience-dependent changes in brain structure. Copyright © 2015 the authors 0270-6474/15/3512303-06$15.00/0.

Spontaneous seizures in a rat model of multiple prenatal freeze lesioning.

PubMed

Kamada, Takashi; Sun, Wei; Takase, Kei-Ichiro; Shigeto, Hiroshi; Suzuki, Satoshi O; Ohyagi, Yasumasa; Kira, Jun-Ichi

2013-08-01

Focal cortical dysplasia (FCD) is an important cause of intractable epilepsy. Previous rat studies have utilized freeze lesioning of neonatal animals to model FCD; however, such models are unable to demonstrate spontaneous seizures without seizure-provoking events. Therefore, we created an animal model with multiple FCD, produced during embryonic development, and observed whether spontaneous seizures occurred. Furthermore, we examined the relationship between FCD and epileptogenesis using immunohistochemistry. At 18 days postconception, a frozen metal probe was placed bilaterally on the scalps of Sprague-Dawley rat embryos through the uterus wall to produce multiple FCD. Electroencephalogram (EEG) and video recording were performed from postnatal day (P) 35 to P77. Brain tissues were examined immunohistochemically at P28 and P78 using semiquantitative densitometry. Eleven of 16 rats (68.8%) showed spontaneous seizures arising in the hippocampus from P47. Movement cessation followed by sniffing and mastication, culminating in wet-dog shaking, was seen during the hippocampal EEG discharges. FCD was observed in the bilateral frontoparietal lobes. The expression levels of N-methyl-d-aspartate receptor (NMDAR) subunits 1, 2A, 2B, the glutamate/aspartate transporter and the glial glutamate transporter 1 (GLT1) at FCD sites were increased at P28 and P78. There were no major histological abnormalities in the hippocampi compared with those in the cortex. However, the expression levels of NMDAR 2A and 2B were increased at P28. Levels of NMDAR1, 2A and 2B, the glutamate/aspartate transporter and GLT1 were also increased at P78. We created an animal model showing spontaneous seizures without a provoking event except for the existence of cortical dysplasia, and without a genetic or general systematic cause like MAM injection or irradiation. The seizures resembled human temporal lobe epilepsy both clinically and on EEG. Alterations in the levels of glutamatergic and GABAergic receptors were investigated during growth. This model should enable better clarification of the mechanisms underlying the development of human epilepsy. Copyright © 2013 Elsevier B.V. All rights reserved.

Prepuberal Stimulation of 5-HT7-R by LP-211 in a Rat Model of Hyper-Activity and Attention-Deficit: Permanent Effects on Attention, Brain Amino Acids and Synaptic Markers in the Fronto-Striatal Interface

PubMed Central

Treno, Concetta; Gironi Carnevale, Ugo A.; Arra, Claudio; Nieddu, Maria; Pagano, Cristina; Illiano, Placido; Barbato, Fabiana; Carboni, Ezio; Laviola, Giovanni; Lacivita, Enza; Leopoldo, Marcello; Adriani, Walter; Sadile, Adolfo G.

2014-01-01

The cross-talk at the prefronto-striatal interface involves excitatory amino acids, different receptors, transducers and modulators. We investigated long-term effects of a prepuberal, subchronic 5-HT7-R agonist (LP-211) on adult behaviour, amino acids and synaptic markers in a model for Attention-Deficit/Hyperactivity Disorder (ADHD). Naples High Excitability rats (NHE) and their Random Bred controls (NRB) were daily treated with LP-211 in the 5th and 6th postnatal week. One month after treatment, these rats were tested for indices of activity, non selective (NSA), selective spatial attention (SSA) and emotionality. The quantity of L-Glutamate (L-Glu), L-Aspartate (L-Asp) and L-Leucine (L-Leu), dopamine transporter (DAT), NMDAR1 subunit and CAMKIIα, were assessed in prefrontal cortex (PFC), dorsal (DS) and ventral striatum (VS), for their role in synaptic transmission, neural plasticity and information processing. Prepuberal LP-211 (at lower dose) reduced horizontal activity and (at higher dose) increased SSA, only for NHE but not in NRB rats. Prepuberal LP-211 increased, in NHE rats, L-Glu in the PFC and L-Asp in the VS (at 0.250 mg/kg dose), whereas (at 0.125 mg/kg dose) it decreased L-Glu and L-Asp in the DS. The L-Glu was decreased, at 0.125 mg/kg, only in the VS of NRB rats. The DAT levels were decreased with the 0.125 mg/kg dose (in the PFC), and increased with the 0.250 mg/kg dose (in the VS), significantly for NHE rats. The basal NMDAR1 level was higher in the PFC of NHE than NRB rats; LP-211 treatment (at 0.125 mg/kg dose) decreased NMDAR1 in the VS of NRB rats. This study represents a starting point about the impact of developmental 5-HT7-R activation on neuro-physiology of attentive processes, executive functions and their neural substrates. PMID:24709857

Contribution of N-methyl-D-aspartate receptors to attention and episodic spatial memory during senescence

PubMed Central

Guidi, Michael; Rani, Asha; Karic, Semir; Severance, Barrett; Kumar, Ashok; Foster, Thomas C.

2015-01-01

A decrease in N-methyl-D-aspartate receptor (NMDAR) function is associated with age-related cognitive impairments. However, NMDAR antagonists are prescribed for cognitive decline associated with age-related neurodegenerative disease, raising questions as to the role of NMDAR activity in cognitive function during aging. The current studies examined effects of NMDAR blockade on cognitive task that are sensitive to aging. Young and middle-age rats were trained on the five-choice serial reaction time task (5-CSRTT) and challenged with MK-801 (0.025, 0.05, and 0.1 mg/kg or vehicle). Attention deficits were apparent in middle-age and performance of young and middle-age rats was enhanced for low doses of MK-801 (0.025 and 0.05). The beneficial effects on attention were reversed by the highest dose of MK-801. Older animals exhibited a delay-dependent impairment of episodic spatial memory examined on a delayed-matching to place water maze task. Similarly, a low dose of MK-801 (0.05 mg/kg) impaired performance with increasing delay and aged animals were more susceptible to disruption by NMDAR blockade. Despite MK-801 impairment of episodic spatial memory, MK-801 had minimal effects on spatial reference memory. Our results confirm that NMDARs contribute to rapidly acquired and flexible spatial memory and support the idea that a decline in NMDAR function contributes to the age-related impairments in cognition. PMID:26234588

Inhibition of NMDARs in the Nucleus Reticularis of the Thalamus Produces Delta Frequency Bursting.

PubMed

Zhang, Yuchun; Llinas, Rodolfo R; Lisman, John E

2009-01-01

Injection of NMDAR antagonist into the thalamus can produce delta frequency EEG oscillations in the thalamocortical system. It is surprising that an antagonist of an excitatory neurotransmitter should trigger such activity, and the mechanism is unknown. One hypothesis is that the antagonist blocks excitation of GABAergic cells, thus producing disinhibition. To test this hypothesis, we investigated the effect of NMDAR antagonist (APV) on cells of the nucleus reticularis (nRT) in rat brain slices, a thalamic nucleus that can serve as a pacemaker for thalamocortical delta oscillations and that is composed entirely of GABAergic neurons. We found, unexpectedly, that nRT cells are hyperpolarized by APV. This occurs because these cells have an unusual form of NMDAR (probably NR2C) that contributes inward current at resting potential in response to ambient glutamate. The hyperpolarization produced by APV is sufficient to deinactivate T-type calcium channels, and these trigger rhythmic bursting at delta frequency. The APV-induced delta frequency bursting is abolished by dopamine D2 receptor antagonist, indicating that dopamine and NMDAR antagonist work synergistically to stimulate delta frequency bursting. Our results have significant implications concerning the electrophysiological basis of schizophrenia and bring together the NMDAR hypofunction, dopamine, and GABA theories of the disease. Our results suggest that NMDAR hypofunction and dopamine work synergistically on the GABAergic cells of the nRT to generate the delta frequency EEG oscillations, a thalamocortical dysrhythmia (TCD) in the awake state that is an established abnormality in schizophrenia.

Inhibition of NMDARs in the Nucleus Reticularis of the Thalamus Produces Delta Frequency Bursting

PubMed Central

Zhang, Yuchun; Llinas, Rodolfo R.; Lisman, John E.

2009-01-01

Injection of NMDAR antagonist into the thalamus can produce delta frequency EEG oscillations in the thalamocortical system. It is surprising that an antagonist of an excitatory neurotransmitter should trigger such activity, and the mechanism is unknown. One hypothesis is that the antagonist blocks excitation of GABAergic cells, thus producing disinhibition. To test this hypothesis, we investigated the effect of NMDAR antagonist (APV) on cells of the nucleus reticularis (nRT) in rat brain slices, a thalamic nucleus that can serve as a pacemaker for thalamocortical delta oscillations and that is composed entirely of GABAergic neurons. We found, unexpectedly, that nRT cells are hyperpolarized by APV. This occurs because these cells have an unusual form of NMDAR (probably NR2C) that contributes inward current at resting potential in response to ambient glutamate. The hyperpolarization produced by APV is sufficient to deinactivate T-type calcium channels, and these trigger rhythmic bursting at delta frequency. The APV-induced delta frequency bursting is abolished by dopamine D2 receptor antagonist, indicating that dopamine and NMDAR antagonist work synergistically to stimulate delta frequency bursting. Our results have significant implications concerning the electrophysiological basis of schizophrenia and bring together the NMDAR hypofunction, dopamine, and GABA theories of the disease. Our results suggest that NMDAR hypofunction and dopamine work synergistically on the GABAergic cells of the nRT to generate the delta frequency EEG oscillations, a thalamocortical dysrhythmia (TCD) in the awake state that is an established abnormality in schizophrenia. PMID:20057928

Contribution of N-methyl-D-aspartate receptors to attention and episodic spatial memory during senescence.

PubMed

Guidi, Michael; Rani, Asha; Karic, Semir; Severance, Barrett; Kumar, Ashok; Foster, Thomas C

2015-11-01

A decrease in N-methyl-D-aspartate receptor (NMDAR) function is associated with age-related cognitive impairments. However, NMDAR antagonists are prescribed for cognitive decline associated with age-related neurodegenerative disease, raising questions as to the role of NMDAR activity in cognitive function during aging. The current studies examined effects of NMDAR blockade on cognitive task that are sensitive to aging. Young and middle-age rats were trained on the five-choice serial reaction time task (5-CSRTT) and challenged with MK-801 (0.025, 0.05, and 0.1mg/kg or vehicle). Attention deficits were apparent in middle-age and performance of young and middle-age rats was enhanced for low doses of MK-801 (0.025 and 0.05). The beneficial effects on attention were reversed by the highest dose of MK-801. Older animals exhibited a delay-dependent impairment of episodic spatial memory examined on a delayed-matching to place water maze task. Similarly, a low dose of MK-801 (0.05mg/kg) impaired performance with increasing delay and aged animals were more susceptible to disruption by NMDAR blockade. Despite MK-801 impairment of episodic spatial memory, MK-801 had minimal effects on spatial reference memory. Our results confirm that NMDARs contribute to rapidly acquired and flexible spatial memory and support the idea that a decline in NMDAR function contributes to the age-related impairments in cognition. Copyright © 2015 Elsevier Inc. All rights reserved.

Single-dose infusion ketamine and non-ketamine N-methyl-d-aspartate receptor antagonists for unipolar and bipolar depression: a meta-analysis of efficacy, safety and time trajectories.

PubMed

Kishimoto, T; Chawla, J M; Hagi, K; Zarate, C A; Kane, J M; Bauer, M; Correll, C U

2016-05-01

Ketamine and non-ketamine N-methyl-d-aspartate receptor antagonists (NMDAR antagonists) recently demonstrated antidepressant efficacy for the treatment of refractory depression, but effect sizes, trajectories and possible class effects are unclear. We searched PubMed/PsycINFO/Web of Science/clinicaltrials.gov until 25 August 2015. Parallel-group or cross-over randomized controlled trials (RCTs) comparing single intravenous infusion of ketamine or a non-ketamine NMDAR antagonist v. placebo/pseudo-placebo in patients with major depressive disorder (MDD) and/or bipolar depression (BD) were included in the analyses. Hedges' g and risk ratios and their 95% confidence intervals (CIs) were calculated using a random-effects model. The primary outcome was depressive symptom change. Secondary outcomes included response, remission, all-cause discontinuation and adverse effects. A total of 14 RCTs (nine ketamine studies: n = 234; five non-ketamine NMDAR antagonist studies: n = 354; MDD = 554, BD = 34), lasting 10.0 ± 8.8 days, were meta-analysed. Ketamine reduced depression significantly more than placebo/pseudo-placebo beginning at 40 min, peaking at day 1 (Hedges' g = -1.00, 95% CI -1.28 to -0.73, p < 0.001), and loosing superiority by days 10-12. Non-ketamine NMDAR antagonists were superior to placebo only on days 5-8 (Hedges' g = -0.37, 95% CI -0.66 to -0.09, p = 0.01). Compared with placebo/pseudo-placebo, ketamine led to significantly greater response (40 min to day 7) and remission (80 min to days 3-5). Non-ketamine NMDAR antagonists achieved greater response at day 2 and days 3-5. All-cause discontinuation was similar between ketamine (p = 0.34) or non-ketamine NMDAR antagonists (p = 0.94) and placebo. Although some adverse effects were more common with ketamine/NMDAR antagonists than placebo, these were transient and clinically insignificant. A single infusion of ketamine, but less so of non-ketamine NMDAR antagonists, has ultra-rapid efficacy for MDD and BD, lasting for up to 1 week. Development of easy-to-administer, repeatedly given NMDAR antagonists without risk of brain toxicity is of critical importance.

Activation of NMDA receptors reduces metabotropic glutamate receptor-induced long-term depression in the nucleus accumbens via a CaMKII-dependent mechanism.

PubMed

Huang, Chiung-Chun; Hsu, Kuei-Sen

2012-12-01

Glutamate is the major excitatory neurotransmitter in the brain and exerts its actions through two distinct types of receptors, ionotropic and metabotropic glutamate receptors (mGluR). Although functional interplay between ionotropic N-methyl-d-aspartate receptors (NMDAR) and mGluR has been convincingly demonstrated in native and recombinant systems, the mechanism by which NMDAR activation leads to modulation of mGluR function has yet to be elucidated. Using whole-cell patch-clamp recordings in mouse nucleus accumbens (NAc) slices, we found that tetanic stimulation (TS) of excitatory afferents with a naturally occurring frequency (10 min at 13 Hz) reliably induces a mGluR1/5-dependent long-term depression (mGluR1/5-LTD) of excitatory synaptic transmission. Blockade of NMDAR during but not after TS showed enhanced mGluR1/5-LTD induction, which is associated with its antagonism of TS-induced calcium/calmodulin-dependent protein kinase II (CaMKII) activation. The ability of NMDAR antagonists to promote mGluR1/5-LTD induction was mimicked by a selective CaMKII inhibitor KN-62. However, the induction of mGluR1/5-LTD by bath-applied agonist (S)-3,5-dihydrophenylglycine was not affected by NMDAR blockade. We also observed that NMDAR or CaMKII blockade during TS significantly blunted TS-induced increased serine/threonine phosphorylation of the scaffold protein Homer1b/c and resulted in an increased interaction of mGluR5 with the Homer1b/c. These results indicate that synaptically released glutamate during TS of excitatory afferents can activate both NMDAR and mGluR1/5 in NAc neurons concomitantly and that activation of NMDAR may stimulate CaMKII-mediated phosphorylation of Homer1b/c and impair the interaction between mGluR5 and Homer1b/c, thereby attenuating mGluR1/5-LTD induction. This study provides a novel molecular mechanism by which NMDAR could regulate mGluR5 function. Copyright © 2012 Elsevier Ltd. All rights reserved.

Frequent rhabdomyolysis in anti-NMDA receptor encephalitis.

PubMed

Lim, Jung-Ah; Lee, Soon-Tae; Kim, Tae-Joon; Moon, Jangsup; Sunwoo, Jun-Sang; Byun, Jung-Ick; Jung, Keun-Hwa; Jung, Ki-Young; Chu, Kon; Lee, Sang Kun

2016-09-15

The aim of this study was to analyze the clinical presentation and provocation factors of rhabdomyolysis in anti-NMDAR encephalitis. Among the 16 patients with anti-NMDAR encephalitis in our institutional cohort, nine patients had elevated CK enzyme levels and clinical evidence of rhabdomyolysis. Rhabdomyolysis was more frequent after immunotherapy. The use of dopamine receptor blocker (DRB) increased the risk of rhabdomyolysis. None of the patients without rhabdomyolysis received DRBs. Rhabdomyolysis is a frequent complication in anti-NMDAR encephalitis and more common after immunotherapy and the use of DRBs increases the risk. Therefore, DRBs should be administered carefully in patients with anti-NMDAR encephalitis. Copyright © 2016 Elsevier B.V. All rights reserved.

Target-specific expression of presynaptic NMDA receptors in neocortical microcircuits.

PubMed

Buchanan, Katherine A; Blackman, Arne V; Moreau, Alexandre W; Elgar, Dale; Costa, Rui P; Lalanne, Txomin; Tudor Jones, Adam A; Oyrer, Julia; Sjöström, P Jesper

2012-08-09

Traditionally, NMDA receptors are located postsynaptically; yet, putatively presynaptic NMDA receptors (preNMDARs) have been reported. Although implicated in controlling synaptic plasticity, their function is not well understood and their expression patterns are debated. We demonstrate that, in layer 5 of developing mouse visual cortex, preNMDARs specifically control synaptic transmission at pyramidal cell inputs to other pyramidal cells and to Martinotti cells, while leaving those to basket cells unaffected. We also reveal a type of interneuron that mediates ascending inhibition. In agreement with synapse-specific expression, we find preNMDAR-mediated calcium signals in a subset of pyramidal cell terminals. A tuned network model predicts that preNMDARs specifically reroute information flow in local circuits during high-frequency firing, in particular by impacting frequency-dependent disynaptic inhibition mediated by Martinotti cells, a finding that we experimentally verify. We conclude that postsynaptic cell type determines presynaptic terminal molecular identity and that preNMDARs govern information processing in neocortical columns. Copyright © 2012 Elsevier Inc. All rights reserved.

Ketamine blocks bursting in the lateral habenula to rapidly relieve depression.

PubMed

Yang, Yan; Cui, Yihui; Sang, Kangning; Dong, Yiyan; Ni, Zheyi; Ma, Shuangshuang; Hu, Hailan

2018-02-14

The N-methyl-d-aspartate receptor (NMDAR) antagonist ketamine has attracted enormous interest in mental health research owing to its rapid antidepressant actions, but its mechanism of action has remained elusive. Here we show that blockade of NMDAR-dependent bursting activity in the 'anti-reward center', the lateral habenula (LHb), mediates the rapid antidepressant actions of ketamine in rat and mouse models of depression. LHb neurons show a significant increase in burst activity and theta-band synchronization in depressive-like animals, which is reversed by ketamine. Burst-evoking photostimulation of LHb drives behavioural despair and anhedonia. Pharmacology and modelling experiments reveal that LHb bursting requires both NMDARs and low-voltage-sensitive T-type calcium channels (T-VSCCs). Furthermore, local blockade of NMDAR or T-VSCCs in the LHb is sufficient to induce rapid antidepressant effects. Our results suggest a simple model whereby ketamine quickly elevates mood by blocking NMDAR-dependent bursting activity of LHb neurons to disinhibit downstream monoaminergic reward centres, and provide a framework for developing new rapid-acting antidepressants.

Role of NMDA Receptor-Mediated Glutamatergic Signaling in Chronic and Acute Neuropathologies

PubMed Central

2016-01-01

N-Methyl-D-aspartate receptors (NMDARs) have two opposing roles in the brain. On the one hand, NMDARs control critical events in the formation and development of synaptic organization and synaptic plasticity. On the other hand, the overactivation of NMDARs can promote neuronal death in neuropathological conditions. Ca2+ influx acts as a primary modulator after NMDAR channel activation. An imbalance in Ca2+ homeostasis is associated with several neurological diseases including schizophrenia, Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. These chronic conditions have a lengthy progression depending on internal and external factors. External factors such as acute episodes of brain damage are associated with an earlier onset of several of these chronic mental conditions. Here, we will review some of the current evidence of how traumatic brain injury can hasten the onset of several neurological conditions, focusing on the role of NMDAR distribution and the functional consequences in calcium homeostasis associated with synaptic dysfunction and neuronal death present in this group of chronic diseases. PMID:27630777

Non-inflammatory cerebrospinal fluid delays the diagnosis and start of immunotherapy in anti-NMDAR encephalitis.

PubMed

Espinola-Nadurille, Mariana; Bautista-Gomez, Paola; Flores, Jose; Rivas-Alonso, Veronica; Perez-Esparza, Rodrigo; Solís-Vivanco, Rodolfo; Vargas-Cañas, Steven

2018-01-01

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is a form of autoimmune encephalopathy that presents with a wide variety of symptoms, including neuropsychiatric manifestations. The authors' aim for this study was to analyze the results of paraclinical studies of patients with a diagnosis of anti-NMDAR encephalitis and the association between symptom onset and diagnosis, and start of immunotherapy. Retrospective data of 29 patients with anti-NMDAR encephalitis were gathered and analyzed. Abnormal EEG was found in 27 patients (93.1%), whereas MRI was abnormal in 19 patients (65.5%). In contrast, an inflammatory pattern on CSF analysis was found in only 13 patients (44.8%). The absence of pleocytosis or increased proteins in the CSF was associated with a longer time from symptom onset to diagnosis and treatment (p = 0.003). The authors conclude that noninflammatory CSF may delay the correct diagnosis and start of immunotherapy in anti-NMDAR encephalitis. In the presence of suggestive clinical features, extensive studies including EEG are recommended.

Early Growth Response 1 (Egr-1) Regulates N-Methyl-d-aspartate Receptor (NMDAR)-dependent Transcription of PSD-95 and α-Amino-3-hydroxy-5-methyl-4-isoxazole Propionic Acid Receptor (AMPAR) Trafficking in Hippocampal Primary Neurons*

PubMed Central

Qin, Xike; Jiang, Yongjun; Tse, Yiu Chung; Wang, Yunling; Wong, Tak Pan; Paudel, Hemant K.

2015-01-01

The N-methyl-d-aspartate receptor (NMDAR) controls synaptic plasticity and memory function and is one of the major inducers of transcription factor Egr-1 in the hippocampus. However, how Egr-1 mediates the NMDAR signal in neurons has remained unclear. Here, we show that the hippocampus of mice lacking Egr-1 displays electrophysiology properties and ultrastructure that are similar to mice overexpressing PSD-95, a major scaffolding protein of postsynaptic density involved in synapse formation, synaptic plasticity, and synaptic targeting of AMPA receptors (AMPARs), which mediate the vast majority of excitatory transmission in the CNS. We demonstrate that Egr-1 is a transcription repressor of the PSD-95 gene and is recruited to the PSD-95 promoter in response to NMDAR activation. Knockdown of Egr-1 in rat hippocampal primary neurons blocks NMDAR-induced PSD-95 down-regulation and AMPAR endocytosis. Likewise, overexpression of Egr-1 in rat hippocampal primary neurons causes reduction in PSD-95 protein level and promotes AMPAR endocytosis. Our data indicate that Egr-1 is involved in NMDAR-mediated PSD-95 down-regulation and AMPAR endocytosis, a process important in the expression of long term depression. PMID:26475861

N-Methyl-D-aspartate receptor antibody could be a cause of catatonic symptoms in psychiatric patients: case reports and methods for detection.

PubMed

Tsutsui, Ko; Kanbayashi, Takashi; Takaki, Manabu; Omori, Yuki; Imai, Yumiko; Nishino, Seiji; Tanaka, Keiko; Shimizu, Tetsuo

2017-01-01

The symptoms of catatonia have been reported to be similar to the initial symptoms of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. Subsequently, this autoimmune limbic encephalitis has been noticed by many psychiatrists. For a differential diagnosis of catatonic state, it is important to detect anti-NMDAR encephalitis. This encephalitis is expected to be in remission by early detection and treatment. We should be more cautious about catatonic symptoms of schizophrenia. When a patient is suspected of having encephalitis, we should screen for anti-NMDAR antibodies in cerebrospinal fluid samples using a cell-based assay. We describe the methods of NMDAR antibody detection and the etiology of this encephalitis with case reports. Two representative cases with catatonia and non-catatonia (brief psychotic disorder) were reported. Schizophrenia is a general, heterogeneous, and complicated disorder, and its pathophysiology is unknown. There is an established evidence of NMDAR hypofunction, which is the functional disconnection of the central component; this is one of the most recognized models for schizophrenia. Furthermore, it is said that autoimmune mechanisms have been involved, at least in subgroups of schizophrenia patients. Further study of anti-NMDAR antibody and its related encephalitis would give essential clues for the research of schizophrenia, catatonia, and atypical psychosis.

Hippocampal protein kinase D1 is necessary for DHPG-induced learning and memory impairments in rats

PubMed Central

Groveman, Bradley R.; Carrier, Nicole; Qiao, Haifa; Fang, Xiao-Qian; Wang, Hui; Xin, Wenkuan; Jiang, Xing-Hong; Salter, Michael W.; Ding, Xin-Sheng; Kabbaj, Mohamed

2018-01-01

Background Understanding molecular mechanisms underlying the induction of learning and memory impairments remains a challenge. Recent investigations have shown that the activation of group I mGluRs (mGluR1 and mGluR5) in cultured hippocampal neurons by application of (S)-3,5-Dihydroxyphenylglycine (DHPG) causes the regulated internalization of N-methyl-D-aspartate receptors (NMDARs), which subsequently activates protein kinase D1 (PKD1). Through phosphorylating the C-terminals of the NMDAR GluN2 subunits, PKD1 down-regulates the activity of remaining (non-internalized) surface NMDARs. The knockdown of PKD1 does not affect the DHPG-induced inhibition of AMPA receptor-mediated miniature excitatory post-synaptic currents (mEPSCs) but prevents the DHPG-induced inhibition of NMDAR-mediated mEPSCs in vitro. Thus, we investigated the in vivo effects of bilateral infusions of DHPG into the hippocampal CA1 area of rats in the Morris water maze (MWM) and the novel object discrimination (NOD) tests. Methods A total of 300 adult male Sprague Dawley rats (250–280 g) were used for behavioral tests. One hundred ninety four were used in MWM test and the other 106 rats in the NOD test. Following one week of habituation to the vivarium, rats were bilaterally implanted under deep anesthesia with cannulas aimed at the CA1 area of the hippocampus (CA1 coordinates in mm from Bregma: AP -3.14; lateral +/-2; DV -3.0). Through implanted cannulas artificial cerebrospinal fluid (ACSF), the group1 mGluR antagonist 6-Methyl-2-(phenylethynyl)pyridine (MPEP), the dynamin-dependent internalization inhibitor Dynasore, or the PKD1 inhibitor CID755673 were infused into the bilateral hippocampal CA1 areas (2 μL per side, over 5 min). The effects of these infusions and the effects of PKD1 knockdown were examined in MWM or NOD test. Results DHPG infusion increased the latency to reach the platform in the MWM test and reduced the preference for the novel object in the NOD task. We found that the DHPG effects were dose-dependent and could be maintained for up to 2 days. Notably, these effects could be prevented by pre-infusion of the group1 mGluR antagonist MPEP, the dynamin-dependent internalization inhibitor Dynasore, the PKD1 inhibitor CID755673, or by PKD1 knockdown in the hippocampal CA1 area. Conclusion Altogether, these findings provide direct evidence that PKD1-mediated signaling may play a critical role in the induction of learning and memory impairments by DHPG infusion into the hippocampal CA1 area. PMID:29614089

Age-related changes in functional postsynaptic nicotinic acetylcholine receptor subunits in neurons of the laterodorsal tegmental nucleus, a nucleus important in drug addiction.

PubMed

Christensen, Mark H; Kohlmeier, Kristi A

2016-03-01

The earlier an individual initiates cigarette smoking, the higher the likelihood of development of dependency to nicotine, the addictive ingredient in cigarettes. One possible mechanism underlying this higher addiction liability is an ontogenetically differential cellular response induced by nicotine in neurons mediating the reinforcing or euphoric effects of this drug, which could arise from age-related differences in the composition of nicotinic acetylcholine receptor (nAChR) subunits. In the current study, we examined whether the subunit composition of nAChRs differed between neurons within the laterodorsal tegmentum (LDT), a nucleus importantly involved in drug addiction associated behaviours, across two periods of ontogeny in which nicotine-mediated excitatory responses were shown to depend on age. To this end, whole-cell patch-clamp recordings in mouse brain slices from identified LDT neurons, in combination with nAChR subunit-specific receptor antagonists, were conducted. Comparison of the contribution of different nAChR subunits to acetylcholine (ACh)-induced inward currents indicated that the contributions of the β2 and/or β4 and α7 nAChR subunits alter across age. Taken together, we conclude that across a limited ontogenetic period, there is plasticity in the subunit composition of nAChRs in LDT neurons. In addition, our data indicate, for the first time, functional presence of α6 nAChR subunits in LDT neurons within the age ranges studied. Changes in subunit composition of nAChRs across ontogeny could contribute to the age-related differential excitability induced by nicotine. Differences in the subunit composition of nAChRs within the LDT would be expected to contribute to ontogenetic-dependent outflow from the LDT to target regions, which include reward-related circuitry. © 2014 Society for the Study of Addiction.

Ionotropic glutamate receptor antagonists and cancer therapy: time to think out of the box?

PubMed

Ribeiro, Mariana P C; Custódio, José B A; Santos, Armanda E

2017-02-01

Glutamate has a trophic function in the development of the central nervous system, regulating the proliferation and migration of neuronal progenitors. The resemblance between neuronal embryonic and tumor cells has paved the way for the investigation of the effects of glutamate on tumor cells. Indeed, tumor cells derived from neuronal tissue express ionotropic glutamate receptor (iGluRs) subunits and iGluR antagonists decrease cell proliferation. Likewise, iGluRs subunits are expressed in several peripheral cancer cells and blockade of the N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) ionotropic glutamate receptor subtypes decreases their proliferation and migration. Although these mechanisms are still being investigated, the inhibition of the mitogen-activated protein kinase pathway was shown to play a key role in the antiproliferative activity of iGluR antagonists. Importantly, MK-801, a NMDAR channel blocker, was effective and well tolerated in animal models of melanoma, lung, and breast cancers, suggesting that the blockade of iGluR signaling may represent a new strategy for cancer treatment. In this review, we focus on the significance of NMDA and AMPA receptor expression in tumor cells, as well as possible therapeutic strategies targeting these receptors.

Tracking single membrane targets of human autoantibodies using single nanoparticle imaging.

PubMed

Jézéquel, Julie; Dupuis, Julien P; Maingret, François; Groc, Laurent

2018-04-21

Over the past decade, an increasing number of neurological and neuropsychiatric diseases have been associated with the expression of autoantibodies directed against neuronal targets, including neurotransmitter receptors. Although cell-based assays are routinely used in clinics to detect the presence of immunoglobulins, such tests often provide heterogeneous outcomes due to their limited sensitivity, especially at low titers. Thus, there is an urging need for new methods allowing the detection of autoantibodies in seropositive patients that cannot always be clinically distinguished from seronegative ones. Here we make a case for single nanoparticle imaging approaches as a highly sensitive antibody detection assay. Through high-affinity interactions between functionalized nanoparticles and autoantibodies that recognize extracellular domains of membrane neuronal targets, single nanoparticle imaging allows a live surface staining of transmembrane proteins and gives access to their surface dynamics. We show here that this method is well-suited to detect low titers of purified immunoglobulin G (IgG) from first-episode psychotic patients and demonstrate that these IgG target glutamatergic N-Methyl-d-Aspartate receptors (NMDAR) in live hippocampal neurons. The molecular behaviors of targeted membrane receptors were indistinguishable from those of endogenous GluN1 NMDAR subunit and were virtually independent of the IgG concentration present in the sample contrary to classical cell-based assays. Single nanoparticle imaging emerges as a real-time sensitive method to detect IgG directed against neuronal surface proteins, which could be used as an additional step to rule out ambiguous seropositivity diagnoses. Copyright © 2018 Elsevier B.V. All rights reserved.

STRIATAL-ENRICHED PROTEIN TYROSINE PHOSPHATASE (STEP) KNOCKOUT MICE HAVE ENHANCED HIPPOCAMPAL MEMORY

PubMed Central

Venkitaramani, Deepa V.; Moura, Paula J.; Picciotto, Marina R.; Lombroso, Paul J.

2011-01-01

STEP is a brain-specific phosphatase that opposes synaptic strengthening by the regulation of key synaptic signaling proteins. Previous studies suggest a possible role for STriatal-Enriched protein tyrosine Phosphatase (STEP) in learning and memory. To demonstrate the functional importance of STEP in learning and memory, we generated STEP knockout (KO) mice and examined the effect of deletion of STEP on behavioral performance, as well as the phosphorylation and expression of its substrates. Here we report that loss of STEP leads to significantly enhanced performance in hippocampal-dependent learning and memory tasks. In addition, STEP KO mice displayed greater dominance behavior, although they were normal in their motivation, motor coordination, visual acuity and social interactions. STEP KO mice displayed enhanced tyrosine phosphorylation of extracellular-signal regulated kinase 1/2 (ERK1/2), the NR2B subunit of the N-methyl-D-aspartate receptor (NMDAR), Proline-rich tyrosine kinase (Pyk2), as well as an increased phosphorylation of ERK1/2 substrates. Concomitant to the increased phosphorylation of NR2B, synaptosomal expression of NR1/NR2B NMDARs was increased in STEP KO mice, as was the GluR1/GluR2 containing α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptors (AMPAR), providing a potential molecular mechanism for the improved cognitive performance. The data support a role for STEP in the regulation of synaptic strengthening. The absence of STEP improves cognitive performance, and may do so by the regulation of downstream effectors necessary for synaptic transmission. PMID:21501258

Differential regulation of NMDA receptors by d-serine and glycine in mammalian spinal locomotor networks

PubMed Central

Acton, David

2017-01-01

Activation of N-methyl-d-aspartate receptors (NMDARs) requires the binding of a coagonist, either d-serine or glycine, in addition to glutamate. Changes in occupancy of the coagonist binding site are proposed to modulate neural networks including those controlling swimming in frog tadpoles. Here, we characterize regulation of the NMDAR coagonist binding site in mammalian spinal locomotor networks. Blockade of NMDARs by d(−)-2-amino-5-phosphonopentanoic acid (d-APV) or 5,7-dichlorokynurenic acid reduced the frequency and amplitude of pharmacologically induced locomotor-related activity recorded from the ventral roots of spinal-cord preparations from neonatal mice. Furthermore, d-APV abolished synchronous activity induced by blockade of inhibitory transmission. These results demonstrate an important role for NMDARs in murine locomotor networks. Bath-applied d-serine enhanced the frequency of locomotor-related but not disinhibited bursting, indicating that coagonist binding sites are saturated during the latter but not the former mode of activity. Depletion of endogenous d-serine by d-amino acid oxidase or the serine-racemase inhibitor erythro-β-hydroxy-l-aspartic acid (HOAsp) increased the frequency of locomotor-related activity, whereas application of l-serine to enhance endogenous d-serine synthesis reduced burst frequency, suggesting a requirement for d-serine at a subset of synapses onto inhibitory interneurons. Consistent with this, HOAsp was ineffective during disinhibited activity. Bath-applied glycine (1–100 µM) failed to alter locomotor-related activity, whereas ALX 5407, a selective inhibitor of glycine transporter-1 (GlyT1), enhanced burst frequency, supporting a role for GlyT1 in NMDAR regulation. Together these findings indicate activity-dependent and synapse-specific regulation of the coagonist binding site within spinal locomotor networks, illustrating the importance of NMDAR regulation in shaping motor output. NEW & NOTEWORTHY We provide evidence that NMDARs within murine spinal locomotor networks determine the frequency and amplitude of ongoing locomotor-related activity in vitro and that NMDARs are regulated by d-serine and glycine in a synapse-specific and activity-dependent manner. In addition, glycine transporter-1 is shown to be an important regulator of NMDARs during locomotor-related activity. These results show how excitatory transmission can be tuned to diversify the output repertoire of spinal locomotor networks in mammals. PMID:28202572

Parvalbumin Cell Ablation of NMDA-R1 Causes Increased Resting Network Excitability with Associated Social and Self-Care Deficits

PubMed Central

Billingslea, Eddie N; Tatard-Leitman, Valerie M; Anguiano, Jaynie; Jutzeler, Catherine R; Suh, Jimmy; Saunders, John A; Morita, Susumu; Featherstone, Robert E; Ortinski, Pavel I; Gandal, Michael J; Lin, Robert; Liang, Yuling; Gur, Raquel E; Carlson, Gregory C; Hahn, Chang-Gyu; Siegel, Steven J

2014-01-01

NMDA-receptor (NMDAR) hypofunction is strongly implicated in the pathophysiology of schizophrenia. Several convergent lines of evidence suggest that net excitation propagated by impaired NMDAR signaling on GABAergic interneurons may be of particular interest in mediating several aspects of schizophrenia. However, it is unclear which behavioral domains are governed by a net increase of excitation and whether modulating downstream GABAergic signaling can reverse neural and thus behavioral deficits. The current study determines the selective contributions of NMDAR dysfunction on PV-containing interneurons to electrophysiological, cognitive, and negative-symptom-related behavioral phenotypes of schizophrenia using mice with a PVcre-NR1flox-driven ablation of NR1 on PV-containing interneurons. In addition, we assessed the efficacy of one agent that directly modulates GABAergic signaling (baclofen) and one agent that indirectly modifies NMDAR-mediated signaling through antagonism of mGluR5 receptors (2-methyl-6-(phenylethynyl) pyridine (MPEP)). The data indicate that loss of NMDAR function on PV interneurons impairs self-care and sociability while increasing N1 latency and baseline gamma power, and reducing induction and maintenance of long-term potentiation. Baclofen normalized baseline gamma power without corresponding effects on behavior. MPEP further increased N1 latency and reduced social behavior in PVcre/NR1+/+ mice. These two indices were negatively correlated before and following MPEP such that as N1 latency increases, sociability decreases. This finding suggests a predictive role for N1 latency with respect to social function. Although previous data suggest that MPEP may be beneficial for core features of autism spectrum disorders, current data suggest that such effects require intact function of NMDAR on PV interneurons. PMID:24525709

Early Growth Response 1 (Egr-1) Regulates N-Methyl-d-aspartate Receptor (NMDAR)-dependent Transcription of PSD-95 and α-Amino-3-hydroxy-5-methyl-4-isoxazole Propionic Acid Receptor (AMPAR) Trafficking in Hippocampal Primary Neurons.

PubMed

Qin, Xike; Jiang, Yongjun; Tse, Yiu Chung; Wang, Yunling; Wong, Tak Pan; Paudel, Hemant K

2015-12-04

The N-methyl-d-aspartate receptor (NMDAR) controls synaptic plasticity and memory function and is one of the major inducers of transcription factor Egr-1 in the hippocampus. However, how Egr-1 mediates the NMDAR signal in neurons has remained unclear. Here, we show that the hippocampus of mice lacking Egr-1 displays electrophysiology properties and ultrastructure that are similar to mice overexpressing PSD-95, a major scaffolding protein of postsynaptic density involved in synapse formation, synaptic plasticity, and synaptic targeting of AMPA receptors (AMPARs), which mediate the vast majority of excitatory transmission in the CNS. We demonstrate that Egr-1 is a transcription repressor of the PSD-95 gene and is recruited to the PSD-95 promoter in response to NMDAR activation. Knockdown of Egr-1 in rat hippocampal primary neurons blocks NMDAR-induced PSD-95 down-regulation and AMPAR endocytosis. Likewise, overexpression of Egr-1 in rat hippocampal primary neurons causes reduction in PSD-95 protein level and promotes AMPAR endocytosis. Our data indicate that Egr-1 is involved in NMDAR-mediated PSD-95 down-regulation and AMPAR endocytosis, a process important in the expression of long term depression. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

MHC class I immune proteins are critical for hippocampus-dependent memory and gate NMDAR-dependent hippocampal long-term depression

PubMed Central

Nelson, P. Austin; Sage, Jennifer R.; Wood, Suzanne C.; Davenport, Christopher M.; Anagnostaras, Stephan G.; Boulanger, Lisa M.

2013-01-01

Memory impairment is a common feature of conditions that involve changes in inflammatory signaling in the brain, including traumatic brain injury, infection, neurodegenerative disorders, and normal aging. However, the causal importance of inflammatory mediators in cognitive impairments in these conditions remains unclear. Here we show that specific immune proteins, members of the major histocompatibility complex class I (MHC class I), are essential for normal hippocampus-dependent memory, and are specifically required for NMDAR-dependent forms of long-term depression (LTD) in the healthy adult hippocampus. In β2m−/−TAP−/−mice, which lack stable cell-surface expression of most MHC class I proteins, NMDAR-dependent LTD in area CA1 of adult hippocampus is abolished, while NMDAR-independent forms of potentiation, facilitation, and depression are unaffected. Altered NMDAR-dependent synaptic plasticity in the hippocampus of β2m−/−TAP−/−mice is accompanied by pervasive deficits in hippocampus-dependent memory, including contextual fear memory, object recognition memory, and social recognition memory. Thus normal MHC class I expression is essential for NMDAR-dependent hippocampal synaptic depression and hippocampus-dependent memory. These results suggest that changes in MHC class I expression could be an unexpected cause of disrupted synaptic plasticity and cognitive deficits in the aging, damaged, and diseased brain. PMID:23959708

Development of schemas revealed by prior experience and NMDA receptor knock-out

PubMed Central

Dragoi, George; Tonegawa, Susumu

2013-01-01

Prior experience accelerates acquisition of novel, related information through processes like assimilation into mental schemas, but the underlying neuronal mechanisms are poorly understood. We investigated the roles that prior experience and hippocampal CA3 N-Methyl-D-aspartate receptor (NMDAR)-dependent synaptic plasticity play in CA1 place cell sequence encoding and learning during novel spatial experiences. We found that specific representations of de novo experiences on linear environments were formed on a framework of pre configured network activity expressed in the preceding sleep and were rapidly, flexibly adjusted via NMDAR-dependent activity. This prior experience accelerated encoding of subsequent experiences on contiguous or isolated novel tracks, significantly decreasing their NMDAR-dependence. Similarly, de novo learning of an alternation task was facilitated by CA3 NMDARs; this experience accelerated subsequent learning of related tasks, independent of CA3 NMDARs, consistent with a schema-based learning. These results reveal the existence of distinct neuronal encoding schemes which could explain why hippocampal dysfunction results in anterograde amnesia while sparing recollection of old, schema-based memories. DOI: http://dx.doi.org/10.7554/eLife.01326.001 PMID:24327561

Computationally Discovered Potentiating Role of Glycans on NMDA Receptors

NASA Astrophysics Data System (ADS)

Sinitskiy, Anton V.; Stanley, Nathaniel H.; Hackos, David H.; Hanson, Jesse E.; Sellers, Benjamin D.; Pande, Vijay S.

2017-04-01

N-methyl-D-aspartate receptors (NMDARs) are glycoproteins in the brain central to learning and memory. The effects of glycosylation on the structure and dynamics of NMDARs are largely unknown. In this work, we use extensive molecular dynamics simulations of GluN1 and GluN2B ligand binding domains (LBDs) of NMDARs to investigate these effects. Our simulations predict that intra-domain interactions involving the glycan attached to residue GluN1-N440 stabilize closed-clamshell conformations of the GluN1 LBD. The glycan on GluN2B-N688 shows a similar, though weaker, effect. Based on these results, and assuming the transferability of the results of LBD simulations to the full receptor, we predict that glycans at GluN1-N440 might play a potentiator role in NMDARs. To validate this prediction, we perform electrophysiological analysis of full-length NMDARs with a glycosylation-preventing GluN1-N440Q mutation, and demonstrate an increase in the glycine EC50 value. Overall, our results suggest an intramolecular potentiating role of glycans on NMDA receptors.

N-methyl-d-aspartate (NMDA) receptor antibodies encephalitis mimicking an autistic regression.

PubMed

Hacohen, Yael; Wright, Sukhvir; Gadian, Jonathan; Vincent, Angela; Lim, Ming; Wassmer, Evangeline; Lin, Jean-Pierre

2016-10-01

Expressive dysphasia and mutism are common clinical features in children and adults with N-methyl-d-aspartate receptor antibodies (NMDAR-Ab) encephalitis, and are likely to result from NMDAR hypofunction. A prodromal loss of social and communication skills can typify that of an autistic regression, particularly when presenting under the age of 3 years. Here we describe two toddlers who presented with developmental regression, particularly of their social communication skills, mimicking an autistic regression, who were found to have NMDAR-Ab in the serum and cerebrospinal fluid. Although both patients had some other neurological features, they were subtle, which resulted in delayed diagnosis of NMDAR-Ab encephalitis. Importantly, immunotherapy was beneficial in both patients, with significant improvement of their language skills and behaviour. © 2016 Mac Keith Press.

NMDA receptor as a newly identified member of the metabotropic glutamate receptor family: clinical implications for neurodegenerative diseases.

PubMed

Chung, ChiHye

2013-08-01

Recent reports have proposed a novel function for the N-methyl-D-aspartate (NMDA) receptor (NMDAR), a well-known excitatory, ionotropic receptor. A series of observations employing pharmacological techniques has proposed that upon ligand binding, this ionotropic receptor can actually function via signaling cascades independent of traditional ionotropic action. Moreover, the "metabotropic" action of NMDARs is suggested to mediate a form of synaptic plasticity, namely long-term synaptic depression (LTD), which shares cellular mechanisms with the synaptic deficits observed in Alzheimer's disease. Given that a growing body of clinical and preclinical evidence strongly recommends NMDAR antagonists for their therapeutic potentials and advantages in a variety of diseases, further investigation into their molecular and cellular mechanisms is required to better understand the "metabotropic" action of NMDARs.

NMDA Receptor as a Newly Identified Member of the Metabotropic Glutamate Receptor Family: Clinical Implications for Neurodegenerative Diseases

PubMed Central

Chung, ChiHye

2013-01-01

Recent reports have proposed a novel function for the N-methyl-d-aspartate (NMDA) receptor (NMDAR), a well-known excitatory, ionotropic receptor. A series of observations employing pharmacological techniques has proposed that upon ligand binding, this ionotropic receptor can actually function via signaling cascades independent of traditional ionotropic action. Moreover, the “metabotropic” action of NMDARs is suggested to mediate a form of synaptic plasticity, namely long-term synaptic depression (LTD), which shares cellular mechanisms with the synaptic deficits observed in Alzheimer’s disease. Given that a growing body of clinical and preclinical evidence strongly recommends NMDAR antagonists for their therapeutic potentials and advantages in a variety of diseases, further investigation into their molecular and cellular mechanisms is required to better understand the “metabotropic” action of NMDARs. PMID:23740429

Memantine for the Treatment of Dementia: A Review on its Current and Future Applications

PubMed Central

Folch, Jaume; Busquets, Oriol; Ettcheto, Miren; Sánchez-López, Elena; Castro-Torres, Ruben Dario; Verdaguer, Ester; Garcia, Maria Luisa; Olloquequi, Jordi; Casadesús, Gemma; Beas-Zarate, Carlos; Pelegri, Carme; Vilaplana, Jordi; Auladell, Carme; Camins, Antoni

2017-01-01

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by the presence in the brain of extracellular amyloid-β protein (Aβ) and intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein. The N-Methyl-D-aspartate receptors (NMDAR), ionotropic glutamate receptor, are essential for processes like learning and memory. An excessive activation of NMDARs has been associated with neuronal loss. The discovery of extrasynaptic NMDARs provided a rational and physiological explanation between physiological and excitotoxic actions of glutamate. Memantine (MEM), an antagonist of extrasynaptic NMDAR, is currently used for the treatment of AD jointly with acetylcholinesterase inhibitors. It has been demonstrated that MEM preferentially prevents the excessive continuous extrasynaptic NMDAR disease activation and therefore prevents neuronal cell death induced by excitotoxicity without disrupting physiological synaptic activity. The problem is that MEM has shown no clear positive effects in clinical applications while, in preclinical stages, had very promising results. The data in preclinical studies suggests that MEM has a positive impact on improving AD brain neuropathology, as well as in preventing Aβ production, aggregation, or downstream neurotoxic consequences, in part through the blockade of extrasynaptic NMDAR. Thus, the focus of this review is primarily to discuss the efficacy of MEM in preclinical models of AD, consider possible combinations of this drug with others, and then evaluate possible reasons for its lack of efficacy in clinical trials. Finally, applications in other pathologies are also considered. PMID:29254093

Molecular and neurochemical biomarkers in Arctic beluga whales (Delphinapterus leucas) were correlated to brain mercury and selenium concentrations.

PubMed

Ostertag, Sonja K; Shaw, Alyssa C; Basu, Niladri; Chan, Hing Man

2014-10-07

Mercury (Hg) concentrations have increased in western Arctic beluga whales (Delphinapterus leucas) since the industrial revolution. Methylmercruy (MeHg) is a known neurotoxicant, yet little is known about the risk of exposure for beluga whales. Selenium (Se) has been linked to demethylation of MeHg in cetaceans, but its role in attenuating Hg toxicity in beluga whales is poorly understood. The objective of this study is to explore relationships between Hg and Se concentrations and neurochemical biomarkers in different brain regions of beluga whales in order to assess potential neurotoxicological risk of Hg exposure in this population. Brain tissue was sampled from hunter-harvested beluga whales from the western Canadian Arctic in 2008 and 2010. Neurochemical and molecular biomarkers were measured with radioligand binding assays and quantitative PCR, respectively. Total Hg (HgT) concentration ranged from 2.6-113 mg kg(-1) dw in temporal cortex. Gamma-amminobutyric acid type A receptor (GABAA-R) binding in the cerebellum was negatively associated with HgT, MeHg and total Se (SeT) concentrations (p ≤ 0.05). The expression of mRNA for GABAA-R subunit α2 was negatively associated with HgT and MeHg (p ≤ 0.05). Furthermore, GABAA-R binding was positively correlated to mRNA expression for GABAA-R α2 subunit, and negatively correlated to the expression of mRNA for GABAA-R α4 subunit (p ≤ 0.05). The expression of N-methyl-d-aspartate receptor (NMDA-R) subunit 2b mRNA expression was negatively associated with iHglabile concentration in the cerebellum (p ≤ 0.05). Variation of molecular and/or biochemical components of the GABAergic and glutamatergic signaling pathways were associated with MeHg exposure in beluga whales. Our results show that MeHg exposure is associated with neurochemical variation in the cerebellum of beluga whales and Se may partially protect from MeHg-associated neurotoxicity.

The NMDA Receptor Subunit NR2b: Effects on LH Release and GnRH Gene Expression in Young and Middle-aged Female Rats, with Modulation by Estradiol

PubMed Central

Maffucci, Jacqueline A.; Walker, Deena M.; Ikegami, Aiko; Woller, Michael J.; Gore, Andrea C.

2008-01-01

The loss of reproductive capacity during aging involves changes in the neural regulation of the hypothalamic gonadotropin-releasing hormone (GnRH) neurons controlling reproduction. This neuronal circuitry includes glutamate receptors on GnRH neurons. Previously, we reported an increase in the expression of the NR2b subunit protein of the NMDA receptor on GnRH neurons in middle-aged compared to young female rats. Here, we examined the functional implications of the NR2b subunit on the onset of reproductive aging, using an NR2b-specific antagonist ifenprodil. Young (3–5 mos.) and middle-aged (10–13 mos.) female rats were ovariectomized (OVX), 17β-estradiol (E2) or vehicle (cholesterol) treated, and implanted with a jugular catheter. Serial blood sampling was undertaken every 10 minutes for 4 hours, with ifenprodil (10mg/kg) or vehicle injected (i.p.) after one hour of baseline sampling. The pulsatile release of pituitary LH and levels of GnRH mRNA in hypothalamus were quantified as indices of the reproductive axis. Our results showed effects of ifenprodil on both endpoints. In OVX rats given cholesterol, neither age nor ifenprodil had any effects on LH release. In E2-treated rats, aging was associated with significant decreases in pulsatile LH release. Additionally, ifenprodil stimulated parameters of pulsatile LH release in both young and middle-aged animals. Ifenprodil had few effects on GnRH mRNA; the only significant effect of ifenprodil was found in the middle-aged, cholesterol group. Together, these findings support a role for the NR2b subunit of the NMDAR in GnRH/LH regulation. Because most of these effects were exhibited on pituitary LH release in the absence of a concomitant change in GnRH gene expression, it is likely that NMDA receptors containing the NR2b subunit plays a role in GnRH-induced LH release, independent of de novo GnRH gene expression. PMID:18025808

Neuromorphic Implementation of Attractor Dynamics in a Two-Variable Winner-Take-All Circuit with NMDARs: A Simulation Study

PubMed Central

You, Hongzhi; Wang, Da-Hui

2017-01-01

Neural networks configured with winner-take-all (WTA) competition and N-methyl-D-aspartate receptor (NMDAR)-mediated synaptic dynamics are endowed with various dynamic characteristics of attractors underlying many cognitive functions. This paper presents a novel method for neuromorphic implementation of a two-variable WTA circuit with NMDARs aimed at implementing decision-making, working memory and hysteresis in visual perceptions. The method proposed is a dynamical system approach of circuit synthesis based on a biophysically plausible WTA model. Notably, slow and non-linear temporal dynamics of NMDAR-mediated synapses was generated. Circuit simulations in Cadence reproduced ramping neural activities observed in electrophysiological recordings in experiments of decision-making, the sustained activities observed in the prefrontal cortex during working memory, and classical hysteresis behavior during visual discrimination tasks. Furthermore, theoretical analysis of the dynamical system approach illuminated the underlying mechanisms of decision-making, memory capacity and hysteresis loops. The consistence between the circuit simulations and theoretical analysis demonstrated that the WTA circuit with NMDARs was able to capture the attractor dynamics underlying these cognitive functions. Their physical implementations as elementary modules are promising for assembly into integrated neuromorphic cognitive systems. PMID:28223913

Neurobeachin and the Kinesin KIF21B Are Critical for Endocytic Recycling of NMDA Receptors and Regulate Social Behavior.

PubMed

Gromova, Kira V; Muhia, Mary; Rothammer, Nicola; Gee, Christine E; Thies, Edda; Schaefer, Irina; Kress, Sabrina; Kilimann, Manfred W; Shevchuk, Olga; Oertner, Thomas G; Kneussel, Matthias

2018-05-29

Autism spectrum disorders (ASDs) are associated with mutations affecting synaptic components, including GluN2B-NMDA receptors (NMDARs) and neurobeachin (NBEA). NBEA participates in biosynthetic pathways to regulate synapse receptor targeting, synaptic function, cognition, and social behavior. However, the role of NBEA-mediated transport in specific trafficking routes is unclear. Here, we highlight an additional function for NBEA in the local delivery and surface re-insertion of synaptic receptors in mouse neurons. NBEA dynamically interacts with Rab4-positive recycling endosomes, transiently enters spines in an activity-dependent manner, and regulates GluN2B-NMDAR recycling. Furthermore, we show that the microtubule growth inhibitor kinesin KIF21B constrains NBEA dynamics and is present in the NBEA-recycling endosome-NMDAR complex. Notably, Kif21b knockout decreases NMDAR surface expression and alters social behavior in mice, consistent with reported social deficits in Nbea mutants. The influence of NBEA-KIF21B interactions on GluN2B-NMDAR local recycling may be relevant to mechanisms underlying ASD etiology. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Neuromorphic Implementation of Attractor Dynamics in a Two-Variable Winner-Take-All Circuit with NMDARs: A Simulation Study.

PubMed

You, Hongzhi; Wang, Da-Hui

2017-01-01

Neural networks configured with winner-take-all (WTA) competition and N-methyl-D-aspartate receptor (NMDAR)-mediated synaptic dynamics are endowed with various dynamic characteristics of attractors underlying many cognitive functions. This paper presents a novel method for neuromorphic implementation of a two-variable WTA circuit with NMDARs aimed at implementing decision-making, working memory and hysteresis in visual perceptions. The method proposed is a dynamical system approach of circuit synthesis based on a biophysically plausible WTA model. Notably, slow and non-linear temporal dynamics of NMDAR-mediated synapses was generated. Circuit simulations in Cadence reproduced ramping neural activities observed in electrophysiological recordings in experiments of decision-making, the sustained activities observed in the prefrontal cortex during working memory, and classical hysteresis behavior during visual discrimination tasks. Furthermore, theoretical analysis of the dynamical system approach illuminated the underlying mechanisms of decision-making, memory capacity and hysteresis loops. The consistence between the circuit simulations and theoretical analysis demonstrated that the WTA circuit with NMDARs was able to capture the attractor dynamics underlying these cognitive functions. Their physical implementations as elementary modules are promising for assembly into integrated neuromorphic cognitive systems.

REVIEWING THE KETAMINE MODEL FOR SCHIZOPHRENIA

PubMed Central

Frohlich, Joel

2014-01-01

The observation that antagonists of the N-methyl-D-aspartate glutamate receptor (NMDAR), such as phencyclidine (PCP) and ketamine, transiently induce symptoms of acute schizophrenia had led to a paradigm shift from dopaminergic to glutamatergic dysfunction in pharmacological models of schizophrenia. The glutamate hypothesis can explain negative and cognitive symptoms of schizophrenia better than the dopamine hypothesis, and has the potential to explain dopamine dysfunction itself. The pharmacological and psychomimetic effects of ketamine, which is safer for human subjects than phencyclidine, are herein reviewed. Ketamine binds to a variety of receptors, but principally acts at the NMDAR, and convergent genetic and molecular evidence point to NMDAR hypofunction in schizophrenia. Furthermore, NMDAR hypofunction can explain connectional and oscillatory abnormalities in schizophrenia in terms of both weakened excitation of inhibitory -aminobutyric acidergic (GABAergic) interneurons that synchronize cortical networks and disinhibition of principal cells. Individuals with prenatal aberrations of NMDAR might experience the onset of schizophrenia towards the completion of synaptic pruning in adolescence, when network connectivity drops below a critical value. We conclude that ketamine challenge is useful for studying the positive, negative, and cognitive symptoms, dopaminergic and GABAergic dysfunction, age of onset, functional dysconnectivity, and abnormal cortical oscillations observed in acute schizophrenia. PMID:24257811

Functional diversification of maize RNA polymerase IV and V subtypes via alternative catalytic subunits

DOE PAGES

Haag, Jeremy R.; Brower-Toland, Brent; Krieger, Elysia K.; ...

2014-10-02

Unlike nuclear multisubunit RNA polymerases I, II, and III, whose subunit compositions are conserved throughout eukaryotes, plant RNA polymerases IV and V are nonessential, Pol II-related enzymes whose subunit compositions are still evolving. Whereas Arabidopsis Pols IV and V differ from Pol II in four or five of their 12 subunits, respectively, and differ from one another in three subunits, proteomic analyses show that maize Pols IV and V differ from Pol II in six subunits but differ from each other only in their largest subunits. Use of alternative catalytic second subunits, which are nonredundant for development and paramutation, yieldsmore » at least two sub-types of Pol IV and three subtypes of Pol V in maize. Pol IV/Pol V associations with MOP1, RMR1, AGO121, Zm_DRD1/CHR127, SHH2a, and SHH2b extend parallels between paramutation in maize and the RNA-directed DNA methylation pathway in Arabidopsis.« less

Functional diversification of maize RNA polymerase IV and V subtypes via alternative catalytic subunits

PubMed Central

Haag, Jeremy R.; Brower-Toland, Brent; Krieger, Elysia K.; Sidorenko, Lyudmila; Nicora, Carrie D.; Norbeck, Angela D.; Irsigler, Andre; LaRue, Huachun; Brzeski, Jan; McGinnis, Karen; Ivashuta, Sergey; Pasa-Tolic, Ljiljana; Chandler, Vicki L.; Pikaard, Craig S.

2014-01-01

Summary Unlike nuclear multisubunit RNA polymerases I, II and III, whose subunit compositions are conserved throughout eukaryotes, plant RNA Polymerases IV and V are non-essential, Pol II-related enzymes whose subunit compositions are still evolving. Whereas Arabidopsis Pols IV and V differ from Pol II in four or five of their twelve subunits, respectively, and differ from one another in three subunits, proteomic analyses show that maize Pols IV and V differ from Pol II in six subunits, but differ from each other only in their largest subunits. Use of alternative catalytic second-subunits, which are non-redundant for development and paramutation, yields at least two subtypes of Pol IV, and three subtypes of Pol V in maize. Pol IV/V associations with MOP1, RMR1, AGO121, Zm_DRD1/CHR127, SHH2a and SHH2b extend parallels between paramutation in maize and the RNA-directed DNA methylation pathway in Arabidopsis. PMID:25284785

IL1R2, CCR2, and CXCR4 May Form Heteroreceptor Complexes with NMDAR and D2R: Relevance for Schizophrenia

PubMed Central

Borroto-Escuela, Dasiel O.; Tarakanov, Alexander O.; Bechter, Karl; Fuxe, Kjell

2017-01-01

The mild neuroinflammation hypothesis of schizophrenia was introduced by Bechter in 2001. It has been hypothesized that a hypofunction of glutamatergic signaling via N-methyl-D-aspartate receptors (NMDARs) and hyperactivation of dopamine D2 receptors play a role in schizophrenia. The triplet puzzle theory states that sets of triplet amino acid homologies guide two different receptors toward each other and contributes to the formation of a receptor heteromer. It is, therefore, proposed that putative NMDAR-C-C chemokine receptor type 2 (CCR2), NMDAR-C-X-C chemokine receptor type 4 (CXCR4), and NMDAR- interleukin 1 receptor type II (IL1R2) heteromers can be formed in the neuronal networks in mild neuroinflammation due to demonstration of Gly-Leu-Leu (GLL), Val-Ser-Thr (VST), and/or Ser-Val-Ser (SVS) amino acid homologies between these receptor protomers. This molecular process may underlie the ability to produce symptoms of schizophrenia in mild neuroinflammation. In this state, volume transmission (VT) is increased involving increased extracellular vesicle-mediated VT from microglia and astroglia. These vesicles may contain CCR2, CXCR4, and/or IL1R2 as well as their ligands and upon internalization by endocytic pathways into neurons can form heteroreceptor complexes with NMDAR in the plasma membrane with pathological allosteric receptor–receptor interactions involving increased internalization and reduced NMDAR signaling. The triplet puzzle theory also suggests the formation of putative D2R-CCR2, D2R-CXCR4, and D2R-IL1R2 heteromers in mild neuroinflammation in view of their demonstrated sets of Leu-Tyr-Ser (LYS), Leu-Pro-Phe (LPF), and/or Ser-Leu-Ala (SLA) triplet homologies. These D2R heteroreceptor complexes may also contribute to schizophrenia-like symptoms in mild neuroinflammation by enhancing D2R protomer function. PMID:28261115

Separate Ionotropic and Metabotropic Glutamate Receptor Functions in Depotentiation vs. LTP: A Distinct Role for Group1 mGluR Subtypes and NMDARs

PubMed Central

Latif-Hernandez, Amira; Faldini, Enrico; Ahmed, Tariq; Balschun, Detlef

2016-01-01

Depotentiation (DP) is a mechanism by which synapses that have recently undergone long-term potentiation (LTP) can reverse their synaptic strengthening within a short time-window after LTP induction. Group 1 metabotropic glutamate receptors (mGluRs) were shown to be involved in different forms of LTP and long-term depression (LTD), but little is known about their roles in DP. Here, we generated DP by applying low-frequency stimulation (LFS) at 5 Hz after LTP had been induced by a single train of theta-burst-stimulation (TBS). While application of LFS for 2 min (DP2′) generated only a short-lasting DP that was independent of the activation of N-methyl-D-aspartate receptors (NMDARs) and group 1 mGluRs, LFS given for 8 min (DP8′) induced a robust DP that was maintained for at least 2 h. This strong form of DP was contingent on NMDAR activation. Interestingly, DP8′ appears to include a metabotropic NMDAR function because it was blocked by the competitive NMDAR antagonist D-AP5 but not by the use-dependent inhibitor MK-801 or high Mg2+. Furthermore, DP8′ was enhanced by application of the mGluR1 antagonist (YM 298198, 1 μM). The mGluR5 antagonist 2-Methyl-6(phenylethynyl) pyridine (MPEP, 40 μM), in contrast, failed to affect it. The induction of LTP, in turn, was NMDAR dependent (as tested with D-AP5), and blocked by MPEP but not by YM 298198. These results indicate a functional dissociation of mGluR1 and mGluR5 in two related and consecutively induced types of NMDAR-dependent synaptic plasticity (LTP → DP) with far-reaching consequences for their role in plasticity and learning under normal and pathological conditions. PMID:27872582

Separate Ionotropic and Metabotropic Glutamate Receptor Functions in Depotentiation vs. LTP: A Distinct Role for Group1 mGluR Subtypes and NMDARs.

PubMed

Latif-Hernandez, Amira; Faldini, Enrico; Ahmed, Tariq; Balschun, Detlef

2016-01-01

Depotentiation (DP) is a mechanism by which synapses that have recently undergone long-term potentiation (LTP) can reverse their synaptic strengthening within a short time-window after LTP induction. Group 1 metabotropic glutamate receptors (mGluRs) were shown to be involved in different forms of LTP and long-term depression (LTD), but little is known about their roles in DP. Here, we generated DP by applying low-frequency stimulation (LFS) at 5 Hz after LTP had been induced by a single train of theta-burst-stimulation (TBS). While application of LFS for 2 min (DP2') generated only a short-lasting DP that was independent of the activation of N -methyl-D-aspartate receptors (NMDARs) and group 1 mGluRs, LFS given for 8 min (DP8') induced a robust DP that was maintained for at least 2 h. This strong form of DP was contingent on NMDAR activation. Interestingly, DP8' appears to include a metabotropic NMDAR function because it was blocked by the competitive NMDAR antagonist D-AP5 but not by the use-dependent inhibitor MK-801 or high Mg 2+ . Furthermore, DP8' was enhanced by application of the mGluR1 antagonist (YM 298198, 1 μM). The mGluR5 antagonist 2-Methyl-6(phenylethynyl) pyridine (MPEP, 40 μM), in contrast, failed to affect it. The induction of LTP, in turn, was NMDAR dependent (as tested with D-AP5), and blocked by MPEP but not by YM 298198. These results indicate a functional dissociation of mGluR1 and mGluR5 in two related and consecutively induced types of NMDAR-dependent synaptic plasticity (LTP → DP) with far-reaching consequences for their role in plasticity and learning under normal and pathological conditions.

Cerebrospinal fluid cyto-/chemokine profile during acute herpes simplex virus induced anti-N-methyl-d-aspartate receptor encephalitis and in chronic neurological sequelae.

PubMed

Kothur, Kavitha; Gill, Deepak; Wong, Melanie; Mohammad, Shekeeb S; Bandodkar, Sushil; Arbunckle, Susan; Wienholt, Louise; Dale, Russell C

2017-08-01

To examine the cytokine/chemokine profile of cerebrospinal fluid (CSF) during acute herpes simplex virus-induced N-methyl-d-aspartate receptor (NMDAR) autoimmunity and in chronic/relapsing post-herpes simplex virus encephalitis (HSE) neurological syndromes. We measured longitudinal serial CSF cyto-/chemokines (n=34) and a glial marker (calcium-binding astroglial protein, S100B) in one patient during acute HSE and subsequent anti-NMDAR encephalitis, and compared the results with those from two patients with anti-NMDAR encephalitis without preceding HSE. We also compared cyto-/chemokines in cross-sectional CSF samples from three children with previous HSE who had ongoing chronic or relapsing neurological symptoms (2yr 9 mo-16y after HSE) with those in a group of children having non-inflammatory neurological conditions (n=20). Acute HSE showed elevation of a broad range of all T-helper-subset-related cyto-/chemokines and S100B whereas the post-HSE anti-NMDAR encephalitis phase showed persistent elevation of two of five T-helper-1 (chemokine [C-X-C motif] ligand 9 [CXCL9], CXCL10), three of five predominantly B-cell (CXCL13, CCL19, a proliferation-inducing ligand [APRIL])-mediated cyto-/chemokines, and interferon-α. The post-HSE anti-NMDAR encephalitis inflammatory response was more pronounced than anti-NMDAR encephalitis. All three chronic post-HSE cases showed persistent elevation of CXCL9, CXCL10, and interferon-α, and there was histopathological evidence of chronic lymphocytic inflammation in one biopsied case 7 years after HSE. Two of three chronic cases showed a modest response to immune therapy. HSE-induced anti-NMDAR encephalitis is a complex and pronounced inflammatory syndrome. There is persistent CSF upregulation of cyto-/chemokines in chronic or relapsing post-HSE neurological symptoms, which may be modifiable with immune therapy. The elevated cyto-/chemokines may be targets of monoclonal therapies. © 2017 Mac Keith Press.

DYRK1A-mediated phosphorylation of GluN2A at Ser(1048) regulates the surface expression and channel activity of GluN1/GluN2A receptors.

PubMed

Grau, Cristina; Arató, Krisztina; Fernández-Fernández, José M; Valderrama, Aitana; Sindreu, Carlos; Fillat, Cristina; Ferrer, Isidre; de la Luna, Susana; Altafaj, Xavier

2014-01-01

N-methyl-D-aspartate glutamate receptors (NMDARs) play a pivotal role in neural development and synaptic plasticity, as well as in neurological disease. Since NMDARs exert their function at the cell surface, their density in the plasma membrane is finely tuned by a plethora of molecules that regulate their production, trafficking, docking and internalization in response to external stimuli. In addition to transcriptional regulation, the density of NMDARs is also influenced by post-translational mechanisms like phosphorylation, a modification that also affects their biophysical properties. We previously described the increased surface expression of GluN1/GluN2A receptors in transgenic mice overexpressing the Dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A), suggesting that DYRK1A regulates NMDARs. Here we have further investigated whether the density and activity of NMDARs were modulated by DYRK1A phosphorylation. Accordingly, we show that endogenous DYRK1A is recruited to GluN2A-containing NMDARs in the adult mouse brain, and we identify a DYRK1A phosphorylation site at Ser(1048) of GluN2A, within its intracellular C-terminal domain. Mechanistically, the DYRK1A-dependent phosphorylation of GluN2A at Ser(1048) hinders the internalization of GluN1/GluN2A, causing an increase of surface GluN1/GluN2A in heterologous systems, as well as in primary cortical neurons. Furthermore, GluN2A phosphorylation at Ser(1048) increases the current density and potentiates the gating of GluN1/GluN2A receptors. We conclude that DYRK1A is a direct regulator of NMDA receptors and we propose a novel mechanism for the control of NMDAR activity in neurons.

DYRK1A-mediated phosphorylation of GluN2A at Ser1048 regulates the surface expression and channel activity of GluN1/GluN2A receptors

PubMed Central

Grau, Cristina; Arató, Krisztina; Fernández-Fernández, José M.; Valderrama, Aitana; Sindreu, Carlos; Fillat, Cristina; Ferrer, Isidre; de la Luna, Susana; Altafaj, Xavier

2014-01-01

N-methyl-D-aspartate glutamate receptors (NMDARs) play a pivotal role in neural development and synaptic plasticity, as well as in neurological disease. Since NMDARs exert their function at the cell surface, their density in the plasma membrane is finely tuned by a plethora of molecules that regulate their production, trafficking, docking and internalization in response to external stimuli. In addition to transcriptional regulation, the density of NMDARs is also influenced by post-translational mechanisms like phosphorylation, a modification that also affects their biophysical properties. We previously described the increased surface expression of GluN1/GluN2A receptors in transgenic mice overexpressing the Dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A), suggesting that DYRK1A regulates NMDARs. Here we have further investigated whether the density and activity of NMDARs were modulated by DYRK1A phosphorylation. Accordingly, we show that endogenous DYRK1A is recruited to GluN2A-containing NMDARs in the adult mouse brain, and we identify a DYRK1A phosphorylation site at Ser1048 of GluN2A, within its intracellular C-terminal domain. Mechanistically, the DYRK1A-dependent phosphorylation of GluN2A at Ser1048 hinders the internalization of GluN1/GluN2A, causing an increase of surface GluN1/GluN2A in heterologous systems, as well as in primary cortical neurons. Furthermore, GluN2A phosphorylation at Ser1048 increases the current density and potentiates the gating of GluN1/GluN2A receptors. We conclude that DYRK1A is a direct regulator of NMDA receptors and we propose a novel mechanism for the control of NMDAR activity in neurons. PMID:25368549

Lack of antibodies to NMDAR or VGKC-complex in GAD and cardiolipin antibody-positive refractory epilepsy.

PubMed

Liimatainen, Suvi; Peltola, Jukka; Hietaharju, Aki; Sabater, Lidia; Lang, Bethan

2014-03-01

Over the last few years autoantibodies against neuronal proteins have been identified in several forms of autoimmune encephalitis and epilepsy. NMDA receptor (NMDAR) and voltage gated potassium channel (VGKC) complex antibodies are mainly associated with limbic encephalitis (LE) whereas glutamic acid decarboxylase antibodies (GADA) and anticardiolipin (ACL) antibodies are more commonly detected in patients with chronic epilepsy. Clinical features vary between these antibodies suggesting the specificity of different neuronal antibodies in seizures. Serum samples of 14 GADA positive and 24 ACL positive patients with refractory epilepsy were analyzed for the presence of VGKC or NMDAR antibodies. No positive VGKC or NMDAR antibodies were found in these patients. The results confirm the different significance of these neuronal antibodies in seizure disorders. Different autoantibodies have different significance in seizures and probably have different pathophysiological mechanisms of actions. Copyright © 2014 Elsevier B.V. All rights reserved.

Chronic EtOH effects on putative measures of compulsive behavior in mice

PubMed Central

Radke, Anna K.; Jury, Nicholas J.; Kocharian, Adrina; Marcinkiewcz, Catherine A.; Lowery-Gionta, Emily G.; Pleil, Kristen E.; McElligott, Zoe A.; McKlveen, Jessica M.; Kash, Thomas L.; Holmes, Andrew

2015-01-01

Addictions, including alcohol use disorders (AUDs), are characterized by the loss of control over drug seeking and consumption, but the neural circuits and signaling mechanisms responsible for the transition from controlled use to uncontrolled abuse remain incompletely understood. Prior studies have shown that ‘compulsive-like’ behaviors in rodents, e.g., persistent responding for ethanol (EtOH) despite punishment, are increased after chronic exposure to EtOH. The main goal of the current study was to assess the effects of chronic intermittent EtOH (CIE) exposure on multiple, putative measures of compulsive-like EtOH seeking in C57BL/6J mice. Mice were exposed to two or four weekly cycles of CIE and then, post-withdrawal, tested for progressive ratio responding for EtOH, sustained responding during signaled EtOH-unavailability and (footshock) punished-suppression of responding for EtOH. Results showed that mice exposed to CIE exhibited attenuated suppression of EtOH-seeking during punishment, as compared to air-exposed controls. By contrast, CIE exposure affected neither punished food reward-seeking behavior, nor other putative measures of compulsive-like EtOH-seeking. Ex vivo RT-PCR analysis of brain tissue found reduced sensitivity to punished EtOH-seeking after CIE exposure was accompanied by a significant increase in gene expression of the GluN1 and GluN2A subunits of the N-methyl-D-aspartate receptor (NMDAR), specifically in the medial orbitofrontal cortex (mOFC). Moreover, slice electrophysiological analysis revealed increased NMDAR-mediated currents in the mOFC after CIE exposure in test-naïve mice. Collectively, the current findings add to growing body of evidence demonstrating that chronic exposure to EtOH fosters resistance to punished EtOH-seeking in association with adaptations in cortical glutamatergic transmission. PMID:26687341

Knockout of NMDA receptors in parvalbumin interneurons recreates autism-like phenotypes.

PubMed

Saunders, John A; Tatard-Leitman, Valerie M; Suh, Jimmy; Billingslea, Eddie N; Roberts, Timothy P; Siegel, Steven J

2013-04-01

Autism is a disabling neurodevelopmental disorder characterized by social deficits, language impairment, and repetitive behaviors with few effective treatments. New evidence suggests that autism has reliable electrophysiological endophenotypes and that these measures may be caused by n-methyl-d-aspartic acid receptor (NMDAR) disruption on parvalbumin (PV)-containing interneurons. These findings could be used to create new translational biomarkers. Recent developments have allowed for cell-type selective knockout of NMDARs in order to examine the perturbations caused by disrupting specific circuits. This study examines several electrophysiological and behavioral measures disrupted in autism using a PV-selective reduction in NMDA R1 subunit. Mouse electroencephalograph (EEG) was recorded in response to auditory stimuli. Event-related potential (ERP) component amplitude and latency analysis, social testing, and premating ultrasonic vocalizations (USVs) recordings were performed. Correlations were examined between the ERP latency and behavioral measures. The N1 ERP latency was delayed, sociability was reduced, and mating USVs were impaired in PV-selective NMDA Receptor 1 Knockout (NR1 KO) as compared with wild-type mice. There was a significant correlation between N1 latency and sociability but not between N1 latency and premating USV power or T-maze performance. The increases in N1 latency, impaired sociability, and reduced vocalizations in PV-selective NR1 KO mice mimic similar changes found in autism. Electrophysiological changes correlate to reduced sociability, indicating that the local circuit mechanisms controlling N1 latency may be utilized in social function. Therefore, we propose that behavioral and electrophysiological alterations in PV-selective NR1 KO mice may serve as a useful model for therapeutic development in autism. Autism Res 2013, 6: 69-77. © 2013 International Society for Autism Research, Wiley Periodicals, Inc. © 2013 International Society for Autism Research, Wiley Periodicals, Inc.

Low doses of dextromethorphan have a beneficial effect in the treatment of neuropathic pain.

PubMed

Morel, Véronique; Pickering, Gisèle; Etienne, Monique; Dupuis, Amandine; Privat, Anne-Marie; Chalus, Maryse; Eschalier, Alain; Daulhac, Laurence

2014-12-01

N-methyl-D-aspartate receptor (NMDAR) antagonists may be given in persistent neuropathic pain, but adverse events especially with ketamine may limit their clinical use. Less central and cognitive adverse events are described with dextromethorphan and memantine. These molecules have been explored in many preclinical and clinical studies, but data are conflicting as regards neuropathic pain alleviation. Dextromethorphan and memantine have been administered to animals after spinal nerve ligation (SNL) to evaluate their antinociceptive/cognitive effects and associated molecular events, including the phosphorylation of several tyrosine (pTyr(1336), pTyr(1472)) residues in the NR2B NMDAR subunit. Spinal nerve ligation and sham animals received dextromethorphan (10 mg/kg, i.p.), memantine (20 mg/kg, i.p.) or saline (1 mL/kg, i.p.). These drugs were administered once symptoms of allodynia and hyperalgesia had developed. Tests were carried out before and after surgery. Tactile allodynia, mechanical hyperalgesia and spatial memory were, respectively, evaluated by von Frey, Randall & Selitto and Y-maze tests and molecular events by Western blot analysis. Spinal nerve-ligated animals displayed nociception and impaired spatial memory. Dextromethorphan, but not memantine, reversed neuropathic pain (NP) symptoms, restored spatial memory integrity and decreased the expression of pTyr(1336)NR2B. Following postoperative administration of dextromethorphan, this study has demonstrated for the first time a concordance between behaviour, cognitive function and molecular events via pTyr(1336)NR2B for neuropathic pain alleviation. Confirmation of these findings in patients would constitute a major step forward in the treatment of neuropathic pain and in the improvement of cognitive function and quality of life. © 2014 Société Française de Pharmacologie et de Thérapeutique.

GRIN2A polymorphisms and expression levels are associated with lead-induced neurotoxicity.

PubMed

Wu, Yu; Wang, Yiqing; Wang, Miaomiao; Sun, Na; Li, Chunping

2017-04-01

Lead acts as an antagonist of the N-methyl-d-aspartate receptor (NMDAR). GRIN2A encodes an important subunit of NMDARs and may be a critical factor in the mechanism of lead neurotoxicity. Changes in GRIN2A expression levels or gene variants may be mechanisms of lead-induced neurotoxicity. In this study, we hypothesized that GRIN2A might contribute to lead-induced neurotoxicity. A preliminary HEK293 cell experiment was performed to analyze the association between GRIN2A expression and lead exposure. In addition, in a population-based study, serum GRIN2A levels were measured in both lead-exposed and control populations. To detect further the influence of GRIN2A gene single nucleotide polymorphisms (SNPs) in lead-induced neurotoxicity, 3 tag SNPs (rs2650429, rs6497540, and rs9302415) were genotyped in a case-control study that included 399 lead-exposed subjects and 398 controls. Lead exposure decreased GRIN2A expression levels in HEK293 cells ( p < 0.001) compared with lead-free cells. Lead-exposed individuals had lower serum GRIN2A levels compared with controls ( p < 0.001), and we found a trend of decreasing GRIN2A level with an increase in blood lead level ( p < 0.001). In addition, we found a significant association between rs2650429 CT and TT genotypes and risk of lead poisoning compared with the rs2650429 CC genotype (adjusted odds ratio = 1.42, 95% confidence interval = 1.01-2.00]. Therefore, changes in GRIN2A expression levels and variants may be important mechanisms in the development of lead-induced neurotoxicity.

Activation of α7 nicotinic acetylcholine receptors protects potentiated synapses from depotentiation during theta pattern stimulation in the hippocampal CA1 region of rats

PubMed Central

Galvez, Bryan; Gross, Noah; Sumikawa, Katumi

2016-01-01

Long-term potentiation (LTP) shows memory-like consolidation and thus becomes increasingly resistant to disruption by low-frequency stimulation (LFS). However, it is known that nicotine application during LFS uniquely depotentiates consolidated LTP. Here, we investigated how nicotine contributes to the disruption of stabilized LTP in the hippocampal CA1 region. We found that nicotine-induced depotentiation is not due to masking LTP by inducing long-term depression and requires the activation of GluN2A-containing NMDARs. We further examined whether nicotine-induced depotentiation involves the reversal of LTP mechanisms. LTP causes phosphorylation of Ser-831 on GluA1 subunits of AMPARs that increases the single-channel conductance of AMPARs. This phosphorylation remained unchanged after depotentiation. LTP involves the insertion of new AMPARs into the synapse and the internalization of AMPARs is associated with dephosphorylation of Ser-845 on GluA1 and caspase-3 activity. Nicotine-induced depotentiation occurred without dephosphorylation of the Ser-845 and in the presence of a caspase-3 inhibitor. LTP is also accompanied by increased filamentous actin (F-actin), which controls spine size. Nicotine-induced depotentiation was prevented by jasplakinolide, which stabilizes F-actin, suggesting that nicotine depotentiates consolidated LTP by destabilizing F-actin. α7 nicotinic acetylcholine receptor (nAChR) antagonists mimicked the effect of nicotine and selective removal of hippocampal cholinergic input caused depotentiation in the absence of nicotine, suggesting that nicotine depotentiates consolidated LTP by inducing α7 nAChR desensitization. Our results demonstrate a new role for nicotinic cholinergic systems in protecting potentiated synapses from depotentiation by preventing GluN2A-NMDAR-mediated signaling for actin destabilization. PMID:26867505

Activation of α7 nicotinic acetylcholine receptors protects potentiated synapses from depotentiation during theta pattern stimulation in the hippocampal CA1 region of rats.

PubMed

Galvez, Bryan; Gross, Noah; Sumikawa, Katumi

2016-06-01

Long-term potentiation (LTP) shows memory-like consolidation and thus becomes increasingly resistant to disruption by low-frequency stimulation (LFS). However, it is known that nicotine application during LFS uniquely depotentiates consolidated LTP. Here, we investigated how nicotine contributes to the disruption of stabilized LTP in the hippocampal CA1 region. We found that nicotine-induced depotentiation is not due to masking LTP by inducing long-term depression and requires the activation of GluN2A-containing NMDARs. We further examined whether nicotine-induced depotentiation involves the reversal of LTP mechanisms. LTP causes phosphorylation of Ser-831 on GluA1 subunits of AMPARs that increases the single-channel conductance of AMPARs. This phosphorylation remained unchanged after depotentiation. LTP involves the insertion of new AMPARs into the synapse and the internalization of AMPARs is associated with dephosphorylation of Ser-845 on GluA1 and caspase-3 activity. Nicotine-induced depotentiation occurred without dephosphorylation of the Ser-845 and in the presence of a caspase-3 inhibitor. LTP is also accompanied by increased filamentous actin (F-actin), which controls spine size. Nicotine-induced depotentiation was prevented by jasplakinolide, which stabilizes F-actin, suggesting that nicotine depotentiates consolidated LTP by destabilizing F-actin. α7 nicotinic acetylcholine receptor (nAChR) antagonists mimicked the effect of nicotine and selective removal of hippocampal cholinergic input caused depotentiation in the absence of nicotine, suggesting that nicotine depotentiates consolidated LTP by inducing α7 nAChR desensitization. Our results demonstrate a new role for nicotinic cholinergic systems in protecting potentiated synapses from depotentiation by preventing GluN2A-NMDAR-mediated signaling for actin destabilization. Copyright © 2016 Elsevier Ltd. All rights reserved.

Postpartum estrogen withdrawal impairs hippocampal neurogenesis and causes depression- and anxiety-like behaviors in mice.

PubMed

Zhang, Zhuan; Hong, Juan; Zhang, Suyun; Zhang, Tingting; Sha, Sha; Yang, Rong; Qian, Yanning; Chen, Ling

2016-04-01

Postpartum estrogen withdrawal is known to be a particularly vulnerable time for depressive symptoms. Ovariectomized adult mice (OVX-mice) treated with hormone-simulated pregnancy (HSP mice) followed by a subsequent estradiol benzoate (EB) withdrawal (EW mice) exhibited depression- and anxiety-like behaviors, as assessed by forced swim, tail suspension and elevated plus-maze, while HSP mice, OVX mice or EB-treated OVX mice (OVX/EB mice) did not. The survival and neurite growth of newborn neurons in hippocampal dentate gyrus were examined on day 5 after EW. Compared with controls, the numbers of 28-day-old BrdU(+) and BrdU(+)/NeuN(+) cells were increased in HSP mice but significantly decreased in EW mice; the numbers of 10-day-old BrdU(+) cells were increased in HSP mice and OVX/EB mice; and the density of DCX(+) fibers was reduced in EW mice and OVX mice. The phosphorylation of hippocampal NMDA receptor (NMDAr) NR2B subunit or Src was increased in HSP mice but decreased in EW mice. NMDAr agonist NMDA prevented the loss of 28-day-old BrdU(+) cells and the depression- and anxiety-like behaviors in EW mice. NR2B inhibitor Ro25-6981 or Src inhibitor dasatinib caused depression- and anxiety-like behaviors in HSP mice with the reduction of 28-day-old BrdU(+) cells. The hippocampal BDNF levels were reduced in EW mice and OVX mice. TrkB receptor inhibitor K252a reduced the density of DCX(+) fibers in HSP mice without the reduction of 28-day-old BrdU(+) cells, or the production of affective disorder. Collectively, these results indicate that postpartum estrogen withdrawal impairs hippocampal neurogenesis in mice that show depression- and anxiety-like behaviors. Copyright © 2016 Elsevier Ltd. All rights reserved.

Pharmacological evidence that a failure to recruit NMDA receptors contributes to impaired fear extinction retention in adolescent rats.

PubMed

Baker, Kathryn D; Richardson, Rick

2017-09-01

Adolescents, both humans and rodents, exhibit a marked impairment in extinction of fear relative to younger and older groups which could be caused by a failure to efficiently recruit NMDA receptors (NMDARs) in adolescence. It is well-established that systemic administration of NMDAR antagonists (e.g., MK801) before extinction training impairs the retention of extinction in adult and juvenile rodents, but it is unknown whether this is also the case for adolescents. Therefore, in the present study we investigated the effect of pharmacologically manipulating the NMDAR on extinction retention in adolescent rats. When extinction retention is typically impaired (i.e., after one session of extinction training) adolescent male rats given d-cycloserine (a partial NMDAR agonist) showed enhanced extinction retention relative to saline-treated animals while animals given MK801 (a non-competitive antagonist) did not exhibit any further impairment of extinction retention relative to the controls. In a further two experiments we demonstrated that when two sessions of extinction training separated by either 4 or 24h intervals were given to adolescent rats, saline-treated animals exhibited good extinction retention and the animals given MK801 before the second session exhibited impaired extinction retention. These findings suggest that extinction in adolescence does not initially involve NMDARs and this is a likely mechanism that contributes to the impaired fear inhibition observed at this age. However, NMDARs appear to be recruited with extended extinction training or after administration of a partial agonist, both of which lead to effective extinction retention. Copyright © 2016 Elsevier Inc. All rights reserved.

Metaplastic Effects of Subanesthetic Ketamine on CA1 Hippocampal Function

PubMed Central

Izumi, Yukitoshi; Zorumski, Charles F.

2014-01-01

Ketamine is a non-competitive N-methyl-D-aspartate receptor (NMDAR) antagonist of interest in neuropsychiatry. In the present studies, we examined the effects of subanesthetic, low micromolar ketamine on excitatory postsynaptic potentials (EPSPs), population spikes (PSs) and synaptic plasticity in the CA1 region of rat hippocampal slices. Ketamine acutely inhibited NMDAR-mediated synaptic responses with half-maximal effects near 10 µM. When administered for 15–30 min at 1–10 µM, ketamine had no effect on baseline dendritic AMPA receptor-mediated EPSPs, but persistently enhanced somatic EPSPs in the pyramidal cell body layer and augmented PS firing. Acute low micromolar ketamine also had no effect on the induction of long-term potentiation (LTP) but blocked long-term depression (LTD). Following 30 min administration of 1–10 µM ketamine, however, a slowly developing and persistent form of LTP inhibition was observed that took two hours following ketamine washout to become manifest. This LTP inhibition did not result from prolonged or enhanced NMDAR inhibition during drug washout. Effects of low ketamine on somatic EPSPs and LTP were not mimicked by a high ketamine concentration that completely inhibited NMDARs, and both of these effects were blocked by co-administration of low ketamine with a low concentration of the competitive NMDAR antagonist, 2-amino-5-phosphonovalerate or inhibitors of nitric oxide synthase. These results indicate that concentrations of ketamine relevant to psychotropic and psychotomimetic effects have complex metaplastic effects on hippocampal function that involve activation of unblocked NMDARs during ketamine exposure. PMID:25128848

Enhanced interaction among ErbB4, PSD-95 and NMDAR by chronic MK-801 treatment is associated with behavioral abnormalities.

PubMed

Li, Ji-Tao; Feng, Yu; Su, Yun-Ai; Wang, Xiao-Dong; Si, Tian-Mei

2013-07-01

The neuregulin 1 (NRG1)-ErbB4 signaling pathway has been implicated in the pathophysiology of schizophrenia. Recent studies suggest that this pathway may interact with the N-methyl-d-aspartate receptor (NMDAR) via the postsynaptic scaffold protein PSD-95. This interaction is of particular interest given the leading role of the NMDAR hypofunction in schizophrenia. The present study investigated the short- and long-term effects of chronic NMDAR blockade on the functional interaction between the two systems in rat prefrontal cortex and hippocampus using immunoprecipitation. Adult male Wistar rats were treated intraperitoneally with MK-801 (0.25 mg/kg) or saline for 28 days. Twenty-four hours after the last injection, the associations of ErbB4 with PSD-95 and NMDAR were enhanced in the prefrontal cortex, whereas only phosphorylated-ErbB4 relative to ErbB4 was increased in the hippocampus. These effects, however, were not detectable 12 days after the last MK-801 treatment, indicating the reversible nature of these changes. We also investigated the effects of chronic MK-801 treatment on locomotion, prepulse inhibition, recognition memory, and spatial working memory. The results showed that this treatment led to decreased locomotor activity, reduced exploration in the center arena, and elevated startle magnitudes, indicating an anxiety-like phenotype. Taken together, our findings suggest that the NRG1-ErbB4 signaling could be modulated by repeated NMDAR blockade, and provide further evidence for the cross-talk between the two signaling pathways. Copyright © 2013 Elsevier Inc. All rights reserved.

Some assembly required: Contributions of Tom Stevens' lab to the V-ATPase field.

PubMed

Graham, Laurie A; Finnigan, Gregory C; Kane, Patricia M

2018-06-01

Tom Stevens' lab has explored the subunit composition and assembly of the yeast V-ATPase for more than 30 years. Early studies helped establish yeast as the predominant model system for study of V-ATPase proton pumps and led to the discovery of protein splicing of the V-ATPase catalytic subunit. The Vma - phenotype, characteristic of loss-of-V-ATPase activity in yeast was key in determining the enzyme's subunit composition via yeast genetics. V-ATPase subunit composition proved to be highly conserved among eukaryotes. Genetic screens for new vma mutants led to identification of a set of dedicated V-ATPase assembly factors and helped unravel the complex pathways for V-ATPase assembly. In later years, exploration of the evolutionary history of several V-ATPase subunits provided new information about the enzyme's structure and function. This review highlights V-ATPase work in the Stevens' lab between 1987 and 2017. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Platelet Kainate Receptor Signaling Promotes Thrombosis by Stimulating Cyclooxygenase Activation

PubMed Central

Sun, Henry; Swaim, AnneMarie; Herrera, Jesus Enrique; Becker, Diane; Becker, Lewis; Srivastava, Kalyan; Thompson, Laura E.; Shero, Michelle R.; Perez-Tamayo, Alita; Suktitpat, Bhoom; Mathias, Rasika; Contractor, Anis; Faraday, Nauder; Morrell, Craig N.

2009-01-01

Rationale Glutamate is a major signaling molecule that binds to glutamate receptors including the ionotropic glutamate receptors; kainate (KA) receptor (KAR), the N-methyl-D-aspartate (NMDA) receptor (NMDAR), and the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor (AMPAR). Each is well characterized in the central nervous system (CNS), but glutamate has important signaling roles in peripheral tissues as well, including a role in regulating platelet function. Objective Our previous work has demonstrated that glutamate is released by platelets in high concentrations within a developing thrombus and increases platelet activation and thrombosis. We now show that platelets express a functional KAR that drives increased agonist induced platelet activation. Methods and Results KAR induced increase in platelet activation is in part the result of activation of platelet cyclooxygenase (COX) in a Mitogen Activated Protein Kinase (MAPK) dependent manner. Platelets derived from KA receptor subunit knockout mice (GluR6−/−) are resistant to KA effects and have a prolonged time to thrombosis in vivo. Importantly, we have also identified polymorphisms in KA receptor subunits that are associated with phenotypic changes in platelet function in a large group of Caucasians and African Americans. Conclusion Our data demonstrate that glutamate regulation of platelet activation is in part COX dependent, and suggest that the KA receptor is a novel anti-thrombotic target. PMID:19679838

Polypeptide composition of fraction 1 protein of the somatic hybrid between Petunia parodii and Petunia parviflora.

PubMed

Kumar, A; Wilson, D; Cocking, E C

1981-04-01

The analysis of the subunit polypeptide composition of Fraction 1 protein provides information on the expression of both chloroplast and nuclear genomes. Fraction 1 protein, isolated from leaves of the somatic hybrid plants derived form the fusion of protoplasts of Petunia parodii and P. parviflora, was analyzed for its subunit polypeptide composition by isoelectric focusing in 8 M urea. The fraction 1 protein enzyme oligomer in the somatic hybrid plants contained small subunits resulting from the expression of both parental nuclear genomes, but probably only one of the parental large subunits, namely that of P. parodii. The relevance of such somatic hybrid material for the study of nucleocytoplasmic interrelationship is discussed, as well as the use of these fraction 1 protein isoelectric focusing patterns for the analysis of taxonomic relationships in Petunia.

Anti-N-methyl-D-aspartate receptor and anti-ribosomal-P autoantibodies contribute to cognitive dysfunction in systemic lupus erythematosus.

PubMed

Massardo, L; Bravo-Zehnder, M; Calderón, J; Flores, P; Padilla, O; Aguirre, J M; Scoriels, L; González, A

2015-05-01

Autoantibodies against N-methyl-D-aspartate receptor (anti-NMDAR) and ribosomal-P (anti-P) antigens are potential pathogenic factors in the frequently observed diffuse brain dysfunctions in patients with systemic lupus erythematosus (SLE). Although studies have been conducted in this area, the role of anti-NMDAR antibodies in SLE cognitive dysfunction remains elusive. Moreover, the specific contribution of anti-P antibodies has not been reported yet. The present study attempts to clarify the contribution of anti-NMDAR and anti-P antibodies to cognitive dysfunction in SLE. The Cambridge Neuropsychological Test Automated Battery (CANTAB) was used to assess a wide range of cognitive function areas in 133 Chilean women with SLE. ANCOVA models included autoantibodies, patient and disease features. Cognitive deficit was found in 20%. Higher SLEDAI-2K scores were associated with impairment in spatial memory and learning abilities, whereas both anti-NMDAR and anti-P antibodies contributed to deficits in attention and spatial planning abilities, which reflect fronto-parietal cortex dysfunctions. These results reveal an association of active disease together with specific circulating autoantibodies, such as anti-NMDAR and anti-P, with cognitive dysfunction in SLE patients. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

The effect of hippocampal NMDA receptor blockade by MK-801 on cued fear extinction.

PubMed

Zhang, Bo; Li, Chuan-Yu; Wang, Xiu-Song

2017-08-14

Extinction of conditioned fear has been suggested to be a new form of learning instead of erasure of what was originally learned, and the process is NMDA (N-methyl d-aspartate) receptor (NMDAR) dependent. Most of studies have so far revealed the important roles of NMDARs in the amygdala and medial prefrontal cortex (mPFC) in cued fear extinction. Although the ventral hippocampus has intimately reciprocal connections with the amygdala and mPFC, the role of its NMDARs in cued fear extinction remains unclear. The present experiment explored the issue by bilateral pre-extinction microinjection of the noncompetitive NMDAR antagonist MK-801 into the ventral hippocampus. Four groups of rats were given habituation, tone cued fear conditioning, fear extinction training and extinction test. Prior to extinction training, rats received bilateral infusions of either MK-801 (1.5, 3, or 6μg/0.5μl) or saline. Our results showed that MK-801 reduced freezing on the first trial of extinction training with no impact on within-session acquisition of extinction, and that the lower doses of MK-801 resulted in increased freezing on the extinction retrieval test. These findings suggest that ventral hippocampal NMDARs are necessary for the consolidation of tone cued fear extinction. Copyright © 2017 Elsevier B.V. All rights reserved.

Inhibition of NMDA Receptors Prevents the Loss of BDNF Function Induced by Amyloid β.

PubMed

Tanqueiro, Sara R; Ramalho, Rita M; Rodrigues, Tiago M; Lopes, Luísa V; Sebastião, Ana M; Diógenes, Maria J

2018-01-01

Brain-derived neurotrophic factor (BDNF) plays important functions in cell survival and differentiation, neuronal outgrowth and plasticity. In Alzheimer's disease (AD), BDNF signaling is known to be impaired, partially because amyloid β (Aβ) induces truncation of BDNF main receptor, TrkB-full length (TrkB-FL). We have previously shown that such truncation is mediated by calpains, results in the formation of an intracellular domain (ICD) fragment and causes BDNF loss of function. Since calpains are Ca 2+ -dependent proteases, we hypothesized that excessive intracellular Ca 2+ build-up could be due to dysfunctional N-methyl-d-aspartate receptors (NMDARs) activation. To experimentally address this hypothesis, we investigated whether TrkB-FL truncation by calpains and consequent BDNF loss of function could be prevented by NMDAR blockade. We herein demonstrate that a NMDAR antagonist, memantine, prevented excessive calpain activation and TrkB-FL truncation induced by Aβ 25-35 . When calpains were inhibited by calpastatin, BDNF was able to increase the dendritic spine density of neurons exposed to Aβ 25135 . Moreover, NMDAR inhibition by memantine also prevented Aβ-driven deleterious impact of BDNF loss of function on structural (spine density) and functional outcomes (synaptic potentiation). Collectively, these findings support NMDAR/Ca 2+ /calpains mechanistic involvement in Aβ-triggered BDNF signaling disruption.

Exploring neuroprotective potential of Withania somnifera phytochemicals by inhibition of GluN2B-containing NMDA receptors: An in silico study.

PubMed

Kumar, Gaurav; Patnaik, Ranjana

2016-07-01

N-methyl-d-aspartate receptors (NMDARs) mediated excitotoxicity has been implicated in multi-neurodegenerative diseases. Due to lack of efficacy and adverse effects of NMDA receptor antagonists, search for herbal remedies that may act as therapeutic agents is an active area of research to combat these diseases. Withania somnifera (WS) is being used for centuries as a nerve tonic and Nootropic agents. The present study targets the in silico evaluation of the neuroprotective efficacy of W. somnifera phytochemicals by inhibition of NMDA receptor-mediated excitotoxicity through allosteric inhibition of the GluN2B containing NMDARs. We predict Blood Brain Barrier (BBB) penetration, mutagenicity, drug-likeness and Human Intestinal Absorption properties of 25 WS phytochemicals. Further, molecular docking was performed to know whether these phytochemicals inhibit the GluN2B containing NMDARs or not. The results suggest that Anaferine, Beta-Sitosterol, Withaferin A, Withanolide A, Withanolide B and Withanolide D inhibit GluN2B containing NMDARs through allosteric mode similar to the well-known selective antagonist Ifenprodil. These phytochemicals have potential as an essentially useful oral drug to counter NMDARs mediated excitotoxicity and to treat multi-neurodegenerative diseases. Copyright © 2016 Elsevier Ltd. All rights reserved.

PSD95: A synaptic protein implicated in schizophrenia or autism?

PubMed

Coley, Austin A; Gao, Wen-Jun

2018-03-02

The molecular components of the postsynaptic density (PSD) in excitatory synapses of the brain are currently being investigated as one of the major etiologies of neurodevelopmental disorders such as schizophrenia (SCZ) and autism. Postsynaptic density protein-95 (PSD-95) is a major regulator of synaptic maturation by interacting, stabilizing and trafficking N-methyl-d-aspartic acid receptors (NMDARs) and α-amino-3-hydroxy-5-methyl-4-isox-azoleproprionic acid receptors (AMPARs) to the postsynaptic membrane. Recently, there has been overwhelming evidence that associates PSD-95 disruption with cognitive and learning deficits observed in SCZ and autism. For instance, recent genomic and sequencing studies of psychiatric patients highlight the aberrations at the PSD of glutamatergic synapses that include PSD-95 dysfunction. In animal studies, PSD-95 deficiency shows alterations in NMDA and AMPA-receptor composition and function in specific brain regions that may contribute to phenotypes observed in neuropsychiatric pathologies. In this review, we describe the role of PSD-95 as an essential scaffolding protein during synaptogenesis and neurodevelopment. More specifically, we discuss its interactions with NMDA receptor subunits that potentially affect glutamate transmission, and the formation of silent synapses during critical time points of neurodevelopment. Furthermore, we describe how PSD-95 may alter dendritic spine morphologies, thus regulating synaptic function that influences behavioral phenotypes in SCZ versus autism. Understanding the role of PSD-95 in the neuropathologies of SCZ and autism will give an insight of the cellular and molecular attributes in the disorders, thus providing treatment options in patients affected. Copyright © 2017 Elsevier Inc. All rights reserved.

Step-wise and lineage-specific diversification of plant RNA polymerase genes and origin of the largest plant-specific subunits.

PubMed

Wang, Yaqiong; Ma, Hong

2015-09-01

Proteins often function as complexes, yet little is known about the evolution of dissimilar subunits of complexes. DNA-directed RNA polymerases (RNAPs) are multisubunit complexes, with distinct eukaryotic types for different classes of transcripts. In addition to Pol I-III, common in eukaryotes, plants have Pol IV and V for epigenetic regulation. Some RNAP subunits are specific to one type, whereas other subunits are shared by multiple types. We have conducted extensive phylogenetic and sequence analyses, and have placed RNAP gene duplication events in land plant history, thereby reconstructing the subunit compositions of the novel RNAPs during land plant evolution. We found that Pol IV/V have experienced step-wise duplication and diversification of various subunits, with increasingly distinctive subunit compositions. Also, lineage-specific duplications have further increased RNAP complexity with distinct copies in different plant families and varying divergence for subunits of different RNAPs. Further, the largest subunits of Pol IV/V probably originated from a gene fusion in the ancestral land plants. We propose a framework of plant RNAP evolution, providing an excellent model for protein complex evolution. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Transient focal ischemia results in persistent and widespread neuroinflammation and loss of glutamate NMDA receptors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dhawan, J.; Biegon, A.; Dhawan, J.

2010-03-04

Stroke is accompanied by neuroinflammation in humans and animal models. To examine the temporal and anatomical profile of neuroinflammation and NMDA receptors (NMDAR) in a stroke model, rats (N = 17) were subjected to a 90 min occlusion of the middle cerebral artery (MCAO) and compared to sham (N = 5) and intact (N = 4) controls. Striatal and parietal cortical infarction was confirmed by MRI 24 h after reperfusion. Animals were killed 14 or 30-40 days later and consecutive coronal cryostat sections were processed for quantitative autoradiography with the neuroinflammation marker [{sup 3}H]PK11195 and the NMDAR antagonist [{sup 3}H]MK801.more » Significantly increased specific binding of [{sup 3}H]PK11195 relative to non-ischemic controls was observed in the ipsilateral striatum (> 3 fold, p < 0.0001), substantia innominata (> 2 fold) with smaller (20%-80%) but statistically significant (p = 0.002-0.04) ipsilateral increases in other regions partially involved in the infarct such as the parietal and piriform cortex, and in the lateral septum, which was not involved in the infarct. Trends for increases in PBR density were also observed in the contralateral hemisphere. In the same animals, NMDAR specific binding was significantly decreased bilaterally in the septum, substantia innominata and ventral pallidum. Significant decreases were also seen in the ipsilateral striatum, accumbens, frontal and parietal cortex. The different anatomical distribution of the two phenomena suggests that neuroinflammation does not cause the observed reduction in NMDAR, though loss of NMDAR may be locally augmented in ipsilateral regions with intense neuroinflammation. Persistent, bilateral loss of NMDAR, probably reflecting receptor down regulation and internalization, may be responsible for some of the effects of stroke on cognitive function which cannot be explained by infarction alone.« less

Deficits in cognitive function and hippocampal plasticity in GM2/GD2 synthase knockout mice.

PubMed

Sha, Sha; Zhou, Libin; Yin, Jun; Takamiya, Koga; Furukawa, Keiko; Furukawa, Koichi; Sokabe, Masahiro; Chen, Ling

2014-04-01

In this study, we used GM2/GD2 synthase knockout (GM2/GD2−/−) mice to examine the influence of deficiency in ganglioside “a-pathway” and “b-pathway” on cognitive performances and hippocampal synaptic plasticity. Eight-week-old GM2/GD2−/− male mice showed a longer escape-latency in Morris water maze test and a shorter latency in step-down inhibitory avoidance task than wild-type (WT) mice. Schaffer collateral-CA1 synapses in the hippocampal slices from GM2/GD2−/− mice showed an increase in the slope of EPSPs with reduced paired-pulse facilitation, indicating an enhancement of their presynaptic glutamate release. In GM2/GD2−/− mice, NMDA receptor (NMDAr)-dependent LTP could not be induced by high-frequency (100–200 Hz) tetanus or θ-burst conditioning stimulation (CS), whereas NMDAr-independent LTP was induced by medium-frequency CS (20–50 Hz). The application of mono-sialoganglioside GM1 in the slice from GM2/GD2−/− mice, to specifically recover the a-pathway, prevented the increased presynaptic glutamate release and 20 Hz-LTP induction, whereas it could not rescue the impaired NMDAr-dependent LTP. These findings suggest that b-pathway deficiency impairs cognitive function probably through suppression of NMDAr-dependent LTP, while a-pathway deficiency may facilitate NMDAr-independent LTP through enhancing presynaptic glutamate release. As both of the NMDAr-independent LTP and increased presynaptic glutamate release were sensitive to the blockade of L-type voltage-gated Ca2+ channels (L-VGCC), a-pathway deficiency may affect presynaptic L-VGCC.

N-methyl-D-aspartate receptor antibody-mediated neurological disease: results of a UK-based surveillance study in children.

PubMed

Wright, Sukhvir; Hacohen, Yael; Jacobson, Leslie; Agrawal, Shakti; Gupta, Rajat; Philip, Sunny; Smith, Martin; Lim, Ming; Wassmer, Evangeline; Vincent, Angela

2015-06-01

N-methyl-D-aspartate receptor antibody (NMDAR-Ab) encephalitis is a well-recognised clinico-immunological syndrome that presents with neuropsychiatric symptoms cognitive decline, movement disorder and seizures. This study reports the clinical features, management and neurological outcomes of paediatric NMDAR-Ab-mediated neurological disease in the UK. A prospective surveillance study. Children with NMDAR-Ab-mediated neurological diseases were voluntarily reported to the British Neurological Surveillance Unit (BPNSU) from November 2010 to December 2011. Initial and follow-up questionnaires were sent out to physicians. Thirty-one children fulfilled the criteria for the study. Eight presented during the study period giving an incidence of 0.85 per million children per year (95% CI 0.64 to 1.06); 23 cases were historical. Behavioural change and neuropsychiatric features were present in 90% of patients, and seizures and movement disorders both in 67%. Typical NMDAR-Ab encephalitis was reported in 24 children and partial phenotype without encephalopathy in seven, including predominantly psychiatric (four) and movement disorder (three). All patients received steroids, 22 (71%) received intravenous immunoglobulin, 9 (29%) received plasma exchange,and 10 (32%) received second-line immunotherapy. Of the 23 patients who were diagnosed early, 18 (78%) made a full recovery compared with only 1 of 8 (13%) of the late diagnosed patients (p=0.002, Fisher's exact test). Seven patients relapsed, with four needing additional second-line immunotherapy. Paediatric NMDAR-Ab-mediated neurological disease appears to be similar to adult NMDAR-Ab encephalitis, but some presented with a partial phenotype. Early treatment was associated with a quick and often full recovery. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Acute and chronic effects of NMDA receptor antagonists in rodents, relevance to negative symptoms of schizophrenia: a translational link to humans.

PubMed

Neill, Joanna C; Harte, Michael K; Haddad, Peter M; Lydall, Emma S; Dwyer, Dominic M

2014-05-01

Negative symptoms of schizophrenia remain an unmet clinical need as they are common, persistent, respond poorly to existing treatments and lead to disability. Blunted affect, alogia, asociality, anhedonia and avolition are regarded as key negative symptoms despite DSM-IV-TR specifying a more limited range. The key to development of improved therapies is improved animal models that mimic the human condition in terms of behaviour and pathology and that predict efficacy of novel treatments in patients. Accumulating evidence shows that NMDA receptor (NMDAR) antagonists mimic cognitive deficits of relevance to schizophrenia in animals, along with associated pathological changes. This review examines evidence for the ability of NMDAR antagonists to mimic anhedonia and asociality, two negative symptoms of schizophrenia, in animals. The use of various species, paradigms and treatment regimens are reviewed. We conclude that sub-chronic treatment with NMDAR antagonists, typically PCP, induces social withdrawal in animals but not anhedonia. NMDAR antagonists have further effects in paradigms such as motivational salience that may be useful for mimicking other aspects of negative symptoms but these require further development. Sub-chronic treatment regimens of NMDAR antagonists also have some neurobiological effects of relevance to negative symptoms. It is our view that a sub-chronic treatment regime with NMDAR antagonists, particularly PCP, with animals tested following a wash-out period and in a battery of tests to assess certain behaviours of relevance to negative symptoms and social withdrawal (the animal equivalent of asociality) is valuable. This will enhance our understanding of the psycho and neuropathology of specific negative symptom domains and allow early detection of novel pharmacological targets. © 2013 Elsevier B.V. and ECNP All rights reserved.

Neuroprotective effects of Bacopa monnieri (Brahmi) on novel object recognition and NMDAR1 immunodensity in the prefrontal cortex, striatum and hippocampus of sub-chronic phencyclidine rat model of schizophrenia.

PubMed

Piyabhan, Pritsana; Wetchateng, Thanitsara

2014-08-01

Cognitive impairment is a major problem, which eventually develops in schizophrenia. It contributes to the patients 'functional disability and cannot be attenuated by antipsychotic drugs. Bacopa monnieri (Brahmi), a neuroprotective herbal medicine in the elderly, might be a novel neuroprotective agent for prevention of cognitive deficit in schizophrenia. To study neuroprotective effects ofBrahmi on novel object recognition task and cerebral glutamate/N-methyl-D- aspartate receptor subtype 1 (NMDAR1) immunodensity in sub-chronic phencyclidine (PCP) rat model ofschizophrenia. Rats were assigned to three groups; Group-A: Control, Group-B: PCP administration and Group- C: Brahmi + PCP. Discrimination ratio (DR) representing cognitive ability was obtainedfrom novel object recognition task. NMDAR1 immunodensity was measured in prefrontal cortex, striatum, cornu ammonis fields I (CA 1) and 2/3 (CA2/3) and dentate gyrus (DG) using immunohistochemistry. DR was significantly reduced in PCP group compared with control. This occurred alongside NMDAR1 up-regulation in CA2/3 and DG but not in prefrontal cortex, striatum or CA1. Brahmi + PCP group showed an increased DR score up to normal which occurred alongside a significantly decreased NMDARI immunodensity in CA2/3 and DG compared with PCP group. Cognitive deficit observed in rats receiving PCP was mediated by NMDAR1 up-regulation in CA2/3 and DG Interestingly, receiving Brahmi before PCP administration can restore this cognitive deficit by decreasingNMDAR1 in these brain areas. Therefore, Brahmi could be a novel neuroprotective agentfor the prevention ofcognitive deficit in schizophrenia.

Mitochondrial matrix metalloproteinase activation decreases myocyte contractility in hyperhomocysteinemia.

PubMed

Moshal, Karni S; Tipparaju, Srinivas M; Vacek, Thomas P; Kumar, Munish; Singh, Mahavir; Frank, Iluiana E; Patibandla, Phani K; Tyagi, Neetu; Rai, Jayesh; Metreveli, Naira; Rodriguez, Walter E; Tseng, Michael T; Tyagi, Suresh C

2008-08-01

Cardiomyocyte N-methyl-d-aspartate receptor-1 (NMDA-R1) activation induces mitochondrial dysfunction. Matrix metalloproteinase protease (MMP) induction is a negative regulator of mitochondrial function. Elevated levels of homocysteine [hyperhomocysteinemia (HHCY)] activate latent MMPs and causes myocardial contractile abnormalities. HHCY is associated with mitochondrial dysfunction. We tested the hypothesis that HHCY activates myocyte mitochondrial MMP (mtMMP), induces mitochondrial permeability transition (MPT), and causes contractile dysfunction by agonizing NMDA-R1. The C57BL/6J mice were administered homocystinemia (1.8 g/l) in drinking water to induce HHCY. NMDA-R1 expression was detected by Western blot and confocal microscopy. Localization of MMP-9 in the mitochondria was determined using confocal microscopy. Ultrastructural analysis of the isolated myocyte was determined by electron microscopy. Mitochondrial permeability was measured by a decrease in light absorbance at 540 nm using the spectrophotometer. The effect of MK-801 (NMDA-R1 inhibitor), GM-6001 (MMP inhibitor), and cyclosporine A (MPT inhibitor) on myocyte contractility and calcium transients was evaluated using the IonOptix video edge track detection system and fura 2-AM. Our results demonstrate that HHCY activated the mtMMP-9 and caused MPT by agonizing NMDA-R1. A significant decrease in percent cell shortening, maximal rate of contraction (-dL/dt), and maximal rate of relaxation (+dL/dt) was observed in HHCY. The decay of calcium transient amplitude was faster in the wild type compared with HHCY. Furthermore, the HHCY-induced decrease in percent cell shortening, -dL/dt, and +dL/dt was attenuated in the mice treated with MK-801, GM-6001, and cyclosporin A. We conclude that HHCY activates mtMMP-9 and induces MPT, leading to myocyte mechanical dysfunction by agonizing NMDA-R1.

Infralimbic GluN2A-Containing NMDA Receptors Modulate Reconsolidation of Cocaine Self-Administration Memory.

PubMed

Hafenbreidel, Madalyn; Rafa Todd, Carolynn; Mueller, Devin

2017-04-01

Addiction is characterized by high relapse susceptibility, and relapse can be triggered by drug-associated cues. Cue presentation induces retrieval of the drug-cue memory, which becomes labile and must be reconsolidated into long-term storage. Repeated unpaired cue presentation, however, promotes extinction. Cue-reactivity can be reduced by blocking reconsolidation or facilitating extinction, which are mediated by NMDA receptors (NMDArs). However, the role of NMDArs in either process following self-administration is unclear. Thus, to determine their role in extinction, rats learned to self-administer cocaine before receiving injections of the NMDAr antagonist CPP immediately after four 45-min extinction sessions. During a subsequent 90-min extinction retention test, CPP-treated rats lever pressed less than saline-treated rats indicating that NMDAr blockade facilitated extinction or disrupted drug-cue memory reconsolidation. In addition, infusing CPP into the infralimbic medial prefrontal cortex (IL-mPFC), a structure implicated in extinction, before four 45-min or immediately after four 30min extinction sessions, had similar results during the extinction retention tests. Next, the GluN2A-selective antagonist NVP or GluN2B-selective antagonist Ro25 was infused into IL-mPFC or nucleus accumbens (NAc) shell, another structure implicated in extinction, after four 45-min extinction sessions. Blocking GluN2A-, but not GluN2B-, containing NMDArs, in IL-mPFC or NAc shell reduced lever pressing during the extinction retention tests. Finally, to dissociate reconsolidation from extinction, NVP was infused into IL-mPFC after four 10-min reactivation sessions, which resulted in reduced lever pressing during the retention test. These results indicate that IL-mPFC GluN2A-containing NMDArs modulate reconsolidation, and suggest a novel treatment strategy, as reducing cue reactivity could limit relapse susceptibility.

Clinical presentation of anti-N-methyl-d-aspartate receptor and anti-voltage-gated potassium channel complex antibodies in children: A series of 24 cases.

PubMed

Konuskan, Bahadir; Yildirim, Mirac; Topaloglu, Haluk; Erol, Ilknur; Oztoprak, Ulkuhan; Tan, Huseyin; Gocmen, Rahsan; Anlar, Banu

2018-01-01

The symptomatology and paraclinical findings of antibody-mediated encephalitis, a relatively novel disorder, are still being characterized in adults and children. A high index of suspicion is needed in order to identify these cases among children presenting with various neurological symptoms. The aim of this study is to examine the clinical, demographic and laboratory findings and outcome of children with anti-NMDAR and anti-VGKC encephalitis for any typical or distinctive features. Cases diagnosed with anti-N-Methyl d-aspartate receptor (NMDAR) and anti-voltage gated potassium channel (VGKC) antibody-mediated encephalopathy in four major child neurology centers are described. In four years, 16 children with NMDAR and 8 children with VGKC antibody-associated disease were identified in the participating centers. The most frequent initial manifestation consisted of generalized seizures and cognitive symptoms in both groups. Movement abnormalities were frequent in anti-NMDAR patients and autonomic symptoms, in anti-VGKC patients. Cerebrospinal fluid (CSF) protein, cell count and IgG index were normal in 9/15 anti-NMDAR and 5/8 anti-VGKC patients tested. EEG and MRI findings were usually nonspecific and non-contributory. The rate and time of recovery was not related to age, sex, acute or subacute onset, antibody type, MRI, EEG or CSF results. Treatment within 3 months of onset was associated with normal neurological outcome. Our results suggest anti-NMDAR and VGKC encephalopathies mostly present with non-focal neurological symptoms longer than 3 weeks. In contrast with adult cases, routine CSF testing, MRI and EEG did not contribute to the diagnosis in this series. Copyright © 2017 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.

N-Methyl D-Aspartate (NMDA) Receptor Antagonists and Memantine Treatment for Alzheimer’s Disease, Vascular Dementia and Parkinson’s Disease

PubMed Central

Olivares, David; Deshpande, Varun K.; Shi, Ying; Lahiri, Debomoy K.; Greig, Nigel H.; Rogers, Jack T.; Huang, Xudong

2016-01-01

Memantine, a partial antagonist of N-methyl-D-aspartate receptor (NMDAR), approved for moderate to severe Alzheimer’s disease (AD) treatment within the US and Europe under brand name Namenda (Forest), Axura and Akatinol (Merz), and Ebixa and Abixa (Lundbeck), may have potential in alleviating additional neurological conditions, such as vascular dementia (VD) and Parkinson’s disease (PD). In various animal models, memantine has been reported to be a neuroprotective agent that positively impacts both neurodegenerative and vascular processes. While excessive levels of glutamate result in neurotoxicity, in part through the over-activation of NMDARs, memantine—as a partial NMDAR antagonist, blocks the NMDA glutamate receptors to normalize the glutamatergic system and ameliorate cognitive and memory deficits. The key to memantine’s therapeutic action lies in its uncompetitive binding to the NMDAR through which low affinity and rapid off-rate kinetics of memantine at the level of the NMDAR-channel preserves the physiological function of the receptor, underpinning memantine’s tolerability and low adverse event profile. As the biochemical pathways evoked by NMDAR antagonism also play a role in PD and since no other drug is sufficiently effective to substitute for the first-line treatment of L-dopa despite its side effects, memantine may be useful in PD treatment with possibly fewer side effects. In spite of the relative modest nature of its adverse effects, memantine has been shown to provide only a moderate decrease in clinical deterioration in AD and VD, and hence efforts are being undertaken in the design of new and more potent memantine-based drugs to hopefully provide greater efficacy. PMID:21875407

Clinical and autoimmune features of a patient with autism spectrum disorder seropositive for anti-NMDA-receptor autoantibody.

PubMed

Gréa, Hélène; Scheid, Isabelle; Gaman, Alexandru; Rogemond, Véronique; Gillet, Sandy; Honnorat, Jérôme; Bolognani, Federico; Czech, Christian; Bouquet, Céline; Toledano, Elie; Bouvard, Manuel; Delorme, Richard; Groc, Laurent; Leboyer, Marion

2017-03-01

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by dysfunctions in social interactions resulting from a complex interplay between immunogenetic and environmental risk factors. Autoimmunity has been proposed as a major etiological component of ASD. Whether specific autoantibodies directed against brain targets are involved in ASD remains an open question. Here, we identified within a cohort an ASD patient with multiple circulating autoantibodies, including the well-characterized one against glutamate NMDA receptor (NMDAR-Ab). The patient exhibited alexithymia and previously suffered from two major depressive episodes without psychotic symptoms. Using a single molecule-based imaging approach, we demonstrate that neither NMDAR-Ab type G immunoglobulin purified from the ASD patient serum, nor that from a seropositive healthy subject, disorganize membrane NMDAR complexes at synapses. These findings suggest that the autistic patient NMDAR-Abs do not play a direct role in the etiology of ASD and that other autoantibodies directed against neuronal targets should be investigated.

Trans-synaptic zinc mobilization improves social interaction in two mouse models of autism through NMDAR activation.

PubMed

Lee, Eun-Jae; Lee, Hyejin; Huang, Tzyy-Nan; Chung, Changuk; Shin, Wangyong; Kim, Kyungdeok; Koh, Jae-Young; Hsueh, Yi-Ping; Kim, Eunjoon

2015-05-18

Genetic aspects of autism spectrum disorders (ASDs) have recently been extensively explored, but environmental influences that affect ASDs have received considerably less attention. Zinc (Zn) is a nutritional factor implicated in ASDs, but evidence for a strong association and linking mechanism is largely lacking. Here we report that trans-synaptic Zn mobilization rapidly rescues social interaction in two independent mouse models of ASD. In mice lacking Shank2, an excitatory postsynaptic scaffolding protein, postsynaptic Zn elevation induced by clioquinol (a Zn chelator and ionophore) improves social interaction. Postsynaptic Zn is mainly derived from presynaptic pools and activates NMDA receptors (NMDARs) through postsynaptic activation of the tyrosine kinase Src. Clioquinol also improves social interaction in mice haploinsufficient for the transcription factor Tbr1, which accompanies NMDAR activation in the amygdala. These results suggest that trans-synaptic Zn mobilization induced by clioquinol rescues social deficits in mouse models of ASD through postsynaptic Src and NMDAR activation.

Distance-dependent gradient in NMDAR-driven spine calcium signals along tapering dendrites

PubMed Central

Walker, Alison S.; Grillo, Federico; Jackson, Rachel E.; Rigby, Mark; Lowe, Andrew S.; Vizcay-Barrena, Gema; Fleck, Roland A.; Burrone, Juan

2017-01-01

Neurons receive a multitude of synaptic inputs along their dendritic arbor, but how this highly heterogeneous population of synaptic compartments is spatially organized remains unclear. By measuring N-methyl-d-aspartic acid receptor (NMDAR)-driven calcium responses in single spines, we provide a spatial map of synaptic calcium signals along dendritic arbors of hippocampal neurons and relate this to measures of synapse structure. We find that quantal NMDAR calcium signals increase in amplitude as they approach a thinning dendritic tip end. Based on a compartmental model of spine calcium dynamics, we propose that this biased distribution in calcium signals is governed by a gradual, distance-dependent decline in spine size, which we visualized using serial block-face scanning electron microscopy. Our data describe a cell-autonomous feature of principal neurons, where tapering dendrites show an inverse distribution of spine size and NMDAR-driven calcium signals along dendritic trees, with important implications for synaptic plasticity rules and spine function. PMID:28209776

NMDA Receptors Subserve Persistent Neuronal Firing During Working Memory In Dorsolateral Prefrontal Cortex

PubMed Central

Wang, Min; Yang, Yang; Wang, Ching-Jung; Gamo, Nao J.; Jin, Lu E.; Mazer, James A.; Morrison, John H.; Wang, Xiao-Jing; Arnsten, Amy F.T.

2013-01-01

Summary Neurons in the primate dorsolateral prefrontal cortex (dlPFC) generate persistent firing in the absence of sensory stimulation, the foundation of mental representation. Persistent firing arises from recurrent excitation within a network of pyramidal Delay cells. Here, we examined glutamate receptor influences underlying persistent firing in primate dlPFC during a spatial working memory task. Computational models predicted dependence on NMDA receptor (NMDAR) NR2B stimulation, and Delay cell persistent firing was abolished by local NR2B NMDAR blockade or by systemic ketamine administration. AMPA receptors (AMPAR) contributed background depolarization to sustain network firing. In contrast, many Response cells -which likely predominate in rodent PFC- were sensitive to AMPAR blockade and increased firing following systemic ketamine, indicating that models of ketamine actions should be refined to reflect neuronal heterogeneity. The reliance of Delay cells on NMDAR may explain why insults to NMDARs in schizophrenia or Alzheimer’s Disease profoundly impair cognition. PMID:23439125

Fasting Activation of AgRP Neurons Requires NMDA Receptors and Involves Spinogenesis and Increased Excitatory Tone

PubMed Central

Liu, Tiemin; Kong, Dong; Shah, Bhavik P.; Ye, Chianping; Koda, Shuichi; Saunders, Arpiar; Ding, Jun B.; Yang, Zongfang; Sabatini, Bernardo L.; Lowell, Bradford B.

2012-01-01

SUMMARY AgRP neuron activity drives feeding and weight gain while that of nearby POMC neurons does the opposite. However, the role of excitatory glutamatergic input in controlling these neurons is unknown. To address this question, we generated mice lacking NMDA receptors (NMDARs) on either AgRP or POMC neurons. Deletion of NMDARs from AgRP neurons markedly reduced weight, body fat and food intake whereas deletion from POMC neurons had no effect. Activation of AgRP neurons by fasting, as assessed by c-Fos, Agrp and Npy mRNA expression, AMPA receptor-mediated EPSCs, depolarization and firing rates, required NMDARs. Furthermore, AgRP but not POMC neurons have dendritic spines and increased glutamatergic input onto AgRP neurons caused by fasting was paralleled by an increase in spines, suggesting fasting induced synaptogenesis and spinogenesis. Thus glutamatergic synaptic transmission and its modulation by NMDARs play key roles in controlling AgRP neurons and determining the cellular and behavioral response to fasting. PMID:22325203

D-Serine and Serine Racemase Are Associated with PSD-95 and Glutamatergic Synapse Stability

PubMed Central

Lin, Hong; Jacobi, Ariel A.; Anderson, Stewart A.; Lynch, David R.

2016-01-01

D-serine is an endogenous coagonist at the glycine site of synaptic NMDA receptors (NMDARs), synthesized by serine racemase (SR) through conversion of L-serine. It is crucial for synaptic plasticity and is implicated in schizophrenia. Our previous studies demonstrated specific loss of SR, D-serine-responsive synaptic NMDARs, and glutamatergic synapses in cortical neurons lacking α7 nicotinic acetylcholine receptors, which promotes glutamatergic synapse formation and maturation during development. We thus hypothesize that D-serine and SR (D-serine/SR) are associated with glutamatergic synaptic development. Using morphological and molecular studies in cortical neuronal cultures, we demonstrate that D-serine/SR are associated with PSD-95 and NMDARs in postsynaptic neurons and with glutamatergic synapse stability during synaptic development. Endogenous D-serine and SR colocalize with PSD-95, but not presynaptic vesicular glutamate transporter 1 (VGLUT1), in glutamatergic synapses of cultured cortical neurons. Low-density astrocytes in cortical neuronal cultures lack SR expression but contain enriched D-serine in large vesicle-like structures, suggesting possible synthesis of D-serine in postsynaptic neurons and storage in astrocytes. More interestingly, endogenous D-serine and SR colocalize with PSD-95 in the postsynaptic terminals of glutamatergic synapses during early and late synaptic development, implicating involvement of D-serine/SR in glutamatergic synaptic development. Exogenous application of D-serine enhances the interactions of SR with PSD-95 and NR1, and increases the number of VGLUT1- and PSD-95-positive glutamatergic synapses, suggesting that exogenous D-serine enhances postsynaptic SR/PSD-95 signaling and stabilizes glutamatergic synapses during cortical synaptic development. This is blocked by NMDAR antagonist 2-amino-5-phosphonopentanoic acid (AP5) and 7-chlorokynurenic acid (7-CK), a specific antagonist at the glycine site of NMDARs, demonstrating that D-serine effects are mediated through postsynaptic NMDARs. Conversely, exogenous application of glycine has no such effects, suggesting D-serine, rather than glycine, modulates postsynaptic events. Taken together, our findings demonstrate that D-serine/SR are associated with PSD-95 and NMDARs in postsynaptic neurons and with glutamatergic synapse stability during synaptic development, implicating D-serine/SR as regulators of cortical synaptic and circuit development. PMID:26941605

D-Serine and Serine Racemase Are Associated with PSD-95 and Glutamatergic Synapse Stability.

PubMed

Lin, Hong; Jacobi, Ariel A; Anderson, Stewart A; Lynch, David R

2016-01-01

D-serine is an endogenous coagonist at the glycine site of synaptic NMDA receptors (NMDARs), synthesized by serine racemase (SR) through conversion of L-serine. It is crucial for synaptic plasticity and is implicated in schizophrenia. Our previous studies demonstrated specific loss of SR, D-serine-responsive synaptic NMDARs, and glutamatergic synapses in cortical neurons lacking α7 nicotinic acetylcholine receptors, which promotes glutamatergic synapse formation and maturation during development. We thus hypothesize that D-serine and SR (D-serine/SR) are associated with glutamatergic synaptic development. Using morphological and molecular studies in cortical neuronal cultures, we demonstrate that D-serine/SR are associated with PSD-95 and NMDARs in postsynaptic neurons and with glutamatergic synapse stability during synaptic development. Endogenous D-serine and SR colocalize with PSD-95, but not presynaptic vesicular glutamate transporter 1 (VGLUT1), in glutamatergic synapses of cultured cortical neurons. Low-density astrocytes in cortical neuronal cultures lack SR expression but contain enriched D-serine in large vesicle-like structures, suggesting possible synthesis of D-serine in postsynaptic neurons and storage in astrocytes. More interestingly, endogenous D-serine and SR colocalize with PSD-95 in the postsynaptic terminals of glutamatergic synapses during early and late synaptic development, implicating involvement of D-serine/SR in glutamatergic synaptic development. Exogenous application of D-serine enhances the interactions of SR with PSD-95 and NR1, and increases the number of VGLUT1- and PSD-95-positive glutamatergic synapses, suggesting that exogenous D-serine enhances postsynaptic SR/PSD-95 signaling and stabilizes glutamatergic synapses during cortical synaptic development. This is blocked by NMDAR antagonist 2-amino-5-phosphonopentanoic acid (AP5) and 7-chlorokynurenic acid (7-CK), a specific antagonist at the glycine site of NMDARs, demonstrating that D-serine effects are mediated through postsynaptic NMDARs. Conversely, exogenous application of glycine has no such effects, suggesting D-serine, rather than glycine, modulates postsynaptic events. Taken together, our findings demonstrate that D-serine/SR are associated with PSD-95 and NMDARs in postsynaptic neurons and with glutamatergic synapse stability during synaptic development, implicating D-serine/SR as regulators of cortical synaptic and circuit development.

The role of NMDA receptors in human eating behavior: evidence from a case of anti-NMDA receptor encephalitis.

PubMed

Perogamvros, Lampros; Schnider, Armin; Leemann, Beatrice

2012-06-01

Research in animal models has implicated N-methyl-D-aspartate (NMDA) receptors (NMDARs) in the control of food intake. Until now, these findings have been not replicated in humans. Here we describe a 22-year-old woman with anti-NMDAR encephalitis and no prior neurological or psychiatric history. Her clinical course was marked by successive eating disorders: anorexia followed by hyperphagia. We propose that, much as they do in other animals, NMDARs in humans interact with the neuroendocrine, homeostatic, and reward systems controlling food intake in the central and peripheral nervous system structures related to feeding and satiety.

Selective Impairment of Spatial Cognition Caused by Autoantibodies to the N-Methyl-d-Aspartate Receptor

PubMed Central

Chang, Eric H.; Volpe, Bruce T.; Mackay, Meggan; Aranow, Cynthia; Watson, Philip; Kowal, Czeslawa; Storbeck, Justin; Mattis, Paul; Berlin, RoseAnn; Chen, Huiyi; Mader, Simone; Huerta, Tomás S.; Huerta, Patricio T.; Diamond, Betty

2015-01-01

Patients with systemic lupus erythematosus (SLE) experience cognitive abnormalities in multiple domains including processing speed, executive function, and memory. Here we show that SLE patients carrying antibodies that bind DNA and the GluN2A and GluN2B subunits of the N-methyl-d-aspartate receptor (NMDAR), termed DNRAbs, displayed a selective impairment in spatial recall. Neural recordings in a mouse model of SLE, in which circulating DNRAbs penetrate the hippocampus, revealed that CA1 place cells exhibited a significant expansion in place field size. Structural analysis showed that hippocampal pyramidal cells had substantial reductions in their dendritic processes and spines. Strikingly, these abnormalities became evident at a time when DNRAbs were no longer detectable in the hippocampus. These results suggest that antibody-mediated neurocognitive impairments may be highly specific, and that spatial cognition may be particularly vulnerable to DNRAb-mediated structural and functional injury to hippocampal cells that evolves after the triggering insult is no longer present. PMID:26286205

Cortical activation of accumbens hyperpolarization-active NMDARs mediates aversion-resistant alcohol intake

PubMed Central

Seif, Taban; Chang, Shao-Ju; Simms, Jeffrey A; Gibb, Stuart L; Dadgar, Jahan; Chen, Billy T; Harvey, Brandon K; Ron, Dorit; Messing, Robert O; Bonci, Antonello; Hopf, F Woodward

2014-01-01

Compulsive drinking despite serious adverse medical, social and economic consequences is a characteristic of alcohol use disorders in humans. Although frontal cortical areas have been implicated in alcohol use disorders, little is known about the molecular mechanisms and pathways that sustain aversion-resistant intake. Here, we show that nucleus accumbens core (NAcore) NMDA-type glutamate receptors and medial prefrontal (mPFC) and insula glutamatergic inputs to the NAcore are necessary for aversion-resistant alcohol consumption in rats. Aversion-resistant intake was associated with a new type of NMDA receptor adaptation, in which hyperpolarization-active NMDA receptors were present at mPFC and insula but not amygdalar inputs in the NAcore. Accordingly, inhibition of Grin2c NMDA receptor subunits in the NAcore reduced aversion-resistant alcohol intake. None of these manipulations altered intake when alcohol was not paired with an aversive consequence. Our results identify a mechanism by which hyperpolarization-active NMDA receptors under mPFC- and insula-to-NAcore inputs sustain aversion-resistant alcohol intake. PMID:23817545

Need for Better Diabetes Treatment: The Therapeutic Potential of NMDA Receptor Antagonists.

PubMed

Welters, A; Lammert, E; Mayatepek, E; Meissner, T

2017-01-01

Diabetes mellitus is the most common metabolic disorder in children and adolescents. Optimal control of blood glucose concentration is essential to prevent acute and diabetic long-term complications. The options to treat diabetes have clearly improved over the last decades, however, to date neither type 1 diabetes nor type 2 diabetes mellitus can be cured. Therefore, diabetes research aims at developing β-cell protective agents that prevent or even reverse diabetes onset. N-methyl-D-aspartate receptors (NMDARs) are glutamate-gated ion channels that are widely expressed in the central nervous system (CNS) where they hold central roles in CNS function. NMDAR dysfunction is associated with several neurological and psychiatric disorders and therefore NMDAR modulators have several potential therapeutic indications. Only little is known about the role of pancreatic NMDA receptors. Our data provide evidence that inhibition of pancreatic NMDARs, either genetically or pharmacologically with the over-the-counter drug dextromethorphan, increases glucose-stimulated insulin secretion from mouse and human pancreatic islets, improves glucose tolerance in mice and individuals with diabetes and promotes islet cell survival under diabetogenic conditions. Thus, our data indicate for the first time that NMDAR antagonists could serve as adjunct treatment for diabetes mellitus. The development of a safe, blood glucose lowering and particularly β-cell protective medication would significantly enhance current diabetes treatment. © Georg Thieme Verlag KG Stuttgart · New York.

Interactions of genotype and glutenin subunit composition on breadmaking quality of durum 1AS•1AL-1DL translocation lines

USDA-ARS?s Scientific Manuscript database

Dual purpose durum (Triticum turgidum L. subsp. durum) wheat, having both good pasta and breadmaking quality, would be an advantage in the market. In this study, we evaluated the effects of genotype and varying HMW and LMW glutenin subunit composition on durum breadmaking quality. Genotypes includ...

Peripheral NMDA Receptor/NO System Blockage Inhibits Itch Responses Induced by Chloroquine in Mice

PubMed Central

Haddadi, Nazgol-Sadat; Foroutan, Arash; Ostadhadi, Sattar; Azimi, Ehsan; Rahimi, Nastaran; Nateghpour, Mehdi; Lerner, Ethan A.; Dehpour, Ahmad Reza

2017-01-01

Intradermal administration of chloroquine (CQ) provokes scratching behavior in mice. Chloroquine-induced itch is histamine-independent and we have reported that the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway is involved in CQ-induced scratching behavior in mice. Previous studies have demonstrated that activation of N-methyl-d-aspartate receptors (NMDARs) induces NO production. Here we show that NMDAR antagonists significantly decrease CQ-induced scratching in mice while a non-effective dose of an NMDAR agonist potentiates the scratching behavior provoked by sub-effective doses of CQ. In contrast, combined pre-treatment with sub-effective doses of an NMDAR antagonist, MK-801, and the NO synthase inhibitor, L-N-nitro arginine methyl ester (L-NAME), decreases CQ-induced scratching behavior. While intradermal administration of CQ significantly increases the concentration of intradermal nitrite, the end product of NO metabolism, effective doses of intraperitoneal and intradermal MK-801 significantly decrease intradermal nitrite levels. Likewise, administration of an effective dose of L-NAME significantly decreases CQ-induced nitrite production. We conclude that the NMDA/NO pathway in the skin modulates CQ-induced scratching behavior. PMID:28119997

Metaplasticity contributes to memory formation in the hippocampus.

PubMed

Crestani, Ana P; Krueger, Jamie N; Barragan, Eden V; Nakazawa, Yuki; Nemes, Sonya E; Quillfeldt, Jorge A; Gray, John A; Wiltgen, Brian J

2018-05-16

Prior learning can modify the plasticity mechanisms that are used to encode new information. For example, NMDA receptor (NMDAR) activation is typically required for new spatial and contextual learning in the hippocampus. However, once animals have acquired this information, they can learn new tasks even if NMDARs are blocked. This finding suggests that behavioral training alters cellular plasticity mechanisms such that NMDARs are not required for subsequent learning. The mechanisms that mediate this change are currently unknown. To address this issue, we tested the idea that changes in intrinsic excitability (induced by learning) facilitate the encoding of new memories via metabotropic glutamate receptor (mGluR) activation. Consistent with this hypothesis, hippocampal neurons exhibited increases in intrinsic excitability after learning that lasted for several days. This increase was selective and only observed in neurons that were activated by the learning event. When animals were trained on a new task during this period, excitable neurons were reactivated and memory formation required the activation of mGluRs instead of NMDARs. These data suggest that increases in intrinsic excitability may serve as a metaplastic mechanism for memory formation.

N-Methyl-d-Aspartate (NMDA) Receptor Blockade Prevents Neuronal Death Induced by Zika Virus Infection.

PubMed

Costa, Vivian V; Del Sarto, Juliana L; Rocha, Rebeca F; Silva, Flavia R; Doria, Juliana G; Olmo, Isabella G; Marques, Rafael E; Queiroz-Junior, Celso M; Foureaux, Giselle; Araújo, Julia Maria S; Cramer, Allysson; Real, Ana Luíza C V; Ribeiro, Lucas S; Sardi, Silvia I; Ferreira, Anderson J; Machado, Fabiana S; de Oliveira, Antônio C; Teixeira, Antônio L; Nakaya, Helder I; Souza, Danielle G; Ribeiro, Fabiola M; Teixeira, Mauro M

2017-04-25

Zika virus (ZIKV) infection is a global health emergency that causes significant neurodegeneration. Neurodegenerative processes may be exacerbated by N -methyl-d-aspartate receptor (NMDAR)-dependent neuronal excitoxicity. Here, we have exploited the hypothesis that ZIKV-induced neurodegeneration can be rescued by blocking NMDA overstimulation with memantine. Our results show that ZIKV actively replicates in primary neurons and that virus replication is directly associated with massive neuronal cell death. Interestingly, treatment with memantine or other NMDAR blockers, including dizocilpine (MK-801), agmatine sulfate, or ifenprodil, prevents neuronal death without interfering with the ability of ZIKV to replicate in these cells. Moreover, in vivo experiments demonstrate that therapeutic memantine treatment prevents the increase of intraocular pressure (IOP) induced by infection and massively reduces neurodegeneration and microgliosis in the brain of infected mice. Our results indicate that the blockade of NMDARs by memantine provides potent neuroprotective effects against ZIKV-induced neuronal damage, suggesting it could be a viable treatment for patients at risk for ZIKV infection-induced neurodegeneration. IMPORTANCE Zika virus (ZIKV) infection is a global health emergency associated with serious neurological complications, including microcephaly and Guillain-Barré syndrome. Infection of experimental animals with ZIKV causes significant neuronal damage and microgliosis. Treatment with drugs that block NMDARs prevented neuronal damage both in vitro and in vivo These results suggest that overactivation of NMDARs contributes significantly to the neuronal damage induced by ZIKV infection, and this is amenable to inhibition by drug treatment. Copyright © 2017 Costa et al.

NR2C in the thalamic reticular nucleus; effects of the NR2C knockout.

PubMed

Zhang, Yuchun; Buonanno, Andres; Vertes, Robert P; Hoover, Walter B; Lisman, John E

2012-01-01

NMDAR antagonists can evoke delta frequency bursting in the nucleus reticularis of the thalamus (nRT). The mechanism of this oscillation was determined; antagonist blocks an NR2C-like conductance that has low Mg block at resting potential and thus can contribute a resting inward current in response to ambient glutamate. Block of this current hyperpolarizes the cell, deinactivating T-type Ca channels and thus triggering delta frequency bursting. The basis for assuming a NR2C-like conductance was that (1) transcripts for NR2C are abundant in the thalamus and (2) the current-voltage curve of the synaptically evoked NMDAR current has the low rectification characteristic of NR2C. In the current study, we have sought to determine whether the channels that generate the NMDAR current are NR2C-like or are actually comprised of receptors containing NR2C. We studied the current-voltage curve of synaptically evoked NMDAR current in the nRT of NR2C knockout mice. In wild-type mice, the current was weakly voltage dependent, as previously observed in rats. This weak rectification was absent in NR2C KO mice. In contrast, NR2C KO had no effect on the strongly rectifying NMDAR current in pyramidal cells of the prefrontal cortex. These results demonstrate that the low rectification normally observed in the nRT is due to NR2C.

NMDA receptor- and ERK-dependent histone methylation changes in the lateral amygdala bidirectionally regulate fear memory formation.

PubMed

Gupta-Agarwal, Swati; Jarome, Timothy J; Fernandez, Jordan; Lubin, Farah D

2014-07-01

It is well established that fear memory formation requires de novo gene transcription in the amygdala. We provide evidence that epigenetic mechanisms in the form of histone lysine methylation in the lateral amygdala (LA) are regulated by NMDA receptor (NMDAR) signaling and involved in gene transcription changes necessary for fear memory consolidation. Here we found increases in histone H3 lysine 9 dimethylation (H3K9me2) levels in the LA at 1 h following auditory fear conditioning, which continued to be temporally regulated up to 25 h following behavioral training. Additionally, we demonstrate that inhibiting the H3K9me2 histone lysine methyltransferase G9a (H/KMTs-G9a) in the LA impaired fear memory, while blocking the H3K9me2 histone lysine demethylase LSD1 (H/KDM-LSD1) enhanced fear memory, suggesting that H3K9me2 in the LA can bidirectionally regulate fear memory formation. Furthermore, we show that NMDAR activity differentially regulated the recruitment of H/KMT-G9a, H/KDM-LSD1, and subsequent H3K9me2 levels at a target gene promoter. This was largely regulated by GluN2B- but not GluN2A-containing NMDARs via ERK activation. Moreover, fear memory deficits associated with NMDAR or ERK blockade were successfully rescued through pharmacologically inhibiting LSD1, suggesting that enhancements of H3K9me2 levels within the LA can rescue fear memory impairments that result from hypofunctioning NMDARs or loss of ERK signaling. Together, the present study suggests that histone lysine methylation regulation in the LA via NMDAR-ERK-dependent signaling is involved in fear memory formation. © 2014 Gupta-Agarwal et al.; Published by Cold Spring Harbor Laboratory Press.

Dynamic NMDAR-mediated properties of place cells during the object place memory task.

PubMed

Faust, Thomas W; Robbiati, Sergio; Huerta, Tomás S; Huerta, Patricio T

2013-01-01

N-methyl-D-aspartate receptors (NMDAR) in the hippocampus participate in encoding and recalling the location of objects in the environment, but the ensemble mechanisms by which NMDARs mediate these processes have not been completely elucidated. To address this issue, we examined the firing patterns of place cells in the dorsal CA1 area of the hippocampus of mice (n = 7) that performed an object place memory (OPM) task, consisting of familiarization (T1), sample (T2), and choice (T3) trials, after systemic injection of 3-[(±)2-carboxypiperazin-4yl]propyl-1-phosphate (CPP), a specific NMDAR antagonist. Place cell properties under CPP (CPP-PCs) were compared to those after control saline injection (SAL-PCs) in the same mice. We analyzed place cells across the OPM task to determine whether they signaled the introduction or movement of objects by NMDAR-mediated changes of their spatial coding. On T2, when two objects were first introduced to a familiar chamber, CPP-PCs and SAL-PCs showed stable, vanishing or moving place fields in addition to changes in spatial information (SI). These metrics were comparable between groups. Remarkably, previously inactive CPP-PCs (with place fields emerging de novo on T2) had significantly weaker SI increases than SAL-PCs. On T3, when one object was moved, CPP-PCs showed reduced center-of-mass (COM) shift of their place fields. Indeed, a subset of SAL-PCs with large COM shifts (>7 cm) was largely absent in the CPP condition. Notably, for SAL-PCs that exhibited COM shifts, those initially close to the moving object followed the trajectory of the object, whereas those far from the object did the opposite. Our results strongly suggest that the SI changes and COM shifts of place fields that occur during the OPM task reflect key dynamic properties that are mediated by NMDARs and might be responsible for binding object identity with location.

Dynamic NMDAR-mediated properties of place cells during the object place memory task

PubMed Central

Faust, Thomas W.; Robbiati, Sergio; Huerta, Tomás S.; Huerta, Patricio T.

2013-01-01

N-methyl-D-aspartate receptors (NMDAR) in the hippocampus participate in encoding and recalling the location of objects in the environment, but the ensemble mechanisms by which NMDARs mediate these processes have not been completely elucidated. To address this issue, we examined the firing patterns of place cells in the dorsal CA1 area of the hippocampus of mice (n = 7) that performed an object place memory (OPM) task, consisting of familiarization (T1), sample (T2), and choice (T3) trials, after systemic injection of 3-[(±)2-carboxypiperazin-4yl]propyl-1-phosphate (CPP), a specific NMDAR antagonist. Place cell properties under CPP (CPP–PCs) were compared to those after control saline injection (SAL–PCs) in the same mice. We analyzed place cells across the OPM task to determine whether they signaled the introduction or movement of objects by NMDAR-mediated changes of their spatial coding. On T2, when two objects were first introduced to a familiar chamber, CPP–PCs and SAL–PCs showed stable, vanishing or moving place fields in addition to changes in spatial information (SI). These metrics were comparable between groups. Remarkably, previously inactive CPP–PCs (with place fields emerging de novo on T2) had significantly weaker SI increases than SAL–PCs. On T3, when one object was moved, CPP–PCs showed reduced center-of-mass (COM) shift of their place fields. Indeed, a subset of SAL–PCs with large COM shifts (>7 cm) was largely absent in the CPP condition. Notably, for SAL–PCs that exhibited COM shifts, those initially close to the moving object followed the trajectory of the object, whereas those far from the object did the opposite. Our results strongly suggest that the SI changes and COM shifts of place fields that occur during the OPM task reflect key dynamic properties that are mediated by NMDARs and might be responsible for binding object identity with location. PMID:24381547

Recovery of NMDA receptor currents from MK-801 blockade is accelerated by Mg2+ and memantine under conditions of agonist exposure

PubMed Central

McKay, Sean; Bengtson, C. Peter; Bading, Hilmar; Wyllie, David J.A.; Hardingham, Giles E.

2013-01-01

MK-801 is a use-dependent NMDA receptor open channel blocker with a very slow off-rate. These properties can be exploited to ‘pre-block’ a population of NMDARs, such as synaptic ones, enabling the selective activation of a different population, such as extrasynaptic NMDARs. However, the usefulness of this approach is dependent on the stability of MK-801 blockade after washout. We have revisited this issue, and confirm that recovery of NMDAR currents from MK-801 blockade is enhanced by channel opening by NMDA, and find that it is further increased when Mg2+ is also present. In the presence of Mg2+, 50% recovery from MK-801 blockade is achieved after 10′ of 100 μM NMDA, or 30′ of 15 μM NMDA exposure. In Mg2+-free medium, NMDA-induced MK-801 dissociation was found to be much slower. Memantine, another PCP-site antagonist, could substitute for Mg2+ in accelerating the unblock of MK-801 in the presence of NMDA. This suggests a model whereby, upon dissociation from its binding site in the pore, MK-801 is able to re-bind in a process antagonized by Mg2+ or another PCP-site antagonist. Finally we show that even when all NMDARs are pre-blocked by MK-801, incubation of neurons with 100 μM NMDA in the presence of Mg2+ for 2.5 h triggers sufficient unblocking to kill >80% of neurons. We conclude that while synaptic MK-801 ‘pre-block’ protocols are useful for pharmacologically assessing synaptic vs. extrasynaptic contributions to NMDAR currents, or studying short-term effects, it is problematic to use this technique to attempt to study the effects of long-term selective extrasynaptic NMDAR activation. This article is part of the Special Issue entitled ‘Glutamate Receptor-Dependent Synaptic Plasticity’. PMID:23402996

Impaired bidirectional NMDA receptor dependent synaptic plasticity in the dentate gyrus of adult female Fmr1 heterozygous knockout mice.

PubMed

Yau, S Y; Bostrom, C A; Chiu, J; Fontaine, C J; Sawchuk, S; Meconi, A; Wortman, R C; Truesdell, E; Truesdell, A; Chiu, C; Hryciw, B N; Eadie, B D; Ghilan, M; Christie, B R

2016-12-01

Fragile-X syndrome (FXS) is caused by the transcriptional repression of the Fmr1 gene resulting in loss of the Fragile-X mental retardation protein (FMRP). This leads to cognitive impairment in both male and female patients, however few studies have focused on the impact of FXS in females. Significant cognitive impairment has been reported in approximately 35% of women who exhibit a heterozygous Fmr1 gene mutation, however to date there is a paucity of information regarding the mechanistic underpinnings of these deficits. We, and others, have recently reported that there is significant impairment in N-methyl-d-aspartate receptor (NMDAR)-dependent long-term potentiation (LTP) and long-term depression (LTD) in the hippocampal dentate gyrus (DG) of male Fmr1 knock out mice. Here we examined if female mice displaying a heterozygous loss of the Fmr1 gene (Fmr1 +/- ) would exhibit similar impairments in DG-dependent spatial memory processing and NMDAR hypofunction. We found that Female Fmr1 +/- mice did not show impaired metabotropic glutamate receptor (mGluR)-LTD in the CA1 region, and could perform well on a temporal ordering task that is thought to involve this brain region. In contrast, female Fmr1 +/- mice showed impairments in a pattern separation task thought to involve the DG, and also displayed a significant impairment in both NMDAR-dependent LTD and LTP in this region. The LTP impairment could be rescued by administering the NMDAR co-agonist, glycine. Our data suggests that NMDAR hypofunction in the DG may partly contribute to learning and memory impairment in female Fmr1 +/- mice. Targeting NMDAR-dependent mechanisms may offer hope as a new therapeutic approach for treating female FXS patients with learning and memory impairments. Copyright © 2016 Elsevier Inc. All rights reserved.

Attenuation of ketamine-induced impairment in verbal learning and memory in healthy volunteers by the AMPA receptor potentiator PF-04958242.

PubMed

Ranganathan, M; DeMartinis, N; Huguenel, B; Gaudreault, F; Bednar, M M; Shaffer, C L; Gupta, S; Cahill, J; Sherif, M A; Mancuso, J; Zumpano, L; D'Souza, D C

2017-11-01

There is a need to develop treatments for cognitive impairment associated with schizophrenia (CIAS). The significant role played by N-methyl-d-aspartate receptors (NMDARs) in both the pathophysiology of schizophrenia and in neuronal plasticity suggests that facilitation of NMDAR function might ameliorate CIAS. One strategy to correct NMDAR hypofunction is to stimulate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) as AMPAR and NMDAR functioning are coupled and interdependent. In rats and nonhuman primates (NHP), AMPAR potentiators reduce spatial working memory deficits caused by the nonselective NMDAR antagonist ketamine. The current study assessed whether the AMPAR potentiator PF-04958242 would attenuate ketamine-induced deficits in verbal learning and memory in humans. Healthy male subjects (n=29) participated in two randomized treatment periods of daily placebo or PF-04958242 for 5 days separated by a washout period. On day 5 of each treatment period, subjects underwent a ketamine infusion for 75 min during which the effects of PF-04958242/placebo were assessed on ketamine-induced: (1) impairments in verbal learning and recall measured by the Hopkins Verbal Learning Test; (2) impairments in working memory on a CogState battery; and (3) psychotomimetic effects measured by the Positive and Negative Syndrome Scale and Clinician-Administered Dissociative Symptoms Scale. PF-04958242 significantly reduced ketamine-induced impairments in immediate recall and the 2-Back and spatial working memory tasks (CogState Battery), without significantly attenuating ketamine-induced psychotomimetic effects. There were no pharmacokinetic interactions between PF-04958242 and ketamine. Furthermore, PF-04958242 was well tolerated. 'High-impact' AMPAR potentiators like PF-04958242 may have a role in the treatment of the cognitive symptoms, but not the positive or negative symptoms, associated with schizophrenia. The excellent concordance between the preclinical (rat, NHP) and human studies with PF-04958242, and in silico modeling of AMPAR-NMDAR interactions in the hippocampus, highlights the translational value of this study.

Infralimbic GluN2A-Containing NMDA Receptors Modulate Reconsolidation of Cocaine Self-Administration Memory

PubMed Central

Hafenbreidel, Madalyn; Rafa Todd, Carolynn; Mueller, Devin

2017-01-01

Addiction is characterized by high relapse susceptibility, and relapse can be triggered by drug-associated cues. Cue presentation induces retrieval of the drug-cue memory, which becomes labile and must be reconsolidated into long-term storage. Repeated unpaired cue presentation, however, promotes extinction. Cue-reactivity can be reduced by blocking reconsolidation or facilitating extinction, which are mediated by NMDA receptors (NMDArs). However, the role of NMDArs in either process following self-administration is unclear. Thus, to determine their role in extinction, rats learned to self-administer cocaine before receiving injections of the NMDAr antagonist CPP immediately after four 45-min extinction sessions. During a subsequent 90-min extinction retention test, CPP-treated rats lever pressed less than saline-treated rats indicating that NMDAr blockade facilitated extinction or disrupted drug-cue memory reconsolidation. In addition, infusing CPP into the infralimbic medial prefrontal cortex (IL-mPFC), a structure implicated in extinction, before four 45-min or immediately after four 30min extinction sessions, had similar results during the extinction retention tests. Next, the GluN2A-selective antagonist NVP or GluN2B-selective antagonist Ro25 was infused into IL-mPFC or nucleus accumbens (NAc) shell, another structure implicated in extinction, after four 45-min extinction sessions. Blocking GluN2A-, but not GluN2B-, containing NMDArs, in IL-mPFC or NAc shell reduced lever pressing during the extinction retention tests. Finally, to dissociate reconsolidation from extinction, NVP was infused into IL-mPFC after four 10-min reactivation sessions, which resulted in reduced lever pressing during the retention test. These results indicate that IL-mPFC GluN2A-containing NMDArs modulate reconsolidation, and suggest a novel treatment strategy, as reducing cue reactivity could limit relapse susceptibility. PMID:28042872

Recovery of NMDA receptor currents from MK-801 blockade is accelerated by Mg2+ and memantine under conditions of agonist exposure.

PubMed

McKay, Sean; Bengtson, C Peter; Bading, Hilmar; Wyllie, David J A; Hardingham, Giles E

2013-11-01

MK-801 is a use-dependent NMDA receptor open channel blocker with a very slow off-rate. These properties can be exploited to 'pre-block' a population of NMDARs, such as synaptic ones, enabling the selective activation of a different population, such as extrasynaptic NMDARs. However, the usefulness of this approach is dependent on the stability of MK-801 blockade after washout. We have revisited this issue, and confirm that recovery of NMDAR currents from MK-801 blockade is enhanced by channel opening by NMDA, and find that it is further increased when Mg(2+) is also present. In the presence of Mg(2+), 50% recovery from MK-801 blockade is achieved after 10' of 100 μM NMDA, or 30' of 15 μM NMDA exposure. In Mg(2+)-free medium, NMDA-induced MK-801 dissociation was found to be much slower. Memantine, another PCP-site antagonist, could substitute for Mg(2+) in accelerating the unblock of MK-801 in the presence of NMDA. This suggests a model whereby, upon dissociation from its binding site in the pore, MK-801 is able to re-bind in a process antagonized by Mg(2+) or another PCP-site antagonist. Finally we show that even when all NMDARs are pre-blocked by MK-801, incubation of neurons with 100 μM NMDA in the presence of Mg(2+) for 2.5 h triggers sufficient unblocking to kill >80% of neurons. We conclude that while synaptic MK-801 'pre-block' protocols are useful for pharmacologically assessing synaptic vs. extrasynaptic contributions to NMDAR currents, or studying short-term effects, it is problematic to use this technique to attempt to study the effects of long-term selective extrasynaptic NMDAR activation. This article is part of the Special Issue entitled 'Glutamate Receptor-Dependent Synaptic Plasticity'. Copyright © 2013 Elsevier Ltd. All rights reserved.

Cannabidiol Attenuates Sensorimotor Gating Disruption and Molecular Changes Induced by Chronic Antagonism of NMDA receptors in Mice

PubMed Central

Issy, Ana Carolina; Ferreira, Frederico R.; Viveros, Maria-Paz; Del Bel, Elaine A.; Guimarães, Francisco S.

2015-01-01

Background: Preclinical and clinical data suggest that cannabidiol (CBD), a major non-psychotomimetic compound from Cannabis sativa, induces antipsychotic-like effects. However, the antipsychotic properties of repeated CBD treatment have been poorly investigated. Behavioral changes induced by repeated treatment with glutamate N-methyl-D-aspartate receptor (NMDAR) antagonists have been proposed as an animal model of schizophrenia-like signs. In the present study, we evaluated if repeated treatment with CBD would attenuate the behavioral and molecular modifications induced by chronic administration of one of these antagonists, MK-801. Methods: Male C57BL/6J mice received daily i.p. injections of MK-801 (0.1, 0.5, or 1mg/kg) for 14, 21, or 28 days. Twenty-four hours after the last injection, animals were submitted to the prepulse inhibition (PPI) test. After that, we investigated if repeated treatment with CBD (15, 30, and 60mg/kg) would attenuate the PPI impairment induced by chronic treatment with MK-801 (1mg/kg; 28 days). CBD treatment began on the 6th day after the start of MK-801 administration and continued until the end of the treatment. Immediately after the PPI, the mice brains were removed and processed to evaluate the molecular changes. We measured changes in FosB/ΔFosB and parvalbumin (PV) expression, a marker of neuronal activity and a calcium-binding protein expressed in a subclass of GABAergic interneurons, respectively. Changes in mRNA expression of the NMDAR GluN1 subunit gene (GRN1) were also evaluated. CBD effects were compared to those induced by the atypical antipsychotic clozapine. Results: MK-801 administration at the dose of 1mg/kg for 28 days impaired PPI responses. Chronic treatment with CBD (30 and 60mg/kg) attenuated PPI impairment. MK-801 treatment increased FosB/ΔFosB expression and decreased PV expression in the medial prefrontal cortex. A decreased mRNA level of GRN1 in the hippocampus was also observed. All the molecular changes were attenuated by CBD. CBD by itself did not induce any effect. Moreover, CBD effects were similar to those induced by repeated clozapine treatment. Conclusions: These results indicate that repeated treatment with CBD, similar to clozapine, reverses the psychotomimetic-like effects and attenuates molecular changes observed after chronic administration of an NMDAR antagonist. These data support the view that CBD may have antipsychotic properties. PMID:25618402

Cannabidiol attenuates sensorimotor gating disruption and molecular changes induced by chronic antagonism of NMDA receptors in mice.

PubMed

Gomes, Felipe V; Issy, Ana Carolina; Ferreira, Frederico R; Viveros, Maria-Paz; Del Bel, Elaine A; Guimarães, Francisco S

2014-10-31

Preclinical and clinical data suggest that cannabidiol (CBD), a major non-psychotomimetic compound from Cannabis sativa, induces antipsychotic-like effects. However, the antipsychotic properties of repeated CBD treatment have been poorly investigated. Behavioral changes induced by repeated treatment with glutamate N-methyl-D-aspartate receptor (NMDAR) antagonists have been proposed as an animal model of schizophrenia-like signs. In the present study, we evaluated if repeated treatment with CBD would attenuate the behavioral and molecular modifications induced by chronic administration of one of these antagonists, MK-801. Male C57BL/6J mice received daily i.p. injections of MK-801 (0.1, 0.5, or 1mg/kg) for 14, 21, or 28 days. Twenty-four hours after the last injection, animals were submitted to the prepulse inhibition (PPI) test. After that, we investigated if repeated treatment with CBD (15, 30, and 60mg/kg) would attenuate the PPI impairment induced by chronic treatment with MK-801 (1mg/kg; 28 days). CBD treatment began on the 6th day after the start of MK-801 administration and continued until the end of the treatment. Immediately after the PPI, the mice brains were removed and processed to evaluate the molecular changes. We measured changes in FosB/ΔFosB and parvalbumin (PV) expression, a marker of neuronal activity and a calcium-binding protein expressed in a subclass of GABAergic interneurons, respectively. Changes in mRNA expression of the NMDAR GluN1 subunit gene (GRN1) were also evaluated. CBD effects were compared to those induced by the atypical antipsychotic clozapine. MK-801 administration at the dose of 1mg/kg for 28 days impaired PPI responses. Chronic treatment with CBD (30 and 60mg/kg) attenuated PPI impairment. MK-801 treatment increased FosB/ΔFosB expression and decreased PV expression in the medial prefrontal cortex. A decreased mRNA level of GRN1 in the hippocampus was also observed. All the molecular changes were attenuated by CBD. CBD by itself did not induce any effect. Moreover, CBD effects were similar to those induced by repeated clozapine treatment. These results indicate that repeated treatment with CBD, similar to clozapine, reverses the psychotomimetic-like effects and attenuates molecular changes observed after chronic administration of an NMDAR antagonist. These data support the view that CBD may have antipsychotic properties. © The Author 2015. Published by Oxford University Press on behalf of CINP.

Neural oscillations as a bridge between glutamatergic system and emotional behaviors in simulated microgravity-induced mice.

PubMed

Shang, Xueliang; Xu, Bo; Li, Qun; Zhai, Baohui; Xu, Xiaxia; Zhang, Tao

2017-01-15

This study aims to investigate if neural oscillations can play a role as a bridge between the alteration of glutamatergic system and emotional behaviors in simulated microgravity (SM) mice. Adult male C57BL/6J mice were randomly divided into two groups: SM and control groups. The animal model was established by hindlimb unloading (HU). The mice were exposed to HU continued for 14days. Weight and sucrose consumption were measured. The degree of anxious and depressive was evaluated by Open field test and Elevated plus maze test. Local field potentials were recorded in the hippocampal perforant path (PP) and dentate gyrus (DG) regions. The NMDAR2A/2B (NR2A/2B) subunits expression and glutamate level were measured by Western and high performance liquid chromatography (HPLC), respectively. After 14days, SM mice exhibited depressive-like and anxiety-like behaviors, while the expression of NR2A/2B subunits and the glutamate level were significantly decreased in the SM group. Moreover, the power distribution of theta (3-8Hz) was decreased by HU, which further significantly attenuated the identical-frequency strength of phase synchronization and the neural information flow at theta rhythm on the PP-DG pathway. The theta-gamma phase synchronization strength was also significantly reduced by HU. The data imply that the neural oscillations measurements is a sign of the emotional behaviors impairment and the glutamatergic system change induced by HU. Copyright © 2016 Elsevier B.V. All rights reserved.

78. Augmenting NMDA Receptor Signaling Enhances Working Memory and Alters Gamma Oscillations in Patients With Schizophrenia

PubMed Central

Forsyth, Jennifer; Bachman, Peter; Asarnow, Robert

2017-01-01

Abstract Background: Gamma band oscillations (30–80 Hz) are associated with numerous sensory and higher cognitive functions and are abnormal in patients with schizophrenia. Glutamate signaling at the N-methyl-D-aspartate receptor (NMDAR) is theorized to play a key role in the pathophysiology of schizophrenia and NMDAR antagonists disrupt working memory and gamma oscillations in healthy individuals. It has therefore been suggested that NMDAR dysfunction may contribute to abnormalities in gamma oscillations and working memory in schizophrenia. In the current study, we examined the effects of acutely augmenting NMDAR signaling using the NMDAR agonist, d-cycloserine (DCS), on working memory and gamma power in patients with schizophrenia. Methods: In a double-blind design, patients with schizophrenia were randomized to receive a single dose of 100 mg DCS (SZ-DCS; n = 24) or Placebo (SZ-PLC; n = 21). Patients completed a spatial n-back task involving a 0-back control condition and 1-back and 2-back working memory loads while undergoing EEG recording. Gamma power (30–80 Hz) during the 0-back condition assessed gamma power associated with basic perceptual, motor, and attentive processes. Change in gamma power for correct working memory trials relative to the 0-back condition assessed gamma power associated with working memory function. Results: Among patients who performed above chance (SZ-DCS = 17, SZ-PLC = 16), patients who received DCS showed superior working memory performance compared to patients who received Placebo. Gamma power during the 0-back control condition was similar between SZ-DCS and SZ-PLC who performed above chance. However, gamma power associated with working memory function was significantly suppressed in SZ-DCS compared to SZ-PLC, particularly over frontal right channels. In addition, whereas higher working memory gamma power over frontal right channels was associated with better working memory performance in SZ-PLC, this relationship was not evident in SZ-DCS. Conclusion: Results suggest that augmenting NMDAR signaling enhanced working memory performance and suppressed gamma activity associated with working memory function in patients with schizophrenia. Given prior reports that schizophrenia patients may utilize excessive gamma power for successful working memory performance, these findings suggest that augmenting NMDAR signaling may improve the efficiency of neural encoding for successful working memory function in schizophrenia.

Mechanism of the modulation of BK potassium channel complexes with different auxiliary subunit compositions by the omega-3 fatty acid DHA.

PubMed

Hoshi, Toshinori; Tian, Yutao; Xu, Rong; Heinemann, Stefan H; Hou, Shangwei

2013-03-19

Large-conductance Ca(2+)- and voltage-activated K(+) (BK) channels are well known for their functional versatility, which is bestowed in part by their rich modulatory repertoire. We recently showed that long-chain omega-3 polyunsaturated fatty acids such as docosahexaenoic acid (DHA) found in oily fish lower blood pressure by activating vascular BK channels made of Slo1+β1 subunits. Here we examined the action of DHA on BK channels with different auxiliary subunit compositions. Neuronal Slo1+β4 channels were just as well activated by DHA as vascular Slo1+β1 channels. In contrast, the stimulatory effect of DHA was much smaller in Slo1+β2, Slo1+LRRC26 (γ1), and Slo1 channels without auxiliary subunits. Mutagenesis of β1, β2, and β4 showed that the large effect of DHA in Slo1+β1 and Slo1+β4 is conferred by the presence of two residues, one in the N terminus and the other in the first transmembrane segment of the β1 and β4 subunits. Transfer of this amino acid pair from β1 or β4 to β2 introduces a large response to DHA in Slo1+β2. The presence of a pair of oppositely charged residues at the aforementioned positions in β subunits is associated with a large response to DHA. The Slo1 auxiliary subunits are expressed in a highly tissue-dependent fashion. Thus, the subunit composition-dependent stimulation by DHA demonstrates that BK channels are effectors of omega-3 fatty acids with marked tissue specificity.

Histidinoalanine, a naturally occurring cross-link derived from phosphoserine and histidine residues in mineral-binding phosphoproteins.

PubMed

Marsh, M E

1986-05-06

Native mineral-containing phosphoprotein particles were isolated from the Heterodont bivalve Macrocallista nimbosa. The native particles are discrete structures about 40 nm in diameter which migrate as a single band during electrophoresis in agarose gels. Removal of the mineral component with ethylenediaminetetraacetic acid dissociates the native protein into nonidentical subunits. The lower molecular weight subunits, representing 8% of the total protein, were obtained by differential centrifugation. The native protein is characterized by a high content of aspartic acid, phosphoserine, phosphothreonine, histidine, and the bifunctional cross-linking residue histidinoalanine. The low molecular weight subunits have the same amino acid composition except for a reduction in histidinoalanine and a corresponding increase in phosphoserine and histidine residues, demonstrating that the alanine portion of the cross-link is derived from phosphoserine residues. Ion-exchange chromatography and molecular sieve chromatography show that the low molecular weight subunits have a similar charge density but differ in molecular weight, and the relative mobilities of the subunits on agarose gels indicate that they are polymers of a single phosphoprotein molecule. The minimum molecular weight of the monomer is about 140 000 on the basis of the amino acid composition. The high molecular weight subunits are rich in histidinoalanine and too large to be resolved by either molecular sieve chromatography or gel electrophoresis. On the basis of the ultrastructural, electrophoretic, chromatographic, and compositional evidence, native phosphoprotein particles are composed of subunits ionically cross-linked via divalent cations. These subunits are variable molecular weight aggregates of a single phosphoprotein molecule covalently cross-linked via histidinoalanine residues. Evidence for a nonenzymatic cross-linking mechanism is discussed.

Subunit compositions of Arabidopsis RNA polymerases I and III reveal Pol I- and Pol III-specific forms of the AC40 subunit and alternative forms of the C53 subunit

PubMed Central

Ream, Thomas S.; Haag, Jeremy R.; Pontvianne, Frederic; Nicora, Carrie D.; Norbeck, Angela D.; Paša-Tolić, Ljiljana; Pikaard, Craig S.

2015-01-01

Using affinity purification and mass spectrometry, we identified the subunits of Arabidopsis thaliana multisubunit RNA polymerases I and III (abbreviated as Pol I and Pol III), the first analysis of their physical compositions in plants. In all eukaryotes examined to date, AC40 and AC19 subunits are common to Pol I (a.k.a. Pol A) and Pol III (a.k.a. Pol C) and are encoded by single genes. Surprisingly, A. thaliana and related species express two distinct AC40 paralogs, one of which assembles into Pol I and the other of which assembles into Pol III. Changes at eight amino acid positions correlate with the functional divergence of Pol I- and Pol III-specific AC40 paralogs. Two genes encode homologs of the yeast C53 subunit and either protein can assemble into Pol III. By contrast, only one of two potential C17 variants, and one of two potential C31 variants were detected in Pol III. We introduce a new nomenclature system for plant Pol I and Pol III subunits in which the 12 subunits that are structurally and functionally homologous among Pols I through V are assigned equivalent numbers. PMID:25813043

Determination of the Subunit Molecular Mass and Composition of Alcohol Dehydrogenase by SDS-PAGE

ERIC Educational Resources Information Center

Nash, Barbara T.

2007-01-01

SDS-PAGE is a simple, rapid technique that has many uses in biochemistry and is readily adaptable to the undergraduate laboratory. It is, however, a technique prone to several types of procedural pitfalls. This article describes the use of SDS-PAGE to determine the subunit molecular mass and composition of yeast alcohol dehydrogenase employing…

Molecular and Behavioral Changes Associated with Adult Hippocampus-Specific SynGAP1 Knockout

ERIC Educational Resources Information Center

Muhia, Mary; Willadt, Silvia; Yee, Benjamin K.; Feldon, Joram; Paterna, Jean-Charles; Schwendener, Severin; Vogt, Kaspar; Kennedy, Mary B.; Knuesel, Irene

2012-01-01

The synaptic Ras/Rap-GTPase-activating protein (SynGAP1) plays a unique role in regulating specific downstream intracellular events in response to N-methyl-D-aspartate receptor (NMDAR) activation. Constitutive heterozygous loss of SynGAP1 disrupts NMDAR-mediated physiological and behavioral processes, but the disruptions might be of developmental…

Genetic Inactivation of D-Amino Acid Oxidase Enhances Extinction and Reversal Learning in Mice

ERIC Educational Resources Information Center

Labrie, Viviane; Duffy, Steven; Wang, Wei; Barger, Steven W.; Baker, Glen B.; Roder, John C.

2009-01-01

Activation of the N-methyl-d-aspartate receptor (NMDAR) glycine site has been shown to accelerate adaptive forms of learning that may benefit psychopathologies involving cognitive and perseverative disturbances. In this study, the effects of increasing the brain levels of the endogenous NMDAR glycine site agonist D-serine, through the genetic…

Recent insights into the mode of action of memantine and ketamine

PubMed Central

Johnson, Jon W.; Glasgow, Nathan G.; Povysheva, Nadezhda V.

2014-01-01

The clinical benefits of the glutamate receptor antagonists memantine and ketamine have helped sustain optimism that glutamate receptors represent viable targets for development of therapeutic drugs. Both memantine and ketamine antagonize N-methyl-d-aspartate receptors (NMDARs), a glutamate receptor subfamily, by blocking the receptor-associated ion channel. Although many of the basic characteristics of NMDAR inhibition by memantine and ketamine appear similar, their effects on humans and to a lesser extent on rodents are strongly divergent. Some recent research suggests that preferential inhibition by memantine and ketamine of distinct NMDAR subpopulations may contribute to the drugs' differential clinical effects. Here we review studies that shed light on possible explanations for differences between the effects of memantine and ketamine. PMID:25462293

Relationship between the sensory-determined astringency and the flavanolic composition of red wines.

PubMed

Quijada-Morín, Natalia; Regueiro, Jorge; Simal-Gándara, Jesús; Tomás, Esperanza; Rivas-Gonzalo, Julián C; Escribano-Bailón, M Teresa

2012-12-19

The relationship between the proanthocyanidin profile and the perceived astringency was assessed in 13 commercial Tempranillo red wines. The concentration and compositional information were obtained by liquid chromatography with diode array detection coupled to electrospray ionization mass spectrometry after acid-catalyzed depolymerization of wine proanthocyanidins in the presence of excess phloroglucinol. Statistical analysis of the results showed significant correlations between sensory and chemical determinations. Astringency was more affected by the subunit composition than by the total concentration or the average degree of polymerization of wine proanthocyanidins. Higher proportions of epicatechin (EC) subunits in extension positions and gallocatechin (GC) subunits in terminal positions were shown to increase astringency. On the contrary, the amount of epigallocatechin (EGC) in both extension and terminal positions was negatively correlated with the perceived astringency.

Effects of transgene-encoded high-molecular weight glutenin proteins in wheat flour blends and sponge and dough baking

USDA-ARS?s Scientific Manuscript database

HMW glutenin subunits are the most important determinants of wheat (Triticum aestivum L.) bread-making quality, and subunit composition explains a large percentage of the variability observed between genotypes. Experiments were designed to elevate expression of a key native HMW glutenin subunit (1D...

Anti-NMDA receptor encephalitis: clinical characteristics, predictors of outcome and the knowledge gap in southwest China.

PubMed

Wang, W; Li, J-M; Hu, F-Y; Wang, R; Hong, Z; He, L; Zhou, D

2016-03-01

The aim was to analyse the clinical profiles and outcomes of patients with anti- N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis in China. A retrospective study of anti-NMDAR encephalitis in China was performed between June 2011 and June 2014. The clinical characteristics and predictors of poor outcome were determined. A total of 51 patients with a definitive diagnosis of anti-NMDAR encephalitis were included in this study. Four of them were surgically confirmed to have a neoplasm. Thirty-two patients, amongst whom 24 were female, presented with psychiatric disorder as the initial symptom, whereas 14 patients, of whom nine were male, presented with seizure as the initial symptom (P = 0.011). Twenty-nine patients (56.86%) were initially misdiagnosed with psychosis, viral encephalitis or other diseases, and 58.8% of the patients experienced at least one type of complication. It typically took 3 weeks before these patients were admitted to our hospital and another 2 weeks before the correct diagnosis was made. Forty-one patients (80%) reached a good outcome; 10 patients (20%) had a poor outcome. Older age, extended hospital stay, memory deficits, decreased consciousness, central hypoventilation, complications and abnormal cerebrospinal fluid results were associated with poor outcome (P < 0.05). Female patients more frequently initially present with psychiatric disorder but male patients more frequently initially present with seizure. Patients with anti-NMDAR encephalitis in China have a lower incidence of neoplasm. Nevertheless, this study reveals several challenges in treating anti-NMDAR encephalitis in China that may contribute to poor outcome. © 2015 EAN.

Compromised NMDA/Glutamate Receptor Expression in Dopaminergic Neurons Impairs Instrumental Learning, But Not Pavlovian Goal Tracking or Sign Tracking

PubMed

James, Alex S; Pennington, Zachary T; Tran, Phu; Jentsch, James David

2015-01-01

Two theories regarding the role for dopamine neurons in learning include the concepts that their activity serves as a (1) mechanism that confers incentive salience onto rewards and associated cues and/or (2) contingency teaching signal reflecting reward prediction error. While both theories are provocative, the causal role for dopamine cell activity in either mechanism remains controversial. In this study mice that either fully or partially lacked NMDARs in dopamine neurons exclusively, as well as appropriate controls, were evaluated for reward-related learning; this experimental design allowed for a test of the premise that NMDA/glutamate receptor (NMDAR)-mediated mechanisms in dopamine neurons, including NMDA-dependent regulation of phasic discharge activity of these cells, modulate either the instrumental learning processes or the likelihood of pavlovian cues to become highly motivating incentive stimuli that directly attract behavior. Loss of NMDARs in dopamine neurons did not significantly affect baseline dopamine utilization in the striatum, novelty evoked locomotor behavior, or consumption of a freely available, palatable food solution. On the other hand, animals lacking NMDARs in dopamine cells exhibited a selective reduction in reinforced lever responses that emerged over the course of instrumental learning. Loss of receptor expression did not, however, influence the likelihood of an animal acquiring a pavlovian conditional response associated with attribution of incentive salience to reward-paired cues (sign tracking). These data support the view that reductions in NMDAR signaling in dopamine neurons affect instrumental reward-related learning but do not lend support to hypotheses that suggest that the behavioral significance of this signaling includes incentive salience attribution.

Has an Angel Shown the Way? Etiological and Therapeutic Implications of the PCP/NMDA Model of Schizophrenia

PubMed Central

Javitt, Daniel C.

2012-01-01

Over the last 20 years, glutamatergic models of schizophrenia have become increasingly accepted as etiopathological models of schizophrenia, based on the observation that phencyclidine (PCP) induces a schizophrenia-like psychosis by blocking neurotransmission at N-methyl-D-aspartate (NMDA)-type glutamate receptors. This article reviews developments in two key predictions of the model: first, that neurocognitive deficits in schizophrenia should follow the pattern of deficit predicted based on underlying NMDAR dysfunction and, second, that agents that stimulate NMDAR function should be therapeutically beneficial. As opposed to dopamine receptors, NMDAR are widely distributed throughout the brain, including subcortical as well as cortical brain regions, and sensory as well as association cortex. Studies over the past 20 years have documented severe sensory dysfunction in schizophrenia using behavioral, neurophysiological, and functional brain imaging approaches, including impaired generation of key sensory-related potentials such as mismatch negativity and visual P1 potentials. Similar deficits are observed in humans following administration of NMDAR antagonists such as ketamine in either humans or animal models. Sensory dysfunction, in turn, predicts impairments in higher order cognitive functions such as auditory or visual emotion recognition. Treatment studies have been performed with compounds acting directly at the NMDAR glycine site, such as glycine, D-serine, or D-cycloserine, and, more recently, with high-affinity glycine transport inhibitors such as RG1678 (Roche). More limited studies have been performed with compounds targeting the redox site. Overall, these compounds have been found to induce significant beneficial effects on persistent symptoms, suggesting novel approaches for treatment and prevention of schizophrenia. PMID:22987851

Effects of memantine on the excitation-inhibition balance in prefrontal cortex.

PubMed

Povysheva, Nadezhda V; Johnson, Jon W

2016-12-01

Memantine is one of the few drugs currently approved for treatment of Alzheimer's disease (AD). The clinical effects of memantine are thought to be associated with inhibition of NMDA receptors (NMDARs). Surprisingly, other open-channel NMDAR blockers have unacceptable side effects that prevent their consideration for AD treatment. One of the mechanisms proposed to explain the therapeutic benefits of memantine involves preferential decrease of excitatory drive to inhibitory neurons in the cortical circuitry and consequent changes in balance between excitation and inhibition (E/I). In this study we addressed effects of memantine on E/I balance in the prefrontal cortex (PFC). We found that a moderate concentration of memantine shifted E/I balance away from inhibition in the PFC circuitry. Indeed, memantine decreased the frequency and amplitude of spontaneous inhibitory postsynaptic currents in pyramidal neurons while leaving spontaneous excitatory postsynaptic currents unaffected. These circuitry effects of memantine were occluded by the competitive NMDAR inhibitor AP-5, and thus are associated with NMDAR inhibition. We also found that memantine decreased feed-forward disynaptic inhibitory input to pyramidal neurons, which is thought to be mediated by parvalbumin (PV)-positive interneurons. Accordingly, memantine caused a greater decrease of the amplitude of NMDAR-mediated synaptic responses in PV-positive interneurons than in pyramidal neurons. Finally, memantine reduced firing activity in PV-positive interneurons while increasing firing in pyramidal neurons. This study elucidates a novel mechanism of action of memantine associated with shifting of the E/I balance away from inhibition in neocortical circuitry, and provides important insights for AD drug development. Copyright © 2016 Elsevier Inc. All rights reserved.

Effects of memantine on the excitation-inhibition balance in prefrontal cortex

PubMed Central

Povysheva, Nadezhda V.; Johnson, Jon W.

2016-01-01

Memantine is one of the few drugs currently approved for treatment of Alzheimer’s disease (AD). The clinical effects of memantine are thought to be associated with inhibition of NMDA receptors (NMDARs). Surprisingly, other open-channel NMDAR blockers have unacceptable side effects that prevent their consideration for AD treatment. One of the mechanisms proposed to explain the therapeutic benefits of memantine involves preferential decrease of excitatory drive to inhibitory neurons in the cortical circuitry and consequent changes in balance between excitation and inhibition (E/I). In this study we addressed effects of memantine on E/I balance in the prefrontal cortex (PFC). We found that a moderate concentration of memantine shifted E/I balance away from inhibition in the PFC circuitry. Indeed, memantine decreased the frequency and amplitude of spontaneous inhibitory postsynaptic currents in pyramidal neurons while leaving spontaneous excitatory postsynaptic currents unaffected. These circuitry effects of memantine were occluded by the competitive NMDAR inhibitor AP-5, and thus are associated with NMDAR inhibition. We also found that memantine decreased feed-forward disynaptic inhibitory input to pyramidal neurons, which is thought to be mediated by parvalbumin (PV)-positive interneurons. Accordingly, memantine caused a greater decrease of the amplitude of NMDAR-mediated synaptic responses in PV-positive interneurons than in pyramidal neurons. Finally, memantine reduced firing activity in PV-positive interneurons while increasing firing in pyramidal neurons. This study elucidates a novel mechanism of action of memantine associated with shifting of the E/I balance away from inhibition in neocortical circuitry, and provides important insights for AD drug development. PMID:27546057

Podocyte Glutamatergic Signaling Contributes to the Function of the Glomerular Filtration Barrier

PubMed Central

Giardino, Laura; Armelloni, Silvia; Corbelli, Alessandro; Mattinzoli, Deborah; Zennaro, Cristina; Guerrot, Dominique; Tourrel, Fabien; Ikehata, Masami; Li, Min; Berra, Silvia; Carraro, Michele; Messa, Piergiorgio

2009-01-01

Podocytes possess the complete machinery for glutamatergic signaling, raising the possibility that neuron-like signaling contributes to glomerular function. To test this, we studied mice and cells lacking Rab3A, a small GTPase that regulates glutamate exocytosis. In addition, we blocked the glutamate ionotropic N-methyl-d-aspartate receptor (NMDAR) with specific antagonists. In mice, the absence of Rab3A and blockade of NMDAR both associated with an increased urinary albumin/creatinine ratio. In humans, NMDAR blockade, obtained by addition of ketamine to general anesthesia, also had an albuminuric effect. In vitro, Rab3A-null podocytes displayed a dysregulated release of glutamate with higher rates of spontaneous exocytosis, explained by a reduction in Rab3A effectors resulting in freedom of vesicles from the actin cytoskeleton. In addition, NMDAR antagonism led to profound cytoskeletal remodeling and redistribution of nephrin in cultured podocytes; the addition of the agonist NMDA reversed these changes. In summary, these results suggest that glutamatergic signaling driven by podocytes contributes to the integrity of the glomerular filtration barrier and that derangements in this signaling may lead to proteinuric renal diseases. PMID:19578006

NMDAR inhibition-independent antidepressant actions of ketamine metabolites

PubMed Central

Zanos, Panos; Moaddel, Ruin; Morris, Patrick J.; Georgiou, Polymnia; Fischell, Jonathan; Elmer, Greg I.; Alkondon, Manickavasagom; Yuan, Peixiong; Pribut, Heather J.; Singh, Nagendra S.; Dossou, Katina S.S.; Fang, Yuhong; Huang, Xi-Ping; Mayo, Cheryl L.; Wainer, Irving W.; Albuquerque, Edson X.; Thompson, Scott M.; Thomas, Craig J.; Zarate, Carlos A.; Gould, Todd D.

2016-01-01

Major depressive disorder afflicts ~16 percent of the world population at some point in their lives. Despite a number of available monoaminergic-based antidepressants, most patients require many weeks, if not months, to respond to these treatments, and many patients never attain sustained remission of their symptoms. The non-competitive glutamatergic N-methyl-D-aspartate receptor (NMDAR) antagonist, (R,S)-ketamine (ketamine), exerts rapid and sustained antidepressant effects following a single dose in depressed patients. Here we show that the metabolism of ketamine to (2S,6S;2R,6R)-hydroxynorketamine (HNK) is essential for its antidepressant effects, and that the (2R,6R)-HNK enantiomer exerts behavioural, electroencephalographic, electrophysiological and cellular antidepressant actions in vivo. Notably, we demonstrate that these antidepressant actions are NMDAR inhibition-independent but they involve early and sustained α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor activation. We also establish that (2R,6R)-HNK lacks ketamine-related side-effects. Our results indicate a novel mechanism underlying ketamine’s unique antidepressant properties, which involves the required activity of a distinct metabolite and is independent of NMDAR inhibition. These findings have relevance for the development of next generation, rapid-acting antidepressants. PMID:27144355

A Monte Carlo model reveals independent signaling at central glutamatergic synapses.

PubMed Central

Franks, Kevin M; Bartol, Thomas M; Sejnowski, Terrence J

2002-01-01

We have developed a biophysically realistic model of receptor activation at an idealized central glutamatergic synapse that uses Monte Carlo techniques to simulate the stochastic nature of transmission following release of a single synaptic vesicle. For the a synapse with 80 AMPA and 20 NMDA receptors, a single quantum, with 3000 glutamate molecules, opened approximately 3 NMDARs and 20 AMPARs. The number of open receptors varied directly with the total number of receptors, and the fraction of open receptors did not depend on the ratio of co-localized AMPARs and NMDARs. Variability decreased with increases in either total receptor number or quantal size, and differences between the variability of AMPAR and NMDAR responses were due solely to unequal numbers of receptors at the synapse. Despite NMDARs having a much higher affinity for glutamate than AMPARs, quantal release resulted in similar occupancy levels in both receptor types. Receptor activation increased with number of transmitter molecules released or total receptor number, whereas occupancy levels were only dependent on quantal size. Tortuous diffusion spaces reduced the extent of spillover and the activation of extrasynaptic receptors. These results support the conclusion that signaling is spatially independent within and between central glutamatergic synapses. PMID:12414671

Anti-N-Methyl-D-aspartate Receptor Encephalitis: A Severe, Potentially Reversible Autoimmune Encephalitis.

PubMed

Liu, Cai-Yun; Zhu, Jie; Zheng, Xiang-Yu; Ma, Chi; Wang, Xu

2017-01-01

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is potentially lethal, but it is also a treatable autoimmune disorder characterized by prominent psychiatric and neurologic symptoms. It is often accompanied with teratoma or other neoplasm, especially in female patients. Anti-NMDAR antibodies in cerebrospinal fluid (CSF) and serum are characteristic features of the disease, thereby suggesting a pathogenic role in the disease. Here, we summarize recent studies that have clearly documented that both clinical manifestations and the antibodies may contribute to early diagnosis and multidisciplinary care. The clinical course of the disorder is reversible and the relapse could occur in some patients. Anti-NMDAR encephalitis coexisting with demyelinating disorders makes the diagnosis more complex; thus, clinicians should be aware of the overlapping diseases.

Anti-N-Methyl-D-aspartate Receptor Encephalitis: A Severe, Potentially Reversible Autoimmune Encephalitis

PubMed Central

Liu, Cai-yun; Zheng, Xiang-Yu; Ma, Chi

2017-01-01

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is potentially lethal, but it is also a treatable autoimmune disorder characterized by prominent psychiatric and neurologic symptoms. It is often accompanied with teratoma or other neoplasm, especially in female patients. Anti-NMDAR antibodies in cerebrospinal fluid (CSF) and serum are characteristic features of the disease, thereby suggesting a pathogenic role in the disease. Here, we summarize recent studies that have clearly documented that both clinical manifestations and the antibodies may contribute to early diagnosis and multidisciplinary care. The clinical course of the disorder is reversible and the relapse could occur in some patients. Anti-NMDAR encephalitis coexisting with demyelinating disorders makes the diagnosis more complex; thus, clinicians should be aware of the overlapping diseases. PMID:28698711

Subunit compositions of Arabidopsis RNA polymerases I and III reveal Pol I- and Pol III-specific forms of the AC40 subunit and alternative forms of the C53 subunit

DOE PAGES

Ream, Thomas S.; Haag, Jeremy R.; Pontvianne, Frederic; ...

2015-05-02

Using affinity purification and mass spectrometry, we identified the subunits of Arabidopsis thaliana multisubunit RNA Polymerases I and III (abbreviated as Pol I and Pol III), providing the first description of their physical compositions in plants. AC40 and AC19 subunits are typically common to Pol I (a.k.a. Pol A) and Pol III (a.k.a. Pol C) and are encoded by single genes whose mutation, in humans, is a cause of the craniofacial disorder, Treacher-Collins Syndrome. Surprisingly, A. thaliana, and related species, express two distinct AC40 paralogs, one of which assembles into Pol I and the other of which assembles into Polmore » III. Changes at eight amino acid positions correlate with this functional divergence of Pol I and Pol III-specific AC40 paralogs. Two genes encode homologs of the yeast C53 subunit, and either variant can assemble into Pol III. By contrast, only one of two potential C17 variants, and one of two potential C31 variants were detected in Pol III. We introduce a new nomenclature system for plant Pol I and Pol III subunits in which the twelve subunits that are structurally and functionally homologous among Pols I through V are assigned equivalent numbers.« less

Subunit compositions of Arabidopsis RNA polymerases I and III reveal Pol I- and Pol III-specific forms of the AC40 subunit and alternative forms of the C53 subunit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ream, Thomas S.; Haag, Jeremy R.; Pontvianne, Frederic

Using affinity purification and mass spectrometry, we identified the subunits of Arabidopsis thaliana multisubunit RNA Polymerases I and III (abbreviated as Pol I and Pol III), providing the first description of their physical compositions in plants. AC40 and AC19 subunits are typically common to Pol I (a.k.a. Pol A) and Pol III (a.k.a. Pol C) and are encoded by single genes whose mutation, in humans, is a cause of the craniofacial disorder, Treacher-Collins Syndrome. Surprisingly, A. thaliana, and related species, express two distinct AC40 paralogs, one of which assembles into Pol I and the other of which assembles into Polmore » III. Changes at eight amino acid positions correlate with this functional divergence of Pol I and Pol III-specific AC40 paralogs. Two genes encode homologs of the yeast C53 subunit, and either variant can assemble into Pol III. By contrast, only one of two potential C17 variants, and one of two potential C31 variants were detected in Pol III. We introduce a new nomenclature system for plant Pol I and Pol III subunits in which the twelve subunits that are structurally and functionally homologous among Pols I through V are assigned equivalent numbers.« less

Dexras1 a unique ras-GTPase interacts with NMDA receptor activity and provides a novel dissociation between anxiety, working memory and sensory gating.

PubMed

Carlson, G C; Lin, R E; Chen, Y; Brookshire, B R; White, R S; Lucki, I; Siegel, S J; Kim, S F

2016-05-13

Dexras1 is a novel GTPase that acts at a confluence of signaling mechanisms associated with psychiatric and neurological disease including NMDA receptors, NOS1AP and nNOS. Recent work has shown that Dexras1 mediates iron trafficking and NMDA-dependent neurodegeneration but a role for Dexras1 in normal brain function or psychiatric disease has not been studied. To test for such a role, mice with germline knockout (KO) of Dexras1 were assayed for behavioral abnormalities as well as changes in NMDA receptor subunit protein expression. Because Dexras1 is up-regulated during stress or by dexamethasone treatment, we included measures associated with emotion including anxiety and depression. Baseline anxiety-like measures (open field and zero maze) were not altered, nor were depression-like behavior (tail suspension). Measures of memory function yielded mixed results, with no changes in episodic memory (novel object recognition) but a significant decrement on working memory (T-maze). Alternatively, there was an increase in pre-pulse inhibition (PPI), without concomitant changes in either startle amplitude or locomotor activity. PPI data are consistent with the direction of change seen following exposure to dopamine D2 antagonists. An examination of NMDA subunit expression levels revealed an increased expression of the NR2A subunit, contrary to previous studies demonstrating down-regulation of the receptor following antipsychotic exposure (Schmitt et al., 2003) and up-regulation after exposure to isolation rearing (Turnock-Jones et al., 2009). These findings suggest a potential role for Dexras1 in modulating a selective subset of psychiatric symptoms, possibly via its interaction with NMDARs and/or other disease-related binding-partners. Furthermore, data suggest that modulating Dexras1 activity has contrasting effects on emotional, sensory and cognitive domains. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

Odor preference and olfactory memory are impaired in Olfaxin-deficient mice.

PubMed

Islam, Saiful; Ueda, Masashi; Nishida, Emika; Wang, Miao-Xing; Osawa, Masatake; Lee, Dongsoo; Itoh, Masanori; Nakagawa, Kiyomi; Tana; Nakagawa, Toshiyuki

2018-06-01

Olfaxin, which is a BNIP2 and Cdc42GAP homology (BCH) domain-containing protein, is predominantly expressed in mitral and tufted (M/T) cells in the olfactory bulb (OB). Olfaxin and Caytaxin, which share 56.3% amino acid identity, are similar in their glutamatergic terminal localization, kidney-type glutaminase (KGA) interaction, and caspase-3 substrate. Although the deletion of Caytaxin protein causes human Cayman ataxia and ataxia in the mutant mouse, the function of Olfaxin is largely unknown. In this study, we generated Prune2 gene mutant mice (Prune2 Ex16-/- ; knock out [KO] mice) using the CRISPR/Cas9 system, during which the exon 16 containing start codon of Olfaxin mRNA was deleted. Exon 16 has 80 nucleotides and is contained in four of five Prune2 isoforms, including PRUNE2, BMCC1, BNIPXL, and Olfaxin/BMCC1s. The levels of Olfaxin mRNA and Olfaxin protein in the OB and piriform cortex of KO mice significantly decreased. Although Prune2 mRNA also significantly decreased in the spinal cord, the gross anatomy of the spinal cord and dorsal root ganglion (DRG) was intact. Further, disturbance of the sensory and motor system was not observed in KO mice. Therefore, in the current study, we examined the role of Olfaxin in the olfactory system where PRUNE2, BMCC1, and BNIPXL are scarcely expressed. Odor preference was impaired in KO mice using opposite-sex urinary scents as well as a non-social odor stimulus (almond). Results of the odor-aversion test demonstrated that odor-associative learning was disrupted in KO mice. Moreover, the NMDAR2A/NMDAR2B subunits switch in the piriform cortex was not observed in KO mice. These results indicated that Olfaxin may play a critical role in odor preference and olfactory memory. Copyright © 2018 Elsevier B.V. All rights reserved.

IGF-1-Involved Negative Feedback of NR2B NMDA Subunits Protects Cultured Hippocampal Neurons Against NMDA-Induced Excitotoxicity.

PubMed

Li, Yun; Sun, Wei; Han, Song; Li, Jianing; Ding, Shu; Wang, Wei; Yin, Yanling

2017-01-01

Insulin-like growth factor 1 (IGF-1) is a multifunctional protein involved in neuronal polarity and axonal guidance. In our previous study, it was discovered that IGF-1 alleviated 50-μM NMDA-induced excitotoxicity against neuronal autophagy via depression of NR2B p-Ser1303 activation. However, it was found that NMDA at a higher dose did not cause neuronal autophagy. And, the performance of IGF-1 under severe excitotoxicity still needs to be clarified. In this study, we observed that IGF-1 can salvage the hippocampal neurons in an autophagy-independent manner after 150-μM NMDA exposure using thiazolyl blue tetrazolium bromide (MTT), lactate dehydrogenase (LDH), Western blot assay, and transmission electron microscopy. In addition, over-activation of post-synaptic NMDARs was found with the whole-cell patch clamp recording method. In order to explore whether there is a positive feedback way for post-synaptic NMDARs and the different pathway caused by 150 μM NMDA, the phosphorylation level of Fyn and the phosphorylation site of NR2B were investigated. It was observed that NR2B p-Tyr1472 was increased by the activation of Fyn after 150-μM NMDA exposure. When the neutralizing antibody against NR2B p-Ser1303 was added into the medium, both the activations of Fyn and NR2B p-Tyr1472 were blocked, suggesting NR2B p-Ser1303 may be the initial step of NMDA-induced excitotoxicity. In addition, since IGF-1 can block the initial step of NR2B activation, its effect is concluded to continue with the development of excitotoxicity. Overall, this study strongly indicates that the relationship between different phosphorylation sites of NR2B should be laid more emphasis on, which may be a vital target for the NR2B-involved excitotoxicity.

Alterations in ethanol-induced behaviors and consumption in knock-in mice expressing ethanol-resistant NMDA receptors.

PubMed

den Hartog, Carolina R; Beckley, Jacob T; Smothers, Thetford C; Lench, Daniel H; Holseberg, Zack L; Fedarovich, Hleb; Gilstrap, Meghin J; Homanics, Gregg E; Woodward, John J

2013-01-01

Ethanol's action on the brain likely reflects altered function of key ion channels such as glutamatergic N-methyl-D-aspartate receptors (NMDARs). In this study, we determined how expression of a mutant GluN1 subunit (F639A) that reduces ethanol inhibition of NMDARs affects ethanol-induced behaviors in mice. Mice homozygous for the F639A allele died prematurely while heterozygous knock-in mice grew and bred normally. Ethanol (44 mM; ∼0.2 g/dl) significantly inhibited NMDA-mediated EPSCs in wild-type mice but had little effect on responses in knock-in mice. Knock-in mice had normal expression of GluN1 and GluN2B protein across different brain regions and a small reduction in levels of GluN2A in medial prefrontal cortex. Ethanol (0.75-2.0 g/kg; i.p.) increased locomotor activity in wild-type mice but had no effect on knock-in mice while MK-801 enhanced activity to the same extent in both groups. Ethanol (2.0 g/kg) reduced rotarod performance equally in both groups but knock-in mice recovered faster following a higher dose (2.5 g/kg). In the elevated zero maze, knock-in mice had a blunted anxiolytic response to ethanol (1.25 g/kg) as compared to wild-type animals. No differences were noted between wild-type and knock-in mice for ethanol-induced loss of righting reflex, sleep time, hypothermia or ethanol metabolism. Knock-in mice consumed less ethanol than wild-type mice during daily limited-access sessions but drank more in an intermittent 24 h access paradigm with no change in taste reactivity or conditioned taste aversion. Overall, these data support the hypothesis that NMDA receptors are important in regulating a specific constellation of effects following exposure to ethanol.

Alterations in Ethanol-Induced Behaviors and Consumption in Knock-In Mice Expressing Ethanol-Resistant NMDA Receptors

PubMed Central

den Hartog, Carolina R.; Beckley, Jacob T.; Smothers, Thetford C.; Lench, Daniel H.; Holseberg, Zack L.; Fedarovich, Hleb; Gilstrap, Meghin J.; Homanics, Gregg E.; Woodward, John J.

2013-01-01

Ethanol's action on the brain likely reflects altered function of key ion channels such as glutamatergic N-methyl-D-aspartate receptors (NMDARs). In this study, we determined how expression of a mutant GluN1 subunit (F639A) that reduces ethanol inhibition of NMDARs affects ethanol-induced behaviors in mice. Mice homozygous for the F639A allele died prematurely while heterozygous knock-in mice grew and bred normally. Ethanol (44 mM; ∼0.2 g/dl) significantly inhibited NMDA-mediated EPSCs in wild-type mice but had little effect on responses in knock-in mice. Knock-in mice had normal expression of GluN1 and GluN2B protein across different brain regions and a small reduction in levels of GluN2A in medial prefrontal cortex. Ethanol (0.75–2.0 g/kg; IP) increased locomotor activity in wild-type mice but had no effect on knock-in mice while MK-801 enhanced activity to the same extent in both groups. Ethanol (2.0 g/kg) reduced rotarod performance equally in both groups but knock-in mice recovered faster following a higher dose (2.5 g/kg). In the elevated zero maze, knock-in mice had a blunted anxiolytic response to ethanol (1.25 g/kg) as compared to wild-type animals. No differences were noted between wild-type and knock-in mice for ethanol-induced loss of righting reflex, sleep time, hypothermia or ethanol metabolism. Knock-in mice consumed less ethanol than wild-type mice during daily limited-access sessions but drank more in an intermittent 24 h access paradigm with no change in taste reactivity or conditioned taste aversion. Overall, these data support the hypothesis that NMDA receptors are important in regulating a specific constellation of effects following exposure to ethanol. PMID:24244696

Effects of rhynchophylline on GluN1 and GluN2B expressions in primary cultured hippocampal neurons.

PubMed

He, Yan; Zeng, Sheng-Ya; Zhou, Shi-Wen; Qian, Gui-Sheng; Peng, Kang; Mo, Zhi-Xian; Zhou, Ji-Yin

2014-10-01

N-methyl-d-aspartate (NMDA) receptor subunits GluN1 and GluN2B in hippocampal neurons play key roles in anxiety. Our previous studies show that rhynchophylline, an active component of the Uncaria species, down-regulates GluN2B expression in the hippocampal CA1 area of amphetamine-induced rat. The effects of rhynchophylline on expressions of GluN1 and GluN2B in primary hippocampal neurons in neonatal rats in vitro were investigated. Neonatal hippocampal neurons were cultured with neurobasal-A medium. After incubation for 6h or 48 h with rhynchophylline (non-competitive NMDAR antagonist) and MK-801 (non-competitive NMDAR antagonist with anxiolytic effect, as the control drug) from day 6, neuron toxicity, mRNA and protein expressions of GluN1 and GluN2B were analyzed. GluN1 is mainly distributed on neuronal axons and dendritic trunks, cytoplasm and cell membrane near axons and dendrites. GluN2B is mainly distributed on the membrane, dendrites, and axon membranes. GluN1 and GluN2B are codistributed on dendritic trunks and dendritic spines. After 48 h incubation, a lower concentration of rhynchophylline (lower than 400 μmol/L) and MK-801 (lower than 200 μmol/L) have no toxicity on neonatal hippocampal neurons. Rhynchophylline up-regulated GluN1 mRNA expression at 6h and mRNA and protein expressions at 48h, but down-regulated GluN2B mRNA and protein expressions at 48 h. However, GluN1 and GluN2B mRNA expressions were down-regulated at 6h, and mRNA and protein expressions were both up-regulated by MK-801 at 48h. These findings show that rhynchophylline reciprocally regulates GluN1 and GluN2B expressions in hippocampal neurons, indicating a potential anxiolytic property for rhynchophylline. Copyright © 2014 Elsevier B.V. All rights reserved.

Dual function of Rpn5 in two PCI complexes, the 26S proteasome and COP9 signalosome.

PubMed

Yu, Zanlin; Kleifeld, Oded; Lande-Atir, Avigail; Bsoul, Maisa; Kleiman, Maya; Krutauz, Daria; Book, Adam; Vierstra, Richard D; Hofmann, Kay; Reis, Noa; Glickman, Michael H; Pick, Elah

2011-04-01

Subunit composition and architectural structure of the 26S proteasome lid is strictly conserved between all eukaryotes. This eight-subunit complex bears high similarity to the eukaryotic translation initiation factor 3 and to the COP9 signalosome (CSN), which together define the proteasome CSN/COP9/initiation factor (PCI) troika. In some unicellular eukaryotes, the latter two complexes lack key subunits, encouraging questions about the conservation of their structural design. Here we demonstrate that, in Saccharomyces cerevisiae, Rpn5 plays dual roles by stabilizing proteasome and CSN structures independently. Proteasome and CSN complexes are easily dissected, with Rpn5 the only subunit in common. Together with Rpn5, we identified a total of six bona fide subunits at roughly stoichiometric ratios in isolated, affinity-purified CSN. Moreover, the copy of Rpn5 associated with the CSN is required for enzymatic hydrolysis of Rub1/Nedd8 conjugated to cullins. We propose that multitasking by a single subunit, Rpn5 in this case, allows it to function in different complexes simultaneously. These observations demonstrate that functional substitution of subunits by paralogues is feasible, implying that the canonical composition of the three PCI complexes in S. cerevisiae is more robust than hitherto appreciated.

Selective alterations of NMDAR function and plasticity in D1 and D2 medium spiny neurons in the nucleus accumbens shell following chronic intermittent ethanol exposure.

PubMed

Renteria, Rafael; Maier, Esther Y; Buske, Tavanna R; Morrisett, Richard A

2017-01-01

A major mouse model widely adopted in recent years to induce pronounced ethanol intake is the ethanol vapor model known as "CIE" or "Chronic Intermittent Ethanol." One critical question concerning this model is whether the rapid induction of high blood ethanol levels for such short time periods is sufficient to induce alterations in N-methyl-d-aspartate receptor (NMDAR) function which may contribute to excessive ethanol intake. In this study, we determined whether such short term intermittent ethanol exposure modulates NMDAR function as well as other prominent electrophysiological properties and the expression of plasticity in both D1 (D1+) and D2 (D1-) dopamine receptor expressing medium spiny neurons (MSNs) in the nucleus accumbens (NAc) shell. To distinguish between the two subtypes of MSNs in the NAc we treated Drd1a-TdTomato transgenic mice with CIE vapor and electrophysiological recordings were conducted 24 h after the last vapor exposure. To investigate CIE induced alterations in plasticity, long-term depression (LTD) was induced by pairing low frequency stimulation (LFS) with post synaptic depolarization. In ethanol naïve mice, LFS induced synaptic depression (LTD) was apparent exclusively in D1+ MSNs. Whereas in slices prepared from CIE treated mice, LFS induced synaptic potentiation (LTP) in D1+ MSNs. Furthermore, following CIE exposure, LFS now produced LTD in D1- MSNs. We found that CIE exposure induced an increase in excitability in D1+ MSNs with no change in D1- MSNs. After CIE, we found a significant increase in spontaneous EPSCs (sEPSCs) frequency in D1+ but not D1- MSNs suggesting alterations in baseline α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) mediated signaling. CIE induced changes in NMDAR function were measured using the NMDA/AMPA ratio and input-output curves of isolated NMDAR currents. We observed a significant increase in NMDAR function in D1+ MSNs and a decrease in D1- MSNs after ethanol vapor exposure. The reversal of NMDAR function may account for the CIE induced alterations in the expression of plasticity. The cell type specific alterations in excitatory signaling in the NAc shell may constitute an important neuroadaptation necessary for the expression of increased ethanol consumption induced by intermittent ethanol vapor exposure. This article is part of the Special Issue entitled 'Ionotropic glutamate receptors'. Copyright © 2016 Elsevier Ltd. All rights reserved.

Functional characterization of α7 nicotinic acetylcholine and NMDA receptor signaling in SH-SY5Y neuroblastoma cells in an ERK phosphorylation assay.

PubMed

Elnagar, Mohamed R; Walls, Anne Byriel; Helal, Gouda K; Hamada, Farid M; Thomsen, Morten Skøtt; Jensen, Anders A

2018-05-05

In the present study, the functional properties of α7 nicotinic acetylcholine receptors (α7 nAChRs) and N-methyl-D-aspartate receptors (NMDARs) endogenously expressed in SH-SY5Y human neuroblastoma cells were characterized in an extracellular-signal regulated kinase (ERK) phosphorylation assay. Both choline and N-methyl-D-aspartate (NMDA) mediated robust concentration-dependent increases in ERK phosphorylation in the SH-SY5Y cells, exhibiting EC 50 values in good agreement with those reported for the agonists at recombinant α7 nAChRs and NMDARs, respectively. Importantly, the responses evoked by choline (10 mM) and by NMDA (50 μM) were significantly inhibited by the α7-selective antagonist α-bungarotoxin (100 nM) and by the NMDAR-selective antagonist MK-801 (50 μM), respectively. The increased ERK phosphorylation levels observed upon co-application of choline (1, 3, 10 mM) and NMDA (50 μM) compared to those produced by the two agonists on their own were fully reconcilable with additive effects and did not reveal substantial synergy between α7 nAChR and NMDAR signaling. Interestingly, however, the responses evoked by the "choline (10 mM) - NMDA (50 μM)" combination were almost completely inhibited by α-bungarotoxin (100 nM) as well as by MK-801 (50 μM), suggesting some sort of a link between α7 nAChR- and NMDAR-mediated ERK phosphorylation. Finally, oligomeric amyloid-β 1-42 peptide (1000 nM) mediated robust inhibition of the ERK phosphorylation induced by choline (10 mM), NMDA (50 μM) and the "choline (10 mM) - NMDA (50 μM)" combination. In conclusion, ERK phosphorylation measurements in SH-SY5Y cells provides a robust assay for studies of α7 nAChR- and NMDAR-mediating signaling and putative functional interactions between the receptors. Copyright © 2018 Elsevier B.V. All rights reserved.

Compromised NMDA/Glutamate Receptor Expression in Dopaminergic Neurons Impairs Instrumental Learning, But Not Pavlovian Goal Tracking or Sign Tracking1,2,3

PubMed Central

James, Alex S.; Pennington, Zachary T.; Tran, Phu

2015-01-01

Abstract Two theories regarding the role for dopamine neurons in learning include the concepts that their activity serves as a (1) mechanism that confers incentive salience onto rewards and associated cues and/or (2) contingency teaching signal reflecting reward prediction error. While both theories are provocative, the causal role for dopamine cell activity in either mechanism remains controversial. In this study mice that either fully or partially lacked NMDARs in dopamine neurons exclusively, as well as appropriate controls, were evaluated for reward-related learning; this experimental design allowed for a test of the premise that NMDA/glutamate receptor (NMDAR)-mediated mechanisms in dopamine neurons, including NMDA-dependent regulation of phasic discharge activity of these cells, modulate either the instrumental learning processes or the likelihood of pavlovian cues to become highly motivating incentive stimuli that directly attract behavior. Loss of NMDARs in dopamine neurons did not significantly affect baseline dopamine utilization in the striatum, novelty evoked locomotor behavior, or consumption of a freely available, palatable food solution. On the other hand, animals lacking NMDARs in dopamine cells exhibited a selective reduction in reinforced lever responses that emerged over the course of instrumental learning. Loss of receptor expression did not, however, influence the likelihood of an animal acquiring a pavlovian conditional response associated with attribution of incentive salience to reward-paired cues (sign tracking). These data support the view that reductions in NMDAR signaling in dopamine neurons affect instrumental reward-related learning but do not lend support to hypotheses that suggest that the behavioral significance of this signaling includes incentive salience attribution. PMID:26464985

Role of N-Methyl-D-Aspartate Receptors in Action-Based Predictive Coding Deficits in Schizophrenia.

PubMed

Kort, Naomi S; Ford, Judith M; Roach, Brian J; Gunduz-Bruce, Handan; Krystal, John H; Jaeger, Judith; Reinhart, Robert M G; Mathalon, Daniel H

2017-03-15

Recent theoretical models of schizophrenia posit that dysfunction of the neural mechanisms subserving predictive coding contributes to symptoms and cognitive deficits, and this dysfunction is further posited to result from N-methyl-D-aspartate glutamate receptor (NMDAR) hypofunction. Previously, by examining auditory cortical responses to self-generated speech sounds, we demonstrated that predictive coding during vocalization is disrupted in schizophrenia. To test the hypothesized contribution of NMDAR hypofunction to this disruption, we examined the effects of the NMDAR antagonist, ketamine, on predictive coding during vocalization in healthy volunteers and compared them with the effects of schizophrenia. In two separate studies, the N1 component of the event-related potential elicited by speech sounds during vocalization (talk) and passive playback (listen) were compared to assess the degree of N1 suppression during vocalization, a putative measure of auditory predictive coding. In the crossover study, 31 healthy volunteers completed two randomly ordered test days, a saline day and a ketamine day. Event-related potentials during the talk/listen task were obtained before infusion and during infusion on both days, and N1 amplitudes were compared across days. In the case-control study, N1 amplitudes from 34 schizophrenia patients and 33 healthy control volunteers were compared. N1 suppression to self-produced vocalizations was significantly and similarly diminished by ketamine (Cohen's d = 1.14) and schizophrenia (Cohen's d = .85). Disruption of NMDARs causes dysfunction in predictive coding during vocalization in a manner similar to the dysfunction observed in schizophrenia patients, consistent with the theorized contribution of NMDAR hypofunction to predictive coding deficits in schizophrenia. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

D-Amino Acid Aberrations in Cerebrospinal Fluid and Plasma of Smokers

PubMed Central

Luykx, Jurjen J; Bakker, Steven C; van Boxmeer, Loes; Vinkers, Christiaan H; Smeenk, Hanne E; Visser, Wouter F; Verhoeven-Duif, Nanda M; Strengman, Eric; Buizer-Voskamp, Jacobine E; de Groene, Lizzy; van Dongen, Eric PA; Borgdorff, Paul; Bruins, Peter; de Koning, Tom J; Kahn, René S; Ophoff, Roel A

2013-01-01

The glutamatergic neurotransmission system and the N-methyl-D-aspartate receptor (NMDAR) have been implicated in smoking and alcohol consumption behavior. Preclinical studies have demonstrated that nicotine and ethanol influence NMDAR functionality, which may have a role in tendencies to consume these substances. Nonetheless, little is known about concentrations of NMDAR coagonists in the cerebrospinal fluid (CSF) and plasma of individuals who smoke or consume alcohol. Glycine and L- and D-stereoisomers of alanine, serine, and proline were therefore measured using ultra-high-performance liquid chromatography-tandem mass spectrometry in 403 healthy subjects. Nicotine and alcohol consumption were quantified using questionnaires. Possible differences in NMDAR coagonist concentrations in plasma and CSF were investigated using ANCOVA with age, body mass index, and storage duration as covariates. The significance threshold was Bonferroni corrected (α=0.00625). Compared with non-smokers, smokers displayed lower levels of D-proline in plasma (p=0.0027, Cohen's d=−0.41) and D-proline in CSF (p=0.0026, Cohen's d=−0.43). D-Serine in CSF was higher in smokers than in non-smokers (p=0.0052, Cohen's d=0.41). After subdividing participants based on smoking quantity, dose-dependent decreases were demonstrated in smokers for D-proline in plasma (F=5.65, p=0.0039) and D-proline in CSF (F=5.20, p=0.0060). No differences in NMDAR coagonist levels between alcohol consumption groups were detected. To our knowledge, this is the first report to implicate D-amino acids in smoking behavior of humans. Whether such concentration differences lie at the root of or result from smoking habits may be addressed in prospective studies. PMID:23615666

Single-Neuron NMDA Receptor Phenotype Influences Neuronal Rewiring and Reintegration following Traumatic Injury

PubMed Central

Patel, Tapan P.; Ventre, Scott C.; Geddes-Klein, Donna; Singh, Pallab K.

2014-01-01

Alterations in the activity of neural circuits are a common consequence of traumatic brain injury (TBI), but the relationship between single-neuron properties and the aggregate network behavior is not well understood. We recently reported that the GluN2B-containing NMDA receptors (NMDARs) are key in mediating mechanical forces during TBI, and that TBI produces a complex change in the functional connectivity of neuronal networks. Here, we evaluated whether cell-to-cell heterogeneity in the connectivity and aggregate contribution of GluN2B receptors to [Ca2+]i before injury influenced the functional rewiring, spontaneous activity, and network plasticity following injury using primary rat cortical dissociated neurons. We found that the functional connectivity of a neuron to its neighbors, combined with the relative influx of calcium through distinct NMDAR subtypes, together contributed to the individual neuronal response to trauma. Specifically, individual neurons whose [Ca2+]i oscillations were largely due to GluN2B NMDAR activation lost many of their functional targets 1 h following injury. In comparison, neurons with large GluN2A contribution or neurons with high functional connectivity both independently protected against injury-induced loss in connectivity. Mechanistically, we found that traumatic injury resulted in increased uncorrelated network activity, an effect linked to reduction of the voltage-sensitive Mg2+ block of GluN2B-containing NMDARs. This uncorrelated activation of GluN2B subtypes after injury significantly limited the potential for network remodeling in response to a plasticity stimulus. Together, our data suggest that two single-cell characteristics, the aggregate contribution of NMDAR subtypes and the number of functional connections, influence network structure following traumatic injury. PMID:24647941

Rhynchophylline suppresses soluble Aβ1-42-induced impairment of spatial cognition function via inhibiting excessive activation of extrasynaptic NR2B-containing NMDA receptors.

PubMed

Yang, Yang; Ji, Wei-Gang; Zhu, Zhi-Ru; Wu, Yu-Ling; Zhang, Zhi-Yang; Qu, Shao-Chen

2018-06-01

Rhynchophylline (RIN) is a significant active component isolated from the Chinese herbal medicine Uncaria rhynchophylla. The overproduction of soluble amyloid β protein (Aβ) oligomers in the hippocampus is closely involved in impairments in cognitive function at the early stage of Alzheimer's disease (AD). Growing evidences show that RIN possesses neuroprotective effects against Aβ-induced neurotoxicity. However, whether RIN can prevent soluble Aβ 1-42 -induced impairments in spatial cognitive function and synaptic plasticity is still unclear. Using the combined methods of behavioral tests, immunofluorescence and electrophysiological recordings, we characterized the key neuroprotective properties of RIN and its possible cellular and molecular mechanisms against soluble Aβ 1-42 -related impairments in rats. Our findings are as follows: (1) RIN efficiently rescued the soluble Aβ 1-42 -induced spatial learning and memory deficits in the Morris water maze test and prevented soluble Aβ 1-42 -induced suppression in long term potentiation (LTP) in the entorhinal cortex (EC)-dentate gyrus (DG) circuit. (2) Excessive activation of extrasynaptic GluN2B-NMDAR and subsequent Ca 2+ overload contributed to the soluble Aβ 1-42 -induced impairments in spatial cognitive function and synaptic plasticity. (3) RIN prevented Aβ 1-42 -induced excessive activation of extrasynaptic NMDARs by reducing extrasynaptic NMDARs -mediated excitatory postsynaptic currents and down regulating GluN2B-NMDAR expression in the DG region, which inhibited Aβ 1-42 -induced Ca 2+ overload mediated by extrasynanptic NMDARs. The results suggest that RIN could be an effective therapeutic candidate for cognitive impairment in AD. Copyright © 2018 Elsevier Ltd. All rights reserved.

Iterative Focused Screening with Biological Fingerprints Identifies Selective Asc-1 Inhibitors Distinct from Traditional High Throughput Screening.

PubMed

Kutchukian, Peter S; Warren, Lee; Magliaro, Brian C; Amoss, Adam; Cassaday, Jason A; O'Donnell, Gregory; Squadroni, Brian; Zuck, Paul; Pascarella, Danette; Culberson, J Chris; Cooke, Andrew J; Hurzy, Danielle; Schlegel, Kelly-Ann Sondra; Thomson, Fiona; Johnson, Eric N; Uebele, Victor N; Hermes, Jeffrey D; Parmentier-Batteur, Sophie; Finley, Michael

2017-02-17

N-methyl-d-aspartate receptors (NMDARs) mediate glutamatergic signaling that is critical to cognitive processes in the central nervous system, and NMDAR hypofunction is thought to contribute to cognitive impairment observed in both schizophrenia and Alzheimer's disease. One approach to enhance the function of NMDAR is to increase the concentration of an NMDAR coagonist, such as glycine or d-serine, in the synaptic cleft. Inhibition of alanine-serine-cysteine transporter-1 (Asc-1), the primary transporter of d-serine, is attractive because the transporter is localized to neurons in brain regions critical to cognitive function, including the hippocampus and cortical layers III and IV, and is colocalized with d-serine and NMDARs. To identify novel Asc-1 inhibitors, two different screening approaches were performed with whole-cell amino acid uptake in heterologous cells stably expressing human Asc-1: (1) a high-throughput screen (HTS) of 3 M compounds measuring 35 S l-cysteine uptake into cells attached to scintillation proximity assay beads in a 1536 well format and (2) an iterative focused screen (IFS) of a 45 000 compound diversity set using a 3 H d-serine uptake assay with a liquid scintillation plate reader in a 384 well format. Critically important for both screening approaches was the implementation of counter screens to remove nonspecific inhibitors of radioactive amino acid uptake. Furthermore, a 15 000 compound expansion step incorporating both on- and off-target data into chemical and biological fingerprint-based models for selection of additional hits enabled the identification of novel Asc-1-selective chemical matter from the IFS that was not identified in the full-collection HTS.

GLYX-13, a NMDA Receptor Glycine-Site Functional Partial Agonist, Induces Antidepressant-Like Effects Without Ketamine-Like Side Effects

PubMed Central

Burgdorf, Jeffrey; Zhang, Xiao-lei; Nicholson, Katherine L; Balster, Robert L; David Leander, J; Stanton, Patric K; Gross, Amanda L; Kroes, Roger A; Moskal, Joseph R

2013-01-01

Recent human clinical studies with the NMDA receptor (NMDAR) antagonist ketamine have revealed profound and long-lasting antidepressant effects with rapid onset in several clinical trials, but antidepressant effects were preceded by dissociative side effects. Here we show that GLYX-13, a novel NMDAR glycine-site functional partial agonist, produces an antidepressant-like effect in the Porsolt, novelty induced hypophagia, and learned helplessness tests in rats without exhibiting substance abuse-related, gating, and sedative side effects of ketamine in the drug discrimination, conditioned place preference, pre-pulse inhibition and open-field tests. Like ketamine, the GLYX-13-induced antidepressant-like effects required AMPA/kainate receptor activation, as evidenced by the ability of NBQX to abolish the antidepressant-like effect. Both GLYX-13 and ketamine persistently (24 h) enhanced the induction of long-term potentiation of synaptic transmission and the magnitude of NMDAR-NR2B conductance at rat Schaffer collateral-CA1 synapses in vitro. Cell surface biotinylation studies showed that both GLYX-13 and ketamine led to increases in both NR2B and GluR1 protein levels, as measured by Western analysis, whereas no changes were seen in mRNA expression (microarray and qRT-PCR). GLYX-13, unlike ketamine, produced its antidepressant-like effect when injected directly into the medial prefrontal cortex (MPFC). These results suggest that GLYX-13 produces an antidepressant-like effect without the side effects seen with ketamine at least in part by directly modulating NR2B-containing NMDARs in the MPFC. Furthermore, the enhancement of ‘metaplasticity' by both GLYX-13 and ketamine may help explain the long-lasting antidepressant effects of these NMDAR modulators. GLYX-13 is currently in a Phase II clinical development program for treatment-resistant depression. PMID:23303054

Convergent mechanisms underlying rapid antidepressant action

PubMed Central

Zanos, Panos; Thompson, Scott M.; Duman, Ronald S.; Zarate, Carlos A.; Gould, Todd D.

2018-01-01

Traditional pharmacological treatments for depression have a delayed therapeutic onset, ranging from several weeks to months, and there is a high percentage of individuals who never respond to treatment. In contrast, ketamine produces rapid-onset antidepressant, anti-suicidal and anti-anhedonic actions following a single administration to depressed patients. Proposed mechanisms of ketamine’s antidepressant action include N-methyl-D-aspartate receptor (NMDAR) modulation, GABAergic interneuron disinhibition, and direct actions of its hydroxynorketamine (HNK) metabolites. Downstream actions include activation of mechanistic target of rapamycin (mTOR), deactivation of glycogen synthase kinase-3 and eukaryotic elongation factor 2 (eEF2), enhanced brain-derived neurotrophic factor (BDNF) signaling, and activation of α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptors (AMPARs). These putative mechanisms of ketamine action are not mutually exclusive and may complement each other to induce potentiation of excitatory synapses in affective-regulating brain circuits, which results in amelioration of depression symptoms. We review these proposed mechanisms of ketamine action in the context of how such mechanisms are informing the development of novel putative rapid-acting antidepressant drugs. Such drugs that have undergoing pre-clinical, and in some cases clinical, testing include the muscarinic acetylcholine receptor antagonist scopolamine, GluN2B-NMDAR antagonists (i.e., CP-101,606, MK-0657), (2R,6R)-HNK, NMDAR glycine site modulators (i.e., 4-chlorokynurenine - pro-drug of the glycineB NMDAR antagonist 7-chlorokynurenic acid), NMDAR agonists (i.e. GLYX-13 (rapastinel)), metabotropic glutamate receptor 2/3 (mGluR2/3) antagonists, GABAA receptor modulators, and drugs acting on various serotonin receptor subtypes. These ongoing studies suggest that the future acute treatment of depression will typically occur within hours, rather than months, of treatment initiation. PMID:29516301

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ribeiro, Mariana P.C.; Laboratory of Biochemistry, Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra; Nunes-Correia, Isabel

Recent reports suggest that N-methyl-D-aspartate receptor (NMDAR) blockade by MK-801 decreases tumor growth. Thus, we investigated whether other ionotropic glutamate receptor (iGluR) antagonists were also able to modulate the proliferation of melanoma cells. On the other hand, the antiestrogen tamoxifen (TAM) decreases the proliferation of melanoma cells, and is included in combined therapies for melanoma. As the efficacy of TAM is limited by its metabolism, we investigated the effects of the NMDAR antagonist MK-801 in combination with TAM and its active metabolites, 4-hydroxytamoxifen (OHTAM) and endoxifen (EDX). The NMDAR blockers MK-801 and memantine decreased mouse melanoma K1735-M2 cell proliferation. Inmore » contrast, the NMDAR competitive antagonist APV and the AMPA and kainate receptor antagonist NBQX did not affect cell proliferation, suggesting that among the iGluR antagonists only the NMDAR channel blockers inhibit melanoma cell proliferation. The combination of antiestrogens with MK-801 potentiated their individual effects on cell biomass due to diminished cell proliferation, since it decreased the cell number and DNA synthesis without increasing cell death. Importantly, TAM metabolites combined with MK-801 promoted cell cycle arrest in G1. Therefore, the data obtained suggest that the activity of MK-801 and antiestrogens in K1735-M2 cells is greatly enhanced when used in combination. - Highlights: • MK-801 and memantine decrease melanoma cell proliferation. • The combination of MK-801 with antiestrogens inhibits melanoma cell proliferation. • These combinations greatly enhance the effects of the compounds individually. • MK-801 combined with tamoxifen active metabolites induces cell cycle arrest in G1. • The combination of MK-801 and antiestrogens is an innovative strategy for melanoma.« less

A Novel Hydrogen Sulfide-releasing N-Methyl-d-Aspartate Receptor Antagonist Prevents Ischemic Neuronal Death*

PubMed Central

Marutani, Eizo; Kosugi, Shizuko; Tokuda, Kentaro; Khatri, Ashok; Nguyen, Rebecca; Atochin, Dmitriy N.; Kida, Kotaro; Van Leyen, Klaus; Arai, Ken; Ichinose, Fumito

2012-01-01

Physiological levels of H2S exert neuroprotective effects, whereas high concentrations of H2S may cause neurotoxicity in part via activation of NMDAR. To characterize the neuroprotective effects of combination of exogenous H2S and NMDAR antagonism, we synthesized a novel H2S-releasing NMDAR antagonist N-((1r,3R,5S,7r)-3,5-dimethyladamantan-1-yl)-4-(3-thioxo-3H-1,2-dithiol-4-yl)-benzamide (S-memantine) and examined its effects in vitro and in vivo. S-memantine was synthesized by chemically combining a slow releasing H2S donor 4-(3-thioxo-3H-1,2-dithiol-4-yl)-benzoic acid (ACS48) with a NMDAR antagonist memantine. S-memantine increased intracellular sulfide levels in human neuroblastoma cells (SH-SY5Y) 10-fold as high as that was achieved by ACS48. Incubation with S-memantine after reoxygenation following oxygen and glucose deprivation (OGD) protected SH-SY5Y cells and murine primary cortical neurons more markedly than did ACS48 or memantine. Glutamate-induced intracellular calcium accumulation in primary cortical neurons were aggravated by sodium sulfide (Na2S) or ACS48, but suppressed by memantine and S-memantine. S-memantine prevented glutamate-induced glutathione depletion in SH-SY5Y cells more markedly than did Na2S or ACS48. Administration of S-memantine after global cerebral ischemia and reperfusion more robustly decreased cerebral infarct volume and improved survival and neurological function of mice than did ACS48 or memantine. These results suggest that an H2S-releasing NMDAR antagonist derivative S-memantine prevents ischemic neuronal death, providing a novel therapeutic strategy for ischemic brain injury. PMID:22815476

Glutamate Signaling and Mitochondrial Dysfunction in Models of Parkinson’s Disease

DTIC Science & Technology

2014-03-01

stages of PD, an elevation in synaptically released glutamate leads to persistent activation of NMDARs that synergizes with Cav1 calcium channels to...neurons is attributable to activity -dependent calcium entry through Cav1 channels, resulting in mitochondrial oxidant stress. Although this mechanism...glutamate leads to persistent activation of NMDARs that synergizes with Cav1 calcium channels to significantly increase mitochondrial oxidant stress and

[Identification of NMDA receptor in normal bovine ovary and ovum].

PubMed

Tachibana, Naoko; Ikeda, Shu-ichi

2014-01-01

To clarify the pathogenesis of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis in patients without ovarian teratoma, we investigate normal human ovary, normal bovine ovary and bovine ova. On the basis of immunohistochemical studies, normal human ovary expressed NR2B epitope in primordial oocytes. The results of SDS-PAGE and immunoblotting using bovine ovarian tissues and ova, we identified two bands of NR1 and NR2B. Moreover, reverse phase liquid chromatography coupled to tandem mass spectrometry showed peptides fractions of NR1, NR2A, NR2B and NR2C. Immunocytochemical study disclosed that normal bovine oocyte has a strong affinity for a patient's disease-specific IgG. Anti-NMDAR encephalitis involves mainly young women who are in their reproductive age. Ovarian teratoma is important as simultaneous tumor, the percentage of patients with ovarian teratoma is less than 40%. It is obvious that the origin of ovarian teratoma is oocyte. So the existence of NMDAR in normal oocytes is very important to assert that ovary itself is the antigen presenting tissue. And also it is helpful to explain why young women are mainly affected from this disease. It seems to conclude that anti-NMDAR encephalitis is one form of autoimmune synaptic encephalitis and that the antigen presenting tissue is ovary itself.

Ameliorating treatment-refractory depression with intranasal ketamine: potential NMDA receptor actions in the pain circuitry representing mental anguish.

PubMed

Opler, Lewis A; Opler, Mark G A; Arnsten, Amy F T

2016-02-01

This article reviews the antidepressant actions of ketamine, an N-methyl-D-aspartame glutamate receptor (NMDAR) antagonist, and offers a potential neural mechanism for intranasal ketamine's ultra-rapid actions based on the key role of NMDAR in the nonhuman primate prefrontal cortex (PFC). Although intravenous ketamine infusions can lift mood within hours, the current review describes how intranasal ketamine administration can have ultra-rapid antidepressant effects, beginning within minutes (5-40 minutes) and lasting hours, but with repeated treatments needed for sustained antidepressant actions. Research in rodents suggests that increased synaptogenesis in PFC may contribute to the prolonged benefit of ketamine administration, beginning hours after administration. However, these data cannot explain the relief that occurs within minutes of intranasal ketamine delivery. We hypothesize that the ultra-rapid effects of intranasal administration in humans may be due to ketamine blocking the NMDAR circuits that generate the emotional representations of pain (eg, Brodmann Areas 24 and 25, insular cortex), cortical areas that can be overactive in depression and which sit above the nasal epithelium. In contrast, NMDAR blockade in the dorsolateral PFC following systemic administration of ketamine may contribute to cognitive deficits. This novel view may help to explain how intravenous ketamine can treat the symptoms of depression yet worsen the symptoms of schizophrenia.

G protein‐coupled receptor 37‐like 1 modulates astrocyte glutamate transporters and neuronal NMDA receptors and is neuroprotective in ischemia

PubMed Central

Jolly, Sarah; Bazargani, Narges; Quiroga, Alejandra C.; Pringle, Nigel P.

2017-01-01

Abstract We show that the G protein‐coupled receptor GPR37‐like 1 (GPR37L1) is expressed in most astrocytes and some oligodendrocyte precursors in the mouse central nervous system. This contrasts with GPR37, which is mainly in mature oligodendrocytes. Comparison of wild type and Gpr37l1–/– mice showed that loss of GPR37L1 did not affect the input resistance or resting potential of astrocytes or neurons in the hippocampus. However, GPR37L1‐mediated signalling inhibited astrocyte glutamate transporters and – surprisingly, given its lack of expression in neurons – reduced neuronal NMDA receptor (NMDAR) activity during prolonged activation of the receptors as occurs in ischemia. This effect on NMDAR signalling was not mediated by a change in the release of D‐serine or TNF‐α, two astrocyte‐derived agents known to modulate NMDAR function. After middle cerebral artery occlusion, Gpr37l1 expression was increased around the lesion. Neuronal death was increased by ∼40% in Gpr37l1–/– brain compared to wild type in an in vitro model of ischemia. Thus, GPR37L1 protects neurons during ischemia, presumably by modulating extracellular glutamate concentration and NMDAR activation. PMID:28795439

Diagnóstico diferencial en la encefalitis por anticuerpos contra el receptor NMDA

PubMed Central

González-Valcárcel, J.; Rosenfeld, M.R.; Dalmau, J.

2011-01-01

Resumen Introducción La encefalitis por anticuerpos contra el receptor de NMDA (NMDAR) suele desarrollarse como un síndrome característico de evolución multifásica y diagnóstico diferencial amplio. Pacientes Presentamos a 2 pacientes diagnosticadas de encefalitis por anticuerpos NMDAR con un cuadro clínico típico, pero que inicialmente señaló otras etiologías. Discusión La afectación frecuente de pacientes jóvenes con manifestaciones psiquiátricas prominentes indica frecuentemente otras consideraciones diagnósticas; las más frecuentes son las encefalitis virales, los procesos psiquiátricos y el síndrome neuroléptico maligno. Varios síndromes previamente definidos de manera parcial o descriptiva en adultos y pacientes pediátricos probablemente eran casos de encefalitis anti-NMDAR. Conclusiones La encefalitis anti-NMDAR debe considerarse en pacientes jóvenes con manifestaciones psiquiátricas subagudas, movimientos anormales y alteraciones autonómicas. La caracterización clínica e inmunológica de esta enfermedad ha llevado a la identificación de nuevos anticuerpos que afectan a procesos de memoria, aprendizaje, conducta y psicosis. PMID:20964986

Aquaporin-4 deficiency facilitates fear memory extinction in the hippocampus through excessive activation of extrasynaptic GluN2B-containing NMDA receptors.

PubMed

Wu, Xin; Zhang, Jie-Ting; Li, Di; Zhou, Jun; Yang, Jun; Zheng, Hui-Ling; Chen, Jian-Guo; Wang, Fang

2017-01-01

Aquaporin-4 (AQP-4) is the predominant water channel in the brain and primarily expressed in astrocytes. Astrocytes have been generally believed to play important roles in regulating synaptic plasticity and information processing. A growing number of evidence shows that AQP-4 plays a potential role in the regulation of astrocyte function. However, little is known about the function of AQP-4 for synaptic plasticity in the hippocampus. Therefore, we evaluated long-term depression (LTD) in the hippocampus and the extinction of fear memory of AQP-4 knockout (KO) and wild-type (WT) mice. We found that AQP-4 deficiency facilitated fear memory extinction and NMDA receptors (NMDARs)-dependent LTD in the CA3-CA1 pathway. Furthermore, AQP-4 deficiency selectively increased GluN2B-NMDAR-mediated excitatory postsynaptic currents (EPSCs). The excessive activation of extrasynaptic GluN2B-NMDAR contributed to the facilitation of NMDAR-dependent LTD and enhancement of fear memory extinction in AQP-4 KO mice. Thus, it appears that AQP-4 may be a potential target for intervention in fear memory extinction. This article is part of the Special Issue entitled 'Ionotropic glutamate receptors'. Copyright © 2016 Elsevier Ltd. All rights reserved.

The NMDAr antagonist ketamine interferes with manipulation of information for transitive inference reasoning in non-human primates.

PubMed

Brunamonti, Emiliano; Mione, Valentina; Di Bello, Fabio; De Luna, Paolo; Genovesio, Aldo; Ferraina, Stefano

2014-09-01

One of the most remarkable traits of highly encephalized animals is their ability to manipulate knowledge flexibly to infer logical relationships. Operationally, the corresponding cognitive process can be defined as reasoning. One hypothesis is that this process relies on the reverberating activity of glutamate neural circuits, sustained by NMDA receptor (NMDAr) mediated synaptic transmission, in both parietal and prefrontal areas. We trained two macaque monkeys to perform a form of deductive reasoning - the transitive inference task - in which they were required to learn the relationship between six adjacent items in a single session and then deduct the relationship between nonadjacent items that had not been paired in the learning phase. When the animals had learned the sequence, we administered systemically a subanaesthetic dose of ketamine (a NMDAr antagonist) and measured their performance on learned and novel problems. We observed impairments in determining the relationship between novel pairs of items. Our results are consistent with the hypothesis that transitive inference premises are integrated during learning in a unified representation and that reducing NMDAr activity interferes with the use of this mental model, when decisions are required in comparing pairs of items that have not been learned. © The Author(s) 2014.

Agmatine reverses pain induced by inflammation, neuropathy, and spinal cord injury.

PubMed

Fairbanks, C A; Schreiber, K L; Brewer, K L; Yu, C G; Stone, L S; Kitto, K F; Nguyen, H O; Grocholski, B M; Shoeman, D W; Kehl, L J; Regunathan, S; Reis, D J; Yezierski, R P; Wilcox, G L

2000-09-12

Antagonists of glutamate receptors of the N-methyl-d-aspartate subclass (NMDAR) or inhibitors of nitric oxide synthase (NOS) prevent nervous system plasticity. Inflammatory and neuropathic pain rely on plasticity, presenting a clinical opportunity for the use of NMDAR antagonists and NOS inhibitors in chronic pain. Agmatine (AG), an endogenous neuromodulator present in brain and spinal cord, has both NMDAR antagonist and NOS inhibitor activities. We report here that AG, exogenously administered to rodents, decreased hyperalgesia accompanying inflammation, normalized the mechanical hypersensitivity (allodynia/hyperalgesia) produced by chemical or mechanical nerve injury, and reduced autotomy-like behavior and lesion size after excitotoxic spinal cord injury. AG produced these effects in the absence of antinociceptive effects in acute pain tests. Endogenous AG also was detected in rodent lumbosacral spinal cord in concentrations similar to those previously detected in brain. The evidence suggests a unique antiplasticity and neuroprotective role for AG in processes underlying persistent pain and neuronal injury.

24(S)-Hydroxycholesterol as a modulator of neuronal signaling and survival

PubMed Central

Sun, Min Yu; Linsenbardt, Andrew; Emnett, Christine; Eisenman, Lawrence N.; Izumi, Yukitoshi; Zorumski, Charles; Mennerick, Steve

2016-01-01

The major cholesterol metabolite in brain, 24S-hydroxycholesterol (24S-HC), serves as a vehicle for cholesterol removal. Its effects on neuronal function, however, have only recently begun to be investigated. Here we review that nascent work. Our own studies have demonstrated that 24S-HC has potent positive modulatory effects on NMDA receptor (NMDAR) function. This could have implications for brain plasticity but also for pathological NMDAR overuse. Other work has demonstrated effects of 24S-HC on neuronal survival and as a possible biomarker of neurodegenerative disease. Depending on circumstances, both upregulation/mimicry of 24S-HC signaling and downregulation/antagonism may have therapeutic potential. We are interested in the possibility that synthetic analogues of 24S-HC with positive effects at NMDARs may hold neurotherapeutic promise, given the role of NMDA receptor hypofunction in certain neuropsychiatric disorders. PMID:25628343

Novel nootropic drug sunifiram enhances hippocampal synaptic efficacy via glycine-binding site of N-methyl-D-aspartate receptor.

PubMed

Moriguchi, Shigeki; Tanaka, Tomoya; Narahashi, Toshio; Fukunaga, Kohji

2013-10-01

Sunifiram is a novel pyrrolidone nootropic drug structurally related to piracetam, which was developed for neurodegenerative disorder like Alzheimer's disease. Sunifiram is known to enhance cognitive function in some behavioral experiments such as Morris water maze task. To address question whether sunifiram affects N-methyl-D-aspartate receptor (NMDAR)-dependent synaptic function in the hippocampal CA1 region, we assessed the effects of sunifiram on NMDAR-dependent long-term potentiation (LTP) by electrophysiology and on phosphorylation of synaptic proteins by immunoblotting analysis. In mouse hippocampal slices, sunifiram at 10-100 nM significantly enhanced LTP in a bell-shaped dose-response relationship which peaked at 10 nM. The enhancement of LTP by sunifiram treatment was inhibited by 7-chloro-kynurenic acid (7-ClKN), an antagonist for glycine-binding site of NMDAR, but not by ifenprodil, an inhibitor for polyamine site of NMDAR. The enhancement of LTP by sunifilam was associated with an increase in phosphorylation of α-amino-3-hydroxy-5-methylisozazole-4-propionate receptor (AMPAR) through activation of calcium/calmodulin-dependent protein kinase II (CaMKII) and an increase in phosphorylation of NMDAR through activation of protein kinase Cα (PKCα). Sunifiram treatments at 1-1000 nM increased the slope of field excitatory postsynaptic potentials (fEPSPs) in a dose-dependent manner. The enhancement was associated with an increase in phosphorylation of AMPAR receptor through activation of CaMKII. Interestingly, under the basal condition, sunifiram treatments increased PKCα (Ser-657) and Src family (Tyr-416) activities with the same bell-shaped dose-response curve as that of LTP peaking at 10 nM. The increase in phosphorylation of PKCα (Ser-657) and Src (Tyr-416) induced by sunifiram was inhibited by 7-ClKN treatment. The LTP enhancement by sunifiram was significantly inhibited by PP2, a Src family inhibitor. Finally, when pretreated with a high concentration of glycine (300 μM), sunifiram treatments failed to potentiate LTP in the CA1 region. Taken together, sunifiram stimulates the glycine-binding site of NMDAR with concomitant PKCα activation through Src kinase. Enhancement of PKCα activity triggers to potentiate hippocampal LTP through CaMKII activation. Copyright © 2013 Wiley Periodicals, Inc.

Effects of infrasound at 8 Hz 90 dB/130 dB on NMDAR1 expression and changes in intracellular calcium ion concentration in the hippocampus of rats.

PubMed

Liu, Zhao-Hui; Chen, Jing-Zao; Ye, Lin; Liu, Jing; Qiu, Jian-Yong; Xu, Jian; Lu, Rui; Yuan, Xiao-Chao; Zhang, Wen-Dong; Li, Xiao-Fang; Li, Gong

2010-01-01

In the present study, we investigated the effect of infrasound on the expression of N-methyl-D-aspartate (NMDAR)1 as well as changes in intracellular calcium ion concentration ([Ca2+]i) in the hippocampus of rats. Sprague-Dawley (SD) rats were exposed for 2 h daily to infrasound at 8 Hz 90 dB or 130 dB, and NMDAR1 expression was examined on days 1, 7, 14, 21 and 28. The expression of NMDAR1 in the rat hippocampus upon exposure to infrasound at 8 Hz 90 dB sound pressure level (SPL) showed an initial decrease on day 1, an increase on days 7 and 14, a further decrease on day 21, and a return to normal levels on day 28. The peak level was observed on day 14 in every examined subregion of the hippocampus. By contrast, exposure to infrasound at 8 Hz 130 dB SPL had opposite effects, showing an increase on day 1, a decrease on day 7, a decrease to the lowest point on days 14, another increase on day 21 and a return to normal levels on day 28. The lowest expression of NMDAR1 was found in the CA1 and CA3 regions on day 14 and in the DG region on day 7 with exposure at 130 dB. There were significant differences in [Ca2+]i concentration on days 14 and 21 with infrasonic exposure at both 8 Hz 90 dB and 130 dB, but no significant differences in [Ca2+]i concentration on days 1, 7 and 28 compared to the control group. The highest [Ca2+]i level was noted on day 14 with infrasound exposure at 8 Hz 130 dB. These changes suggest that 8 Hz 90 dB/130 dB infrasound exposure induced certain reversible changes in NMDAR1 expression and [Ca2+]i concentration in hippocampal cells, which may influence mnemonic functions related to the hippocampus.

Memory retrieval in response to partial cues requires NMDA receptor-dependent neurotransmission in the medial prefrontal cortex.

PubMed

Jo, Yong Sang; Choi, June-Seek

2014-03-01

The medial prefrontal cortex (mPFC) has been suggested to play a crucial role in retrieving detailed contextual information about a previous learning episode in response to a single retrieval cue. However, few studies investigated the neurochemical mechanisms that mediate the prefrontal retrieval process. In the current study, we examined whether N-methyl-D-aspartate receptors (NMDARs) in the mPFC were necessary for retrieval of a well-learned spatial location on the basis of partial or degraded spatial cues. Rats were initially trained to find a hidden platform in the Morris water maze using four extramaze cues in the surrounding environment. Their retrieval performance was subsequently tested under different cue conditions. Infusions of DL-2-amino-5-phosphonovaleric acid (APV), a NMDAR antagonist, significantly disrupted memory retrieval when three of the original cues were removed. By contrast, APV injections into the mPFC did not affect animals' retrieval performance when the original cues were presented or when three novels landmarks were added alongside the original cues. These results indicate that prefrontal NMDARs are required for memory retrieval when allocentric spatial information is degraded. NMDAR-dependent neurotransmission in the mPFC may facilitate an active retrieval process to reactivate complete contextual representations associated with partial retrieval cues. Copyright © 2013 Elsevier Inc. All rights reserved.

Selective cognitive impairments associated with NMDA receptor blockade in humans.

PubMed

Rowland, Laura M; Astur, Robert S; Jung, Rex E; Bustillo, Juan R; Lauriello, John; Yeo, Ronald A

2005-03-01

Hypofunction of the N-methyl-D-aspartate receptor (NMDAR) may be involved in the pathophysiology of schizophrenia. NMDAR antagonists like ketamine induce schizophrenia-like features in humans. In rodent studies, NMDAR antagonism impairs learning by disrupting long-term potentiation (LTP) in the hippocampus. This study investigated the effects of ketamine on spatial learning (acquisition) vs retrieval in a virtual Morris water task in humans. Verbal fluency, working memory, and learning and memory of verbal information were also assessed. Healthy human subjects participated in this double-blinded, placebo-controlled study. On two separate occasions, ketamine/placebo was administered and cognitive tasks were assessed in association with behavioral ratings. Ketamine impaired learning of spatial and verbal information but retrieval of information learned prior to drug administration was preserved. Schizophrenia-like symptoms were significantly related to spatial and verbal learning performance. Ketamine did not significantly impair attention, verbal fluency, or verbal working memory task performance. Spatial working memory was slightly impaired. In conclusion, these results provide evidence for ketamine's differential impairment of verbal and spatial learning vs retrieval. By using the Morris water task, which is hippocampal-dependent, this study helps bridge the gap between nonhuman animal and human NMDAR antagonism research. Impaired cognition is a core feature of schizophrenia. A better understanding of NMDA antagonism, its physiological and cognitive consequences, may provide improved models of psychosis and cognitive therapeutics.

Novel human D-amino acid oxidase inhibitors stabilize an active-site lid-open conformation

PubMed Central

Terry-Lorenzo, Ryan T.; Chun, Lawrence E.; Brown, Scott P.; Heffernan, Michele L. R.; Fang, Q. Kevin; Orsini, Michael A.; Pollegioni, Loredano; Hardy, Larry W.; Spear, Kerry L.; Large, Thomas H.

2014-01-01

The NMDAR (N-methyl-D-aspartate receptor) is a central regulator of synaptic plasticity and learning and memory. hDAAO (human D-amino acid oxidase) indirectly reduces NMDAR activity by degrading the NMDAR co-agonist D-serine. Since NMDAR hypofunction is thought to be a foundational defect in schizophrenia, hDAAO inhibitors have potential as treatments for schizophrenia and other nervous system disorders. Here, we sought to identify novel chemicals that inhibit hDAAO activity. We used computational tools to design a focused, purchasable library of compounds. After screening this library for hDAAO inhibition, we identified the structurally novel compound, ‘compound 2’ [3-(7-hydroxy-2-oxo-4-phenyl-2H-chromen-6-yl)propanoic acid], which displayed low nM hDAAO inhibitory potency (Ki=7 nM). Although the library was expected to enrich for compounds that were competitive for both D-serine and FAD, compound 2 actually was FAD uncompetitive, much like canonical hDAAO inhibitors such as benzoic acid. Compound 2 and an analog were independently co-crystalized with hDAAO. These compounds stabilized a novel conformation of hDAAO in which the active-site lid was in an open position. These results confirm previous hypotheses regarding active-site lid flexibility of mammalian D-amino acid oxidases and could assist in the design of the next generation of hDAAO inhibitors. PMID:25001371

AMELIORATING TREATMENT-REFRACTORY DEPRESSION WITH INTRANASAL KETAMINE: POTENTIAL NMDA RECEPTOR ACTIONS IN THE PAIN CIRCUITRY REPRESENTING MENTAL ANGUISH

PubMed Central

Opler, Lewis A.; Opler, Mark G.; Arnsten, Amy F.T.

2014-01-01

This paper reviews the anti-depressant actions of the N-methyl-D-aspartame glutamate receptor (NMDAR) antagonist, ketamine, and offers a potential neural mechanism for intranasal ketamine’s ultra-rapid actions based on the key role of NMDAR in the nonhuman primate prefrontal cortex (PFC). Although intravenous ketamine infusions can lift mood within hours, the current review describes how intranasal ketamine administration can have ultra-rapid antidepressant effects, beginning within minutes (5–40 minutes) and lasting hours, but with repeated treatments needed for sustained antidepressant actions. Research in rodents suggests that increased synaptogenesis in PFC may contribute to the prolonged benefit of ketamine administration, beginning hours after administration. However, these data cannot explain the relief that occurs within minutes of intranasal ketamine delivery. We hypothesize that the ultra-rapid effects of intranasal administration in humans may be due to ketamine blocking the NMDAR circuits that generate the emotional representations of pain (e.g. Brodmann Areas 24 and 25, insular cortex), cortical areas that can be overactive in depression and which sit above the nasal epithelium. In contrast, NMDAR blockade in the dorsolateral PFC following systemic administration of ketamine may contribute to cognitive deficits. This novel view may help to explain how intravenous ketamine can treat the symptoms of depression yet worsen the symptoms of schizophrenia. PMID:25619798

Age-Dependent Long-Term Potentiation Deficits in the Prefrontal Cortex of the Fmr1 Knockout Mouse Model of Fragile X Syndrome.

PubMed

Martin, Henry G S; Lassalle, Olivier; Brown, Jonathan T; Manzoni, Olivier J

2016-05-01

The most common inherited monogenetic cause of intellectual disability is Fragile X syndrome (FXS). The clinical symptoms of FXS evolve with age during adulthood; however, neurophysiological data exploring this phenomenon are limited. The Fmr1 knockout (Fmr1KO) mouse models FXS, but studies in these mice of prefrontal cortex (PFC) function are underrepresented, and aging linked data are absent. We studied synaptic physiology and activity-dependent synaptic plasticity in the medial PFC of Fmr1KO mice from 2 to 12 months. In young adult Fmr1KO mice, NMDA receptor (NMDAR)-mediated long-term potentiation (LTP) is intact; however, in 12-month-old mice this LTP is impaired. In parallel, there was an increase in the AMPAR/NMDAR ratio and a concomitant decrease of synaptic NMDAR currents in 12-month-old Fmr1KO mice. We found that acute pharmacological blockade of mGlu5 receptor in 12-month-old Fmr1KO mice restored a normal AMPAR/NMDAR ratio and LTP. Taken together, the data reveal an age-dependent deficit in LTP in Fmr1KO mice, which may correlate to some of the complex age-related deficits in FXS. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Roles of N-methyl-d-aspartate receptors during the sensory stimulation-evoked field potential responses in mouse cerebellar cortical molecular layer.

PubMed

Xu, Yin-Hua; Zhang, Guang-Jian; Zhao, Jing-Tong; Chu, Chun-Ping; Li, Yu-Zi; Qiu, De-Lai

2017-11-01

The functions of N-methyl-d-aspartate receptors (NMDARs) in cerebellar cortex have been widely studied under in vitro condition, but their roles during the sensory stimulation-evoked responses in the cerebellar cortical molecular layer in living animals are currently unclear. We here investigated the roles of NMDARs during the air-puff stimulation on ipsilateral whisker pad-evoked field potential responses in cerebellar cortical molecular layer in urethane-anesthetized mice by electrophysiological recording and pharmacological methods. Our results showed that cerebellar surface administration of NMDA induced a dose-dependent decrease in amplitude of the facial stimulation-evoked inhibitory responses (P1) in the molecular layer, accompanied with decreases in decay time, half-width and area under curve (AUC) of P1. The IC 50 of NMDA induced inhibition in amplitude of P1 was 46.5μM. In addition, application of NMDA induced significant increases in the decay time, half-width and AUC values of the facial stimulation-evoked excitatory responses (N1) in the molecular layer. Application of an NMDAR blocker, D-APV (250μM) abolished the facial stimulation-evoked P1 in the molecular layer. These results suggested that NMDARs play a critical role during the sensory information processing in cerebellar cortical molecular layer in vivo in mice. Copyright © 2017 Elsevier B.V. All rights reserved.

Testing synaptic plasticity in dynamic mate choice decisions: N-methyl d-aspartate receptor blockade disrupts female preference

PubMed Central

Ramsey, Mary E.; Vu, Wendy; Cummings, Molly E.

2014-01-01

Social behaviours such as mate choice require context-specific responses, often with evolutionary consequences. Increasing evidence indicates that the behavioural plasticity associated with mate choice involves learning. For example, poeciliids show age-dependent changes in female preference functions and express synaptic-plasticity-associated molecular markers during mate choice. Here, we test whether social cognition is necessary for female preference behaviour by blocking the central player in synaptic plasticity, NMDAR (N-methyl d-aspartate receptor), in a poeciliid fish, Xiphophorus nigrensis. After subchronic exposure to NMDAR antagonist MK-801, female preference behaviours towards males were dramatically reduced. Overall activity levels were unaffected, but there was a directional shift from ‘social’ behaviours towards neutral activity. Multivariate gene expression patterns significantly discriminated between females with normal versus disrupted plasticity processes and correlated with preference behaviours—not general activity. Furthermore, molecular patterns support a distinction between ‘preference’ (e.g. neuroserpin, neuroligin-3, NMDAR) and ‘sociality’ (isotocin and vasotocin) gene clusters, highlighting a possible conservation between NMDAR disruption and nonapeptides in modulating behaviour. Our results suggest that mate preference may involve greater social memory processing than overall sociality, and that poeciliid preference functions integrate synaptic-plasticity-oriented ‘preference’ pathways with overall sociality to invoke dynamic, context-specific responses towards favoured males and away from unfavoured males. PMID:24807251

Antidepressant-like effects induced by NMDA receptor blockade and NO synthesis inhibition in the ventral medial prefrontal cortex of rats exposed to the forced swim test.

PubMed

Pereira, Vitor Silva; Romano, Angélica; Wegener, Gregers; Joca, Sâmia R L

2015-07-01

Systemic treatment with NMDA receptor (NMDAR) antagonists, inhibitors of neuronal nitric oxide synthase (nNOS) or of soluble guanylyl cyclase (sGC), induce antidepressant-like effects in rats. Increased levels of glutamate and nitric oxide (NO) in the medial prefrontal cortex (MPFC) of stressed animals have been described in the literature. However, the role of the NMDAR-nNOS-sGC pathway of the MPFC in the mediation of forced swim-induced behaviors remains unclear. The aim of this work was to test the hypothesis that the inhibition of the NMDAR-nNOS-sGC pathway in the ventral MPFC (infralimbic (IL) or prelimbic (PL)) would elicit antidepressant-like effects in the forced swim test (FST). Rats implanted with cannulae aimed at the PL or the IL were exposed to the FST and injected with LY235959 (NMDAR antagonist), NPA (nNOS inhibitor), ODQ (sGC inhibitor), or carboxy-PTIO (NO scavenger). Additional groups received the AMPA antagonist, NBQX, before the effective doses of LY235959 or NPA. LY235959 administration into PL or IL before the FS pretest produced no effects. Administration of LY235959 (3 and 10 nmol/0.2 μL) after pretest was effective only when administered into the PL. However, the administration of NPA (0.01 nmol/0.2 μL), c-PTIO (1.0 nmol/0.2 μL), and ODQ (1.0 nmol/0.2 μL) into the PL or IL before the FST produced antidepressant-like effects. NBQX blocked the antidepressant-like effect of LY235959 but not of NPA. Blocking NMDAR or NO signaling in the vMPFC, either in the IL or the PL, induces antidepressant-like effects in the rat FST. These effects seemingly occur through independent mechanisms, since NBQX blocked the former effect but not the latter.

Spinal NMDA receptor activation constrains inactivity-induced phrenic motor facilitation in Charles River Sprague-Dawley rats

PubMed Central

Streeter, K. A.

2014-01-01

Reduced spinal synaptic inputs to phrenic motor neurons elicit a unique form of spinal plasticity known as inactivity-induced phrenic motor facilitation (iPMF). iPMF requires tumor necrosis factor-α (TNF-α) and atypical protein kinase C (aPKC) activity within spinal segments containing the phrenic motor nucleus to stabilize early, transient increases in phrenic burst amplitude into long-lasting iPMF. Here we tested the hypothesis that spinal N-methyl-d-aspartate receptor (NMDAR) activation constrains long-lasting iPMF in some rat substrains. Phrenic motor output was recorded in anesthetized, ventilated Harlan (HSD) and Charles River (CRSD) Sprague-Dawley rats exposed to a 30-min central neural apnea. HSD rats expressed a robust, long-lasting (>60 min) increase in phrenic burst amplitude (i.e., long-lasting iPMF) when respiratory neural activity was restored. By contrast, CRSD rats expressed an attenuated, transient (∼15 min) iPMF. Spinal NMDAR inhibition with DL-2-amino-5-phosphonopentanoic acid (APV) before neural apnea or shortly (4 min) prior to the resumption of respiratory neural activity revealed long-lasting iPMF in CRSD rats that was phenotypically similar to that in HSD rats. By contrast, APV did not alter iPMF expression in HSD rats. Spinal TNF-α or aPKC inhibition impaired long-lasting iPMF enabled by NMDAR inhibition in CRSD rats, suggesting that similar mechanisms give rise to long-lasting iPMF in CRSD rats with NMDAR inhibition as those giving rise to long-lasting iPMF in HSD rats. These results suggest that NMDAR activation can impose constraints on TNF-α-induced aPKC activation after neural apnea, impairing stabilization of transient iPMF into long-lasting iPMF. These data may have important implications for understanding differential responses to reduced respiratory neural activity in a heterogeneous human population. PMID:25103979

Neuronal surface antigen antibodies in limbic encephalitis

PubMed Central

Graus, F; Saiz, A; Lai, M; Bruna, J; López, F; Sabater, L; Blanco, Y; Rey, M J.; Ribalta, T; Dalmau, J

2008-01-01

Objective: To report the frequency and type of antibodies against neuronal surface antigens (NSA-ab) in limbic encephalitis (LE). Methods: Analysis of clinical features, neuropathologic findings, and detection of NSA-ab using immunochemistry on rat tissue and neuronal cultures in a series of 45 patients with paraneoplastic (23) or idiopathic (22) LE. Results: NSA-ab were identified in 29 patients (64%; 12 paraneoplastic, 17 idiopathic). Thirteen patients had voltage-gated potassium channels (VGKC)-ab, 11 novel NSA (nNSA)-ab, and 5 NMDA receptor (NMDAR)-ab. nNSA-ab did not identify a common antigen and were more frequent in paraneoplastic than idiopathic LE (39% vs 9%; p = 0.03). When compared with VGKC-ab or NMDAR-ab, the nNSA associated more frequently with intraneuronal antibodies (11% vs 73%; p = 0.001). Of 12 patients (9 nNSA-ab, 2 VGKC-ab, 1 NMDAR-ab) with paraneoplastic LE and NSA-ab, concomitant intraneuronal antibodies occurred in 9 (75%). None of these 12 patients improved with immunotherapy. The autopsy of three of them showed neuronal loss, microgliosis, and cytotoxic T cell infiltrates in the hippocampus and amygdala. These findings were compatible with a T-cell mediated neuronal damage. In contrast, 13 of 17 (76%) patients with idiopathic LE and NSA-ab (8 VGKC-ab, 4 NMDAR-ab, 1 nNSA-ab) and 1 of 5 (20%) without antibodies had clinical improvement (p = 0.04). Conclusions: In paraneoplastic limbic encephalitis (LE), novel antibodies against neuronal surface antigens (nNSA-ab) occur frequently, coexist with antibodies against intracellular antigens, and these cases are refractory to immunotherapy. In idiopathic LE, the likelihood of improvement is significantly higher in patients with NSA-ab than in those without antibodies. GLOSSARY GAD = glutamic acid decarboxylase; LE = limbic encephalitis; NMDAR = N-methyl-D-aspartate receptor; NSA = neuronal surface antigens; nNSA = novel NSA; SCLC = small-cell lung cancer; VGKC = voltage-gated potassium channels; WBC = white blood cells. PMID:18794496

A PK-PD model of ketamine-induced high-frequency oscillations

NASA Astrophysics Data System (ADS)

Flores, Francisco J.; Ching, ShiNung; Hartnack, Katharine; Fath, Amanda B.; Purdon, Patrick L.; Wilson, Matthew A.; Brown, Emery N.

2015-10-01

Objective. Ketamine is a widely used drug with clinical and research applications, and also known to be used as a recreational drug. Ketamine produces conspicuous changes in the electrocorticographic (ECoG) signals observed both in humans and rodents. In rodents, the intracranial ECoG displays a high-frequency oscillation (HFO) which power is modulated nonlinearly by ketamine dose. Despite the widespread use of ketamine there is no model description of the relationship between the pharmacokinetic-pharmacodynamics (PK-PDs) of ketamine and the observed HFO power. Approach. In the present study, we developed a PK-PD model based on estimated ketamine concentration, its known pharmacological actions, and observed ECoG effects. The main pharmacological action of ketamine is antagonism of the NMDA receptor (NMDAR), which in rodents is accompanied by an HFO observed in the ECoG. At high doses, however, ketamine also acts at non-NMDAR sites, produces loss of consciousness, and the transient disappearance of the HFO. We propose a two-compartment PK model that represents the concentration of ketamine, and a PD model based in opposing effects of the NMDAR and non-NMDAR actions on the HFO power. Main results. We recorded ECoG from the cortex of rats after two doses of ketamine, and extracted the HFO power from the ECoG spectrograms. We fit the PK-PD model to the time course of the HFO power, and showed that the model reproduces the dose-dependent profile of the HFO power. The model provides good fits even in the presence of high variability in HFO power across animals. As expected, the model does not provide good fits to the HFO power after dosing the pure NMDAR antagonist MK-801. Significance. Our study provides a simple model to relate the observed electrophysiological effects of ketamine to its actions at the molecular level at different concentrations. This will improve the study of ketamine and rodent models of schizophrenia to better understand the wide and divergent range of effects that ketamine has.

Effects of neurosteroid actions at N-methyl-D-aspartate and GABA A receptors in the midbrain ventral tegmental area for anxiety-like and mating behavior of female rats.

PubMed

Frye, Cheryl A; Paris, Jason J

2011-01-01

In the midbrain ventral tegmental area (VTA), actions of neurosteroids, such as the progesterone metabolite, 5α-pregnan-3α-ol-20-one (3α,5α-THP), can facilitate mating and influence stress-related processes. Some actions of 3α,5α-THP may occur via positive modulation of GABA(A) receptors (GBRs), or negative modulation of N-methyl-D: -aspartate receptors (NMDARs), to influence anxiety-like behavior; but this is not known. We aimed to assess the role that neurosteroids and stress factors play on intra-VTA NMDAR- and/or GBR-mediated anxiety-like and mating behavior. Estradiol-primed, ovariectomized rats, which were partially or completely adrenalectomized (ADX), received infusions of vehicle, an NMDAR blocker (MK-801; 200 ng), or a GBR antagonist (bicuculline, 100 ng) to the VTA. Rats then received intra-VTA vehicle or a neurosteroidogenesis enhancer (N,N-Dihexyl-2-(4-fluorophenyl)indole-3-acetamide, FGIN 1-27, 5 μg) and anxiety-like and sexual behavior was assessed. Complete, compared to partial, ADX significantly reduced open arm exploration on an elevated plus maze, the proportion of females that engaged in mating, lordosis quotients, pacing of sexual contacts, and defensive aggression towards a sexually vigorous male. Intra-VTA MK-801 enhanced open arm investigation and the proportion of females that engaged in mating. Infusions of either, MK-801 or FGIN 1-27, enhanced lordosis and, when co-administered, FGIN 1-27 attenuated MK-801's lordosis-enhancing effects. Intra-VTA infusions of bicuculline, prior to FGIN 1-27, blocked FGIN 1-27's effects to enhance lordosis. Together, these data suggest that reduced NMDAR activity in the VTA may influence motivation to explore and engage in sexual behavior. These data suggest that neurosteroid actions at NMDARs and GBRs in the VTA are important for exploration and/or sexual behavior.

Effects of neurosteroid actions at N-methyl-D-aspartate and GABAA receptors in the midbrain ventral tegmental area for anxiety-like and mating behavior of female rats

PubMed Central

Paris, Jason J.

2013-01-01

Rationale In the midbrain ventral tegmental area (VTA), actions of neurosteroids, such as the progesterone metabolite, 5α-pregnan-3α-ol-20-one (3α,5α-THP), can facilitate mating and influence stress-related processes. Some actions of 3α,5α-THP may occur via positive modulation of GABAA receptors (GBRs), or negative modulation of N-methyl-D-aspartate receptors (NMDARs), to influence anxiety-like behavior; but this is not known. Objectives We aimed to assess the role that neurosteroids and stress factors play on intra-VTA NMDAR- and/or GBR-mediated anxiety-like and mating behavior. Methods Estradiol-primed, ovariectomized rats, which were partially or completely adrenalectomized (ADX), received infusions of vehicle, an NMDAR blocker (MK-801; 200 ng), or a GBR antagonist (bicuculline, 100 ng) to the VTA. Rats then received intra-VTA vehicle or a neurosteroidogenesis enhancer (N,N-Dihexyl-2-(4-fluorophenyl)indole-3-acetamide, FGIN 1-27, 5 μg) and anxiety-like and sexual behavior was assessed. Results Complete, compared to partial, ADX significantly reduced open arm exploration on an elevated plus maze, the proportion of females that engaged in mating, lordosis quotients, pacing of sexual contacts, and defensive aggression towards a sexually vigorous male. Intra-VTA MK-801 enhanced open arm investigation and the proportion of females that engaged in mating. Infusions of either, MK-801 or FGIN 1-27, enhanced lordosis and, when co-administered, FGIN 1-27 attenuated MK-801’s lordosis-enhancing effects. Intra-VTA infusions of bicuculline, prior to FGIN 1-27, blocked FGIN 1-27’s effects to enhance lordosis. Conclusions Together, these data suggest that reduced NMDAR activity in the VTA may influence motivation to explore and engage in sexual behavior. These data suggest that neurosteroid actions at NMDARs and GBRs in the VTA are important for exploration and/or sexual behavior. PMID:20878318

Phencyclidine Disrupts the Auditory Steady State Response in Rats

PubMed Central

Leishman, Emma; O’Donnell, Brian F.; Millward, James B.; Vohs, Jenifer L.; Rass, Olga; Krishnan, Giri P.; Bolbecker, Amanda R.; Morzorati, Sandra L.

2015-01-01

The Auditory Steady-State Response (ASSR) in the electroencephalogram (EEG) is usually reduced in schizophrenia (SZ), particularly to 40 Hz stimulation. The gamma frequency ASSR deficit has been attributed to N-methyl-D-aspartate receptor (NMDAR) hypofunction. We tested whether the NMDAR antagonist, phencyclidine (PCP), produced similar ASSR deficits in rats. EEG was recorded from awake rats via intracranial electrodes overlaying the auditory cortex and at the vertex of the skull. ASSRs to click trains were recorded at 10, 20, 30, 40, 50, and 55 Hz and measured by ASSR Mean Power (MP) and Phase Locking Factor (PLF). In Experiment 1, the effect of different subcutaneous doses of PCP (1.0, 2.5 and 4.0 mg/kg) on the ASSR in 12 rats was assessed. In Experiment 2, ASSRs were compared in PCP treated rats and control rats at baseline, after acute injection (5 mg/kg), following two weeks of subchronic, continuous administration (5 mg/kg/day), and one week after drug cessation. Acute administration of PCP increased PLF and MP at frequencies of stimulation below 50 Hz, and decreased responses at higher frequencies at the auditory cortex site. Acute administration had a less pronounced effect at the vertex site, with a reduction of either PLF or MP observed at frequencies above 20 Hz. Acute effects increased in magnitude with higher doses of PCP. Consistent effects were not observed after subchronic PCP administration. These data indicate that acute administration of PCP, a NMDAR antagonist, produces an increase in ASSR synchrony and power at low frequencies of stimulation and a reduction of high frequency (> 40 Hz) ASSR activity in rats. Subchronic, continuous administration of PCP, on the other hand, has little impact on ASSRs. Thus, while ASSRs are highly sensitive to NMDAR antagonists, their translational utility as a cross-species biomarker for NMDAR hypofunction in SZ and other disorders may be dependent on dose and schedule. PMID:26258486

Antenatal blockade of N-methyl-D-aspartate receptors by Memantine reduces the susceptibility to diabetes induced by a high-fat diet in rats with intrauterine growth restriction.

PubMed

Huang, Xiao-Ting; Yue, Shao-Jie; Li, Chen; Guo, Jia; Huang, Yan-Hong; Han, Jian-Zhong; Feng, Dan-Dan; Luo, Zi-Qiang

2017-05-01

Intrauterine growth retardation (IUGR) is closely related to the later development of type 2 diabetes in adulthood. Excessive activation of N-methly-D-aspartate receptors (NMDARs) causes excitatory neurotoxicity, resulting in neuronal injury or death. Inhibition of NMDARs enhances the glucose-stimulated insulin secretion and survival of islet cells in type 2 diabetic mouse and human islets. Here, we examined whether antenatal blockade of NMDARs by Memantine could decrease the risk of diabetes induced by a high-fat (HF) diet at adulthood in IUGR rats. Pregnant SD rats were assigned to four groups: control, IUGR, Memantine, and Memantine + IUGR. The pregnant rats were exposed to hypoxic conditions (FiO2 = 0.105) for 8 h/day (IUGR group) or given a daily Memantine injection (5 mg/kg, i.p.) before hypoxia exposure from embryonic day (E) 14.5 to E 20.5 (Memantine + IUGR). The offspring were fed an HF diet with 60% of the calories from age 4 to 12 weeks. We found that NMDAR mRNAs were expressed in the fetal rat pancreas. An HF diet resulted in a high rate of diabetes at adulthood in the IUGR group. Antenatal Memantine treatment decreased the risk of diabetes at adulthood of rats with IUGR, which was associated with rescued glucose tolerance, increased insulin release, improved the insulin sensitivity, and increased expression of genes related to beta-cell function in the pancreas. Together, our results suggest that antenatal blockade of NMDARs by Memantine in pregnant rats improves fetal development and reduces the susceptibility to diabetes at adulthood in offspring. © The Authors 2017. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

A case report: anti-NMDA receptor encephalitis

PubMed Central

Bhat, Pavan; Ahmed, Ameer; Jolepalem, Preetam; Sittambalam, Charmian

2018-01-01

ABSTRACT N-methyl-d-aspartate receptor (NMDAR) antibody encephalitis is a potentially fatal autoimmune syndrome in which there is antibody production against the NMDAR causing profound dysregulation of neurotransmission. The syndrome is frequently associated with ovarian teratomas and women are disproportionately affected. Patients most often present with a constellation of neuropsychiatric signs and symptoms, including memory loss, hallucinations, and decreased level of consciousness. This condition is lethal if left untreated. Immunotherapy and surgical resection of the culprit malignancy often results in the rapid resolution of symptoms. PMID:29915659

Subunit Compositions of the RNA-Silencing Enzymes Pol IV and Pol V Reveal Their Origins as Specialized Forms of RNA Polymerase II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ream, Thomas S.; Haag, J. R.; Wierzbicki, A. T.

2009-01-30

In addition to RNA polymerases I, II and III, which are multi-subunit RNA polymerases found in all eukaryotes, plants have catalytic subunits for two additional nuclear RNA polymerases, abbreviated as Pol IV and Pol V (formerly Pol IVa and Pol IVb, respectively). Pol IV and Pol V play non-redundant roles in siRNA-directed DNA methylation and gene silencing pathways.

Amygdala Infusions of an NR2B-Selective or an NR2A-Preferring NMDA Receptor Antagonist Differentially Influence Fear Conditioning and Expression in the Fear-Potentiated Startle Test

ERIC Educational Resources Information Center

Walker, David L.; Davis, Michael

2008-01-01

Within the amygdala, most N-methyl-D-aspartic acid (NMDA) receptors consist of NR1 subunits in combination with either NR2A or NR2B subunits. Because the particular subunit composition greatly influences the receptors' properties, we investigated the contribution of both subtypes to fear conditioning and expression. To do so, we infused the…

Subunit stoichiometry of the CNG channel of rod photoreceptors.

PubMed

Weitz, Dietmar; Ficek, Nicole; Kremmer, Elisabeth; Bauer, Paul J; Kaupp, U Benjamin

2002-12-05

Cyclic nucleotide-gated (CNG) channels play a central role in the conversion of sensory stimuli into electrical signals. CNG channels form heterooligomeric complexes built of A and B subunits. Here, we study the subunit stoichiometry of the native rod CNG channel by chemical crosslinking. The apparent molecular weight (M(w)) of each crosslink product was determined by SDS-PAGE, and its composition was analyzed by Western blotting using antibodies specific for the A1 or B1 subunit. The number of crosslink products and their M(w) as well as the immunological identification of A1 and B1 subunits in the crosslink products led us to conclude that the native rod CNG channel is a tetramer composed of three A1 and one B1 subunit. This is an example of violation of symmetry in tetrameric channels.

Construction and characterization of the hetero-oligomer of the group II chaperonin from the hyperthermophilic archaeon, Thermococcus sp. strain KS-1.

PubMed

Sahlan, Muhamad; Kanzaki, Taro; Yohda, Masafumi

2009-05-01

The hyperthermophilic archaeon Thermococcus sp. strain KS-1 (T. KS-1) expresses two different chaperonin subunits, alpha and beta, for the folding of its proteins. The composition of the subunits in the hexadecameric double ring changes with temperature. The content of the beta subunit significantly increases according to the increase in temperature. The homo-oligomer of the beta subunit, Cpn beta, is more thermostable than that of the alpha subunit, Cpn alpha. Since Cpn alpha and Cpn beta also have different protein folding activities and interactions with prefoldin, the hetero-oligomer is thought to exhibit different characteristics according to the content of subunits. The hetero-oligomer of the T. KS-1 chaperonin has not been studied, however, because the alpha and beta subunits form hetero-oligomers of varying compositions when they are expressed simultaneously. In this study, we characterized the T. KS-1 chaperonin hetero-oligomer, Cpn alphabeta, containing both alpha and beta in the alternate order, which was constructed by the expression of alpha and beta subunits in a coordinated fashion and protease digestion. Cpn alphabeta protected citrate synthase from thermal aggregation, promoted the folding of acid-denatured GFP in an ATP-dependent manner, and exhibited an ATP-dependent conformational change. The yield of refolded GFP generated by Cpn alphabeta was almost equivalent to that generated by Cpn beta but lower than that generated by Cpn alpha. In contrast, Cpn alphabeta exhibited almost the same level of thermal stability as Cpn alpha, which was lower than that of Cpn beta. The affinity of Cpn alphabeta to prefoldin was found to be between those of Cpn alpha and Cpn beta, as expected.

Functional reconstitution of the Mycobacterium tuberculosis long-chain acyl-CoA carboxylase from multiple acyl-CoA subunits.

PubMed

Bazet Lyonnet, Bernardo; Diacovich, Lautaro; Gago, Gabriela; Spina, Lucie; Bardou, Fabienne; Lemassu, Anne; Quémard, Annaïk; Gramajo, Hugo

2017-04-01

Mycobacterium tuberculosis produces a large number of structurally diverse lipids that have been implicated in the pathogenicity, persistence and antibiotic resistance of this organism. Most building blocks involved in the biosynthesis of all these lipids are generated by acyl-CoA carboxylases whose subunit composition and physiological roles have not yet been clearly established. Inconclusive data in the literature refer to the exact protein composition and substrate specificity of the enzyme complex that produces the long-chain α-carboxy-acyl-CoAs, which are substrates involved in the last step of condensation mediated by the polyketide synthase 13 to synthesize mature mycolic acids. Here we have successfully reconstituted the long-chain acyl-CoA carboxylase (LCC) complex from its purified components, the α subunit (AccA3), the ε subunit (AccE5) and the two β subunits (AccD4 and AccD5), and demonstrated that the four subunits are essential for its activity. Furthermore, we also showed by substrate competition experiments and the use of a specific inhibitor that the AccD5 subunit's role in the carboxylation of the long acyl-CoAs, as part of the LCC complex, was structural rather than catalytic. Moreover, AccD5 was also able to carboxylate its natural substrates, acetyl-CoA and propionyl-CoA, in the context of the LCC enzyme complex. Thus, the supercomplex formed by these four subunits has the potential to generate the main substrates, malonyl-CoA, methylmalonyl-CoA and α-carboxy-C 24-26 -CoA, used as condensing units for the biosynthesis of all the lipids present in this pathogen. © 2017 Federation of European Biochemical Societies.

Group IIA secretory phospholipase A2 (GIIA) mediates apoptotic death during NMDA receptor activation in rat primary cortical neurons.

PubMed

Chiricozzi, Elena; Fernandez-Fernandez, Seila; Nardicchi, Vincenza; Almeida, Angeles; Bolaños, Juan Pedro; Goracci, Gianfrancesco

2010-03-01

Phospholipases A(2) (PLA(2)) participate in neuronal death signalling pathways because of their ability to release lipid mediators, although the contribution of each isoform and mechanism of neurotoxicity are still elusive. Using a novel fluorogenic method to assess changes in a PLA(2) activity by flow cytometry, here we show that the group IIA secretory phospholipase A(2) isoform (GIIA) was specifically activated in cortical neurons following stimulation of N-methyl-d-aspartate glutamate receptor subtype (NMDAR). For activation, GIIA required Ca(2+) and reactive oxygen/nitrogen species, and inhibition of its activity fully prevented NMDAR-mediated neuronal apoptotic death. Superoxide, nitric oxide or peroxynitrite donors stimulated GIIA activity, which mediated neuronal death. Intriguingly, we also found that GIIA activity induced mitochondrial superoxide production after NMDAR stimulation. These results reveal a novel role for GIIA in excitotoxicity both as target and producer of superoxide in a positive-loop of activation that may contribute to the propagation of neurodegeneration.

Serine racemase is associated with schizophrenia susceptibility in humans and in a mouse model

PubMed Central

Labrie, Viviane; Fukumura, Ryutaro; Rastogi, Anjali; Fick, Laura J.; Wang, Wei; Boutros, Paul C.; Kennedy, James L.; Semeralul, Mawahib O.; Lee, Frankie H.; Baker, Glen B.; Belsham, Denise D.; Barger, Steven W.; Gondo, Yoichi; Wong, Albert H.C.; Roder, John C.

2009-01-01

Abnormal N-methyl-d-aspartate receptor (NMDAR) function has been implicated in the pathophysiology of schizophrenia. d-serine is an important NMDAR modulator, and to elucidate the role of the d-serine synthesis enzyme serine racemase (Srr) in schizophrenia, we identified and characterized mice with an ENU-induced mutation that results in a complete loss of Srr activity and dramatically reduced d-serine levels. Mutant mice displayed behaviors relevant to schizophrenia, including impairments in prepulse inhibition, sociability and spatial discrimination. Behavioral deficits were exacerbated by an NMDAR antagonist and ameliorated by d-serine or the atypical antipsychotic clozapine. Expression profiling revealed that the Srr mutation influenced several genes that have been linked to schizophrenia and cognitive ability. Transcript levels altered by the Srr mutation were also normalized by d-serine or clozapine treatment. Furthermore, analysis of SRR genetic variants in humans identified a robust association with schizophrenia. This study demonstrates that aberrant Srr function and diminished d-serine may contribute to schizophrenia pathogenesis. PMID:19483194

Mechanical stress activates NMDA receptors in the absence of agonists.

PubMed

Maneshi, Mohammad Mehdi; Maki, Bruce; Gnanasambandam, Radhakrishnan; Belin, Sophie; Popescu, Gabriela K; Sachs, Frederick; Hua, Susan Z

2017-01-03

While studying the physiological response of primary rat astrocytes to fluid shear stress in a model of traumatic brain injury (TBI), we found that shear stress induced Ca 2+ entry. The influx was inhibited by MK-801, a specific pore blocker of N-Methyl-D-aspartic acid receptor (NMDAR) channels, and this occurred in the absence of agonists. Other NMDA open channel blockers ketamine and memantine showed a similar effect. The competitive glutamate antagonists AP5 and GluN2B-selective inhibitor ifenprodil reduced NMDA-activated currents, but had no effect on the mechanically induced Ca 2+ influx. Extracellular Mg 2+ at 2 mM did not significantly affect the shear induced Ca 2+ influx, but at 10 mM it produced significant inhibition. Patch clamp experiments showed mechanical activation of NMDAR and inhibition by MK-801. The mechanical sensitivity of NMDARs may play a role in the normal physiology of fluid flow in the glymphatic system and it has obvious relevance to TBI.

Mechanical stress activates NMDA receptors in the absence of agonists

PubMed Central

Maneshi, Mohammad Mehdi; Maki, Bruce; Gnanasambandam, Radhakrishnan; Belin, Sophie; Popescu, Gabriela K.; Sachs, Frederick; Hua, Susan Z.

2017-01-01

While studying the physiological response of primary rat astrocytes to fluid shear stress in a model of traumatic brain injury (TBI), we found that shear stress induced Ca2+ entry. The influx was inhibited by MK-801, a specific pore blocker of N-Methyl-D-aspartic acid receptor (NMDAR) channels, and this occurred in the absence of agonists. Other NMDA open channel blockers ketamine and memantine showed a similar effect. The competitive glutamate antagonists AP5 and GluN2B-selective inhibitor ifenprodil reduced NMDA-activated currents, but had no effect on the mechanically induced Ca2+ influx. Extracellular Mg2+ at 2 mM did not significantly affect the shear induced Ca2+ influx, but at 10 mM it produced significant inhibition. Patch clamp experiments showed mechanical activation of NMDAR and inhibition by MK-801. The mechanical sensitivity of NMDARs may play a role in the normal physiology of fluid flow in the glymphatic system and it has obvious relevance to TBI. PMID:28045032

Agmatine reverses pain induced by inflammation, neuropathy, and spinal cord injury

PubMed Central

Fairbanks, Carolyn A.; Schreiber, Kristin L.; Brewer, Kori L.; Yu, Chen-Guang; Stone, Laura S.; Kitto, Kelley F.; Nguyen, H. Oanh; Grocholski, Brent M.; Shoeman, Don W.; Kehl, Lois J.; Regunathan, Soundararajan; Reis, Donald J.; Yezierski, Robert P.; Wilcox, George L.

2000-01-01

Antagonists of glutamate receptors of the N-methyl-d-aspartate subclass (NMDAR) or inhibitors of nitric oxide synthase (NOS) prevent nervous system plasticity. Inflammatory and neuropathic pain rely on plasticity, presenting a clinical opportunity for the use of NMDAR antagonists and NOS inhibitors in chronic pain. Agmatine (AG), an endogenous neuromodulator present in brain and spinal cord, has both NMDAR antagonist and NOS inhibitor activities. We report here that AG, exogenously administered to rodents, decreased hyperalgesia accompanying inflammation, normalized the mechanical hypersensitivity (allodynia/hyperalgesia) produced by chemical or mechanical nerve injury, and reduced autotomy-like behavior and lesion size after excitotoxic spinal cord injury. AG produced these effects in the absence of antinociceptive effects in acute pain tests. Endogenous AG also was detected in rodent lumbosacral spinal cord in concentrations similar to those previously detected in brain. The evidence suggests a unique antiplasticity and neuroprotective role for AG in processes underlying persistent pain and neuronal injury. PMID:10984543

Stereotyped initiation of retinal waves by bipolar cells via presynaptic NMDA autoreceptors

PubMed Central

Zhang, Rong-wei; Li, Xiao-quan; Kawakami, Koichi; Du, Jiu-lin

2016-01-01

Glutamatergic retinal waves, the spontaneous patterned neural activities propagating among developing retinal ganglion cells (RGCs), instruct the activity-dependent refinement of visuotopic maps. However, its initiation and underlying mechanism remain largely elusive. Here using larval zebrafish and multiple in vivo approaches, we discover that bipolar cells (BCs) are responsible for the generation of glutamatergic retinal waves. The wave originates from BC axon terminals (ATs) and propagates laterally to nearby BCs and vertically to downstream RGCs and the optic tectum. Its initiation is triggered by the activation of and consequent glutamate release from BC ATs, and is mediated by the N-methyl-D-aspartate subtype of glutamate receptors (NMDARs) expressed at these ATs. Intercellular asymmetry of NMDAR expression at BC ATs enables the preferential initiation of waves at the temporal retina, where BC ATs express more NMDARs. Thus, our findings indicate that glutamatergic retinal waves are initiated by BCs through a presynaptic NMDA autoreceptor-dependent process. PMID:27586999

Iron overload accelerates neuronal amyloid-β production and cognitive impairment in transgenic mice model of Alzheimer's disease.

PubMed

Becerril-Ortega, Javier; Bordji, Karim; Fréret, Thomas; Rush, Travis; Buisson, Alain

2014-10-01

Iron dyshomeostasis is proving increasingly likely to be involved in the pathology of Alzheimer's disease (AD); yet, its mechanism is not well understood. Here, we investigated the AD-related mechanism(s) of iron-sulfate exposure in vitro and in vivo, using cultured primary cortical neurons and APP/PS1 AD-model mice, respectively. In both systems, we observed iron-induced disruptions of amyloid precursor protein (APP) processing, neuronal signaling, and cognitive behavior. Iron overload increased production of amyloidogenic KPI-APP and amyloid beta. Further, this APP misprocessing was blocked by MK-801 in vitro, suggesting the effect was N-methyl-D-aspartate receptor (NMDAR) dependent. Calcium imaging confirmed that 24 hours iron exposure led to disrupted synaptic signaling by augmenting GluN2B-containing NMDAR expression-GluN2B messenger RNA and protein levels were increased and promoting excessing extrasynaptic NMDAR signaling. The disrupted GluN2B expression was concurrent with diminished expression of the splicing factors, sc35 and hnRNPA1. In APP/PS1 mice, chronic iron treatment led to hastened progression of cognitive impairment with the novel object recognition discrimination index, revealing a deficit at the age of 4 months, concomitant with augmented GluN2B expression. Together, these data suggest iron-induced APP misprocessing and hastened cognitive decline occur through inordinate extrasynaptic NMDAR activation. Copyright © 2014 Elsevier Inc. All rights reserved.

Phencyclidine administration during neurodevelopment alters network activity in prefrontal cortex and hippocampus in adult rats.

PubMed

Kjaerby, Celia; Hovelsø, Nanna; Dalby, Nils Ole; Sotty, Florence

2017-08-01

Symptoms of schizophrenia have been linked to insults during neurodevelopment such as NMDA receptor (NMDAR) antagonist exposure. In animal models, this leads to schizophrenia-like behavioral symptoms as well as molecular and functional changes within hippocampal and prefrontal regions. The aim of this study was to determine how administration of the NMDAR antagonist phencyclidine (PCP) during neurodevelopment affects functional network activity within the hippocampus and medial prefrontal cortex (mPFC). We recorded field potentials in vivo after electrical brain stem stimulation and observed a suppression of evoked theta power in ventral hippocampus, while evoked gamma power in mPFC was enhanced in rats administered with PCP neonatally. In addition, increased gamma synchrony elicited by acute administration of the NMDAR antagonist MK-801 was exaggerated in neonatal PCP animals. These data suggest that NMDAR antagonist exposure during brain development alters functional networks within hippocampus and mPFC possibly contributing to the reported behavioral symptoms of this animal model of schizophrenia. NEW & NOTEWORTHY We show that insults with a NMDA receptor antagonist during neurodevelopment lead to suppressed evoked theta oscillations in ventral hippocampus in adult rats, while evoked gamma oscillations are enhanced and hypersensitive to an acute challenge with a NMDA receptor antagonist in prefrontal cortex. These observations reveal the significance of neurodevelopmental disturbances in the evolvement of schizophrenia-like symptoms and contribute to the understanding of the functional deficits underlying aberrant behavior in this disease. Copyright © 2017 the American Physiological Society.

Possible Involvement of Standardized Bacopa monniera Extract (CDRI-08) in Epigenetic Regulation of reelin and Brain-Derived Neurotrophic Factor to Enhance Memory

PubMed Central

Preethi, Jayakumar; Singh, Hemant K.; Rajan, Koilmani E.

2016-01-01

Bacopa monniera extract (CDRI-08; BME) has been known to improve learning and memory, and understanding the molecular mechanisms may help to know its specificity. We investigated whether the BME treatment alters the methylation status of reelin and brain-derived neurotropic factor (BDNF) to enhance the memory through the interaction of N-methyl-D-aspartate receptor (NMDAR) with synaptic proteins. Rat pups were subjected to novel object recognition test following daily oral administration of BME (80 mg/kg) in 0.5% gum acacia (per-orally, p.o.; PND 15–29)/three doses of 5-azacytidine (5-azaC; 3.2 mg/kg) in 0.9% saline (intraperitoneally, i.p.) on PND-30. After the behavioral test, methylation status of reelin, BDNF and activation of NMDAR, and its interactions with synaptic proteins were tested. Rat pups treated with BME/5-azaC showed higher discrimination towards novel objects than with old objects during testing. Further, we observed an elevated level of unmethylated DNA in reelin and BDNF promoter region. Up-regulated reelin along with the splice variant of apolipoprotein E receptor 2 (ApoER 2, ex 19) form a cluster and activate NMDAR through disabled adopter protein-1 (DAB1) to enhance BDNF. Observed results suggest that BME regulate reelin epigenetically, which might enhance NMDAR interactions with synaptic proteins and induction of BDNF. These changes may be linked with improved novel object recognition memory. PMID:27445807

Perturbing NR2B-PSD-95 interaction relieves neuropathic pain by inactivating CaMKII-CREB signaling.

PubMed

Xu, Fangxia; Zhao, Xin; Liu, Lin; Song, Jia; Zhu, Yingjun; Chu, Shuaishuai; Shao, Xueming; Li, Xiuxiu; Ma, Zhengliang; Gu, Xiaoping

2017-09-06

Neuropathic pain is characterized by central sensitization. The interaction between N-methyl-D-aspartate receptors (NMDARs) and postsynaptic density protein-95 (PSD-95) plays a major role in central sensitization. Here, we aimed to investigate the analgesic effect of disruption of the interaction between NMDAR and PSD-95. Chronic dorsal root ganglia compression model rats were used to mimic sciatica. Thermal hyperalgesia and mechanical allodynia were evaluated. The expression of spinal phospho-NR2B, PSD-95, calcium/calmodulin-dependent protein kinase II (CaMKII), and cAMP response element binding protein (CREB) was measured using western blotting. A mimetic peptide Myr-NR2B9c was injected intrathecally to disrupt the interaction between PSD-95 and NR2B and detected by coimmunoprecipitation. Chronic dorsal root ganglia compression surgery induced thermal hyperalgesia and mechanical allodynia, and upregulated pain-related proteins such as phospho-NR2B, PSD-95, CaMKII, and CREB expressions in the spinal cord. Myr-NR2B9c disrupted the interaction between NR2B-containing NMDARs and PSD-95 in the spinal cord. Intrathecal administration of Myr-NR2B9c attenuated neuropathic pain behaviors and downregulated the expressions of phospho-NR2B, PSD-95, CaMKII, and CREB in the spinal cord. The present study indicates that dissociation of NR2B-containing NMDARs from PSD-95 inactivates CaMKII and CREB signaling and relieves pain.

PSD-93 deletion inhibits Fyn-mediated phosphorylation of NR2B and protects against focal cerebral ischemia.

PubMed

Zhang, Meijuan; Li, Qingjie; Chen, Ling; Li, Jie; Zhang, Xin; Chen, Xiang; Zhang, Qingxiu; Shao, Yuan; Xu, Yun

2014-08-01

Modification of N-methyl-d-aspartate receptor (NMDAR)-mediated excitotoxicity appears to be a potential target in the treatment of ischemic stroke. Postsynaptic density protein-93 (PSD-93) specifically binds the C-terminal tails of the NMDAR, which is critical to couple NMDAR activity to specific intracellular signaling. This study is to investigate whether PSD-93 disruption displays neuroprotection in a focal ischemic stroke model of adult mice and, if it does, to explore possible mechanisms. It was found that, following middle cerebral artery occlusion (MCAO), PSD-93 knockout (KO) mice manifested significant reductions in infarcted volume, neurological deficits and number of degenerated neurons. PSD-93 deletion also reduced cultured cortical neuronal death caused by glucose and oxygen deprivation (OGD). Ischemic long term potentiation (i-LTP) could not be induced in the PSD-93 KO group and wild type (WT) groups pretreated with either AP-5 (NMDAR inhibitor) or PP2 (Src family inhibitor). PSD-93 KO decreased the phosphorylation of the NR2B at Tyr1472 and the interaction between NR2B and Fyn after MCAO. Together, our study demonstrated that PSD-93 KO confers profound neuroprotection against ischemic brain injury, which probably links to the inhibitory effect on Fyn-mediated phosphorylation of NR2B caused by PSD-93 deletion. These findings may provide a novel avenue for the treatment of ischemic stroke. Copyright © 2014 Elsevier Inc. All rights reserved.

Serine racemase is expressed in islets and contributes to the regulation of glucose homeostasis.

PubMed

Lockridge, Amber D; Baumann, Daniel C; Akhaphong, Brian; Abrenica, Alleah; Miller, Robert F; Alejandro, Emilyn U

2016-11-01

NMDA receptors (NMDARs) have recently been discovered as functional regulators of pancreatic β-cell insulin secretion. While these excitatory receptor channels have been extensively studied in the brain for their role in synaptic plasticity and development, little is known about how they work in β-cells. In neuronal cells, NMDAR activation requires the simultaneous binding of glutamate and a rate-limiting co-agonist, such as D-serine. D-serine levels and availability in most of the brain rely on endogenous synthesis by the enzyme serine racemase (Srr). Srr transcripts have been reported in human and mouse islets but it is not clear whether Srr is functionally expressed in β-cells or what its role in the pancreas might be. In this investigation, we reveal that Srr protein is highly expressed in primary human and mouse β-cells. Mice with whole body deletion of Srr (Srr KO) show improved glucose tolerance through enhanced insulin secretory capacity, possibly through Srr-mediated alterations in islet NMDAR expression and function. We observed elevated insulin sensitivity in some animals, suggesting Srr metabolic regulation in other peripheral organs as well. Srr expression in neonatal and embryonic islets, and adult deficits in Srr KO pancreas weight and islet insulin content, point toward a potential role for Srr in pancreatic development. These data reveal the first evidence that Srr may regulate glucose homeostasis in peripheral tissues and provide circumstantial evidence that D-serine may be an endogenous islet NMDAR co-agonist in β-cells.

Cystathionine-β-synthase-derived hydrogen sulfide is required for amygdalar long-term potentiation and cued fear memory in rats.

PubMed

Chen, Hai-Bo; Wu, Wen-Ning; Wang, Wei; Gu, Xun-Hu; Yu, Bin; Wei, Bo; Yang, Yuan-Jian

2017-04-01

Hydrogen sulfide (H 2 S) is an endogenous gaseous molecule that functions as a neuromodulator in the brain. We previously reported that H 2 S regulated amygdalar synaptic plasticity and cued fear memory in rats. However, whether endogenous H 2 S is required for amygdalar long-term potentiation (LTP) induction and cued fear memory formation remains unclear. Here, we show that cystathionine-β-synthase (CBS), the predominant H 2 S-producing enzyme in the brain, was highly expressed in the amygdala of rats. Suppressing CBS activity by inhibitor prevented activity-triggered generation of H 2 S in the lateral amygdala (LA) region. Incubating brain slices with CBS inhibitor significantly prevented the induction of NMDA receptors (NMDARs)-dependent LTP in the thalamo-LA pathway, and intra-LA infusion of CBS inhibitor impaired cued fear memory in rats. Notably, treatment with H 2 S donor, but not CBS activator, significantly reversed the impairments of LTP and fear memory caused by CBS inhibition. Mechanismly, inhibition of CBS activity led to a reduction in NMDAR-mediated synaptic response in the thalamo-LA pathway, and treatment with H 2 S donor restored the function of NMDARs. Collectively, these results indicate that CBS-derived H 2 S is required for amygdalar synaptic plasticity and cued fear memory in rats, and the effects of endogenous H 2 S might involve the regulation of NMDAR function. Copyright © 2017 Elsevier Inc. All rights reserved.

Vitamin B6 prevents isocarbophos-induced vascular dementia in rats through N-methyl-D-aspartate receptor signaling.

PubMed

Li, Peng; Zhu, Mo-Li; Pan, Guo-Pin; Lu, Jun-Xiu; Zhao, Fan-Rong; Jian, Xu; Liu, Li-Ying; Wan, Guang-Rui; Chen, Yuan; Ping, Song; Wang, Shuang-Xi; Hu, Chang-Ping

2018-01-01

We have previously reported that the long-term exposure of organophosphorus induces vascular dementia (VD) in rats. As a coenzyme, vitamin B6 is mainly involved in the regulation of metabolisms. Whether vitamin B6 improves VD remains unknown. The model of VD was induced by feeding rats with isocarbophos (0.5 mg/kg per two day, 12 weeks). The blood flow of the posterior cerebral artery (PCA) in rat was assessed by transcranial Doppler (TCD). The learning and memory were evaluated by the Morris Water Maze (MWM) test. Administration of vitamin B6 increased the blood flow in the right and left posterior cerebral arteries and improved the functions of learning and memory in isocarbophos-treated rats. Vitamin B6 increased the protein levels of N-methyl-D-aspartate receptor (NMDAR) 2B, postsynaptic densities (PSDs) protein 95, and calmodulin-dependent protein kinase II (CaMK-II) in the hippocampus, which were decreased by isocarbophos in rats. Morphological analysis by light microscope and electronic microscope indicated disruptions of the hippocampus caused by isocarbophos were normalized by vitamin B6. Importantly, the antagonist of NMDAR signaling by eliprodil abolished these beneficial effects produced by vitamin B6 on PCA blood flow, learning, memory, and hippocampus structure in rats, as well as the protein expression of NMDAR 2B, PSDs protein 95, and CaMK-II in the hippocampus. Vitamin B6 activates NMDAR signaling to prevent isocarbophos-induced VD in rats.

N‐methyl‐D‐aspartate receptor antibody production from germinal center reactions: Therapeutic implications

PubMed Central

Makuch, Mateusz; Wilson, Robert; Al‐Diwani, Adam; Varley, James; Kienzler, Anne‐Kathrin; Taylor, Jennifer; Berretta, Antonio; Fowler, Darren; Lennox, Belinda; Leite, M. Isabel; Waters, Patrick

2018-01-01

Introduction N‐methyl‐D‐aspartate receptor (NMDAR) antibody encephalitis is mediated by immunoglobulin G (IgG) autoantibodies directed against the NR1 subunit of the NMDAR. Around 20% of patients have an underlying ovarian teratoma, and the condition responds to early immunotherapies and ovarian teratoma removal. However, despite clear therapeutic relevance, mechanisms of NR1‐IgG production and the contribution of germinal center B cells to NR1‐IgG levels are unknown. Methods Clinical data and longitudinal paired serum NR1‐reactive IgM and IgG levels from 10 patients with NMDAR‐antibody encephalitis were determined. Peripheral blood mononuclear cells from these 10 patients, and two available ovarian teratomas, were stimulated with combinations of immune factors and tested for secretion of total IgG and NR1‐specific antibodies. Results In addition to disease‐defining NR1‐IgG, serum NR1‐IgM was found in 6 of 10 patients. NR1‐IgM levels were typically highest around disease onset and detected for several months into the disease course. Moreover, circulating patient B cells were differentiated into CD19+CD27++CD38++ antibody‐secreting cells in vitro and, from 90% of patients, secreted NR1‐IgM and NR1‐IgG. Secreted levels of NR1‐IgG correlated with serum NR1‐IgG (p < 0.0001), and this was observed across the varying disease durations, suggestive of an ongoing process. Furthermore, ovarian teratoma tissue contained infiltrating lymphocytes which produced NR1‐IgG in culture. Interpretation Serum NR1‐IgM and NR1‐IgG, alongside the consistent production of NR1‐IgG from circulating B cells and from ovarian teratomas suggest that ongoing germinal center reactions may account for the peripheral cell populations which secrete NR1‐IgG. Cells participating in germinal center reactions might be a therapeutic target for the treatment of NMDAR‐antibody encephalitis. Ann Neurol 2018;83:553–561 PMID:29406578

Subunit Compositions of the RNA-Silencing Enzymes Pol IV and Pol V Reveal Their Origins as Specialized Forms of RNA Polymerase II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ream, Thomas S.; Haag, J. R.; Wierzbicki, A. T.

2009-01-30

In addition to RNA polymerases I, II, and III, the essential RNA polymerases present in all eukaryotes, plants have two additional nuclear RNA polymerases, abbreviated as Pol IV and Pol V, that play nonredundant roles in siRNA-directed DNA methylation and gene silencing. We show that Arabidopsis Pol IV and Pol V are composed of subunits that are paralogous or identical to the 12 subunits of Pol II. Four subunits of Pol IV are distinct from their Pol II paralogs, six subunits of Pol V are distinct from their Pol II paralogs, and four subunits differ between Pol IV and Polmore » V. Importantly, the subunit differences occur in key positions relative to the template entry and RNA exit paths. Our findings support the hypothesis that Pol IV and Pol V are Pol II-like enzymes that evolved specialized roles in the production of noncoding transcripts for RNA silencing and genome defense.« less

Activation-induced Modification in the CD3 Complex of the γδ T Cell Receptor

PubMed Central

Hayes, Sandra M.; Laky, Karen; El-Khoury, Dalal; Kappes, Dietmar J.; Fowlkes, B.J.; Love, Paul E.

2002-01-01

The T cell antigen receptor complexes expressed on αβ and γδ T cells differ not only in their respective clonotypic heterodimers but also in the subunit composition of their CD3 complexes. The γδ T cell receptors (TCRs) expressed on ex vivo γδ T cells lack CD3δ, whereas αβ TCRs contain CD3δ. While this result correlates with the phenotype of CD3δ−/− mice, in which γδ T cell development is unaffected, it is inconsistent with the results of previous studies reporting that CD3δ is a component of the γδ TCR. Since earlier studies examined the subunit composition of γδ TCRs expressed on activated and expanded peripheral γδ T cells or γδ TCR+ intestinal intraepithelial lymphocytes, we hypothesized that activation and expansion may lead to changes in the CD3 subunit composition of the γδ TCR. Here, we report that activation and expansion do in fact result in the inclusion of a protein, comparable in mass and mobility to CD3δ, in the γδ TCR. Further analyses revealed that this protein is not CD3δ, but instead is a differentially glycosylated form of CD3γ. These results provide further evidence for a major difference in the subunit composition of αβ- and γδ TCR complexes and raise the possibility that modification of CD3γ may have important functional consequences in activated γδ T cells. PMID:12438426

The ribosomal subunit assembly line

PubMed Central

Dlakić, Mensur

2005-01-01

Recent proteomic studies in Saccharomyces cerevisiae have identified nearly 200 proteins, other than the structural ribosomal proteins, that participate in the assembly of ribosomal subunits and their transport from the nucleus. In a separate line of research, proteomic studies of mature plant ribosomes have revealed considerable variability in the protein composition of individual ribosomes. PMID:16207363

Two sides of the same coin: TFIIH complexes in transcription and DNA repair.

PubMed

Zhovmer, Alexander; Oksenych, Valentyn; Coin, Frédéric

2010-04-13

TFIIH is organized into a seven-subunit core associated with a three-subunit Cdk-activating kinase (CAK) module. TFIIH has roles in both transcription initiation and DNA repair. During the last 15 years, several studies have been conducted to identify the composition of the TFIIH complex involved in DNA repair. Recently, a new technique combining chromatin immunoprecipitation and western blotting resolved the hidden nature of the TFIIH complex participating in DNA repair. Following the recruitment of TFIIH to the damaged site, the CAK module is released from the core TFIIH, and the core subsequently associates with DNA repair factors. The release of the CAK is specifically driven by the recruitment of the DNA repair factor XPA and is required to promote the incision/excision of the damaged DNA. Once the DNA lesions have been repaired, the CAK module returns to the core TFIIH on the chromatin, together with the release of the repair factors. These data highlight the dynamic composition of a fundamental cellular factor that adapts its subunit composition to the cell needs.

Subunit mass fingerprinting of mitochondrial complex I.

PubMed

Morgner, Nina; Zickermann, Volker; Kerscher, Stefan; Wittig, Ilka; Abdrakhmanova, Albina; Barth, Hans-Dieter; Brutschy, Bernhard; Brandt, Ulrich

2008-10-01

We have employed laser induced liquid bead ion desorption (LILBID) mass spectrometry to determine the total mass and to study the subunit composition of respiratory chain complex I from Yarrowia lipolytica. Using 5-10 pmol of purified complex I, we could assign all 40 known subunits of this membrane bound multiprotein complex to peaks in LILBID subunit fingerprint spectra by comparing predicted protein masses to observed ion masses. Notably, even the highly hydrophobic subunits encoded by the mitochondrial genome were easily detectable. Moreover, the LILBID approach allowed us to spot and correct several errors in the genome-derived protein sequences of complex I subunits. Typically, the masses of the individual subunits as determined by LILBID mass spectrometry were within 100 Da of the predicted values. For the first time, we demonstrate that LILBID spectrometry can be successfully applied to a complex I band eluted from a blue-native polyacrylamide gel, making small amounts of large multiprotein complexes accessible for subunit mass fingerprint analysis even if they are membrane bound. Thus, the LILBID subunit mass fingerprint method will be of great value for efficient proteomic analysis of complex I and its assembly intermediates, as well as of other water soluble and membrane bound multiprotein complexes.

Subunit arrangement in P2X receptors.

PubMed

Jiang, Lin-Hua; Kim, Miran; Spelta, Valeria; Bo, Xuenong; Surprenant, Annmarie; North, R Alan

2003-10-01

ATP-gated ionotropic receptors (P2X receptors) are distributed widely in the nervous system. For example, a hetero-oligomeric receptor containing both P2X2 and P2X3 subunits is involved in primary afferent sensation. Each subunit has two membrane-spanning domains. We have used disulfide bond formation between engineered cysteines to demonstrate close proximity between the outer ends of the first transmembrane domain of one subunit and the second transmembrane domain of another. After expression in HEK 293 cells of such modified P2X2 or P2X4 subunits, the disulfide bond formation is evident because an ATP-evoked channel opening requires previous reduction with dithiothreitol. In the hetero-oligomeric P2X2/3 receptor the coexpression of doubly substituted subunits with wild-type partners allows us to deduce that the hetero-oligomeric channel contains adjacent P2X3 subunits but does not contain adjacent P2X2 subunits. The results suggest a "head-to-tail" subunit arrangement in the quaternary structure of P2X receptors and show that a trimeric P2X2/3 receptor would have the composition P2X2(P2X3)2.

Proteasome activity and their subunit composition in endometrial cancer tissue: correlations with clinical morphological parameters.

PubMed

Spirina, L V; Kondakova, I V; Koval', V D; Kolomiets, L A; Chernyshova, A L; Choinzonov, E L; Sharova, N P

2012-08-01

The development of endometrial cancer is related to the status of the intracellular proteasome system. Total proteasome activity and pools 26S and 20S activities are higher in tumor tissue than in intact endometrium, and their composition is different. The expression of α1α2α3α5α6α7 is lower in endometrial cancer tissue in comparison with intact endometrium and the content of immune subunits LMP7, LMP2, and PA28β is increased. Total proteasome activity depends on the disease stage.

A PK-PD Model of Ketamine-Induced High-Frequency Oscillations

PubMed Central

Flores, Francisco J.; Ching, ShiNung; Hartnack, Katharine; Fath, Amanda B.; Purdon, Patrick L.; Wilson, Matthew A.; Brown, Emery N.

2017-01-01

Objective Ketamine is a widely used drug with clinical and research applications, and also known to be used as a recreational drug. Ketamine produces conspicuous changes in the electrocorticographic (ECoG) signals observed both in humans and rodents. In rodents, the intracranial ECoG displays a High-Frequency Oscillation (HFO) which power is modulated non-linearly by ketamine dose. Despite the widespread use of ketamine there is no model description of the relationship between the pharmacokinetic-pharmacodynamics (PK-PD) of ketamine and the observed HFO power. Approach In the present study, we developed a PK-PD model based on estimated ketamine concentration, its known pharmacological actions, and observed ECoG effects. The main pharmacological action of ketamine is antagonism of the NMDA receptor (NMDAR), which in rodents is accompanied by a high-frequency oscillation (HFO) observed in the ECoG. At high doses, however, ketamine also acts at non-NMDAR sites, produces loss of consciousness, and the transient disappearance of the HFO. We propose a two-compartment PK model that represents the concentration of ketamine, and a PD model based in opposing effects of the NMDAR and non-NMDAR actions on the HFO power. Main results We recorded ECoG from the cortex of rats after two doses of ketamine, and extracted the HFO power from the ECoG spectrograms. We fit the PK-PD model to the time course of the HFO power, and showed that the model reproduces the dose-dependent profile of the HFO power. The model provides good fits even in the presence of high variability in HFO power across animals. As expected, the model does not provide good fits to the HFO power after dosing the pure NMDAR antagonist MK-801. Significance Our study provides a simple model to relate the observed electrophysiological effects of ketamine to its actions at the molecular level at different concentrations. This will improve the study of ketamine and rodent models of schizophrenia to better understand the wide and divergent range of effects that ketamine has. PMID:26268223

Pregnanolone Glutamate, a Novel Use-Dependent NMDA Receptor Inhibitor, Exerts Antidepressant-Like Properties in Animal Models.

PubMed

Holubova, Kristina; Nekovarova, Tereza; Pistovcakova, Jana; Sulcova, Alexandra; Stuchlík, Ales; Vales, Karel

2014-01-01

A number of studies demonstrated a rapid onset of an antidepressant effect of non-competitive N-methyl-d-aspartic acid receptor (NMDAR) antagonists. Nonetheless, its therapeutic potential is rather limited, due to a high coincidence of negative side-effects. Therefore, the challenge seems to be in the development of NMDAR antagonists displaying antidepressant properties, and at the same time maintaining regular physiological function of the NMDAR. Previous results demonstrated that naturally occurring neurosteroid 3α5β-pregnanolone sulfate shows pronounced inhibitory action by a use-dependent mechanism on the tonically active NMDAR. The aim of the present experiments is to find out whether the treatment with pregnanolone 3αC derivatives affects behavioral response to chronic and acute stress in an animal model of depression. Adult male mice were used throughout the study. Repeated social defeat and forced swimming tests were used as animal models of depression. The effect of the drugs on the locomotor/exploratory activity in the open-field test was also tested together with an effect on anxiety in the elevated plus maze. Results showed that pregnanolone glutamate (PG) did not induce hyperlocomotion, whereas both dizocilpine and ketamine significantly increased spontaneous locomotor activity in the open field. In the elevated plus maze, PG displayed anxiolytic-like properties. In forced swimming, PG prolonged time to the first floating. Acute treatment of PG disinhibited suppressed locomotor activity in the repeatedly defeated group-housed mice. Aggressive behavior of isolated mice was reduced after the chronic 30-day administration of PG. PG showed antidepressant-like and anxiolytic-like properties in the used tests, with minimal side-effects. Since PG combines GABAA receptor potentiation and use-dependent NMDAR inhibition, synthetic derivatives of neuroactive steroids present a promising strategy for the treatment of mood disorders. -3α5β-pregnanolone glutamate (PG) is a use-dependent antagonist of NMDA receptors.-We demonstrated that PG did not induce significant hyperlocomotion.-We showed that PG displayed anxiolytic-like and antidepressant-like properties.

Stressor-induced NMDAR dysfunction as a unifying hypothesis for the aetiology, pathogenesis and comorbidity of clinical depression.

PubMed

Marsden, W N

2011-10-01

Typically the monoamine system has been the central focus of neurobiological research into depression and represents the major target of modern antidepressant medications; although the extent to which monoamines such as serotonin play a role in the pathogenesis of depression is still not clear. Recent research advancements have expanded the neurotransmitter-level focus of mood disorders to incorporate intracellular pathways and regional brain circuitry. As such the importance of other systems has emerged including those related to neuroplastic signal transduction and gene transcription cascades within cortico-limbic circuits. Indeed mounting evidence suggests interaction with these pathways is required for the chronic therapeutic effect of current clinical antidepressants. Dysfunction of the glutamatergic system has also emerged as a major pathological feature in depression, and glutamatergic agents have demonstrated rapid and robust antidepressant activity in humans. In particular, the glutamate receptors (AMPAR, NMDAR & mGluR) are intrinsically connected to neuronal efficiency and inefficiency cascades, so their dysfunction may account for alterations to multiple signal transduction pathways in depression. This article presents concepts supporting a NMDA hypothesis of depression, whereby the pathogenesis of depression may arise from stressors inducing excessive NMDAR activity which acts heterogeneously at both cellular and regional levels to disrupt normal neurobiological function and induce the depressive phenotype. In this hypothesis multiple psychological and environmental stressors are united in their capacity to potentiate excessive tonic and phasic NMDAR activation on neurons and glia. Such NMDAR dysfunction may lead to: disruption of glia processes and tripartite signalling; potentiation of extrasynaptic inefficiency/LTD pathways in some regions (e.g. prefrontal cortex & hippocampus); potentiation of synaptic efficiency/LTP pathways in other regions (e.g. amygdala); and regional disruption of cortico-limbic circuits and dopaminergic reward pathways (e.g. nucleus accumbens). This model unites depression with a variety of stressors including glucocorticoids, inflammation, oxidative stress, magnesium deficiency, hyperhomocysteinemia, and bio-energetic dysfunction; and also helps explain comorbidity with other neurological and affective disorders. In particular, a neurometabolic contribution to the aetiology of depressive as well as other neurological and affective disorders is explored. Copyright © 2011 Elsevier Ltd. All rights reserved.

MK-801-induced locomotor activity in long-sleep x short-sleep recombinant inbred mouse strains: correlational analysis with low-dose ethanol and provisional quantitative trait loci.

PubMed

Zahniser, N R; Negri, C A; Hanania, T; Gehle, V M

1999-11-01

Low doses of the N-methyl-D-aspartate receptor (NMDAR) antagonist MK-801 (dizocilpine) or ethanol increase locomotor activity to a lesser extent in long-sleep (LS), than in short-sleep (SS), mice. LS mice also have fewer brain [3H]MK-801 binding sites than SS mice. In this study, LSXSS recombinant inbred (RI) mice were used to investigate whether different NMDAR densities contribute to differential MK-801 activation and whether common genes are involved in initial sensitivity to MK-801-and ethanol-induced activation. Locomotor activity was measured for 90 min after saline or MK-801 injection. Quantitative autoradiographic analysis of [3H]MK-801 binding was used to measure densities of NMDARs in seven brain regions. The ethanol (1-2 g/kg) activation scores from Erwin and colleagues (1997) were used for correlational analysis, as was their method for quantitative trait loci (QTL) analysis. Both saline and MK-801 (0.3 mg/kg, given intraperitoneally) induced a continuum of locomotor responses across the LSXSS RI strains. There was a 4-fold range of MK-801 difference scores (MK-801 score-saline baseline), with the RI 9 and RI 4 strains representing low and high responders, respectively. Dose-response experiments with these two strains confirmed that 0.3 mg/kg MK-801 produced significant activation, similar to previous results with LS and SS mice. However, unlike previous LS/SS results, lower densities of NMDARs were not observed in the RI 9 than in the RI 4 mouse brains. No significant genetic correlations were observed between MK-801-induced and ethanol-induced responses in the LSXSS RI mice. Two provisional MK-801 activation QTLs were identified (p < 0.01) on chromosomes 11 and 19, neither in common with those mapped for ethanol activation. Different densities of brain NMDARs are unlikely to account for the differential activation of LSXSS RI mice by MK-801. Additionally, in the RI mice either separate sets of genes regulate low dose MK-801- and ethanol-induced locomotor responses or the overlapping subset of genes controlling these two behaviors is small (< or =10%).

A definition of the domains Archaea, Bacteria and Eucarya in terms of small subunit ribosomal RNA characteristics

NASA Technical Reports Server (NTRS)

Winker, S.; Woese, C. R.

1991-01-01

The number of small subunit rRNA sequences is now great enough that the three domains Archaea, Bacteria and Eucarya (Woese et al., 1990) can be reliably defined in terms of their sequence "signatures". Approximately 50 homologous positions (or nucleotide pairs) in the small subunit rRNA characterize and distinguish among the three. In addition, the three can be recognized by a variety of nonhomologous rRNA characters, either individual positions and/or higher-order structural features. The Crenarchaeota and the Euryarchaeota, the two archaeal kingdoms, can also be defined and distinguished by their characteristic compositions at approximately fifteen positions in the small subunit rRNA molecule.

Analysis of the interaction mode between hyperthermophilic archaeal group II chaperonin and prefoldin using a platform of chaperonin oligomers of various subunit arrangements.

PubMed

Sahlan, Muhamad; Kanzaki, Taro; Zako, Tamotsu; Maeda, Mizuo; Yohda, Masafumi

2010-09-01

Prefoldin is a co-chaperone that captures an unfolded protein substrate and transfers it to the group II chaperonin for completion of protein folding. Group II chaperonin of a hyperthermophilic archaeon, Thermococcus strain KS-1, interacts and cooperates with archaeal prefoldins. Although the interaction sites within chaperonin and prefoldin have been analyzed, the binding mode between jellyfish-like hexameric prefoldin and the double octameric ring group II chaperonin remains unclear. As prefoldin binds the chaperonin beta subunit more strongly than the alpha subunit, we analyzed the binding mode between prefoldin and chaperonin in the context of Thermococcus group II chaperonin complexes of various subunit compositions and arrangements. The oligomers exhibited various affinities for prefoldins according to the number and order of subunits. Binding affinity increased with the number of Cpnbeta subunits. Interestingly, chaperonin complexes containing two beta subunits adjacently exhibited stronger affinities than other chaperonin complexes containing the same number of beta subunits. The result suggests that all four beta tentacles of prefoldin interact with the helical protrusions of CPN in the PFD-CPN complex as the previously proposed model that two adjacent PFD beta subunits seem to interact with two CPN adjacent subunits. Copyright © 2010 Elsevier B.V. All rights reserved.

Genetic analysis of neuronal ionotropic glutamate receptor subunits

PubMed Central

Granger, Adam J; Gray, John A; Lu, Wei; Nicoll, Roger A

2011-01-01

Abstract In the brain, fast, excitatory synaptic transmission occurs primarily through AMPA- and NMDA-type ionotropic glutamate receptors. These receptors are composed of subunit proteins that determine their biophysical properties and trafficking behaviour. Therefore, determining the function of these subunits and receptor subunit composition is essential for understanding the physiological properties of synaptic transmission. Here, we discuss and evaluate various genetic approaches that have been used to study AMPA and NMDA receptor subunits. These approaches have demonstrated that the GluA1 AMPA receptor subunit is required for activity-dependent trafficking and contributes to basal synaptic transmission, while the GluA2 subunit regulates Ca2+ permeability, homeostasis and trafficking to the synapse under basal conditions. In contrast, the GluN2A and GluN2B NMDA receptor subunits regulate synaptic AMPA receptor content, both during synaptic development and plasticity. Ongoing research in this field is focusing on the molecular interactions and mechanisms that control these functions. To accomplish this, molecular replacement techniques are being used, where native subunits are replaced with receptors containing targeted mutations. In this review, we discuss a single-cell molecular replacement approach which should arguably advance our physiological understanding of ionotropic glutamate receptor subunits, but is generally applicable to study of any neuronal protein. PMID:21768264

Genetic analysis of neuronal ionotropic glutamate receptor subunits.

PubMed

Granger, Adam J; Gray, John A; Lu, Wei; Nicoll, Roger A

2011-09-01

In the brain, fast, excitatory synaptic transmission occurs primarily through AMPA- and NMDA-type ionotropic glutamate receptors. These receptors are composed of subunit proteins that determine their biophysical properties and trafficking behaviour. Therefore, determining the function of these subunits and receptor subunit composition is essential for understanding the physiological properties of synaptic transmission. Here, we discuss and evaluate various genetic approaches that have been used to study AMPA and NMDA receptor subunits. These approaches have demonstrated that the GluA1 AMPA receptor subunit is required for activity-dependent trafficking and contributes to basal synaptic transmission, while the GluA2 subunit regulates Ca(2+) permeability, homeostasis and trafficking to the synapse under basal conditions. In contrast, the GluN2A and GluN2B NMDA receptor subunits regulate synaptic AMPA receptor content, both during synaptic development and plasticity. Ongoing research in this field is focusing on the molecular interactions and mechanisms that control these functions. To accomplish this, molecular replacement techniques are being used, where native subunits are replaced with receptors containing targeted mutations. In this review, we discuss a single-cell molecular replacement approach which should arguably advance our physiological understanding of ionotropic glutamate receptor subunits, but is generally applicable to study of any neuronal protein.

Cytoplasmic Dynein Regulation by Subunit Heterogeneity and Its Role in Apical Transport

PubMed Central

Tai, Andrew W.; Chuang, Jen-Zen; Sung, Ching-Hwa

2001-01-01

Despite the existence of multiple subunit isoforms for the microtubule motor cytoplasmic dynein, it has not yet been directly shown that dynein complexes with different compositions exhibit different properties. The 14-kD dynein light chain Tctex-1, but not its homologue RP3, binds directly to rhodopsin's cytoplasmic COOH-terminal tail, which encodes an apical targeting determinant in polarized epithelial Madin-Darby canine kidney (MDCK) cells. We demonstrate that Tctex-1 and RP3 compete for binding to dynein intermediate chain and that overexpressed RP3 displaces endogenous Tctex-1 from dynein complexes in MDCK cells. Furthermore, replacement of Tctex-1 by RP3 selectively disrupts the translocation of rhodopsin to the MDCK apical surface. These results directly show that cytoplasmic dynein function can be regulated by its subunit composition and that cytoplasmic dynein is essential for at least one mode of apical transport in polarized epithelia. PMID:11425878

Assembly and mechanism of a group II ECF transporter.

PubMed

Karpowich, Nathan K; Wang, Da-Neng

2013-02-12

Energy-coupling factor (ECF) transporters are a recently discovered family of primary active transporters for micronutrients and vitamins, such as biotin, thiamine, and riboflavin. Found exclusively in archaea and bacteria, including the human pathogens Listeria, Streptococcus, and Staphylococcus, ECF transporters may be the only means of vitamin acquisition in these organisms. The subunit composition of ECF transporters is similar to that of ATP binding cassette (ABC) importers, whereby both systems share two homologous ATPase subunits (A and A'), a high affinity substrate-binding subunit (S), and a transmembrane coupling subunit (T). However, the S subunit of ECF transporters is an integral membrane protein, and the transmembrane coupling subunits do not share an obvious sequence homology between the two transporter families. Moreover, the subunit stoichiometry of ECF transporters is controversial, and the detailed molecular interactions between subunits and the conformational changes during substrate translocation are unknown. We have characterized the ECF transporters from Thermotoga maritima and Streptococcus thermophilus. Our data suggests a subunit stoichiometry of 2S:2T:1A:1A' and that S subunits for different substrates can be incorporated into the same transporter complex simultaneously. In the first crystal structure of the A-A' heterodimer, each subunit contains a novel motif called the Q-helix that plays a key role in subunit coupling with the T subunits. Taken together, these findings suggest a mechanism for coupling ATP binding and hydrolysis to transmembrane transport by ECF transporters.

Distinct Roles of NMDAR and mGluR5 in Light Exposure Reversal of Feedforward Synaptic Strength in V1 of Juvenile Mice after Binocular Vision Deprivation.

PubMed

Tie, Xiaoxiu; Li, Shuo; Feng, Yilin; Lai, Biqin; Liu, Sheng; Jiang, Bin

2018-06-01

In the visual cortex, sensory deprivation causes global augmentation of the amplitude of AMPA receptor-mediated miniature EPSCs in layer 2/3 pyramidal cells and enhancement of NMDA receptor-dependent long-term potentiation (LTP) in cells activated in layer 4, effects that are both rapidly reversed by light exposure. Layer 2/3 pyramidal cells receive both feedforward input from layer 4 and intra-cortical lateral input from the same layer, LTP is mainly induced by the former input. Whether feedforward excitatory synaptic strength is affected by visual deprivation and light exposure, how this synaptic strength correlates with the magnitude of LTP in this pathway, and the underlying mechanism have not been explored. Here, we showed that in juvenile mice, both dark rearing and dark exposure reduced the feedforward excitatory synaptic strength, and the effects can be reversed completely by 10-12 h and 6-8 h light exposure, respectively. However, inhibition of NMDA receptors by CPP or mGluR5 by MPEP, prevented the effect of light exposure on the mice reared in the dark from birth, while only inhibition of NMDAR prevented the effect of light exposure on dark-exposed mice. These results suggested that the activation of both NMDAR and mGluR5 are essential in the light exposure reversal of feedforward excitatory synaptic strength in the dark reared mice from birth; while in the dark exposed mice, only activation of NMDAR is required. Copyright © 2018. Published by Elsevier Ltd.

Long term potentiation depends on release of D-serine from astrocytes

PubMed Central

Henneberger, Christian; Papouin, Thomas; Oliet, Stéphane H. R.; Rusakov, Dmitri A.

2009-01-01

Long-term potentiation (LTP) of synaptic transmission provides an experimental model for studying mechanisms of memory1. The classical form of LTP relies on N-methyl-D-aspartate receptors (NMDARs), and it has emerged that astroglia can regulate their activation through Ca2+-dependent release of the NMDAR co-agonist D-serine2-4. Release of D-serine from glia enables LTP in cultures5 and explains a correlation between glial coverage of synapses and LTP in the supraoptic nucleus4. However, Ca2+ elevations in astroglia can also release other signalling molecules, most prominently glutamate6-8, Adenosine-5′-triphosphate9, and Tumor-Necrosis-Factor-α10,11 whereas neurons themselves can synthesise and supply D-serine12,13. Furthermore, loading an astrocyte with exogenous Ca2+ buffers does not suppress LTP in hippocampal area CA114-16, and the physiological relevance of experiments in cultures or strong exogenous stimuli applied to astrocytes has been questioned17,18. The involvement of glia in LTP induction thus remains controversial. Here we show that clamping internal Ca2+ in individual CA1 astrocytes blocks LTP induction at nearby excitatory synapses by reducing the occupancy of the NMDAR co-agonist sites. This LTP blockade can be reversed by exogenous D-serine or glycine whereas depletion of D-serine or disruption of exocytosis in an individual astrocyte blocks local LTP. We thus demonstrate that Ca2+-dependent release of D-serine from an astrocyte controls NMDAR-dependent plasticity in many thousands of excitatory synapses occurring nearby. PMID:20075918

Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc.

PubMed

Anderson, Charles T; Radford, Robert J; Zastrow, Melissa L; Zhang, Daniel Y; Apfel, Ulf-Peter; Lippard, Stephen J; Tzounopoulos, Thanos

2015-05-19

Many excitatory synapses contain high levels of mobile zinc within glutamatergic vesicles. Although synaptic zinc and glutamate are coreleased, it is controversial whether zinc diffuses away from the release site or whether it remains bound to presynaptic membranes or proteins after its release. To study zinc transmission and quantify zinc levels, we required a high-affinity rapid zinc chelator as well as an extracellular ratiometric fluorescent zinc sensor. We demonstrate that tricine, considered a preferred chelator for studying the role of synaptic zinc, is unable to efficiently prevent zinc from binding low-nanomolar zinc-binding sites, such as the high-affinity zinc-binding site found in NMDA receptors (NMDARs). Here, we used ZX1, which has a 1 nM zinc dissociation constant and second-order rate constant for binding zinc that is 200-fold higher than those for tricine and CaEDTA. We find that synaptic zinc is phasically released during action potentials. In response to short trains of presynaptic stimulation, synaptic zinc diffuses beyond the synaptic cleft where it inhibits extrasynaptic NMDARs. During higher rates of presynaptic stimulation, released glutamate activates additional extrasynaptic NMDARs that are not reached by synaptically released zinc, but which are inhibited by ambient, tonic levels of nonsynaptic zinc. By performing a ratiometric evaluation of extracellular zinc levels in the dorsal cochlear nucleus, we determined the tonic zinc levels to be low nanomolar. These results demonstrate a physiological role for endogenous synaptic as well as tonic zinc in inhibiting extrasynaptic NMDARs and thereby fine tuning neuronal excitability and signaling.

GRIN1 mutation associated with intellectual disability alters NMDA receptor trafficking and function.

PubMed

Chen, Wenjuan; Shieh, Christine; Swanger, Sharon A; Tankovic, Anel; Au, Margaret; McGuire, Marianne; Tagliati, Michele; Graham, John M; Madan-Khetarpal, Suneeta; Traynelis, Stephen F; Yuan, Hongjie; Pierson, Tyler Mark

2017-06-01

N-methyl-d-aspartate receptors (NMDARs) play important roles in brain development and neurological disease. We report two individuals with similar dominant de novo GRIN1 mutations (c.1858 G>A and c.1858 G>C; both p.G620R). Both individuals presented at birth with developmental delay and hypotonia associated with behavioral abnormalities and stereotypical movements. Recombinant NMDARs containing the mutant GluN1-G620R together with either GluN2A or GluN2B were evaluated for changes in their trafficking to the plasma membrane and their electrophysiological properties. GluN1-G620R/GluN2A complexes showed a mild reduction in trafficking, a ~2-fold decrease in glutamate and glycine potency, a strong decrease in sensitivity to Mg 2+ block, and a significant reduction of current responses to a maximal effective concentration of agonists. GluN1-G620R/GluN2B complexes showed significantly reduced delivery of protein to the cell surface associated with similarly altered electrophysiology. These results indicate these individuals may have suffered neurodevelopmental deficits as a result of the decreased presence of GluN1-G620R/GluN2B complexes on the neuronal surface during embryonic brain development and reduced current responses of GluN1-G620R-containing NMDARs after birth. These cases emphasize the importance of comprehensive functional characterization of de novo mutations and illustrates how a combination of several distinct features of NMDAR expression, trafficking and function can be present and influence phenotype.

Monosodium glutamate intake affect the function of the kidney through NMDA receptor.

PubMed

Mahieu, Stella; Klug, Maximiliano; Millen, Néstor; Fabro, Ana; Benmelej, Adriana; Contini, Maria Del Carmen

2016-03-15

We investigated whether the chronic intake of monosodium glutamate (MSG) with food affects kidney function, and renal response to glycine. We also established if the NMDA receptors are involved in the changes observed. Male Wistar rats (5weeks old) were fed a diet supplemented with MSG (3g/kg b.w./day), five days a week, and spontaneous ingestion of a 1% MSG solution during 16weeks. NaCl rats were fed a diet with NaCl (1g/kg b.w./day) and 0.35% NaCl solution at the same frequency and time. Control group was fed with normal chow and tap water. We utilized clearance techniques to examine glomerular filtration rate (GFR) and cortical renal plasma flow (CRPF) response to glycine and glycine+MK-801 (antagonist NMDA-R), and we determined NMDA-R1 in kidney by immunohistochemistry. The addition of MSG in the diet of rats increased both GFR and CRPF with an increase of absolute sodium reabsorption. However, hyperfiltration was accompanied with a normal response to glycine infusion. Immunostain of kidney demonstrate that the NMDA receptor is upregulated in rats fed with MSG diet. NMDA-R antagonist MK-801 significantly reduced both the GFR and CRPF; however the percentage of reduction was significantly higher in the group MSG. MK-801 also reduces fractional excretion of water, sodium and potassium in the three groups. Renal NMDAR may be conditioned by the addition of MSG in the diet, favoring the hyperfiltration and simultaneously Na retention in the body. Copyright © 2016 Elsevier Inc. All rights reserved.

JIP1-Mediated JNK Activation Negatively Regulates Synaptic Plasticity and Spatial Memory.

PubMed

Morel, Caroline; Sherrin, Tessi; Kennedy, Norman J; Forest, Kelly H; Avcioglu Barutcu, Seda; Robles, Michael; Carpenter-Hyland, Ezekiel; Alfulaij, Naghum; Standen, Claire L; Nichols, Robert A; Benveniste, Morris; Davis, Roger J; Todorovic, Cedomir

2018-04-11

The c-Jun N-terminal kinase (JNK) signal transduction pathway is implicated in learning and memory. Here, we examined the role of JNK activation mediated by the JNK-interacting protein 1 (JIP1) scaffold protein. We compared male wild-type mice with a mouse model harboring a point mutation in the Jip1 gene that selectively blocks JIP1-mediated JNK activation. These male mutant mice exhibited increased NMDAR currents, increased NMDAR-mediated gene expression, and a lower threshold for induction of hippocampal long-term potentiation. The JIP1 mutant mice also displayed improved hippocampus-dependent spatial memory and enhanced associative fear conditioning. These results were confirmed using a second JIP1 mutant mouse model that suppresses JNK activity. Together, these observations establish that JIP1-mediated JNK activation contributes to the regulation of hippocampus-dependent, NMDAR-mediated synaptic plasticity and learning. SIGNIFICANCE STATEMENT The results of this study demonstrate that c-Jun N-terminal kinase (JNK) activation induced by the JNK-interacting protein 1 (JIP1) scaffold protein negatively regulates the threshold for induction of long-term synaptic plasticity through the NMDA-type glutamate receptor. This change in plasticity threshold influences learning. Indeed, mice with defects in JIP1-mediated JNK activation display enhanced memory in hippocampus-dependent tasks, such as contextual fear conditioning and Morris water maze, indicating that JIP1-JNK constrains spatial memory. This study identifies JIP1-mediated JNK activation as a novel molecular pathway that negatively regulates NMDAR-dependent synaptic plasticity and memory. Copyright © 2018 the authors 0270-6474/18/383708-21$15.00/0.

Serine racemase deletion disrupts memory for order and alters cortical dendritic morphology

PubMed Central

DeVito, Loren M.; Balu, Darrick T.; Kanter, Benjamin R.; Lykken, Christine; Basu, Alo C.; Coyle, Joseph T.; Eichenbaum, Howard

2012-01-01

There is substantial evidence implicating N-methyl-d-aspartate receptors (NMDARs) in memory and cognition. It has also been suggested that NMDAR hypofunction might underlie the cognitive deficits observed in schizophrenia since morphological changes, including alterations in the dendritic architecture of pyramidal neurons in the prefrontal cortex (PFC), have been reported in the schizophrenic brain post mortem. Here, we used a genetic model of NMDAR hypofunction, a serine racemase knockout (SR−/−) mouse in which the first coding exon of the mouse serine racemase gene has been deleted, to explore the role of d-serine in regulating cognitive functions as well as dendritic architecture. SR −/− mice exhibited a significantly disrupted representation of the order of events in distinct experiences as revealed by object recognition and odor sequence tests; however, SR −/− animals were unimpaired in the detection of novel objects and in spatial displacement, and showed intact relational memory in a test of transitive inference. In addition, SR −/− mice exhibited normal sociability and preference for social novelty. Neurons in the medial PFC of SR−/− mice displayed reductions in the complexity, total length, and spine density of apical dendrites. These findings demonstrate that d-serine is important for specific aspects of cognition, as well as in regulating dendritic morphology of pyramidal neurons in the mPFC. Moreover, they suggest that NMDAR hypofunction might, in part, be responsible for the cognitive deficits and synaptic changes associated with schizophrenia, and highlight this signaling pathway as a potential target for therapeutic intervention. PMID:21029376

Death of Neurons following Injury Requires Conductive Neuronal Gap Junction Channels but Not a Specific Connexin

PubMed Central

Fontes, Joseph D.; Ramsey, Jon; Polk, Jeremy M; Koop, Andre; Denisova, Janna V.; Belousov, Andrei B.

2015-01-01

Pharmacological blockade or genetic knockout of neuronal connexin 36 (Cx36)-containing gap junctions reduces neuronal death caused by ischemia, traumatic brain injury and NMDA receptor (NMDAR)-mediated excitotoxicity. However, whether Cx36 gap junctions contribute to neuronal death via channel-dependent or channel-independent mechanism remains an open question. To address this, we manipulated connexin protein expression via lentiviral transduction of mouse neuronal cortical cultures and analyzed neuronal death twenty-four hours following administration of NMDA (a model of NMDAR excitotoxicity) or oxygen-glucose deprivation (a model of ischemic injury). In cultures prepared from wild-type mice, over-expression and knockdown of Cx36-containing gap junctions augmented and prevented, respectively, neuronal death from NMDAR-mediated excitotoxicity and ischemia. In cultures obtained form from Cx36 knockout mice, re-expression of functional gap junction channels, containing either neuronal Cx36 or non-neuronal Cx43 or Cx31, resulted in increased neuronal death following insult. In contrast, the expression of communication-deficient gap junctions (containing mutated connexins) did not have this effect. Finally, the absence of ethidium bromide uptake in non-transduced wild-type neurons two hours following NMDAR excitotoxicity or ischemia suggested the absence of active endogenous hemichannels in those neurons. Taken together, these results suggest a role for neuronal gap junctions in cell death via a connexin type-independent mechanism that likely relies on channel activities of gap junctional complexes among neurons. A possible contribution of gap junction channel-permeable death signals in neuronal death is discussed. PMID:26017008

Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc

PubMed Central

Anderson, Charles T.; Radford, Robert J.; Zastrow, Melissa L.; Zhang, Daniel Y.; Apfel, Ulf-Peter; Lippard, Stephen J.; Tzounopoulos, Thanos

2015-01-01

Many excitatory synapses contain high levels of mobile zinc within glutamatergic vesicles. Although synaptic zinc and glutamate are coreleased, it is controversial whether zinc diffuses away from the release site or whether it remains bound to presynaptic membranes or proteins after its release. To study zinc transmission and quantify zinc levels, we required a high-affinity rapid zinc chelator as well as an extracellular ratiometric fluorescent zinc sensor. We demonstrate that tricine, considered a preferred chelator for studying the role of synaptic zinc, is unable to efficiently prevent zinc from binding low-nanomolar zinc-binding sites, such as the high-affinity zinc-binding site found in NMDA receptors (NMDARs). Here, we used ZX1, which has a 1 nM zinc dissociation constant and second-order rate constant for binding zinc that is 200-fold higher than those for tricine and CaEDTA. We find that synaptic zinc is phasically released during action potentials. In response to short trains of presynaptic stimulation, synaptic zinc diffuses beyond the synaptic cleft where it inhibits extrasynaptic NMDARs. During higher rates of presynaptic stimulation, released glutamate activates additional extrasynaptic NMDARs that are not reached by synaptically released zinc, but which are inhibited by ambient, tonic levels of nonsynaptic zinc. By performing a ratiometric evaluation of extracellular zinc levels in the dorsal cochlear nucleus, we determined the tonic zinc levels to be low nanomolar. These results demonstrate a physiological role for endogenous synaptic as well as tonic zinc in inhibiting extrasynaptic NMDARs and thereby fine tuning neuronal excitability and signaling. PMID:25947151

Enhanced Nitric Oxide Production during Lead (Pb2+) Exposure Recovers Protein Expression but not Presynaptic Localization of Synaptic Proteins in Developing Hippocampal Neurons

PubMed Central

Neal, April P.; Stansfield, Kirstie H.; Guilarte, Tomás R.

2012-01-01

We have previously reported that lead (Pb2+) exposure results in both presynaptic and postsynaptic changes in developing neurons as a result of inhibition of the N-methyl-D-aspartate receptor (NMDAR). NMDAR inhibition by Pb2+ during synaptogenesis disrupts downstream trans-synaptic signaling of brain-derived neurotrophic factor (BDNF) and exogenous addition of BDNF can recover the effects of Pb2+ on both presynaptic protein expression and presynaptic vesicular release. NMDAR activity can modulate other trans-synaptic signaling pathways, such as nitric oxide (NO) signaling. Thus, it is possible that other trans-synaptic pathways in addition to BDNF signaling may be disrupted by Pb2+ exposure. The current study investigated whether exogenous addition of NO could recover the presynaptic vesicular proteins lost as a result of Pb2+ exposure during synaptogenesis, namely Synaptophysin (Syn) and Synaptobrevin (Syb). We observed that exogenous addition of NO during Pb2+ exposure results in complete recovery of whole-cell Syn levels and partial recovery of Syn and Syb synaptic targeting in Pb2+-exposed neurons. PMID:22265330

NMDA receptor hypofunction in the dentate gyrus and impaired context discrimination in adult Fmr1 knockout mice.

PubMed

Eadie, Brennan D; Cushman, Jesse; Kannangara, Timal S; Fanselow, Michael S; Christie, Brian R

2012-02-01

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability in humans. This X-linked disorder is caused by the transcriptional repression of a single gene, Fmr1. The loss of Fmr1 transcription prevents the production of Fragile X mental retardation protein (FMRP) which in turn disrupts the expression of a variety of key synaptic proteins that appear to be important for intellectual ability. A clear link between synaptic dysfunction and behavioral impairment has been elusive, despite the fact that several animal models of FXS have been generated. Here we report that Fmr1 knockout mice exhibit impaired bidirectional synaptic plasticity in the dentate gyrus (DG) of the hippocampus. These deficits are associated with a novel decrease in functional NMDARs (N-methyl-D-aspartate receptors). In addition, mice lacking the Fmr1 gene show impaired performance in a context discrimination task that normally requires functional NMDARs in the DG. These data indicate that Fmr1 deletion results in significant NMDAR-dependent electrophysiological and behavioral impairments specific to the DG. Copyright © 2010 Wiley Periodicals, Inc.

Autism-like Deficits in Shank3-Deficient Mice Are Rescued by Targeting Actin Regulators.

PubMed

Duffney, Lara J; Zhong, Ping; Wei, Jing; Matas, Emmanuel; Cheng, Jia; Qin, Luye; Ma, Kaijie; Dietz, David M; Kajiwara, Yuji; Buxbaum, Joseph D; Yan, Zhen

2015-06-09

Haploinsufficiency of the Shank3 gene, which encodes a scaffolding protein at glutamatergic synapses, is a highly prevalent and penetrant risk factor for autism. Using combined behavioral, electrophysiological, biochemical, imaging, and molecular approaches, we find that Shank3-deficient mice exhibit autism-like social deficits and repetitive behaviors, as well as the significantly diminished NMDA receptor (NMDAR) synaptic function and synaptic distribution in prefrontal cortex. Concomitantly, Shank3-deficient mice have a marked loss of cortical actin filaments, which is associated with the reduced Rac1/PAK activity and increased activity of cofilin, the major actin depolymerizing factor. The social deficits and NMDAR hypofunction are rescued by inhibiting cofilin or activating Rac1 in Shank3-deficient mice and are induced by inhibiting PAK or Rac1 in wild-type mice. These results indicate that the aberrant regulation of synaptic actin filaments and loss of synaptic NMDARs contribute to the manifestation of autism-like phenotypes. Thus, targeting actin regulators provides a strategy for autism treatment. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

LTP-triggered cholesterol redistribution activates Cdc42 and drives AMPA receptor synaptic delivery

PubMed Central

Brachet, Anna; Norwood, Stephanie; Brouwers, Jos F.; Palomer, Ernest; Helms, J. Bernd

2015-01-01

Neurotransmitter receptor trafficking during synaptic plasticity requires the concerted action of multiple signaling pathways and the protein transport machinery. However, little is known about the contribution of lipid metabolism during these processes. In this paper, we addressed the question of the role of cholesterol in synaptic changes during long-term potentiation (LTP). We found that N-methyl-d-aspartate–type glutamate receptor (NMDAR) activation during LTP induction leads to a rapid and sustained loss or redistribution of intracellular cholesterol in the neuron. A reduction in cholesterol, in turn, leads to the activation of Cdc42 and the mobilization of GluA1-containing α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid–type glutamate receptors (AMPARs) from Rab11-recycling endosomes into the synaptic membrane, leading to synaptic potentiation. This process is accompanied by an increase of NMDAR function and an enhancement of LTP. These results imply that cholesterol acts as a sensor of NMDAR activation and as a trigger of downstream signaling to engage small GTPase (guanosine triphosphatase) activation and AMPAR synaptic delivery during LTP. PMID:25753037

Mechanisms for localising calcineurin and CaMKII in dendritic spines.

PubMed

Penny, Christopher J; Gold, Matthew G

2018-05-27

Calcineurin and calmodulin-dependent protein kinase II (CaMKII) are both highly abundant in neurons, and both are activated by calmodulin at similar Ca 2+ concentrations in the test tube. However, they fulfill opposite functions in dendritic spines, with CaMKII activity driving long-term synaptic potentiation following large influxes of Ca 2+ through NMDA-type glutamate receptors (NMDARs), and calcineurin responding to smaller influxes of Ca 2+ through the same receptors to induce long-term depression. In this review, we explore the notion that precise dynamic localisation of the two enzymes at different sites within dendritic spines is fundamental to this behavior. We describe the structural basis of calcineurin and CaMKII localisation by their interaction with proteins including AKAP79, densin-180, α-actinin, and NMDARs. We then consider how interactions with these proteins likely position calcineurin and CaMKII at different distances from Ca 2+ microdomains emanating from the mouths of NMDARs in order to drive the divergent responses. We also highlight shortcomings in our current understanding of synaptic localisation of these two important signalling enzymes. Copyright © 2017. Published by Elsevier Inc.

N-Methyl-d-Aspartate (NMDA) Receptor Blockade Prevents Neuronal Death Induced by Zika Virus Infection

PubMed Central

Costa, Vivian V.; Del Sarto, Juliana L.; Rocha, Rebeca F.; Silva, Flavia R.; Doria, Juliana G.; Olmo, Isabella G.; Marques, Rafael E.; Queiroz-Junior, Celso M.; Foureaux, Giselle; Araújo, Julia Maria S.; Cramer, Allysson; Real, Ana Luíza C. V.; Ribeiro, Lucas S.; Sardi, Silvia I.; Ferreira, Anderson J.; Machado, Fabiana S.; de Oliveira, Antônio C.; Teixeira, Antônio L.; Nakaya, Helder I.; Souza, Danielle G.

2017-01-01

ABSTRACT Zika virus (ZIKV) infection is a global health emergency that causes significant neurodegeneration. Neurodegenerative processes may be exacerbated by N-methyl-d-aspartate receptor (NMDAR)-dependent neuronal excitoxicity. Here, we have exploited the hypothesis that ZIKV-induced neurodegeneration can be rescued by blocking NMDA overstimulation with memantine. Our results show that ZIKV actively replicates in primary neurons and that virus replication is directly associated with massive neuronal cell death. Interestingly, treatment with memantine or other NMDAR blockers, including dizocilpine (MK-801), agmatine sulfate, or ifenprodil, prevents neuronal death without interfering with the ability of ZIKV to replicate in these cells. Moreover, in vivo experiments demonstrate that therapeutic memantine treatment prevents the increase of intraocular pressure (IOP) induced by infection and massively reduces neurodegeneration and microgliosis in the brain of infected mice. Our results indicate that the blockade of NMDARs by memantine provides potent neuroprotective effects against ZIKV-induced neuronal damage, suggesting it could be a viable treatment for patients at risk for ZIKV infection-induced neurodegeneration. PMID:28442607

[Molecular cloning and characterization of cDNA of the rpc10+ gene encoding the smallest subunit of nuclear RNA polymerases of Schizosaccharomyces pombe].

PubMed

Shpakovskiĭ, G V; Lebedenko, E N

1997-05-01

The full-length cDNA of the rpc10+ gene encoding mini-subunit Rpc10, which is common for all three nuclear RNA polymerases of the fission yeast Schizosaccharomyces pombe, was cloned and sequenced. The Rpc10 subunit of Sz. pombe and its homologs from S. cerevisiae and H. sapiens are positively charged proteins with a highly conserved C-terminal region and an invariant zinc-binding domain (Zn-finger) of a typical amino acid composition: YxCx2Cx12RCx2CGxR. Functional tests of heterospecific complementation, using tetrad analysis or plasmid shuffling, showed that the Rpc10 subunit of Sz. pombe can successfully replace the homologous ABC10 alpha subunit in nuclear RNA polymerases I-III of S. cerevisiae.

Iron Oxidation and Core Formation in Recombinant Heteropolymeric Human Ferritins.

PubMed

Mehlenbacher, Matthew; Poli, Maura; Arosio, Paolo; Santambrogio, Paolo; Levi, Sonia; Chasteen, N Dennis; Bou-Abdallah, Fadi

2017-08-01

In animals, the iron storage and detoxification protein, ferritin, is composed of two functionally and genetically distinct subunit types, H (heavy) and L (light), which co-assemble in various ratios with tissue specific distributions to form shell-like protein structures of 24 subunits within which a mineralized iron core is stored. The H-subunit possesses a ferroxidase center (FC) that catalyzes Fe(II) oxidation, whereas the L-subunit does not. To assess the role of the L-subunit in iron oxidation and core formation, two human recombinant heteropolymeric ferritins, designated H-rich and L-rich with ratios of ∼20H:4L and ∼22L:2H, respectively, were employed and compared to the human homopolymeric H-subunit ferritin (HuHF). These heteropolymeric ferritins have a composition similar to the composition of those found in hearts and brains (i.e., H-rich) and in livers and spleens (i.e., L-rich). As for HuHF, iron oxidation in H-rich ferritin was found to proceed with a 2:1 Fe(II):O 2 stoichiometry at an iron level of 2 Fe(II) atoms/H-subunit with the generation of H 2 O 2 . The H 2 O 2 reacted with additional Fe(II) in a 2:1 Fe(II):H 2 O 2 ratio, thus avoiding the production of hydroxyl radical. A μ-1,2-peroxo-diFe(III) intermediate was observed at the FC of H-rich ferritin as for HuHF. Importantly, the H-rich protein regenerated full ferroxidase activity more rapidly than HuHF did and additionally formed larger iron cores, indicating dual roles for the L-subunit in facilitating iron turnover at the FC and in mineralization of the core. The L-rich ferritin, while also facilitating iron oxidation at the FC, additionally promoted oxidation at the mineral surface once the iron binding capacity of the FC was exceeded.

Soybean glycinin subunits: Characterization of physicochemical and adhesion properties.

PubMed

Mo, Xiaoqun; Zhong, Zhikai; Wang, Donghai; Sun, Xiuzhi

2006-10-04

Soybean proteins have shown great potential for applications as renewable and environmentally friendly adhesives. The objective of this work was to study physicochemical and adhesion properties of soy glycinin subunits. Soybean glycinin was extracted from soybean flour and then fractionated into acidic and basic subunits with an estimated purity of 90 and 85%, respectively. Amino acid composition of glycinin subunits was determined. The high hydrophobic amino acid content is a major contributor to the solubility behavior and water resistance of the basic subunits. Acidic subunits and glycinin had similar solubility profiles, showing more than 80% solubility at pH 2.0-4.0 or 6.5-12.0, whereas basic subunits had considerably lower solubility with the minimum at pH 4.5-8.0. Thermal analysis using a differential scanning calorimeter suggested that basic subunits form new oligomeric structures with higher thermal stability than glycinin but no highly ordered structures present in isolated acidic subunits. The wet strength of basic subunits was 160% more than that of acidic subunits prepared at their respective isoelectric points (pI) and cured at 130 degrees C. Both pH and the curing temperature significantly affected adhesive performance. High-adhesion water resistance was usually observed for adhesives from protein prepared at their pI values and cured at elevated temperatures. Basic subunits are responsible for the water resistance of glycinin and are a good starting material for the development of water-resistant adhesives.

The F0F1-ATP Synthase Complex Contains Novel Subunits and Is Essential for Procyclic Trypanosoma brucei

PubMed Central

Zíková, Alena; Schnaufer, Achim; Dalley, Rachel A.; Panigrahi, Aswini K.; Stuart, Kenneth D.

2009-01-01

The mitochondrial F0F1 ATP synthase is an essential multi-subunit protein complex in the vast majority of eukaryotes but little is known about its composition and role in Trypanosoma brucei, an early diverged eukaryotic pathogen. We purified the F0F1 ATP synthase by a combination of affinity purification, immunoprecipitation and blue-native gel electrophoresis and characterized its composition and function. We identified 22 proteins of which five are related to F1 subunits, three to F0 subunits, and 14 which have no obvious homology to proteins outside the kinetoplastids. RNAi silencing of expression of the F1 α subunit or either of the two novel proteins showed that they are each essential for the viability of procyclic (insect stage) cells and are important for the structural integrity of the F0F1-ATP synthase complex. We also observed a dramatic decrease in ATP production by oxidative phosphorylation after silencing expression of each of these proteins while substrate phosphorylation was not severely affected. Our procyclic T. brucei cells were sensitive to the ATP synthase inhibitor oligomycin even in the presence of glucose contrary to earlier reports. Hence, the two novel proteins appear essential for the structural organization of the functional complex and regulation of mitochondrial energy generation in these organisms is more complicated than previously thought. PMID:19436713

Heteromeric Slick/Slack K+ channels show graded sensitivity to cell volume changes

PubMed Central

Hashem, Nadia; Calloe, Kirstine; Klaerke, Dan A.

2017-01-01

Slick and Slack high-conductance K+ channels are found in the CNS, kidneys, pancreas, among other organs, where they play an important role in cell excitability as well as in ion transport processes. They are both activated by Na+ and Cl- but show a differential regulation by cell volume changes. Slick has been shown to be regulated by cell volume changes, whereas Slack is insensitive. α-subunits of these channels form homomeric as well as heteromeric channels. It is the aim of this work to explore whether the subunit composition of the Slick/Slack heteromeric channel affects the response to osmotic challenges. In order to provide with the adequate water permeability to the cell membrane of Xenopus laevis oocytes, mRNA of aquaporin 1 was co-expressed with homomeric or heteromeric Slick and Slack α-subunits. Oocytes were superfused with hypotonic or hypertonic buffers and changes in currents were measured by two-electrode voltage clamp. This work presents the first heteromeric K+ channel with a characteristic graded sensitivity to small and fast changes in cell volume. Our results show that the cell volume sensitivity of Slick/Slack heteromeric channels is dependent on the number of volume sensitive Slick α-subunits in the tetrameric channels, giving rise to graded cell volume sensitivity. Regulation of the subunit composition of a channel may constitute a novel mechanism to determine volume sensitivity of cells. PMID:28222129

Heteromeric Slick/Slack K+ channels show graded sensitivity to cell volume changes.

PubMed

Tejada, Maria A; Hashem, Nadia; Calloe, Kirstine; Klaerke, Dan A

2017-01-01

Slick and Slack high-conductance K+ channels are found in the CNS, kidneys, pancreas, among other organs, where they play an important role in cell excitability as well as in ion transport processes. They are both activated by Na+ and Cl- but show a differential regulation by cell volume changes. Slick has been shown to be regulated by cell volume changes, whereas Slack is insensitive. α-subunits of these channels form homomeric as well as heteromeric channels. It is the aim of this work to explore whether the subunit composition of the Slick/Slack heteromeric channel affects the response to osmotic challenges. In order to provide with the adequate water permeability to the cell membrane of Xenopus laevis oocytes, mRNA of aquaporin 1 was co-expressed with homomeric or heteromeric Slick and Slack α-subunits. Oocytes were superfused with hypotonic or hypertonic buffers and changes in currents were measured by two-electrode voltage clamp. This work presents the first heteromeric K+ channel with a characteristic graded sensitivity to small and fast changes in cell volume. Our results show that the cell volume sensitivity of Slick/Slack heteromeric channels is dependent on the number of volume sensitive Slick α-subunits in the tetrameric channels, giving rise to graded cell volume sensitivity. Regulation of the subunit composition of a channel may constitute a novel mechanism to determine volume sensitivity of cells.

The composition and function of the striatin-interacting phosphatases and kinases (STRIPAK) complex in fungi.

PubMed

Kück, Ulrich; Beier, Anna M; Teichert, Ines

2016-05-01

The striatin-interacting phosphatases and kinases (STRIPAK) complex is a highly conserved eukaryotic protein complex that was recently described for diverse animal and fungal species. Here, we summarize our current knowledge about the composition and function of the STRIPAK complex from the ascomycete Sordaria macrospora, which we discovered by investigating sexually sterile mutants (pro), having a defect in fruiting body development. Mass spectrometry and yeast two-hybrid analysis defined core subunits of the STRIPAK complex, which have structural homologs in animal and other fungal organisms. These subunits (and their mammalian homologs) are PRO11 (striatin), PRO22 (STRIP1/2), SmMOB3 (Mob3), PRO45 (SLMAP), and PP2AA, the structural, and PP2Ac, the catalytic subunits of protein phosphatase 2A (PP2A). Beside fruiting body formation, the STRIPAK complex controls vegetative growth and hyphal fusion in S. macrospora. Although the contribution of single subunits to diverse cellular and developmental processes is not yet fully understood, functional analysis has already shown that mammalian homologs are able to substitute the function of distinct fungal STRIPAK subunits. This underscores the view that fungal model organisms serve as useful tools to get a molecular insight into cellular and developmental processes of eukaryotes in general. Future work will unravel the precise localization of single subunits within the cell and decipher their STRIPAK-related and STRIPAK-independent functions. Finally, evidence is accumulating that there is a crosstalk between STRIPAK and various signaling pathways, suggesting that eukaryotic development is dependent on STRIPAK signaling. Copyright © 2015 Elsevier Inc. All rights reserved.

The eukaryotic RNA exosome: same scaffold but variable catalytic subunits.

PubMed

Lykke-Andersen, Søren; Tomecki, Rafal; Jensen, Torben Heick; Dziembowski, Andrzej

2011-01-01

The RNA exosome is a versatile ribonucleolytic protein complex that participates in a multitude of cellular RNA processing and degradation events. It consists of an invariable nine-subunit core that associates with a variety of enzymatically active subunits and co-factors. These contribute to or even provide the catalytic activity and substrate specificity of the complex. The S. cerevisiae exosome has been intensively studied since its discovery in 1997 and thus serves as the archetype of eukaryotic exosomes. Notably, its catalytic potential, derived exclusively from associated subunits, differs between the nuclear and cytoplasmic versions of the complex. The same holds true for other eukaryotes, however, recent discoveries from various laboratories including our own have revealed that there are variations on this theme. Here, we review the latest findings concerning catalytic subunits of eukaryotic exosomes, and we discuss the apparent need for differential composition and subcellular distribution of exosome variants.

Interneuron- and GABAA receptor-specific inhibitory synaptic plasticity in cerebellar Purkinje cells

NASA Astrophysics Data System (ADS)

He, Qionger; Duguid, Ian; Clark, Beverley; Panzanelli, Patrizia; Patel, Bijal; Thomas, Philip; Fritschy, Jean-Marc; Smart, Trevor G.

2015-07-01

Inhibitory synaptic plasticity is important for shaping both neuronal excitability and network activity. Here we investigate the input and GABAA receptor subunit specificity of inhibitory synaptic plasticity by studying cerebellar interneuron-Purkinje cell (PC) synapses. Depolarizing PCs initiated a long-lasting increase in GABA-mediated synaptic currents. By stimulating individual interneurons, this plasticity was observed at somatodendritic basket cell synapses, but not at distal dendritic stellate cell synapses. Basket cell synapses predominantly express β2-subunit-containing GABAA receptors; deletion of the β2-subunit ablates this plasticity, demonstrating its reliance on GABAA receptor subunit composition. The increase in synaptic currents is dependent upon an increase in newly synthesized cell surface synaptic GABAA receptors and is abolished by preventing CaMKII phosphorylation of GABAA receptors. Our results reveal a novel GABAA receptor subunit- and input-specific form of inhibitory synaptic plasticity that regulates the temporal firing pattern of the principal output cells of the cerebellum.

Antitussive Effects of Memantine in Guinea Pigs

PubMed Central

Smith, Jaclyn A.; Hilton, Emma C. Y.; Saulsberry, Loren

2012-01-01

Background: The treatment of cough is a significant clinical unmet need because there is little evidence that current therapies are effective. Based on evidence supporting a role for N-methyl d-aspartate receptors (NMDARs) in cough, we hypothesized that memantine, a low-affinity, uncompetitive NMDAR channel blocker in routine use for the treatment of Alzheimer disease, could be an effective, well-tolerated, antitussive therapy. The aim of this study was to establish preclinical evidence that memantine has antitussive effects. Methods: We studied the influence of memantine on experimentally induced coughing in response to citric acid and bradykinin inhalation in guinea pigs. We also compared the potency and efficacy of memantine as an antitussive to other NMDAR antagonists, dextromethorphan and ketamine, and to the γ-aminobutyric acid class B receptor agonist baclofen. Results: Compared with control subjects, 10 mg/kg memantine significantly reduced the cumulative number of coughs evoked by both citric acid (median, 24.0 [interquartile range (IQR), 13.0-25.5] vs 1.5 [IQR, 0.3-10.3] coughs; P = .012) and bradykinin aerosols (median, 16.0 [IQR, 9.5-18.5] vs 0.0 [IQR, 0-0.75] coughs; P = .002). Memantine 10 mg/kg produced a similar reduction in the cumulative number of coughs to baclofen 3 mg/kg and demonstrated comparatively greater cough suppression than 30 mg/kg dextromethorphan or 30 mg/kg ketamine. This dose of memantine produced no sedative or respiratory depressive effects. Conclusions: This study illustrates that memantine has marked antitussive effects in guinea pigs, most likely mediated through NMDAR channel blockade. Memantine, therefore, has the potential to be a safe, effective, and well-tolerated antitussive agent. PMID:22016492

Neuronal surface antigen antibodies in limbic encephalitis: clinical-immunologic associations.

PubMed

Graus, F; Saiz, A; Lai, M; Bruna, J; López, F; Sabater, L; Blanco, Y; Rey, M J; Ribalta, T; Dalmau, J

2008-09-16

To report the frequency and type of antibodies against neuronal surface antigens (NSA-ab) in limbic encephalitis (LE). Analysis of clinical features, neuropathologic findings, and detection of NSA-ab using immunochemistry on rat tissue and neuronal cultures in a series of 45 patients with paraneoplastic (23) or idiopathic (22) LE. NSA-ab were identified in 29 patients (64%; 12 paraneoplastic, 17 idiopathic). Thirteen patients had voltage-gated potassium channels (VGKC)-ab, 11 novel NSA (nNSA)-ab, and 5 NMDA receptor (NMDAR)-ab. nNSA-ab did not identify a common antigen and were more frequent in paraneoplastic than idiopathic LE (39% vs 9%; p = 0.03). When compared with VGKC-ab or NMDAR-ab, the nNSA associated more frequently with intraneuronal antibodies (11% vs 73%; p = 0.001). Of 12 patients (9 nNSA-ab, 2 VGKC-ab, 1 NMDAR-ab) with paraneoplastic LE and NSA-ab, concomitant intraneuronal antibodies occurred in 9 (75%). None of these 12 patients improved with immunotherapy. The autopsy of three of them showed neuronal loss, microgliosis, and cytotoxic T cell infiltrates in the hippocampus and amygdala. These findings were compatible with a T-cell mediated neuronal damage. In contrast, 13 of 17 (76%) patients with idiopathic LE and NSA-ab (8 VGKC-ab, 4 NMDAR-ab, 1 nNSA-ab) and 1 of 5 (20%) without antibodies had clinical improvement (p = 0.04). In paraneoplastic limbic encephalitis (LE), novel antibodies against neuronal surface antigens (nNSA-ab) occur frequently, coexist with antibodies against intracellular antigens, and these cases are refractory to immunotherapy. In idiopathic LE, the likelihood of improvement is significantly higher in patients with NSA-ab than in those without antibodies.

Dissociation of thirst and sodium appetite in the furo/cap model of extracellular dehydration and a role for N-methyl-D-aspartate receptors in the sensitization of sodium appetite

PubMed Central

Hurley, Seth. W.; Johnson, Alan Kim

2015-01-01

Depletion of extracellular fluids motivates many animals to seek out and ingest water and sodium. Animals with a history of extracellular dehydration display enhanced sodium appetite and in some cases thirst. The progressive increase in sodium intake induced by repeated sodium depletions is known as sensitization of sodium appetite. Administration of the diuretic and natriuretic drug, furosemide, along with a low dose of captopril (furo/cap), elicits thirst and a rapid onset of sodium appetite. In the present studies the furo/cap model was used to explore the physiological mechanisms of sensitization of sodium appetite. However, when thirst and sodium appetite were measured concurrently in the furo/cap model, individual rats exhibited sensitization of either thirst or sodium appetite. In subsequent studies, thirst and sodium appetite were dissociated by offering either water prior to sodium or sodium before water. When water and sodium intake were dissociated in time, the furo/cap model reliably produced sensitization of sodium appetite. It is likely that neuroplasticity mediates this sensitization. Glutamatergic N-methyl-d-aspartate receptor (NMDA-R) activation is critical for the development of most forms of neuroplasticity. Therefore, we hypothesized that integrity of NMDA-R function is necessary for the sensitization of sodium appetite. Pharmacological blockade of NMDA-Rs with systemic administration of MK-801 (0.15mg/kg) prevented the sensitization of fluid intake in general when water and sodium were offered concurrently, and prevented sensitization of sodium intake specifically when water and sodium intake were dissociated. The involvement of NMDA-Rs provides support for the possibility that sensitization of sodium appetite is mediated by neuroplasticity. PMID:24341713

Role of antioxidant enzymes in redox regulation of N-methyl-D-aspartate receptor function and memory in middle-aged rats.

PubMed

Lee, Wei-Hua; Kumar, Ashok; Rani, Asha; Foster, Thomas C

2014-06-01

Overexpression of superoxide dismutase 1 (SOD1) in the hippocampus results in age-dependent impaired cognition and altered synaptic plasticity suggesting a possible model for examining the role of oxidative stress in senescent neurophysiology. However, it is unclear if SOD1 overexpression involves an altered redox environment and a decrease in N-methyl-D-aspartate receptor (NMDAR) synaptic function reported for aging animals. Viral vectors were used to express SOD1 and green fluorescent protein (SOD1 + GFP), SOD1 and catalase (SOD1 + CAT), or GFP alone in the hippocampus of middle-aged (17 months) male Fischer 344 rats. We confirm that SOD1 + GFP and SOD1 + CAT reduced lipid peroxidation indicating superoxide metabolites were primarily responsible for lipid peroxidation. SOD1 + GFP impaired learning, decreased glutathione peroxidase activity, decreased glutathione levels, decreased NMDAR-mediated synaptic responses, and impaired long-term potentiation. Co-expression of SOD1 + CAT rescued the effects of SOD1 expression on learning, redox measures, and synaptic function suggesting the effects were mediated by excess hydrogen peroxide. Application of the reducing agent dithiolthreitol to hippocampal slices increased the NMDAR-mediated component of the synaptic response in SOD1 + GFP animals relative to animals that overexpress SOD1 + CAT indicating that the effect of antioxidant enzyme expression on NMDAR function was because of a shift in the redox environment. The results suggest that overexpression of neuronal SOD1 and CAT in middle age may provide a model for examining the role of oxidative stress in senescent physiology and the progression of age-related neurodegenerative diseases. Copyright © 2014 Elsevier Inc. All rights reserved.

Clinically Relevant Concentrations of Ketamine Inhibit Osteoclast Formation In Vitro in Mouse Bone Marrow Cultures.

PubMed

Du, Erxia; McAllister, Patrick; Venna, Venugopal Reddy; Xiao, Liping

2017-04-01

Ketamine has been used safely in clinics for decades for analgesia and anesthesia. It is increasingly popular in clinical practice due to its new uses and importance for emergency procedures. It is known that ketamine is sequestered in the bone marrow and the major receptors for ketamine, noncompetitive N-methyl-d-aspartate receptors (NMDARs), are expressed in osteoclasts (OCs) and osteoblasts. However, the impact of ketamine on OCs or osteoblasts is unknown. In this study, we investigated the effects of ketamine on osteoclastogenesis and regulation of NMDARs expression in vitro. Bone marrows (BMs) or bone marrow macrophages (BMMs) were cultured in the presence of macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor kappa-B ligand (RANKL) with or without ketamine for up to 6 days. OC formation peaked at day 5. On day 5 of culture, ketamine inhibited OC formation from both BM and BMM cultures at clinically relevant concentrations (3-200 µM). Ketamine inhibited RANKL-induced expression of nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1 (NFATc1) in BMM cultures. Inhibition of ketamine on RANKL-induced osteoclastogenesis is associated with down-regulation of NMDARs. In addition, ketamine significantly inhibited the M-CSF induced migration of BMMs, inhibited cell fusion and significantly increased mature OC apoptosis. We conclude that clinically relevant concentrations of ketamine inhibit OC formation in both BM and BMM cultures in vitro through inhibiting migration and fusion process and enhancing mature OC apoptosis. It is likely that ketamine regulates osteoclastogenesis, at least in part, via its effects on NMDAR expression. J. Cell. Biochem. 118: 914-923, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

PSD-95 family MAGUKs are essential for anchoring AMPA and NMDA receptor complexes at the postsynaptic density

PubMed Central

Chen, Xiaobing; Levy, Jonathan M.; Hou, Austin; Winters, Christine; Azzam, Rita; Sousa, Alioscka A.; Leapman, Richard D.; Nicoll, Roger A.; Reese, Thomas S.

2015-01-01

The postsynaptic density (PSD)-95 family of membrane-associated guanylate kinases (MAGUKs) are major scaffolding proteins at the PSD in glutamatergic excitatory synapses, where they maintain and modulate synaptic strength. How MAGUKs underlie synaptic strength at the molecular level is still not well understood. Here, we explore the structural and functional roles of MAGUKs at hippocampal excitatory synapses by simultaneous knocking down PSD-95, PSD-93, and synapse-associated protein (SAP)102 and combining electrophysiology and transmission electron microscopic (TEM) tomography imaging to analyze the resulting changes. Acute MAGUK knockdown greatly reduces synaptic transmission mediated by α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptors (AMPARs) and N-methyl-d-aspartate receptors (NMDARs). This knockdown leads to a significant rise in the number of silent synapses, diminishes the size of PSDs without changes in pre- or postsynaptic membrane, and depletes the number of membrane-associated PSD-95–like vertical filaments and transmembrane structures, identified as AMPARs and NMDARs by EM tomography. The differential distribution of these receptor-like structures and dependence of their abundance on PSD size matches that of AMPARs and NMDARs in the hippocampal synapses. The loss of these structures following MAGUK knockdown tracks the reduction in postsynaptic AMPAR and NMDAR transmission, confirming the structural identities of these two types of receptors. These results demonstrate that MAGUKs are required for anchoring both types of glutamate receptors at the PSD and are consistent with a structural model where MAGUKs, corresponding to membrane-associated vertical filaments, are the essential structural proteins that anchor and organize both types of glutamate receptors and govern the overall molecular organization of the PSD. PMID:26604311

PSD-95 family MAGUKs are essential for anchoring AMPA and NMDA receptor complexes at the postsynaptic density.

PubMed

Chen, Xiaobing; Levy, Jonathan M; Hou, Austin; Winters, Christine; Azzam, Rita; Sousa, Alioscka A; Leapman, Richard D; Nicoll, Roger A; Reese, Thomas S

2015-12-15

The postsynaptic density (PSD)-95 family of membrane-associated guanylate kinases (MAGUKs) are major scaffolding proteins at the PSD in glutamatergic excitatory synapses, where they maintain and modulate synaptic strength. How MAGUKs underlie synaptic strength at the molecular level is still not well understood. Here, we explore the structural and functional roles of MAGUKs at hippocampal excitatory synapses by simultaneous knocking down PSD-95, PSD-93, and synapse-associated protein (SAP)102 and combining electrophysiology and transmission electron microscopic (TEM) tomography imaging to analyze the resulting changes. Acute MAGUK knockdown greatly reduces synaptic transmission mediated by α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptors (AMPARs) and N-methyl-d-aspartate receptors (NMDARs). This knockdown leads to a significant rise in the number of silent synapses, diminishes the size of PSDs without changes in pre- or postsynaptic membrane, and depletes the number of membrane-associated PSD-95-like vertical filaments and transmembrane structures, identified as AMPARs and NMDARs by EM tomography. The differential distribution of these receptor-like structures and dependence of their abundance on PSD size matches that of AMPARs and NMDARs in the hippocampal synapses. The loss of these structures following MAGUK knockdown tracks the reduction in postsynaptic AMPAR and NMDAR transmission, confirming the structural identities of these two types of receptors. These results demonstrate that MAGUKs are required for anchoring both types of glutamate receptors at the PSD and are consistent with a structural model where MAGUKs, corresponding to membrane-associated vertical filaments, are the essential structural proteins that anchor and organize both types of glutamate receptors and govern the overall molecular organization of the PSD.

Proteomic analysis of PSD-93 knockout mice following the induction of ischemic cerebral injury.

PubMed

Rong, Rong; Yang, Hui; Rong, Liangqun; Wei, Xiue; Li, Qingjie; Liu, Xiaomei; Gao, Hong; Xu, Yun; Zhang, Qingxiu

2016-03-01

Postsynaptic density protein-93 (PSD-93) is enriched in the postsynaptic density and is involved in N-methyl-d-aspartate receptor (NMDAR) triggered neurotoxicity through PSD-93/NMDAR/nNOS signaling pathway. In the present study, we found that PSD-93 deficiency reduced infarcted volume and neurological deficits induced by transient middle cerebral artery occlusion (tMCAO) in the mice. To identify novel targets of PSD-93 related neurotoxicity, we applied isobaric tags for relative and absolute quantitative (iTRAQ) labeling and combined this labeling with on-line two-dimensional LC/MS/MS technology to elucidate the changes in protein expression in PSD-93 knockout mice following tMCAO. The proteomic data set consisted of 1892 proteins. Compared to control group, differences in expression levels in ischemic group >1.5-fold and <0.66-fold were considered as differential expression. A total of 104 unique proteins with differential abundance levels were identified, among which 17 proteins were selected for further validation. Gene ontology analysis using UniProt database revealed that these differentially expressed proteins are involved in diverse function such as synaptic transmission, neuronal neurotransmitter and ion transport, modification of organelle membrane components. Moreover, network analysis revealed that the interacting proteins were involved in the transport of synaptic vesicles, the integrity of synaptic membranes and the activation of the ionotropic glutamate receptors NMDAR1 and NMDAR2B. Finally, RT-PCR and Western blot analysis showed that SynGAP, syntaxin-1A, protein kinase C β, and voltage-dependent L-type calcium channels were inhibited by ischemia-reperfusion. Identification of these proteins provides valuable clues to elucidate the mechanisms underlying the actions of PSD-93 in ischemia-reperfusion induced neurotoxicity. Copyright © 2015 Elsevier Inc. All rights reserved.

Anti–N-Methyl-D-Aspartate Receptor (NMDAR) Encephalitis in Children and Adolescents

PubMed Central

Florance, Nicole R.; Davis, Rebecca L.; Lam, Christopher; Szperka, Christina; Zhou, Lei; Ahmad, Saba; Campen, Cynthia J.; Moss, Heather; Peter, Nadja; Gleichman, Amy J.; Glaser, Carol A.; Lynch, David R.; Rosenfeld, Myrna R.; Dalmau, Josep

2010-01-01

Objective To report the clinical features of anti–N-methyl-D-aspartate receptor (NMDAR) encephalitis in patients ≤ 18 years old. Methods Information was obtained by the authors or referring physicians. Antibodies were determined by immunocytochemistry and enzyme-linked immunosorbent assay (ELISA) using HEK293 cells ectopically expressing NR1. Results Over an 8-month period, 81 patients (12 male) with anti-NMDAR encephalitis were identified. Thirty-two (40%) were ≤18 years old (youngest 23 months, median 14 years); 6 were male. The frequency of ovarian teratomas was 56% in women >18 years old, 31% in girls ≤18 years old (p = 0.05), and 9% in girls ≤14 years old ( p = 0.008). None of the male patients had tumors. Of 32 patients ≤18 years old, 87.5% presented with behavioral or personality change, sometimes associated with seizures and frequent sleep dysfunction; 9.5% with dyskinesias or dystonia; and 3% with speech reduction. On admission, 53% had severe speech deficits. Eventually, 77% developed seizures, 84% stereotyped movements, 86% autonomic instability, and 23% hypoventilation. Responses to immunotherapy were slow and variable. Overall, 74% had full or substantial recovery after immunotherapy or tumor removal. Neurological relapses occurred in 25%. At the last follow-up, full recovery occurred more frequently in patients who had a teratoma that was removed (5/8) than in those without a teratoma (4/23; p = 0.03). Interpretation Anti-NMDAR encephalitis is increasingly recognized in children, comprising 40% of all cases. Younger patients are less likely to have tumors. Behavioral and speech problems, seizures, and abnormal movements are common early symptoms. The phenotype resembles that of the adults, although dysautonomia and hypoventilation are less frequent or severe in children. PMID:19670433

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis in children and adolescents.

PubMed

Florance, Nicole R; Davis, Rebecca L; Lam, Christopher; Szperka, Christina; Zhou, Lei; Ahmad, Saba; Campen, Cynthia J; Moss, Heather; Peter, Nadja; Gleichman, Amy J; Glaser, Carol A; Lynch, David R; Rosenfeld, Myrna R; Dalmau, Josep

2009-07-01

To report the clinical features of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis in patients < or = 18 years old. Information was obtained by the authors or referring physicians. Antibodies were determined by immunocytochemistry and enzyme-linked immunosorbent assay (ELISA) using HEK293 cells ectopically expressing NR1. Over an 8-month period, 81 patients (12 male) with anti-NMDAR encephalitis were identified. Thirty-two (40%) were < or =18 years old (youngest 23 months, median 14 years); 6 were male. The frequency of ovarian teratomas was 56% in women >18 years old, 31% in girls < or =18 years old (p = 0.05), and 9% in girls < or =14 years old (p = 0.008). None of the male patients had tumors. Of 32 patients < or =18 years old, 87.5% presented with behavioral or personality change, sometimes associated with seizures and frequent sleep dysfunction; 9.5% with dyskinesias or dystonia; and 3% with speech reduction. On admission, 53% had severe speech deficits. Eventually, 77% developed seizures, 84% stereotyped movements, 86% autonomic instability, and 23% hypoventilation. Responses to immunotherapy were slow and variable. Overall, 74% had full or substantial recovery after immunotherapy or tumor removal. Neurological relapses occurred in 25%. At the last follow-up, full recovery occurred more frequently in patients who had a teratoma that was removed (5/8) than in those without a teratoma (4/23; p = 0.03). Anti-NMDAR encephalitis is increasingly recognized in children, comprising 40% of all cases. Younger patients are less likely to have tumors. Behavioral and speech problems, seizures, and abnormal movements are common early symptoms. The phenotype resembles that of the adults, although dysautonomia and hypoventilation are less frequent or severe in children. Ann Neurol 2009;66:11-18.

Neurophysiological mechanisms of cortical plasticity impairments in schizophrenia and modulation by the NMDA receptor agonist D-serine

PubMed Central

Kantrowitz, Joshua T.; Epstein, Michael L.; Beggel, Odeta; Rohrig, Stephanie; Lehrfeld, Jonathan M.; Revheim, Nadine; Lehrfeld, Nayla P.; Reep, Jacob; Parker, Emily; Silipo, Gail; Ahissar, Merav; Javitt, Daniel C.

2016-01-01

Schizophrenia is associated with deficits in cortical plasticity that affect sensory brain regions and lead to impaired cognitive performance. Here we examined underlying neural mechanisms of auditory plasticity deficits using combined behavioural and neurophysiological assessment, along with neuropharmacological manipulation targeted at the N-methyl-D-aspartate type glutamate receptor (NMDAR). Cortical plasticity was assessed in a cohort of 40 schizophrenia/schizoaffective patients relative to 42 healthy control subjects using a fixed reference tone auditory plasticity task. In a second cohort (n = 21 schizophrenia/schizoaffective patients, n = 13 healthy controls), event-related potential and event-related time–frequency measures of auditory dysfunction were assessed during administration of the NMDAR agonist d-serine. Mismatch negativity was used as a functional read-out of auditory-level function. Clinical trials registration numbers were NCT01474395/NCT02156908. Schizophrenia/schizoaffective patients showed significantly reduced auditory plasticity versus healthy controls (P = 0.001) that correlated with measures of cognitive, occupational and social dysfunction. In event-related potential/time-frequency analyses, patients showed highly significant reductions in sensory N1 that reflected underlying impairments in θ responses (P < 0.001), along with reduced θ and β-power modulation during retention and motor-preparation intervals. Repeated administration of d-serine led to intercorrelated improvements in (i) auditory plasticity (P < 0.001); (ii) θ-frequency response (P < 0.05); and (iii) mismatch negativity generation to trained versus untrained tones (P = 0.02). Schizophrenia/schizoaffective patients show highly significant deficits in auditory plasticity that contribute to cognitive, occupational and social dysfunction. d-serine studies suggest first that NMDAR dysfunction may contribute to underlying cortical plasticity deficits and, second, that repeated NMDAR agonist administration may enhance cortical plasticity in schizophrenia. PMID:27913408

Anti-N-Methyl-d-Aspartate receptor (NMDAR) encephalitis during pregnancy: Clinical analysis of reported cases.

PubMed

Shi, Yan-Chao; Chen, Xiu-Ju; Zhang, Hong-Mei; Wang, Zhen; Du, Da-Yong

2017-06-01

To analyze the clinical features of 13 pregnant patients with anti-N-Methyl-d-Aspartate receptor (NMDAR) encephalitis. Retrospective review of thirteen reported cases was conducted for anti-NMDAR encephalitis patients during pregnancy. The clinical data were collected from papers published in PubMed prior to 16 February 2016. Statistical analysis of the data was performed, which encompasses the patients' age, past medical history, onset of symptoms, concomitant with ovarian teratomas, immunotherapy, outcomes of mothers and newborns. Thirteen cases were reported in 11 articles with a median age of 23 (interquartile range, 19-27) years old. There were eight cases in which the onset periods of gestation happened in the first trimester and five cases in the second trimester. Among 13 cases, five patients had a past medical history, one concomitant with autoimmune Graves' hyperthyroidism, one with bilateral ovarian teratomas removed history, one with anti-NMDAR encephalitis five years before pregnancy and two with psychiatric symptoms. Five patients were found with ovarian teratomas. Seven patients responded to first-line immunotherapy whereas all of two patients responded to second-line immunotherapy when the first-line immunotherapy failed. Following up all the 13 patients, most experienced a substantial recovery, except one had spasticity and dystonia in one hand, and one died of a superimposed infection. Three fetuses were miscarried or aborted in total. Most newborns were healthy, except two cases (2/10) with abnormal neurologic signs. Clinical analysis of the data indicates that most patients respond to first-line immunotherapy. A second-line immunotherapy is effective when first-line immunotherapy fails. It has also been found that most mothers and newborns can have good outcomes. Copyright © 2017. Published by Elsevier B.V.

Nicotine Ameliorates NMDA Receptor Antagonist-Induced Deficits in Contextual Fear Conditioning through High Affinity Nicotinic Acetylcholine Receptors in the Hippocampus

PubMed Central

André, Jessica M.; Leach, Prescott T.; Gould, Thomas J.

2011-01-01

NMDA glutamate receptors (NMDARs) and nicotinic acetylcholine receptors (nAChRs) are both involved in learning and synaptic plasticity. Increasing evidence suggests processes mediated by these receptors may interact to modulate learning; however, little is known about the neural substrates involved in these interactive processes. The present studies investigated the effects of nicotine on MK-801 hydrogen maleate (MK-801) and DL-2-Amino-5-phosphonovaleric acid (APV) induced disruption of contextual fear conditioning in male C57BL/6J mice, using direct drug infusion and selective nAChR antagonists to define the brain regions and the nAChR subtypes involved. Mice treated with MK-801 showed a deficit in contextual fear conditioning that was ameliorated by nicotine. Direct drug infusion demonstrated that the NMDAR antagonists disrupted hippocampal function and that nicotine acted in the dorsal hippocampus to ameliorate the deficit in learning. The high-affinity nAChR antagonist Dihydro-β-erythroidine hydrobromide (DhβE) blocked the effects of nicotine on MK-801-induced deficits while the α7 nAChR antagonist methyllycaconitine citrate salt hydrate (MLA) did not. These results suggest that NMDARs and nAChRs may mediate similar hippocampal processes involved in contextual fear conditioning. Furthermore, these results may have implications for developing effective therapeutics for the cognitive deficits associated with schizophrenia because a large subset of patients with schizophrenia exhibit cognitive deficits that may be related to NMDAR dysfunction and smoke at much higher rates than the healthy population, which may be an attempt to ameliorate cognitive deficits. PMID:21167848

Antagonism at NMDA receptors, but not β-adrenergic receptors, disrupts the reconsolidation of pavlovian conditioned approach and instrumental transfer for ethanol-associated conditioned stimuli.

PubMed

Milton, Amy L; Schramm, Moritz J W; Wawrzynski, James R; Gore, Felicity; Oikonomou-Mpegeti, Faye; Wang, Nancy Q; Samuel, Daniel; Economidou, Daina; Everitt, Barry J

2012-02-01

Reconsolidation is the process by which memories require restabilisation following destabilisation at retrieval. Since even old, well-established memories become susceptible to disruption following reactivation, treatments based upon disrupting reconsolidation could provide a novel form of therapy for neuropsychiatric disorders based upon maladaptive memories, such as drug addiction. Pavlovian cues are potent precipitators of relapse to drug-seeking behaviour and influence instrumental drug seeking through at least three psychologically and neurobiologically distinct processes: conditioned reinforcement, conditioned approach (autoshaping) and conditioned motivation (pavlovian-instrumental transfer or PIT). We have previously demonstrated that the reconsolidation of memories underlying the conditioned reinforcing properties of drug cues depends upon NMDA receptor (NMDAR)- and β-adrenergic receptor (βAR)-mediated signalling. However, it is unknown whether the drug cue memory representations underlying conditioned approach and PIT depend upon the same mechanisms. Using orally self-administered ethanol as a reinforcer in two separate experiments, we investigated whether the reconsolidation of the memories underlying conditioned approach and PIT requires βAR- and NMDAR-dependent neurotransmission. For ethanol self-administering but non-dependent rats, the memories underlying conditioned approach and PIT for a pavlovian drug cue were disrupted by the administration of the NMDAR antagonist MK-801, but not the administration of the βAR antagonist propranolol, when given in conjunction with memory reactivation. As for natural reinforcers, NMDARs are required for the reconsolidation of all aspects of pavlovian drug memories, but βARs are only required for the memory representation underlying conditioned reinforcement. These results indicate the potential utility of treatments based upon disrupting cue-drug memory reconsolidation in preventing relapse.

Memantine and dizocilpine interactions with antinociceptive or discriminative stimulus effects of morphine in rats after acute or chronic treatment with morphine

PubMed Central

Chen, Yukun; Evola, Marianne

2013-01-01

Rationale Memantine is a N-methyl-d-aspartic acid receptor (NMDAR) channel blocker that binds to dizocilpine sites and appears well tolerated during chronic use. Published studies suggest NMDAR antagonists prevent development of tolerance to effects of morphine by blocking NMDAR hyperactivation. Objectives We sought to compare effects of memantine to those of the more frequently studied dizocilpine and to evaluate memantine as a potential adjunct to modify tolerance to mu-opioid receptor agonists. Methods Sprague–Dawley rats were trained to discriminate morphine (3.2 mg/kg) and saline under fixed ratio 15 schedules of food delivery. Potency and maximal stimulus or rate-altering effects of cumulative doses of morphine were examined 30 min after pretreatment with dizocilpine (0.032–0.1 mg/kg) or memantine (5–10 mg/kg) and after chronic treatment with combinations of dizocilpine or memantine and morphine, 10 mg/kg twice daily, for 6 to 14 days. Effects of dizocilpine or memantine on morphine antinociception were examined in a 55 °C water tail-withdrawal assay with drug treatments parallel to those in discrimination studies. Results Acutely, memantine attenuated while dizocilpine potentiated the stimulus and antinociceptive effects of morphine. Neither chronic dizocilpine nor memantine blocked tolerance to the stimulus effects of morphine. In contrast, combined-treatment with dizocilpine (0.1 mg/kg) blocked tolerance to antinociceptive effects of lower (0.1∼3.2 mg/kg) but not higher doses of morphine, whereas memantine did not block tolerance. Conclusions Memantine and dizocilpine interacted differently with morphine, possibly due to different NMDAR binding profiles. The lack of memantine-induced changes in morphine tolerance suggests memantine may not be a useful adjunct in chronic pain management. PMID:22864944

Nandrolone-induced aggressive behavior is associated with alterations in extracellular glutamate homeostasis in mice.

PubMed

Kalinine, Eduardo; Zimmer, Eduardo Rigon; Zenki, Kamila Cagliari; Kalinine, Iouri; Kazlauckas, Vanessa; Haas, Clarissa Branco; Hansel, Gisele; Zimmer, Aline Rigon; Souza, Diogo Onofre; Müller, Alexandre Pastoris; Portela, Luis Valmor

2014-07-01

Nandrolone decanoate (ND), an anabolic androgenic steroid (AAS), induces an aggressive phenotype by mechanisms involving glutamate-induced N-methyl-d-aspartate receptor (NMDAr) hyperexcitability. The astrocytic glutamate transporters remove excessive glutamate surrounding the synapse. However, the impact of supraphysiological doses of ND on glutamate transporters activity remains elusive. We investigated whether ND-induced aggressive behavior is interconnected with GLT-1 activity, glutamate levels and abnormal NMDAr responses. Two-month-old untreated male mice (CF1, n=20) were tested for baseline aggressive behavior in the resident-intruder test. Another group of mice (n=188) was injected with ND (15mg/kg) or vehicle for 4, 11 and 19days (short-, mid- and long-term endpoints, respectively) and was evaluated in the resident-intruder test. Each endpoint was assessed for GLT-1 expression and glutamate uptake activity in the frontoparietal cortex and hippocampal tissues. Only the long-term ND endpoint significantly decreased the latency to first attack and increased the number of attacks, which was associated with decreased GLT-1 expression and glutamate uptake activity in both brain areas. These alterations may affect extracellular glutamate levels and receptor excitability. Resident males were assessed for hippocampal glutamate levels via microdialysis both prior to, and following, the introduction of intruders. Long-term ND mice displayed significant increases in the microdialysate glutamate levels only after exposure to intruders. A single intraperitoneal dose of the NMDAr antagonists, memantine or MK-801, shortly before the intruder test decreased aggressive behavior. In summary, long-term ND-induced aggressive behavior is associated with decreased extracellular glutamate clearance and NMDAr hyperexcitability, emphasizing the role of this receptor in mediating aggression mechanisms. Copyright © 2014 Elsevier Inc. All rights reserved.

Benzodiazepine-induced hippocampal CA1 neuron alpha-amino-3-hydroxy-5-methylisoxasole-4-propionic acid (AMPA) receptor plasticity linked to severity of withdrawal anxiety: differential role of voltage-gated calcium channels and N-methyl-D-aspartic acid receptors.

PubMed

Xiang, Kun; Tietz, Elizabeth I

2007-09-01

Withdrawal from 1-week oral administration of the benzodiazepine, flurazepam (FZP) is associated with increased alpha-amino-3-hydroxy-5-methylisoxasole-4-propionic acid (AMPA) receptor (AMPAR) miniature excitatory postsynaptic currents (mEPSCs) but reduction of N-methyl-D-aspartic acid (NMDA) receptor (NMDAR)-evoked (e)EPSCs in hippocampal CA1 neurons. A positive correlation was observed between increased AMPAR-mediated mEPSC amplitude and anxiety-like behavior in 1-day FZP-withdrawn rats. These effects were disrupted by systemic AMPAR antagonist administration (GYKI-52466, 0.5 mg/kg, intraperitoneal) at withdrawal onset, strengthening the hypothesis that CA1 neuron AMPAR-mediated hyperexcitability is a central component of a functional anatomic circuit associated with the expression of withdrawal anxiety. Abolition of AMPAR current upregulation in 2-day FZP withdrawn rats by GYKI-52466 injection also reversed the reduction in NMDAR-mediated eEPSC amplitude in CA1 neurons from the same rats, suggesting that downregulation of NMDAR function may serve a protective, negative-feedback role to prevent AMPAR-mediated neuronal overexcitation. NMDAR antagonist administration (MK-801, 0.25 mg/kg intraperitoneally) had no effect on modifying increased glutamatergic strength or on withdrawal anxiety, whereas injection of an L-type voltage-gated calcium channel antagonist, nimodipine (10 mg/kg, intraperitoneally) averted AMPAR current enhancement and anxiety-like behavior, suggesting that these manifestations may be initiated by a voltage-gated calcium channel-dependent signal transduction pathway. An evidence-based model of likely cellular mechanisms in the hippocampus contributing to benzodiazepine withdrawal anxiety was proposed implicating regulation of multiple CA1 neuron ion channels.

Acute Phencyclidine Alters Neural Oscillations Evoked by Tones in the Auditory Cortex of Rats.

PubMed

Schnakenberg Martin, Ashley M; OʼDonnell, Brian F; Millward, James B; Vohs, Jenifer L; Leishman, Emma; Bolbecker, Amanda R; Rass, Olga; Morzorati, Sandra L

2017-01-01

The onset response to a single tone as measured by electroencephalography (EEG) is diminished in power and synchrony in schizophrenia. Because neural synchrony, particularly at gamma frequencies (30-80 Hz), is hypothesized to be supported by the N-methyl-D-aspartate receptor (NMDAr) system, we tested whether phencyclidine (PCP), an NMDAr antagonist, produced similar deficits to tone stimuli in rats. Experiment 1 tested the effect of a PCP dose (1.0, 2.5, and 4.5 mg/kg) on response to single tones on intracranial EEG recorded over the auditory cortex in rats. Experiment 2 evaluated the effect of PCP after acute administration of saline or PCP (5 mg/kg), after continuous subchronic administration of saline or PCP (5 mg/kg/day), and after a week of drug cessation. In both experiments, a time-frequency analysis quantified mean power (MP) and phase locking factor (PLF) between 1 and 80 Hz. Event-related potentials (ERPs) were also measured to tones, and EEG spectral power in the absence of auditory stimuli. Acute PCP increased PLF and MP between 10 and 30 Hz, while decreasing MP and PLF between approximately 50 and 70 Hz. Acute PCP produced a dose-dependent broad-band increase in EEG power that extended into gamma range frequencies. There were no consistent effects of subchronic administration on gamma range activity. Acute PCP increased ERP amplitudes for the P16 and N70 components. Findings suggest that acute PCP-induced NMDAr hypofunction has differential effects on neural power and synchrony which vary with dose, time course of administration and EEG frequency. EEG synchrony and power appear to be sensitive translational biomarkers for disrupted NMDAr function, which may contribute to the pathophysiology of schizophrenia and other neuropsychiatric disorders. © 2017 S. Karger AG, Basel.

NMDA receptor function and NMDA receptor-dependent phosphorylation of huntingtin is altered by the endocytic protein HIP1.

PubMed

Metzler, Martina; Gan, Lu; Wong, Tak Pan; Liu, Lidong; Helm, Jeffrey; Liu, Lili; Georgiou, John; Wang, Yushan; Bissada, Nagat; Cheng, Kevin; Roder, John C; Wang, Yu Tian; Hayden, Michael R

2007-02-28

Huntingtin-interacting protein 1 (HIP1) is an endocytic adaptor protein that plays a role in clathrin-mediated endocytosis and the ligand-induced internalization of AMPA receptors (AMPARs) (Metzler et al., 2003). In the present study, we investigated the role of HIP1 in NMDA receptor (NMDAR) function by analyzing NMDA-dependent transport and NMDA-induced excitotoxicity in neurons from HIP1-/- mice. HIP1 colocalizes with NMDARs in hippocampal and cortical neurons and affinity purifies with NMDARs by GST (glutathione S-transferase) pull down and coimmunoprecipitation. A profound decrease in NMDA-induced AMPAR internalization of 75% occurs in neurons from HIP1-/- mice compared with wild type, using a quantitative single-cell-based internalization assay. This defect in NMDA-dependent removal of surface AMPARs is in agreement with the observed defect in long-term depression induction in hippocampal brain slices of HIP1-/- mice and supports a role of HIP1 in AMPAR internalization in vivo. HIP1-/- neurons are partially protected from NMDA-induced excitotoxicity as assessed by LDH (lactate dehydrogenase) release, TUNEL (terminal deoxynucleotidyl transferase-mediated biotinylated dUTP nick end labeling) and caspase-3 activation assays, which points to a role of HIP1 in NMDA-induced cell death. Interestingly, phosphorylation of Akt and its substrate huntingtin (htt) decreases during NMDA-induced excitotoxicity by 48 and 31%, respectively. This decrease is significantly modulated by HIP1, resulting in 94 and 48% changes in P-Akt and P-htt levels in HIP1-/- neurons, respectively. In summary, we have shown that HIP1 influences important NMDAR functions and that both HIP1 and htt participate in NMDA-induced cell death. These findings may provide novel insights into the cellular mechanisms underlying enhanced NMDA-induced excitotoxicity in Huntington's disease.

Neto-Mediated Intracellular Interactions Shape Postsynaptic Composition at the Drosophila Neuromuscular Junction

PubMed Central

Ramos, Cathy I.; Igiesuorobo, Oghomwen; Wang, Qi; Serpe, Mihaela

2015-01-01

The molecular mechanisms controlling the subunit composition of glutamate receptors are crucial for the formation of neural circuits and for the long-term plasticity underlying learning and memory. Here we use the Drosophila neuromuscular junction (NMJ) to examine how specific receptor subtypes are recruited and stabilized at synaptic locations. In flies, clustering of ionotropic glutamate receptors (iGluRs) requires Neto (Neuropillin and Tolloid-like), a highly conserved auxiliary subunit that is essential for NMJ assembly and development. Drosophila neto encodes two isoforms, Neto-α and Neto-β, with common extracellular parts and distinct cytoplasmic domains. Mutations that specifically eliminate Neto-β or its intracellular domain were generated. When Neto-β is missing or is truncated, the larval NMJs show profound changes in the subtype composition of iGluRs due to reduced synaptic accumulation of the GluRIIA subunit. Furthermore, neto-β mutant NMJs fail to accumulate p21-activated kinase (PAK), a critical postsynaptic component implicated in the synaptic stabilization of GluRIIA. Muscle expression of either Neto-α or Neto-β rescued the synaptic transmission at neto null NMJs, indicating that Neto conserved domains mediate iGluRs clustering. However, only Neto-β restored PAK synaptic accumulation at neto null NMJs. Thus, Neto engages in intracellular interactions that regulate the iGluR subtype composition by preferentially recruiting and/or stabilizing selective receptor subtypes. PMID:25905467

Small subunits of RNA polymerase: localization, levels and implications for core enzyme composition.

PubMed

Doherty, Geoff P; Fogg, Mark J; Wilkinson, Anthony J; Lewis, Peter J

2010-12-01

Bacterial RNA polymerases (RNAPs) contain several small auxiliary subunits known to co-purify with the core α, β and β' subunits. The ω subunit is conserved between Gram-positive and Gram-negative bacteria, while the δ subunit is conserved within, but restricted to, Gram-positive bacteria. Although various functions have been assigned to these subunits via in vitro assays, very little is known about their in vivo roles. In this work we constructed a pair of vectors to investigate the subcellular localization of the δ and ω subunits in Bacillus subtilis with respect to the core RNAP. We found these subunits to be closely associated with RNAP involved in transcribing both mRNA and rRNA operons. Quantification of these subunits revealed δ to be present at equimolar levels with RNAP and ω to be present at around half the level of core RNAP. For comparison, the localization and quantification of RNAP β' and ω subunits in Escherichia coli was also investigated. Similar to B. subtilis, β' and ω closely associated with the nucleoid and formed subnucleoid regions of high green fluorescent protein intensity, but, unlike ω in B. subtilis, ω levels in E. coli were close to parity with those of β'. These results indicate that δ is likely to be an integral RNAP subunit in Gram-positives, whereas ω levels differ substantially between Gram-positives and -negatives. The ω subunit may be required for RNAP assembly and subsequently be turned over at different rates or it may play roles in Gram-negative bacteria that are performed by other factors in Gram-positives.

Enhanced nitric oxide production during lead (Pb²⁺) exposure recovers protein expression but not presynaptic localization of synaptic proteins in developing hippocampal neurons.

PubMed

Neal, April P; Stansfield, Kirstie H; Guilarte, Tomás R

2012-02-23

We have previously reported that lead (Pb(2+)) exposure results in both presynaptic and postsynaptic changes in developing neurons as a result of inhibition of the N-methyl-d-aspartate receptor (NMDAR). NMDAR inhibition by Pb(2+) during synaptogenesis disrupts downstream trans-synaptic signaling of brain-derived neurotrophic factor (BDNF) and exogenous addition of BDNF can recover the effects of Pb(2+) on both presynaptic protein expression and presynaptic vesicular release. NMDAR activity can modulate other trans-synaptic signaling pathways, such as nitric oxide (NO) signaling. Thus, it is possible that other trans-synaptic pathways in addition to BDNF signaling may be disrupted by Pb(2+) exposure. The current study investigated whether exogenous addition of NO could recover the presynaptic vesicular proteins lost as a result of Pb(2+) exposure during synaptogenesis, namely Synaptophysin (Syn) and Synaptobrevin (Syb). We observed that exogenous addition of NO during Pb(2+) exposure results in complete recovery of whole-cell Syn levels and partial recovery of Syn and Syb synaptic targeting in Pb(2+)-exposed neurons. Copyright © 2011 Elsevier B.V. All rights reserved.

Astroglial CB1 Receptors Determine Synaptic D-Serine Availability to Enable Recognition Memory.

PubMed

Robin, Laurie M; Oliveira da Cruz, José F; Langlais, Valentin C; Martin-Fernandez, Mario; Metna-Laurent, Mathilde; Busquets-Garcia, Arnau; Bellocchio, Luigi; Soria-Gomez, Edgar; Papouin, Thomas; Varilh, Marjorie; Sherwood, Mark W; Belluomo, Ilaria; Balcells, Georgina; Matias, Isabelle; Bosier, Barbara; Drago, Filippo; Van Eeckhaut, Ann; Smolders, Ilse; Georges, Francois; Araque, Alfonso; Panatier, Aude; Oliet, Stéphane H R; Marsicano, Giovanni

2018-06-06

Bidirectional communication between neurons and astrocytes shapes synaptic plasticity and behavior. D-serine is a necessary co-agonist of synaptic N-methyl-D-aspartate receptors (NMDARs), but the physiological factors regulating its impact on memory processes are scantly known. We show that astroglial CB 1 receptors are key determinants of object recognition memory by determining the availability of D-serine at hippocampal synapses. Mutant mice lacking CB 1 receptors from astroglial cells (GFAP-CB 1 -KO) displayed impaired object recognition memory and decreased in vivo and in vitro long-term potentiation (LTP) at CA3-CA1 hippocampal synapses. Activation of CB 1 receptors increased intracellular astroglial Ca 2+ levels and extracellular levels of D-serine in hippocampal slices. Accordingly, GFAP-CB 1 -KO displayed lower occupancy of the co-agonist binding site of synaptic hippocampal NMDARs. Finally, elevation of D-serine levels fully rescued LTP and memory impairments of GFAP-CB 1 -KO mice. These data reveal a novel mechanism of in vivo astroglial control of memory and synaptic plasticity via the D-serine-dependent control of NMDARs. Copyright © 2018 Elsevier Inc. All rights reserved.

Spontaneous recovery of memory functions in an untreated case of anti NMDAR encephalitis - a reason to maintain hope.

PubMed

McIvor, Katherine; Moore, Perry

2017-01-01

Anti N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an autoimmune disorder that was only fully discovered recently and neuropsychological outcome data remains sparse. We present the case of BA, a 19-year-old male, which illustrates the cognitive outcome in an untreated case over a time period of over 2½ years. We conducted three cognitive assessments, including tests of memory and executive functioning, over this time period and considered the evidence for reliable change in memory function using the Wechsler Advanced Clinical Solutions (ACS) serial assessment package. Our findings revealed mild memory problems 6 months post-discharge with, at best, static and potentially declining memory functioning at follow-up assessment 12 months post-discharge. However, the results of testing at 30 months post-discharge revealed significant improvements in immediate and delayed memory index performances. Our report of a case of anti-NMDAR encephalitis provides evidence for spontaneous improvements in memory functioning occurring more than 2 years after initial assessment and also demonstrates both the utility and potential limitations of the ACS serial assessment software when used in a relatively typical clinical assessment situation.

Relationship of resting brain hyperconnectivity and schizophrenia-like symptoms produced by the NMDA receptor antagonist ketamine in humans.

PubMed

Driesen, N R; McCarthy, G; Bhagwagar, Z; Bloch, M; Calhoun, V; D'Souza, D C; Gueorguieva, R; He, G; Ramachandran, R; Suckow, R F; Anticevic, A; Morgan, P T; Krystal, J H

2013-11-01

N-methyl-D-aspartate glutamate receptor (NMDA-R) antagonists produce schizophrenia-like positive and negative symptoms in healthy human subjects. Preclinical research suggests that NMDA-R antagonists interfere with the function of gamma-aminobutyric acid (GABA) neurons and alter the brain oscillations. These changes have been hypothesized to contribute to psychosis. In this investigation, we evaluated the hypothesis that the NMDA-R antagonist ketamine produces alterations in cortical functional connectivity during rest that are related to symptoms. We administered ketamine to a primary sample of 22 subjects and to an additional, partially overlapping, sample of 12 subjects. Symptoms before and after the experimental session were rated with the Positive and Negative Syndrome Scale (PANSS). In the primary sample, functional connectivity was measured via functional magnetic resonance imaging almost immediately after infusion began. In the additional sample, this assessment was repeated after 45 min of continuous ketamine infusion. Global, enhanced functional connectivity was observed at both timepoints, and this hyperconnectivity was related to symptoms in a region-specific manner. This study supports the hypothesis that pathological increases in resting brain functional connectivity contribute to the emergence of positive and negative symptoms associated with schizophrenia.

Relationship of Resting Brain Hyperconnectivity and Schizophrenia-like Symptoms Produced by the NMDA receptor Antagonist Ketamine in Humans

PubMed Central

Driesen, Naomi R.; McCarthy, Gregory; Bhagwagar, Zubin; Bloch, Michael; Calhoun, Vincent; D’Souza, Deepak C.; Gueorguieva, Ralitza; He, George; Ramachandran, Ramani; Suckow, Raymond F.; Anticevic, Alan; Morgan, Peter T.; Krystal, John H.

2012-01-01

N-methyl-D-aspartate glutamate receptor (NMDA-R) antagonists produce schizophrenia-like positive and negative symptoms in healthy human subjects. Preclinical research suggests that NMDA-R antagonists interfere with the function of gamma-aminobutyric acid (GABA) neurons and alter brain oscillations. These changes have been hypothesized to contribute to psychosis. In this investigation, we evaluated the hypothesis that the NMDA-R antagonist ketamine produces alterations in cortical functional connectivity during rest that are related to symptoms. We administered ketamine to a primary sample of twenty-two subjects and to an additional, partially overlapping, sample of twelve subjects. Symptoms before and after the experimental session were rated with the Positive and Negative Symptom Scale (PANSS). In the primary sample, functional connectivity was measured via functional magnetic resonance imaging almost immediately after infusion began. In the additional sample, this assessment was repeated after 45 minutes of continuous ketamine infusion. Global, enhanced functional connectivity was observed at both timepoints and this hyperconnectivity was related to symptoms in a region-specific manner. This study supports the hypothesis that pathological increases in resting brain functional connectivity contribute to the emergence of positive and negative symptoms associated with schizophrenia. PMID:23337947