Anticonvulsant effect of minocycline on pentylenetetrazole-induced seizure in mice: involvement of nitric oxide and N-methyl-D-aspartate receptor.

PubMed

Amini-Khoei, Hossein; Kordjazy, Nastaran; Haj-Mirzaian, Arya; Amiri, Shayan; Haj-Mirzaian, Arvin; Shirzadian, Armin; Hasanvand, Amin; Balali-Dehkordi, Shima; Hassanipoor, Mahsa; Dehpour, Ahmad Reza

2018-03-20

Anticonvulsant effects of minocycline have been explored recently. This study was designed to examine the anticonvulsant effect of acute administration of minocycline on pentylenetetrazole (PTZ)-induced seizures in mouse considering the possible role of nitric oxide (NO)/NMDA pathway. We induced seizure using intravenous administration of PTZ. Our results showed that acute administration of minocycline increased the seizure threshold. Furthermore, co-administration of sub-effective doses of the non-selective nitric oxide synthase (NOS) inhibitor, L-NAME (10 mg/kg) and the neuronal NOS inhibitor, 7-nitroindazole (40 mg/kg) enhanced the anticonvulsant effect of sub-effective dose of minocycline (40 mg/kg). We found that inducible NOS inhibitor, aminoguanidine (100 mg/kg), had no effect on the anti-seizure effect of minocycline. Moreover, L-arginine (60 mg/kg), as a NOS substrate, reduced the anticonvulsant effect of minocycline. We also demonstrated that pretreatment with NMDA receptor antagonists, ketamine (0.5 mg/kg) and MK-801 (0.05 mg/kg) increased the anticonvulsant effect of sub-effective dose of minocycline. Results showed that minocycline significantly decreased the hippocampal nitrite level. Furthermore, co-administration of nNOS inhibitor like NMDA receptor antagonists augmented the effect of minocycline on the hippocampal nitrite level. In conclusion, we revealed that anticonvulsant effect of minocycline might be, at least in part, due to decline in constitutive hippocampal nitric oxide activity as well as inhibition of NMDA receptors.

Inhibition of DOR prevents remifentanil induced postoperative hyperalgesia through regulating the trafficking and function of spinal NMDA receptors in vivo and in vitro.

PubMed

Wang, Chunyan; Li, Yize; Wang, Haiyun; Xie, Keliang; Shu, Ruichen; Zhang, Linlin; Hu, Nan; Yu, Yonghao; Wang, Guolin

2015-01-01

Several studies have demonstrated that intraoperative remifentanil infusions have been associated with opioid-induced hyperalgesia (OIH). Activation of delta opioid receptor (DOR) and augmentation of N-methyl-d-aspartate (NMDA) receptor expression and function may play an important role in the development of OIH. The aim of this study was to investigate whether DOR inhibition could prevent remifentanil-induced hyperalgesia via regulating spinal NMDA receptor expression and function in vivo and in vitro. A rat model of remifentanil-induced postoperative hyperalgesia was performed with the DOR agonist deltorphin-deltorphin II or the DOR antagonist naltrindole injected intrathecally 10 min before remifentanil infusion. Mechanical and thermal hyperalgesia were measured at -24h, 2, 6, 24 and 48 h after remifentanil infusion. Western blot was applied to detect the membrane and total expression of DOR and NMDA receptor subunits (NR1, NR2A and NR2B) in spinal cord L4-L6 segments. In addition, whole-cell patch-clamp recording was used to investigate the effect of DOR inhibition on NMDA receptor-induced current in spinal cord slices in vitro. We found that membrane trafficking of DOR, NR1 and NR2B subunits in the spinal cord increased after remifentanil administration and surgery. The DOR antagonist naltrindole could attenuate mechanical and thermal hyperalgesia without affecting baseline nociceptive threshold, reduce membrane expression of DOR and decrease the membrane and total expressions of NR1 and NR2B subunits. Furthermore, the amplitude and the frequency of NMDA receptor-induced current were significantly increased by remifentanil incubation in neurons of the dorsal horn, which was reversed by the application of naltrindole. The above results indicate that inhibition of DOR could significantly inhibit remifentanil-induced hyperalgesia via modulating the total protein level, membrane trafficking and function of NMDA receptors in the dorsal horn of spinal cord, suggesting that naltrindole could be a potential anti-hyperalgesic agent for treating OIH. Copyright © 2014. Published by Elsevier Inc.

Interplay between non-NMDA and NMDA receptor activation during oscillatory wave propagation: Analyses of caffeine-induced oscillations in the visual cortex of rats.

PubMed

Yoshimura, Hiroshi; Sugai, Tokio; Kato, Nobuo; Tominaga, Takashi; Tominaga, Yoko; Hasegawa, Takahiro; Yao, Chenjuan; Akamatsu, Tetsuya

2016-07-01

Generation and propagation of oscillatory activities in cortical networks are important features of the brain. However, many issues related to oscillatory phenomena are unclear. We previously reported neocortical oscillation following caffeine treatment of rat brain slices. Input to the primary visual cortex (Oc1) generates N-methyl-d-aspartate (NMDA) receptor-dependent oscillations, and we proposed that the oscillatory signals originate in the secondary visual cortex (Oc2). Because non-NMDA and NMDA receptors cooperate in synaptic transmission, non-NMDA receptors may also play an important role in oscillatory activities. Here we investigated how non-NMDA receptor activities contribute to NMDA receptor-dependent oscillations by using optical recording methods. After induction of stable oscillations with caffeine application, blockade of NMDA receptors abolished the late stable oscillatory phase, but elicited 'hidden' non-NMDA receptor-dependent oscillation during the early depolarizing phase. An interesting finding is that the origin of the non-NMDA receptor-dependent oscillation moved from the Oc1, during the early phase, toward the origin of the NMDA receptor-dependent oscillation that is fixed in the Oc2. In addition, the frequency of the non-NMDA receptor-dependent oscillation was higher than that of the NMDA receptor-dependent oscillation. Thus, in one course of spatiotemporal oscillatory activities, the relative balance in receptor activities between non-NMDA and NMDA receptors gradually changes, and this may be due to the different kinetics of the two receptor types. These results suggest that interplay between the two receptor types in the areas of Oc1 and Oc2 may play an important role in oscillatory signal communication. Copyright © 2016 Elsevier Ltd. All rights reserved.

Interaction of PGHS-2 and glutamatergic mechanisms controlling the ovine fetal hypothalamus-pituitary-adrenal axis

PubMed Central

Knutson, Nathan

2010-01-01

Prostaglandins, generated within the fetal brain, are integral components of the mechanism controlling the fetal hypothalamus-pituitary-adrenal (HPA) axis. Previous studies in this laboratory demonstrated that prostaglandin G/H synthase isozyme 2 (PGHS-2) inhibition reduces the fetal HPA axis response to cerebral hypoperfusion, blocks the preparturient rise in fetal plasma ACTH concentration, and delays parturition. We also discovered that blockade of N-methyl-d-aspartate (NMDA) receptors reduces the fetal ACTH response to cerebral hypoperfusion. The present study was designed to test the hypothesis that PGHS-2 action and the downstream effect of HPA axis stimulation are stimulated by NMDA-mediated glutamatergic neurotransmission. Chronically catheterized late-gestation fetal sheep (n = 8) were injected with NMDA (1 mg iv). All responded with increases in fetal plasma ACTH and cortisol concentrations. Pretreatment with resveratrol (100 mg iv, n = 5), a specific inhibitor of PGHS-1, did not alter the magnitude of the HPA axis response to NMDA. Pretreatment with nimesulide (10 mg iv, n = 6), a specific inhibitor of PGHS-2, significantly reduced the HPA axis response to NMDA. To further explore this interaction, we injected NMDA in six chronically catheterized fetal sheep that were chronically infused with nimesulide (n = 6) at a rate of 1 mg/day into the lateral cerebral ventricle for 5–7 days. In this group, there was no significant ACTH response to NMDA. Finally, we tested whether the HPA axis response to prostaglandin E2 (PGE2) is mediated by NMDA receptors. Seven chronically catheterized late-gestation fetal sheep were injected with 100 ng of PGE2, which significantly increased fetal plasma ACTH and cortisol concentrations. Pretreatment with ketamine (10 mg iv), an NMDA antagonist, did not alter the ACTH or cortisol response to PGE2. We conclude that generation of prostanoids via the action of PGHS-2 in the fetal brain augments the fetal HPA axis response to NMDA-mediated glutamatergic stimulation. PMID:20445154

Voltage-dependent calcium channel involvement in NMDA-induced activation of NOS.

PubMed

Alagarsamy, S; Johnson, K M

1995-11-13

We have previously shown that N-methyl-D-aspartate (NMDA) increases nitric oxide synthase (NOS) activity in rat frontal cortex; however, the actual mechanism of this activation has not been addressed. Tetrodotoxin (TTX; 0.05 microM) inhibited NMDA-activated NOS, suggesting that TTX-sensitive Na+ channels are interposed between the NMDA receptors and the NOS cellular compartment. The NMDA response was also blocked by voltage-dependent Ca2+ channel (VDCC) blockers including Cd2+, Co2+, funnel web spider toxin (FTX) and omega-Aga IVa, but not by nifedipine or omega-conotoxin. These data suggest that Ca2+ flux through P- and/or Q-type VDCC subsequent to NMDA-induced depolarization may be at least as important for NOS activation as Ca2+ entry through the NMDA receptor.

The NH2-terminus of substance P modulates NMDA-induced activity in the mouse spinal cord.

PubMed

Hornfeldt, C S; Sun, X; Larson, A A

1994-05-01

Excitatory amino acids (EAAs) and substance P are believed to transmit nociceptive information in the spinal cord. As substance P NH2-terminal fragments can modulate non-NMDA EAA-mediated activity, we examined the effects of substance P fragments to ascertain whether the COOH- or NH2-terminus of substance P modulates the actions of NMDA in the spinal cord. NMDA activity was measured by the intensity of behaviors produced by NMDA (0.2 nmol) administered intrathecally in the mouse. The NMDA response was attenuated after pretreatment with either substance P (22.5 pmol, 30 min) or the NH2-terminal fragment of substance P, SP-(1-7). Pretreatment with the COOH-terminal fragment SP-(5-11) (22.5 pmol, 30 min), a neurokinin ligand, had no effect on NMDA-induced behaviors, suggesting that the inhibitory effect of substance P is caused by the NH2-terminus. Pretreatment with D-Pro2,D-Phe7 substance P-(1-7), a SP-(1-7) antagonist, potentiated NMDA activity, suggesting a tonic inhibitory effect of the substance P NH2-terminus. Desensitization to NMDA typically develops when NMDA is injected at 2 min intervals. While pretreatment with SP-(1-7) inhibited NMDA, coadministration of SP-(1-7) (22.5 pmol), with the first of four injections of NMDA, first inhibited but then potentiated responses to each challenge with NMDA. Coadministration of the same dose of SP-(1-7) with the fourth injection of NMDA immediately potentiated the response to NMDA.(ABSTRACT TRUNCATED AT 250 WORDS)

Glycine Potentiates AMPA Receptor Function through Metabotropic Activation of GluN2A-Containing NMDA Receptors

PubMed Central

Li, Li-Jun; Hu, Rong; Lujan, Brendan; Chen, Juan; Zhang, Jian-Jian; Nakano, Yasuko; Cui, Tian-Yuan; Liao, Ming-Xia; Chen, Jin-Cao; Man, Heng-Ye; Feng, Hua; Wan, Qi

2016-01-01

NMDA receptors are Ca2+-permeable ion channels. The activation of NMDA receptors requires agonist glutamate and co-agonist glycine. Recent evidence indicates that NMDA receptor also has metabotropic function. Here we report that in cultured mouse hippocampal neurons, glycine increases AMPA receptor-mediated currents independent of the channel activity of NMDA receptors and the activation of glycine receptors. The potentiation of AMPA receptor function by glycine is antagonized by the inhibition of ERK1/2. In the hippocampal neurons and in the HEK293 cells transfected with different combinations of NMDA receptors, glycine preferentially acts on GluN2A-containing NMDA receptors (GluN2ARs), but not GluN2B-containing NMDA receptors (GluN2BRs), to enhance ERK1/2 phosphorylation independent of the channel activity of GluN2ARs. Without requiring the channel activity of GluN2ARs, glycine increases AMPA receptor-mediated currents through GluN2ARs. Thus, these results reveal a metabotropic function of GluN2ARs in mediating glycine-induced potentiation of AMPA receptor function via ERK1/2 activation. PMID:27807405

NMDA receptor blockade in the prelimbic cortex activates the mesolimbic system and dopamine-dependent opiate reward signaling.

PubMed

Tan, Huibing; Rosen, Laura G; Ng, Garye A; Rushlow, Walter J; Laviolette, Steven R

2014-12-01

N-Methyl-D-aspartate (NMDA) receptors in the medial prefrontal cortex (mPFC) are involved in opiate reward processing and modulate sub-cortical dopamine (DA) activity. NMDA receptor blockade in the prelimbic (PLC) division of the mPFC strongly potentiates the rewarding behavioural properties of normally sub-reward threshold doses of opiates. However, the possible functional interactions between cortical NMDA and sub-cortical DAergic motivational neural pathways underlying these effects are not understood. This study examines how NMDA receptor modulation in the PLC influences opiate reward processing via interactions with sub-cortical DAergic transmission. We further examined whether direct intra-PLC NMDA receptor modulation may activate DA-dependent opiate reward signaling via interactions with the ventral tegmental area (VTA). Using an unbiased place conditioning procedure (CPP) in rats, we performed bilateral intra-PLC microinfusions of the competitive NMDA receptor antagonist, (2R)-amino-5-phosphonovaleric acid (AP-5), prior to behavioural morphine place conditioning and challenged the rewarding effects of morphine with DA receptor blockade. We next examined the effects of intra-PLC NMDA receptor blockade on the spontaneous activity patterns of presumptive VTA DA or GABAergic neurons, using single-unit, extracellular in vivo neuronal recordings. We show that intra-PLC NMDA receptor blockade strongly activates sub-cortical DA neurons within the VTA while inhibiting presumptive non-DA GABAergic neurons. Behaviourally, NMDA receptor blockade activates a DA-dependent opiate reward system, as pharmacological blockade of DA transmission blocked morphine reward only in the presence of intra-PLC NMDA receptor antagonism. These findings demonstrate a cortical NMDA-mediated mechanism controlling mesolimbic DAergic modulation of opiate reward processing.

An EP2 Agonist Facilitates NMDA-Induced Outward Currents and Inhibits Dendritic Beading through Activation of BK Channels in Mouse Cortical Neurons

PubMed Central

Hayashi, Yoshinori; Morinaga, Saori; Liu, Xia; Zhang, Jing; Wu, Zhou; Yokoyama, Takeshi; Nakanishi, Hiroshi

2016-01-01

Prostaglandin E2 (PGE2), a major metabolite of arachidonic acid produced by cyclooxygenase pathways, exerts its bioactive responses by activating four E-prostanoid receptor subtypes, EP1, EP2, EP3, and EP4. PGE2 enables modulating N-methyl-D-aspartate (NMDA) receptor-mediated responses. However, the effect of E-prostanoid receptor agonists on large-conductance Ca2+-activated K+ (BK) channels, which are functionally coupled with NMDA receptors, remains unclear. Here, we showed that EP2 receptor-mediated signaling pathways increased NMDA-induced outward currents (I NMDA-OUT), which are associated with the BK channel activation. Patch-clamp recordings from the acutely dissociated mouse cortical neurons revealed that an EP2 receptor agonist activated I NMDA-OUT, whereas an EP3 receptor agonist reduced it. Agonists of EP1 or EP4 receptors showed no significant effects on I NMDA-OUT. A direct perfusion of 3,5′-cyclic adenosine monophosphate (cAMP) through the patch pipette facilitated I NMDA-OUT, which was abolished by the presence of protein kinase A (PKA) inhibitor. Furthermore, facilitation of I NMDA-OUT caused by an EP2 receptor agonist was significantly suppressed by PKA inhibitor. Finally, the activation of BK channels through EP2 receptors facilitated the recovery phase of NMDA-induced dendritic beading in the primary cultured cortical neurons. These results suggest that a direct activation of BK channels by EP2 receptor-mediated signaling pathways plays neuroprotective roles in cortical neurons. PMID:27298516

Ethanol (EtOH) inhibition of NMDA-activated ion current is not voltage-dependent and EtOH does not interact with other binding sites on the NMDA receptor/ionophore complex

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

Lovinger, D.M.; White, G.; Weight, F.F.

1990-02-26

Recent studies indicate that intoxicating concentrations of EtOH inhibit neuronal responses to activation of NMDA-type glutamate receptors. The authors have observed that the potency of different alcohols for inhibiting NMDA-activated ion current in hippocampal neurons increases as a function of increasing hydrophobicity, suggesting that EtOH acts at a hydrophobic site. To further characterize the mechanisms of this effect, the authors examined the voltage-dependence of the EtOH inhibition of NMDA-activated ion current as well as potential interactions of EtOH with other effectors of the NMDA receptor/ionophore complex. The amount of inhibition of peak NMDA-activated current by 50 mM EtOH did notmore » differ over a range of membrane potentials from {minus}60 to +60 mV, and EtOH did not alter the reversal potential of NMDA-activated current. The percent inhibition observed in the presence of 10-100 mM EtOH did not differ with NMDA concentrations from 10-100 {mu}M. The percent inhibition by 50 mM EtOH (30-48%) did not differ in the absence or presence of the channel blockers Mg{sup 2+} (50-500 {mu}M), Zn{sup 2+} (5 and 20 {mu}M) or ketamine (2 and 10 {mu}M), or with increasing concentrations of the NMDA receptor cofactor glycine (0.01-1 {mu}M). These data indicate that: (i) EtOH does not change the ion selectivity of the ionophore, and (ii) EtOH does not appear to interact with previously described binding sites on the NMDA receptor/ionophore complex.« less

LY404187: a novel positive allosteric modulator of AMPA receptors.

PubMed

Quirk, Jennifer C; Nisenbaum, Eric S

2002-01-01

LY404187 is a selective, potent and centrally active positive allosteric modulator of AMPA receptors. LY404187 preferentially acts at recombinant human homomeric GluR2 and GluR4 versus GluR1 and GluR3 AMPA receptors. In addition, LY404187 potentiates the flip splice variant of these AMPA receptors to a greater degree than the flop splice variant. In both recombinant and native AMPA receptors, potentiation by LY404187 displays a unique time-dependent growth that appears to involve a suppression of the desensitization process of these ion channels. LY404187 has been shown to enhance glutamatergic synaptic transmission both in vitro and in vivo. This augmentation of synaptic activity is due to the direct potentiation of AMPA receptor function, as well as an indirect recruitment of voltage-dependent NMDA receptor activity. Enhanced calcium influx through NMDA receptors is known to be a critical step in initiating long-term modifications in synaptic function (e.g., long-term potentiation, LTP). These modifications in synaptic function may be substrates for certain forms of memory encoding. Consistent with a recruitment of NMDA receptor activity, LY404187 has been shown to enhance performance in animal models of cognitive function requiring different mnemonic processes. These data suggest that AMPA receptor potentiators may be therapeutically beneficial for treating cognitive deficits in a variety of disorders, particularly those that are associated with reduced glutamatergic signaling such as schizophrenia. In addition, LY404187 has been demonstrated to be efficacious in animal models of behavioral despair that possess considerable predictive validity for antidepressant activity. Although the therapeutic efficacy of AMPA receptor potentiators in these and other diseases will ultimately be determined in the clinic, evidence suggests that the benefit of these compounds will be mediated by multiple mechanisms of action. These mechanisms include direct enhancement of AMPA receptor function, secondary mobilization of intracellular signaling cascades, and prolonged modulation of gene expression.

Pharmacological specificity of N-methyl-D-aspartate discrimination in rats.

PubMed

Grech, D M; Willetts, J; Balster, R L

1993-04-01

The purpose of this study was to provide further information on the usefulness of N-methyl-D-aspartate (NMDA) discrimination in rats as a behavioral model for NMDA receptor activation. The pharmacological specificity of the NMDA discriminative stimulus was examined in rats trained to discriminate 30 mg/kg, i.p. NMDA from saline using a 2-lever fixed-ratio (FR) 32 food reinforcement schedule. Pharmacologically diverse centrally-acting agents were examined for their ability to substitute for NMDA. Morphine did not substitute for NMDA; neither did the central stimulants, caffeine and (+)-amphetamine, which produced a maximum mean of only 16 and 35% NMDA-lever responding, respectively. Pentylenetetrazol and picrotoxin also did not substitute for NMDA. Compounds interacting with cholinergic neurotransmission including nicotine, physostigmine, arecoline and mecamylamine, produced at best, only intermediate levels of NMDA-lever responding (32-61%), with the highest levels of NMDA-lever responding generally occurring at doses that also reduced rates of responding. These results suggest that the discriminative stimulus properties of NMDA are dissimilar from those of a number of centrally-acting drugs. Combined with the results of studies indicating that the NMDA discriminative stimulus can be antagonized by competitive NMDA antagonists, these results provide further evidence that NMDA receptor activation is the basis of NMDA discrimination and that this model may be useful for studying site-selective NMDA agonists and antagonists.

Suppression of Neurotoxic Lesion-Induced Seizure Activity: Evidence for a Permanent Role for the Hippocampus in Contextual Memory

PubMed Central

Sparks, Fraser T.; Lehmann, Hugo; Hernandez, Khadaryna; Sutherland, Robert J.

2011-01-01

Damage to the hippocampus (HPC) using the excitotoxin N-methyl-D-aspartate (NMDA) can cause retrograde amnesia for contextual fear memory. This amnesia is typically attributed to loss of cells in the HPC. However, NMDA is also known to cause intense neuronal discharge (seizure activity) during the hours that follow its injection. These seizures may have detrimental effects on retrieval of memories. Here we evaluate the possibility that retrograde amnesia is due to NMDA-induced seizure activity or cell damage per se. To assess the effects of NMDA induced activity on contextual memory, we developed a lesion technique that utilizes the neurotoxic effects of NMDA while at the same time suppressing possible associated seizure activity. NMDA and tetrodotoxin (TTX), a sodium channel blocker, are simultaneously infused into the rat HPC, resulting in extensive bilateral damage to the HPC. TTX, co-infused with NMDA, suppresses propagation of seizure activity. Rats received pairings of a novel context with foot shock, after which they received NMDA-induced, TTX+NMDA-induced, or no damage to the HPC at a recent (24 hours) or remote (5 weeks) time point. After recovery, the rats were placed into the shock context and freezing was scored as an index of fear memory. Rats with an intact HPC exhibited robust memory for the aversive context at both time points, whereas rats that received NMDA or NMDA+TTX lesions showed a significant reduction in learned fear of equal magnitude at both the recent and remote time points. Therefore, it is unlikely that observed retrograde amnesia in contextual fear conditioning are due to disruption of non-HPC networks by propagated seizure activity. Moreover, the memory deficit observed at both time points offers additional evidence supporting the proposition that the HPC has a continuing role in maintaining contextual memories. PMID:22110648

Regulation of tyrosine hydroxylase activity and phosphorylation at Ser(19) and Ser(40) via activation of glutamate NMDA receptors in rat striatum.

PubMed

Lindgren, N; Xu, Z Q; Lindskog, M; Herrera-Marschitz, M; Goiny, M; Haycock, J; Goldstein, M; Hökfelt, T; Fisone, G

2000-06-01

The activity of tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of dopamine, is stimulated by phosphorylation. In this study, we examined the effects of activation of NMDA receptors on the state of phosphorylation and activity of tyrosine hydroxylase in rat striatal slices. NMDA produced a time-and concentration-dependent increase in the levels of phospho-Ser(19)-tyrosine hydroxylase in nigrostriatal nerve terminals. This increase was not associated with any changes in the basal activity of tyrosine hydroxylase, measured as DOPA accumulation. Forskolin, an activator of adenylyl cyclase, stimulated tyrosine hydroxylase phosphorylation at Ser(40) and caused a significant increase in DOPA accumulation. NMDA reduced forskolin-mediated increases in both Ser(40) phosphorylation and DOPA accumulation. In addition, NMDA reduced the increase in phospho-Ser(40)-tyrosine hydroxylase produced by okadaic acid, an inhibitor of protein phosphatase 1 and 2A, but not by a cyclic AMP analogue, 8-bromo-cyclic AMP. These results indicate that, in the striatum, glutamate decreases tyrosine hydroxylase phosphorylation at Ser(40) via activation of NMDA receptors by reducing cyclic AMP production. They also provide a mechanism for the demonstrated ability of NMDA to decrease tyrosine hydroxylase activity and dopamine synthesis.

Celastrus paniculatus seed water soluble extracts protect against glutamate toxicity in neuronal cultures from rat forebrain.

PubMed

Godkar, Praful B; Gordon, Richard K; Ravindran, Arippa; Doctor, Bhupendra P

2004-08-01

Aqueous extracts of Celastrus paniculatus (CP) seed have been reported to improve learning and memory in rats. In addition, these extracts were shown to have antioxidant properties, augmented endogenous antioxidant enzymes, and decreased lipid peroxidation in rat brain. However, water soluble extracts of CP seed (CP-WSE) have not been evaluated for their neuroprotective effects. In the study reported here, we used enriched forebrain primary neuronal cell (FBNC) cultures to study the neuroprotective effects of three CP-WSE extracts (a room temperature, WF; a hot water, HF; and an acid, AF) on glutamate-induced toxicity. FBNC were pre-treated with the CP-WSE and then with glutamate to evaluate the protection afforded against excitatory amino acid-induced toxicity. The criteria for neuroprotection were based on the effects of CP-WSE on a mitochondrial function test following glutamate-induced neurotoxicity. Pre-treatment of neuronal cells with CP-WSE significantly attenuated glutamate-induced neuronal death. To understand the molecular mechanism of action of CP-WSE, we conducted electrophysiological studies using patch-clamp techniques on N-methyl-D-aspartate (NMDA)-activated whole-cell currents in FBNC. WSE significantly and reversibly inhibited whole-cell currents activated by NMDA. The results suggest that CP-WSE protected neuronal cells against glutamate-induced toxicity by modulating glutamate receptor function.

The interplay of cannabinoid and NMDA glutamate receptor systems in humans: preliminary evidence of interactive effects of cannabidiol and ketamine in healthy human subjects.

PubMed

Hallak, Jaime E C; Dursun, Serdar M; Bosi, Daniel C; de Macedo, Ligia Ribeiro Horta; Machado-de-Sousa, João Paulo; Abrão, João; Crippa, José A S; McGuire, Phillip; Krystal, John H; Baker, Glen B; Zuardi, Antonio W

2011-01-15

Interactions between glutamatergic and endocannabinoid systems may contribute to schizophrenia, dissociative states, and other psychiatric conditions. Cannabidiol (CBD), a cannabinoid-1/2 (CB1/2) receptor weak partial agonist or antagonist, may play a role in the treatment of schizophrenia. This study tested the hypothesis that CBD would attenuate the behavioral effects of the NMDA receptor antagonist, ketamine, in healthy human subjects. Ten male healthy volunteers were evaluated twice in a randomized order. In both sessions they received ketamine (bolus of 0.26 mg/kg/1 min followed by IV infusion of 0.25mg/kg over 30 min) preceded by either CBD (600 mg) or placebo. Psychopathology was assessed using the Brief Psychiatric Rating Scale (BPRS) and the CADSS (Clinician Administered Dissociative States Scale) at regular intervals from 30 min before to 90 min after ketamine administration. CBD significantly augmented the activating effects of ketamine, as measured by the activation subscales of the BPRS. However, CBD also showed a non-significant trend to reduce ketamine-induced depersonalization, as measured by the CADSS. These data describe a complex pattern of psychopharmacologic interactions between CBD and ketamine at the doses of each agent studied in this experiment. Copyright © 2010 Elsevier B.V. All rights reserved.

NMDA receptor gating of information flow through the striatum in vivo.

PubMed

Pomata, Pablo E; Belluscio, Mariano A; Riquelme, Luis A; Murer, M Gustavo

2008-12-10

A role of NMDA receptors in corticostriatal synaptic plasticity is widely acknowledged. However, the conditions that allow NMDA receptor activation in the striatum in vivo remain obscure. Here we show that NMDA receptors contribute to sustain the membrane potential of striatal medium spiny projection neurons close to threshold during spontaneous UP states in vivo. Moreover, we found that the blockade of striatal NMDA receptors reduces markedly the spontaneous firing of ensembles of medium spiny neurons during slow waves in urethane-anesthetized rats. We speculate that recurrent activation of NMDA receptors during UP states allows off-line information flow through the striatum and system level consolidation during habit formation.

Evaluation of the role of NMDA receptor function in antidepressant-like activity. A new study with citalopram and fluoxetine in the forced swim test in mice.

PubMed

Wolak, Małgorzata; Siwek, Agata; Szewczyk, Bernadeta; Poleszak, Ewa; Bystrowska, Beata; Moniczewski, Andrzej; Rutkowska, Anita; Młyniec, Katarzyna; Nowak, Gabriel

2015-06-01

The NMDA/glutamate receptors are involved in the mechanism of antidepressant activity. The present study was designed to investigate the effect of NMDA receptor ligands (agonists and antagonists of glutamate sites) on the antidepressant-like activity of selective serotonin reuptake inhibitors (SSRIs), citalopram and fluoxetine, in the forced swim test in mice. The antidepressant activity (reduction in immobility time) of citalopram but not of fluoxetine was antagonized by N-methyl-D-aspartate acid and enhanced by CGP37849 (antagonist of the NMDA receptor). The present literature data indicate that the antidepressant-like activity of conventional antidepressants is generally affected by the NMDA receptor, although by modulation from different sites of the complex. Thus, it supports the issue of the ability of NMDA receptor antagonists to enhance the antidepressant action in human depression. Copyright © 2014 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

NMDA/glutamate mechanism of magnesium-induced anxiolytic-like behavior in mice.

PubMed

Poleszak, Ewa; Wlaź, Piotr; Wróbel, Andrzej; Fidecka, Sylwia; Nowak, Gabriel

2008-01-01

The anxiolytic-like activity of magnesium in mice during the elevated plus maze (EPM) has been demonstrated previously. In the present study, we examined the involvement of NMDA/glutamate receptor ligands on the magnesium effect on the EPM. We demonstrated that low, ineffective doses of NMDA antagonists (the competitive NMDA antagonist CGP 37849, 0.3 mg/kg; an antagonist of the glycineB sites, L-701,324, 1 mg/kg; a partial agonist of the glycineB sites, D-cycloserine, 2.5 mg/kg; and the non-competitive NMDA antagonist MK-801, 0.05 mg/kg) administered together with an ineffective dose of magnesium (10 mg/kg) evoked a significant increase in the percentage of time spent in the open arm of the maze (an index of anxiety). Moreover, magnesium-induced anxiolytic-like activity (20 mg/kg) was antagonized by D-serine (100 nmol/mouse), an agonist of glycineB site of the NMDA receptor complex. The present study demonstrates the involvement of the NMDA/glutamate pathway in the magnesium anxiolytic-like activity in the EPM in mice, and that this activity particularly involves the glycineB sites.

NMDA Receptor Activity in Circulating Red Blood Cells: Methods of Detection.

PubMed

Makhro, Asya; Kaestner, Lars; Bogdanova, Anna

2017-01-01

Abundance and activity of N-methyl-D-aspartate (NMDA) in circulating red blood cells contributes to the maintenance of intracellular Ca 2+ in these cells and, by doing that, controls red cell volume, membrane stability, and O 2 carrying capacity. Detection of the NMDA receptor activity in red blood cells is challenging as the number of its copies is low and shows substantial cell-to-cell heterogeneity. Receptor abundance is reliably assessed using the radiolabeled antagonist ([ 3 H]MK-801) binding technique. Uptake of Ca 2+ following the NMDA receptor activation is detected in cells loaded with Ca 2+ -sensitive fluorescent dye Fluo-4 AM. Both microfluorescence live-cell imaging and flow cytometry may be used for fluorescence intensity detection. Automated patch clamp is currently used for recording of electric currents triggered by the stimulation of the NMDA receptor. These currents are mediated by the Ca 2+ -sensitive K + (Gardos) channels that open upon Ca 2+ uptake via the active NMDA receptor. Furthermore, K + flux through the Gardos channels induced by the NMDA receptor stimulation in red blood cells may be detected using unidirectional K + ( 86 Rb + ) influx.

Simvastatin Prevents Dopaminergic Neurodegeneration in Experimental Parkinsonian Models: The Association with Anti-Inflammatory Responses

PubMed Central

Zhang, Limin; Wu, Aimin; Yang, Yu; Xiong, Zhaojun; Deng, Chao; Huang, Xu-Feng; Yenari, Midori A.; Yang, Yuan-Guo; Ying, Weihai; Wang, Qing

2011-01-01

Background In addition to their original applications to lowering cholesterol, statins display multiple neuroprotective effects. N-methyl-D-aspartate (NMDA) receptors interact closely with the dopaminergic system and are strongly implicated in therapeutic paradigms of Parkinson's disease (PD). This study aims to investigate how simvastatin impacts on experimental parkinsonian models via regulating NMDA receptors. Methodology/Principal Findings Regional changes in NMDA receptors in the rat brain and anxiolytic-like activity were examined after unilateral medial forebrain bundle lesion by 6-hydroxydopamine via a 3-week administration of simvastatin. NMDA receptor alterations in the post-mortem rat brain were detected by [3H]MK-801(Dizocilpine) binding autoradiography. 6-hydroxydopamine treated PC12 was applied to investigate the neuroprotection of simvastatin, the association with NMDA receptors, and the anti-inflammation. 6-hydroxydopamine induced anxiety and the downregulation of NMDA receptors in the hippocampus, CA1(Cornu Ammonis 1 Area), amygdala and caudate putamen was observed in 6-OHDA(6-hydroxydopamine) lesioned rats whereas simvastatin significantly ameliorated the anxiety-like activity and restored the expression of NMDA receptors in examined brain regions. Significant positive correlations were identified between anxiolytic-like activity and the restoration of expression of NMDA receptors in the hippocampus, amygdala and CA1 following simvastatin administration. Simvastatin exerted neuroprotection in 6-hydroxydopamine-lesioned rat brain and 6-hydroxydopamine treated PC12, partially by regulating NMDA receptors, MMP9 (matrix metalloproteinase-9), and TNF-a (tumour necrosis factor-alpha). Conclusions/Significance Our results provide strong evidence that NMDA receptor modulation after simvastatin treatment could partially explain its anxiolytic-like activity and anti-inflammatory mechanisms in experimental parkinsonian models. These findings contribute to a better understanding of the critical roles of simvastatin in treating PD via NMDA receptors. PMID:21731633

Simvastatin prevents dopaminergic neurodegeneration in experimental parkinsonian models: the association with anti-inflammatory responses.

PubMed

Yan, Junqiang; Xu, Yunqi; Zhu, Cansheng; Zhang, Limin; Wu, Aimin; Yang, Yu; Xiong, Zhaojun; Deng, Chao; Huang, Xu-Feng; Yenari, Midori A; Yang, Yuan-Guo; Ying, Weihai; Wang, Qing

2011-01-01

In addition to their original applications to lowering cholesterol, statins display multiple neuroprotective effects. N-methyl-D-aspartate (NMDA) receptors interact closely with the dopaminergic system and are strongly implicated in therapeutic paradigms of Parkinson's disease (PD). This study aims to investigate how simvastatin impacts on experimental parkinsonian models via regulating NMDA receptors. Regional changes in NMDA receptors in the rat brain and anxiolytic-like activity were examined after unilateral medial forebrain bundle lesion by 6-hydroxydopamine via a 3-week administration of simvastatin. NMDA receptor alterations in the post-mortem rat brain were detected by [³H]MK-801(Dizocilpine) binding autoradiography. 6-hydroxydopamine treated PC12 was applied to investigate the neuroprotection of simvastatin, the association with NMDA receptors, and the anti-inflammation. 6-hydroxydopamine induced anxiety and the downregulation of NMDA receptors in the hippocampus, CA1(Cornu Ammonis 1 Area), amygdala and caudate putamen was observed in 6-OHDA(6-hydroxydopamine) lesioned rats whereas simvastatin significantly ameliorated the anxiety-like activity and restored the expression of NMDA receptors in examined brain regions. Significant positive correlations were identified between anxiolytic-like activity and the restoration of expression of NMDA receptors in the hippocampus, amygdala and CA1 following simvastatin administration. Simvastatin exerted neuroprotection in 6-hydroxydopamine-lesioned rat brain and 6-hydroxydopamine treated PC12, partially by regulating NMDA receptors, MMP9 (matrix metalloproteinase-9), and TNF-a (tumour necrosis factor-alpha). Our results provide strong evidence that NMDA receptor modulation after simvastatin treatment could partially explain its anxiolytic-like activity and anti-inflammatory mechanisms in experimental parkinsonian models. These findings contribute to a better understanding of the critical roles of simvastatin in treating PD via NMDA receptors.

Cell signaling pathways in the mechanisms of neuroprotection afforded by bergamot essential oil against NMDA-induced cell death in vitro.

PubMed

Corasaniti, M T; Maiuolo, J; Maida, S; Fratto, V; Navarra, M; Russo, R; Amantea, D; Morrone, L A; Bagetta, G

2007-06-01

The effects of bergamot essential oil (BEO; Citrus bergamia, Risso) on excitotoxic neuronal damage was investigated in vitro. The study was performed in human SH-SY5Y neuroblastoma cells exposed to N-methyl-D-aspartate (NMDA). Cell viability was measured by dye exclusion. Reactive oxygen species (ROS) and caspase-3 activity were measured fluorimetrically. Calpain I activity and the activation (phosphorylation) of Akt and glycogen synthase kinase-3beta (GSK-3beta) were assayed by Western blotting. NMDA induced concentration-dependent, receptor-mediated, death of SH-SY5Y cells, ranging from 11 to 25% (0.25-5 mM). Cell death induced by 1 mM NMDA (21%) was preceded by a significant accumulation of intracellular ROS and by a rapid activation of the calcium-activated protease calpain I. In addition, NMDA caused a rapid deactivation of Akt kinase and this preceded the detrimental activation of the downstream kinase, GSK-3beta. BEO (0.0005-0.01%) concentration dependently reduced death of SH-SY5Y cells caused by 1 mM NMDA. In addition to preventing ROS accumulation and activation of calpain, BEO (0.01%) counteracted the deactivation of Akt and the consequent activation of GSK-3beta, induced by NMDA. Results obtained by using specific fractions of BEO, suggested that monoterpene hydrocarbons were responsible for neuroprotection afforded by BEO against NMDA-induced cell death. Our data demonstrate that BEO reduces neuronal damage caused in vitro by excitotoxic stimuli and that this neuroprotection was associated with prevention of injury-induced engagement of critical death pathways.

Vinpocetine protects inner retinal neurons with functional NMDA glutamate receptors against retinal ischemia.

PubMed

Nivison-Smith, Lisa; Khoo, Pauline; Acosta, Monica L; Kalloniatis, Michael

2018-02-01

Retinal ischemia is involved in the pathogenesis of many major vision threatening diseases. Vinpocetine is a natural drug, which has a range of neuroprotective actions against retinal ischemia including modulating cation flow, improving metabolic activity and preventing apoptosis. The exact mechanism behind these actions remains unknown but may involve glutamate receptors, major components of the ischemic cascade. This study examined the effects of vinpocetine in association with specific ionotropic glutamate receptor agonists: N-methyl-D-aspartate (NMDA) and kainate. Vinpocetine's actions to improve cation channel permeability and cell marker immunoreactivity following ischemia appeared to be limited to NMDA activation with no changes observed following kainate stimulation. Vinpocetine's actions were lost in the presence of an NMDA receptor inhibitor further suggesting they may be secondary to NMDA receptor activation. NMDA receptor function was also necessary for vinpocetine's actions on glucose availability during ischemia but not lactate dehydrogenase (LDH) activity in the ischemic retina suggesting not all of vinpocetine's actions are linked to NMDA receptor function. These results may explain vinpocetine's effectiveness as a neuroprotective agent as the NMDA receptor is implicated in the pathogenesis of ischemia in a range of tissues of the central nervous system. Copyright © 2017 Elsevier Ltd. All rights reserved.

Activation of N-methyl-d-aspartate receptors reduces heart rate variability and facilitates atrial fibrillation in rats.

PubMed

Shi, Shaobo; Liu, Tao; Wang, Dandan; Zhang, Yan; Liang, Jinjun; Yang, Bo; Hu, Dan

2017-07-01

The goal of this study was to assess the effects of N-methyl-d-aspartate (NMDA) receptors activation on heart rate variability (HRV) and susceptibility to atrial fibrillation (AF). Rats were randomized for treatment with saline, NMDA (agonist of NMDA receptors), or NMDA plus MK-801 (antagonist of NMDA receptors) for 2 weeks. Heart rate variability was evaluated by using implantable electrocardiogram telemeters. Atrial fibrillation susceptibility was assessed with programmed stimulation in isolated hearts. Compared with the controls, the NMDA-treated rats displayed a decrease in the standard deviation of normal RR intervals, the standard deviation of the average RR intervals, the mean of the 5-min standard deviations of RR intervals, the root mean square of successive differences, and high frequency (HF); and an increase in low frequency (LF) and LF/HF (all P< 0.01). Additionally, the NMDA-treated rats showed prolonged activation latency and reduced effective refractory period (all P< 0.01). Importantly, AF was induced in all NMDA-treated rats. While atrial fibrosis developed, connexin40 downgraded and metalloproteinase 9 upgraded in the NMDA-treated rats (all P< 0.01). Most of the above alterations were mitigated by co-administering with MK-801. These results indicate that NMDA receptors activation reduces HRV and enhances AF inducibility, with cardiac autonomic imbalance, atrial fibrosis, and degradation of gap junction protein identified as potential mechanistic contributors. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

Serial EEG findings in anti-NMDA receptor encephalitis: correlation between clinical course and EEG.

PubMed

Ueda, Jun; Kawamoto, Michi; Hikiami, Ryota; Ishii, Junko; Yoshimura, Hajime; Matsumoto, Riki; Kohara, Nobuo

2017-12-01

Anti-NMDA receptor encephalitis is a paraneoplastic encephalitis characterised by psychiatric features, involuntary movement, and autonomic instability. Various EEG findings in patients with anti-NMDA receptor encephalitis have been reported, however, the correlation between the EEG findings and clinical course of anti-NMDA receptor encephalitis remains unclear. We describe a patient with anti-NMDA receptor encephalitis with a focus on EEG findings, which included: status epilepticus, generalised rhythmic delta activity, excess beta activity, extreme delta brush, and paroxysmal alpha activity upon arousal from sleep, which we term"arousal alpha pattern". Initially, status epilepticus was observed on the EEG when the patient was comatose with conjugate deviation. The EEG then indicated excess beta activity, followed by the emergence of continuous slow activity, including generalised rhythmic delta activity and extreme delta brush, in the most severe phase. Slow activity gradually faded in parallel with clinical amelioration. Excess beta activity persisted, even after the patient became almost independent in daily activities, and finally disappeared with full recovery. In summary, our patient with anti-NMDA receptor encephalitis demonstrated slow activity on the EEG, including extreme delta brush during the most severe phase, which gradually faded in parallel with clinical amelioration, with excess beta activity persisting into the recovery phase.

Pharmacological properties of excitatory amino acid induced changes in extracellular calcium concentration in rat hippocampal slices.

PubMed

Arens, J; Stabel, J; Heinemann, U

1992-01-01

We have studied extracellular ionic changes induced by iontophoretic application of excitatory amino acids in rat hippocampal slices. In contrast to kinetics of changes in [Ca2+]o, kinetics of changes in [K+]o, [Na+]o, [Cl-]o as well as in extracellular space size were comparable for different glutamate receptor agonists. Thus, alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA), quisqualate (quis), and kainate caused reductions in [Ca2+]o followed by an increase of [Ca2+]o above baseline, whereas glutamate, aspartate, N-methyl-D-aspartate (NMDA), and DL-homocysteic acid caused only reductions in [Ca2+]o. After blocking the NMDA receptors with ketamine and 2-amino-5- phosphonovaleric acid (2-APV), glutamate-induced decreases in [Ca2+]o were followed by an overshoot. Reduction of the transmembrane Na+ gradient by lowering [Na+]o, blocking of the Na(+)-K+ ATPase by lowering [K+]o, and application of ouabain blocked the overshoots after quis application, whereas vanadate, a blocker of the Ca(2+)-Mg2+ ATPase, had no effects. Lithium enhanced the reductions in [Ca2+]o and blocked the overshoots. Amiloride also reduced the overshoots. All organic Ca2+ entry blockers diminished reductions of [Ca2+]o but increased the overshoots. Inorganic Ca2+ antagonists had variable effects. Ni2+ had similar effects as the organic Ca2+ entry blockers while Cd2+ reduced both the [Ca2+]o decreases as well as the subsequent overshoots. Co2+ had initially a similar action as Ni2+. With prolonged application, [Ca2+]o decreases became augmented and, during wash, overshoots could no longer be elicited. We suggest that the overshoots in [Ca2+]o are due to a combined effect of extracellular space shrinkage and activation of the Na+/Ca2+ exchangers. This would imply that NMDA receptor activation blocks extrusion of Ca2+ from the cells. We tested the hypothesis that quis-induced intracellular Ca2+ release and extrusion of Ca2+ from the cells contributed to the overshoots. Dantrolene was without effect on the quis-induced signals, while ryanodine reduced the overshoots. Caffeine on the other hand diminished the [Ca2+]o decreases with no effects on the overshoots. To test for possible second messenger routes by which NMDA receptor activation might slow Ca2+ extrusion from cells, we investigated the effects of arachidonic acid and N-monomethyl-D- arginine on the quis-induced signals. While these agents reduced decreases in [Ca2+]o, they had no clear effects on the overshoots. Thus a possible route by which NMDA receptor activation may affect Ca2+ extrusion from cells has still to be elucidated.

Astrocytic Activation Generates De Novo Neuronal Potentiation and Memory Enhancement.

PubMed

Adamsky, Adar; Kol, Adi; Kreisel, Tirzah; Doron, Adi; Ozeri-Engelhard, Nofar; Melcer, Talia; Refaeli, Ron; Horn, Henrike; Regev, Limor; Groysman, Maya; London, Michael; Goshen, Inbal

2018-05-18

Astrocytes respond to neuronal activity and were shown to be necessary for plasticity and memory. To test whether astrocytic activity is also sufficient to generate synaptic potentiation and enhance memory, we expressed the Gq-coupled receptor hM3Dq in CA1 astrocytes, allowing their activation by a designer drug. We discovered that astrocytic activation is not only necessary for synaptic plasticity, but also sufficient to induce NMDA-dependent de novo long-term potentiation in the hippocampus that persisted after astrocytic activation ceased. In vivo, astrocytic activation enhanced memory allocation; i.e., it increased neuronal activity in a task-specific way only when coupled with learning, but not in home-caged mice. Furthermore, astrocytic activation using either a chemogenetic or an optogenetic tool during acquisition resulted in memory recall enhancement on the following day. Conversely, directly increasing neuronal activity resulted in dramatic memory impairment. Our findings that astrocytes induce plasticity and enhance memory may have important clinical implications for cognitive augmentation treatments. Copyright © 2018 Elsevier Inc. All rights reserved.

A role for synaptic and network plasticity in controlling epileptiform activity in CA1 in the kainic acid-lesioned rat hippocampus in vitro.

PubMed Central

Bernard, C; Wheal, H V

1996-01-01

1. Stimulation of the surviving afferents in the stratum radiatum of the CA1 area in kainic acid-lesioned hippocampal slices produced graded epileptiform activity, part of which (> 20%) involved the activation of N-methyl-D-aspartate (NMDA) receptors. There was also a failure of synaptic inhibition in this region. In this preparation, we have tested the effects of low-frequency stimulation (LFS; 1 Hz for 15 min) on synaptic responses and epileptiform activity. 2. LFS resulted in long-term depression (LTD) of excitatory synaptic potentials (EPSPs), long-term decrease of population spike amplitudes (PSAs) and EPSP-spike (E-S) potentiation. Evoked epileptiform activity was reduced but neurons had a higher probability of discharge. LTD could be reversed by subsequent tetanic stimulation whereas E-S dissociation remained unchanged. Synaptic and network responses could be saturated towards either potentiation or depression. However, E-S potentiation was maximal following the first conditioning stimulus. 3. NMDA receptor-mediated responses were pharmacologically isolated. LFS resulted in LTD of synaptic responses, long-term decrease of PSAs and E-S depression. These depressions could not be reversed by subsequent tetanic stimulation. alpha-Amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA) and NMDA receptor-mediated responses were then measured in isolation before and following conditioning stimuli. LFS was shown to simultaneously produce LTD of AMPA and NMDA receptor-mediated responses. E-S potentiation of the AMPA component and E-S depression of the NMDA component occurred coincidentally. 4. LTD of AMPA and NMDA receptor-mediated responses were shown to be NMDA dependent. In contrast, E-S potentiation and depression occurred even when NMDA receptors were pharmacologically blocked. 5. These findings indicate that synaptic responses could be modified bidirectionally in the CA1 area of kainic acid-lesioned rat hippocampus in an NMDA receptor-dependent manner. However, E-S dissociations were independent of the activation of NMDA receptors, hinting at mechanisms different from those of synaptic LTD. We suggest that changes in E-S coupling were caused by a modification of the firing threshold of the CA1 pyramidal neurons. Furthermore, the firing mechanisms controlling NMDA and AMPA receptor-mediated network activity appeared to be different. The possible use of LFS applied to the hippocampus as a clinical intervention to suppress epileptiform activity is discussed. PMID:8866357

Cell signaling pathways in the mechanisms of neuroprotection afforded by bergamot essential oil against NMDA-induced cell death in vitro

PubMed Central

Corasaniti, M T; Maiuolo, J; Maida, S; Fratto, V; Navarra, M; Russo, R; Amantea, D; Morrone, L A; Bagetta, G

2007-01-01

Background and purpose: The effects of bergamot essential oil (BEO; Citrus bergamia, Risso) on excitotoxic neuronal damage was investigated in vitro. Experimental approach: The study was performed in human SH-SY5Y neuroblastoma cells exposed to N-methyl-D-aspartate (NMDA). Cell viability was measured by dye exclusion. Reactive oxygen species (ROS) and caspase-3 activity were measured fluorimetrically. Calpain I activity and the activation (phosphorylation) of Akt and glycogen synthase kinase-3β (GSK-3β) were assayed by Western blotting. Key results: NMDA induced concentration-dependent, receptor-mediated, death of SH-SY5Y cells, ranging from 11 to 25% (0.25–5 mM). Cell death induced by 1 mM NMDA (21%) was preceded by a significant accumulation of intracellular ROS and by a rapid activation of the calcium-activated protease calpain I. In addition, NMDA caused a rapid deactivation of Akt kinase and this preceded the detrimental activation of the downstream kinase, GSK-3β. BEO (0.0005–0.01%) concentration dependently reduced death of SH-SY5Y cells caused by 1 mM NMDA. In addition to preventing ROS accumulation and activation of calpain, BEO (0.01%) counteracted the deactivation of Akt and the consequent activation of GSK-3β, induced by NMDA. Results obtained by using specific fractions of BEO, suggested that monoterpene hydrocarbons were responsible for neuroprotection afforded by BEO against NMDA-induced cell death. Conclusions and Implications: Our data demonstrate that BEO reduces neuronal damage caused in vitro by excitotoxic stimuli and that this neuroprotection was associated with prevention of injury-induced engagement of critical death pathways. PMID:17401440

N-Methyl-d-aspartate Modulation of Nucleus Accumbens Dopamine Release by Metabotropic Glutamate Receptors: Fast Cyclic Voltammetry Studies in Rat Brain Slices in Vitro.

PubMed

Yavas, Ersin; Young, Andrew M J

2017-02-15

The N-methyl-d-aspartate (NMDA) receptor antagonist, phencyclidine, induces behavioral changes in rodents mimicking symptoms of schizophrenia, possibly mediated through dysregulation of glutamatergic control of mesolimbic dopamine release. We tested the hypothesis that NMDA receptor activation modulates accumbens dopamine release, and that phencyclidine pretreatment altered this modulation. NMDA caused a receptor-specific, dose-dependent decrease in electrically stimulated dopamine release in nucleus accumbens brain slices. This decrease was unaffected by picrotoxin, making it unlikely to be mediated through GABAergic neurones, but was decreased by the metabotropic glutamate receptor antagonist, (RS)-α-methyl-4-sulfonophenylglycine, indicating that NMDA activates mechanisms controlled by these receptors to decrease stimulated dopamine release. The effect of NMDA was unchanged by in vivo pretreatment with phencyclidine (twice daily for 5 days), with a washout period of at least 7 days before experimentation, which supports the hypothesis that there is no enduring direct effect of PCP at NMDA receptors after this pretreatment procedure. We propose that NMDA depression of accumbal dopamine release is mediated by metabotropic glutamate receptors located pre- or perisynaptically, and suggest that NMDA evoked increased extrasynaptic spillover of glutamate is sufficient to activate these receptors that, in turn, inhibit dopamine release. Furthermore, we suggest that enduring functional changes brought about by subchronic phencyclidine pretreatment, modeling deficits in schizophrenia, are downstream effects consequent on chronic blockade of NMDA receptors, rather than direct effects on NMDA receptors themselves.

Pre-synaptic glycine GlyT1 transporter--NMDA receptor interaction: relevance to NMDA autoreceptor activation in the presence of Mg2+ ions.

PubMed

Musante, Veronica; Summa, Maria; Cunha, Rodrigo A; Raiteri, Maurizio; Pittaluga, Anna

2011-05-01

Rat hippocampal glutamatergic terminals possess NMDA autoreceptors whose activation by low micromolar NMDA elicits glutamate exocytosis in the presence of physiological Mg(2+) (1.2 mM), the release of glutamate being significantly reduced when compared to that in Mg(2+)-free condition. Both glutamate and glycine were required to evoke glutamate exocytosis in 1.2 mM Mg(2+), while dizocilpine, cis-4-[phosphomethyl]-piperidine-2-carboxylic acid and 7-Cl-kynurenic acid prevented it, indicating that occupation of both agonist sites is needed for receptor activation. D-serine mimicked glycine but also inhibited the NMDA/glycine-induced release of [(3H]D-aspartate, thus behaving as a partial agonist. The NMDA/glycine-induced release in 1.2 mM Mg(2+) strictly depended on glycine uptake through the glycine transporter type 1 (GlyT1), because the GlyT1 blocker N-[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl])sarcosine hydrochloride, but not the GlyT2 blocker Org 25534, prevented it. Accordingly, [(3)H]glycine was taken up during superfusion, while lowering the external concentration of Na(+), the monovalent cation co-transported with glycine by GlyT1, abrogated the NMDA-induced effect. Western blot analysis of subsynaptic fractions confirms that GlyT1 and NMDA autoreceptors co-localize at the pre-synaptic level, where GluN3A subunits immunoreactivity was also recovered. It is proposed that GlyT1s coexist with NMDA autoreceptors on rat hippocampal glutamatergic terminals and that glycine taken up by GlyT1 may permit physiological activation of NMDA pre-synaptic autoreceptors. © 2011 The Authors. Journal of Neurochemistry © 2011 International Society for Neurochemistry.

Cellular prion protein protects from inflammatory and neuropathic pain

PubMed Central

2011-01-01

Cellular prion protein (PrPC) inhibits N-Methyl-D-Aspartate (NMDA) receptors. Since NMDA receptors play an important role in the transmission of pain signals in the dorsal horn of spinal cord, we thus wanted to determine if PrPC null mice show a reduced threshold for various pain behaviours. We compared nociceptive thresholds between wild type and PrPC null mice in models of inflammatory and neuropathic pain, in the presence and the absence of a NMDA receptor antagonist. 2-3 months old male PrPC null mice exhibited an MK-801 sensitive decrease in the paw withdrawal threshold in response both mechanical and thermal stimuli. PrPC null mice also exhibited significantly longer licking/biting time during both the first and second phases of formalin-induced inflammation of the paw, which was again prevented by treatment of the mice with MK-801, and responded more strongly to glutamate injection into the paw. Compared to wild type animals, PrPC null mice also exhibited a significantly greater nociceptive response (licking/biting) after intrathecal injection of NMDA. Sciatic nerve ligation resulted in MK-801 sensitive neuropathic pain in wild-type mice, but did not further augment the basal increase in pain behaviour observed in the null mice, suggesting that mice lacking PrPC may already be in a state of tonic central sensitization. Altogether, our data indicate that PrPC exerts a critical role in modulating nociceptive transmission at the spinal cord level, and fit with the concept of NMDA receptor hyperfunction in the absence of PrPC. PMID:21843375

D-Cycloserine Does Not Facilitate Fear Extinction by Reducing Conditioned Stimulus Processing or Promoting Conditioned Inhibition to Contextual Cues

ERIC Educational Resources Information Center

Baker, Kathryn D.; McNally, Gavan P.; Richardson, Rick

2012-01-01

The NMDA receptor partial agonist d-cycloserine (DCS) enhances the extinction of learned fear in rats and exposure therapy in humans with anxiety disorders. Despite these benefits, little is known about the mechanisms by which DCS promotes the loss of fear. The present study examined whether DCS augments extinction retention (1) through reductions…

NMDA-induced potentiation of mGluR5 is mediated by activation of protein phosphatase 2B/calcineurin

PubMed Central

Alagarsamy, Sudar; Saugstad, Julie; Warren, Lee; Mansuy, Isabelle M.; Gereau, Robert W.; Conn, P. Jeffrey

2010-01-01

Previous reports have shown that activation of N-methyl-D-aspartate (NMDA) receptors potentiates responses to activation of the group I metabotropic glutamate receptor mGluR5 by reversing PKC-mediated desensitization of this receptor. NMDA-induced reversal of mGluR5 desensitization is dependent on activation of protein phosphatases. However, the specific protein phosphatase involved and the precise mechanism by which NMDA receptor activation reduces mGluR desensitization are not known. We have performed a series of molecular, biochemical, and genetic studies to show that NMDA-induced regulation of mGluR5 is dependent on activation of calcium-dependent protein phosphatase 2B/calcineurin (PP2B/CaN). Furthermore, we report that purified calcineurin directly dephosphorylates the C-terminal tail of mGluR5 at sites that are phosphorylated by PKC. Finally, immunoprecipitation and GST fusion protein pull-down experiments reveal that calcineurin interacts with mGluR5, suggesting that these proteins could be colocalized in a signaling complex. Taken together with previous studies, these data suggest that activation of NMDA receptors leads to activation of calcineurin and that calcineurin modulates mGluR5 function by directly dephosphorylating mGluR5 at PKC sites that are involved in desensitization of this receptor. 2005 Elsevier Ltd. All rights reserved. PMID:16005030

Glutamate receptor activation in the kindled dentate gyrus.

PubMed

Behr, J; Heinemann, U; Mody, I

2000-01-01

The contribution of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), N-methyl-D-aspartate (NMDA), and kainate receptor activation to the enhanced seizure susceptibility of the dentate gyrus was investigated in an experimental model of temporal lobe epilepsy. Using the specific NMDA and AMPA receptor antagonists D-APV and SYM 2206, we examined alterations in glutamate receptor-dependent synaptic currents 48 hours and 28 days after kindling in field-potential and voltage-clamp recordings. Forty-eight hours after kindling, the fractions of AMPA and NMDA receptor-mediated excitatory postsynaptic current components shifted dramatically in favor of the NMDA receptor-mediated response. Four weeks after kindling, however, AMPA and NMDA receptor-mediated excitatory postsynaptic currents reverted to control-like values. Neither single nor repetitive perforant path stimuli evoked kainate receptor-mediated excitatory postsynaptic currents in dentate gyrus granule cells of control or kindled rats. The enhanced excitability of the kindled dentate gyrus 48 hours after the last seizure most likely results from transiently enhanced NMDA receptor activation. The NMDA receptor seems to play a critical role in the induction of the kindled state rather than in the persistence of the enhanced seizure susceptibility.

Adjunctive Treatment with Asenapine Augments the Escitalopram-Induced Effects on Monoaminergic Outflow and Glutamatergic Neurotransmission in the Medial Prefrontal Cortex of the Rat

PubMed Central

Björkholm, Carl; Frånberg, Olivia; Malmerfelt, Anna; Marcus, Monica M.; Konradsson-Geuken, Åsa; Schilström, Björn; Jardemark, Kent

2015-01-01

Background: Substantial clinical data support the addition of low doses of atypical antipsychotic drugs to selective serotonin reuptake inhibitors (SSRIs) to rapidly enhance the antidepressant effect in treatment-resistant depression. Preclinical studies suggest that this effect is at least partly explained by an increased catecholamine outflow in the medial prefrontal cortex (mPFC). Methods: In the present study we used in vivo microdialysis in freely moving rats and in vitro intracellular recordings of pyramidal cells of the rat mPFC to investigate the effects of adding the novel atypical antipsychotic drug asenapine to the SSRI escitalopram with regards to monoamine outflow in the mPFC and dopamine outflow in nucleus accumbens as well as glutamatergic transmission in the mPFC. Results: The present study shows that addition of low doses (0.05 and 0.1 mg/kg) of asenapine to escitalopram (5 mg/kg) markedly enhances dopamine, noradrenaline, and serotonin release in the rat mPFC as well as dopamine release in the nucleus accumbens. Moreover, this drug combination facilitated both N-methyl-d-Aspartate (NMDA)– and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)–induced currents as well as electrically evoked excitatory postsynaptic potentials in pyramidal cells of the rat mPFC. Conclusions: Our results support the notion that the augmentation of SSRIs by atypical antipsychotic drugs in treatment-resistant depression may, at least in part, be related to enhanced catecholamine output in the prefrontal cortex and that asenapine may be clinically used to achieve this end. In particular, the subsequent activation of the D1 receptor may be of importance for the augmented antidepressant effect, as this mechanism facilitated both NMDA and AMPA receptor-mediated transmission in the mPFC. Our novel observation that the drug combination, like ketamine, facilitates glutamatergic transmission in the mPFC may contribute to explain the rapid and potent antidepressant effect obtained when atypical antipsychotic drugs are added to SSRIs. PMID:25522408

NMDA receptor mediates proliferation and CREB phosphorylation in postnatal Müller glia-derived retinal progenitors

PubMed Central

Ramírez, Mónica

2009-01-01

Purpose Postnatal retinal Müller glia are considered to be retinal progenitors as they retain the ability to dedifferentiate, proliferate, and differentiate to new retinal glia and neurons after injury. The proliferation and differentiation processes are coordinated by several extrinsic factors and neurotransmitters, including glutamate. Thus, the appropriate numbers and proportions of the different cell types are generated to form a functional retina during development and during injury repair. Here we analyze the changes in the proliferation of postnatal Müller glia-derived progenitors after activation of the N-methyl-D-aspartate (NMDA) glutamate receptors. Methods Müller glia-derived progenitor cell cultures were characterized by immunocytochemistry with antibodies against the NR1 subunit of the NMDA receptor and the progenitor cell marker nestin. The effect of glutamate receptor agonists and antagonists on cell proliferation was analyzed by BrdU incorporation or Ki67 immunostaining, cell counting, and by immunolabeling of phosphorylated cAMP response element binding protein (P-CREB) transcription factor. The effect of NMDA receptor activation was analyzed in vivo by P-CREB immunohistochemistry in retinal sections of Long-Evans NMDA injected rats. Results We show that NMDA receptor activation significantly increases the proliferation rate of Müller-glia derived progenitor cells and that this increase can be blocked by NMDA receptor antagonists. Furthermore, we show that CREB phosphorylation is induced in NMDA-treated Müller-glia derived progenitor cells in culture and that specific pharmacological inhibition of CREB phosphorylation results in a decreased number of proliferating cells. We confirmed the relevance of these observations by the analysis of retinal sections after NMDA injection in vivo where immunoreactivity to phosphorylated CREB is also increased after treatment. Conclusions In the present study we show that NMDA receptor activation induces postnatal Müller glia-derived retinal cell progenitor proliferation and transcription factor CREB phosphorylation both in culture and in vivo. The identification of the molecular determinants of mature retinal progenitors such as transcription factor CREB and NMDA receptor-induced players should facilitate the control of growth and manipulation of progenitor cell cultures and the possible identification of the molecular mechanisms involved in progenitor self-renewal. PMID:19365572

Effects of Ginkgo biloba extracts on NMDA-activated currents in acutely isolated hippocampal neurons of the rat.

PubMed

Li, Shao; Luo, Jie; Wang, Xi; Guan, Bing-Cai; Sun, Chang-Kai

2011-01-01

Ginkgo biloba extracts (GBE) have long been used as a traditional herbal medicine for treating central nervous system diseases and peripheral vascular diseases, but the underlying mechanisms have yet to be elucidated. Furthermore, traditional GBE is in the form of microsomes and only dissolves in organic solvents; its clinical applications have been greatly limited. Therefore, in the present study, nanometer GBE (nGBE) was prepared utilizing supercritical anti-solvent (SAS) upon CO(2) -supercritical fluid extraction (CO(2) -SPF). Using whole-cell patch clamp techniques, the effects of different preparations of GBE on N-methyl-D-aspartate (NMDA)-activated currents (I(NMDA) ) from acutely isolated rat hippocampal neurons were investigated and the difference in protective potency between nGBE and mGBE evaluated. The results showed that the inward current activated by NMDA could be depressed by mGBE and nGBE. The inhibitory rates were 40% ± 17% and 64% ± 15%, and the half-inhibition concentrations (IC(50) ) were 0.0210 ± 0.0055 and 0.0262 ± 0.0038 mg/mL, respectively. In comparison, the modulatory effect of nGBE (dissolved in extracellular solution) on NMDA-activated current was significantly greater than that of mGBE (dissolved in DMSO) (p < 0.05). This indicated that the modulatory effects of GBE on NMDA-activated current may contribute to the neuroprotective effects of GBE and the modulatory effect of nGBE on NMDA-activated current was greater than that of mGBE. Copyright © 2010 John Wiley & Sons, Ltd.

Role of AMPA and NMDA receptors and back-propagating action potentials in spike timing-dependent plasticity.

PubMed

Fuenzalida, Marco; Fernández de Sevilla, David; Couve, Alejandro; Buño, Washington

2010-01-01

The cellular mechanisms that mediate spike timing-dependent plasticity (STDP) are largely unknown. We studied in vitro in CA1 pyramidal neurons the contribution of AMPA and N-methyl-d-aspartate (NMDA) components of Schaffer collateral (SC) excitatory postsynaptic potentials (EPSPs; EPSP(AMPA) and EPSP(NMDA)) and of the back-propagating action potential (BAP) to the long-term potentiation (LTP) induced by a STDP protocol that consisted in pairing an EPSP and a BAP. Transient blockade of EPSP(AMPA) with 7-nitro-2,3-dioxo-1,4-dihydroquinoxaline-6-carbonitrile (CNQX) during the STDP protocol prevented LTP. Contrastingly LTP was induced under transient inhibition of EPSP(AMPA) by combining SC stimulation, an imposed EPSP(AMPA)-like depolarization, and BAP or by coupling the EPSP(NMDA) evoked under sustained depolarization (approximately -40 mV) and BAP. In Mg(2+)-free solution EPSP(NMDA) and BAP also produced LTP. Suppression of EPSP(NMDA) or BAP always prevented LTP. Thus activation of NMDA receptors and BAPs are needed but not sufficient because AMPA receptor activation is also obligatory for STDP. However, a transient depolarization of another origin that unblocks NMDA receptors and a BAP may also trigger LTP.

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

Bidirectional modulation of windup by NMDA receptors in the rat spinal trigeminal nucleus.

PubMed

Woda, Alain; Blanc, Olivier; Voisin, Daniel L; Coste, Jérôme; Molat, Jean-Louis; Luccarini, Philippe

2004-04-01

Activation of afferent nociceptive pathways is subject to activity-dependent plasticity, which may manifest as windup, a progressive increase in the response of dorsal horn nociceptive neurons to repeated stimuli. At the cellular level, N-methyl-d-aspartate (NMDA) receptor activation by glutamate released from nociceptive C-afferent terminals is currently thought to generate windup. Most of the wide dynamic range nociceptive neurons that display windup, however, do not receive direct C-fibre input. It is thus unknown where the NMDA mechanisms for windup operate. Here, using the Sprague-Dawley rat trigeminal system as a model, we anatomically identify a subpopulation of interneurons that relay nociceptive information from the superficial dorsal horn where C-fibres terminate, to downstream wide dynamic range nociceptive neurons. Using in vivo electrophysiological recordings, we show that at the end of this pathway, windup was reduced (24 +/- 6%, n = 7) by the NMDA receptor antagonist AP-5 (2.0 fmol) and enhanced (62 +/- 19%, n = 12) by NMDA (1 nmol). In contrast, microinjections of AP-5 (1.0 fmol) within the superficial laminae increased windup (83 +/- 44%, n = 9), whereas NMDA dose dependently decreased windup (n = 19). These results indicate that NMDA receptor function at the segmental level depends on their precise location in nociceptive neural networks. While some NMDA receptors actually amplify pain information, the new evidence for NMDA dependent inhibition of windup we show here indicates that, simultaneously, others act in the opposite direction. Working together, the two mechanisms may provide a fine tuning of gain in pain.

Novel dimeric bis(7)-tacrine proton-dependently inhibits NMDA-activated currents

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

Luo, Jialie; Li, Wenming; Liu, Yuwei

2007-09-21

Bis(7)-tacrine has been shown to prevent glutamate-induced neuronal apoptosis by blocking NMDA receptors. However, the characteristics of the inhibition have not been fully elucidated. In this study, we further characterize the features of bis(7)-tacrine inhibition of NMDA-activated current in cultured rat hippocampal neurons. The results show that with the increase of extracellular pH, the inhibitory effect decreases dramatically. At pH 8.0, the concentration-response curve of bis(7)-tacrine is shifted rightwards with the IC{sub 50} value increased from 0.19 {+-} 0.03 {mu}M to 0.41 {+-} 0.04 {mu}M. In addition, bis(7)-tacrine shifts the proton inhibition curve rightwards. Furthermore, the inhibitory effect of bis(7)-tacrinemore » is not altered by the presence of the NMDA receptor proton sensor shield spermidine. These results indicate that bis(7)-tacrine inhibits NMDA-activated current in a pH-dependent manner by sensitizing NMDA receptors to proton inhibition, rendering it potentially beneficial therapeutic effects under acidic conditions associated with stroke and ischemia.« less

Glucocorticoid acts on a putative G protein-coupled receptor to rapidly regulate the activity of NMDA receptors in hippocampal neurons.

PubMed

Zhang, Yanmin; Sheng, Hui; Qi, Jinshun; Ma, Bei; Sun, Jihu; Li, Shaofeng; Ni, Xin

2012-04-01

Glucocorticoids (GCs) have been demonstrated to act through both genomic and nongenomic mechanisms. The present study demonstrated that corticosterone rapidly suppressed the activity of N-methyl-D-aspartate (NMDA) receptors in cultured hippocampal neurons. The effect was maintained with corticosterone conjugated to bovine serum albumin and blocked by inhibition of G protein activity with intracellular GDP-β-S application. Corticosterone increased GTP-bound G(s) protein and cyclic AMP (cAMP) production, activated phospholipase Cβ(3) (PLC-β(3)), and induced inositol-1,4,5-triphosphate (IP(3)) production. Blocking PLC and the downstream cascades with PLC inhibitor, IP(3) receptor antagonist, Ca(2+) chelator, and protein kinase C (PKC) inhibitors prevented the actions of corticosterone. Blocking adenylate cyclase (AC) and protein kinase A (PKA) caused a decrease in NMDA-evoked currents. Application of corticosterone partly reversed the inhibition of NMDA currents caused by blockage of AC and PKA. Intracerebroventricular administration of corticosterone significantly suppressed long-term potentiation (LTP) in the CA1 region of the hippocampus within 30 min in vivo, implicating the possibly physiological significance of rapid effects of GC on NMDA receptors. Taken together, our results indicate that GCs act on a putative G protein-coupled receptor to activate multiple signaling pathways in hippocampal neurons, and the rapid suppression of NMDA activity by GCs is dependent on PLC and downstream signaling.

Citrate Modulates the Regulation by Zn2+ of N-Methyl-D-Aspartate Receptor-Mediated Channel Current and Neurotransmitter Release

NASA Astrophysics Data System (ADS)

Westergaard, Niels; Banke, Tue; Wahl, Philip; Sonnewald, Ursula; Schousboe, Arne

1995-04-01

The effect of the two metal-ion chelators EDTA and citrate on the action of N-methyl-D-aspartate (NMDA) receptors was investigated by use of cultured mouse cerebellar granule neurons and Xenopus oocytes, respectively, to monitor either NMDA-evoked transmitter release or membrane currents. Transmitter release from the glutamatergic neurons was determined by superfusion of the cells after preloading with the glutamate analogue D-[^3H]aspartate. The oocytes were injected with mRNA isolated from mouse cerebellum and, after incubation to allow translation to occur, currents mediated by NMDA were recorded electrophysiologically by voltage clamp at a holding potential of -80 mV. It was found that citrate as well as EDTA could attenuate the inhibitory action of Zn2+ on NMDA receptor-mediated transmitter release from the neurons and membrane currents in the oocytes. These effects were specifically related to the NMDA receptor, since the NMDA receptor antagonist MK-801 abolished the action and no effects of Zn2+ and its chelators were observed when kainate was used to selectively activate non-NMDA receptors. Since it was additionally demonstrated that citrate (and EDTA) preferentially chelated Zn2+ rather than Ca2+, the present findings strongly suggest that endogenous citrate released specifically from astrocytes into the extracellular space in the brain may function as a modulator of NMDA receptor activity. This is yet another example of astrocytic influence on neuronal activity.

Dynamic Changes in Cytosolic ATP Levels in Cultured Glutamatergic Neurons During NMDA-Induced Synaptic Activity Supported by Glucose or Lactate.

PubMed

Lange, Sofie C; Winkler, Ulrike; Andresen, Lars; Byhrø, Mathilde; Waagepetersen, Helle S; Hirrlinger, Johannes; Bak, Lasse K

2015-12-01

We have previously shown that synaptic transmission fails in cultured neurons in the presence of lactate as the sole substrate. Thus, to test the hypothesis that the failure of synaptic transmission is a consequence of insufficient energy supply, ATP levels were monitored employing the ATP biosensor Ateam1.03YEMK. While inducing synaptic activity by subjecting cultured neurons to two 30 s pulses of NMDA (30 µM) with a 4 min interval, changes in relative ATP levels were measured in the presence of lactate (1 mM), glucose (2.5 mM) or the combination of the two. ATP levels reversibly declined following NMDA-induced neurotransmission activity, as indicated by a reversible 10-20 % decrease in the response of the biosensor. The responses were absent when the NMDA receptor antagonist memantine was present. In the presence of lactate alone, the ATP response dropped significantly more than in the presence of glucose following the 2nd pulse of NMDA (approx. 10 vs. 20 %). Further, cytosolic Ca(2+) homeostasis during NMDA-induced synaptic transmission is partially inhibited by verapamil indicating that voltage-gated Ca(2+) channels are activated. Lastly, we showed that cytosolic Ca(2+) homeostasis is supported equally well by both glucose and lactate, and that a pulse of NMDA causes accumulation of Ca(2+) in the mitochondrial matrix. In summary, we have shown that ATP homeostasis during neurotransmission activity in cultured neurons is supported by both glucose and lactate. However, ATP homeostasis seems to be negatively affected by the presence of lactate alone, suggesting that glucose is needed to support neuronal energy metabolism during activation.

Calcium responses to synaptically activated bursts of action potentials and their synapse-independent replay in cultured networks of hippocampal neurons.

PubMed

Bengtson, C Peter; Kaiser, Martin; Obermayer, Joshua; Bading, Hilmar

2013-07-01

Both synaptic N-methyl-d-aspartate (NMDA) receptors and voltage-operated calcium channels (VOCCs) have been shown to be critical for nuclear calcium signals associated with transcriptional responses to bursts of synaptic input. However the direct contribution to nuclear calcium signals from calcium influx through NMDA receptors and VOCCs has been obscured by their concurrent roles in action potential generation and synaptic transmission. Here we compare calcium responses to synaptically induced bursts of action potentials with identical bursts devoid of any synaptic contribution generated using the pre-recorded burst as the voltage clamp command input to replay the burst in the presence of blockers of action potentials or ionotropic glutamate receptors. Synapse independent replays of bursts produced nuclear calcium responses with amplitudes around 70% of their original synaptically generated signals and were abolished by the L-type VOCC blocker, verapamil. These results identify a major direct source of nuclear calcium from local L-type VOCCs whose activation is boosted by NMDA receptor dependent depolarization. The residual component of synaptically induced nuclear calcium signals which was both VOCC independent and NMDA receptor dependent showed delayed kinetics consistent with a more distal source such as synaptic NMDA receptors or internal stores. The dual requirement of NMDA receptors and L-type VOCCs for synaptic activity-induced nuclear calcium dependent transcriptional responses most likely reflects a direct somatic calcium influx from VOCCs whose activation is amplified by synaptic NMDA receptor-mediated depolarization and whose calcium signal is boosted by a delayed input from distal calcium sources mostly likely entry through NMDA receptors and release from internal stores. This article is part of a Special Issue entitled: 12th European Symposium on Calcium. Copyright © 2013 Elsevier B.V. All rights reserved.

Glutamatergic drugs for schizophrenia: a systematic review and meta-analysis.

PubMed

Tuominen, Harri J; Tiihonen, Jari; Wahlbeck, Kristian

2005-01-01

To evaluate the efficacy of glutamatergic drugs, acting agonistically on the N-methyl-D-aspartate (NMDA) or the non-NMDA receptors, in schizophrenia. All relevant randomized controlled trials of glutamatergic drugs for schizophrenia were obtained from the Cochrane Schizophrenia Group's Register of Trials without any language or year limitations. Trials were classified according to their methodological quality. For binary and continuous data, relative risks and weighted (WMD) or standardized mean differences (SMD) were calculated, respectively. Eighteen short-term trials with 343 randomized patients were included in the meta-analysis. In all of these trials, glycine, D-serine, D-cycloserine or ampakine CX516 was used to augment antipsychotics. NMDA receptor co-agonists glycine and D-serine are effective in reducing negative symptoms (N = 132, fixed effect model SMD = -0.66, 95% CI -1.02 to -0.29, p = 0.0004) of schizophrenia, the magnitude of the effect is moderate. D-Cycloserine, a partial agonist of NMDA receptors, is less effective towards negative symptoms (N = 119, fixed effect model SMD = -0.11, 95% CI -0.48 to 0.25, p = 0.6). Positive symptoms fail to respond to glutamatergic medication. Available derived data on cognitive functioning do not indicate a significant effect of glycine or D-serine (N = 80, random effect model WMD = -2.79, 95% CI -6.17 to 0.60, p = 0.11). In the current limited data set, a moderate amelioration of negative symptoms of schizophrenia was found, but no other statistically significant beneficial effects on symptoms of schizophrenia.

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.

Agmatine protects against cell damage induced by NMDA and glutamate in cultured hippocampal neurons

PubMed Central

Wang, Wei-Ping; Iyo, Abiye H.; Miguel-Hidalgo, Javier; Regunathan, Soundar; Zhu, Meng-Yang

2010-01-01

Agmatine is a polyamine and has been considered as a novel neurotransmitter or neuromodulator in the central nervous system. In the present study, the neuroprotective effect of agmatine against cell damage caused by N-methyl-d-aspartate (NMDA) and glutamate was investigated in cultured rat hippocampal neurons. Lactate dehydrogenase (LDH) activity assay, β-tubulin III immunocytochemical staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end-labeling (TUNEL) assay were conducted to detect cell damage. Exposure of 12-day neuronal cultures of rat hippocampus to NMDA or glutamate for 1 h caused a concentration-dependent neurotoxicity, as indicated by the significant increase in released LDH activities. Addition of 100 µM agmatine into media ablated the neurotoxicity induced by NMDA or glutamate, an effect also produced by the specific NMDA receptor antagonist dizocilpine hydrogen maleate (MK801). Arcaine, an analog of agmatine with similar structure as agmatine, fully prevented the NMDA- or glutamate-induced neuronal damage. Spermine and putrescine, the endogenous polyamine and metabolic products of agmatine without the guanidine moiety of agmatine, failed to show this effect, indicating a structural relevance for this neuroprotection. Immunocytochemical staining and TUNEL assay confirmed the findings in the LDH measurement. That is, agmatine and MK801 markedly attenuated NMDA-induced neuronal death and significantly reduced TUNEL-positive cell numbers induced by exposure of cultured hippocampal neurons to NMDA. Taken together, these results demonstrate that agmatine can protect cultured hippocampal neurons from NMDA- or glutamate-induced excitotoxicity, through a possible blockade of the NMDA receptor channels or a potential anti-apoptotic property. PMID:16546145

Hypothalamic nutrient sensing activates a forebrain-hindbrain neuronal circuit to regulate glucose production in vivo.

PubMed

Lam, Carol K L; Chari, Madhu; Rutter, Guy A; Lam, Tony K T

2011-01-01

Hypothalamic nutrient sensing regulates glucose production, but the neuronal circuits involved remain largely unknown. Recent studies underscore the importance of N-methyl-d-aspartate (NMDA) receptors in the dorsal vagal complex in glucose regulation. These studies raise the possibility that hypothalamic nutrient sensing activates a forebrain-hindbrain NMDA-dependent circuit to regulate glucose production. We implanted bilateral catheters targeting the mediobasal hypothalamus (MBH) (forebrain) and dorsal vagal complex (DVC) (hindbrain) and performed intravenous catheterizations to the same rat for infusion and sampling purposes. This model enabled concurrent selective activation of MBH nutrient sensing by either MBH delivery of lactate or an adenovirus expressing the dominant negative form of AMPK (Ad-DN AMPK α2 [D¹⁵⁷A]) and inhibition of DVC NMDA receptors by either DVC delivery of NMDA receptor blocker MK-801 or an adenovirus expressing the shRNA of NR1 subunit of NMDA receptors (Ad-shRNA NR1). Tracer-dilution methodology and the pancreatic euglycemic clamp technique were performed to assess changes in glucose kinetics in the same conscious, unrestrained rat in vivo. MBH lactate or Ad-DN AMPK with DVC saline increased glucose infusion required to maintain euglycemia due to an inhibition of glucose production during the clamps. However, DVC MK-801 negated the ability of MBH lactate or Ad-DN AMPK to increase glucose infusion or lower glucose production. Molecular knockdown of DVC NR1 of NMDA receptor via Ad-shRNA NR1 injection also negated MBH Ad-DN AMPK to lower glucose production. Molecular and pharmacological inhibition of DVC NMDA receptors negated hypothalamic nutrient sensing mechanisms activated by lactate metabolism or AMPK inhibition to lower glucose production. Thus, DVC NMDA receptor is required for hypothalamic nutrient sensing to lower glucose production and that hypothalamic nutrient sensing activates a forebrain-hindbrain circuit to lower glucose production.

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.

Design, Synthesis, and Structure–Activity Relationship of a Novel Series of GluN2C-Selective Potentiators

PubMed Central

2015-01-01

NMDA receptors are tetrameric complexes composed of GluN1 and GluN2A–D subunits that mediate a slow Ca2+-permeable component of excitatory synaptic transmission. NMDA receptors have been implicated in a wide range of neurological diseases and thus represent an important therapeutic target. We herein describe a novel series of pyrrolidinones that selectively potentiate only NMDA receptors that contain the GluN2C subunit. The most active analogues tested were over 100-fold selective for recombinant GluN2C-containing receptors over GluN2A/B/D-containing NMDA receptors as well as AMPA and kainate receptors. This series represents the first class of allosteric potentiators that are selective for diheteromeric GluN2C-containing NMDA receptors. PMID:24512267

Spinal N-methyl-D-aspartate receptors and nociception-evoked release of primary afferent substance P.

PubMed

Nazarian, A; Gu, G; Gracias, N G; Wilkinson, K; Hua, X Y; Vasko, M R; Yaksh, T L

2008-03-03

Dorsal horn N-methyl-D-aspartate (NMDA) receptors contribute significantly to spinal nociceptive processing through an effect postsynaptic to non-primary glutamatergic axons, and perhaps presynaptic to the primary afferent terminals. The present study sought to examine the regulatory effects of NMDA receptors on primary afferent release of substance P (SP), as measured by neurokinin 1 receptor (NK1r) internalization in the spinal dorsal horn of rats. The effects of intrathecal NMDA alone or in combination with D-serine (a glycine site agonist) were initially examined on basal levels of NK1r internalization. NMDA alone or when co-administered with D-serine failed to induce NK1r internalization, whereas activation of spinal TRPV1 receptors by capsaicin resulted in a notable NK1r internalization. To determine whether NMDA receptor activation could potentiate NK1r internalization or pain behavior induced by a peripheral noxious stimulus, intrathecal NMDA was given prior to an intraplantar injection of formalin. NMDA did not alter the formalin-induced NK1r internalization nor did it enhance the formalin paw flinching behavior. To further characterize the effects of presynaptic NMDA receptors, the NMDA antagonists DL-2-amino-5-phosphonopentanoic acid (AP-5) and MK-801 were intrathecally administered to assess their regulatory effects on formalin-induced NK1r internalization and pain behavior. AP-5 had no effect on formalin-induced NK1r internalization, whereas MK-801 produced only a modest reduction. Both antagonists, however, reduced the formalin paw flinching behavior. In subsequent in vitro experiments, perfusion of NMDA in spinal cord slice preparations did not evoke basal release of SP or calcitonin gene-related peptide (CGRP). Likewise, perfusion of NMDA did not enhance capsaicin-evoked release of the two peptides. These results suggest that presynaptic NMDA receptors in the spinal cord play little if any role on the primary afferent release of SP.

Anxiolytic-Like Effects and Increase in Locomotor Activity Induced by Infusions of NMDA into the Ventral Hippocampus in Rat: Interaction with GABAergic System.

PubMed

Bina, Payvand; Rezvanfard, Mehrnaz; Ahmadi, Shamseddin; Zarrindast, Mohammad Reza

2014-10-01

In this study, we investigated the role of N-Methyl-D-Aspartate (NMDA) receptors in the ventral hippocampus (VH) and their possible interactions with GABAA system on anxiety-like behaviors. We used an elevated-plus maze test (EPM) to assess anxiety-like behaviors and locomotor activity in male Wistar rats. The results showed that intra-VH infusions of different doses of NMDA (0.25 and 0.5 μg/rat) increased locomotor activity, and also induced anxiolytic-like behaviors, as revealed by a tendency to increase percentage of open arm time (%OAT), and a significant increase in percentage of open arm entries (%OAE). The results also showed that intra-VH infusions of muscimol (0.5 and 1 μg/rat) or bicuculline (0.5 and 1 μg/rat) did not significantly affect anxiety-like behaviors, but bicuculline at dose of 1 μg/rat increased locomotor activity. Intra-VH co-infusions of muscimol (0.5 μg/rat) along with low doses of NMDA (0.0625 and 0.125 μg/rat) showed a tendency to increase %OAT, %OAE and locomotor activity; however, no interaction was observed between the drugs. Interestingly, intra-VH co-infusions of bicuculline (0.5 μg/rat) along with effective doses of NMDA (0.25 and 0.5 μg/rat) decreased %OAT, %OAE and locomotor activity, and a significant interaction between two drugs was observed. It can be concluded that GABAergic system may mediate the anxiolytic-like effects and increase in locomotor activity induced by NMDA in the VH.

The effects of GABAA and NMDA receptors in the shell-accumbens on spatial memory of METH-treated rats.

PubMed

Heysieattalab, Soomaayeh; Naghdi, Nasser; Zarrindast, Mohammad-Reza; Haghparast, Abbas; Mehr, Shahram Ejtemaei; Khoshbouei, Habibeh

2016-03-01

Methamphetamine (METH) is a highly addictive and neurotoxic psychostimulant. Its use in humans is often associated with neurocognitive impairment and deficits in hippocampal plasticity. Striatal dopamine system is one of the main targets of METH. The dopamine neurons in the striatum directly or indirectly regulate the GABA and glutamatergic signaling in this region and thus their outputs. This is consistent with previous reports showing modification of neuronal activity in the striatum modulates the expression of hippocampal LTP and hippocampal-dependent memory tasks such as Morris water maze (MWM). Therefore, reversing or preventing METH-induced synaptic modifications via pharmacological manipulations of the shell-nucleus accumbens (shell-NAc) may introduce a viable therapeutic target to attenuate the METH-induced memory deficits. This study is designed to investigate the role of intra-shell NAc manipulation of GABAA and NMDA receptors and their interaction with METH on memory performance in MWM task. Pharmacological manipulations were performed in rats received METH or saline. We found systemic saline plus intra-shell NAc infusions of muscimol dose-dependently impaired performance, while bicuculline had no effect. Surprisingly, the intra-NAc infusions of 0.005μg/rat muscimol that has no effect on memory performance (ineffective dose) prevented METH-induced memory impairment. In the contrary, the intra-NAc infusions of bicuculline (0.2μg/rat) increased METH-induced memory impairment. However, pre-training intra-NAc infusions of D-AP5 dose-dependently impaired performance, while NMDA had no effect in rats received systemic saline (control group). The intra-NAc infusions with an ineffective dose of NMDA (0.1μg/rat) increased METH-induced memory impairment. Furthermore, intra-NAc infusions of D-AP5 with an ineffective dose (0.1μg/rat) prevented METH-induced memory impairment. Our result is consistent with the interpretation that METH-mediated learning deficit might be due to modification of hippocampus-VTA loop and that augmentation of GABAA receptor function in the shell-NAc may provide a new therapeutic target for alleviating METH-induced memory deficits. Copyright © 2015. Published by Elsevier Inc.

Convulsions induced by centrally administered NMDA in mice: effects of NMDA antagonists, benzodiazepines, minor tranquilizers and anticonvulsants.

PubMed Central

Moreau, J. L.; Pieri, L.; Prud'hon, B.

1989-01-01

1. Convulsions were induced reproducibly by intracerebroventricular injection of N-methyl-D-aspartic acid (NMDA) to conscious mice. 2. Competitive (carboxypiperazine-propylphosphonic acid, CPP; 2-amino-7-phosphonoheptanoic acid, AP7) and non-competitive (MK801; phencyclidine, PCP; thienylcyclohexylpiperidine, TCP; dextrorphan; dextromethorphan) NMDA antagonists prevented NMDA-induced convulsions. 3. Benzodiazepine receptor agonists and partial agonists (triazolam, diazepam, clonazepam, Ro 16-6028), classical anticonvulsants (diphenylhydantoin, phenobarbitone, sodium valproate) and meprobamate were also found to prevent NMDA-induced convulsions. 4. Flumazenil (a benzodiazepine receptor antagonist) and the GABA agonists THIP and muscimol (up to subtoxic doses) were without effect. 5. Flumazenil reversed the anticonvulsant action of diazepam, but not that of MK801. 6. Results obtained in this model differ somewhat from those described in a seizure model with systemic administration of NMDA. An explanation for this discrepancy is offered. 7. This model is a simple test for assessing the in vivo activity of NMDA antagonists and also expands the battery of chemically-induced seizure models for characterizing anticonvulsants not acting at NMDA receptors. PMID:2574061

BDNF released during neuropathic pain potentiates NMDA receptors in primary afferent terminals

PubMed Central

Chen, Wenling; Walwyn, Wendy; Ennes, Helena S.; Kim, Hyeyoung; McRoberts, James A.; Marvizón, Juan Carlos G.

2014-01-01

NMDA receptors in primary afferent terminals can contribute to hyperalgesia by increasing neurotransmitter release. In rats and mice, we found that the ability of intrathecal NMDA to induce neurokinin 1 receptor (NK1R) internalization (a measure of substance P release) required a previous injection of BDNF. Selective knock-down of NMDA receptors in primary afferents decreased NMDA-induced NK1R internalization, confirming the presynaptic location of these receptors. The effect of BDNF was mediated by tropomyosin-related kinase B (trkB) receptors and not p75 neurotrophin receptors (p75NTR), because it was not produced by proBDNF and was inhibited by the trkB antagonist ANA-12 but not by the p75NTR inhibitor TAT-Pep5. These effects are probably mediated through the truncated form of the trkB receptor as there is little expression of full-length trkB in dorsal root ganglion (DRG) neurons. Src family kinase inhibitors blocked the effect of BDNF, suggesting that trkB receptors promote the activation of these NMDA receptors by Src family kinase phosphorylation. Western blots of cultured DRG neurons revealed that BDNF increased Tyr1472 phosphorylation of the NR2B subunit of the NMDA receptor, known to have a potentiating effect. Patch-clamp recordings showed that BDNF, but not proBDNF, increased NMDA receptor currents in cultured DRG neurons. NMDA-induced NK1R internalization was also enabled in a neuropathic pain model or by activating dorsal horn microglia with lipopolysaccharide. These effects were decreased by a BDNF scavenger, a trkB receptor antagonist and an Src family kinase inhibitor, indicating that BDNF released by microglia potentiates NMDA receptors in primary afferents during neuropathic pain. PMID:24611998

Role of motor cortex NMDA receptors in learning-dependent synaptic plasticity of behaving mice

PubMed Central

Hasan, Mazahir T.; Hernández-González, Samuel; Dogbevia, Godwin; Treviño, Mario; Bertocchi, Ilaria; Gruart, Agnès; Delgado-García, José M.

2013-01-01

The primary motor cortex has an important role in the precise execution of learned motor responses. During motor learning, synaptic efficacy between sensory and primary motor cortical neurons is enhanced, possibly involving long-term potentiation and N-methyl-D-aspartate (NMDA)-specific glutamate receptor function. To investigate whether NMDA receptor in the primary motor cortex can act as a coincidence detector for activity-dependent changes in synaptic strength and associative learning, here we generate mice with deletion of the Grin1 gene, encoding the essential NMDA receptor subunit 1 (GluN1), specifically in the primary motor cortex. The loss of NMDA receptor function impairs primary motor cortex long-term potentiation in vivo. Importantly, it impairs the synaptic efficacy between the primary somatosensory and primary motor cortices and significantly reduces classically conditioned eyeblink responses. Furthermore, compared with wild-type littermates, mice lacking primary motor cortex show slower learning in Skinner-box tasks. Thus, primary motor cortex NMDA receptors are necessary for activity-dependent synaptic strengthening and associative learning. PMID:23978820

The Neuroprotective Effects of SIRT1 on NMDA-Induced Excitotoxicity

PubMed Central

Si, Peipei; Qin, Huaping; Yin, Litian

2017-01-01

Silent information regulator 1 (SIRT1), an NAD+-dependent deacetylase, is involved in the regulation of gene transcription, energy metabolism, and cellular aging and has become an important therapeutic target across a range of diseases. Recent research has demonstrated that SIRT1 possesses neuroprotective effects; however, it is unknown whether it protects neurons from NMDA-mediated neurotoxicity. In the present study, by activation of SIRT1 using resveratrol (RSV) in cultured cortical neurons or by overexpression of SIRT1 in SH-SY5Y cell, we aimed to evaluate the roles of SIRT1 in NMDA-induced excitotoxicity. Our results showed that RSV or overexpression of SIRT1 elicited inhibitory effects on NMDA-induced excitotoxicity including a decrease in cell viability, an increase in lactate dehydrogenase (LDH) release, and a decrease in the number of living cells as measured by CCK-8 assay, LDH test, and Calcein-AM and PI double staining. RSV or overexpression of SIRT1 significantly improved SIRT1 deacetylase activity in the excitotoxicity model. Further study suggests that overexpression of SIRT1 partly suppressed an NMDA-induced increase in p53 acetylation. These results indicate that SIRT1 activation by either RSV or overexpression of SIRT1 can exert neuroprotective effects partly by inhibiting p53 acetylation in NMDA-induced neurotoxicity. PMID:29081884

Design, synthesis, and evaluation of polyamine-memantine hybrids as NMDA channel blockers.

PubMed

Kumamoto, Takuya; Nakajima, Marie; Uga, Reina; Ihayazaka, Naoko; Kashihara, Haruna; Katakawa, Kazuaki; Ishikawa, Tsutomu; Saiki, Ryotaro; Nishimura, Kazuhiro; Igarashi, Kazuei

2018-02-01

N-Methyl-d-aspartate (NMDA) receptors have been implicated in learning and memory, and may also play a central role in various conditions leading to neuronal degradation. NMDA receptor antagonists could therefore be of therapeutic benefit for a number of neurological disorders. We have designed hybrid compounds of polyamines and memantine, both of which function as NMDA channel blockers. The triamine derivative with a guanidine moiety showed more potent antagonistic activity than memantine. Copyright © 2017 Elsevier Ltd. All rights reserved.

Role of Phosphatidylinositol-3 Kinase Pathway in NMDA Preconditioning: Different Mechanisms for Seizures and Hippocampal Neuronal Degeneration Induced by Quinolinic Acid.

PubMed

Constantino, Leandra C; Binder, Luisa B; Vandresen-Filho, Samuel; Viola, Giordano G; Ludka, Fabiana K; Lopes, Mark W; Leal, Rodrigo B; Tasca, Carla I

2018-04-20

N-methyl D-aspartate (NMDA) preconditioning is evoked by the administration of a subtoxic dose of NMDA and is protective against neuronal excitotoxicity. This effect may involve a diversity of targets and cell signaling cascades associated to neuroprotection. Phosphatidylinositol-3 kinase/protein kinase B (PI3K/Akt) and mitogen-activated protein kinases (MAPKs) such as extracellular regulated protein kinase 1/2 (ERK1/2) and p38 MAPK pathways play a major role in neuroprotective mechanisms. However, their involvement in NMDA preconditioning was not yet fully investigated. The present study aimed to evaluate the effect of NMDA preconditioning on PI3K/Akt, ERK1/2, and p38 MAPK pathways in the hippocampus of mice and characterize the involvement of PI3K on NMDA preconditioning-evoked prevention of seizures and hippocampal cell damage induced by quinolinic acid (QA). Thus, mice received wortmannin (a PI3K inhibitor) and 15 min later a subconvulsant dose of NMDA (preconditioning) or saline. After 24 h of this treatment, an intracerebroventricular QA infusion was administered. Phosphorylation levels and total content of Akt, glycogen synthase protein kinase-3β (GSK-3β), ERK1/2, and p38 MAPK were not altered after 24 h of NMDA preconditioning with or without wortmmanin pretreatment. Moreover, after QA administration, behavioral seizures, hippocampal neuronal degeneration, and Akt activation were evaluated. Inhibition of PI3K pathway was effective in abolishing the protective effect of NMDA preconditioning against QA-induced seizures, but did not modify neuronal protection promoted by preconditioning as evaluated by Fluoro-Jade B staining. The study confirms that PI3K participates in the mechanism of protection induced by NMDA preconditioning against QA-induced seizures. Conversely, NMDA preconditioning-evoked protection against neuronal degeneration is not altered by PI3K signaling pathway inhibition. These results point to differential mechanisms regarding protection against a behavioral and cellular manifestation of neural damage.

Activation of µ-opioid receptors and block of KIR3 potassium channels and NMDA receptor conductance by l- and d-methadone in rat locus coeruleus

PubMed Central

Matsui, Aya; Williams, John T

2010-01-01

BACKGROUND AND PURPOSE Methadone activates opioid receptors to increase a potassium conductance mediated by G-protein-coupled, inwardly rectifying, potassium (KIR3) channels. Methadone also blocks KIR3 channels and N-methyl-D-aspartic acid (NMDA) receptors. However, the concentration dependence and stereospecificity of receptor activation and channel blockade by methadone on single neurons has not been characterized. EXPERIMENTAL APPROACH Intracellular and whole-cell recording were made from locus coeruleus neurons in brain slices and the activation of µ-opioid receptors and blockade of KIR3 and NMDA channels with l- and d-methadone was examined. KEY RESULTS The potency of l-methadone, measured by the amplitude of hyperpolarization was 16.5-fold higher than with d-methadone. A maximum hyperpolarization was caused by both enantiomers (∼30 mV); however, the maximum outward current measured with whole-cell voltage-clamp recording was smaller than the current induced by [Met]5enkephalin. The KIR3 conductance induced by activation of α2-adrenoceptors was decreased with high concentrations of l- and d-methadone (10–30 µM). In addition, methadone blocked the resting inward rectifying conductance (KIR). Both l- and d-methadone blocked the NMDA receptor-dependent current. The block of NMDA receptor-dependent current was voltage-dependent suggesting that methadone acted as a channel blocker. CONCLUSIONS AND IMPLICATIONS Methadone activated µ-opioid receptors at low concentrations in a stereospecific manner. KIR3 and NMDA receptor channel block was not stereospecific and required substantially higher concentrations. The separation in the concentration range suggests that the activation of µ-opioid receptors rather than the channel blocking properties mediate both the therapeutic and toxic actions of methadone. PMID:20659105

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.

Angiotensin II attenuates NMDA receptor-mediated neuronal cell death and prevents the associated reduction in Bcl-2 expression.

PubMed

Schelman, William R; Andres, Robert; Ferguson, Paul; Orr, Brent; Kang, Evan; Weyhenmeyer, James A

2004-09-10

While angiotensin II (Ang II) plays a major role in the regulation of blood pressure, fluid homeostasis and neuroendocrine function, recent studies have also implicated the peptide hormone in cell growth, differentiation and apoptosis. In support of this, we have previously demonstrated that Ang II attenuates N-methyl-D-aspartate (NMDA) receptor signaling [Molec. Brain Res. 48 (1997) 197]. To further examine the modulatory role of Ang II on NMDA receptor function, we investigated the effect of angiotensin receptor (AT) activation on NMDA-mediated cell death and the accompanying decrease in Bcl-2 expression. The viability of differentiated N1E-115 and NG108-15 neuronal cell lines was reduced following exposure to NMDA in a dose-dependent manner. MTT analysis (mitochondrial integrity) revealed a decrease in cell survival of 49.4+/-12.3% in NG108 cells and 79.9+/-6.8% in N1E cells following treatment with 10 mM NMDA for 20 h. Cytotoxicity in N1E cells was inhibited by the noncompetitive NMDA receptor antagonist, MK-801. Further, NMDA receptor-mediated cell death in NG108 cells was attenuated by treatment with Ang II. The Ang II effect was inhibited by both AT1 and AT2 receptor antagonists, losartan and PD123319, respectively, suggesting that both receptor subtypes may play a role in the survival effect of Ang II. Since it has been shown that activation of NMDA receptors alters the expression of Bcl-2 family proteins, Western blot analysis was performed in N1E cells to determine whether Ang II alters the NMDA-induced changes in Bcl-2 expression. A concentration-dependent decrease of intracellular Bcl-2 protein levels was observed following treatment with NMDA, and this reduction was inhibited by MK801. Addition of Ang II suppressed the NMDA receptor-mediated reduction in Bcl-2. The Ang II effect on NMDA-mediated changes in Bcl-2 levels was blocked by PD123319, but was not significantly changed by losartan, suggesting AT2 receptor specificity. Taken together, these results suggest that Ang II attenuates NMDA receptor-mediated neurotoxicity and that this effect may be due, in part, to an alteration in Bcl-2 expression.

Tryptophanol-derived oxazolopiperidone lactams: identification of a hit compound as NMDA receptor antagonist.

PubMed

Pereira, Nuno A L; Sureda, Francesc X; Esplugas, Roser; Pérez, Maria; Amat, Mercedes; Santos, Maria M M

2014-08-01

N-Methyl-D-aspartate receptors (NMDAR) exacerbated activation leads to neuron death through a phenomenon called excitotoxicity. These receptors are implicated in several neurological diseases (e.g., Alzheimer and Parkinson) and thus represent an important therapeutic target. We herein describe the study of enantiopure tryptophanol-derived oxazolopiperidone lactams as NMDA receptor antagonists. The most active hit exhibited an IC50 of 63.4 μM in cultured rat cerebellar granule neurons thus being 1.5 fold more active than clinically approved NMDA antagonist amantadine (IC50=92 μM). Copyright © 2014 Elsevier Ltd. All rights reserved.

Subunit Arrangement and Phenylethanolamine Binding in GluN1/GluN2B NMDA Receptors

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

E Karakas; N Simorowski; H Furukawa

2011-12-31

Since it was discovered that the anti-hypertensive agent ifenprodil has neuroprotective activity through its effects on NMDA (N-methyl-D-aspartate) receptors, a determined effort has been made to understand the mechanism of action and to develop improved therapeutic compounds on the basis of this knowledge. Neurotransmission mediated by NMDA receptors.

Activation of the ζ receptor 1 suppresses NMDA responses in rat retinal ganglion cells.

PubMed

Zhang, X-J; Liu, L-L; Jiang, S-X; Zhong, Y-M; Yang, X-L

2011-03-17

The sigma receptor 1 (σR1) has been shown to modulate the activity of several voltage- and ligand-gated channels. Using patch-clamp techniques in rat retinal slice preparations, we demonstrated that activation of σR1 by SKF10047 (SKF) or PRE-084 suppressed N-methyl-D-aspartate (NMDA) receptor-mediated current responses from both ON and OFF type ganglion cells (GCs), dose-dependently, and the effect could be blocked by the σR1 antagonist BD1047 or the σR antagonist haloperidol. The suppression by SKF of NMDA currents was abolished with pre-incubation of the G protein inhibitor GDP-β-S or the Gi/o activator mastoparan. We further explored the intracellular signaling pathway responsible for the SKF-induced suppression of NMDA responses. Application of either cAMP/the PKA inhibitor Rp-cAMP or cGMP/the PKG inhibitor KT5823 did not change the SKF-induced effect, suggesting the involvement of neither cAMP/PKA nor cGMP/PKG pathway. In contrast, suppression of NMDA responses by SKF was abolished by internal infusion of the phosphatidylinostiol-specific phospholipase C (PLC) inhibitor U73122, but not by the phosphatidylcholine-PLC inhibitor D609. SKF-induced suppression of NMDA responses was dependent on intracellular Ca2+ concentration ([Ca2+]i), as evidenced by the fact that the effect was abolished when [Ca2+]i was buffered with 10 mM BAPTA. The SKF effect was blocked by xestospongin-C/heparin, IP3 receptor antagonists, but unchanged by ryanodine/caffeine, ryanodine receptor modulators. Furthermore, application of protein kinase C inhibitors Bis IV and Gö6976 eliminated the SKF effect. These results suggest that the suppression of NMDA responses of rat retinal GCs caused by the activation of σR1 may be mediated by a distinct [Ca2+]i-dependent PLC-PKC pathway. This effect of SKF could help ameliorate malfunction of GCs caused by excessive stimulation of NMDA receptors under pathological conditions. Copyright © 2011 IBRO. Published by Elsevier Ltd. All rights reserved.

Study of the n-methyl-d-aspartate antagonistic properties of anticholinergic drugs

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

McDonough, J.H.; Shih, T.M.

1995-12-31

A study of the N-methyl-D-aspartate antagonistic properties of anticholinergic drugs. PHARMACOL BIOCHEM BEHAV. 51(2/3) 249-253, 1995. Drugs that act at the N-methyl-D-aspartate (NMDA) receptor complex have the ability to terminate nerve agent-induced seizures and modulate the neuropathologic consequences of agent exposure. Drugs with mixed anticholinergic and anti-NMDA properties potentially provide an ideal class of compounds for development as anticonvulsant treatments for nerve agent casualties. The present experiment evaluated the potential NMDA antagonist activity of 11 anticholinergic drugs by determining whether pretreatment with the compound was capable of protecting mice from the lethal effects of NMDA. The following anticholinergic drugs antagonizedmore » NMDA lethality and are ranked according to their potency: mecamylamine > procyclidine = benactyzine > biperiden > tribexyphenidyl. The anticholinergics atropine, aprophen, azaprophen, benztropine, 3-quinudidinyl benzilate (QNB), and scopolamine failed to show NMDA antagonist properties. In addition, and unexpectedly, diazepam, ethanol, and pentobarbital were also shown to be capable of antagonizing NMDA lethality over a certain range of doses. The advantages and limitations of using antagonism of NMDA lethality in mice as a bioassay for determining the NMDA antagonist properties of drugs are also discussed.« less

Gene regulation by NMDA receptor activation in the SDN-POA neurons of male rats during sexual development.

PubMed

Hsu, Hseng-Kuang; Shao, Pei-Lin; Tsai, Ke-Li; Shih, Huei-Chuan; Lee, Tzu-Ying; Hsu, Chin

2005-04-01

The present study was designed to identify possible signaling pathways, which may play a role in prevention of neuronal apoptosis in the sexually dimorphic nucleus of the preoptic area (SDN-POA) after physiological activation of the N-methyl-D-aspartate (NMDA) receptor. Gene response to the blockage of the NMDA receptor by an antagonist (dizocilpine hydrogen maleate; MK-801) was screened after suppression subtractive hybridization (SSH). The results showed that differential screening after SSH detected the presence of some neurotrophic genes (RNA binding motif protein 3 (RBM3), alpha-tubulin) as well as apoptosis-related genes (Bcl-2, cytochrome oxidase subunit II, cytochrome oxidase subunit III) in the SDN-POA of male rats, which were down-regulated by blocking the NMDA receptor. The RT-PCR products of the aforementioned genes in MK-801-treated males were significantly less than that in untreated males. In particular, the expression of Bcl-2 mRNA, including Bcl-2 protein, in male rats were significantly suppressed by MK-801 treatment. Moreover, the binding activity of nuclear factor kappaB (NFkappaB) was significantly higher in male rats than in females, but significantly diminished by blocking the NMDA receptor with MK-801 in male rats. No significant difference in cAMP response element-binding protein (CREB) binding activity was observed among untreated male, MK-801-treated male, untreated female and MK-801-treated female groups. These results suggest that genes regulated by NMDA receptor activation might participate in neuronal growth and/or anti-apoptosis, and support an important signaling pathway of NFkappaB activation and its target gene, Bcl-2, in preventing neuronal apoptosis in the SDN-POA of male rats during sexual development.

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.

Tandospirone, a 5-HT1A partial agonist, ameliorates aberrant lactate production in the prefrontal cortex of rats exposed to blockade of N-methy-D-aspartate receptors; Toward the therapeutics of cognitive impairment of schizophrenia.

PubMed

Uehara, Takashi; Matsuoka, Tadasu; Sumiyoshi, Tomiki

2014-01-01

Augmentation therapy with serotonin-1A (5-HT1A) receptor partial agonists has been suggested to improve cognitive impairment in patients with schizophrenia. Decreased activity of prefrontal cortex may provide a basis for cognitive deficits of the disease. Lactate plays a significant role in the supply of energy to the brain, and glutamatergic neurotransmission contributes to lactate production. The purposes of this study were to examine the effect of repeated administration (once a daily for 4 days) of tandospirone (0.05 or 5 mg/kg) on brain energy metabolism, as represented by extracellular lactate concentration (eLAC) in the medial prefrontal cortex (mPFC) of a rat model of schizophrenia. Four-day treatment with MK-801, an NMDA-R antagonist, prolonged eLAC elevation induced by foot-shock stress (FS). Co-administration with the high-dose tandospirone suppressed prolonged FS-induced eLAC elevation in rats receiving MK-801, whereas tandospirone by itself did not affected eLAC increment. These results suggest that stimulation of 5-HT1A receptors ameliorates abnormalities of energy metabolism in the mPFC due to blockade of NMDA receptors. These findings provide a possible mechanism, based on brain energy metabolism, by which 5-HT1A agonism improve cognitive impairment of schizophrenia and related disorders.

Inhibition of N-methyl-D-aspartate receptors increases paraoxon-induced apoptosis in cultured neurons

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

Wu Xuan; Tian Feng; Okagaki, Peter

2005-10-01

Organophosphorus (OP) compounds, used as insecticides and chemical warfare agents, are potent neurotoxins. We examined the neurotoxic effect of paraoxon (O,O-diethyl O-p-nitrophenyl phosphate), an organophosphate compound, and the role of NMDA receptors as a mechanism of action in cultured cerebellar granule cells. Paraoxon is neurotoxic to cultured rat cerebellar granule cells in a time- and concentration-dependent manner. Cerebellar granule cells are less sensitive to the neurotoxic effects of paraoxon on day in vitro (DIV) 4 than neurons treated on DIV 8. Surprisingly, the N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801, enhances paraoxon-mediated neurotoxicity suggesting that NMDA receptors may play a protective role.more » Pretreatment with a subtoxic concentration of N-methyl-D-aspartate (NMDA) [100 {mu}M] protects about 40% of the vulnerable neurons that would otherwise die from paraoxon-induced neurotoxicity. Moreover, addition of a neuroprotective concentration of NMDA 3 h after treatment with paraoxon provides the same level of protection. Because paraoxon-mediated neuronal cell death is time-dependent, we hypothesized that apoptosis may be involved. Paraoxon increases apoptosis about 10-fold compared to basal levels. The broad-spectrum caspase inhibitor (Boc-D-FMK) and the caspase-9-specific inhibitor (Z-LEHD-FMK) protect against paraoxon-mediated apoptosis, paraoxon-stimulated caspase-3 activity and neuronal cell death. MK-801 increases, whereas NMDA blocks paraoxon-induced apoptosis and paraoxon-stimulated caspase-3 activity. These results suggest that activation of NMDA receptors protect neurons against paraoxon-induced neurotoxicity by blocking apoptosis initiated by paraoxon.« less

Investigating dynamic structural and mechanical changes of neuroblastoma cells associated with glutamate-mediated neurodegeneration

NASA Astrophysics Data System (ADS)

Fang, Yuqiang; Iu, Catherine Y. Y.; Lui, Cathy N. P.; Zou, Yukai; Fung, Carmen K. M.; Li, Hung Wing; Xi, Ning; Yung, Ken K. L.; Lai, King W. C.

2014-11-01

Glutamate-mediated neurodegeneration resulting from excessive activation of glutamate receptors is recognized as one of the major causes of various neurological disorders such as Alzheimer's and Huntington's diseases. However, the underlying mechanisms in the neurodegenerative process remain unidentified. Here, we investigate the real-time dynamic structural and mechanical changes associated with the neurodegeneration induced by the activation of N-methyl-D-aspartate (NMDA) receptors (a subtype of glutamate receptors) at the nanoscale. Atomic force microscopy (AFM) is employed to measure the three-dimensional (3-D) topography and mechanical properties of live SH-SY5Y cells under stimulus of NMDA receptors. A significant increase in surface roughness and stiffness of the cell is observed after NMDA treatment, which indicates the time-dependent neuronal cell behavior under NMDA-mediated neurodegeneration. The present AFM based study further advance our understanding of the neurodegenerative process to elucidate the pathways and mechanisms that govern NMDA induced neurodegeneration, so as to facilitate the development of novel therapeutic strategies for neurodegenerative diseases.

Non-NMDA receptor antagonist-induced drinking in rat

NASA Technical Reports Server (NTRS)

Xu, Z.; Johnson, A. K.

1998-01-01

Glutamate has been implicated in the central control of mechanisms that maintain body fluid homeostasis. The present studies demonstrate that intracerebroventricular (i.c.v.) injections of the non-N-methyl-d-aspartate (NMDA) receptor antagonists 6, 7-dinitroquinoxaline-2,3-dione (DNQX) and 6-cyano-7-nitroquinoxaline-2,3 dione (CNQX) induce drinking in rats. The dipsogenic effect of i.c.v. DNQX was antagonized by the non-NMDA receptor agonist alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA). The water intake induced by DNQX was also blocked by pretreatment with a NMDA receptor antagonist, MK-801, but not by angiotensin type 1 (AT1) or acetylcholine muscarinic receptor antagonists (losartan and atropine). The results indicate that non-NMDA receptors may exert a tonic inhibitory effect within brain circuits that control dipsogenic activity and that functional integrity of NMDA receptors may be required for the non-NMDA receptor antagonists to induce water intake. Copyright 1998 Published by Elsevier Science B.V.

Oxotremorine-M potentiates NMDA receptors by muscarinic receptor dependent and independent mechanisms.

PubMed

Zwart, Ruud; Reed, Hannah; Sher, Emanuele

2018-01-01

Muscarinic acetylcholine M1 receptors play an important role in synaptic plasticity in the hippocampus and cortex. Potentiation of NMDA receptors as a consequence of muscarinic acetylcholine M1 receptor activation is a crucial event mediating the cholinergic modulation of synaptic plasticity, which is a cellular mechanism for learning and memory. In Alzheimer's disease, the cholinergic input to the hippocampus and cortex is severely degenerated, and agonists or positive allosteric modulators of M1 receptors are therefore thought to be of potential use to treat the deficits in cognitive functions in Alzheimer's disease. In this study we developed a simple system in which muscarinic modulation of NMDA receptors can be studied in vitro. Human M1 receptors and NR1/2B NMDA receptors were co-expressed in Xenopus oocytes and various muscarinic agonists were assessed for their modulatory effects on NMDA receptor-mediated responses. As expected, NMDA receptor-mediated responses were potentiated by oxotremorine-M, oxotremorine or xanomeline when the drugs were applied between subsequent NMDA responses, an effect which was fully blocked by the muscarinic receptor antagonist atropine. However, in oocytes expressing NR1/2B NMDA receptors but not muscarinic M1 receptors, oxotremorine-M co-applied with NMDA also resulted in a potentiation of NMDA currents and this effect was not blocked by atropine, demonstrating that oxotremorine-M is able to directly potentiate NMDA receptors. Oxotremorine, which is a close analogue of oxotremorine-M, and xanomeline, a chemically distinct muscarinic agonist, did not potentiate NMDA receptors by this direct mechanism. Comparing the chemical structures of the three different muscarinic agonists used in this study suggests that the tri-methyl ammonium moiety present in oxotremorine-M is important for the compound's interaction with NMDA receptors. Copyright © 2017 Elsevier Inc. All rights reserved.

Metabotropic glutamate receptor 5 responses dictate differentiation of neural progenitors to NMDA-responsive cells in fragile X syndrome.

PubMed

Achuta, Venkat Swaroop; Grym, Heli; Putkonen, Noora; Louhivuori, Verna; Kärkkäinen, Virve; Koistinaho, Jari; Roybon, Laurent; Castrén, Maija L

2017-04-01

Disrupted metabotropic glutamate receptor 5 (mGluR5) signaling is implicated in many neuropsychiatric disorders, including autism spectrum disorder, found in fragile X syndrome (FXS). Here we report that intracellular calcium responses to the group I mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG) are augmented, and calcium-dependent mGluR5-mediated mechanisms alter the differentiation of neural progenitors in neurospheres derived from human induced pluripotent FXS stem cells and the brains of mouse model of FXS. Treatment with the mGluR5 antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) prevents an abnormal clustering of DHPG-responsive cells that are responsive to activation of ionotropic receptors in mouse FXS neurospheres. MPEP also corrects morphological defects of differentiated cells and enhanced migration of neuron-like cells in mouse FXS neurospheres. Unlike in mouse neurospheres, MPEP increases the differentiation of DHPG-responsive radial glial cells as well as the subpopulation of cells responsive to both DHPG and activation of ionotropic receptors in human neurospheres. However, MPEP normalizes the FXS-specific increase in the differentiation of cells responsive only to N-methyl-d-aspartate (NMDA) present in human neurospheres. Exposure to MPEP prevents the accumulation of intermediate basal progenitors in embryonic FXS mouse brain suggesting that rescue effects of GluR5 antagonist are progenitor type-dependent and species-specific differences of basal progenitors may modify effects of MPEP on the cortical development. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 419-437, 2017. © 2016 Wiley Periodicals, Inc.

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

Mitochondrial dysfunction and lipid peroxidation in rat frontal cortex by chronic NMDA administration can be partially prevented by lithium treatment.

PubMed

Kim, Helena K; Isaacs-Trepanier, Cameron; Elmi, Nika; Rapoport, Stanley I; Andreazza, Ana C

2016-05-01

Chronic N-methyl-d-aspartate (NMDA) administration to rats may be a model to investigate excitotoxicity mediated by glutamatergic hyperactivity, and lithium has been reported to be neuroprotective. We hypothesized that glutamatergic hyperactivity in chronic NMDA injected rats would cause mitochondrial dysfunction and lipid peroxidation in the brain, and that chronic lithium treatment would ameliorate some of these NMDA-induced alterations. Rats treated with lithium for 6 weeks were injected i.p. 25 mg/kg NMDA on a daily basis for the last 21 days of lithium treatment. Brain was removed and frontal cortex was analyzed. Chronic NMDA decreased brain levels of mitochondrial complex I and III, and increased levels of the lipid oxidation products, 8-isoprostane and 4-hydroxynonenal, compared with non-NMDA injected rats. Lithium treatment prevented the NMDA-induced increments in 8-isoprostane and 4-hydroxynonenal. Our findings suggest that increased chronic activation of NMDA receptors can induce alterations in electron transport chain complexes I and III and in lipid peroxidation in brain. The NMDA-induced changes may contribute to glutamate-mediated excitotoxicity, which plays a role in brain diseases such as bipolar disorder. Lithium treatment prevented changes in 8-isoprostane and 4-hydroxynonenal, which may contribute to lithium's reported neuroprotective effect and efficacy in bipolar disorder. Copyright © 2016 Elsevier Ltd. All rights reserved.

Protective effect of methanol extract of Uncaria rhynchophylla against excitotoxicity induced by N-methyl-D-aspartate in rat hippocampus.

PubMed

Lee, Jongseok; Son, Dongwook; Lee, Pyeongjae; Kim, Dae-Keun; Shin, Min-Chul; Jang, Mi-Hyeon; Kim, Chang-Ju; Kim, Yong-Sik; Kim, Sun-Yeou; Kim, Hocheol

2003-05-01

Uncaria rhynchophylla is a medicinal herb used for convulsive disorders in Oriental medicine. In this study, the effect of the methanol extract of Uncaria rhynchophylla against N-methyl-D-aspartate (NMDA)-induced excitotoxicity was investigated. Pretreatment with the extract of Uncaria rhynchopylla reduced the degree of neuronal damage induced by NMDA exposure in cultured hippocampal slices. In the patch clamp study, Uncaria rhynchophylla significantly inhibited NMDA receptor-activated ion current in acutely dissociated hippocampal CA1 neurons. These results indicate that Uncaria rhynchophylla offers protection against NMDA-induced neuronal injury and inhibitory action on NMDA receptor-mediated ion current may be a mechanism behind the neuroprotective effect of Uncaria rhynchophylla.

Ethanol Inhibition of Recombinant NMDA Receptors Is Not Altered by Co-Expression of CaMKII-α or CaMKII-β

PubMed Central

Xu, Minfu; Chandler, L. Judson; Woodward, John J.

2008-01-01

Previous studies have shown that the N-methyl-D-aspartate (NMDA) receptor is an important target for the actions of ethanol in the brain. NMDA receptors are glutamate-activated ion channels that are highly expressed in neurons. They are activated during periods of significant glutamatergic synaptic activity and are an important source of the signaling molecule calcium in the post-synaptic spine. Alterations in the function of NMDA receptors by drugs or disease are associated with deficits in motor, sensory and cognitive processes of the brain. Acutely, ethanol inhibits ion flow through NMDA receptors while sustained exposure to ethanol can induce compensatory changes in the density and localization of the receptor. Defining factors that govern the acute ethanol sensitivity of NMDA receptors is an important step in how an individual responds to ethanol. In the present study, we investigated the effect of calcium-calmodulin dependent protein kinase II (CaMKII) on the ethanol sensitivity of recombinant NMDA receptors. CaMKII is a major constituent of the post-synaptic density and is critically involved in various forms of learning and memory. NMDA receptor subunits were transiently expressed in human embryonic kidney 293 cells (HEK 293) along with CaMKII-α or CaMKII-β tagged with the green fluorescent protein (GFP). Whole cell currents were elicited by brief exposures to glutamate and were measured using patchclamp electrophysiology. Neither CaMKII-α or CaMKII-β had any significant effect on the ethanol inhibition of NR1/2A or NR1/2B receptors. Ethanol inhibition was also unaltered by deletion of CaMKII binding domains in NR1 or NR2 subunits or by phospho-site mutants that mimic or occlude CaMKII phosphorylation. Chronic treatment of cortical neurons with ethanol had no significant effect on the expression of CaMKII-α or CaMKII-β. The results of this study suggest that CaMKII is not involved in regulating the acute ethanol sensitivity of NMDA receptors. PMID:18562151

Synaptic GluN2A and GluN2B Containing NMDA Receptors within the Superficial Dorsal Horn Activated following Primary Afferent Stimulation

PubMed Central

MacDermott, Amy B.

2014-01-01

NMDA receptors are important elements in pain signaling in the spinal cord dorsal horn. They are heterotetramers, typically composed of two GluN1 and two of four GluN2 subunits: GluN2A-2D. Mice lacking some of the GluN2 subunits show deficits in pain transmission yet functional synaptic localization of these receptor subtypes in the dorsal horn has not been fully resolved. In this study, we have investigated the composition of synaptic NMDA receptors expressed in monosynaptic and polysynaptic pathways from peripheral sensory fibers to lamina I neurons in rats. We focused on substance P receptor-expressing (NK1R+) projection neurons, critical for expression of hyperalgesia and allodynia. EAB-318 and (R)-CPP, GluN2A/B antagonists, blocked both monosynaptic and polysynaptic NMDA EPSCs initiated by primary afferent activation by ∼90%. Physiological measurements exploiting the voltage dependence of monosynaptic EPSCs similarly indicated dominant expression of GluN2A/B types of synaptic NMDA receptors. In addition, at synapses between C fibers and NK1R+ neurons, NMDA receptor activation initiated a secondary, depolarizing current. Ifenprodil, a GluN2B antagonist, caused modest suppression of monosynaptic NMDA EPSC amplitudes, but had a widely variable, sometimes powerful, effect on polysynaptic responses following primary afferent stimulation when inhibitory inputs were blocked to mimic neuropathic pain. We conclude that GluN2B subunits are moderately expressed at primary afferent synapses on lamina I NK1R+ neurons, but play more important roles for polysynaptic NMDA EPSCs driven by primary afferents following disinhibition, supporting the view that the analgesic effect of the GluN2B antagonist on neuropathic pain is at least in part, within the spinal cord. PMID:25122884

Genetic Demonstration of a Role for Stathmin in Adult Hippocampal Neurogenesis, Spinogenesis, and NMDA Receptor-Dependent Memory

PubMed Central

Martel, Guillaume; Uchida, Shusaku; Hevi, Charles; Chévere-Torres, Itzamarie; Fuentes, Ileana; Park, Young Jin; Hafeez, Hannah; Yamagata, Hirotaka; Watanabe, Yoshifumi

2016-01-01

Neurogenesis and memory formation are essential features of the dentate gyrus (DG) area of the hippocampus, but to what extent the mechanisms responsible for both processes overlap remains poorly understood. Stathmin protein, whose tubulin-binding and microtubule-destabilizing activity is negatively regulated by its phosphorylation, is prominently expressed in the DG. We show here that stathmin is involved in neurogenesis, spinogenesis, and memory formation in the DG. tTA/tetO-regulated bitransgenic mice, expressing the unphosphorylatable constitutively active Stathmin4A mutant (Stat4A), exhibit impaired adult hippocampal neurogenesis and reduced spine density in the DG granule neurons. Although Stat4A mice display deficient NMDA receptor-dependent memory in contextual discrimination learning, which is dependent on hippocampal neurogenesis, their NMDA receptor-independent memory is normal. Confirming NMDA receptor involvement in the memory deficits, Stat4A mutant mice have a decrease in the level of synaptic NMDA receptors and a reduction in learning-dependent CREB-mediated gene transcription. The deficits in neurogenesis, spinogenesis, and memory in Stat4A mice are not present in mice in which tTA/tetO-dependent transgene transcription is blocked by doxycycline through their life. The memory deficits are also rescued within 3 d by intrahippocampal infusion of doxycycline, further indicating a role for stathmin expressed in the DG in contextual memory. Our findings therefore point to stathmin and microtubules as a mechanistic link between neurogenesis, spinogenesis, and NMDA receptor-dependent memory formation in the DG. SIGNIFICANCE STATEMENT In the present study, we aimed to clarify the role of stathmin in neuronal and behavioral functions. We characterized the neurogenic, behavioral, and molecular consequences of the gain-of-function stathmin mutation using a bitransgenic mouse expressing a constitutively active form of stathmin. We found that stathmin plays an important role in adult hippocampal neurogenesis and spinogenesis. In addition, stathmin mutation led to impaired NMDA receptor-dependent and neurogenesis-associated memory and did not affect NMDA receptor-independent memory. Moreover, biochemical analysis suggested that stathmin regulates the synaptic transport of NMDA receptors, which in turn influence CREB-mediated gene transcription machinery. Overall, these data suggest that stathmin is an important molecule for neurogenesis, spinogenesis, and NMDA receptor-dependent learning and memory. PMID:26818507

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.

Augmentation by escitalopram, but not citalopram or R-citalopram, of the effects of low-dose risperidone: behavioral, biochemical, and electrophysiological evidence.

PubMed

Marcus, Monica M; Jardemark, Kent; Malmerfelt, Anna; Gertow, Jens; Konradsson-Geuken, Asa; Svensson, Torgny H

2012-04-01

Antidepressant drugs are frequently used to treat affective symptoms in schizophrenia. We have recently shown that escitalopram, but not citalopram or R-citalopram, increases firing rate and burst firing of midbrain dopamine neurons, potentiates cortical N-methyl-D-aspartate (NMDA) receptor-mediated transmission and enhances cognition, effects that might influence the outcome of concomitant antipsychotic medication. Here, we studied, in rats, the behavioral and neurobiological effects of adding escitalopram, citalopram, or R-citalopram to the second-generation antipsychotic drug risperidone. We examined antipsychotic efficacy using the conditioned avoidance response (CAR) test, extrapyramidal side effect (EPS) liability using a catalepsy test, dopamine outflow in the medial prefrontal cortex (mPFC) and nucleus accumbens using in vivo microdialysis in freely moving animals, and NMDA receptor-mediated transmission in the mPFC using intracellular electrophysiological recording in vitro. Only escitalopram (5 mg/kg), but not citalopram (10 mg/kg), or R-citalopram (10 mg/kg), dramatically enhanced the antipsychotic-like effect of a low dose of risperidone (0.25 mg/kg), without increasing catalepsy. Given alone, escitalopram, but not citalopram or R-citalopram, markedly enhanced both cortical dopamine output and NMDA receptor-mediated transmission. Addition of escitalopram and to some extent R-citalopram, but not citalopram, significantly enhanced both cortical dopamine output and cortical NMDA receptor-mediated transmission induced by a suboptimal dose/concentration of risperidone. These results suggest that adjunct treatment with escitalopram, but not citalopram, may enhance the effect of a subtherapeutic dose of risperidone on positive, negative, cognitive, and depressive symptoms in schizophrenia, yet without increased EPS liability. Copyright © 2011 Wiley Periodicals, Inc.

MPTP-meditated hippocampal dopamine deprivation modulates synaptic transmission and activity-dependent synaptic plasticity

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

Zhu Guoqi; Chen Ying; Huang Yuying

2011-08-01

Parkinson's disease (PD)-like symptoms including learning deficits are inducible by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Therefore, it is possible that MPTP may disturb hippocampal memory processing by modulation of dopamine (DA)- and activity-dependent synaptic plasticity. We demonstrate here that intraperitoneal (i.p.) MPTP injection reduces the number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra (SN) within 7 days. Subsequently, the TH expression level in SN and hippocampus and the amount of DA and its metabolite DOPAC in striatum and hippocampus decrease. DA depletion does not alter basal synaptic transmission and changes pair-pulse facilitation (PPF) of field excitatory postsynaptic potentials (fEPSPs) only atmore » the 30 ms inter-pulse interval. In addition, the induction of long-term potentiation (LTP) is impaired whereas the duration of long-term depression (LTD) becomes prolonged. Since both LTP and LTD depend critically on activation of NMDA and DA receptors, we also tested the effect of DA depletion on NMDA receptor-mediated synaptic transmission. Seven days after MPTP injection, the NMDA receptor-mediated fEPSPs are decreased by about 23%. Blocking the NMDA receptor-mediated fEPSP does not mimic the MPTP-LTP. Only co-application of D1/D5 and NMDA receptor antagonists during tetanization resembled the time course of fEPSP potentiation as observed 7 days after i.p. MPTP injection. Together, our data demonstrate that MPTP-induced degeneration of DA neurons and the subsequent hippocampal DA depletion alter NMDA receptor-mediated synaptic transmission and activity-dependent synaptic plasticity. - Highlights: > I.p. MPTP-injection mediates death of dopaminergic neurons. > I.p. MPTP-injection depletes DA and DOPAC in striatum and hippocampus. > I.p. MPTP-injection does not alter basal synaptic transmission. > Reduction of LTP and enhancement of LTD after i.p. MPTP-injection. > Attenuation of NMDA-receptors mediated fEPSPs after i.p. MPTP-injection.« less

Blockade of NMDA receptors decreased spinal microglia activation in bee venom induced acute inflammatory pain in rats.

PubMed

Li, Li; Wu, Yongfang; Bai, Zhifeng; Hu, Yuyan; Li, Wenbin

2017-03-01

Microglial cells in spinal dorsal horn can be activated by nociceptive stimuli and the activated microglial cells release various cytokines enhancing the nociceptive transmission. However, the mechanisms underlying the activation of spinal microglia during nociceptive stimuli have not been well understood. In order to define the role of NMDA receptors in the activation of spinal microglia during nociceptive stimuli, the present study was undertaken to investigate the effect of blockade of NMDA receptors on the spinal microglial activation induced by acute peripheral inflammatory pain in rats. The acute inflammatory pain was induced by subcutaneous bee venom injection to the plantar surface of hind paw of rats. Spontaneous pain behavior, thermal withdrawal latency and mechanical withdrawal threshold were rated. The expression of specific microglia marker CD11b/c was assayed by immunohistochemistry and western blot. After bee venom treatment, it was found that rats produced a monophasic nociception characterized by constantly lifting and licking the injected hind paws, decreased thermal withdrawal latency and mechanical withdrawal threshold; immunohistochemistry displayed microglia with enlarged cell bodies, thickened, extended cellular processes with few ramifications, small spines, and intensive immunostaining; western blot showed upregulated expression level of CD11b/c within the period of hyperalgesia. Prior intrathecal injection of MK-801, a selective antagonist of NMDA receptors, attenuated the pain behaviors and suppressed up-regulation of CD11b/c induced by bee venom. It can be concluded that NMDA receptors take part in the mediation of spinal microglia activation in bee venom induced peripheral inflammatory pain and hyperalgesia in rats.

The role of striatal NMDA receptors in drug addiction.

PubMed

Ma, Yao-Ying; Cepeda, Carlos; Cui, Cai-Lian

2009-01-01

The past decade has witnessed an impressive accumulation of evidence indicating that the excitatory amino acid glutamate and its receptors, in particular the N-methyl-D-aspartate (NMDA) receptor subtype, play an important role in drug addiction. Various lines of research using animal models of drug addiction have demonstrated that drug-induced craving is accompanied by significant upregulation of NR2B subunit expression. Furthermore, selective blockade of NR2B-containing NMDA receptors in the striatum, especially in the nucleus accumbens (NAc) can inhibit drug craving and reinstatement. The purpose of this review is to examine the role of striatal NMDA receptors in drug addiction. After a brief description of glutamatergic innervation and NMDA receptor subunit distribution in the striatum, we discuss potential mechanisms to explain the role of striatal NMDA receptors in drug addiction by elucidating signaling cascades involved in the regulation of subunit expression and redistribution, phosphorylation of receptor subunits, as well as activation of intracellular signals triggered by drug experience. Understanding the mechanisms regulating striatal NMDA receptor changes in drug addiction will provide more specific and rational targets to counteract the deleterious effects of drug addiction.

Competitive (AP7) and non-competitive (MK-801) NMDA receptor antagonists differentially alter glucose utilization in rat cortex

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

Clow, D.W.; Lee, S.J.; Hammer, R.P. Jr.

1991-04-01

The effects of D,L-2-amino-7-phosphonoheptanoic acid (AP7), a competitive N-methyl-D-aspartate (NMDA) receptor antagonist, and MK-801, a non-competitive NMDA receptor antagonist, on regional brain metabolism were studied in unanesthetized, freely moving rats by using the quantitative {sup 14}C2-deoxyglucose autoradiographic procedure. AP7 (338 or 901 mg/kg) produced a dose-dependent decrease of metabolic activity throughout most of the regions studied including sensory, motor, and limbic cortices. In contrast, MK-801 (0.1 or 1.0 mg/kg) resulted in a dose-dependent decrease of metabolic activity in sensory cortices, and an increase in limbic regions such as the hippocampal stratum lacunosum moleculare and entorhinal cortex. MK-801 also produced amore » biphasic response in agranular motor cortex, whereby the low dose increased while the high dose decreased labeling. In addition, MK-801 produced heterogeneous effects on regional cerebral metabolism in sensory cortices. Metabolic activity decreased in layer IV relative to layer Va following MK-801 treatment in primary somatosensory (SI) and visual (VI) cortices, suggesting a shift in activity from afferent fibers innervating layer IV to those innervating layer Va. MK-801 administration also decreased metabolic activity in granular SI relative to dysgranular SI, and in VI relative to secondary visual cortex (VII), thus providing a relative sparing of activity in dysgranular SI and VII. Thus, the non-competitive NMDA receptor antagonist suppressed activity from extrinsic neocortical sources, enhancing relative intracortical activity and stimulating limbic regions, while the competitive NMDA antagonist depressed metabolic activity in all cortical regions.« less

Rapamycin prevents N-methyl-D-aspartate-induced retinal damage through an ERK-dependent mechanism in rats.

PubMed

Ichikawa, Atsuko; Nakahara, Tsutomu; Kurauchi, Yuki; Mori, Asami; Sakamoto, Kenji; Ishii, Kunio

2014-06-01

Recent studies have demonstrated that inhibition of the mammalian target of rapamycin (mTOR) protects against neuronal injury, but the mechanisms underlying this protection are not fully understood. The present study investigates whether rapamycin, an inhibitor of the mTOR pathway, protects against N-methyl-D-aspartate (NMDA)-induced retinal neurotoxicity and whether the extracellular signal-regulated kinase (ERK) pathway contributes to this protective effect in rats. Significant cell loss in the ganglion cell layer and a reduction in thickness of the inner plexiform layer were observed 7 days after a single intravitreal injection of NMDA (200 nmol/eye). These NMDA-induced morphological changes were significantly reduced by rapamycin (20 nmol/eye). The number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive apoptotic cells had increased 6 hr after NMDA injection, an effect that was significantly attenuated by rapamycin. The ERK inhibitor U0126 (1 nmol/eye) almost completely abolished rapamycin's inhibition of NMDA-induced apoptosis. Immunohistochemical studies showed that NMDA caused a time-dependent increase in levels of the phosphorylated form of the ribosomal protein S6 (pS6), a downstream indicator of mTOR activity. The increased pS6 levels were markedly decreased by rapamycin. Both NMDA and rapamycin increased the level of phosphorylated ERK (pERK) in Müller cells, and coinjection of both agents further increased pERK levels. These results suggest that rapamycin has a neuroprotective effect against NMDA-induced retinal neurotoxicity and that this effect could be patially mediated by activation of the ERK pathway in retinal Müller cells. Copyright © 2014 Wiley Periodicals, Inc.

H-Ras Modulates N-Methyl-d-aspartate Receptor Function via Inhibition of Src Tyrosine Kinase Activity*

PubMed Central

Thornton, Claire; Yaka, Rami; Dinh, Son; Ron, Dorit

2005-01-01

Tyrosine phosphorylation of the NR2A and NR2B subunits of the N-methyl-d-aspartate (NMDA) receptor by Src protein-tyrosine kinases modulates receptor channel activity and is necessary for the induction of long term potentiation (LTP). Deletion of H-Ras increases both NR2 tyrosine phosphorylation and NMDA receptor-mediated hippocampal LTP. Here we investigated whether H-Ras regulates phosphorylation and function of the NMDA receptor via Src family protein-tyrosine kinases. We identified Src as a novel H-Ras binding partner. H-Ras bound to Src but not Fyn both in vitro and in brain via the Src kinase domain. Cotransfection of H-Ras and Src inhibited Src activity and decreased NR2A tyrosine phosphorylation. Treatment of rat brain slices with Tat-H-Ras depleted NR2A from the synaptic membrane, decreased endogenous Src activity and NR2A phosphorylation, and decreased the magnitude of hip-pocampal LTP. No change was observed for NR2B. We suggest that H-Ras negatively regulates Src phosphorylation of NR2A and retention of NR2A into the synaptic membrane leading to inhibition of NMDA receptor function. This mechanism is specific for Src and NR2A and has implications for studies in which regulation of NMDA receptor-mediated LTP is important, such as synaptic plasticity, learning, and memory and addiction. PMID:12695509

Development of 2′-substituted (2S,1′R,2′S)-2-(carboxycyclopropyl)glycine analogues as potent N-methyl-d-aspartic acid receptor agonists

PubMed Central

Risgaard, Rune; Nielsen, Simon D.; Hansen, Kasper B.; Jensen, Christina M.; Nielsen, Birgitte; Traynelis, Stephen F.; Clausen, Rasmus P.

2013-01-01

A series of 2′-substituted analogues of the selective NMDA receptor ligand (2S,1′R,2′S)-2-(carboxycyclopropyl)glycine ((S)-CCG-IV) have been designed, synthesized and pharmacologically characterized. The design was based on a docking study hypothesizing that substituents in the 2′-position would protrude into a region where differences among the NMDA receptor GluN2 subunits exist. Various synthetic routes were explored, and two different routes provided a series of alkyl-substituted analogues. Pharmacological characterization revealed that these compounds are NMDA receptor agonists and that potency decreases with increasing size of the alkyl groups. Variations in agonist activity are observed at the different recombinant NMDA receptor subtypes. This study demonstrates that it is possible to introduce substituents in the 2′-position of (S)-CCG-IV while maintaining agonist activity and that variation among NMDA receptor subtypes may be achieved by probing this region of the receptor. PMID:23614571

A critical role of spinal Shank2 proteins in NMDA-induced pain hypersensitivity

PubMed Central

Yoon, Seo-Yeon; Kwon, Soon-Gu; Kim, Yong Ho; Yeo, Ji-Hee; Ko, Hyoung-Gon; Roh, Dae-Hyun; Kaang, Bong-Kiun; Beitz, Alvin J; Lee, Jang-Hern

2017-01-01

Background Self-injurious behaviors (SIBs) are devastating traits in autism spectrum disorder (ASD). Although deficits in pain sensation might be one of the contributing factors underlying the development of SIBs, the mechanisms have yet to be addressed. Recently, the Shank2 synaptic protein has been considered to be a key component in ASD, and mutations of SHANK2 gene induce the dysfunction of N-methyl-D-aspartate (NMDA) receptors, suggesting a link between Shank2 and NMDA receptors in ASD. Given that spinal NMDA receptors play a pivotal role in pain hypersensitivity, we investigated the possible role of Shank2 in nociceptive hypersensitivity by examining changes in spontaneous pain following intrathecal NMDA injection in Shank2−/− (Shank2 knock-out, KO) mice. Results Intrathecal NMDA injection evoked spontaneous nociceptive behaviors. These NMDA-induced nociceptive responses were significantly reduced in Shank2 KO mice. We also observed a significant decrease of NMDA currents in the spinal dorsal horn of Shank2 KO mice. Subsequently, we examined whether mitogen-activated protein kinase or AKT signaling is involved in this reduced pain behavior in Shank2 KO mice because the NMDA receptor is closely related to these signaling molecules. Western blotting and immunohistochemistry revealed that spinally administered NMDA increased the expression of a phosphorylated form of extracellular signal-regulated kinase (p-ERK) which was significantly reduced in Shank2 KO mice. However, p38, JNK, or AKT were not changed by NMDA administration. The ERK inhibitor, PD98059, decreased NMDA-induced spontaneous pain behaviors in a dose-dependent manner in wild-type mice. Moreover, it was found that the NMDA-induced increase in p-ERK was primarily colocalized with Shank2 proteins in the spinal cord dorsal horn. Conclusion Shank2 protein is involved in spinal NMDA receptor-mediated pain, and mutations of Shank2 may suppress NMDA-ERK signaling in spinal pain transmission. This study provides new clues into the mechanisms underlying pain deficits associated with SIB and deserves further study in patients with ASD. PMID:28326932

A critical role of spinal Shank2 proteins in NMDA-induced pain hypersensitivity.

PubMed

Yoon, Seo-Yeon; Kwon, Soon-Gu; Kim, Yong Ho; Yeo, Ji-Hee; Ko, Hyoung-Gon; Roh, Dae-Hyun; Kaang, Bong-Kiun; Beitz, Alvin J; Lee, Jang-Hern; Oh, Seog Bae

2017-01-01

Background Self-injurious behaviors (SIBs) are devastating traits in autism spectrum disorder (ASD). Although deficits in pain sensation might be one of the contributing factors underlying the development of SIBs, the mechanisms have yet to be addressed. Recently, the Shank2 synaptic protein has been considered to be a key component in ASD, and mutations of SHANK2 gene induce the dysfunction of N-methyl-D-aspartate (NMDA) receptors, suggesting a link between Shank2 and NMDA receptors in ASD. Given that spinal NMDA receptors play a pivotal role in pain hypersensitivity, we investigated the possible role of Shank2 in nociceptive hypersensitivity by examining changes in spontaneous pain following intrathecal NMDA injection in S hank2-/- ( Shank2 knock-out, KO) mice. Results Intrathecal NMDA injection evoked spontaneous nociceptive behaviors. These NMDA-induced nociceptive responses were significantly reduced in Shank2 KO mice. We also observed a significant decrease of NMDA currents in the spinal dorsal horn of Shank2 KO mice. Subsequently, we examined whether mitogen-activated protein kinase or AKT signaling is involved in this reduced pain behavior in Shank2 KO mice because the NMDA receptor is closely related to these signaling molecules. Western blotting and immunohistochemistry revealed that spinally administered NMDA increased the expression of a phosphorylated form of extracellular signal-regulated kinase (p-ERK) which was significantly reduced in Shank2 KO mice. However, p38, JNK, or AKT were not changed by NMDA administration. The ERK inhibitor, PD98059, decreased NMDA-induced spontaneous pain behaviors in a dose-dependent manner in wild-type mice. Moreover, it was found that the NMDA-induced increase in p-ERK was primarily colocalized with Shank2 proteins in the spinal cord dorsal horn. Conclusion Shank2 protein is involved in spinal NMDA receptor-mediated pain, and mutations of Shank2 may suppress NMDA-ERK signaling in spinal pain transmission. This study provides new clues into the mechanisms underlying pain deficits associated with SIB and deserves further study in patients with ASD.

Mitochondrial Division Inhibitor 1 (mdivi-1) Protects Neurons against Excitotoxicity through the Modulation of Mitochondrial Function and Intracellular Ca2+ Signaling.

PubMed

Ruiz, Asier; Alberdi, Elena; Matute, Carlos

2018-01-01

Excessive dynamin related protein 1 (Drp1)-triggered mitochondrial fission contributes to apoptosis under pathological conditions and therefore it has emerged as a promising therapeutic target. Mitochondrial division inhibitor 1 (mdivi-1) inhibits Drp1-dependent mitochondrial fission and is neuroprotective in several models of brain ischemia and neurodegeneration. However, mdivi-1 also modulates mitochondrial function and oxidative stress independently of Drp1, and consequently the mechanisms through which it protects against neuronal injury are more complex than previously foreseen. In this study, we have analyzed the effects of mdivi-1 on mitochondrial dynamics, Ca 2+ signaling, mitochondrial bioenergetics and cell viability during neuronal excitotoxicity in vitro . Time-lapse fluorescence microscopy revealed that mdivi-1 blocked NMDA-induced mitochondrial fission but not that triggered by sustained AMPA receptor activation, showing that mdivi-1 inhibits excitotoxic mitochondrial fragmentation in a source specific manner. Similarly, mdivi-1 strongly reduced NMDA-triggered necrotic-like neuronal death and, to a lesser extent, AMPA-induced toxicity. Interestingly, neuroprotection provided by mdivi-1 against NMDA, but not AMPA, correlated with a reduction in cytosolic Ca 2+ ([Ca 2+ ] cyt ) overload and calpain activation indicating additional cytoprotective mechanisms. Indeed, mdivi-1 depolarized mitochondrial membrane and depleted ER Ca 2+ content, leading to attenuation of mitochondrial [Ca 2+ ] increase and enhancement of the integrated stress response (ISR) during NMDA receptor activation. Finally, lentiviral knockdown of Drp1 did not rescue NMDA-induced mitochondrial fission and toxicity, indicating that neuroprotective activity of mdivi-1 is Drp1-independent. Together, these results suggest that mdivi-1 induces a Drp1-independent protective phenotype that prevents predominantly NMDA receptor-mediated excitotoxicity through the modulation of mitochondrial function and intracellular Ca 2+ signaling.

Activity-dependent shedding of the NMDA receptor glycine binding site by matrix metalloproteinase 3: a PUTATIVE mechanism of postsynaptic plasticity.

PubMed

Pauly, Thorsten; Ratliff, Miriam; Pietrowski, Eweline; Neugebauer, Rainer; Schlicksupp, Andrea; Kirsch, Joachim; Kuhse, Jochen

2008-07-16

Functional and structural alterations of clustered postsynaptic ligand gated ion channels in neuronal cells are thought to contribute to synaptic plasticity and memory formation in the human brain. Here, we describe a novel molecular mechanism for structural alterations of NR1 subunits of the NMDA receptor. In cultured rat spinal cord neurons, chronic NMDA receptor stimulation induces disappearance of extracellular epitopes of NMDA receptor NR1 subunits, which was prevented by inhibiting matrix metalloproteinases (MMPs). Immunoblotting revealed the digestion of solubilized NR1 subunits by MMP-3 and identified a fragment of about 60 kDa as MMPs-activity-dependent cleavage product of the NR1 subunit in cultured neurons. The expression of MMP-3 in the spinal cord culture was shown by immunoblotting and immunofluorescence microscopy. Recombinant NR1 glycine binding protein was used to identify MMP-3 cleavage sites within the extracellular S1 and S2-domains. N-terminal sequencing and site-directed mutagenesis revealed S542 and L790 as two putative major MMP-3 cleavage sites of the NR1 subunit. In conclusion, our data indicate that MMPs, and in particular MMP-3, are involved in the activity dependent alteration of NMDA receptor structure at postsynaptic membrane specializations in the CNS.

Activity-Dependent Shedding of the NMDA Receptor Glycine Binding Site by Matrix Metalloproteinase 3: A PUTATIVE Mechanism of Postsynaptic Plasticity

PubMed Central

Pietrowski, Eweline; Neugebauer, Rainer; Schlicksupp, Andrea; Kirsch, Joachim; Kuhse, Jochen

2008-01-01

Functional and structural alterations of clustered postsynaptic ligand gated ion channels in neuronal cells are thought to contribute to synaptic plasticity and memory formation in the human brain. Here, we describe a novel molecular mechanism for structural alterations of NR1 subunits of the NMDA receptor. In cultured rat spinal cord neurons, chronic NMDA receptor stimulation induces disappearance of extracellular epitopes of NMDA receptor NR1 subunits, which was prevented by inhibiting matrix metalloproteinases (MMPs). Immunoblotting revealed the digestion of solubilized NR1 subunits by MMP-3 and identified a fragment of about 60 kDa as MMPs-activity-dependent cleavage product of the NR1 subunit in cultured neurons. The expression of MMP-3 in the spinal cord culture was shown by immunoblotting and immunofluorescence microscopy. Recombinant NR1 glycine binding protein was used to identify MMP-3 cleavage sites within the extracellular S1 and S2-domains. N-terminal sequencing and site-directed mutagenesis revealed S542 and L790 as two putative major MMP-3 cleavage sites of the NR1 subunit. In conclusion, our data indicate that MMPs, and in particular MMP-3, are involved in the activity dependent alteration of NMDA receptor structure at postsynaptic membrane specializations in the CNS. PMID:18629001

Characterization of spontaneous excitatory synaptic currents in salamander retinal ganglion cells.

PubMed Central

Taylor, W R; Chen, E; Copenhagen, D R

1995-01-01

1. Spontaneous excitatory postsynaptic currents (sEPSCs) were recorded under voltage-clamp conditions. Consistent with activation of non-NMDA-type glutamate receptors, the sEPSCs reversed at potentials above 0 mV, were blocked by 1 microM CNQX and prolonged by 2 mM aniracetam. 2. The peak conductance of the averaged sEPSCs (n = 70-400) was 130 +/- 60 pS (mean +/- S.D.; 17 cells, ranging from 70 to 290 pS). Amplitude distributions were skewed towards larger amplitudes. 3. The decay of individual and mean sEPSCs was exponential with a mean time constant (tau d) of 3.75 +/- 0.84 ms (n = 13), which was voltage independent. The 10-90% rise time of the sEPSCs was 1.30 +/- 0.44 ms (n = 13). There was no correlation between sEPSC rise time and tau d suggesting that dendritic filtering alone did not shape the time course of sEPSCs. 4. Light-evoked EPSCs in these retinal ganglion cells are mediated by concomitant activation of NMDA and non-NMDA receptors; however, no NMDA component was discerned in the sEPSCs, even when recording at -96 mV in Mg(2+)-free solutions. The decay time course was not altered by 20 microM AP7, an NMDA antagonist, nor was an NMDA component unmasked by adding glycine or D-serine. These results suggest that NMDA and non-NMDA receptors are not coactivated by a single vesicle of transmitter during spontaneous release, and thus are probably not colocalized in the postsynaptic membrane at the sites of spontaneous release. 5. The sEPSCs were an order of magnitude faster than the non-NMDA receptor-mediated EPSCs evoked by light stimuli, and it is proposed that the EPSC time course is determined largely by the extended time course of release of synaptic vesicles from bipolar cells. The quantal content of a light-evoked non-NMDA receptor-mediated EPSC in an on-off cell is about 200 quanta. Images Figure 6 PMID:7562636

Medial prefrontal cortex TRPV1 and CB1 receptors modulate cardiac baroreflex activity by regulating the NMDA receptor/nitric oxide pathway.

PubMed

Lagatta, Davi C; Kuntze, Luciana B; Ferreira-Junior, Nilson C; Resstel, Leonardo B M

2018-05-29

The ventral medial prefrontal cortex (vMPFC) facilitates the cardiac baroreflex response through N-methyl-D-aspartate (NMDA) receptor activation and nitric oxide (NO) formation by neuronal NO synthase (nNOS) and soluble guanylate cyclase (sGC) triggering. Glutamatergic transmission is modulated by the cannabinoid receptor type 1 (CB 1 ) and transient receptor potential vanilloid type 1 (TRPV 1 ) receptors, which may inhibit or stimulate glutamate release in the brain, respectively. Interestingly, vMPFC CB 1 receptors decrease cardiac baroreflex responses, while TRPV 1 channels facilitate them. Therefore, the hypothesis of the present study is that the vMPFC NMDA/NO pathway is regulated by both CB 1 and TRPV 1 receptors in the modulation of cardiac baroreflex activity. In order to test this assumption, we used male Wistar rats that had stainless steel guide cannulae bilaterally implanted in the vMPFC. Subsequently, a catheter was inserted into the femoral artery, for cardiovascular recordings, and into the femoral vein for assessing baroreflex activation. The increase in tachycardic and bradycardic responses observed after the microinjection of a CB 1 receptors antagonist into the vMPFC was prevented by an NMDA antagonist as well as by the nNOS and sGC inhibition. NO extracellular scavenging also abolished these responses. These same pharmacological manipulations inhibited cardiac reflex enhancement induced by TRPV 1 agonist injection into the area. Based on these results, we conclude that vMPFC CB 1 and TRPV 1 receptors inhibit or facilitate the cardiac baroreflex activity by stimulating or blocking the NMDA activation and NO synthesis.

Basic pharmacology of NMDA receptors.

PubMed

Gonda, Xenia

2012-01-01

NMDA receptors are ionotropic receptors mediating glutamatergic neurotransmission and play a role in several basic functions in the central nervous system, from regulating neurodevelopment and synaptic plasticity, learning and memory formation, cognitive processes, rhythm generation necessary for locomotor activity and breathing, and excitotoxicity. Due to their complex involvement in the above processes, NMDA receptors have been established to play a role in the etiopathology of several neuropsychiatric disorders such as ischaemia and traumatic brain injury, neurodegenerative disorders, pain syndromes, addiction, affective disorders and such neurodevelopmental disorders as autism or schizophrenia. NMDA receptors contain multiple types of subunits with distinct functional and pharmacological properties making the picture more complex. These receptors also offer multiple binding sites to be targeted with pharmacons, however, early broad-spectrum NMDA receptor antagonists had limited clinical use due to their intolerable adverse effect profile. The discovery of several types of subunit selective NMDA receptor antagonists may offer valuable therapeutic possibilities for several disorders, with improved clinical efficacy and decreased side effects. However, in spite of our increasing knowledge concerning the involvement of NMDA receptors in pathological processes, molecules with a selective action, tolerable side effect profile and good clinical efficacy are still only in clinical development in the majority of cases. Nevertheless, NMDA receptors offer a novel opportunity in the treatment of various neuropsychiatric conditions.

Kinetic Contributions to Gating by Interactions Unique to N-methyl-d-aspartate (NMDA) Receptors*

PubMed Central

Borschel, William F.; Cummings, Kirstie A.; Tindell, LeeAnn K.; Popescu, Gabriela K.

2015-01-01

Among glutamate-gated channels, NMDA receptors produce currents that subside with unusually slow kinetics, and this feature is essential to the physiology of central excitatory synapses. Relative to the homologous AMPA and kainate receptors, NMDA receptors have additional intersubunit contacts in the ligand binding domain that occur at both conserved and non-conserved sites. We examined GluN1/GluN2A single-channel currents with kinetic analyses and modeling to probe these class-specific intersubunit interactions for their role in glutamate binding and receptor gating. We found that substitutions that eliminate such interactions at non-conserved sites reduced stationary gating, accelerated deactivation, and imparted sensitivity to aniracetam, an AMPA receptor-selective positive modulator. Abolishing unique contacts at conserved sites also reduced stationary gating and accelerated deactivation. These results show that contacts specific to NMDA receptors, which brace the heterodimer interface within the ligand binding domain, stabilize actively gating receptor conformations and result in longer bursts and slower deactivations. They support the view that the strength of the heterodimer interface modulates gating in both NMDA and non-NMDA receptors and that unique interactions at this interface are responsible in part for basic differences between the kinetics of NMDA and non-NMDA currents at glutamatergic synapses. PMID:26370091

Structure of the Zinc-Bound Amino-Terminal Domain of the NMDA Receptor NR2B Subunit

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

Karakas, E.; Simorowski, N; Furukawa, H

2009-01-01

N-methyl-D-aspartate (NMDA) receptors belong to the family of ionotropic glutamate receptors (iGluRs) that mediate the majority of fast excitatory synaptic transmission in the mammalian brain. One of the hallmarks for the function of NMDA receptors is that their ion channel activity is allosterically regulated by binding of modulator compounds to the extracellular amino-terminal domain (ATD) distinct from the L-glutamate-binding domain. The molecular basis for the ATD-mediated allosteric regulation has been enigmatic because of a complete lack of structural information on NMDA receptor ATDs. Here, we report the crystal structures of ATD from the NR2B NMDA receptor subunit in the zinc-freemore » and zinc-bound states. The structures reveal the overall clamshell-like architecture distinct from the non-NMDA receptor ATDs and molecular determinants for the zinc-binding site, ion-binding sites, and the architecture of the putative phenylethanolamine-binding site.« less

Excitatory amino acids in epilepsy and potential novel therapies.

PubMed

Meldrum, B S

1992-07-01

Evidence that an abnormality of excitatory neurotransmission may contribute to the epileptic phenomena in various animal and human syndromes is reviewed. Altered glutamate transport or metabolism may be a contributory factor in some genetic syndromes and enhanced responsiveness to activation of NMDA receptors may be significant in various acquired forms of epilepsy. Decreasing glutamatergic neurotransmission provides a rational therapeutic approach to epilepsy. Potent anticonvulsant effects are seen with the acute administration of NMDA antagonists in a wide range of animal models. Some competitive antagonists acting at the NMDA/glutamate site show prolonged anticonvulsant activity following oral administration at doses free of motor side effects and appear suitable for clinical trial.

Different Molecular Mechanisms Mediate Direct or Glia-Dependent Prion Protein Fragment 90-231 Neurotoxic Effects in Cerebellar Granule Neurons.

PubMed

Thellung, Stefano; Gatta, Elena; Pellistri, Francesca; Villa, Valentina; Corsaro, Alessandro; Nizzari, Mario; Robello, Mauro; Florio, Tullio

2017-10-01

Glia over-stimulation associates with amyloid deposition contributing to the progression of central nervous system neurodegenerative disorders. Here we analyze the molecular mechanisms mediating microglia-dependent neurotoxicity induced by prion protein (PrP)90-231, an amyloidogenic polypeptide corresponding to the protease-resistant portion of the pathological prion protein scrapie (PrP Sc ). PrP90-231 neurotoxicity is enhanced by the presence of microglia within neuronal culture, and associated to a rapid neuronal [Ca ++ ] i increase. Indeed, while in "pure" cerebellar granule neuron cultures, PrP90-231 causes a delayed intracellular Ca ++ entry mediated by the activation of NMDA receptors; when neuron and glia are co-cultured, a transient increase of [Ca ++ ] i occurs within seconds after treatment in both granule neurons and glial cells, then followed by a delayed and sustained [Ca ++ ] i raise, associated with the induction of the expression of inducible nitric oxide synthase and phagocytic NADPH oxidase. [Ca ++ ] i fast increase in neurons is dependent on the activation of multiple pathways since it is not only inhibited by the blockade of voltage-gated channel activity and NMDA receptors but also prevented by the inhibition of nitric oxide and PGE 2 release from glial cells. Thus, Ca ++ homeostasis alteration, directly induced by PrP90-231 in cerebellar granule cells, requires the activation of NMDA receptors, but is greatly enhanced by soluble molecules released by activated glia. In glia-enriched cerebellar granule cultures, the activation of inducible nitric oxide (iNOS) and NADPH oxidase represents the main mechanism of toxicity since their pharmacological inhibition prevented PrP90-231 neurotoxicity, whereas NMDA blockade by D(-)-2-amino-5-phosphonopentanoic acid is ineffective; conversely, in pure cerebellar granule cultures, NMDA blockade but not iNOS inhibition strongly reduced PrP90-231 neurotoxicity. These data indicate that amyloidogenic peptides induce neurotoxic signals via both direct neuron interaction and glia activation through different mechanisms responsible of calcium homeostasis disruption in neurons and potentiating each other: the activation of excitotoxic pathways via NMDA receptors and the release of radical species that establish an oxidative milieu.

Excitotoxicity in the Lung: N-Methyl-D-Aspartate-Induced, Nitric Oxide-Dependent, Pulmonary Edema is Attenuated by Vasoactive Intestinal Peptide and by Inhibitors of Poly(ADP-Ribose) Polymerase

NASA Astrophysics Data System (ADS)

Said, Sami I.; Berisha, Hasan I.; Pakbaz, Hedayatollah

1996-05-01

Excitatory amino acid toxicity, resulting from overactivation of N-methyl-D-aspartate (NMDA) glutamate receptors, is a major mechanism of neuronal cell death in acute and chronic neurological diseases. We have investigated whether excitotoxicity may occur in peripheral organs, causing tissue injury, and report that NMDA receptor activation in perfused, ventilated rat lungs triggered acute injury, marked by increased pressures needed to ventilate and perfuse the lung, and by high-permeability edema. The injury was prevented by competitive NMDA receptor antagonists or by channel-blocker MK-801, and was reduced in the presence of Mg2+. As with NMDA toxicity to central neurons, the lung injury was nitric oxide (NO) dependent: it required L-arginine, was associated with increased production of NO, and was attenuated by either of two NO synthase inhibitors. The neuropeptide vasoactive intestinal peptide and inhibitors of poly(ADP-ribose) polymerase also prevented this injury, but without inhibiting NO synthesis, both acting by inhibiting a toxic action of NO that is critical to tissue injury. The findings indicate that: (i) NMDA receptors exist in the lung (and probably elsewhere outside the central nervous system), (ii) excessive activation of these receptors may provoke acute edematous lung injury as seen in the ``adult respiratory distress syndrome,'' and (iii) this injury can be modulated by blockade of one of three critical steps: NMDA receptor binding, inhibition of NO synthesis, or activation of poly(ADP-ribose) polymerase.

Choline exposure reduces potentiation of N-methyl-D-aspartate toxicity by corticosterone in the developing hippocampus.

PubMed

Mulholland, Patrick J; Self, Rachel L; Harris, Barton R; Littleton, John M; Prendergast, Mark A

2004-11-25

Exposure to high levels of glucocorticoids (GCs) may adversely affect neuronal viability, particularly in the developing hippocampus, via increased function or sensitivity of N-methyl-D-aspartate (NMDA)-type glutamate receptors. Conversely, choline supplementation in the developing brain may reduce the severity of subsequent insult. The present studies aimed to examine the extent to which short-term exposure to high concentrations of corticosterone would produce neuronal injury mediated by NMDA receptor activity. These studies also assessed the ability of choline to prevent this form of injury via interactions with nicotinic acetylcholine receptors (nAChRs) expressing the alpha7 subunit. Organotypic hippocampal slice cultures derived from neonatal rat were pre-treated for 72 h with corticosterone (100 nM) alone or with choline (0.1-10 mM), prior to a brief (1 h) NMDA exposure (5 microM). NMDA exposure produced significant cellular damage, reflected as increased fluorescence of the non-vital marker propidium iodide, in the CA1 region. While exposure to corticosterone alone did not produce damage, pre-treatment of cultures with corticosterone markedly exacerbated NMDA-induced toxicity. Pre-treatment with choline (> or =1 mM) alone or in combination with corticosterone markedly reduced subsequent NMDA toxicity, effects blocked by co-exposure to methyllycaconitine (100 nM), an antagonist active at nAChRs expressing the alpha7 subunit. These data suggest that even short-term exposure to high concentrations of GCs may adversely affect neuronal viability and that choline supplementation protects the brain from NMDA receptor-mediated damage, including that associated with hypercortisolemia.

Effects of D-cycloserine on extinction of mesolimbic cue reactivity in alcoholism: a randomized placebo-controlled trial.

PubMed

Kiefer, Falk; Kirsch, Martina; Bach, Patrick; Hoffmann, Sabine; Reinhard, Iris; Jorde, Anne; von der Goltz, Christoph; Spanagel, Rainer; Mann, Karl; Loeber, Sabine; Vollstädt-Klein, Sabine

2015-07-01

Mesocorticolimbic reactivity to alcohol-associated cues has been shown to be associated with relapse to renewed drinking and to be decreased by cue-exposure-based extinction training (CET). Evidence from preclinical studies suggests that the extinction of conditioned alcohol-seeking behavior might be facilitated by drugs increasing N-methyl-D-aspartate (NMDA) receptor-associated memory consolidation. In this study, we assessed the efficacy of CET treatment supplemented with the partial NMDA-receptor agonist D-cycloserine (DCS) at reducing mesolimbic cue reactivity (CR), craving, and relapse risk in alcoholism. In a randomized, placebo-controlled, double-blind study, we recruited 76 recently detoxified abstinent alcohol-dependent patients. Thirty-two (16 DCS, 16 placebo) patients showed cue-induced ventral-striatal activation measured with functional magnetic resonance imaging (fMRI) prior to treatment and were thus included in the efficacy analyses. After inpatient detoxification, patients underwent nine sessions of CET spaced over 3 weeks, receiving either 50 mg DCS or placebo 1 h prior to each CET session. FMRI was conducted before treatment and 3 weeks after treatment onset. Following treatment with CET plus DCS, cue-induced brain activation in the ventral and dorsal striatum was decreased compared to treatment with CET plus placebo. Elevated posttreatment ventral striatal CR and increased craving (assessed using the Obsessive Compulsive Drinking Scale) were associated with increased relapse risk. DCS was shown to augment the effect of CET for alcohol-dependent subjects. The interaction between craving and ventral-striatal CR on treatment outcome suggests that CET might be especially effective in patients exhibiting both high craving and elevated CR.

Evaluation of Neuroprotection and Behavioral Recovery by the Kappa- Opioid, PD 117302 Following Transient Forebrain Ischemia

DTIC Science & Technology

1994-01-01

shown to protect against NMDA -induced convul- mate- and aspartate-stimulated NMDA activity mediates delayed sions in rats (38), and to reduce...assessing a variety of pharmacological and physiological manip- competitive NMDA antagonists have been shown to decrease ulations (e.g., 40). Additionally...Hayward, N. J.; Tyers, 8. DeLong, G. R. Autism , amnesia, hippocampus, and learning. Neu- M. B.; Scopes, D. 1. C.; Naylor, A.; Judd, D. B. Neuroprotective

Altered Actions of Memantine and NMDA-Induced Currents in a New Grid2-Deleted Mouse Line

PubMed Central

Kumagai, Ayako; Fujita, Akira; Yokoyama, Tomoki; Nonobe, Yuki; Hasaba, Yasuhiro; Sasaki, Tsutomu; Itoh, Yumi; Koura, Minako; Suzuki, Osamu; Adachi, Shigeki; Ryo, Haruko; Kohara, Arihiro; Tripathi, Lokesh P.; Sanosaka, Masato; Fukushima, Toshiki; Takahashi, Hiroyuki; Kitagawa, Kazuo; Nagaoka, Yasuo; Kawahara, Hidehisa; Mizuguchi, Kenji; Nomura, Taisei; Matsuda, Junichiro; Tabata, Toshihide; Takemori, Hiroshi

2014-01-01

Memantine is a non-competitive antagonist of the N-methyl-d-aspartate (NMDA) receptor, and is an approved drug for the treatment of moderate-to-severe Alzheimer’s disease. We identified a mouse strain with a naturally occurring mutation and an ataxic phenotype that presents with severe leg cramps. To investigate the phenotypes of these mutant mice, we screened several phenotype-modulating drugs and found that memantine (10 mg/kg) disrupted the sense of balance in the mutants. Moreover, the mutant mice showed an attenuated optokinetic response (OKR) and impaired OKR learning, which was also observed in wild-type mice treated with memantine. Microsatellite analyses indicated that the Grid2 gene-deletion is responsible for these phenotypes. Patch-clamp analysis showed a relatively small change in NMDA-dependent current in cultured granule cells from Grid2 gene-deleted mice, suggesting that GRID2 is important for correct NMDA receptor function. In general, NMDA receptors are activated after the activation of non-NMDA receptors, such as AMPA receptors, and AMPA receptor dysregulation also occurs in Grid2 mutant mice. Indeed, the AMPA treatment enhanced memantine susceptibility in wild-type mice, which was indicated by balance sense and OKR impairments. The present study explores a new role for GRID2 and highlights the adverse effects of memantine in different genetic backgrounds. PMID:25513882

Pharmacological characterization of NMDA-like receptors in the single-celled organism Paramecium primaurelia.

PubMed

Ramoino, Paola; Candiani, Simona; Pittaluga, Anna Maria; Usai, Cesare; Gallus, Lorenzo; Ferrando, Sara; Milanese, Marco; Faimali, Marco; Bonanno, Giambattista

2014-02-01

Paramecium primaurelia is a unicellular eukaryote that moves in freshwater by ciliary beating and responds to environmental stimuli by altering motile behaviour. The movements of the cilia are controlled by the electrical changes of the cell membrane: when the intraciliary Ca(2+) concentration associated with plasma membrane depolarization increases, the ciliary beating reverses its direction, and consequently the swimming direction changes. The ciliary reversal duration is correlated with the amount of Ca(2+) influx. Here, we evaluated the effects due to the activation or blockade of N-methyl-d-aspartic acid (NMDA) receptors on swimming behaviour in Paramecium. Paramecia normally swim forward, drawing almost linear tracks. We observed that the simultaneous administration of NMDA and glycine induced a partial ciliary reversal (PaCR) leading to a continuous spiral-like swim. Furthermore, the duration of continuous ciliary reversal (CCR), triggered by high external KCl concentrations, was longer in NMDA+glycine-treated cells. NMDA action required the presence of Ca(2+), as the normal forward swimming was restored when the ion was omitted from the extracellular milieu. The PaCR and the enhancement of CCR duration significantly decreased when the antagonists of the glutamate site D-AP5 or CGS19755, the NMDA channel blocker MK-801 or the glycine site antagonist DCKA was added. The action of NMDA+glycine was also abolished by Zn(2+) or ifenprodil, the GluN2A and the GluN2B NMDA-containing subunit blockers, respectively. Searches of the Paramecium genome database currently available indicate that the NMDA-like receptor with ligand-binding characteristics of an NMDA receptor-like complex, purified from rat brain synaptic membranes and found in some metazoan genomes, is also present in Paramecium. These results provide evidence that functional NMDA receptors similar to those typical of mammalian neuronal cells are present in the single-celled organism Paramecium and thus suggest that the glutamatergic NMDA system is a phylogenetically old behaviour-controlling mechanism.

NMDA Receptors as Potential Therapeutic Targets in Diabetic Nephropathy: Increased Renal NMDA Receptor Subunit Expression in Akita Mice and Reduced Nephropathy Following Sustained Treatment With Memantine or MK-801.

PubMed

Roshanravan, Hila; Kim, Eun Young; Dryer, Stuart E

2016-10-01

N-methyl-d-aspartate (NMDA) receptors are expressed throughout the kidney, and the abundance of these receptors and some of their endogenous agonists are increased in diabetes. Moreover, sustained activation of podocyte NMDA receptors induces Ca(2+) influx, oxidative stress, loss of slit diaphragm proteins, and apoptosis. We observed that NMDA receptor subunits and their transcripts are increased in podocytes and mesangial cells cultured in elevated glucose compared with controls. A similar increase in NMDA subunits, especially NR1, NR2A, and NR2C, was observed in glomeruli and tubules of Akita mice. Sustained continuous treatment with the strong NMDA receptor antagonist dizocilpine (MK-801) for 28 days starting at 8 weeks of age reduced 24-h albumin excretion and mesangial matrix expansion and improved glomerular ultrastructure in Akita mice. MK-801 did not alleviate reduced Akita mouse body weight and had no effect on kidney histology or ultrastructure in DBA/2J controls. The structurally dissimilar NMDA antagonist memantine also reduced diabetic nephropathy, although it was less effective than MK-801. Inhibition of NMDA receptors may represent a valid therapeutic approach to reduce renal complications of diabetes, and it is possible to develop well-tolerated agents with minimal central nervous system effects. Two such agents, memantine and dextromethorphan, are already in widespread clinical use. © 2016 by the American Diabetes Association.

Trigeminal Medullary Dorsal Horn Neurons Activated by Nasal Stimulation Coexpress AMPA, NMDA, and NK1 Receptors

PubMed Central

McCulloch, P. F.; DiNovo, K. M.; Westerhaus, D. J.; Vizinas, T. A.; Peevey, J. F.; Lach, M. A.; Czarnocki, P.

2013-01-01

Afferent information initiating the cardiorespiratory responses during nasal stimulation projects from the nasal passages to neurons within the trigeminal medullary dorsal horn (MDH) via the anterior ethmoidal nerve (AEN). Central AEN terminals are thought to release glutamate to activate the MDH neurons. This study was designed to determine which neurotransmitter receptors (AMPA, kainate, or NMDA glutamate receptor subtypes or the Substance P receptor NK1) are expressed by these activated MDH neurons. Fos was used as a neuronal marker of activated neurons, and immunohistochemistry combined with epifluorescent microscopy was used to determine which neurotransmitter receptor subunits were coexpressed by activated MDH neurons. Results indicate that, during nasal stimulation with ammonia vapors in urethane-anesthetized Sprague-Dawley rats, activated neurons within the superficial MDH coexpress the AMPA glutamate receptor subunits GluA1 (95.8%) and GluA2/3 (88.2%), the NMDA glutamate receptor subunits GluN1 (89.1%) and GluN2A (41.4%), and NK1 receptors (64.0%). It is therefore likely that during nasal stimulation the central terminals of the AEN release glutamate and substance P that then produces activation of these MDH neurons. The involvement of AMPA and NMDA receptors may mediate fast and slow neurotransmission, respectively, while NK1 receptor involvement may indicate activation of a nociceptive pathway. PMID:24967301

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

Activation of NMDA receptor by elevated homocysteine in chronic liver disease contributes to encephalopathy.

PubMed

Choudhury, Sabanum; Borah, Anupom

2015-07-01

Liver diseases lead to a complex syndrome characterized by neurological, neuro-psychiatric and motor complications, called hepatic encephalopathy, which is prevalent in patients and animal models of acute, sub-chronic and chronic liver failure. Although alterations in GABAergic, glutamatergic, cholinergic and serotonergic neuronal functions have been implicated in HE, the molecular mechanisms that lead to HE in chronic liver disease (CLD) is least illustrated. Due to hepatocellular failure, levels of ammonia and homocysteine (Hcy), in addition to others, are found to increase in the brain as well as plasma. Hcy, a non-protein forming amino acid and an excitotoxin, activates ionotropic glutamate (n-methyl-d-aspartate; NMDA) receptors, and thereby leads to influx of Ca(2+) into neurons, which in turn activates several pathways that trigger oxidative stress, inflammation and apoptosis, collectively called excitotoxicity. Elevated levels of Hcy in the plasma and brain, a condition called Hyperhomocysteinemia (HHcy), and the resultant NMDA receptor-mediated excitotoxicity has been implicated in several diseases, including Parkinson's disease and Alzheimer's disease. Although, hyperammonemia has been shown to cause excitotoxicity, the role of HHcy in the development of behavioral and neurochemical alterations that occur in HE has not been illustrated yet. It is hypothesized that CLD-induced HHcy plays a major role in the development of HE through activation of NMDA receptors. It is further hypothesized that HHcy synergizes with hyperammonemia to activate NMDA receptor in the brain, and thereby cause oxidative stress, inflammation and apoptosis, and neuronal loss that leads to HE. Copyright © 2015 Elsevier Ltd. All rights reserved.

(+)-Pentazocine Reduces NMDA-Induced Murine Retinal Ganglion Cell Death Through a σR1-Dependent Mechanism

PubMed Central

Zhao, Jing; Mysona, Barbara A.; Qureshi, Azam; Kim, Lily; Fields, Taylor; Gonsalvez, Graydon B.; Smith, Sylvia B.; Bollinger, Kathryn E.

2016-01-01

Purpose To evaluate, in vivo, the effects of the sigma-1 receptor (σR1) agonist, (+)-pentazocine, on N-methyl-D-aspartate (NMDA)-mediated retinal excitotoxicity. Methods Intravitreal NMDA injections were performed in C57BL/6J mice (wild type [WT]) and σR1−/− (σR1 knockout [KO]) mice. Fellow eyes were injected with phosphate-buffered saline (PBS). An experimental cohort of WT and σR1 KO mice was administered (+)-pentazocine by intraperitoneal injection, and untreated animals served as controls. Retinas derived from mice were flat-mounted and labeled for retinal ganglion cells (RGCs). The number of RGCs was compared between NMDA and PBS-injected eyes for all groups. Apoptosis was assessed using TUNEL assay. Levels of extracellular-signal–regulated kinases (ERK1/2) were analyzed by Western blot. Results N-methyl-D-aspartate induced a significant increase in TUNEL-positive nuclei and a dose-dependent loss of RGCs. Mice deficient in σR1 showed greater RGC loss (≈80%) than WT animals (≈50%). (+)-Pentazocine treatment promoted neuronal survival, and this effect was prevented by deletion of σR1. (+)-Pentazocine treatment resulted in enhanced activation of ERK at the 6-hour time point following NMDA injection. The (+)-pentazocine–induced ERK activation was diminished in σR1 KO mice. Conclusions Targeting σR1 activation prevented RGC death while enhancing activation of the mitogen-activated protein kinase (MAPK), ERK1/2. Sigma-1 receptor is a promising therapeutic target for retinal neurodegenerative diseases. PMID:26868747

Interactions of Pannexin1 channels with purinergic and NMDA receptor channels.

PubMed

Li, Shuo; Bjelobaba, Ivana; Stojilkovic, Stanko S

2018-01-01

Pannexins are a three-member family of vertebrate plasma membrane spanning molecules that have homology to the invertebrate gap junction forming proteins, the innexins. However, pannexins do not form gap junctions but operate as plasma membrane channels. The best-characterized member of these proteins, Pannexin1 (Panx1) was suggested to be functionally associated with purinergic P2X and N-methyl-D-aspartate (NMDA) receptor channels. Activation of these receptor channels by their endogenous ligands leads to cross-activation of Panx1 channels. This in turn potentiates P2X and NMDA receptor channel signaling. Two potentiation concepts have been suggested: enhancement of the current responses and/or sustained receptor channel activation by ATP released through Panx1 pore and adenosine generated by ectonucleotidase-dependent dephosphorylation of ATP. Here we summarize the current knowledge and hypotheses about interactions of Panx1 channels with P2X and NMDA receptor channels. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve. Published by Elsevier B.V.

Differences in magnesium and calcium effects on N-methyl-D-aspartate- and quisqualate-induced decreases in extracellular sodium concentration in rat hippocampal slices.

PubMed

Köhr, G; Heinemann, U

1988-01-01

Decreases in extracellular sodium concentration [( Na+]o) and associated slow negative field potentials (fp's) were monitored with double barreled sodium sensitive/reference microelectrodes in area CA1 of rat hippocampal slices during iontophoretic application of the glutamate receptor agonists N-methyl-D-aspartate (NMDA) and quisqualate (quis). The effects of lowering [Ca2+]o on these signals were compared to those of lowering [Mg2+]o. Both NMDA- and quis-induced decreases in [Na+]o of up to 60 mM and in the fp's of up to 8 mV. Decreasing [Mg2+]o enhanced NMDA-induced signals, whereas quis-induced signals were unaffected. Lowering [Ca2+]o also enhanced NMDA signals, although somewhat less than lowering [Mg2+]o. This effect was still present, even when voltage dependent Na+ currents were blocked by 10(-7) tetrodotoxin. Interestingly, quis-induced signals could be enhanced in a low Ca2+ medium as well, but only when high quis concentrations were used. The results suggest that, during the sorts of large decreases of [Ca2+]o observed during seizure activity, activation of NMDA receptors is facilitated.

Targeting of glycine site on NMDA receptor as a possible new strategy for autism treatment.

PubMed

Ghanizadeh, Ahmad

2011-05-01

The exact pathophysiology of the neurodevelopment disorder of autism is not clear and there is not any curative approach for it. There is only one FDA-approved medication for its management. Therefore, providing of novel treatments is highly required. The hypofunction of GABAergic system and glutamate toxicity are generally believed to have a causal role for autism. The antagonist of the N-methyl-D-aspartic acid (NMDA) glutamate receptor improves autism. Glycine is required for the activation of NMDA receptor. The antagonist of glycine site decreases NMDA receptor conductance. It is hypothesis that glycine site antagonists can be tested as a new strategy for the management of autism.

The role of N-methyl-D-aspartate receptors and nitric oxide in cochlear dopamine release.

PubMed

Halmos, G; Horváth, T; Polony, G; Fekete, A; Kittel, A; Vizi, E S; van der Laan, B F A M; Zelles, T; Lendvai, B

2008-06-23

Dopamine (DA) released from lateral olivocochlear (LOC) terminals may have a neuroprotective effect in the cochlea. To explore the role of N-methyl-d-aspartate (NMDA) receptors and nitric oxide (NO) in the modulation of a cochlear DA release, we measured the release of [3H]DA from isolated mouse cochlea in response to the application of NMDA. NMDA at 100 muM significantly increased the electrical-field stimulation-evoked and resting release of DA from the cochlea. The NO donor sodium nitroprusside enhanced the basal outflow of DA but failed to influence the evoked release. The administration of the nitric oxide synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) alone was ineffective, but it significantly inhibited the initial phase of the NMDA-induced elevation of DA outflow, which suggested the role of NO in the NMDA-induced DA release. The DA uptake inhibitor nomifensine increased the electrically evoked release of DA. Nomifensine failed to change the effect of NMDA on the resting or electrically-evoked DA release, which suggested that the uptake mechanism does not play a role in NMDA-evoked and NO-mediated DA release. In summary, we provide evidence that NO can modulate the release of DA from the cochlea following NMDA receptor activation, but does not affect the uptake of DA.

Monosodium glutamate alters the response properties of rat trigeminovascular neurons through activation of peripheral NMDA receptors.

PubMed

O'Brien, Melissa; Cairns, Brian E

2016-10-15

Ingestion of monosodium glutamate (MSG) has been shown to cause headaches in healthy individuals and trigger migraine-like headaches in migraine sufferers. We combined immunohistochemistry, in vivo electrophysiology, and laser Doppler recordings of dural vasculature to investigate the effect of systemic administration of MSG on the trigeminovascular pathway. Immunohistochemical analysis confirmed the expression of NMDA receptors on nerve fibers innervating dural blood vessels and excitatory amino acid transporter 2 on dural blood vessels. Systemic administration of MSG (50mg/kg) evoked an increase in ongoing discharge in 5/6 spinal trigeminal subnucleus caudalis (SpVc) neurons with dural input recorded from male and female rats, respectively, as well as lowering their mechanical activation threshold. There were no sex-related differences in these effects of MSG. Neuronal discharge and mechanical sensitization were significantly attenuated by co-injection with the peripherally restricted NMDA receptor antagonist (2R)-amino-5-phosphonovaleric acid (APV) in both sexes. Systemic administration of MSG induced a 24.5% and 20.6% increase in dural flux in male and female rats, respectively. These results suggest that MSG-induced headache is mediated by the activation of peripheral NMDA receptors and subsequent dural vasodilation. Peripheral NMDA receptors are a potential target for the development of new drugs to treat headaches. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

Augmenting NMDA receptor signaling boosts experience-dependent neuroplasticity in the adult human brain

PubMed Central

Forsyth, Jennifer K.; Bachman, Peter; Mathalon, Daniel H.; Roach, Brian J.; Asarnow, Robert F.

2015-01-01

Experience-dependent plasticity is a fundamental property of the brain. It is critical for everyday function, is impaired in a range of neurological and psychiatric disorders, and frequently depends on long-term potentiation (LTP). Preclinical studies suggest that augmenting N-methyl-d-aspartate receptor (NMDAR) signaling may promote experience-dependent plasticity; however, a lack of noninvasive methods has limited our ability to test this idea in humans until recently. We examined the effects of enhancing NMDAR signaling using d-cycloserine (DCS) on a recently developed LTP EEG paradigm that uses high-frequency visual stimulation (HFvS) to induce neural potentiation in visual cortex neurons, as well as on three cognitive tasks: a weather prediction task (WPT), an information integration task (IIT), and a n-back task. The WPT and IIT are learning tasks that require practice with feedback to reach optimal performance. The n-back assesses working memory. Healthy adults were randomized to receive DCS (100 mg; n = 32) or placebo (n = 33); groups were similar in IQ and demographic characteristics. Participants who received DCS showed enhanced potentiation of neural responses following repetitive HFvS, as well as enhanced performance on the WPT and IIT. Groups did not differ on the n-back. Augmenting NMDAR signaling using DCS therefore enhanced activity-dependent plasticity in human adults, as demonstrated by lasting enhancement of neural potentiation following repetitive HFvS and accelerated acquisition of two learning tasks. Results highlight the utility of considering cellular mechanisms underlying distinct cognitive functions when investigating potential cognitive enhancers. PMID:26621715

NMDA receptor-antagonistic properties of hyperforin, a constituent of St. John's Wort.

PubMed

Kumar, Vikas; Mdzinarishvili, Alexander; Kiewert, Cornelia; Abbruscato, Thomas; Bickel, Ulrich; van der Schyf, Cornelis J; Klein, Jochen

2006-09-01

Extracts of the medicinal plant St. John's wort (Hypericum perforatum) are widely used for the treatment of affective disorders. Hyperforin, a constituent of St. John's wort, is known to modulate the release and re-uptake of various neurotransmitters, an action that likely underlies its antidepressive activity. We now report that hyperforin also has N-methyl-D-aspartate (NMDA)-antagonistic effects. Hyperforin (10 microM) was found to inhibit the NMDA-induced calcium influx into cortical neurons. In rat hippocampal slices, hyperforin inhibited the NMDA-receptor-mediated release of choline from phospholipids. Hyperforin also antagonized the increase of water content in freshly isolated hippocampal slices, and it counteracted, at 3 and 10 microM, the increase of water content induced by NMDA. Hyperforin was inactive, however, in two in vivo models of brain edema formation, middle cerebral artery occlusion and water intoxication in mice. In conclusion, hyperforin has NMDA-receptor-antagonistic and potential neuroprotective effects in vitro. This effect may contribute to the therapeutic effectiveness of St. John's wort extracts in some situations, for example, for relapse prevention in alcoholism.

Characterization of postsynaptic calcium signals in the pyramidal neurons of anterior cingulate cortex

PubMed Central

Li, Xu-Hui; Song, Qian; Chen, Tao; Zhuo, Min

2017-01-01

Calcium signaling is critical for synaptic transmission and plasticity. N-methyl-D-aspartic acid (NMDA) receptors play a key role in synaptic potentiation in the anterior cingulate cortex. Most previous studies of calcium signaling focus on hippocampal neurons, little is known about the activity-induced calcium signals in the anterior cingulate cortex. In the present study, we show that NMDA receptor-mediated postsynaptic calcium signals induced by different synaptic stimulation in anterior cingulate cortex pyramidal neurons. Single and multi-action potentials evoked significant suprathreshold Ca2+ increases in somas and spines. Both NMDA receptors and voltage-gated calcium channels contributed to this increase. Postsynaptic Ca2+signals were induced by puff-application of glutamate, and a NMDA receptor antagonist AP5 blocked these signals in both somas and spines. Finally, long-term potentiation inducing protocols triggered postsynaptic Ca2+ influx, and these influx were NMDA receptor dependent. Our results provide the first study of calcium signals in the anterior cingulate cortex and demonstrate that NMDA receptors play important roles in postsynaptic calcium signals in anterior cingulate cortex pyramidal neurons. PMID:28726541

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

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.

Inhibiting Src family tyrosine kinase activity blocks glutamate signalling to ERK1/2 and Akt/PKB but not JNK in cultured striatal neurones.

PubMed

Crossthwaite, Andrew J; Valli, Haseeb; Williams, Robert J

2004-03-01

Glutamate receptor activation of mitogen-activated protein (MAP) kinase signalling cascades has been implicated in diverse neuronal functions such as synaptic plasticity, development and excitotoxicity. We have previously shown that Ca2+-influx through NMDA receptors in cultured striatal neurones mediates the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt/protein kinase B (PKB) through a phosphatidylinositol 3-kinase (PI 3-kinase)-dependent pathway. Exposing neurones to the Src family tyrosine kinase inhibitor PP2, but not the inactive analogue PP3, inhibited NMDA receptor-induced phosphorylation of ERK1/2 and Akt/PKB in a concentration-dependent manner, and reduced cAMP response element-binding protein (CREB) phosphorylation. To establish a link between Src family tyrosine kinase-mediated phosphorylation and PI 3-kinase signalling, affinity precipitation experiments were performed with the SH2 domains of the PI 3-kinase regulatory subunit p85. This revealed a Src-dependent phosphorylation of a focal adhesion kinase (FAK)-p85 complex on glutamate stimulation. Demonstrating that PI3-kinase is not ubiquitously involved in NMDA receptor signal transduction, the PI 3-kinase inhibitors wortmannin and LY294002 did not prevent NMDA receptor Ca2+-dependent phosphorylation of c-Jun N-terminal kinase 1/2 (JNK1/2). Further, inhibiting Src family kinases increased NMDA receptor-dependent JNK1/2 phosphorylation, suggesting that Src family kinase-dependent cascades may physiologically limit signalling to JNK. These results demonstrate that Src family tyrosine kinases and PI3-kinase are pivotal regulators of NMDA receptor signalling to ERK/Akt and JNK in striatal neurones.

mTOR activation is required for the anti-alcohol effect of ketamine, but not memantine, in alcohol-preferring rats

PubMed Central

Sabino, Valentina; Narayan, Aditi R.; Zeric, Tamara; Steardo, Luca; Cottone, Pietro

2013-01-01

Glutamate NMDA receptors mediate many molecular and behavioral effects of alcohol, and they play a key role in the development of excessive drinking. Uncompetitive NMDA receptor antagonists may, therefore, have therapeutic potential for alcoholism. The first aim was to compare the effects of the NMDA antagonists memantine and ketamine on ethanol and saccharin drinking in alcohol-preferring rats. The second aim was to determine whether the effects of the two NMDA receptor antagonists were mediated by the mammalian target of rapamycin (mTOR). TSRI Sardinian alcohol-preferring rats were allowed to self-administer either 10% w/v ethanol or 0.08% w/v saccharin, and water. Operant responding and motor activity were assessed following administration of either memantine (0–10 mg/kg) or ketamine (0–20 mg/kg). Finally, ethanol self-administration was assessed in rats administered with either memantine or ketamine but pretreated with the mTOR inhibitor rapamycin (2.5 mg/kg). The uncompetitive NMDA receptor antagonists memantine and ketamine dose-dependently reduced ethanol drinking in alcohol-preferring rats; while memantine had a preferential effect on alcohol over saccharin, ketamine reduced responding for both solutions. Neither antagonist induced malaise, as shown by the lack of effect on water intake and motor activity. The mTOR inhibitor rapamycin blocked the effects of ketamine, but not those of memantine. Memantine and ketamine both reduce alcohol drinking in alcohol-preferring rats, but only memantine is selective for alcohol. The effects of ketamine, but not memantine, are mediated by mTOR. The results support the therapeutic potential of uncompetitive NMDA receptor antagonists, especially memantine, in alcohol addiction. PMID:23466691

Neuromodulation by Mg2+ and polyamines of excitatory amino acid currents in rodent neurones in culture.

PubMed

Kumamoto, E

1996-12-01

Excitatory amino-acid currents in rodent central neurones are mediated by the activation of glutamate receptors. Ionotropic types of the receptors are divided into alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), kainate and N-methyl-D-aspartate (NMDA) receptors, and the former two are collectively called non-NMDA receptors. The NMDA receptor is modulated by a number of endogenous neuromodulators including Mg2+, polyamines, glycine and protons in extracellular solutions. Although it has been generally thought that each of the neuromodulators acts on a distinct site in the NMDA receptor, recent studies have revealed that these actions may be not necessarily independent of each other. The NMDA receptor response is not only inhibited but also potentiated by Mg2+, and the latter action is due to an interaction of a Mg2+ site with either glycine- or proton-binding site. In the presence of polyamines, a tonic inhibition by protons of the NMDA receptor response is relieved, resulting in a potentiation of the response. Alternatively, it has been recently revealed that there are some subtypes of non-NMDA receptors which are negatively modulated by polyamines in either extra- or intra cellular solutions. The difference in polyamine sensitivity among non-NMDA receptors is attributed to a distinction in their constituted subunits. The inhibition of non-NMDA receptor by intracellular polyamines results in inward rectification of the current-voltage relation which is not seen for polyamine-insensitive ones. This polyamine action is not mimicked by intracellular Mg2+.

Revealing dynamically-organized receptor ion channel clusters in live cells by a correlated electric recording and super-resolution single-molecule imaging approach.

PubMed

Yadav, Rajeev; Lu, H Peter

2018-03-28

The N-methyl-d-aspartate (NMDA) receptor ion-channel is activated by the binding of ligands, along with the application of action potential, important for synaptic transmission and memory functions. Despite substantial knowledge of the structure and function, the gating mechanism of the NMDA receptor ion channel for electric on-off signals is still a topic of debate. We investigate the NMDA receptor partition distribution and the associated channel's open-close electric signal trajectories using a combined approach of correlating single-molecule fluorescence photo-bleaching, single-molecule super-resolution imaging, and single-channel electric patch-clamp recording. Identifying the compositions of NMDA receptors, their spatial organization and distributions over live cell membranes, we observe that NMDA receptors are organized inhomogeneously: nearly half of the receptor proteins are individually dispersed; whereas others exist in heterogeneous clusters of around 50 nm in size as well as co-localized within the diffraction limited imaging area. We demonstrate that inhomogeneous interactions and partitions of the NMDA receptors can be a cause of the heterogeneous gating mechanism of NMDA receptors in living cells. Furthermore, comparing the imaging results with the ion-channel electric current recording, we propose that the clustered NMDA receptors may be responsible for the variation in the current amplitude observed in the on-off two-state ion-channel electric signal trajectories. Our findings shed new light on the fundamental structure-function mechanism of NMDA receptors and present a conceptual advancement of the ion-channel mechanism in living cells.

Opiate physical dependence and N-methyl-D-aspartate receptors.

PubMed

Noda, Yukihiro; Nabeshima, Toshitaka

2004-10-01

The present review focused the involvement of N-methyl-D-aspartate (NMDA) receptors in morphine physical dependence. The increased levels of extracellular glutamate, NMDA receptor zeta subunit (NR1) mRNA, NMDA receptor epsilon 1 subunit (NR2A) protein, phosphorylated Ca(2+)/calmodulin kinase II (p-CaMKII) protein, c-fos mRNA, c-Fos protein, are observed in the specific brain areas of mice and/or rats showing signs of naloxone-precipitated withdrawal. In preclinical and clinical studies, a variety of NMDA receptor antagonists and pretreatment with an antisense oligonucleotide of the NR1 have been reported to inhibit the development, expression and/or maintenance of opiate physical dependence. In contrast to data obtained in adult animals, NMDA receptor antagonists are neither effective in blocking the development of opiate dependence nor the expression of opiate withdrawal in neonatal rats. In the NMDA receptor-deficient mice, the NR2A knockout mice show the marked loss of typical withdrawal abstinence behaviors precipitated by naloxone. The rescue of NR2A protein by electroporation into the nucleus accumbens of NR2A knockout mice reverses the loss of abstinence behaviors. The activation of CaMKII and increased expression of c-Fos protein in the brain of animals with naloxone-precipitated withdrawal syndrome are prevented by NMDA receptor antagonists, whereas the increased levels of extracellular glutamate are not prevented by them. These findings indicate that glutamatergic neurotransmission at the NMDA receptor site contributes to the development, expression and maintenance of opiate dependence, and suggest that NMDA receptor antagonists may be a useful adjunct in the treatment of opiate dependence.

Afferent specific role of NMDA receptors for the circuit integration of hippocampal neurogliaform cells.

PubMed

Chittajallu, R; Wester, J C; Craig, M T; Barksdale, E; Yuan, X Q; Akgül, G; Fang, C; Collins, D; Hunt, S; Pelkey, K A; McBain, C J

2017-07-28

Appropriate integration of GABAergic interneurons into nascent cortical circuits is critical for ensuring normal information processing within the brain. Network and cognitive deficits associated with neurological disorders, such as schizophrenia, that result from NMDA receptor-hypofunction have been mainly attributed to dysfunction of parvalbumin-expressing interneurons that paradoxically express low levels of synaptic NMDA receptors. Here, we reveal that throughout postnatal development, thalamic, and entorhinal cortical inputs onto hippocampal neurogliaform cells are characterized by a large NMDA receptor-mediated component. This NMDA receptor-signaling is prerequisite for developmental programs ultimately responsible for the appropriate long-range AMPAR-mediated recruitment of neurogliaform cells. In contrast, AMPAR-mediated input at local Schaffer-collateral synapses on neurogliaform cells remains normal following NMDA receptor-ablation. These afferent specific deficits potentially impact neurogliaform cell mediated inhibition within the hippocampus and our findings reveal circuit loci implicating this relatively understudied interneuron subtype in the etiology of neurodevelopmental disorders characterized by NMDA receptor-hypofunction.Proper brain function depends on the correct assembly of excitatory and inhibitory neurons into neural circuits. Here the authors show that during early postnatal development in mice, NMDAR signaling via activity of long-range synaptic inputs onto neurogliaform cells is required for their appropriate integration into the hippocampal circuitry.

Selective enhancement of NMDA receptor-mediated locomotor hyperactivity by male sex hormones in mice.

PubMed

van den Buuse, Maarten; Low, Jac Kee; Kwek, Perrin; Martin, Sally; Gogos, Andrea

2017-09-01

Altered glutamate NMDA receptor function is implicated in schizophrenia, and gender differences have been demonstrated in this illness. This study aimed to investigate the interaction of gonadal hormones with NMDA receptor-mediated locomotor hyperactivity and PPI disruption in mice. The effect of 0.25 mg/kg of MK-801 on locomotor activity was greater in male mice than in female mice. Gonadectomy (by surgical castration) significantly reduced MK-801-induced hyperlocomotion in male mice, but no effect of gonadectomy was seen in female mice or on amphetamine-induced locomotor hyperactivity. The effect of MK-801 on prepulse inhibition of startle (PPI) was similar in intact and castrated male mice and in ovariectomized (OVX) female mice. In contrast, there was no effect of MK-801 on PPI in intact female mice. Forebrain NMDA receptor density, as measured with [ 3 H]MK-801 autoradiography, was significantly higher in male than in female mice but was not significantly altered by either castration or OVX. These results suggest that male sex hormones enhance the effect of NMDA receptor blockade on psychosis-like behaviour. This interaction was not seen in female mice and was independent of NMDA receptor density in the forebrain. Male sex hormones may be involved in psychosis by an interaction with NMDA receptor hypofunction.

Retrieval-induced NMDA receptor-dependent Arc expression in two models of cocaine-cue memory.

PubMed

Alaghband, Yasaman; O'Dell, Steven J; Azarnia, Siavash; Khalaj, Anna J; Guzowski, John F; Marshall, John F

2014-12-01

The association of environmental cues with drugs of abuse results in persistent drug-cue memories. These memories contribute significantly to relapse among addicts. While conditioned place preference (CPP) is a well-established paradigm frequently used to examine the modulation of drug-cue memories, very few studies have used the non-preference-based model conditioned activity (CA) for this purpose. Here, we used both experimental approaches to investigate the neural substrates of cocaine-cue memories. First, we directly compared, in a consistent setting, the involvement of cortical and subcortical brain regions in cocaine-cue memory retrieval by quantifying activity-regulated cytoskeletal-associated (Arc) protein expression in both the CPP and CA models. Second, because NMDA receptor activation is required for Arc expression, we investigated the NMDA receptor dependency of memory persistence using the CA model. In both the CPP and CA models, drug-paired animals showed significant increases in Arc immunoreactivity in regions of the frontal cortex and amygdala compared to unpaired controls. Additionally, administration of a NMDA receptor antagonist (MK-801 or memantine) immediately after cocaine-CA memory reactivation impaired the subsequent conditioned locomotion associated with the cocaine-paired environment. The enhanced Arc expression evident in a subset of corticolimbic regions after retrieval of a cocaine-context memory, observed in both the CPP and CA paradigms, likely signifies that these regions: (i) are activated during retrieval of these memories irrespective of preference-based decisions, and (ii) undergo neuroplasticity in order to update information about cues previously associated with cocaine. This study also establishes the involvement of NMDA receptors in maintaining memories established using the CA model, a characteristic previously demonstrated using CPP. Overall, these results demonstrate the utility of the CA model for studies of cocaine-context memory and suggest the involvement of an NMDA receptor-dependent Arc induction pathway in drug-cue memory interference. Copyright © 2014 Elsevier Inc. All rights reserved.

Retrieval-induced NMDA receptor-dependent Arc expression in two models of cocaine-cue memory

PubMed Central

Alaghband, Yasaman; O'Dell, Steven J.; Azarnia, Siavash; Khalaj, Anna J.; Guzowski, John F.; Marshall, John F.

2014-01-01

The association of environmental cues with drugs of abuse results in persistent drug-cue memories. These memories contribute significantly to relapse among addicts. While conditioned place preference (CPP) is a well-established paradigm frequently used to examine the modulation of drug-cue memories, very few studies have used the non-preference-based model conditioned activity (CA) for this purpose. Here, we used both experimental approaches to investigate the neural substrates of cocaine-cue memories. First, we directly compared, in a consistent setting, the involvement of cortical and subcortical brain regions in cocaine-cue memory retrieval by quantifying activity-regulated cytoskeletal associated gene (Arc) protein expression in both the CPP and CA models. Second, because NMDA receptor activation is required for Arc expression, we investigated the NMDA receptor dependency of memory persistence using the CA model. In both the CPP and CA models, drug-paired animals showed significant increases in Arc immunoreactivity in regions of the frontal cortex and amygdala compared to unpaired controls. Additionally, administration of a NMDA receptor antagonist (MK-801 or memantine) immediately after cocaine-CA memory reactivation impaired the subsequent conditioned locomotion associated with the cocaine-paired environment. The enhanced Arc expression evident in a subset of corticolimbic regions after retrieval of a cocaine-context memory, observed in both the CPP and CA paradigms, likely signifies that these regions: (i) are activated during retrieval of these memories irrespective of preference-based decisions, and (ii) undergo neuroplasticity in order to update information about cues previously associated with cocaine. This study also establishes the involvement of NMDA receptors in maintaining memories established using the CA model, a characteristic previously demonstrated using CPP. Overall, these results demonstrate the utility of the CA model for studies of cocaine-context memory and suggest the involvement of an NMDA receptor-dependent Arc induction pathway in drug-cue memory interference. PMID:25225165

In Vitro Stretch Injury Induces Time- and Severity-Dependent Alterations of STEP Phosphorylation and Proteolysis in Neurons

PubMed Central

Mesfin, Mahlet N.; von Reyn, Catherine R.; Mott, Rosalind E.; Putt, Mary E.

2012-01-01

Abstract Striatal-enriched tyrosine phosphatase (STEP) has been identified as a component of physiological and pathophysiological signaling pathways mediated by N-methyl-d-aspartate (NMDA) receptor/calcineurin/calpain activation. Activation of these pathways produces a subsequent change in STEP isoform expression or activation via dephosphorylation. In this study, we evaluated changes in STEP phosphorylation and proteolysis in dissociated cortical neurons after sublethal and lethal mechanical injury using an in vitro stretch injury device. Sublethal stretch injury produces minimal changes in STEP phosphorylation at early time points, and increased STEP phosphorylation at 24 h that is blocked by the NMDA-receptor antagonist APV, the calcineurin-inhibitor FK506, and the sodium channel blocker tetrodotoxin. Lethal stretch injury produces rapid STEP dephosphorylation via NR2B-containing NMDA receptors, but not calcineurin, and a subsequent biphasic phosphorylation pattern. STEP61 expression progressively increases after sublethal stretch with no change in calpain-mediated STEP33 formation, while lethal stretch injury results in STEP33 formation via a NR2B-containing NMDA receptor pathway within 1 h of injury. Blocking calpain activation in the initial 30 min after stretch injury increases the ratio of active STEP in cells and blocks STEP33 formation, suggesting that STEP is an early substrate of calpain after mechanical injury. There is a strong correlation between the amount of STEP33 formed and the degree of cell death observed after lethal stretch injury. In summary, these data demonstrate that previously characterized pathways of STEP regulation via the NMDA receptor are generally conserved in mechanical injury, and suggest that calpain-mediated cleavage of STEP33 should be further examined as an early marker of neuronal fate after stretch injury. PMID:22435660

Metabotropic glutamate receptor 5 upregulates surface NMDA receptor expression in striatal neurons via CaMKII.

PubMed

Jin, Dao-Zhong; Xue, Bing; Mao, Li-Min; Wang, John Q

2015-10-22

Metabotropic and ionotropic glutamate receptors are closely clustered in postsynaptic membranes and are believed to interact actively with each other to control excitatory synaptic transmission. Metabotropic glutamate receptor 5 (mGluR5), for example, has been well documented to potentiate ionotropic NMDA receptor activity, although underlying mechanisms are poorly understood. In this study, we investigated the role of mGluR5 in regulating trafficking and subcellular distribution of NMDA receptors in adult rat striatal neurons. We found that the mGluR1/5 agonist DHPG concentration-dependently increased NMDA receptor GluN1 and GluN2B subunit expression in the surface membrane. Meanwhile, DHPG reduced GluN1 and GluN2B levels in the intracellular compartment. The effect of DHPG was blocked by an mGluR5 selective antagonist MTEP but not by an mGluR1 selective antagonist 3-MATIDA. Pretreatment with an inhibitor or a specific inhibitory peptide for synapse-enriched Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) also blocked the DHPG-stimulated redistribution of GluN1 and GluN2B. In addition, DHPG enhanced CaMKIIα activity and elevated GluN2B phosphorylation at a CaMKII-sensitive site (serine 1303). These results demonstrate that mGluR5 regulates trafficking of NMDA receptors in striatal neurons. Activation of mGluR5 appears to induce rapid trafficking of GluN1 and GluN2B to surface membranes through a signaling pathway involving CaMKII. Copyright © 2015 Elsevier B.V. All rights reserved.

Oxidative stress induced NMDA receptor alteration leads to spatial memory deficits in temporal lobe epilepsy: ameliorative effects of Withania somnifera and Withanolide A.

PubMed

Soman, Smijin; Korah, P K; Jayanarayanan, S; Mathew, Jobin; Paulose, C S

2012-09-01

In the present study we investigate the effect of Withania somnifera (WS) root extract and Withanolide A (WA) in restoring spatial memory deficit by inhibiting oxidative stress induced alteration in glutamergic neurotransmission. We demonstrate significant cellular loss in hippocampus of epileptic rats, visualized through decreased TOPRO stained neurons. Impaired spatial memory was observed in epileptic rats after Radial arm maze test. Treatment with WS and WA has resulted in increased number of TOPRO stained neurons. Enhanced performance of epileptic rats treated with WS and WA was observed in Radial arm maze test. The antioxidant activity of WS and WA was studied using superoxide dismutase (SOD) and Catalase (CAT) assays in the hippocampus of experimental rats. The SOD activity and CAT activity decreased significantly in epileptic group, treatment with WS and WA significantly reversed the enzymatic activities to near control. Real time gene expression studies of SOD and GPx showed significant up-regulation in epileptic group compared to control. Treatment with WS and WA showed significant reversal to near control. Lipid peroxidation quantified using TBARS assay, significantly increased in epileptic rats. Treatment with WS and WA showed significant reversal to near control. NMDA receptor expression decreased in epileptic rats. The treatment with WS and WA resulted in physiological expression of NMDA receptors. This data suggests that oxidative stress effects membrane constitution resulting in decreased NMDA receptor density leading to impaired spatial memory. Treatment with WS and WA has ameliorated spatial memory deficits by enhancing antioxidant system and restoring altered NMDA receptor density.

The effect of the NMDA receptor blocker, dextromethorphan, on cribbing in horses.

PubMed

Rendon, R A; Shuster, L; Dodman, N H

2001-01-01

Stereotypic cribbing in horses is thought to involve excess dopaminergic activity within the striatum. Various models of stress-induced stereotypies including cribbing in horses postulate that stress stimulates the release of endorphins, triggering the release of striatal dopamine. Dopamine in turn activates basal ganglia motor programs, reinforcing behavior via a reward mechanism. Furthermore, the release of dopamine by endorphins has been shown to depend on activation of NMDA receptors. In the present study, horses identified as cribbers and volunteered by their owners were treated with the NMDA receptor antagonist dextromethorphan (DM). When DM was administered via jugular injection (1 mg/kg), eight of nine horses responded with reductions in cribbing rate (CR) compared to baseline, and cribbing was suppressed completely for a period of time in almost half of the horses tested.

Group II Metabotropic Glutamate Receptor Agonist Ameliorates MK801-Induced Dysfunction of NMDA Receptors via the Akt/GSK-3β Pathway in Adult Rat Prefrontal Cortex

PubMed Central

Xi, Dong; Li, Yan-Chun; Snyder, Melissa A; Gao, Ruby Y; Adelman, Alicia E; Zhang, Wentong; Shumsky, Jed S; Gao, Wen-Jun

2011-01-01

Pharmacological intervention targeting mGluRs has emerged as a potential treatment for schizophrenia, whereas the mechanisms involved remain elusive. We explored the antipsychotic effects of an mGluR2/3 agonist in the MK-801 model of schizophrenia in the rat prefrontal cortex. We found that the mGluR2/3 agonist LY379268 effectively recovered the disrupted expression of NMDA receptors induced by MK-801 administration. This effect was attributable to the direct regulatory action of LY379268 on NMDA receptors via activation of the Akt/GSK-3β signaling pathway. As occurs with the antipsychotic drug clozapine, acute treatment with LY379268 significantly increased the expression and phosphorylation of NMDA receptors, as well as Akt and GSK-3β. Physiologically, LY379268 significantly enhanced NMDA-induced current in prefrontal neurons and a GSK-3β inhibitor occluded this effect. In contrast to the widely proposed mechanism of modulating presynaptic glutamate release, our results strongly argue that mGluR2/3 agonists modulate the function of NMDA receptors through postsynaptic actions and reverse the MK-801-induced NMDA dysfunction via the Akt/GSK-3β pathway. This study provides novel evidence for postsynaptic mechanisms of mGluR2/3 in regulation of NMDA receptors and presents useful insights into the mechanistic actions of mGluR2/3 agonists as potential antipsychotic agents for treating schizophrenia. PMID:21326193

Effect of clozapine on locomotor activity and anxiety-related behavior in the neonatal mice administered MK-801.

PubMed

Pınar, Neslihan; Akillioglu, Kubra; Sefil, Fatih; Alp, Harun; Sagir, Mustafa; Acet, Ahmet

2015-08-11

Atypical antipsychotics have been used to treat fear and anxiety disturbance that are highly common in schizophrenic patients. It is suggested that disruptions of N-methyl-d-aspartate (NMDA)-mediated transmission of glutamate may underlie the pathophysiology of schizophrenia. The present study was conducted to analyze the effectiveness of clozapine on the anxiety-related behavior and locomotor function of the adult brain, which had previously undergone NMDA receptor blockade during a developmental period. In order to block the NMDA receptor, male mice were administered 0.25 mg/kg of MK-801 on days 7 to 10 postnatal. In adulthood, they were administered intraperitoneally 0.5 mg/kg of clozapine and tested with open-field and elevated plus maze test, to assess their emotional behavior and locomotor activity. In the group receiving MK-801 in the early developmental period the elevated plus maze test revealed a reduction in the anxiety-related behavior (p<0.05), while the open-field test indicated a decrease in locomotor activity (p<0.01). Despite these reductions, clozapine could not reverse the NMDA receptor blockade. Also, as an atypical antipsychotic agent, clozapine could not reverse impairment in the locomotor activity and anxiety-related behavior, induced by administration of the MK-801 in neonatal period.

Effect of clozapine on locomotor activity and anxiety-related behavior in the neonatal mice administered MK-801

PubMed Central

Pinar, Neslihan; Akillioglu, Kubra; Sefil, Fatih; Alp, Harun; Sagir, Mustafa; Acet, Ahmet

2015-01-01

Atypical antipsychotics have been used to treat fear and anxiety disturbance that are highly common in schizophrenic patients. It is suggested that disruptions of N-methyl-d-aspartate (NMDA)-mediated transmission of glutamate may underlie the pathophysiology of schizophrenia. The present study was conducted to analyze the effectiveness of clozapine on the anxiety-related behavior and locomotor function of the adult brain, which had previously undergone NMDA receptor blockade during a developmental period. In order to block the NMDA receptor, male mice were administered 0.25 mg/kg of MK-801 on days 7 to 10 postnatal. In adulthood, they were administered intraperitoneally 0.5 mg/kg of clozapine and tested with open-field and elevated plus maze test, to assess their emotional behavior and locomotor activity. In the group receiving MK-801 in the early developmental period the elevated plus maze test revealed a reduction in the anxiety-related behavior (p<0.05), while the open-field test indicated a decrease in locomotor activity (p<0.01). Despite these reductions, clozapine could not reverse the NMDA receptor blockade. Also, as an atypical antipsychotic agent, clozapine could not reverse impairment in the locomotor activity and anxiety-related behavior, induced by administration of the MK-801 in neonatal period. PMID:26295298

An extension of hypotheses regarding rapid-acting, treatment-refractory, and conventional antidepressant activity of dextromethorphan and dextrorphan.

PubMed

Lauterbach, Edward C

2012-06-01

It was previously hypothesized that dextromethorphan (DM) and dextrorphan (DX) may possess antidepressant properties, including rapid and conventional onsets of action and utility in treatment-refractory depression, based on pharmacodynamic similarities to ketamine. These similarities included sigma-1 (σ(1)) agonist and NMDA antagonist properties, calcium channel blockade, muscarinic binding, serotonin transporter (5HTT) inhibition, and μ receptor potentiation. Here, six specific hypotheses are developed in light of additional mechanisms and evidence. Comparable potencies to ketamine for DM and DX are detailed for σ(1) (DX>DM>ketamine), NMDA PCP site (DX>ketamine>DM), and muscarinic (DX>ketamine>DM) receptors, 5HTT (DM>DX≫ketamine), and NMDA antagonist potentiation of μ receptor stimulation (DM>ketamine). Rapid acting antidepressant properties of DM include NMDA high-affinity site, NMDR-2A, and functional NMDR-2B receptor antagonism, σ(1) stimulation, putative mTOR activation (by σ(1) stimulation, μ potentiation, and 5HTT inhibition), putative AMPA receptor trafficking (by mTOR activation, PCP antagonism, σ(1) stimulation, μ potentiation, and 5HTT inhibition), and dendritogenesis, spinogenesis, synaptogenesis, and neuronal survival by NMDA antagonism and σ(1) and mTOR signaling. Those for dextrorphan include NMDA high-affinity site and NMDR-2A antagonism, σ(1) stimulation, putative mTOR activation (by σ(1) stimulation and ß adrenoreceptor stimulation), putative AMPA receptor trafficking (by mTOR activation, PCP antagonism, σ(1) stimulation, ß stimulation, and μ antagonism), and dendritogenesis, spinogenesis, synaptogenesis, and neuronal survival by NMDA antagonism and σ(1) and mTOR signaling. Conventional antidepressant properties for dextromethorphan and dextrorphan include 5HTT and norepinephrine transporter inhibition, σ(1) stimulation, NMDA and PCP antagonism, and possible serotonin 5HT1b/d receptor stimulation. Additional properties for dextromethorphan include possible presynaptic α(2) adrenoreceptor antagonism or postsynaptic α(2) stimulation and, for dextrorphan, ß stimulation and possible muscarinic and μ antagonism. Treatment-refractory depression properties include increased serotonin and norepinephrine availability, PCP, NMDR-2B, presynaptic alpha-2 antagonism, and the multiplicity of other antidepressant receptor mechanisms. Suggestions for clinical trials are provided for oral high-dose dextromethorphan and Nuedexta (dextromethorphan combined with quinidine to block metabolism to dextrorphan, thereby increasing dextromethorphan plasma concentrations). Suggestions include exclusionary criteria, oral dosing, observation periods, dose-response approaches, and safety and tolerability are considered. Although oral dextromethorphan may be somewhat more likely to show efficacy through complementary antidepressant mechanisms of dextrorphan, a clinical trial will be more logistically complex than one of Nuedexta due to high doses and plasma level variability. Clinical trials may increase our therapeutic armamentarium and our pharmacological understanding of treatment-refractory depression and antidepressant onset of action. Copyright © 2012 Elsevier Ltd. All rights reserved.

Single-Molecule Patch-Clamp FRET Anisotropy Microscopy Studies of NMDA Receptor Ion Channel Activation and Deactivation under Agonist Ligand Binding in Living Cells.

PubMed

Sasmal, Dibyendu Kumar; Yadav, Rajeev; Lu, H Peter

2016-07-20

N-methyl-d-aspartate (NMDA) receptor ion channel is activated by the binding of two pairs of glycine and glutamate along with the application of action potential. Binding and unbinding of ligands changes its conformation that plays a critical role in the open-close activities of NMDA receptor. Conformation states and their dynamics due to ligand binding are extremely difficult to characterize either by conventional ensemble experiments or single-channel electrophysiology method. Here we report the development of a new correlated technical approach, single-molecule patch-clamp FRET anisotropy imaging and demonstrate by probing the dynamics of NMDA receptor ion channel and kinetics of glycine binding with its ligand binding domain. Experimentally determined kinetics of ligand binding with receptor is further verified by computational modeling. Single-channel patch-clamp and four-channel fluorescence measurement are recorded simultaneously to get correlation among electrical on and off states, optically determined conformational open and closed states by FRET, and binding-unbinding states of the glycine ligand by anisotropy measurement at the ligand binding domain of GluN1 subunit. This method has the ability to detect the intermediate states in addition to electrical on and off states. Based on our experimental results, we have proposed that NMDA receptor gating goes through at least one electrically intermediate off state, a desensitized state, when ligands remain bound at the ligand binding domain with the conformation similar to the fully open state.

Extreme delta brush evolving into status epilepticus in a patient with anti-NMDA encephalitis.

PubMed

Herlopian, Aline; Rosenthal, Eric S; Chu, Catherine J; Cole, Andrew J; Struck, Aaron F

2017-01-01

Extreme delta brush (EDB) is an EEG pattern unique to anti-NMDA encephalitis. It is correlated with seizures and status epilepticus in patients who have a prolonged course of illness. The etiology of the underlying association between EDB and seizures is not understood. We present a patient with anti-NMDA encephalitis who developed status epilepticus evolving from the high frequency activity of the extreme delta brush. This case demonstrates that EDB is not only a marker for a greater propensity for seizures but also directly implicated in seizure generation.

Interactions between ifenprodil and dizocilpine on mouse behaviour in models of anxiety and working memory.

PubMed

Fraser, C M; Cooke, M J; Fisher, A; Thompson, I D; Stone, T W

1996-11-01

The N-methyl-D-aspartate (NMDA) receptor polyamine site antagonist, ifenprodil, had no effect on spontaneous alteration or locomotor activity in the Y-maze when given alone. The NMDA receptor/ion channel blocker, dizocilpine, induced a deficit in spontaneous alteration, but when ifenprodil was co-administered with dizocilpine, it showed a strong tendency to attenuate the dizocilpine-induced deficit. In the plus-maze, ifenprodil had an anxiolytic profile which was accompanied by an increase in locomotion. Dizocilpine had an anxiolytic profile in this model and increased locomotor activity. When co-administered with dizocilpine, ifenprodil reduced both the anxiolytic and locomotor effects of dizocilpine. When co-administered with ifenprodil, cyclopentyladenosine (CPA) and 1,3-dipropyl-8-cyclopentylxanthine (CPX) reduced the anxiolytic effect of ifenprodil. CPA and CPX in combination did not reverse the anxiolytic effect of ifenpropil. It is concluded that NMDA antagonists with different sites of action can show distinct behavioural profiles, with dizocilpine but not ifenprodil inducing a deficit in working memory, while both are anxiolytic. Blockade of NMDA receptors by ifenprodil, however, can preclude any response to dizocilpine. The anxiolytic activity of ifenprodil may involve the release of purines acting at adenosine receptors.

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.

Evidence for the involvement of NMDA receptors in the antidepressant-like effect of nicotine in mouse forced swimming and tail suspension tests.

PubMed

Haj-Mirzaian, Arya; Kordjazy, Nastaran; Haj-Mirzaian, Arvin; Ostadhadi, Sattar; Ghasemi, Mehdi; Amiri, Shayan; Faizi, Mehrdad; Dehpour, AhmadReza

2015-10-01

The antidepressant action of acute nicotine administration in clinical and animal studies is well recognized. But the underlying mechanism for this effect has not been carefully discovered. We attempted to evaluate the possible role of N-Methyl-D-aspartate (NMDA) receptors in the antidepressant-like effect of nicotine. After the assessment of locomotor activity in the open-field test, forced swimming test (FST) and tail suspension test (TST) were used to evaluate the antidepressant-like effect of nicotine in mice. We performed intraperitoneal administration of nicotine at different doses and periods before the tests. To assess the possible involvement of NMDA receptors, non-effective doses of NMDA antagonists and an NMDA agonist were obtained and were administered simultaneously with the non-effective and effective doses of nicotine, respectively. Nicotine (0.2 mg/kg, 30 min before FST/TST) significantly reduced the immobility time of mice similar to fluoxetine (20 mg/kg). Nicotine did not affect the locomotor behavior of mice in open-field test. Co-administration of non-effective doses of NMDA receptor antagonists, ketamine (1 or 0.3 mg/kg), MK-801 (0.05 or 0.005 mg/kg), and magnesium sulfate (10 or 5 mg/kg) with nicotine (0.1 or 0.03 mg/kg) had remarkable synergistic antidepressant effect in both FST and TST. Also, non-effective NMDA (75 or 30 mg/kg) reversed the anti-immobility effect of nicotine (0.2 mg/kg) on mouse FST and TST. Our study has for the first time confirmed that the antidepressant-like effect of nicotine on mice is NMDA-mediated, and nicotine presumably exerts this effect by antagonizing the glutamatergic NMDA receptors.

A role for N-methyl-D-aspartate receptors in norepinephrine-induced long-lasting potentiation in the dentate gyrus.

PubMed

Stanton, P K; Mody, I; Heinemann, U

1989-01-01

Mechanisms of action of norepinephrine (NE) on dentate gyrus granule cells were studied in rat hippocampal slices using extra- and intracellular recordings and measurements of stimulus and amino acid-induced changes in extracellular Ca2+ and K+ concentration. Bath application of NE (10-50 microM) induced long-lasting potentiation of perforant path evoked potentials, and markedly enhanced high-frequency stimulus-induced Ca2+ influx and K+ efflux, actions blocked by beta-receptor antagonists and mimicked by beta agonists. Enhanced Ca2+ influx was primarily postsynaptic, since presynaptic delta [Ca2+]o in the stratum moleculare synaptic field was not altered by NE. Interestingly, the potentiation of both ionic fluxes and evoked population potentials were antagonized by the N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonovalerate (APV). Furthermore, NE selectively enhanced the delta [Ca2+]o delta [K+]o and extracellular slow negative field potentials elicited by iontophoretically applied NMDA, but not those induced by the excitatory amino acid quisqualate. These results suggest that granule cell influx of Ca2+ through NMDA ionophores is enhanced by NE via beta-receptor activation. In intracellular recordings, NE depolarized granule cells (4.8 +/- 1.1 mV), and increased input resistance (RN) by 34 +/- 6.5%. These actions were also blocked by either the beta-antagonist propranolol or specific beta 1-blocker metoprolol. Moreover, the depolarization and RN increase persisted for long periods (93 +/- 12 min) after NE washout. In contrast, while NE, in the presence of APV, still depolarized granule cells and increased RN, APV made these actions quickly reversible upon NE washout (16 +/- 9 min). This suggested that NE induction of long-term, but not short-term, plasticity in the dentate gyrus requires NMDA receptor activation. NE may be enhancing granule cell firing by some combination of blockade on the late Ca2+-activated K+ conductance and depolarization of granule cells, both actions that can bring granule cells into a voltage range where NMDA receptors are more easily activated. Furthermore, NE also elicited activity-independent long-lasting depolarization and RN increases, which required functional NMDA receptors to persist.

Memantine, an NMDA receptor antagonist, differentially influences Go/No-Go performance and fMRI activity in individuals with and without a family history of alcoholism

PubMed Central

DeVito, E. E.; Jiantonio, R. E.; Meda, S. A.; Stevens, M. C.; Potenza, M. N.; Krystal, J. H.; Pearlson, G. D.

2013-01-01

Rationale Individuals with a family history of alcoholism (family history positive [FHP]) show higher alcoholism rates and are more impulsive than those without such a family history (family history negative [FHN]), possibly due to altered N-methyl-D-aspartate (NMDA) receptor function. Objectives We investigated whether memantine, an NMDA receptor antagonist, differentially influences impulsivity measures and Go/No-Go behavior and fMRI activity in matched FHP and FHN individuals. Methods On separate days, participants received a single dose of 40 mg memantine or identical-appearing placebo. Results No group performance differences were observed on placebo for Go correct hit or No-Go false alarm reaction time on the Go/No-Go task. During fMRI, right cingulate activation differed for FHP vs. FHN subjects during No-Go correct rejects. Memantine had attenuated effects in FHP vs. FHN subjects: For No-Go false alarms, memantine was associated with limited reduction in subcortical, cingulate, and temporal regions in FHP subjects and reduced activity in fronto-striatal–parietal networks in FHN subjects. For No-Go correct rejects, memantine (relative to placebo) reduced activity in left cingulate and caudate in FHP but not FHN subjects. Conclusions Lower sensitivity to the effects of memantine in FHP subjects is consistent with greater NMDA receptor function in this group. PMID:22311382

NMDA receptor activation regulates sociability by its effect on mTOR signaling activity.

PubMed

Burket, Jessica A; Benson, Andrew D; Tang, Amy H; Deutsch, Stephen I

2015-07-03

Tuberous Sclerosis Complex is one example of a syndromic form of autism spectrum disorder associated with disinhibited activity of mTORC1 in neurons (e.g., cerebellar Purkinje cells). mTORC1 is a complex protein possessing serine/threonine kinase activity and a key downstream molecule in a signaling cascade beginning at the cell surface with the transduction of neurotransmitters (e.g., glutamate and acetylcholine) and nerve growth factors (e.g., Brain-Derived Neurotrophic Factor). Interestingly, the severity of the intellectual disability in Tuberous Sclerosis Complex may relate more to this metabolic disturbance (i.e., overactivity of mTOR signaling) than the density of cortical tubers. Several recent reports showed that rapamycin, an inhibitor of mTORC1, improved sociability and other symptoms in mouse models of Tuberous Sclerosis Complex and autism spectrum disorder, consistent with mTORC1 overactivity playing an important pathogenic role. NMDA receptor activation may also dampen mTORC1 activity by at least two possible mechanisms: regulating intraneuronal accumulation of arginine and the phosphorylation status of a specific extracellular signal regulating kinase (i.e., ERK1/2), both of which are "drivers" of mTORC1 activity. Conceivably, the prosocial effects of targeting the NMDA receptor with agonists in mouse models of autism spectrum disorders result from their ability to dampen mTORC1 activity in neurons. Strategies for dampening mTORC1 overactivity by NMDA receptor activation may be preferred to its direct inhibition in chronic neurodevelopmental disorders, such as autism spectrum disorders. Copyright © 2015 Elsevier Inc. All rights reserved.

Ion channels in EEG: isolating channel dysfunction in NMDA receptor antibody encephalitis.

PubMed

Symmonds, Mkael; Moran, Catherine H; Leite, M Isabel; Buckley, Camilla; Irani, Sarosh R; Stephan, Klaas Enno; Friston, Karl J; Moran, Rosalyn J

2018-06-01

See Roberts and Breakspear (doi:10.1093/brain/awy136) for a scientific commentary on this article.Neurological and psychiatric practice frequently lack diagnostic probes that can assess mechanisms of neuronal communication non-invasively in humans. In N-methyl-d-aspartate (NMDA) receptor antibody encephalitis, functional molecular assays are particularly important given the presence of NMDA antibodies in healthy populations, the multifarious symptomology and the lack of radiological signs. Recent advances in biophysical modelling techniques suggest that inferring cellular-level properties of neural circuits from macroscopic measures of brain activity is possible. Here, we estimated receptor function from EEG in patients with NMDA receptor antibody encephalitis (n = 29) as well as from encephalopathic and neurological patient controls (n = 36). We show that the autoimmune patients exhibit distinct fronto-parietal network changes from which ion channel estimates can be obtained using a microcircuit model. Specifically, a dynamic causal model of EEG data applied to spontaneous brain responses identifies a selective deficit in signalling at NMDA receptors in patients with NMDA receptor antibody encephalitis but not at other ionotropic receptors. Moreover, though these changes are observed across brain regions, these effects predominate at the NMDA receptors of excitatory neurons rather than at inhibitory interneurons. Given that EEG is a ubiquitously available clinical method, our findings suggest a unique re-purposing of EEG data as an assay of brain network dysfunction at the molecular level.

The effect of 1800MHz radio-frequency radiation on NMDA receptor subunit NR1 expression and peroxidation in the rat brain in healthy and inflammatory states.

PubMed

Bodera, Paweł; Makarova, Katerina; Zawada, Katarzyna; Antkowiak, Bożena; Paluch, Małgorzata; Sobiczewska, Elżbieta; Sirav, Bahriye; Siwicki, Andrzej K; Stankiewicz, Wanda

2017-08-01

The aim of this study was to evaluate the effect of repeated exposure (5 times for 15min) of 1800MHz radio-frequency radiation (RFR) on N-methyl-d-aspartate receptor subunit NR1 (NMDA-NR1) expression in the brains of rats in a persistent inflammatory state. We also measured the effect of RFR combined with tramadol (TRAM) to determine the potential antioxidant capacity of this agent. The effects of the Global System for Mobile Communication (GSM) modulated 1800MHz RFR exposure on the expression and activity of glutamate receptor channels with antioxidative activity in brain tissue was measured using oxygen radical absorbance capacity (ORAC) and electron spin resonance (ESR) detection of the hydroxyl radical generated by the Fenton reaction. NMDA-NR1 was measured in the cerebral tissue of rats with inflammation (complete Freund's adjuvent) and those injected with tramadol after RFR exposure (RFR, RFR/TRAM) and in non-exposed (baseline, TRAM) rats. No differences between the baseline group and the exposed group (RFR) were observed. NMDA-NR1 expression decreased after CFA injection and RFR exposure, and an elevated expression of NMDA-NR1 was observed in healthy control rats of both groups: TRAM/RFR and RFR. ORAC assessment revealed a robust effect of RFR, however the other experiments revealed equivocal effects. Further studies examining the combination of ORAC with NMDA are warranted to elucidate more clearly the effect of RFR on the brain. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

AMP-activated protein kinase (AMPK)-induced preconditioning in primary cortical neurons involves activation of MCL-1.

PubMed

Anilkumar, Ujval; Weisová, Petronela; Düssmann, Heiko; Concannon, Caoimhín G; König, Hans-Georg; Prehn, Jochen H M

2013-03-01

Neuronal preconditioning is a phenomenon where a previous exposure to a sub-lethal stress stimulus increases the resistance of neurons towards a second, normally lethal stress stimulus. Activation of the energy stress sensor, AMP-activated protein kinase (AMPK) has been shown to contribute to the protective effects of ischaemic and mitochondrial uncoupling-induced preconditioning in neurons, however, the molecular basis of AMPK-mediated preconditioning has been less well characterized. We investigated the effect of AMPK preconditioning using 5-aminoimidazole-4-carboxamide riboside (AICAR) in a model of NMDA-mediated excitotoxic injury in primary mouse cortical neurons. Activation of AMPK with low concentrations of AICAR (0.1 mM for 2 h) induced a transient increase in AMPK phosphorylation, protecting neurons against NMDA-induced excitotoxicity. Analysing potential targets of AMPK activation, demonstrated a marked increase in mRNA expression and protein levels of the anti-apoptotic BCL-2 family protein myeloid cell leukaemia sequence 1 (MCL-1) in AICAR-preconditioned neurons. Interestingly, over-expression of MCL-1 protected neurons against NMDA-induced excitotoxicity while MCL-1 gene silencing abolished the effect of AICAR preconditioning. Monitored intracellular Ca²⁺ levels during NMDA excitation revealed that MCL-1 over-expressing neurons exhibited improved bioenergetics and markedly reduced Ca²⁺ elevations, suggesting a potential mechanism through which MCL-1 confers neuroprotection. This study identifies MCL-1 as a key effector of AMPK-induced preconditioning in neurons. © 2012 International Society for Neurochemistry.

Extrasynaptic Glutamate Receptor Activation as Cellular Bases for Dynamic Range Compression in Pyramidal Neurons

PubMed Central

Oikonomou, Katerina D.; Short, Shaina M.; Rich, Matthew T.; Antic, Srdjan D.

2012-01-01

Repetitive synaptic stimulation overcomes the ability of astrocytic processes to clear glutamate from the extracellular space, allowing some dendritic segments to become submerged in a pool of glutamate, for a brief period of time. This dynamic arrangement activates extrasynaptic NMDA receptors located on dendritic shafts. We used voltage-sensitive and calcium-sensitive dyes to probe dendritic function in this glutamate-rich location. An excess of glutamate in the extrasynaptic space was achieved either by repetitive synaptic stimulation or by glutamate iontophoresis onto the dendrites of pyramidal neurons. Two successive activations of synaptic inputs produced a typical NMDA spike, whereas five successive synaptic inputs produced characteristic plateau potentials, reminiscent of cortical UP states. While NMDA spikes were coupled with brief calcium transients highly restricted to the glutamate input site, the dendritic plateau potentials were accompanied by calcium influx along the entire dendritic branch. Once initiated, the glutamate-mediated dendritic plateau potentials could not be interrupted by negative voltage pulses. Activation of extrasynaptic NMDA receptors in cellular compartments void of spines is sufficient to initiate and support plateau potentials. The only requirement for sustained depolarizing events is a surplus of free glutamate near a group of extrasynaptic receptors. Highly non-linear dendritic spikes (plateau potentials) are summed in a highly sublinear fashion at the soma, revealing the cellular bases of signal compression in cortical circuits. Extrasynaptic NMDA receptors provide pyramidal neurons with a function analogous to a dynamic range compression in audio engineering. They limit or reduce the volume of “loud sounds” (i.e., strong glutamatergic inputs) and amplify “quiet sounds” (i.e., glutamatergic inputs that barely cross the dendritic threshold for local spike initiation). Our data also explain why consecutive cortical UP states have uniform amplitudes in a given neuron. PMID:22934081

Toll-like receptor 4 enhancement of non-NMDA synaptic currents increases dentate excitability after brain injury.

PubMed

Li, Ying; Korgaonkar, Akshata A; Swietek, Bogumila; Wang, Jianfeng; Elgammal, Fatima S; Elkabes, Stella; Santhakumar, Vijayalakshmi

2015-02-01

Concussive brain injury results in neuronal degeneration, microglial activation and enhanced excitability in the hippocampal dentate gyrus, increasing the risk for epilepsy and memory dysfunction. Endogenous molecules released during injury can activate innate immune responses including toll-like receptor 4 (TLR4). Recent studies indicate that immune mediators can modulate neuronal excitability. Since non-specific agents that reduce TLR4 signaling can limit post-traumatic neuropathology, we examined whether TLR4 signaling contributes to early changes in dentate excitability after brain injury. Concussive brain injury caused a transient increase in hippocampal TLR4 expression within 4h, which peaked at 24h. Post-injury increase in TLR4 expression in the dentate gyrus was primarily neuronal and persisted for one week. Acute, in vitro treatment with TLR4 ligands caused bidirectional modulation of dentate excitability in control and brain-injured rats, with a reversal in the direction of modulation after brain injury. TLR4 antagonists decreased, and agonist increased, afferent-evoked dentate excitability one week after brain injury. NMDA receptor antagonist did not occlude the ability of LPS-RS, a TLR4 antagonist, to decrease post-traumatic dentate excitability. LPS-RS failed to modulate granule cell NMDA EPSCs but decreased perforant path-evoked non-NMDA EPSC peak amplitude and charge transfer in both granule cells and mossy cells. Our findings indicate an active role for TLR4 signaling in early post-traumatic dentate hyperexcitability. The novel TLR4 modulation of non-NMDA glutamatergic currents, identified herein, could represent a general mechanism by which immune activation influences neuronal excitability in neurological disorders that recruit sterile inflammatory responses. Copyright © 2014 Elsevier Inc. All rights reserved.

The PICK1 Ca2+ sensor modulates N-methyl-d-aspartate (NMDA) receptor-dependent microRNA-mediated translational repression in neurons.

PubMed

Rajgor, Dipen; Fiuza, Maria; Parkinson, Gabrielle T; Hanley, Jonathan G

2017-06-09

MicroRNAs (miRNAs) are important regulators of localized mRNA translation in neuronal dendrites. The presence of RNA-induced silencing complex proteins in these compartments and the dynamic miRNA expression changes that occur in response to neuronal stimulation highlight their importance in synaptic plasticity. Previously, we demonstrated a novel interaction between the major RNA-induced silencing complex component Argounaute-2 (Ago2) and the BAR (bin/amphiphysin/rvs) domain protein PICK1. PICK1 recruits Ago2 to recycling endosomes in dendrites, where it inhibits miRNA-mediated translational repression. Chemical induction of long-term depression via NMDA receptor activation causes the dissociation of Ago2 from PICK1 and a consequent increase in dendritic miRNA-mediated gene silencing. The mechanism that underlies the regulation of PICK1-Ago2 binding is unknown. In this study, we demonstrate that the PICK1-Ago2 interaction is directly sensitive to Ca 2+ ions so that high [Ca 2+ ] free reduces PICK1 binding to Ago2. Mutating a stretch of C-terminal Ca 2+ -binding residues in PICK1 results in a complete block of NMDA-induced PICK1-Ago2 disassociation in cortical neurons. Furthermore, the same mutant also blocks NMDA-stimulated miRNA-mediated gene silencing. This study defines a novel mechanism whereby elevated [Ca 2+ ] induced by NMDA receptor activation modulates Ago2 and miRNA activity via PICK1. Our work suggests a Ca 2+ -dependent process to regulate miRNA activity in neurons in response to the induction of long-term depression. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

GABAA overactivation potentiates the effects of NMDA blockade during the brain growth spurt in eliciting locomotor hyperactivity in juvenile mice.

PubMed

Oliveira-Pinto, Juliana; Paes-Branco, Danielle; Cristina-Rodrigues, Fabiana; Krahe, Thomas E; Manhães, Alex C; Abreu-Villaça, Yael; Filgueiras, Cláudio C

2015-01-01

Both NMDA receptor blockade and GABAA receptor overactivation during the brain growth spurt may contribute to the hyperactivity phenotype reminiscent of attention-deficit/hyperactivity disorder. Here, we evaluated the effects of exposure to MK801 (a NMDA antagonist) and/or to muscimol (a GABAA agonist) during the brain growth spurt on locomotor activity of juvenile Swiss mice. This study was carried out in two separate experiments. In the first experiment, pups received a single i.p. injection of either saline solution (SAL), MK801 (MK, 0.1, 0.3 or 0.5 mg/kg) or muscimol (MU, 0.02, 0.1 or 0.5 mg/kg) at the second postnatal day (PND2), and PNDs 4, 6 and 8. In the second experiment, we investigated the effects of a combined injection of MK (0.1 mg/kg) and MU (doses: 0.02, 0.1 or 0.5 mg/kg) following the same injection schedule of the first experiment. In both experiments, locomotor activity was assessed for 15 min at PND25. While MK promoted a dose-dependent increase in locomotor activity, exposure to MU failed to elicit significant effects. The combined exposure to the highest dose of MU and the lowest dose of MK induced marked hyperactivity. Moreover, the combination of the low dose of MK and the high dose of MU resulted in a reduced activity in the center of the open field, suggesting an increased anxiety-like behavior. These findings suggest that, during the brain growth spurt, the blockade of NMDA receptors induces juvenile locomotor hyperactivity whereas hyperactivation of GABAA receptors does not. However, GABAA overactivation during this period potentiates the effects of NMDA blockade in inducing locomotor hyperactivity. Copyright © 2015 Elsevier Inc. All rights reserved.

On the dynamical mechanisms of influence of synaptic currents on the neuron model with response differentiation

NASA Astrophysics Data System (ADS)

Zakharov, D. G.; Kuznetsov, A. S.

2015-08-01

The combined effect of synaptic NMDA, AMPA, and GABA currents on the neuron model with response differentiation has been considered. It has been shown that the GABA and NMDA currents can compensate the effects of each other, whereas the AMPA current not only leads to the suppression of oscillations but also significantly amplifies the high-frequency activity of the neuron induced by the NMDA current. Two bifurcation scenarios underlying these effects have been revealed. It has been predicted which scenario takes place under the combined influence of all three currents.

The investigation of neonatal MK-801 administration and physical environmental enrichment on emotional and cognitive functions in adult Balb/c mice.

PubMed

Akillioglu, Kubra; Babar Melik, Emine; Melik, Enver; Kocahan, Sayad

2012-09-01

N-methyl-D-aspartate (NMDA) receptors play an important role in brain maturation and developmental processes. It is known that growing up in an enriched environment has effects on emotional and cognitive performance. In our study, we evaluated the effects of physically enriched environment on the emotional and cognitive functions of the adult brain in the setting of previous NMDA receptor hypoactivity during the critical developmental period of the nervous system. In this study, NMDA receptor blockade was induced 5-10 days postnatally (PD5-10) using MK-801 in mice Balb/c (twice a day 0.25 mg/kg, for 5 days, intraperitoneal). MK-801 was given to developing mice living in a standard (SE) and an enrichment environment (EE) and once the animals reached adulthood, emotional behaviors were evaluated using an open field test (OF) and an elevated plus maze (EPM) test whereas cognitive processes were evaluated using the Morris water-maze (MWM). The EE group showed decreased locomotor activity (p<0.05) in the OF and increased exploratory behaviour (p<0.01) and decreased fear of heights/anxiety-like behaviour (p<0.05) in the EPM test. The EE had positive effects on spatial learning in the MWM (p<0.05). Blockade of the NMDA receptor increased the fear of height (p<0.05), decreased exploratory behaviour and locomotor activity (p<0.001). Also, it led to decreased spatial learning (p<0.05). The decreases in spatial learning and exploratory behaviours and the increase in fear of heights/anxiety-like behaviour with NMDA receptor blockade was not reversed by EE. NMDA receptor blockade during the critical period of development led to deterioration in the emotional and cognitive processes during adulthood. An enriched environmental did not reverse the deleterious effects of the NMDA receptor blockade on emotional and cognitive functions. Copyright © 2012. Published by Elsevier Inc.

Dephosphorylation of GluN2B C-Terminal Tyrosine Residues Does Not Contribute to Acute Ethanol Inhibition of Recombinant NMDA Receptors

PubMed Central

Hughes, Benjamin A.; Smothers, Corigan T.; Woodward, John J.

2013-01-01

N-methyl-D-aspartate (NMDA) receptors are ion channels activated by the neurotransmitter glutamate and are highly expressed by neurons. These receptors are critical for excitatory synaptic signaling and inhibition of NMDA receptors leads to impaired cognition and learning. Ethanol inhibits NMDA currents at concentrations associated with intoxication and this action may underlie some of the behavioral effects of ethanol. Although numerous sites and mechanisms of action have been tested, the manner in which ethanol inhibits NMDA receptors remains unclear. Recent findings in the literature suggest that ethanol, via facilitation of tyrosine phosphatase activity, may dephosphorylate key tyrosine residues in the C-terminus of GluN2B subunits resulting in diminished channel function. To directly test this hypothesis, we engineered GluN2B mutants that contained phenylalanine in place of tyrosine at three different sites and transiently expressed them with the GluN1 subunit in human embryonic kidney (HEK) cells. Whole-cell patch clamp electrophysiology was used to record glutamate-activated currents in the absence and presence of ethanol (10–600 mM). All mutants were functional and did not differ from one another with respect to current amplitude, steady-state to peak ratio, or magnesium block. Analysis of ethanol dose-response curves showed no significant difference in IC50 values between wild-type receptors and Y1252F, Y1336F, Y1472F or triple Y-F mutants. These findings suggest that dephosphorylation of C-terminal tyrosine residues does not account for ethanol inhibition of GluN2B receptors. PMID:23357553

NMDA receptor adjusted co-administration of ecstasy and cannabinoid receptor-1 agonist in the amygdala via stimulation of BDNF/Trk-B/CREB pathway in adult male rats.

PubMed

Ashabi, Ghorbangol; Sadat-Shirazi, Mitra-Sadat; Khalifeh, Solmaz; Elhampour, Laleh; Zarrindast, Mohammad-Reza

2017-04-01

Consumption of cannabinoid receptor-1 (CB-1) agonist such as cannabis is widely taken in 3,4- methylenedioxymethamphetamine (MDMA) or ecstasy users; it has been hypothesized that co-consumption of CB-1 agonist might protect neurons against MDMA toxicity. N-methyl-d-aspartate (NMDA) receptors regulate neuronal plasticity and firing rate in the brain through Tyrosine-kinase B (Trk-B) activation. The molecular and electrophysiological association among NMDA and MDMA/Arachidonylcyclopropylamide (ACPA, a selective CB-1 receptor agonist) co-consumption was not well-known. Here, neuronal spontaneous activity, Brain-derived neurotrophic factor (BDNF), Trk-B and cAMP response element binding protein (CREB) phosphorylation levels were recognized in ACPA and MDMA co-injected rats. Besides, we proved the role of NMDA receptor on MDMA and ACPA combination on neuronal spontaneous activity and Trk-B/BDNF pathway in the central amygdala (CeA). Male rats were anesthetized with intra-peritoneal injections of urethane; MDMA, D-2-amino-5-phosphonopentanoate (D-AP5, NMDA receptor antagonist) were injected into CeA. ACPA was administrated by intra-cerebroventricular injection. Thirty minutes following injections, neuronal firing rate was recorded from CeA. Two hours after drug injection, amygdala was collected from brain for molecular evaluations. Single administration of MDMA and/or ACPA reduced firing rates compared with sham group in the CeA dose-dependently. Injection of D-AP5, ACPA and MDMA reduced firing rate compared with sham group (P<0.001). Interestingly, injection of ACPA+MDMA enhanced BDNF, Trk-B and CREB phosphorylation compared with MDMA groups. D-AP5, ACPA and MDMA co-injection decreased BDNF, Trk-B and CREB phosphorylation levels compared with ACPA+MDMA in the amygdala (P<0.01). Probably, NMDA receptors are involved in the protective role of acute MDMA+ACPA co-injection via BDNF/Trk-B/CREB pathways. Copyright © 2017 Elsevier Inc. All rights reserved.

Clozapine and glycinamide prevent MK-801-induced deficits in the novel object recognition (NOR) test in the domestic rabbit (Oryctolagus cuniculus).

PubMed

Hoffman, Kurt L; Basurto, Enrique

2014-09-01

Studies in humans indicate that acute administration of sub-anesthetic doses of ketamine, an NMDA receptor antagonist, provokes schizophrenic-like symptoms in healthy volunteers, and exacerbates existing symptoms in individuals with schizophrenia. These and other findings suggest that NMDA receptor hypofunction might participate in the pathophysiology of schizophrenia, and have prompted the development of rodent pharmacological models for this disorder based on acute or subchronic treatment with NMDA receptor antagonists, as well as the development of novel pharmacotherapies based on increasing extrasynaptic glycine concentrations. In the present study, we tested whether acute hyperlocomotory behavior and/or deficits in the novel object recognition (NOR) task, induced in male rabbits by the acute subcutaneous (s.c.) administration of MK-801 (0.025 and 0.037 mg/kg s.c., respectively), were prevented by prior administration of the atypcial antipsychotic, clozapine (0.2mg/kg, s.c.), or the glycine pro-drug glycinamide (56 mg/kg, s.c.). We found that clozapine fully prevented the MK-801-induced hyperlocomotion, and both clozapine and glycinamide prevented MK-801-induced deficits in the NOR task. The present results show that MK-801-induced hyperlocomotion and deficits in the NOR task in the domestic rabbit demonstrate predictive validity as an alternative animal model for symptoms of schizophrenia. Moreover, these results indicate that glycinamide should be investigated in pre-clinical models of neuropsychiatric disorders such as schizophrenia, obsessive compulsive disorder and anxiety disorders, where augmentation of extrasynaptic glycine concentrations may have therapeutic utility. Copyright © 2014 Elsevier B.V. All rights reserved.

Gentiopicroside attenuates morphine rewarding effect through downregulation of GluN2B receptors in nucleus accumbens.

PubMed

Liu, Shui-Bing; Ma, Lan; Guo, Hong-Ju; Feng, Bin; Guo, Yan-Yan; Li, Xiao-Qiang; Sun, Wen-Ji; Zheng, Lian-He; Zhao, Ming-Gao

2012-08-01

Gentiopicroside (Gent) is one of the secoiridoid compound isolated from Gentiana lutea. This compound exhibits analgesic activities and inhibits the expression of GluN2B-containing N-methyl-D-aspartate (NMDA) receptors in the anterior cingulate cortex in mice. Nucleus accumbens (NAc) is a forebrain structure known for its role in drug addiction. However, little is known about the role of Gent on morphine dependence and synaptic transmission changes in the NAc. Conditioned place preference (CPP) test and behavioral sensitization of locomotor activity were used to investigate drug-seeking related behaviors. Brain slices containing NAc were prepared, and whole-cell patch-clamp recordings were performed to record the excitatory postsynaptic currents (EPSCs). Expression of proteins was detected by Western blot analysis. Systemic administration of Gent attenuated the CPP effect induced by morphine, but had no effect on morphine-induced behavioral sensitization. Gent significantly reversed overexpression of GluN2B-containing NMDA receptors and dopamine D2 receptors in NAc during the first week of morphine withdrawal. However, the compound did not affect the overexpression of GluN2A-containing NMDA receptors, GluA1, and dopamine D1 receptors. Lastly, Gent significantly reduced NMDA receptors-mediated EPSCs in the NAc. Our study provides strong evidence that Gent inhibits morphine dependence through downregulation of GluN2B-containing NMDA receptors in the NAc. © 2012 Blackwell Publishing Ltd.

Involvement of ERK in NMDA receptor-independent cortical neurotoxicity of hydrogen sulfide

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

Kurokawa, Yuko; Sekiguchi, Fumiko; Kubo, Satoko

2011-11-04

Highlights: Black-Right-Pointing-Pointer Hydrogen sulfide causes NMDA receptor-independent neurotoxicity in mouse fetal cortical neurons. Black-Right-Pointing-Pointer Activation of ERK mediates the toxicity of hydrogen sulfide. Black-Right-Pointing-Pointer Apoptotic mechanisms are involved in the hydrogen-induced cell death. -- Abstract: Hydrogen sulfide (H{sub 2}S), a gasotransmitter, exerts both neurotoxicity and neuroprotection, and targets multiple molecules including NMDA receptors, T-type calcium channels and NO synthase (NOS) that might affect neuronal viability. Here, we determined and characterized effects of NaHS, an H{sub 2}S donor, on cell viability in the primary cultures of mouse fetal cortical neurons. NaHS caused neuronal death, as assessed by LDH release and trypanmore » blue staining, but did not significantly reduce the glutamate toxicity. The neurotoxicity of NaHS was resistant to inhibitors of NMDA receptors, T-type calcium channels and NOS, and was blocked by inhibitors of MEK, but not JNK, p38 MAP kinase, PKC and Src. NaHS caused prompt phosphorylation of ERK and upregulation of Bad, followed by translocation of Bax to mitochondria and release of mitochondrial cytochrome c, leading to the nuclear condensation/fragmentation. These effects of NaHS were suppressed by the MEK inhibitor. Our data suggest that the NMDA receptor-independent neurotoxicity of H{sub 2}S involves activation of the MEK/ERK pathway and some apoptotic mechanisms.« less

Short-term field stimulation mimics synaptic maturation of hippocampal synapses

PubMed Central

Bagley, Elena E; Westbrook, Gary L

2012-01-01

Many aspects of synaptic transmission are modified during development, reflecting not only the consequence of developmental programmes of gene expression, but also the effects of ongoing neural activity. We investigated the role of synaptic activity in the maturation of Schaffer collateral (SC)–CA1 synapses using sustained low frequency field stimulation of acute brain slices. Between postnatal days 4–6 and 14–16, mouse SC–CA1 synapses in naïve slices showed a developmental decrease in the probability of transmitter release (Pr) and an increase in the contribution of GluN2A (NR2A) subunits to the NMDA receptor-mediated excitatory postsynaptic current (EPSC). Surprisingly, these developmental changes could be mimicked by short term (4 h) in vitro synaptic activity in slices taken from postnatal days (PND) 4–6 mice. However, different activity levels were required to alter release probability compared to the NMDA receptor subunit composition. Spontaneous synaptic activity was sufficient to alter the NMDA receptor subunit composition, but sustained low-frequency field stimulation of the brain slice (0.1 Hz, 4 h) was necessary to reduce release probability, as assessed 1 h following the cessation of stimulation. The protein synthesis inhibitor anisomycin blocked the effect of field stimulation on release probability. These results indicate that features of mature excitatory synapses can be rapidly induced in immature neurons. The activity dependence of the Pr and NMDA receptor subunit composition serves as a sensitive indicator of prior neural activity, and provides dual mechanisms for homeostatic control of excitatory synaptic efficacy. PMID:22351628

Short-term field stimulation mimics synaptic maturation of hippocampal synapses.

PubMed

Bagley, Elena E; Westbrook, Gary L

2012-04-01

Many aspects of synaptic transmission are modified during development, reflecting not only the consequence of developmental programmes of gene expression, but also the effects of ongoing neural activity. We investigated the role of synaptic activity in the maturation of Schaffer collateral (SC)-CA1 synapses using sustained low frequency field stimulation of acute brain slices. Between postnatal days 4-6 and 14-16, mouse SC-CA1 synapses in naïve slices showed a developmental decrease in the probability of transmitter release (P(r)) and an increase in the contribution of GluN2A (NR2A) subunits to the NMDA receptor-mediated excitatory postsynaptic current (EPSC). Surprisingly, these developmental changes could be mimicked by short term (4 h) in vitro synaptic activity in slices taken from postnatal days (PND) 4-6 mice. However, different activity levels were required to alter release probability compared to the NMDA receptor subunit composition. Spontaneous synaptic activity was sufficient to alter the NMDA receptor subunit composition, but sustained low-frequency field stimulation of the brain slice (0.1 Hz, 4 h) was necessary to reduce release probability, as assessed 1 h following the cessation of stimulation. The protein synthesis inhibitor anisomycin blocked the effect of field stimulation on release probability. These results indicate that features of mature excitatory synapses can be rapidly induced in immature neurons. The activity dependence of the P(r) and NMDA receptor subunit composition serves as a sensitive indicator of prior neural activity, and provides dual mechanisms for homeostatic control of excitatory synaptic efficacy.

Chronic administration of aripiprazole activates GSK3β-dependent signalling pathways, and up-regulates GABAA receptor expression and CREB1 activity in rats.

PubMed

Pan, Bo; Huang, Xu-Feng; Deng, Chao

2016-07-20

Aripiprazole is a D2-like receptor (D2R) partial agonist with a favourable clinical profile. Previous investigations indicated that acute and short-term administration of aripiprazole had effects on PKA activity, GSK3β-dependent pathways, GABAA receptors, NMDA receptor and CREB1 in the brain. Since antipsychotics are used chronically in clinics, the present study investigated the long-term effects of chronic oral aripiprazole treatment on these cellular signalling pathways, in comparison with haloperidol (a D2R antagonist) and bifeprunox (a potent D2R partial agonist). We found that the Akt-GSK3β pathway was activated by aripiprazole and bifeprunox in the prefrontal cortex; NMDA NR2A levels were reduced by aripiprazole and haloperidol. In the nucleus accumbens, all three drugs increased Akt-GSK3β signalling; in addition, both aripiprazole and haloperidol, but not bifeprunox, increased the expression of Dvl-3, β-catenin and GABAA receptors, NMDA receptor subunits, as well as CREB1 phosphorylation levels. The results suggest that chronic oral administration of aripiprazole affects schizophrenia-related cellular signalling pathways and markers (including Akt-GSK3β signalling, Dvl-GSK3β-β-catenin signalling, GABAA receptor, NMDA receptor and CREB1) in a brain-region-dependent manner; the selective effects of aripiprazole on these signalling pathways might be associated with its unique clinical effects.

Trace and contextual fear conditioning require neural activity and NMDA receptor-dependent transmission in the medial prefrontal cortex

PubMed Central

Gilmartin, Marieke R.; Helmstetter, Fred J.

2010-01-01

The contribution of the medial prefrontal cortex (mPFC) to the formation of memory is a subject of considerable recent interest. Notably, the mechanisms supporting memory acquisition in this structure are poorly understood. The mPFC has been implicated in the acquisition of trace fear conditioning, a task that requires the association of a conditional stimulus (CS) and an aversive unconditional stimulus (UCS) across a temporal gap. In both rat and human subjects, frontal regions show increased activity during the trace interval separating the CS and UCS. We investigated the contribution of prefrontal neural activity in the rat to the acquisition of trace fear conditioning using microinfusions of the γ-aminobutyric acid type A (GABAA) receptor agonist muscimol. We also investigated the role of prefrontal N-methyl-d-aspartate (NMDA) receptor-mediated signaling in trace fear conditioning using the NMDA receptor antagonist 2-amino-5-phosphonovaleric acid (APV). Temporary inactivation of prefrontal activity with muscimol or blockade of NMDA receptor-dependent transmission in mPFC impaired the acquisition of trace, but not delay, conditional fear responses. Simultaneously acquired contextual fear responses were also impaired in drug-treated rats exposed to trace or delay, but not unpaired, training protocols. Our results support the idea that synaptic plasticity within the mPFC is critical for the long-term storage of memory in trace fear conditioning. PMID:20504949

Role of the NMDA receptor and iron on free radical production and brain damage following transient middle cerebral artery occlusion.

PubMed

Im, Doo Soon; Jeon, Jeong Wook; Lee, Jin Soo; Won, Seok Joon; Cho, Sung Ig; Lee, Yong Beom; Gwag, Byoung Joo

2012-05-21

Excess activation of ionotropic glutamate receptors and iron is believed to contribute to free radical production and neuronal death following hypoxic ischemia. We examined the possibility that both NMDA receptor activation and iron overload determine spatial and temporal patterns of free radical production after transient middle cerebral artery occlusion (tMCAO) in male Sprague-Dawley rats. Mitochondrial free radical (MFR) levels were maximally increased in neurons in the core at 1 h and 24 h after tMCAO. Early MFR production was blocked by administration of MK-801, an NMDA receptor antagonist, but not deferoxamine, an iron chelator. Neither MK-801 nor deferoxamine attenuated late MFR production in the core. Increased MFRs were observed in penumbral neurons within 6 h and gradually increased over 24 h after tMCAO. Slowly-evolving MFRs in the core and penumbra were accompanied by iron overload. Deferoxamine blocked iron overload but reduced MFR production only in the penumbra. Combined MK-801/deferoxamine reduced late MFR production in both core and penumbra in an additive manner. Combination therapy significantly ameliorated infarction compared with monotherapy. These findings suggest that the NMDA receptor activation and iron overload mediate late MFR production and infarction after tMCAO. Copyright © 2012 Elsevier B.V. All rights reserved.

Isoflurane-Induced Caspase-3 Activation Is Dependent on Cytosolic Calcium and Can Be Attenuated by Memantine

PubMed Central

Zhang, Guohua; Dong, Yuanlin; Zhang, Bin; Ichinose, Fumito; Wu, Xu; Culley, Deborah J.; Crosby, Gregory

2008-01-01

Increasing evidence indicates that caspase activation and apoptosis are associated with a variety of neurodegenerative disorders, including Alzheimer's disease. We reported that anesthetic isoflurane can induce apoptosis, alter processing of the amyloid precursor protein (APP), and increase amyloid-β protein (Aβ) generation. However, the mechanism by which isoflurane induces apoptosis is primarily unknown. We therefore set out to assess effects of extracellular calcium concentration on isoflurane-induced caspase-3 activation in H4 human neuroglioma cells stably transfected to express human full-length APP (H4-APP cells). In addition, we tested effects of RNA interference (RNAi) silencing of IP3 receptor, NMDA receptor, and endoplasmic reticulum (ER) calcium pump, sacro-/ER calcium ATPase (SERCA1). Finally, we examined the effects of the NMDA receptor partial antagonist, memantine, in H4-APP cells and brain tissue of naive mice. EDTA (10 mm), BAPTA (10 μm), and RNAi silencing of IP3 receptor, NMDA receptor, or SERCA1 attenuated capase-3 activation. Memantine (4 μm) inhibited isoflurane-induced elevations in cytosolic calcium levels and attenuated isoflurane-induced caspase-3 activation, apoptosis, and cell viability. Memantine (20 mg/kg, i.p.) reduced isoflurane-induced caspase-3 activation in brain tissue of naive mice. These results suggest that disruption of calcium homeostasis underlies isoflurane-induced caspase activation and apoptosis. We also show for the first time that the NMDA receptor partial antagonist, memantine, can prevent isoflurane-induced caspase-3 activation and apoptosis in vivo and in vitro. These findings, indicating that isoflurane-induced caspase activation and apoptosis are dependent on cytosolic calcium levels, should facilitate the provision of safer anesthesia care, especially for Alzheimer's disease and elderly patients. PMID:18434534

Prenatal exposure to phencyclidine produces abnormal behaviour and NMDA receptor expression in postpubertal mice.

PubMed

Lu, Lingling; Mamiya, Takayoshi; Lu, Ping; Toriumi, Kazuya; Mouri, Akihiro; Hiramatsu, Masayuki; Kim, Hyoung-Chun; Zou, Li-Bo; Nagai, Taku; Nabeshima, Toshitaka

2010-08-01

Several studies have shown the disruptive effects of non-competitive N-methyl-d-aspartate (NMDA) receptor antagonists on neurobehavioural development. Based on the neurodevelopment hypothesis of schizophrenia, there is growing interest in animal models treated with NMDA antagonists at developing stages to investigate the pathogenesis of psychological disturbances in humans. Previous studies have reported that perinatal treatment with phencyclidine (PCP) impairs the development of neuronal systems and induces schizophrenia-like behaviour. However, the adverse effects of prenatal exposure to PCP on behaviour and the function of NMDA receptors are not well understood. This study investigated the long-term effects of prenatal exposure to PCP in mice. The prenatal PCP-treated mice showed hypersensitivity to a low dose of PCP in locomotor activity and impairment of recognition memory in the novel object recognition test at age 7 wk. Meanwhile, the prenatal exposure reduced the phosphorylation of NR1, although it increased the expression of NR1 itself. Furthermore, these behavioural changes were attenuated by atypical antipsychotic treatment. Taken together, prenatal exposure to PCP produced long-lasting behavioural deficits, accompanied by the abnormal expression and dysfunction of NMDA receptors in postpubertal mice. It is worth investigating the influences of disrupted NMDA receptors during the prenatal period on behaviour in later life.

Is the Acute NMDA Receptor Hypofunction a Valid Model of Schizophrenia?

PubMed Central

Adell, Albert; Jiménez-Sánchez, Laura; López-Gil, Xavier; Romón, Tamara

2012-01-01

Several genetic, neurodevelopmental, and pharmacological animal models of schizophrenia have been established. This short review examines the validity of one of the most used pharmacological model of the illness, ie, the acute administration of N-methyl-D-aspartate (NMDA) receptor antagonists in rodents. In some cases, data on chronic or prenatal NMDA receptor antagonist exposure have been introduced for comparison. The face validity of acute NMDA receptor blockade is granted inasmuch as hyperlocomotion and stereotypies induced by phencyclidine, ketamine, and MK-801 are regarded as a surrogate for the positive symptoms of schizophrenia. In addition, the loss of parvalbumin-containing cells (which is one of the most compelling finding in postmortem schizophrenia brain) following NMDA receptor blockade adds construct validity to this model. However, the lack of changes in glutamic acid decarboxylase (GAD67) is at variance with human studies. It is possible that changes in GAD67 are more reflective of the neurodevelopmental condition of schizophrenia. Finally, the model also has predictive validity, in that its behavioral and transmitter activation in rodents are responsive to antipsychotic treatment. Overall, although not devoid of drawbacks, the acute administration of NMDA receptor antagonists can be considered as a good model of schizophrenia bearing a satisfactory degree of validity. PMID:21965469

Decrement in operant performance produced by NMDA receptor antagonists in the rat: tolerance and cross-tolerance.

PubMed

Dravolina, O A; Zvartau, E E; Bespalov, A Y

2000-04-01

Current perspectives on the clinical use of NMDA receptor antagonists infer repeated administration schedules for the management of different pathological states. The development of tolerance and cross-tolerance between different NMDA receptor antagonists may be an important factor contributing to the clinical efficacy of these drugs. The present study aimed to characterize the development of tolerance and cross-tolerance to the ability of various site-selective NMDA receptor antagonists to produce a decrement of operant responding (multiple extinction 9 s fixed-interval 1-s schedule of water reinforcement). Acute administration of D-CPPen (SDZ EAA 494; 1-5.6 mg/kg), dizocilpine (MK-801; 0.03-0.3 mg/kg), memantine (0.3-17 mg/kg), ACEA-1021 (10-56 mg/kg), and eliprodil (1-30 mg/kg) differentially affected operant responding. Both increases and decreases in response rates and accuracy of responding were observed. Repeated preexposure to D-CPPen (5.6 mg/kg, once a day for 7 days) attenuated a behavioral disruption produced by an acute challenge with D-CPPen or ACEA-1021, but potentiated the effects of dizocilpine, memantine, and eliprodil. Based on the present results, one can suggest that the repeated administration of a competitive NMDA receptor antagonist differentially affects the functional activity of various sites on NMDA receptor complex.

Glutamate receptor antibodies in neurological diseases: anti-AMPA-GluR3 antibodies, anti-NMDA-NR1 antibodies, anti-NMDA-NR2A/B antibodies, anti-mGluR1 antibodies or anti-mGluR5 antibodies are present in subpopulations of patients with either: epilepsy, encephalitis, cerebellar ataxia, systemic lupus erythematosus (SLE) and neuropsychiatric SLE, Sjogren's syndrome, schizophrenia, mania or stroke. These autoimmune anti-glutamate receptor antibodies can bind neurons in few brain regions, activate glutamate receptors, decrease glutamate receptor's expression, impair glutamate-induced signaling and function, activate blood brain barrier endothelial cells, kill neurons, damage the brain, induce behavioral/psychiatric/cognitive abnormalities and ataxia in animal models, and can be removed or silenced in some patients by immunotherapy.

PubMed

Levite, Mia

2014-08-01

Glutamate is the major excitatory neurotransmitter of the Central Nervous System (CNS), and it is crucially needed for numerous key neuronal functions. Yet, excess glutamate causes massive neuronal death and brain damage by excitotoxicity--detrimental over activation of glutamate receptors. Glutamate-mediated excitotoxicity is the main pathological process taking place in many types of acute and chronic CNS diseases and injuries. In recent years, it became clear that not only excess glutamate can cause massive brain damage, but that several types of anti-glutamate receptor antibodies, that are present in the serum and CSF of subpopulations of patients with a kaleidoscope of human neurological diseases, can undoubtedly do so too, by inducing several very potent pathological effects in the CNS. Collectively, the family of anti-glutamate receptor autoimmune antibodies seem to be the most widespread, potent, dangerous and interesting anti-brain autoimmune antibodies discovered up to now. This impression stems from taking together the presence of various types of anti-glutamate receptor antibodies in a kaleidoscope of human neurological and autoimmune diseases, their high levels in the CNS due to intrathecal production, their multiple pathological effects in the brain, and the unique and diverse mechanisms of action by which they can affect glutamate receptors, signaling and effects, and subsequently impair neuronal signaling and induce brain damage. The two main families of autoimmune anti-glutamate receptor antibodies that were already found in patients with neurological and/or autoimmune diseases, and that were already shown to be detrimental to the CNS, include the antibodies directed against ionotorpic glutamate receptors: the anti-AMPA-GluR3 antibodies, anti-NMDA-NR1 antibodies and anti-NMDA-NR2 antibodies, and the antibodies directed against Metabotropic glutamate receptors: the anti-mGluR1 antibodies and the anti-mGluR5 antibodies. Each type of these anti-glutamate receptor antibodies is discussed separately in this very comprehensive review, with regards to: the human diseases in which these anti-glutamate receptor antibodies were found thus far, their presence and production in the nervous system, their association with various psychiatric/behavioral/cognitive/motor impairments, their possible association with certain infectious organisms, their detrimental effects in vitro as well as in vivo in animal models in mice, rats or rabbits, and their diverse and unique mechanisms of action. The review also covers the very encouraging positive responses to immunotherapy of some patients that have either of the above-mentioned anti-glutamate receptor antibodies, and that suffer from various neurological diseases/problems. All the above are also summarized in the review's five schematic and useful figures, for each type of anti-glutamate receptor antibodies separately. The review ends with a summary of all the main findings, and with recommended guidelines for diagnosis, therapy, drug design and future investigations. In the nut shell, the human studies, the in vitro studies, as well as the in vivo studies in animal models in mice, rats and rabbit revealed the following findings regarding the five different types of anti-glutamate receptor antibodies: (1) Anti-AMPA-GluR3B antibodies are present in ~25-30% of patients with different types of Epilepsy. When these anti-glutamate receptor antibodies (or other types of autoimmune antibodies) are found in Epilepsy patients, and when these autoimmune antibodies are suspected to induce or aggravate the seizures and/or the cognitive/psychiatric/behavioral impairments that sometimes accompany the seizures, the Epilepsy is called 'Autoimmune Epilepsy'. In some patients with 'Autoimmune Epilepsy' the anti-AMPA-GluR3B antibodies associate significantly with psychiatric/cognitive/behavior abnormalities. In vitro and/or in animal models, the anti-AMPA-GluR3B antibodies by themselves induce many pathological effects: they activate glutamate/AMPA receptors, kill neurons by 'Excitotoxicity', and/or by complement activation modulated by complement regulatory proteins, cause multiple brain damage, aggravate chemoconvulsant-induced seizures, and also induce behavioral/motor impairments. Some patients with 'Autoimmune Epilepsy' that have anti-AMPA-GluR3B antibodies respond well (although sometimes transiently) to immunotherapy, and thanks to that have reduced seizures and overall improved neurological functions. (2) Anti-NMDA-NR1 antibodies are present in patients with autoimmune 'Anti-NMDA-receptor Encephalitis'. In humans, in animal models and in vitro the anti-NMDA-NR1 antibodies can be very pathogenic since they can cause a pronounced decrease of surface NMDA receptors expressed in hippocampal neurons, and also decrease the cluster density and synaptic localization of the NMDA receptors. The anti-NMDA-NR1 antibodies induce these effects by crosslinking and internalization of the NMDA receptors. Such changes can impair glutamate signaling via the NMDA receptors and lead to various neuronal/behavior/cognitive/psychiatric abnormalities. Anti-NMDA-NR1 antibodies are frequently present in high levels in the CSF of the patients with 'Anti-NMDA-receptor encephalitis' due to their intrathecal production. Many patients with 'Anti-NMDA receptor Encephalitis' respond well to several modes of immunotherapy. (3) Anti-NMDA-NR2A/B antibodies are present in a substantial number of patients with Systemic Lupus Erythematosus (SLE) with or without neuropsychiatric problems. The exact percentage of SLE patients having anti-NMDA-NR2A/B antibodies varies in different studies from 14 to 35%, and in one study such antibodies were found in 81% of patients with diffuse 'Neuropshychiatric SLE', and in 44% of patients with focal 'Neuropshychiatric SLE'. Anti-NMDA-NR2A/B antibodies are also present in subpopulations of patients with Epilepsy of several types, Encephalitis of several types (e.g., chronic progressive limbic Encephalitis, Paraneoplastic Encephalitis or Herpes Simplex Virus Encephalitis), Schizophrenia, Mania, Stroke, or Sjorgen syndrome. In some patients, the anti-NMDA-NR2A/B antibodies are present in both the serum and the CSF. Some of the anti-NMDA-NR2A/B antibodies cross-react with dsDNA, while others do not. Some of the anti-NMDA-NR2A/B antibodies associate with neuropsychiatric/cognitive/behavior/mood impairments in SLE patients, while others do not. The anti-NMDA-NR2A/B antibodies can undoubtedly be very pathogenic, since they can kill neurons by activating NMDA receptors and inducing 'Excitotoxicity', damage the brain, cause dramatic decrease of membranal NMDA receptors expressed in hippocampal neurons, and also induce behavioral cognitive impairments in animal models. Yet, the concentration of the anti-NMDA-NR2A/B antibodies seems to determine if they have positive or negative effects on the activity of glutamate receptors and on the survival of neurons. Thus, at low concentration, the anti-NMDA-NR2A/B antibodies were found to be positive modulators of receptor function and increase the size of NMDA receptor-mediated excitatory postsynaptic potentials, whereas at high concentration they are pathogenic as they promote 'Excitotoxcity' through enhanced mitochondrial permeability transition. (4) Anti-mGluR1 antibodies were found thus far in very few patients with Paraneoplastic Cerebellar Ataxia, and in these patients they are produced intrathecally and therefore present in much higher levels in the CSF than in the serum. The anti-mGluR1 antibodies can be very pathogenic in the brain since they can reduce the basal neuronal activity, block the induction of long-term depression of Purkinje cells, and altogether cause cerebellar motor coordination deficits by a combination of rapid effects on both the acute and the plastic responses of Purkinje cells, and by chronic degenerative effects. Strikingly, within 30 min after injection of anti-mGluR1 antibodies into the brain of mice, the mice became ataxic. Anti-mGluR1 antibodies derived from patients with Ataxia also caused disturbance of eye movements in animal models. Immunotherapy can be very effective for some Cerebellar Ataxia patients that have anti-mGluR1 antibodies. (5) Anti-mGluR5 antibodies were found thus far in the serum and CSF of very few patients with Hodgkin lymphoma and Limbic Encephalopathy (Ophelia syndrome). The sera of these patients that contained anti-GluR5 antibodies reacted with the neuropil of the hippocampus and cell surface of live rat hippocampal neurons, and immunoprecipitation from cultured neurons and mass spectrometry demonstrated that the antigen was indeed mGluR5. Taken together, all these evidences show that anti-glutamate receptor antibodies are much more frequent among various neurological diseases than ever realized before, and that they are very detrimental to the nervous system. As such, they call for diagnosis, therapeutic removal or silencing and future studies. What we have learned by now about the broad family of anti-glutamate receptor antibodies is so exciting, novel, unique and important, that it makes all future efforts worthy and essential.

Essential Role of NMDA Receptor Channel ε4 Subunit (GluN2D) in the Effects of Phencyclidine, but Not Methamphetamine

PubMed Central

Hagino, Yoko; Kasai, Shinya; Han, Wenhua; Yamamoto, Hideko; Nabeshima, Toshitaka; Mishina, Masayoshi; Ikeda, Kazutaka

2010-01-01

Phencyclidine (PCP), a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, increases locomotor activity in rodents and causes schizophrenia-like symptoms in humans. Although activation of the dopamine (DA) pathway is hypothesized to mediate these effects of PCP, the precise mechanisms by which PCP induces its effects remain to be elucidated. The present study investigated the effect of PCP on extracellular levels of DA (DAex) in the striatum and prefrontal cortex (PFC) using in vivo microdialysis in mice lacking the NMDA receptor channel ε1 or ε4 subunit (GluRε1 [GluN2A] or GluRε4 [GluN2D]) and locomotor activity. PCP significantly increased DAex in wildtype and GluRε1 knockout mice, but not in GluRε4 knockout mice, in the striatum and PFC. Acute and repeated administration of PCP did not increase locomotor activity in GluRε4 knockout mice. The present results suggest that PCP enhances dopaminergic transmission and increases locomotor activity by acting at GluRε4. PMID:21060893

Iron Mediates N-Methyl-d-aspartate Receptor-dependent Stimulation of Calcium-induced Pathways and Hippocampal Synaptic Plasticity*

PubMed Central

Muñoz, Pablo; Humeres, Alexis; Elgueta, Claudio; Kirkwood, Alfredo; Hidalgo, Cecilia; Núñez, Marco T.

2011-01-01

Iron deficiency hinders hippocampus-dependent learning processes and impairs cognitive performance, but current knowledge on the molecular mechanisms underlying the unique role of iron in neuronal function is sparse. Here, we investigated the participation of iron on calcium signal generation and ERK1/2 stimulation induced by the glutamate agonist N-methyl-d-aspartate (NMDA), and the effects of iron addition/chelation on hippocampal basal synaptic transmission and long-term potentiation (LTP). Addition of NMDA to primary hippocampal cultures elicited persistent calcium signals that required functional NMDA receptors and were independent of calcium influx through L-type calcium channels or α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors; NMDA also promoted ERK1/2 phosphorylation and nuclear translocation. Iron chelation with desferrioxamine or inhibition of ryanodine receptor (RyR)-mediated calcium release with ryanodine-reduced calcium signal duration and prevented NMDA-induced ERK1/2 activation. Iron addition to hippocampal neurons readily increased the intracellular labile iron pool and stimulated reactive oxygen species production; the antioxidant N-acetylcysteine or the hydroxyl radical trapper MCI-186 prevented these responses. Iron addition to primary hippocampal cultures kept in calcium-free medium elicited calcium signals and stimulated ERK1/2 phosphorylation; RyR inhibition abolished these effects. Iron chelation decreased basal synaptic transmission in hippocampal slices, inhibited iron-induced synaptic stimulation, and impaired sustained LTP in hippocampal CA1 neurons induced by strong stimulation. In contrast, iron addition facilitated sustained LTP induction after suboptimal tetanic stimulation. Together, these results suggest that hippocampal neurons require iron to generate RyR-mediated calcium signals after NMDA receptor stimulation, which in turn promotes ERK1/2 activation, an essential step of sustained LTP. PMID:21296883

Involvement of NMDA receptor in low-frequency magnetic field-induced anxiety in mice.

PubMed

Salunke, Balwant P; Umathe, Sudhir N; Chavan, Jagatpalsingh G

2014-12-01

It had been reported that exposure to extremely low-frequency magnetic field (ELFMF) induces anxiety in human and rodents. Anxiety mediates via the activation of N-methyl-d-aspartate (NMDA) receptor, whereas activation of γ-aminobutyric acid (GABA) receptor attenuates the same. Hence, the present study was carried out to understand the contribution of NMDA and/or GABA receptors modulation in ELFMF-induced anxiety for which Swiss albino mice were exposed to ELFMF (50 Hz, 10 G) by subjecting them to Helmholtz coils. The exposure was for 8 h/day for 7, 30, 60, 90 and 120 days. Anxiety level was assessed in elevated plus maze, open field test and social interaction test, on 7th, 30th, 60th, 90th and 120th exposure day, respectively. Moreover, the role of GABA and glutamate in ELFMF-induced anxiety was assessed by treating mice with muscimol [0.25 mg/kg intraperitoneally (i.p.)], bicuculline (1.0 mg/kg i.p.), NMDA (15 mg/kg i.p.) and MK-801 (0.03 mg/kg i.p.), as a GABAA and NMDA receptor agonist and antagonist, respectively. Glutamate receptor agonist exacerbated while inhibitor attenuated the ELFMF-induced anxiety. In addition, levels of GABA and glutamate were determined in regions of the brain viz, cortex, striatum, hippocampus and hypothalamus. Experiments demonstrated significant elevation of GABA and glutamate levels in the hippocampus and hypothalamus. However, GABA receptor modulators did not produce significant effect on ELFMF-induced anxiety and elevated levels of GABA at tested dose. Together, these findings suggest that ELFMF significantly induced anxiety behavior, and indicated the involvement of NMDA receptor in its effect.

Drugs acting on amino acid neurotransmitters.

PubMed

Meldrum, B S

1986-01-01

The most potent agents currently available for suppressing myoclonic activity in animals and humans act to enhance GABA-mediated inhibition and/or to diminish amino acid-induced excitation. Postsynaptic GABA-mediated inhibition plays an important role at the cortical level, diminishing the effect of augmented afferent activity and preventing pathologically enhanced output. Enhancement of GABAergic inhibition, principally at the cortical level but also at lower levels, by clonazepam and by valproate appears to be a predominant element in their antimyoclonic action. Studies in various animal models, including photically induced myoclonus in the baboon, P papio, indicate the value of other approaches to enhancing GABA-mediated inhibition. Among such approaches meriting evaluation in humans are inhibition of GABA-transaminase activity by gamma-vinyl GABA and action at some of the benzodiazepine receptors to enhance the action of GABA, as by the novel anticonvulsant beta-carbolines. Excitatory transmission mediated by dicarboxylic amino acids appears to play a role in myoclonus, especially at the spinal level, but also in the brainstem, cerebellum, basal ganglia, and cortex. Among various novel agents that act at the postsynaptic receptor site to antagonize such excitation, those specifically blocking excitation induced by aspartate and/or NMDA prevent myoclonic activity in a wide range of animal models. Further research is required before such agents can be evaluated in humans.

NMDA receptors are involved in the antidepressant-like effects of capsaicin following amphetamine withdrawal in male mice.

PubMed

Amiri, Shayan; Alijanpour, Sakineh; Tirgar, Fatemeh; Haj-Mirzaian, Arya; Amini-Khoei, Hossein; Rahimi-Balaei, Maryam; Rastegar, Mojgan; Ghaderi, Marzieh; Ghazi-Khansari, Mahmoud; Zarrindast, Mohammad-Reza

2016-08-04

Amphetamine withdrawal (AW) is accompanied by diminished pleasure and depression which plays a key role in drug relapse and addictive behaviors. There is no efficient treatment for AW-induced depression and underpinning mechanisms were not well determined. Considering both transient receptor potential cation channel, subfamily V, member 1 (TRPV1) and N-Methyl-d-aspartate (NMDA) receptors contribute to pathophysiology of mood and addictive disorders, in this study, we investigated the role of TRPV1 and NMDA receptors in mediating depressive-like behaviors following AW in male mice. Results revealed that administration of capsaicin, TRPV1 agonist, (100μg/mouse, i.c.v.) and MK-801, NMDA receptor antagonist (0.005mg/kg, i.p.) reversed AW-induced depressive-like behaviors in forced swimming test (FST) and splash test with no effect on animals' locomotion. Co-administration of sub-effective doses of MK-801 (0.001mg/kg, i.p.) and capsaicin (10μg/mouse, i.c.v) exerted antidepressant-like effects in behavioral tests. Capsazepine, TRPV1 antagonist, (100μg/mouse, i.c.v) and NMDA, NMDA receptor agonist (7.5mg/kg, i.p.) abolished the effects of capsaicin and MK-801, respectively. None of aforementioned treatments had any effect on behavior of control animals. Collectively, our findings showed that activation of TRPV1 and blockade of NMDA receptors produced antidepressant-like effects in male mice following AW, and these receptors are involved in AW-induced depressive-like behaviors. Further, we found that rapid antidepressant-like effects of capsaicin in FST and splash test are partly mediated by NMDA receptors. Copyright © 2016. Published by Elsevier Ltd.

Implementation of a Fluorescence-Based Screening Assay Identifies Histamine H3 Receptor Antagonists Clobenpropit and Iodophenpropit as Subunit-Selective N-Methyl-d-Aspartate Receptor Antagonists

PubMed Central

Hansen, Kasper B.; Mullasseril, Praseeda; Dawit, Sara; Kurtkaya, Natalie L.; Yuan, Hongjie; Vance, Katie M.; Orr, Anna G.; Kvist, Trine; Ogden, Kevin K.; Le, Phuong; Vellano, Kimberly M.; Lewis, Iestyn; Kurtkaya, Serdar; Du, Yuhong; Qui, Min; Murphy, T. J.; Snyder, James P.; Bräuner-Osborne, Hans

2010-01-01

N-Methyl-d-aspartate (NMDA) receptors are ligand-gated ion channels that mediate a slow, Ca2+-permeable component of excitatory synaptic transmission in the central nervous system and play a pivotal role in synaptic plasticity, neuronal development, and several neurological diseases. We describe a fluorescence-based assay that measures NMDA receptor-mediated changes in intracellular calcium in a BHK-21 cell line stably expressing NMDA receptor NR2D with NR1 under the control of a tetracycline-inducible promoter (Tet-On). The assay selectively identifies allosteric modulators by using supramaximal concentrations of glutamate and glycine to minimize detection of competitive antagonists. The assay is validated by successfully identifying known noncompetitive, but not competitive NMDA receptor antagonists among 1800 screened compounds from two small focused libraries, including the commercially available library of pharmacologically active compounds. Hits from the primary screen are validated through a secondary screen that used two-electrode voltage-clamp recordings on recombinant NMDA receptors expressed in Xenopus laevis oocytes. This strategy identified several novel modulators of NMDA receptor function, including the histamine H3 receptor antagonists clobenpropit and iodophenpropit, as well as the vanilloid receptor transient receptor potential cation channel, subfamily V, member 1 (TRPV1) antagonist capsazepine. These compounds are noncompetitive antagonists and the histamine H3 receptor ligand showed submicromolar potency at NR1/NR2B NMDA receptors, which raises the possibility that compounds can be developed that act with high potency on both glutamate and histamine receptor systems simultaneously. Furthermore, it is possible that some actions attributed to histamine H3 receptor inhibition in vivo may also involve NMDA receptor antagonism. PMID:20197375

Investigating the influence of PFC transection and nicotine on dynamics of AMPA and NMDA receptors of VTA dopaminergic neurons.

PubMed

Chen, Ting; Zhang, Die; Dragomir, Andrei; Kobayashi, Kunikazu; Akay, Yasemin; Akay, Metin

2011-10-21

All drugs of abuse, including nicotine, activate the mesocorticolimbic system that plays critical roles in nicotine reward and reinforcement development and triggers glutamatergic synaptic plasticity on the dopamine (DA) neurons in the ventral tegmental area (VTA). The addictive behavior and firing pattern of the VTA DA neurons are thought to be controlled by the glutamatergic synaptic input from prefrontal cortex (PFC). Interrupted functional input from PFC to VTA was shown to decrease the effects of the drug on the addiction process. Nicotine treatment could enhance the AMPA/NMDA ratio in VTA DA neurons, which is thought as a common addiction mechanism. In this study, we investigate whether or not the lack of glutamate transmission from PFC to VTA could make any change in the effects of nicotine. We used the traditional AMPA/NMDA peak ratio, AMPA/NMDA area ratio, and KL (Kullback-Leibler) divergence analysis method for the present study. Our results using AMPA/NMDA peak ratio showed insignificant difference between PFC intact and transected and treated with saline. However, using AMPA/NMDA area ratio and KL divergence method, we observed a significant difference when PFC is interrupted with saline treatment. One possible reason for the significant effect that the PFC transection has on the synaptic responses (as indicated by the AMPA/NMDA area ratio and KL divergence) may be the loss of glutamatergic inputs. The glutamatergic input is one of the most important factors that contribute to the peak ratio level. Our results suggested that even within one hour after a single nicotine injection, the peak ratio of AMPA/NMDA on VTA DA neurons could be enhanced.

Activation of NMDA receptors in the brainstem, rostral ventromedial medulla, and nucleus reticularis gigantocellularis mediates mechanical hyperalgesia produced by repeated intramuscular injections of acidic saline in rats.

PubMed

Da Silva, Luis F; Desantana, Josimari M; Sluka, Kathleen A

2010-04-01

Repeated injections of acidic saline into the gastrocnemius muscle induce both muscle and cutaneous hypersensitivity. We have previously shown that microinjection of local anesthetic into either the rostral ventromedial medulla (RVM) or the nucleus reticularis gigantocellularis (NGC) reverses this muscle and cutaneous hypersensitivity. Although prior studies show that NMDA receptors in the RVM play a clear role in mediating visceral and inflammatory hypersensitivity, the role of NMDA receptors in the NGC or in noninflammatory muscle pain is unclear. Therefore, the present study evaluated involvement of the NMDA receptors in the RVM and NGC in muscle and cutaneous hypersensitivity induced by repeated intramuscular injections of acidic saline. Repeated intramuscular injections of acidic saline, 5 days apart, resulted in a bilateral decrease in the withdrawal thresholds of the paw and muscle in all groups 24 hours after the second injection. Microinjection of NMDA receptor antagonists into the RVM reversed both the muscle and cutaneous hypersensitivity. However, microinjection of NMDA receptor antagonists into the NGC only reversed cutaneous but not muscle hypersensitivity. These results suggest that NMDA receptors in the RVM mediate both muscle and cutaneous hypersensitivity, but those in the NGC mediate only cutaneous hypersensitivity after muscle insult. The current study shows that NMDA receptors in supraspinal facilitatory sites maintain noninflammatory muscle pain. Clinical studies in people with chronic widespread, noninflammatory pain, similarly, show alterations in central excitability. Thus, understanding mechanisms in an animal model could lead to improved treatment for patients with chronic muscle pain. Copyright 2010 American Pain Society. Published by Elsevier Inc. All rights reserved.

Opiate and N-methyl-D-aspartate receptors in form-deprivation myopia.

PubMed

Fischer, A J; Seltner, R L; Stell, W K

1998-01-01

Pharmacological studies have implicated retinal opiate pathways in the visual regulation of ocular growth. However, the effects of opiate receptor subtype-specific compounds on form-deprivation myopia (FDM) are inconsistent (Seltner et al., 1997), and may be mediated by non-opiate receptors. The purpose of this study was to test whether opiate receptor-inactive (D-) enantiomers elicit the same FDM-suppressing effect as their opiate receptor-active (L-) counterparts. Since some opiates are thought to act at NMDA receptors, we also tested whether NMDA receptor agonists and antagonists influence ocular growth or FDM. We found that both L- and D- enantiomers of morphine-like compounds (dextrorphanol and levorphanol, and D- and L-naloxone) were equally effective in blocking FDM. The NMDA receptor antagonists dextromethorphan, MK801, and AP5 also suppressed FDM. A single toxic dose of NMDA, that destroys many subtypes of amacrine cells (including those that synthesize the opioid peptide enkephalin), induced myopia and ocular enlargement in ungoggled eyes, and eliminated the ability of form-deprivation to enhance ocular growth. The NR-1 subunit of the NMDA receptor was localized to a narrowly stratified, intense stratum at approximately 50% depth in the inner plexiform layer, diffusely throughout the proximal inner plexiform layer, and to many somata in the amacrine and ganglion cell layers. These observations suggest that most effects of opiate receptor ligands on FDM in the chick are mediated by non-opiate receptors, which are likely to include NMDA receptors. NMDA as an excitotoxin transiently enhances ocular growth, but thereafter disables retinal mechanisms that promote emmetropization and FDM. These observations are consistent with a prominent role for pathways utilizing NMDA receptors in FDM and ocular growth-control.

NMDA receptor antagonists attenuate the proconvulsant effect of juvenile social isolation in male mice.

PubMed

Amiri, Shayan; Haj-Mirzaian, Arya; Amini-khoei, Hossein; Momeny, Majid; Shirzadian, Armin; Rahimi-Balaei, Maryam; Zarrinrad, Ghazaleh; Ghazi-Khansari, Mahmoud; Azizi, Romina; Dehpour, Ahmad Reza; Mehr, Shahram Ejtemaei

2016-03-01

Experiencing psychosocial stress in early life, such as social isolation stress (SIS), is known to have negative enduring effects on the development of the brain and behavior. In addition to anxiety and depressive-like behaviors, we previously showed that juvenile SIS increases susceptibility to pentylenetetrazole (PTZ)-induced seizures in mice through enhancing the nitrergic system activity in the hippocampus. In this study, we investigated the possible involvement of N-methyl-D-aspartate (NMDA) receptors in proconvulsant effects of juvenile SIS. Applying 4 weeks of SIS to juvenile male mice at postnatal day 21-23, we observed an increased susceptibility to PTZ as well as anxiety and depressive-like behaviors in adult mice. Intraperitoneal (i.p.) administration of NMDA receptor antagonists, MK-801 (0.05 mg/kg) and ketamine (0.5mg/kg), reversed the proconvulsant effects of SIS in Isolated (and not social) housed animals. Co-administration of non-effective doses of nitric oxide synthase (NOS) inhibitors, 7NI (25mg/kg) and L-NAME (10mg/kg), with NMDA receptor antagonists, MK-801 (0.01 mg/kg) and ketamine (0.1mg/kg) attenuated the proconvulsant effects of juvenile SIS only in isolated housed mice. Also, using real time RT-PCR, we showed that hippocampal upregulation of NR2B subunit of NMDA receptor may play a critical role in proconvulsant effects of juvenile SIS by dysregulation of NMDA/NO pathway. In conclusion, results of present study revealed that experiencing SIS during adolescence predisposes the co-occurrence of seizure disorders with psychiatric comorbidities and also, alteration of NMDA receptor structure and function in hippocampus plays a role in proconvulsant effects of juvenile SIS through enhancing the NMDA/NO pathway. Copyright © 2016 Elsevier Inc. All rights reserved.

Positive feedback of NR2B-containing NMDA receptor activity is the initial step toward visual imprinting: a model for juvenile learning.

PubMed

Nakamori, Tomoharu; Sato, Katsushige; Kinoshita, Masae; Kanamatsu, Tomoyuki; Sakagami, Hiroyuki; Tanaka, Kohichi; Ohki-Hamazaki, Hiroko

2015-01-01

Imprinting in chicks is a good model for elucidating the processes underlying neural plasticity changes during juvenile learning. We recently reported that neural activation of a telencephalic region, the core region of the hyperpallium densocellulare (HDCo), was critical for success of visual imprinting, and that N-Methyl-D-aspartic (NMDA) receptors containing the NR2B subunit (NR2B/NR1) in this region were essential for imprinting. Using electrophysiological and multiple-site optical imaging techniques with acute brain slices, we found that long-term potentiation (LTP) and enhancement of NR2B/NR1 currents in HDCo neurons were induced in imprinted chicks. Enhancement of NR2B/NR1 currents as well as an increase in surface NR2B expression occurred even following a brief training that was too weak to induce LTP or imprinting behavior. This means that NR2B/NR1 activation is the initial step of learning, well before the activation of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors which induces LTP. We also showed that knockdown of NR2B/NR1 inhibited imprinting, and inversely, increasing the surface NR2B expression by treatment with a casein kinase 2 inhibitor successfully reduced training time required for imprinting. These results suggest that imprinting stimuli activate post-synaptic NR2B/NR1 in HDCo cells, increase NR2B/NR1 signaling through up-regulation of its expression, and induce LTP and memory acquisition. The study investigated the neural mechanism underlying juvenile learning. In the initial stage of chick imprinting, NMDA receptors containing the NMDA receptor subunit 2B (NR2B) are activated, surface expression of NR2B/NR1 (NMDA receptor subunit 1) is up-regulated, and consequently long-term potentiation is induced in the telencephalic neurons. We suggest that the positive feedback in the NR2B/NR1 activation is a unique process of juvenile learning, exhibiting rapid memory acquisition. © 2014 International Society for Neurochemistry.

Mechanisms for Antagonistic Regulation of AMPA and NMDA-D1 Receptor Complexes at Postsynaptic Sites

NASA Technical Reports Server (NTRS)

Schumann, Johann; Scheler, Gabriele

2004-01-01

From the analysis of these pathways we conclude that postsynaptic processes that regulate synaptic transmission undergo significant cross-talk with respect to glutamatergic and neuromodulatory (dopamine) signals. The main hypothesis is that of a compensatory regulation, a competitive switch between the induction of increased AMPA conductance by CaMKII-dependent phosphorylation and reduced expression of PP2A, and increased D1 receptor sensitivity and expression by increased PKA, PP2A and decreased PP-1/calcineurin expression. Both types of plasticity are induced by NMDA receptor activation and increased internal calcium, they require different internal conditions to become expressed. Specifically we propose that AMPA regulation and D1 regulation are inversely coupled;The net result may be a bifurcation of synaptic state into predominantly AMPA or NMDA-D1 synapses. This could have functional consequences: stable connections for AMPA and conditional gating for NMDA-D1 synapses.

Memantine and Kynurenic Acid: Current Neuropharmacological Aspects

PubMed Central

Majláth, Zsófia; Török, Nóra; Toldi, József; Vécsei, László

2016-01-01

Glutamatergic neurotransmission, of special importance in the human brain, is implicated in key brain functions such as synaptic plasticity and memory. The excessive activation of N-methyl- D-aspartate (NMDA) receptors may result in excitotoxic neuronal damage; this process has been implicated in the pathomechanism of different neurodegenerative disorders, such as Alzheimer’s disease (AD). Memantine is an uncompetitive antagonist of NMDA receptors with a favorable pharmacokinetic profile, and is therefore clinically well tolerated. Memantine is approved for the treatment of AD, but may additionally be beneficial for other dementia forms and pain conditions. Kynurenic acid (KYNA) is an endogenous antagonist of NMDA receptors which has been demonstrated under experimental conditions to be neuroprotective. The development of a well-tolerated NMDA antagonist may offer a novel therapeutic option for the treatment of neurodegenerative disease and pain syndromes. KYNA may be a valuable candidate for future drug development. PMID:26564141

Cholinergic basal forebrain structures are not essential for mediation of the arousing action of glutamate.

PubMed

Lelkes, Zoltán; Abdurakhmanova, Shamsiiat; Porkka-Heiskanen, Tarja

2017-09-18

The cholinergic basal forebrain contributes to cortical activation and receives rich innervations from the ascending activating system. It is involved in the mediation of the arousing actions of noradrenaline and histamine. Glutamatergic stimulation in the basal forebrain results in cortical acetylcholine release and suppression of sleep. However, it is not known to what extent the cholinergic versus non-cholinergic basal forebrain projection neurones contribute to the arousing action of glutamate. To clarify this question, we administered N-methyl-D-aspartate (NMDA), a glutamate agonist, into the basal forebrain in intact rats and after destruction of the cholinergic cells in the basal forebrain with 192 immunoglobulin (Ig)G-saporin. In eight Han-Wistar rats with implanted electroencephalogram/electromyogram (EEG/EMG) electrodes and guide cannulas for microdialysis probes, 0.23 μg 192 IgG-saporin was administered into the basal forebrain, while the eight control animals received artificial cerebrospinal fluid. Two weeks later, a microdialysis probe targeted into the basal forebrain was perfused with cerebrospinal fluid on the baseline day and for 3 h with 0.3 mmNMDA on the subsequent day. Sleep-wake activity was recorded for 24 h on both days. NMDA exhibited a robust arousing effect in both the intact and the lesioned rats. Wakefulness was increased and both non-REM and REM sleep were decreased significantly during the 3-h NMDA perfusion. Destruction of the basal forebrain cholinergic neurones did not abolish the wake-enhancing action of NMDA. Thus, the cholinergic basal forebrain structures are not essential for the mediation of the arousing action of glutamate. © 2017 European Sleep Research Society.

Fyn kinase-mediated phosphorylation of NMDA receptor NR2B subunit at Tyr1472 is essential for maintenance of neuropathic pain.

PubMed

Abe, Tetsuya; Matsumura, Shinji; Katano, Tayo; Mabuchi, Tamaki; Takagi, Kunio; Xu, Li; Yamamoto, Akitsugu; Hattori, Kotaro; Yagi, Takeshi; Watanabe, Masahiko; Nakazawa, Takanobu; Yamamoto, Tadashi; Mishina, Masayoshi; Nakai, Yoshihide; Ito, Seiji

2005-09-01

Despite abundant evidence implicating the importance of N-methyl-D-aspartate (NMDA) receptors in the spinal cord for pain transmission, the signal transduction coupled to NMDA receptor activation is largely unknown for the neuropathic pain state that lasts over periods of weeks. To address this, we prepared mice with neuropathic pain by transection of spinal nerve L5. Wild-type, NR2A-deficient, and NR2D-deficient mice developed neuropathic pain; in addition, phosphorylation of NR2B subunits of NMDA receptors at Tyr1472 was observed in the superficial dorsal horn of the spinal cord 1 week after nerve injury. Neuropathic pain and NR2B phosphorylation at Tyr1472 were attenuated by the NR2B-selective antagonist CP-101,606 and disappeared in mice lacking Fyn kinase, a Src-family tyrosine kinase. Concomitant with the NR2B phosphorylation, an increase in neuronal nitric oxide synthase activity was visualized in the superficial dorsal horn of neuropathic pain mice by NADPH diaphorase histochemistry. Electron microscopy showed that the phosphorylated NR2B was localized at the postsynaptic density in the spinal cord of mice with neuropathic pain. Indomethacin, an inhibitor of prostaglandin (PG) synthesis, and PGE receptor subtype EP1-selective antagonist reduced the NR2B phosphorylation in these mice. Conversely, EP1-selective agonist stimulated Fyn kinase-dependent nitric oxide formation in the spinal cord. The present study demonstrates that Tyr1472 phosphorylation of NR2B subunits by Fyn kinase may have dual roles in the retention of NMDA receptors in the postsynaptic density and in activation of nitric oxide synthase, and suggests that PGE2 is involved in the maintenance of neuropathic pain via the EP1 subtype.

NMDA receptor dependent PGC-1alpha up-regulation protects the cortical neuron against oxygen-glucose deprivation/reperfusion injury.

PubMed

Luo, Yun; Zhu, Wenjing; Jia, Jia; Zhang, Chenyu; Xu, Yun

2009-09-01

The peroxisome proliferator activated receptor coactivator 1 alpha (PGC-1alpha) is a nuclear transcriptional coactivator that is widely expressed in the brain areas. Over-expression of PGC-1alpha can protect neuronal cells from oxidant-induced injury. The purpose of the current study is to investigate the role of PGC-1alpha in the oxygen (anoxia) deprivation (OGD) neurons. The PGC-1alpha mRNA and protein level between control and OGD neurons were examined by real-time PCR and Western blot. More PGC-1alpha expression was found in the OGD neurons compared with the normal group. Over-expression of PGC-1alpha suppressed cell apoptosis while inhibition of the PGC-1alpha expression induced cell apoptosis in OGD neurons. Furthermore, increase of PGC-1alpha resulted in activation of N-methyl-D-aspartate (NMDA) receptor, p38, and ERK mitogen-activated protein kinase (MAPK) pathway. The blocking of the NMDA receptor by its antagonists MK-801 reduced PGC-1alpha mRNA expression in OGD neurons, while NMDA itself can directly induce the expression of PGC-1alpha in neuronal cells. At the same time, PD98059 (ERK MAPK inhibitor) and SB203580 (P38 MAPK inhibitor) also prevented the up-regulation of PGC-1alpha in OGD neurons and MK801 can inhibit the expression of P38 and ERK MAPK. These data suggested that the expression of PGC-1alpha was up-regulated in OGD mice cortical neurons, which protected the neurons against OGD injury. Moreover, this effect was correlated to the NMDA receptor and the ERK and P38 MAPK pathway. The protective effect of PGC-1alpha on OGD cortical neurons may be useful for stroke therapy.

Modulation of inhibitory activity markers by intermittent theta-burst stimulation in rat cortex is NMDA-receptor dependent.

PubMed

Labedi, Adnan; Benali, Alia; Mix, Annika; Neubacher, Ute; Funke, Klaus

2014-01-01

Intermittent theta-burst stimulation (iTBS) applied via transcranial magnetic stimulation has been shown to increase cortical excitability in humans. In the rat brain it strongly reduced the number of neurons expressing the 67-kD isoform of the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD67) and those expressing the calcium-binding proteins parvalbumin (PV) and calbindin (CB), specific markers of fast-spiking (FS) and non-FS inhibitory interneurons, respectively, an indication of modified cortical inhibition. Since iTBS effects in humans have been shown to be NMDA receptor sensitive, we wondered whether the iTBS-induced changes in the molecular phenotype of interneurons may be also sensitive to glutamatergic synaptic transmission mediated by NMDA receptors. In a sham-controlled fashion, five iTBS-blocks of 600 stimuli were applied to rats either lightly anesthetized by only urethane or by an additional low (subnarcotic) or high dose of the NMDA receptor antagonist ketamine before immunohistochemical analysis. iTBS reduced the number of neurons expressing GAD67, PV and CB. Except for CB, a low dose of ketamine partially prevented these effects while a higher dose almost completely abolished the iTBS effects. Our findings indicate that iTBS modulates the molecular, and likely also the electric, activity of cortical inhibitory interneurons and that the modulation of FS-type but less that of non-FS-type neurons is mediated by NMDA receptors. A combination of iTBS with pharmacological interventions affecting distinct receptor subtypes may thus offer options to enhance its selectivity in modulating the activity of distinct cell types and preventing others from being modulated. Copyright © 2014 Elsevier Inc. All rights reserved.

On the Role of Glutamate in Presynaptic Development: Possible Contributions of Presynaptic NMDA Receptors.

PubMed

Fedder, Karlie N; Sabo, Shasta L

2015-12-14

Proper formation and maturation of synapses during development is a crucial step in building the functional neural circuits that underlie perception and behavior. It is well established that experience modifies circuit development. Therefore, understanding how synapse formation is controlled by synaptic activity is a key question in neuroscience. In this review, we focus on the regulation of excitatory presynaptic terminal development by glutamate, the predominant excitatory neurotransmitter in the brain. We discuss the evidence that NMDA receptor activation mediates these effects of glutamate and present the hypothesis that local activation of presynaptic NMDA receptors (preNMDARs) contributes to glutamate-dependent control of presynaptic development. Abnormal glutamate signaling and aberrant synapse development are both thought to contribute to the pathogenesis of a variety of neurodevelopmental disorders, including autism spectrum disorders, intellectual disability, epilepsy, anxiety, depression, and schizophrenia. Therefore, understanding how glutamate signaling and synapse development are linked is important for understanding the etiology of these diseases.

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

The N-methyl-D-aspartate-evoked cytoplasmic calcium increase in adult rat dorsal root ganglion neuronal somata was potentiated by substance P pretreatment in a protein kinase C-dependent manner.

PubMed

Castillo, C; Norcini, M; Baquero-Buitrago, J; Levacic, D; Medina, R; Montoya-Gacharna, J V; Blanck, T J J; Dubois, M; Recio-Pinto, E

2011-03-17

The involvement of substance P (SP) in neuronal sensitization through the activation of the neurokinin-1-receptor (NK1r) in postsynaptic dorsal horn neurons has been well established. In contrast, the role of SP and NK1r in primary sensory dorsal root ganglion (DRG) neurons, in particular in the soma, is not well understood. In this study, we evaluated whether SP modulated the NMDA-evoked transient increase in cytoplasmic Ca2+ ([Ca2+]cyt) in the soma of dissociated adult DRG neurons. Cultures were treated with nerve growth factor (NGF), prostaglandin E2 (PGE2) or both NGF+PGE2. Treatment with NGF+PGE2 increased the percentage of N-methyl-D-aspartate (NMDA) responsive neurons. There was no correlation between the percentage of NMDA responsive neurons and the level of expression of the NR1 and NR2B subunits of the NMDA receptor or of the NK1r. Pretreatment with SP did not alter the percentage of NMDA responsive neurons; while it potentiated the NMDA-evoked [Ca2+]cyt transient by increasing its magnitude and by prolonging the period during which small- and some medium-sized neurons remained NMDA responsive. The SP-mediated potentiation was blocked by the SP-antagonist ([D-Pro4, D-Trp7,9]-SP (4-11)) and by the protein kinase C (PKC) blocker bisindolylmaleimide I (BIM); and correlated with the phosphorylation of PKCε. The Nk1r agonist [Sar9, Met(O2)11]-SP (SarMet-SP) also potentiated the NMDA-evoked [Ca2+]cyt transient. Exposure to SP or SarMet-SP produced a rapid increase in the labeling of phosphorylated-PKCε. In none of the conditions we detected phosphorylation of the NR2B subunit at Ser-1303. Phosphorylation of the NR2B subunit at Tyr1472 was enhanced to a similar extent in cells exposed to NMDA, SP or NMDA+SP, and that enhancement was blocked by BIM. Our findings suggest that NGF and PGE2 may contribute to the injury-evoked sensitization of DRG neurons in part by enhancing their NMDA-evoked [Ca2+]cyt transient in all sized DRG neurons; and that SP may further contribute to the DRG sensitization by enhancing and prolonging the NMDA-evoked increase in [Ca2+]cyt in small- and medium-sized DRG neurons. Copyright © 2011 IBRO. Published by Elsevier Ltd. All rights reserved.

Differential Involvement of Amygdala and Cortical NMDA Receptors Activation upon Encoding in Odor Fear Memory

ERIC Educational Resources Information Center

Hegoburu, Chloé; Parrot, Sandrine; Ferreira, Guilaume; Mouly, Anne-Marie

2014-01-01

Although the basolateral amygdala (BLA) plays a crucial role for the acquisition of fear memories, sensory cortices are involved in their long-term storage in rats. However, the time course of their respective involvement has received little investigation. Here we assessed the role of the glutamatergic N-methyl-D-aspartate (NMDA) receptors in the…

Ligand-specific Deactivation Time Course of GluN1/GluN2D NMDA Receptors

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

K Vance; N Simorowski; S Traynelis

2011-12-31

N-methyl-D-aspartate (NMDA) receptors belong to the family of ionotropic glutamate receptors that mediate a majority of excitatory synaptic transmission. One unique property of GluN1/GluN2D NMDA receptors is an unusually prolonged deactivation time course following the removal of L-glutamate. Here we show, using x-ray crystallography and electrophysiology, that the deactivation time course of GluN1/GluN2D receptors is influenced by the conformational variability of the ligand-binding domain (LBD) as well as the structure of the activating ligand. L-glutamate and L-CCG-IV induce significantly slower deactivation time courses compared with other agonists. Crystal structures of the isolated GluN2D LBD in complex with various ligands revealmore » that the binding of L-glutamate induces a unique conformation at the backside of the ligand-binding site in proximity to the region at which the transmembrane domain would be located in the intact receptors. These data suggest that the activity of the GluN1/GluN2D NMDA receptor is controlled distinctively by the endogenous neurotransmitter L-glutamate.« less

Characterization of l-Theanine Excitatory Actions on Hippocampal Neurons: Toward the Generation of Novel N-Methyl-d-aspartate Receptor Modulators Based on Its Backbone.

PubMed

Sebih, Fatiha; Rousset, Matthieu; Bellahouel, Salima; Rolland, Marc; de Jesus Ferreira, Marie Celeste; Guiramand, Janique; Cohen-Solal, Catherine; Barbanel, Gérard; Cens, Thierry; Abouazza, Mohammed; Tassou, Adrien; Gratuze, Maud; Meusnier, Céline; Charnet, Pierre; Vignes, Michel; Rolland, Valérie

2017-08-16

l-Theanine (or l-γ-N-ethyl-glutamine) is the major amino acid found in Camellia sinensis. It has received much attention because of its pleiotropic physiological and pharmacological activities leading to health benefits in humans, especially. We describe here a new, easy, efficient, and environmentally friendly chemical synthesis of l-theanine and l-γ-N-propyl-Gln and their corresponding d-isomers. l-Theanine, and its derivatives obtained so far, exhibited partial coagonistic action at N-methyl-d-aspartate (NMDA) receptors, with no detectable agonist effect at other glutamate receptors, on cultured hippocampal neurons. This activity was retained on NMDA receptors expressed in Xenopus oocytes. In addition, both GluN2A and GluN2B containing NMDA receptors were equally modulated by l-theanine. The stereochemical change from l-theanine to d-theanine along with the substitution of the ethyl for a propyl moiety in the γ-N position of l- and d-theanine significantly enhanced the biological efficacy, as measured on cultured hippocampal neurons. l-Theanine structure thus represents an interesting backbone to develop novel NMDA receptor modulators.

Human T lymphocytes express N-methyl-D-aspartate receptors functionally active in controlling T cell activation

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

Miglio, Gianluca; Varsaldi, Federica; Lombardi, Grazia

2005-12-30

The aim of this study was to investigate the expression and the functional role of N-methyl-D-aspartate (NMDA) receptors in human T cells. RT-PCR analysis showed that human resting peripheral blood lymphocytes (PBL) and Jurkat T cells express genes encoding for both NR1 and NR2B subunits: phytohemagglutinin (PHA)-activated PBL also expresses both these genes and the NR2A and NR2D genes. Cytofluorimetric analysis showed that NR1 expression increases as a consequence of PHA (10 {mu}g/ml) treatment. D-(-)-2-Amino-5-phosphonopentanoic acid (D-AP5), and (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine [(+)-MK 801], competitive and non-competitive NMDA receptor antagonists, respectively, inhibited PHA-induced T cell proliferation, whereas they did not affect IL-2 (10more » U/ml)-induced proliferation of PHA blasts. These effects were due to the prevention of T cell activation (inhibition of cell aggregate formation and CD25 expression), but not to cell cycle arrest or death. These results demonstrate that human T lymphocytes express NMDA receptors, which are functionally active in controlling cell activation.« less

Competitive and noncompetitive antagonists at N-methyl-D-aspartate receptors protect against methamphetamine-induced dopaminergic damage in mice.

PubMed

Sonsalla, P K; Riordan, D E; Heikkila, R E

1991-02-01

The administration of methamphetamine (METH) to experimental animals results in damage to nigrostriatal dopaminergic neurons. We have demonstrated previously that the excitatory amino acids may be involved in this neurotoxicity. For example, several compounds which bind to the phenyclidine site within the ion channel linked to the N-methyl-D-aspartate (NMDA) receptor protected mice from the METH-induced loss of neostriatal tyrosine hydroxylase activity and dopamine content. The present study was conducted to characterize further the role of the excitatory amino acids in mediating the neurotoxic effects of METH. The administration of three or four injections of METH (10 mg/kg) every 2 hr to mice produced large decrements in neostriatal dopamine content (80-84%) and in tyrosine hydroxylase activity (65-74%). A dose-dependent protection against these METH-induced decreases was seen with two noncompetitive NMDA antagonists, ifenprodil and SL 82.0715 (25-50 mg/kg/injection), both of which are thought to bind to a polyamine or sigma site associated with the NMDA receptor complex, and with two competitive NMDA antagonists, CGS 19755 (25-50 mg/kg/injection) and NPC 12626 (150-300 mg/kg/injection). Moreover, an intrastriatal infusion of NMDA (0.1 mumol) produced a slight but significant loss of neostriatal dopamine which was potentiated in mice that also received a systemic injection of METH. The results of these studies strengthen the hypothesis that the excitatory amino acids play a critical role in the nigrostriatal dopaminergic damage induced by METH.

Systemic administration of dizocilpine maleate (MK-801) or L-dopa reverses the increases in GAD65 and GAD67 mRNA expression in the globus pallidus in a rat hemiparkinsonian model.

PubMed

Bacci, Jean-Jacques; Salin, Pascal; Kerkerian-Le Goff, Lydia

2002-12-15

This study examined the consequences of systemic treatment with either L-dopa or MK-801 on the levels of mRNAs encoding the 65 and 67 kDa isoforms of glutamate decarboxylase (GAD65 and GAD67) in the striatum and globus pallidus (GP) of rats rendered hemiparkinsonian by intranigral 6-hydroxydopamine injection. GADs mRNA levels were assessed by means of in situ hybridization histochemistry. In the striatum, dopamine denervation resulted in increased GAD67 mRNA levels at the rostral and caudal levels, whereas GAD65 showed selective increase at the caudal level. L-dopa and MK-801 treatments showed differential effects on the two GAD isoform levels in rats with 6-hydroxydopamine lesion. The lesion-induced increases in GAD67 transcripts were potentiated by L-dopa but unaffected by MK-801, whereas the increases in GAD65 were suppressed by MK-801 but unaffected by L-dopa. These data suggest a heterogeneity of glutamate-dopamine interaction in the anteroposterior extent of the striatum and show that NMDA-mediated mechanisms are involved in the 6-hydroxydopamine lesion-induced transcriptional changes in striatal GAD65 but not GAD67. In GP, the 6-OHDA lesion elicited increases in both GAD65 and GAD67 mRNA levels. L-dopa or MK-801 treatment suppressed the lesion-induced augmentations in the two GADs mRNA levels. These results indicate that dopamine denervation-induced changes in the functional activity of GP neurons involve both dopamine and glutamate NMDA receptor-mediated mechanisms. Comparison between the effects of L-dopa and MK-801 treatments on markers of the activity of striatal and pallidal GABA neurons further suggest that the impact of these treatments at the GP level do not depend solely on the striatopallidal input. Copyright 2002 Wiley-Liss, Inc.

NMDA-receptor dependent synaptic activation of TRPC channels in olfactory bulb granule cells

PubMed Central

Stroh, Olga; Freichel, Marc; Kretz, Oliver; Birnbaumer, Lutz; Hartmann, Jana; Egger, Veronica

2012-01-01

TRPC channels are widely expressed throughout the nervous system including the olfactory bulb where their function is largely unknown. Here we describe their contribution to central synaptic processing at the reciprocal mitral and tufted cell - granule cell microcircuit, the most abundant synapse of the mammalian olfactory bulb. Suprathreshold activation of the synapse causes sodium action potentials in mouse granule cells and a subsequent long-lasting depolarization (LLD) linked to a global dendritic postsynaptic calcium signal recorded with two-photon laser scanning microscopy. These signals are not observed after action potentials evoked by current injection in the same cells. The LLD persists in the presence of group I metabotropic glutamate receptor antagonists but is entirely absent from granule cells deficient for the NMDA receptor subunit NR1. Moreover, both depolarization and Ca2+ rise are sensitive to the blockade of NMDA receptors. The LLD and the accompanying Ca2+ rise are also absent in granule cells from mice deficient for both TRPC channel subtypes 1 and 4, whereas the deletion of either TRPC1 or TRPC4 results in only a partial reduction of the LLD. Recordings from mitral cells in the absence of both subunits reveal a reduction of asynchronous neurotransmitter release from the granule cells during recurrent inhibition. We conclude that TRPC1 and TRPC4 can be activated downstream of NMDA receptor activation and contribute to slow synaptic transmission in the olfactory bulb, including the calcium dynamics required for asynchronous release from the granule cell spine. PMID:22539836

Chronic administration of aripiprazole activates GSK3β-dependent signalling pathways, and up-regulates GABAA receptor expression and CREB1 activity in rats

PubMed Central

Pan, Bo; Huang, Xu-Feng; Deng, Chao

2016-01-01

Aripiprazole is a D2-like receptor (D2R) partial agonist with a favourable clinical profile. Previous investigations indicated that acute and short-term administration of aripiprazole had effects on PKA activity, GSK3β-dependent pathways, GABAA receptors, NMDA receptor and CREB1 in the brain. Since antipsychotics are used chronically in clinics, the present study investigated the long-term effects of chronic oral aripiprazole treatment on these cellular signalling pathways, in comparison with haloperidol (a D2R antagonist) and bifeprunox (a potent D2R partial agonist). We found that the Akt-GSK3β pathway was activated by aripiprazole and bifeprunox in the prefrontal cortex; NMDA NR2A levels were reduced by aripiprazole and haloperidol. In the nucleus accumbens, all three drugs increased Akt-GSK3β signalling; in addition, both aripiprazole and haloperidol, but not bifeprunox, increased the expression of Dvl-3, β-catenin and GABAA receptors, NMDA receptor subunits, as well as CREB1 phosphorylation levels. The results suggest that chronic oral administration of aripiprazole affects schizophrenia-related cellular signalling pathways and markers (including Akt-GSK3β signalling, Dvl-GSK3β-β-catenin signalling, GABAA receptor, NMDA receptor and CREB1) in a brain-region-dependent manner; the selective effects of aripiprazole on these signalling pathways might be associated with its unique clinical effects. PMID:27435909

Progressive brain damage, synaptic reorganization and NMDA activation in a model of epileptogenic cortical dysplasia.

PubMed

Colciaghi, Francesca; Finardi, Adele; Nobili, Paola; Locatelli, Denise; Spigolon, Giada; Battaglia, Giorgio Stefano

2014-01-01

Whether severe epilepsy could be a progressive disorder remains as yet unresolved. We previously demonstrated in a rat model of acquired focal cortical dysplasia, the methylazoxymethanol/pilocarpine - MAM/pilocarpine - rats, that the occurrence of status epilepticus (SE) and subsequent seizures fostered a pathologic process capable of modifying the morphology of cortical pyramidal neurons and NMDA receptor expression/localization. We have here extended our analysis by evaluating neocortical and hippocampal changes in MAM/pilocarpine rats at different epilepsy stages, from few days after onset up to six months of chronic epilepsy. Our findings indicate that the process triggered by SE and subsequent seizures in the malformed brain i) is steadily progressive, deeply altering neocortical and hippocampal morphology, with atrophy of neocortex and CA regions and progressive increase of granule cell layer dispersion; ii) changes dramatically the fine morphology of neurons in neocortex and hippocampus, by increasing cell size and decreasing both dendrite arborization and spine density; iii) induces reorganization of glutamatergic and GABAergic networks in both neocortex and hippocampus, favoring excitatory vs inhibitory input; iv) activates NMDA regulatory subunits. Taken together, our data indicate that, at least in experimental models of brain malformations, severe seizure activity, i.e., SE plus recurrent seizures, may lead to a widespread, steadily progressive architectural, neuronal and synaptic reorganization in the brain. They also suggest the mechanistic relevance of glutamate/NMDA hyper-activation in the seizure-related brain pathologic plasticity.

Inflammatory mediators leading to protein misfolding and uncompetitive/fast off-rate drug therapy for neurodegenerative disorders.

PubMed

Lipton, Stuart A; Gu, Zezong; Nakamura, Tomohiro

2007-01-01

Inflammatory mediators, including free radicals such as nitric oxide (NO) and reactive oxygen species (ROS), can contribute to neurodegenerative diseases in part by triggering protein misfolding. In this chapter, we will discuss a newly discovered pathway for this phenomenon and possible novel treatments. Excitotoxicity, defined as overstimulation of glutamate receptors, has been implicated in a final common pathway contributing to neuronal injury and death in a wide range of acute and chronic neurological disorders, ranging from Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), multiple sclerosis, and Alzheimer's disease (AD) to stroke and trauma. Excitotoxic cell death is due, at least in part, to excessive activation of N-methyl-d-aspartate (NMDA)-type glutamate receptors, leading to excessive Ca(2+) influx through the receptor's associated ion channel and subsequent free radical production, including NO and ROS. These free radicals can trigger a variety of injurious pathways, but newly discovered evidence suggests that some proteins are S-nitrosylated (transfer of NO to a critical thiol group), and this reaction can mimic the effect of rare genetic mutations. This posttranslational modification can contribute to protein misfolding, triggering neurodegenerative diseases. One such molecule affected is protein disulfide isomerase (PDI), an enzyme responsible for normal protein folding in the endoplasmic reticulum (ER). We found that when PDI is S-nitrosylation (forming SNO-PDI), the function of the enzyme is compromised, leading to misfolded proteins and contributing to neuronal cell injury and loss. Moreover, SNO-PDI occurs at pathological levels in several human diseases, including AD and PD. This discovery thus links protein misfolding to excitotoxicity and free radical formation in a number of neurodegenerative disorders. Another molecule whose S-nitrosylation can lead to abnormal protein accumulation is the E3 ubiquitin ligase, parkin, which contributes to the pathogenesis of PD. One way to ameliorate excessive NO production and hence abnormal S-nitrosylations would be to inhibit NMDA receptors. In fact, blockade of excessive NMDA receptor activity can in large measure protect neurons from this type of injury and death. However, inhibition of the NMDA receptor by high-affinity antagonists also blocks the receptor's normal function in synaptic transmission and leads to unacceptable side effects. For this reason, many NMDA receptor antagonists have disappointingly failed in advanced clinical trials. Our group was the first to demonstrate that gentle blockade of NMDA receptors by memantine, via a mechanism of uncompetitive open-channel block with a rapid "off-rate," can prevent this type of damage in a clinically efficacious manner without substantial side effects. For these Uncompetitive/Fast Off-rate therapeutics, we use the term "UFO drugs" because like Unidentified Flying Objects, they leave very quickly as soon as their job is finished. As a result, memantine blocks excessive NMDA receptor activity without disrupting normal activity. Memantine does this by preferentially entering the receptor-associated ion channel when it is excessively open, and, most importantly, when its off-rate from the channel is relatively fast so that it does not accumulate to interfere with normal synaptic transmission. Hence, memantine is clinically well tolerated, has been used in Europe for PD for many years, and recently passed multiple phase III trials for dementia, leading to its approval by the FDA and European Union for moderate-to-severe AD. Clinical studies of memantine for additional neurological disorders, including other dementias, neuropathic pain, and glaucoma, are underway. We have also developed a series of second-generation drugs that display greater neuroprotective properties than memantine. These second-generation drugs take advantage of the fact that the NMDA receptor has other modulatory sites, including critical thiol groups that are S-nitrosylated. In this case, in contrast to PDI or parkin, S-nitrosylation proves to be neuroprotective by decreasing excessive NMDA receptor activity. Targeted S-nitrosylation of the NMDA receptor can be achieved by coupling NO to memantine, yielding second-generation "UFO drugs" known as NitroMemantines.

Prolonged exposure of cortical neurons to oligomeric amyloid-β impairs NMDA receptor function via NADPH oxidase-mediated ROS production: protective effect of green tea (–)-epigallocatechin-3-gallate

PubMed Central

He, Yan; Cui, Jiankun; Lee, James C-M; Ding, Shinghua; Chalimoniuk, Malgorzata; Simonyi, Agnes; Sun, Albert Y; Gu, Zezong; Weisman∥, Gary A; Gibson Wood, W; Sun, Grace Y

2011-01-01

Excessive production of Aβ (amyloid β-peptide) has been shown to play an important role in the pathogenesis of AD (Alzheimer's disease). Although not yet well understood, aggregation of Aβ is known to cause toxicity to neurons. Our recent study demonstrated the ability for oligomeric Aβ to stimulate the production of ROS (reactive oxygen species) in neurons through an NMDA (N-methyl-d-aspartate)-dependent pathway. However, whether prolonged exposure of neurons to aggregated Aβ is associated with impairment of NMDA receptor function has not been extensively investigated. In the present study, we show that prolonged exposure of primary cortical neurons to Aβ oligomers caused mitochondrial dysfunction, an attenuation of NMDA receptor-mediated Ca2+ influx and inhibition of NMDA-induced AA (arachidonic acid) release. Mitochondrial dysfunction and the decrease in NMDA receptor activity due to oligomeric Aβ are associated with an increase in ROS production. Gp91ds-tat, a specific peptide inhibitor of NADPH oxidase, and Mn(III)-tetrakis(4-benzoic acid)-porphyrin chloride, an ROS scavenger, effectively abrogated Aβ-induced ROS production. Furthermore, Aβ-induced mitochondrial dysfunction, impairment of NMDA Ca2+ influx and ROS production were prevented by pre-treatment of neurons with EGCG [(−)-epigallocatechin-3-gallate], a major polyphenolic component of green tea. Taken together, these results support a role for NADPH oxidase-mediated ROS production in the cytotoxic effects of Aβ, and demonstrate the therapeutic potential of EGCG and other dietary polyphenols in delaying onset or retarding the progression of AD. PMID:21434871

Timosaponin derivative YY-23 acts as a non-competitive NMDA receptor antagonist and exerts a rapid antidepressant-like effect in mice.

PubMed

Zhang, Qi; Guo, Fei; Fu, Zhi-wen; Zhang, Bing; Huang, Cheng-gang; Li, Yang

2016-02-01

N-methyl-D-aspartic acid (NMDA) receptor modulators have shown promising results as potential antidepressant agents, whereas timosaponins extracted from the Chinese herb Rhizoma Anemarrhenae exhibit antidepressant activities. In the present study we examined whether YY-23, a modified metabolite of timosaponin B-III, could affect NMDA receptors in rat hippocampal neurons in vitro, and evaluated its antidepressant-like effects in stressed mice. NMDA-induced currents were recorded in acutely dissociated rat hippocampal CA1 neurons using a whole-cell recording technique. C57BL/6 mice were exposed to a 6-week chronic mild stress (CMS) or a 10-d chronic social defeat stress (CSDS). The stressed mice were treated with YY-23 (20 mg·kg(-1)·d(-1)) or a positive-control drug, fluoxetine (10 mg·kg(-1)·d(-1)) for 3 weeks. Behavioral assessments were carried out every week. In acutely dissociated rat hippocampal CA1 neurons, YY-23 selectively and reversibly inhibited NMDA-induced currents with an EC50 value of 2.8 μmol/L. This inhibition of NMDA-induced currents by YY-23 was non-competitive, and had no features of voltage-dependency or use-dependency. Treatment of the stressed mice with YY-23 not only reversed CMS-induced deficiency of sucrose preference and immobility time, and CSDS-induced reduction of social interaction, but also had faster onset as compared to fluoxetine. YY-23 is a novel non-competitive antagonist of NMDA receptors with promising rapid antidepressant-like effects in mouse models of CMS and CSDS depression.

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.

Vesicular glutamate release from central axons contributes to myelin damage.

PubMed

Doyle, Sean; Hansen, Daniel Bloch; Vella, Jasmine; Bond, Peter; Harper, Glenn; Zammit, Christian; Valentino, Mario; Fern, Robert

2018-03-12

The axon myelin sheath is prone to injury associated with N-methyl-D-aspartate (NMDA)-type glutamate receptor activation but the source of glutamate in this context is unknown. Myelin damage results in permanent action potential loss and severe functional deficit in the white matter of the CNS, for example in ischemic stroke. Here, we show that in rats and mice, ischemic conditions trigger activation of myelinic NMDA receptors incorporating GluN2C/D subunits following release of axonal vesicular glutamate into the peri-axonal space under the myelin sheath. Glial sources of glutamate such as reverse transport did not contribute significantly to this phenomenon. We demonstrate selective myelin uptake and retention of a GluN2C/D NMDA receptor negative allosteric modulator that shields myelin from ischemic injury. The findings potentially support a rational approach toward a low-impact prophylactic therapy to protect patients at risk of stroke and other forms of excitotoxic injury.

A predictive coding account of MMN reduction in schizophrenia.

PubMed

Wacongne, Catherine

2016-04-01

The mismatch negativity (MMN) is thought to be an index of the automatic activation of a specialized network for active prediction and deviance detection in the auditory cortex. It is consistently reduced in schizophrenic patients and has received a lot of interest as a clinical and translational tool. The main neuronal hypothesis regarding the mechanisms leading to a reduced MMN in schizophrenic patients is a dysfunction of NMDA receptors (NMDA-R). However, this hypothesis has never been implemented in a neuronal model. In this paper, we examine the consequences of NMDA-R dysfunction in a neuronal model of MMN based on predictive coding principle. I also investigate how predictive processes may interact with synaptic adaptation in MMN generations and examine the consequences of this interaction for the use of MMN paradigms in schizophrenia research. Copyright © 2015 Elsevier B.V. All rights reserved.

Control of cortical neuronal migration by glutamate and GABA

PubMed Central

Luhmann, Heiko J.; Fukuda, A.; Kilb, W.

2015-01-01

Neuronal migration in the cortex is controlled by the paracrine action of the classical neurotransmitters glutamate and GABA. Glutamate controls radial migration of pyramidal neurons by acting primarily on NMDA receptors and regulates tangential migration of inhibitory interneurons by activating non-NMDA and NMDA receptors. GABA, acting on ionotropic GABAA-rho and GABAA receptors, has a dichotomic action on radially migrating neurons by acting as a GO signal in lower layers and as a STOP signal in upper cortical plate (CP), respectively. Metabotropic GABAB receptors promote radial migration into the CP and tangential migration of interneurons. Besides GABA, the endogenous GABAergic agonist taurine is a relevant agonist controlling radial migration. To a smaller extent glycine receptor activation can also influence radial and tangential migration. Activation of glutamate and GABA receptors causes increases in intracellular Ca2+ transients, which promote neuronal migration by acting on the cytoskeleton. Pharmacological or genetic manipulation of glutamate or GABA receptors during early corticogenesis induce heterotopic cell clusters in upper layers and loss of cortical lamination, i.e., neuronal migration disorders which can be associated with neurological or neuropsychiatric diseases. The pivotal role of NMDA and ionotropic GABA receptors in cortical neuronal migration is of major clinical relevance, since a number of drugs acting on these receptors (e.g., anti-epileptics, anesthetics, alcohol) may disturb the normal migration pattern when present during early corticogenesis. PMID:25688185

MMP-9 Serum Levels in Schizophrenic Patients during Treatment Augmentation with Sarcosine (Results of the PULSAR Study).

PubMed

Strzelecki, Dominik; Kałużyńska, Olga; Szyburska, Justyna; Wysokiński, Adam

2016-07-09

Find changes in matrix metallopeptidase-9 (MMP-9) levels during augmentation of antipsychotic treatment with sarcosine and a relationship between schizophrenia symptoms severity and initial level of MMP-9. Fifty-eight patients with diagnosis of schizophrenia with predominant negative symptoms participated in a six-month prospective RCT (randomized controlled trial). The patients received two grams of sarcosine (n = 28) or placebo (n = 30) daily. At the beginning, after six weeks and after six months MMP-9 levels were measured. Severity of symptomatology was assessed with the Positive and Negative Syndrome Scale (PANSS) and Calgary Depression Scale for Schizophrenia (CDSS). MMP-9 serum levels were stable after six weeks and six months in both groups. We noted improvement in negative symptoms, general psychopathology and total PANSS score in sarcosine group compared to placebo; however, there was no correlations between serum MMP-9 concentrations and PANSS scores in all assessments. Initial serum MMP-9 concentrations cannot be used as an improvement predictor acquired during sarcosine augmentation. Our results indicate that either MMP-9 is not involved in the N-methyl-d-aspartate (NMDA)-dependent mechanism of sarcosine action in terms of clinical parameters or sarcosine induced changes in peripheral MMP-9 concentrations cannot be detected in blood assessments.

Neuropathological Responses to Chronic NMDA in Rats Are Worsened by Dietary n-3 PUFA Deprivation but Are Not Ameliorated by Fish Oil Supplementation

PubMed Central

Kim, Hyung-Wook; Taha, Ameer Y.; Cheon, Yewon; Igarashi, Miki; Rapoport, Stanley I.; Rao, Jagadeesh S.

2014-01-01

Background Dietary long-chain n-3 polyunsaturated fatty acid (PUFA) supplementation may be beneficial for chronic brain illnesses, but the issue is not agreed on. We examined effects of dietary n-3 PUFA deprivation or supplementation, compared with an n-3 PUFA adequate diet (containing alpha-linolenic acid [18:3 n-3] but not docosahexaenoic acid [DHA, 22:6n-3]), on brain markers of lipid metabolism and excitotoxicity, in rats treated chronically with NMDA or saline. Methods Male rats after weaning were maintained on one of three diets for 15 weeks. After 12 weeks, each diet group was injected i.p. daily with saline (1 ml/kg) or a subconvulsive dose of NMDA (25 mg/kg) for 3 additional weeks. Then, brain fatty acid concentrations and various markers of excitotoxicity and fatty acid metabolism were measured. Results Compared to the diet-adequate group, brain DHA concentration was reduced, while n-6 docosapentaenoic acid (DPA, 22:5n-6) concentration was increased in the n-3 deficient group; arachidonic acid (AA, 20:4n-6) concentration was unchanged. These concentrations were unaffected by fish oil supplementation. Chronic NMDA increased brain cPLA2 activity in each of the three groups, but n-3 PUFA deprivation or fish oil did not change cPLA2 activity or protein compared with the adequate group. sPLA2 expression was unchanged in the three conditions, whereas iPLA2 expression was reduced by deprivation but not changed by supplementation. BDNF protein was reduced by NMDA in N-3 PUFA deficient rats, but protein levels of IL-1β, NGF, and GFAP did not differ between groups. Conclusions N-3 PUFA deprivation significantly worsened several pathological NMDA-induced changes produced in diet adequate rats, whereas n-3 PUFA supplementation did not affect NMDA induced changes. Supplementation may not be critical for this measured neuropathology once the diet has an adequate n-3 PUFA content. PMID:24798187

Blonanserin ameliorates phencyclidine-induced visual-recognition memory deficits: the complex mechanism of blonanserin action involving D₃-5-HT₂A and D₁-NMDA receptors in the mPFC.

PubMed

Hida, Hirotake; Mouri, Akihiro; Mori, Kentaro; Matsumoto, Yurie; Seki, Takeshi; Taniguchi, Masayuki; Yamada, Kiyofumi; Iwamoto, Kunihiro; Ozaki, Norio; Nabeshima, Toshitaka; Noda, Yukihiro

2015-02-01

Blonanserin differs from currently used serotonin 5-HT₂A/dopamine-D₂ receptor antagonists in that it exhibits higher affinity for dopamine-D₂/₃ receptors than for serotonin 5-HT₂A receptors. We investigated the involvement of dopamine-D₃ receptors in the effects of blonanserin on cognitive impairment in an animal model of schizophrenia. We also sought to elucidate the molecular mechanism underlying this involvement. Blonanserin, as well as olanzapine, significantly ameliorated phencyclidine (PCP)-induced impairment of visual-recognition memory, as demonstrated by the novel-object recognition test (NORT) and increased extracellular dopamine levels in the medial prefrontal cortex (mPFC). With blonanserin, both of these effects were antagonized by DOI (a serotonin 5-HT₂A receptor agonist) and 7-OH-DPAT (a dopamine-D₃ receptor agonist), whereas the effects of olanzapine were antagonized by DOI but not by 7-OH-DPAT. The ameliorating effect was also antagonized by SCH23390 (a dopamine-D₁ receptor antagonist) and H-89 (a protein kinase A (PKA) inhibitor). Blonanserin significantly remediated the decrease in phosphorylation levels of PKA at Thr(197) and of NR1 (an essential subunit of N-methyl-D-aspartate (NMDA) receptors) at Ser(897) by PKA in the mPFC after a NORT training session in the PCP-administered mice. There were no differences in the levels of NR1 phosphorylated at Ser(896) by PKC in any group. These results suggest that the ameliorating effect of blonanserin on PCP-induced cognitive impairment is associated with indirect functional stimulation of the dopamine-D₁-PKA-NMDA receptor pathway following augmentation of dopaminergic neurotransmission due to inhibition of both dopamine-D₃ and serotonin 5-HT₂A receptors in the mPFC.

Different effects of isolation-rearing and neonatal MK-801 treatment on attentional modulations of prepulse inhibition of startle in rats.

PubMed

Wu, Zhe-Meng; Ding, Yu; Jia, Hong-Xiao; Li, Liang

2016-09-01

Prepulse inhibition (PPI) is suppression of the startle reflex by a weaker sensory stimulus (prepulse) preceding the startling stimulus. In people with schizophrenia, impairment of attentional modulation of PPI, but not impairment of baseline PPI, is correlated with symptom severity. In rats, both fear conditioning of prepulse and perceptually spatial separation between the conditioned prepulse and a noise masker enhance PPI (the paradigms of attentional modulation of PPI). As a neurodevelopmental model of schizophrenia, isolation rearing impairs both baseline PPI and attentional modulations of PPI in rats. This study examined in Sprague-Dawley male rats whether neonatally blocking N-methyl-D-aspartate (NMDA) receptors specifically affects attentional modulations of PPI during adulthood. Both socially reared rats with neonatal exposure to the NMDA receptor antagonist MK-801 and isolation-reared rats exhibited augmented startle responses, but only isolation rearing impaired baseline PPI. Fear conditioning of the prepulse enhanced PPI in socially reared rats, but MK-801-treated rats lost the prepulse feature specificity. Perceptually spatial separation between the conditioned prepulse and a noise masker further enhanced PPI only in normally reared rats. Clozapine administration during adulthood generally weakened startle, enhanced baseline PPI in neonatally interrupted rats, and restored the fear conditioning-induced PPI enhancement in isolation-reared rats with a loss of the prepulse feature specificity. Clozapine administration also abolished both the perceptual separation-induced PPI enhancement in normally reared rats and the fear conditioning-induced PPI enhancement in MK-801-treated rats. Isolation rearing impairs both baseline PPI and attentional modulations of PPI, but neonatally disrupting NMDA receptor-mediated transmissions specifically impair attentional modulations of PPI. Clozapine has limited alleviating effects.

Periadolescent exposure to the NMDA antagonist MK-801 impairs the functional maturation of local GABAergic circuits in the adult prefrontal cortex

PubMed Central

Thomases, Daniel R.; Cass, Daryn K.; Tseng, Kuei Y.

2012-01-01

A developmental disruption of prefrontal cortical (PFC) inhibitory circuits is thought to contribute to the adolescent onset of cognitive deficits observed in schizophrenia. However, the developmental mechanisms underlying such a disruption remain elusive. The goal of this study is to examine how repeated exposure to the NMDA receptor antagonist dizocilpine maleate (MK-801) during periadolescence (from postnatal days -PD- 35-40) impacts the normative development of local prefrontal network response in rats. In vivo electrophysiological analyses revealed that MK-801 administration during periadolescence elicits an enduring disinhibited prefrontal local field potential response to ventral hippocampal stimulation at 20Hz (beta) and 40Hz (gamma) in adulthood (PD65-85). Such a disinhibition was not observed when MK-801 was given during adulthood, indicating that the periadolescent transition is indeed a sensitive period for the functional maturation of prefrontal inhibitory control. Accordingly, the pattern of prefrontal local field potential disinhibition induced by periadolescent MK-801 treatment resembles that observed in the normal PD30-40 PFC. Further pharmacological manipulations revealed that these developmentally immature prefrontal responses can be mimicked by single microinfusion of the GABA-A receptor antagonist picrotoxin into the normal adult PFC. Importantly, acute administration of the GABA-A positive allosteric modulator Indiplon into the PFC reversed the prefrontal disinhibitory state induced by periadolescent MK-801 to normal levels. Together, these results indicate a critical role of NMDA receptors in regulating the periadolescent maturation of GABAergic networks in the PFC, and that pharmacologically-induced augmentation of local GABA-A receptor-mediated transmission is sufficient to overcome the disinhibitory prefrontal state associated with the periadolescent MK-801 exposure. PMID:23283319

Extinction of Conditioned Taste Aversion Depends on Functional Protein Synthesis but Not on NMDA Receptor Activation in the Ventromedial Prefrontal Cortex

ERIC Educational Resources Information Center

Akirav, Irit; Khatsrinov, Vicktoria; Vouimba, Rose-Marie; Merhav, Maayan; Ferreira, Guillaume; Rosenblum, Kobi; Maroun, Mouna

2006-01-01

We investigated the role of the ventromedial prefrontal cortex (vmPFC) in extinction of conditioned taste aversion (CTA) by microinfusing a protein synthesis inhibitor or N-methyl-d-asparate (NMDA) receptors antagonist into the vmPFC immediately following a non-reinforced extinction session. We found that the protein synthesis blocker anisomycin,…

[The role of gamma-aminobutyric acid in the mechanism of action of anticonvulsant drugs].

PubMed

Chmielewska, B

2000-01-01

Decreased activity of gamma-aminobutyric acid, the major inhibitory neurotransmitter in CNS can be epileptogenic. Manipulation of the GABA system has been a target for development of antiepileptic drugs. The different ways for augmenting gabaergic inhibition by conventional and new AEDs are presented in this paper. Among the I generation, barbiturates and benzodiazepines are potent anticonvulsants that act as GABA modulators in postsynaptic GABA-A receptor complex but their usefulness is limited by dependence and tolerance to antiseizure activity. The II generation drugs vigabatrin and tiagabine, and to some extent gabapentin have been developed by a rationale strategy and none of them exert direct action in GABA receptors. Only two former drugs exhibit selective, strictly defined activity: vigabatrine is an irreversible inhibitor of GABA-aminotransferase and tiagabine acts as a GABA-uptake inhibitor from synaptic cleft into neurons and glia. Gabapentin binds to a novel receptors in epileptogenic areas in CNS and enhances GABA turnover. Drugs with multiple mechanisms of action, felbamate and topiramate not only potentiate gabaergic inhibition in several ways but also diminish the activity of excitatory amino acids at their NMDA or AMPA receptors; the later mechanism seems to be essential for their potential neuroprotective activity in epileptogenesis. None of gabamimetic drugs provide optimal seizure control but better tolerability of newer ones and well-established mechanisms of action provide possible harmless therapy.

NMDA Receptors Regulate Genes Responsible for Major Immune Functions of Mononuclears in Human Peripheral Blood.

PubMed

Kuzmina, U Sh; Zainullina, L F; Sadovnikov, S V; Vakhitov, V A; Vakhitova, Yu V

2018-06-19

To determine the role of NMDA receptors in the functional regulation of immunocompetent cells, comparative assay was carried out for genes expressed in the mononuclears in peripheral blood of healthy persons under normal conditions and after blockade of these receptors. The genes, whose expression changed in response to blockade of NMDA receptors in mononuclears, encode the products involved in regulation of the major functions of immune cells, such as proliferation (IL4, VCAM1, and CDKN2A), apoptosis (BAX, MYC, CDKN2A, HSPB1, and CADD45A), activation (IL4R, IL4, VCAM1, and CDKN2A), and differentiation (IL4, VCAM1, and BAX).

Chronic MK-801 Application in Adolescence and Early Adulthood: A Spatial Working Memory Deficit in Adult Long-Evans Rats But No Changes in the Hippocampal NMDA Receptor Subunits

PubMed Central

Uttl, Libor; Petrasek, Tomas; Sengul, Hilal; Svojanovska, Marketa; Lobellova, Veronika; Vales, Karel; Radostova, Dominika; Tsenov, Grygoriy; Kubova, Hana; Mikulecka, Anna; Svoboda, Jan; Stuchlik, Ales

2018-01-01

The role of NMDA receptors in learning, memory and hippocampal function has long been recognized. Post-mortem studies have indicated that the expression or subunit composition of the NMDA glutamate receptor subtype might be related to the impaired cognitive functions found in schizophrenia patients. NMDA receptor antagonists have been used to develop animal models of this disorder. There is accumulating evidence showing that not only the acute but also the chronic application of NMDA receptor antagonists may induce schizophrenia-like alterations in behavior and brain functions. However, limited evidence is available regarding the consequences of NMDA receptor blockage during periods of adolescence and early adulthood. This study tested the hypothesis that a 2-week treatment of male Long-Evans and Wistar rats with dizocilpine (MK-801; 0.5 mg/kg daily) starting at postnatal days (PD) 30 and 60 would cause a long-term cognitive deficit and changes in the levels of NMDA receptor subunits. The working memory version of the Morris water maze (MWM) and active place avoidance with reversal on a rotating arena (Carousel) requiring cognitive coordination and flexibility probed cognitive functions and an elevated-plus maze (EPM) was used to measure anxiety-like behavior. The western blot method was used to determine changes in NMDA receptor subunit levels in the hippocampus. Our results showed no significant changes in behaviors in Wistar rats. Slightly elevated anxiety-like behavior was observed in the EPM in Long-Evans rats with the onset of treatment on PD 30. Furthermore, Long-Evans rats treated from PD 60 displayed impaired working memory in the MWM. There were; however, no significant changes in the levels of NMDA receptor subunits because of MK-801 administration. These findings suggest that a 2-week treatment starting on PD 60 in Long-Evans rats leads to long-term changes in working memory, but this deficit is not paralleled by changes in NMDA receptor subunits. These results support the face validity, but not construct validity of this model. We suggest that chronic treatment of adolescent and adult rats does not constitute a plausible animal model of schizophrenia. PMID:29487522

Chronic MK-801 Application in Adolescence and Early Adulthood: A Spatial Working Memory Deficit in Adult Long-Evans Rats But No Changes in the Hippocampal NMDA Receptor Subunits.

PubMed

Uttl, Libor; Petrasek, Tomas; Sengul, Hilal; Svojanovska, Marketa; Lobellova, Veronika; Vales, Karel; Radostova, Dominika; Tsenov, Grygoriy; Kubova, Hana; Mikulecka, Anna; Svoboda, Jan; Stuchlik, Ales

2018-01-01

The role of NMDA receptors in learning, memory and hippocampal function has long been recognized. Post-mortem studies have indicated that the expression or subunit composition of the NMDA glutamate receptor subtype might be related to the impaired cognitive functions found in schizophrenia patients. NMDA receptor antagonists have been used to develop animal models of this disorder. There is accumulating evidence showing that not only the acute but also the chronic application of NMDA receptor antagonists may induce schizophrenia-like alterations in behavior and brain functions. However, limited evidence is available regarding the consequences of NMDA receptor blockage during periods of adolescence and early adulthood. This study tested the hypothesis that a 2-week treatment of male Long-Evans and Wistar rats with dizocilpine (MK-801; 0.5 mg/kg daily) starting at postnatal days (PD) 30 and 60 would cause a long-term cognitive deficit and changes in the levels of NMDA receptor subunits. The working memory version of the Morris water maze (MWM) and active place avoidance with reversal on a rotating arena (Carousel) requiring cognitive coordination and flexibility probed cognitive functions and an elevated-plus maze (EPM) was used to measure anxiety-like behavior. The western blot method was used to determine changes in NMDA receptor subunit levels in the hippocampus. Our results showed no significant changes in behaviors in Wistar rats. Slightly elevated anxiety-like behavior was observed in the EPM in Long-Evans rats with the onset of treatment on PD 30. Furthermore, Long-Evans rats treated from PD 60 displayed impaired working memory in the MWM. There were; however, no significant changes in the levels of NMDA receptor subunits because of MK-801 administration. These findings suggest that a 2-week treatment starting on PD 60 in Long-Evans rats leads to long-term changes in working memory, but this deficit is not paralleled by changes in NMDA receptor subunits. These results support the face validity, but not construct validity of this model. We suggest that chronic treatment of adolescent and adult rats does not constitute a plausible animal model of schizophrenia.

The role of GluN2B-containing NMDA receptors in short- and long-term fear recall.

PubMed

Mikics, Eva; Toth, Mate; Biro, Laszlo; Bruzsik, Biborka; Nagy, Boglarka; Haller, Jozsef

2017-08-01

N-methyl-d-aspartate (NMDA) receptors are crucial synaptic elements in long-term memory formation, including the associative learning of fearful events. Although NMDA blockers were consistently shown to inhibit fear memory acquisition and recall, the clinical use of general NMDA blockers is hampered by their side effects. Recent studies revealed significant heterogeneity in the distribution and neurophysiological characteristics of NMDA receptors with different GluN2 (NR2) subunit composition, which may have differential role in fear learning and recall. To investigate the specific role of NMDA receptor subpopulations with different GluN2 subunit compositions in the formation of lasting traumatic memories, we contrasted the effects of general NMDA receptor blockade with GluN2A-, GluN2B-, and GluN2C/D subunit selective antagonists (MK-801, PEAQX, Ro25-6981, PPDA, respectively). To investigate acute and lasting consequences, behavioral responses were investigated 1 and 28days after fear conditioning. We found that MK-801 (0.05 and 0.1mg/kg) decreased fear recall at both time points. GluN2B receptor subunit blockade produced highly similar effects, albeit efficacy was somewhat smaller 28days after fear conditioning. Unlike MK-801, Ro25-6981 (3 and 10mg/kg) did not affect locomotor activity in the open-field. In contrast, GluN2A and GluN2C/D blockers (6 and 20mg/kg PEAQX; 3 and 10mg/kg PPDA, respectively) had no effect on conditioned fear recall at any time point and dose. This sharp contrast between GluN2B- and other subunit-containing NMDA receptor function indicates that GluN2B receptor subunits are intimately involved in fear memory formation, and may provide a novel pharmacological target in post-traumatic stress disorder or other fear-related disorders. Copyright © 2017 Elsevier Inc. All rights reserved.

Motor impairments, striatal degeneration, and altered dopamine-glutamate interplay in mice lacking PSD-95.

PubMed

Zhang, Jingping; Saur, Taixiang; Duke, Angela N; Grant, Seth G N; Platt, Donna M; Rowlett, James K; Isacson, Ole; Yao, Wei-Dong

2014-01-01

Excessive activation of the N-methyl-d-aspartate (NMDA) receptor and the neurotransmitter dopamine (DA) mediate neurotoxicity and neurodegeneration under many neurological conditions, including Huntington's disease (HD), an autosomal dominant neurodegenerative disease characterized by the preferential loss of medium spiny projection neurons (MSNs) in the striatum. PSD-95 is a major scaffolding protein in the postsynaptic density (PSD) of dendritic spines, where a classical role for PSD-95 is to stabilize glutamate receptors at sites of synaptic transmission. Our recent studies indicate that PSD-95 also interacts with the D1 DA receptor localized in spines and negatively regulates spine D1 signaling. Moreover, PSD-95 forms ternary protein complexes with D1 and NMDA receptors, and plays a role in limiting the reciprocal potentiation between both receptors from being escalated. These studies suggest a neuroprotective role for PSD-95. Here we show that mice lacking PSD-95, resulting from genetic deletion of the GK domain of PSD-95 (PSD-95-ΔGK mice), sporadically develop progressive neurological impairments characterized by hypolocomotion, limb clasping, and loss of DARPP-32-positive MSNs. Electrophysiological experiments indicated that NMDA receptors in mutant MSNs were overactive, suggested by larger, NMDA receptor-mediated miniature excitatory postsynaptic currents (EPSCs) and higher ratios of NMDA- to AMPA-mediated corticostriatal synaptic transmission. In addition, NMDA receptor currents in mutant cortical neurons were more sensitive to potentiation by the D1 receptor agonist SKF81297. Finally, repeated administration of the psychostimulant cocaine at a dose regimen not producing overt toxicity-related phenotypes in normal mice reliably converted asymptomatic mutant mice to clasping symptomatic mice. These results support the hypothesis that deletion of PSD-95 in mutant mice produces concomitant overactivation of both D1 and NMDA receptors that makes neurons more susceptible to NMDA excitotoxicity, causing neuronal damage and neurological impairments. Understanding PSD-95-dependent neuroprotective mechanisms may help elucidate processes underlying neurodegeneration in HD and other neurological disorders.

Induction of c-Fos immunoreactivity in the amygdala of mice expressing anxiety-like behavior after local perfusion of veratrine in the prelimbic medial prefrontal cortex.

PubMed

Yamada, Misa; Saitoh, Akiyoshi; Ohashi, Masanori; Suzuki, Satoshi; Oka, Jun-Ichiro; Yamada, Mitsuhiko

2015-08-01

Local perfusion of the sodium channel activator veratrine in mouse prelimbic medial prefrontal cortex (PL) induced c-Fos immunoreactivity in the sub-regions of amygdala. Co-perfusion of the NMDA receptor antagonist MK-801 diminished the c-Fos expression. Significant correlations were observed between c-Fos immunoreactivity and behavioral measures in the open-field test. The PL stimulation activates a neural network projecting to the amygdala via NMDA receptor-mediated glutamatergic neurotransmission. Anxiety-like behavior induced after the PL stimulation may be partly mediated through the activation of amygdala.

Methylphenidate enhances NMDA-receptor response in medial prefrontal cortex via sigma-1 receptor: a novel mechanism for methylphenidate action.

PubMed

Zhang, Chun-Lei; Feng, Ze-Jun; Liu, Yue; Ji, Xiao-Hua; Peng, Ji-Yun; Zhang, Xue-Han; Zhen, Xue-Chu; Li, Bao-Ming

2012-01-01

Methylphenidate (MPH), commercially called Ritalin or Concerta, has been widely used as a drug for Attention Deficit Hyperactivity Disorder (ADHD). Noteworthily, growing numbers of young people using prescribed MPH improperly for pleasurable enhancement, take high risk of addiction. Thus, understanding the mechanism underlying high level of MPH action in the brain becomes an important goal nowadays. As a blocker of catecholamine transporters, its therapeutic effect is explained as being due to proper modulation of D1 and α2A receptor. Here we showed that higher dose of MPH facilitates NMDA-receptor mediated synaptic transmission via a catecholamine-independent mechanism, in layer V∼VI pyramidal cells of the rat medial prefrontal cortex (PFC). To indicate its postsynaptic action, we next found that MPH facilitates NMDA-induced current and such facilitation could be blocked by σ1 but not D1/5 and α2 receptor antagonists. And this MPH eliciting enhancement of NMDA-receptor activity involves PLC, PKC and IP3 receptor mediated intracellular Ca(2+) increase, but does not require PKA and extracellular Ca(2+) influx. Our additional pharmacological studies confirmed that higher dose of MPH increases locomotor activity via interacting with σ1 receptor. Together, the present study demonstrates for the first time that MPH facilitates NMDA-receptor mediated synaptic transmission via σ1 receptor, and such facilitation requires PLC/IP3/PKC signaling pathway. This novel mechanism possibly explains the underlying mechanism for MPH induced addictive potential and other psychiatric side effects.

Methylphenidate Enhances NMDA-Receptor Response in Medial Prefrontal Cortex via Sigma-1 Receptor: A Novel Mechanism for Methylphenidate Action

PubMed Central

Liu, Yue; Ji, Xiao-Hua; Peng, Ji-Yun; Zhang, Xue-Han; Zhen, Xue-Chu; Li, Bao-Ming

2012-01-01

Methylphenidate (MPH), commercially called Ritalin or Concerta, has been widely used as a drug for Attention Deficit Hyperactivity Disorder (ADHD). Noteworthily, growing numbers of young people using prescribed MPH improperly for pleasurable enhancement, take high risk of addiction. Thus, understanding the mechanism underlying high level of MPH action in the brain becomes an important goal nowadays. As a blocker of catecholamine transporters, its therapeutic effect is explained as being due to proper modulation of D1 and α2A receptor. Here we showed that higher dose of MPH facilitates NMDA-receptor mediated synaptic transmission via a catecholamine-independent mechanism, in layer V∼VI pyramidal cells of the rat medial prefrontal cortex (PFC). To indicate its postsynaptic action, we next found that MPH facilitates NMDA-induced current and such facilitation could be blocked by σ1 but not D1/5 and α2 receptor antagonists. And this MPH eliciting enhancement of NMDA-receptor activity involves PLC, PKC and IP3 receptor mediated intracellular Ca2+ increase, but does not require PKA and extracellular Ca2+ influx. Our additional pharmacological studies confirmed that higher dose of MPH increases locomotor activity via interacting with σ1 receptor. Together, the present study demonstrates for the first time that MPH facilitates NMDA-receptor mediated synaptic transmission via σ1 receptor, and such facilitation requires PLC/IP3/PKC signaling pathway. This novel mechanism possibly explains the underlying mechanism for MPH induced addictive potential and other psychiatric side effects. PMID:23284812

Characterization of N-methyl-D-aspartate-evoked taurine release in the developing and adult mouse hippocampus.

PubMed

Saransaari, P; Oja, S S

2003-01-01

Taurine is an inhibitory amino acid acting as an osmoregulator and neuroromodulator in the brain, with neuroprotective properties. The ionotropic glutamate receptor agonist N-methyl-D-aspartate (NMDA) greatly potentiates taurine release from brain preparations in both normal and ischemic conditions, the effect being particularly marked in the developing hippocampus. We now characterized the regulation of NMDA-stimulated taurine release from hippocampal slices from adult (3-month-old) and developing (7-day-old) mouse using a superfusion system. The NMDA-stimulated taurine release was receptor-mediated in both adult and developing mouse hippocampus. In adults, only NO-generating compounds, sodium nitroprusside, S-nitroso-N-acetylpenicillamine and hydroxylamine reduced the release, as did also NO synthase inhibitors, 7-nitroindazole and nitroarginine, indicating that the release is mediated by the NO/cGMP pathway. On the other hand, the regulation of the NMDA-evoked taurine release proved to be somewhat complex in the immature hippocampus. It was not affected by the NOergic compounds, but enhanced by the protein kinase C activator 4 beta-phorbol 12-myristate 13-acetate and adenosine receptor A(1) agonists, N(6)-cyclohexyladenosine and R(-)N(6)-(2-phenylisopropyl)adenosine in a receptor-mediated manner. The activation of both ionotropic 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors and metabotropic glutamate group I receptors also enhanced the evoked release. The NMDA-receptor-stimulated taurine release could be a part of the neuroprotective properties of taurine, being important particularly under cell-damaging conditions in the developing hippocampus and hence preventing excitotoxicity.

The mGlu5 receptor antagonist MPEP activates specific stress-related brain regions and lacks neurotoxic effects of the NMDA receptor antagonist MK-801: significance for the use as anxiolytic/antidepressant drug.

PubMed

Inta, Dragos; Filipovic, Dragana; Lima-Ojeda, Juan M; Dormann, Christof; Pfeiffer, Natascha; Gasparini, Fabrizio; Gass, Peter

2012-04-01

Glutamatergic agents have been conceptualized as powerful, fast-acting alternatives to monoaminergic-based antidepressants. NMDA receptor antagonists such as ketamine or MK-801 are therapeutically effective, but their clinical use is hampered by psychotomimetic effects, accompanied by neurotoxicity in the retrosplenial and cingulate cortex. Antagonists of metabotropic mGlu5 receptors like MPEP elicit both robust antidepressant and anxiolytic effects; however, the underlying mechanisms are yet unknown. mGlu5 receptors closely interact with NMDA receptors, but whether MPEP induces neurotoxicity similar to NMDA receptor antagonists has not been elucidated. We show here using c-Fos brain mapping that MPEP administration results in a restricted activation of distinct stress-related brain areas, including the bed nucleus of stria terminalis (BNST), central nucleus of the amygdala, and paraventricular nucleus of the hypothalamus (PVNH), in a pattern similar to that induced by classical antidepressants and anxiolytics. Unlike the NMDA antagonist MK-801, MPEP does not injure the adult retrosplenial cortex, in which it fails to induce heat shock protein 70 (Hsp70). Moreover, MPEP does not elicit to the same extent as MK-801 apoptosis in cortical areas at perinatal stages, as revealed by caspase 3 expression. These data identify new cellular targets for the anxiolytic and antidepressant effect of MPEP, indicating also in addition that in contrast to MK-801, it lacks the cortical neurotoxicity associated with psychotomimetic side-effects. Copyright © 2012 Elsevier Ltd. All rights reserved.

Opposite modulation of brain stimulation reward by NMDA and AMPA receptors in the ventral tegmental area

PubMed Central

Ducrot, Charles; Fortier, Emmanuel; Bouchard, Claude; Rompré, Pierre-Paul

2013-01-01

Previous studies have shown that blockade of ventral tegmental area (VTA) glutamate N-Methyl-D-Aspartate (NMDA) receptors induces reward, stimulates forward locomotion and enhances brain stimulation reward. Glutamate induces two types of excitatory response on VTA neurons, a fast and short lasting depolarization mediated by α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors and a longer lasting depolarization mediated by NMDA receptors. A role for the two glutamate receptors in modulation of VTA neuronal activity is evidenced by the functional change in AMPA and NMDA synaptic responses that result from repeated exposure to reward. Since both receptors contribute to the action of glutamate on VTA neuronal activity, we studied the effects of VTA AMPA and NMDA receptor blockade on reward induced by electrical brain stimulation. Experiments were performed on rats trained to self-administer electrical pulses in the medial posterior mesencephalon. Reward thresholds were measured with the curve-shift paradigm before and for 2 h after bilateral VTA microinjections of the AMPA antagonist, NBQX (2,3,-Dioxo-6-nitro-1,2,3,4-tetrahydrobenzo(f)quinoxaline-7-sulfonamide, 0, 80, and 800 pmol/0.5 μl/side) and of a single dose (0.825 nmol/0.5 μl/side) of the NMDA antagonist, PPPA (2R,4S)-4-(3-Phosphonopropyl)-2-piperidinecarboxylic acid). NBQX produced a dose-dependent increase in reward threshold with no significant change in maximum rate of responding. Whereas PPPA injected at the same VTA sites produced a significant time dependent decrease in reward threshold and increase in maximum rate of responding. We found a negative correlation between the magnitude of the attenuation effect of NBQX and the enhancement effect of PPPA; moreover, NBQX and PPPA were most effective when injected, respectively, into the anterior and posterior VTA. These results suggest that glutamate acts on different receptor sub-types, most likely located on different VTA neurons, to modulate reward. PMID:24106463

Opposite modulation of brain stimulation reward by NMDA and AMPA receptors in the ventral tegmental area.

PubMed

Ducrot, Charles; Fortier, Emmanuel; Bouchard, Claude; Rompré, Pierre-Paul

2013-01-01

Previous studies have shown that blockade of ventral tegmental area (VTA) glutamate N-Methyl-D-Aspartate (NMDA) receptors induces reward, stimulates forward locomotion and enhances brain stimulation reward. Glutamate induces two types of excitatory response on VTA neurons, a fast and short lasting depolarization mediated by α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors and a longer lasting depolarization mediated by NMDA receptors. A role for the two glutamate receptors in modulation of VTA neuronal activity is evidenced by the functional change in AMPA and NMDA synaptic responses that result from repeated exposure to reward. Since both receptors contribute to the action of glutamate on VTA neuronal activity, we studied the effects of VTA AMPA and NMDA receptor blockade on reward induced by electrical brain stimulation. Experiments were performed on rats trained to self-administer electrical pulses in the medial posterior mesencephalon. Reward thresholds were measured with the curve-shift paradigm before and for 2 h after bilateral VTA microinjections of the AMPA antagonist, NBQX (2,3,-Dioxo-6-nitro-1,2,3,4-tetrahydrobenzo(f)quinoxaline-7-sulfonamide, 0, 80, and 800 pmol/0.5 μl/side) and of a single dose (0.825 nmol/0.5 μl/side) of the NMDA antagonist, PPPA (2R,4S)-4-(3-Phosphonopropyl)-2-piperidinecarboxylic acid). NBQX produced a dose-dependent increase in reward threshold with no significant change in maximum rate of responding. Whereas PPPA injected at the same VTA sites produced a significant time dependent decrease in reward threshold and increase in maximum rate of responding. We found a negative correlation between the magnitude of the attenuation effect of NBQX and the enhancement effect of PPPA; moreover, NBQX and PPPA were most effective when injected, respectively, into the anterior and posterior VTA. These results suggest that glutamate acts on different receptor sub-types, most likely located on different VTA neurons, to modulate reward.

Antidepressant effect of pramipexole in mice forced swimming test: A cross talk between dopamine receptor and NMDA/nitric oxide/cGMP pathway.

PubMed

Ostadhadi, Sattar; Imran Khan, Muhammad; Norouzi-Javidan, Abbas; Dehpour, Ahmad-Reza

2016-07-01

Pramipexole is a dopamine D2 receptor agonist indicated for treating Parkinson disorder. This study was aimed to investigate the effect of pramipexole in forced swimming test (FST) in mice and the possible involvement of activation of D2 receptors and inhibition of N-methyl-d-aspartate (NMDA) receptors and nitric oxide-cyclic guanosine monophosphate (NO-cGMP) on this effect. Intraperitoneal administration of pramipexole (1-3mg/kg) reduced the immobility time in the FST similar to fluoxetine (20mg/kg, i.p.). This effect of pramipexole (1mg/kg, i.p.) was ceased when mice were pretreated with haloperidol (0.15mg/kg, i.p,) and sulpiride (5mg/kg, i.p) as D2 receptor antagonists, NMDA (75mg/kg,i.p.), l-arginine (750mg/kg, i.p., a substrate for nitric oxide synthase) or sildenafil (5mg/kg, i.p., a phosphodiesterase 5 inhibitor). The administration of MK-801 (0.05mg/kg, i.p., a NMDA receptor antagonist) l-NG-Nitro arginine methyl ester (l-NAME, 10mg/kg, i.p., a non-specific nitric oxide synthase (NOS) inhibitor), 7-nitroindazole (30mg/kg, i.p., a neuronal NOS inhibitor) and methylene blue (10mg/kg, i.p.), an inhibitor of both NOS and soluble guanylyl cyclase (sGC) in combination with the sub-effective dose of pramipexole (0.3mg/kg, i.p.) reduced the immobility. Altogether, our data suggest that the antidepressant-like effect of pramipexole is dependent on the activation of D2 receptor and inhibition of either NMDA receptors and/or NO-cGMP synthesis. These results contribute to the understanding of the mechanisms underlying the antidepressant-like effect of pramipexole and reinforce the role of D2 receptors, NMDA receptors and l-arginine-NO-GMP pathway in the antidepressant mechanism of this agent. Copyright © 2016. Published by Elsevier Masson SAS.

Synthesis and characterization of a series of diarylguanidines that are noncompetitive N-methyl-D-aspartate receptor antagonists with neuroprotective properties

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

Keana, J.F.W.; McBurney, R.N.; Scherz, M.W.

1989-07-01

Four diarylguanidine derivatives were synthesized. These compounds were found to displace, at submicromolar concentrations, {sup 3}H-labeled 1-(1-(2-thienyl)cyclohexyl)piperidine and (+)-({sup 3}H)MK-801 from phencyclidine receptors in brain membrane preparations. In electrophysiological experiments the diarylguanidines blocked N-methyl-D-aspartate (NMDA)-activated ion channels. These dairylguanidines also protected rat hippocampal neurons in vitro from glutamate-induced cell death. The results show that some diarylguanidines are noncompetitive antagonists of NMDA receptor-mediated responses and have the neuroprotective property that is commonly associated with blockers of the NMDA receptor-gated cation channel. Diarylguanidines are structurally unrelated to known blockers of NMDA channels and, therefore, represent a new compound series for the developmentmore » of neuroprotective agents with therapeutic value in patients suffering from stroke, from brain or spinal cord trauma, from hypoglycemia, and possibly from brain ischemia due to heart attack.« less

[Combined blockade of AMPA- and NMDA-receptors has maximum effect to eliminate development of pentylenetetrazole-induced kindling in rats].

PubMed

Serdiuk, S E; Gmiro, V E; Veselkina, O S

2013-05-01

Peroral chronic administration the standard antiepileptic drug sodium valproate in a dose of 200 mg/kg eliminates development of generalized clonic-tonic pentylenetetrazol kindling seizures in 100% of rats, but only in 57% of rats this treatment prevents clonic kindling seizures. In the specified dose sodium valproate decreases in 1.7 times average severity of pentylenetetrazol kindling seizures compare with control. IEM-2121, causing combined blockade of NMDA- and AMPA-glutamate receptors, as well as IEM-1676, which also blocks AMPA-, NMDA- and N-cholinoreceptors, both after peroral chronic administration in a doses 10 mg/kg and 20 mg/kg accordingly, possess higher, than sodium valproate, anticonvulsant activity because reduce average severity of pentylenetetrazol kindling seizures in 2.4-2.7 times in comparison with control and prevents clonic kindling seizures in 87% of rats. Combined blockade of AMPA- and NMDA-receptors and perhars N-cholinoreceptors has maximum effect to eliminate epileptogenesis both clonic, and clonic-tonic pentylenetetrazol kindling seizures.

Protective effect of magnesium acetyltaurate against NMDA-induced retinal damage involves restoration of minerals and trace elements homeostasis.

PubMed

Jafri, Azliana Jusnida Ahmad; Arfuzir, Natasha Najwa Nor; Lambuk, Lidawani; Iezhitsa, Igor; Agarwal, Renu; Agarwal, Puneet; Razali, Norhafiza; Krasilnikova, Anna; Kharitonova, Maria; Demidov, Vasily; Serebryansky, Evgeny; Skalny, Anatoly; Spasov, Alexander; Yusof, Ahmad Pauzi Md; Ismail, Nafeeza Mohd

2017-01-01

Glutamate-mediated excitotoxicity involving N-methyl-d-aspartate (NMDA) receptors has been recognized as a final common outcome in pathological conditions involving death of retinal ganglion cells (RGCs). Overstimulation of NMDA receptors results in influx of calcium (Ca) and sodium (Na) ions and efflux of potassium (K). NMDA receptors are blocked by magnesium (Mg). Such changes due to NMDA overstimulation are also associated with not only the altered levels of minerals but also that of trace elements and redox status. Both the decreased and elevated levels of trace elements such as iron (Fe), zinc (Zn), copper (Cu) affect NMDA receptor excitability and redox status. Manganese (Mn), and selenium (Se) are also part of antioxidant defense mechanisms in retina. Additionally endogenous substances such as taurine also affect NMDA receptor activity and retinal redox status. Therefore, the aim of this study was to evaluate the effect of Mg acetyltaurate (MgAT) on the retinal mineral and trace element concentration, oxidative stress, retinal morphology and retinal cell apoptosis in rats after-NMDA exposure. One group of Sprague Dawley rats received intravitreal injection of vehicle while 4 other groups similarly received NMDA (160nmolL -1 ). Among the NMDA injected groups, 3 groups also received MgAT (320nmolL -1 ) as pre-treatment, co-treatment or post-treatment. Seven days after intravitreal injection, rats were sacrificed, eyes were enucleated and retinae were isolated for estimation of mineral (Ca, Na, K, Mg) and trace element (Mn, Cu, Fe, Se, Zn) concentration using Inductively Coupled Plasma (DRC ICP-MS) techniques (NexION 300D), retinal oxidative stress using Elisa, retinal morphology using H&E staining and retinal cell apoptosis using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL). Intravitreal NMDA injection resulted in increased concentration of Ca (4.6 times, p<0.0001), Mg (1.5 times, p<0.01), Na (3 times, p<0.0001) and K (2.3 times, p<0.0001) compared to vehicle injected group. This was accompanied with significant increase of Ca/Mg and Na/K ratios, 3 and 1.27 times respectively, compared to control group. The trace elements such as Cu, Fe and Zn also showed a significant increase amounting to 3.3 (p<0.001), 2.3 (p<0.0001) and 3 (p<0.0001) times respectively compared to control group. Se was increased by 60% (p<0.005). Pre-treatment with MgAT abolished effect of NMDA on minerals and trace elements more effectively than co- and post-treatment. Similar observations were made for retinal oxidative stress, retinal morphology and retinal cell apoptosis. In conclusion, current study demonstrated the protective effect of MgAT against NMDA-induced oxidative stress and retinal cell apoptosis. This effect of MgAT was associated with restoration of retinal concentrations of minerals and trace elements. Further studies are warranted to explore the precise molecular targets of MgAT. Nevertheless, MgAT seems a potential candidate in the management of diseases involving NMDA-induced excitotoxicity. Copyright © 2016 Elsevier GmbH. All rights reserved.

Impaired long-term memory and NR2A-type NMDA receptor-dependent synaptic plasticity in mice lacking c-Fos in the CNS.

PubMed

Fleischmann, Alexander; Hvalby, Oivind; Jensen, Vidar; Strekalova, Tatyana; Zacher, Christiane; Layer, Liliana E; Kvello, Ane; Reschke, Markus; Spanagel, Rainer; Sprengel, Rolf; Wagner, Erwin F; Gass, Peter

2003-10-08

The immediate early gene c-fos is part of the activator protein-1 transcription factor and has been postulated to participate in the molecular mechanisms of learning and memory. To test this hypothesis in vivo, we generated mice with a nervous system-specific c-fos knock-out using the Cre-loxP system. Adult mice lacking c-Fos in the CNS (c-fosDeltaCNS) showed normal general and emotional behavior but were specifically impaired in hippocampus-dependent spatial and associative learning tasks. These learning deficits correlated with a reduction of long-term potentiation (LTP) in hippocampal CA3-CA1 synapses. The magnitude of LTP was restored by a repeated tetanization procedure, suggesting impaired LTP induction in c-fosDeltaCNS mice. This rescue was blocked by a selective inhibitor of NR2B-type NMDA receptors. This blockade was compensated in wild-type mice by NR2A-type NMDA receptor-activated signaling pathways, thus indicating that these pathways are compromised in c-fosDeltaCNS mice. In summary, our data suggest a role for c-Fos in hippocampus-dependent learning and memory as well as in NMDA receptor-dependent LTP formation.

Potentiation of GluN2C/D NMDA receptor subtypes in the amygdala facilitates the retention of fear and extinction learning in mice.

PubMed

Ogden, Kevin K; Khatri, Alpa; Traynelis, Stephen F; Heldt, Scott A

2014-02-01

NMDA receptors are glutamate receptor ion channels that contribute to synaptic plasticity and are important for many forms of learning and memory. In the amygdala, NMDA receptors are critical for the acquisition, retention, and extinction of classically conditioned fear responses. Although the GluN2B subunit has been implicated in both the acquisition and extinction of conditioned fear, GluN2C-knockout mice show reduced conditioned fear responses. Moreover, D-cycloserine (DCS), which facilitates fear extinction, selectively enhances the activity of GluN2C-containing NMDA receptors. To further define the contribution of GluN2C receptors to fear learning, we infused the GluN2C/GluN2D-selective potentiator CIQ bilaterally into the basolateral amygdala (3, 10, or 30 μg/side) following either fear conditioning or fear extinction training. CIQ both increased the expression of conditioned fear 24 h later and enhanced the extinction of the previously conditioned fear response. These results support a critical role for GluN2C receptors in the amygdala in the consolidation of learned fear responses and suggest that increased activity of GluN2C receptors may underlie the therapeutic actions of DCS.

Protein kinase and phosphatase modulation of quail brain GABA(A) and non-NMDA receptors co-expressed in Xenopus oocytes.

PubMed

Moon, C; Fraser, S P; Djamgoz, M B

2000-02-01

The GABA(A) receptor and the non-NMDA subtype of the ionotropic glutamate receptor were co-expressed in Xenopus oocytes by injection of quail brain mRNA. The oocytes were treated with various protein kinase (PK) and protein phosphatase (PP) activators and inhibitors and the effects on receptor functioning were monitored. Two phorbol esters, 4-beta-phorbol 12-myristate-13-acetate (PMA) and 4-beta-phorbol 12,13-dibutyrate (PDBu); the cGMP-dependent PK activators sodium nitroprusside (SNP) and S-nitrosoglutathione (SNOG); and the PP inhibitor okadaic acid (OA) reduced the amplitude of the GABA-induced currents, whilst the PK inhibitor staurosporine potentiated it. In addition, PMA, PDBu, SNP, and OA reduced the desensitization of the GABA-induced response. Identical treatments generally had similar but less pronounced effects on responses generated by kainate (KA) but the desensitization characteristic of the non-NMDA receptor was not affected. None of the treatments had any effect on the reversal potentials of the induced currents. Immunoblots revealed that the oocytes express endogenous PKG and guanylate cyclase. The results are discussed in terms of the molecular structures of GABA(A) and non-NMDA receptors and the potential functional consequences of phosphorylation/dephosphorylation.

Blockade of NMDA receptors prevents analgesic tolerance to repeated transcutaneous electrical nerve stimulation (TENS) in rats

PubMed Central

Hingne, Priyanka M.; Sluka, Kathleen A.

2008-01-01

Repeated daily application transcutaneous electrical nerve stimulation (TENS) results in tolerance, at spinal opioid receptors, to the anti-hyperalgesia produced by TENS. Since N-Methyl-D-Aspartate (NMDA) receptor antagonists prevent analgesic tolerance to opioid agonists we hypothesized that blockade of NMDA receptors will prevent tolerance to TENS. In rats with knee joint inflammation, TENS was applied for 20 minute daily at high frequency (100 Hz), low frequency (4 Hz), or sham TENS. Rats were treated with the NMDA antagonist MK-801 (0.01 mg/kg-0.1 mg/kg) or vehicle daily before TENS. Paw withdrawal thresholds were tested before and after inflammation, and before and after TENS treatment for 4 days. On day 1 TENS reversed the decreased mechanical withdrawal threshold induced by joint inflammation. On day 4 TENS had no effect on the decreased withdrawal threshold in the group treated with vehicle demonstrating development of tolerance. However, in the group treated with 0.1 mg/kg MK-801, TENS significantly reversed the mechanical withdrawal thresholds on day 4 demonstrating that tolerance did not develop. Vehicle treated animals developed cross-tolerance at spinal opioid receptors. Treatment with MK-801 reversed this cross-tolerance at spinal opioid receptors. In summary, blockade of NMDA receptors prevents analgesic tolerance to daily TENS by preventing tolerance at spinal opioid receptors. Perspective Tolerance observed to the clinical treatment of TENS could be prevented by administration of pharmaceutical agents with NMDA receptors activity such as ketamine or dextromethorphan. PMID:18061543

Actions of Bupivacaine, a Widely Used Local Anesthetic, on NMDA Receptor Responses

PubMed Central

Paganelli, Meaghan A.

2015-01-01

NMDA receptors mediate excitatory neurotransmission in brain and spinal cord and play a pivotal role in the neurological disease state of chronic pain, which is caused by central sensitization. Bupivacaine is the indicated local anesthetic in caudal, epidural, and spinal anesthesia and is widely used clinically to manage acute and chronic pain. In addition to blocking Na+ channels, bupivacaine affects the activity of many other channels, including NMDA receptors. Importantly, bupivacaine inhibits NMDA receptor-mediated synaptic transmission in the dorsal horn of the spinal cord, an area critically involved in central sensitization. We used recombinant NMDA receptors expressed in HEK293 cells and found that increasing concentrations of bupivacaine decreased channel open probability in GluN2 subunit- and pH-independent manner by increasing the mean duration of closures and decreasing the mean duration of openings. Using kinetic modeling of one-channel currents, we attributed the observed current decrease to two main mechanisms: a voltage-dependent “foot-in-the-door” pore block and an allosteric gating effect. Further, the inhibition was state-independent because it occurred to the same degree whether the drug was applied before or after glutamate stimulation and was mediated by extracellular and intracellular inhibitory sites, via hydrophilic and hydrophobic pathways. These results predict that clinical doses of bupivacaine would decrease the peak and accelerate the decay of synaptic NMDA receptor currents during normal synaptic transmission. These quantitative predictions inform possible applications of bupivacaine as preventative and therapeutic approaches in chronic pain. PMID:25589775

NMDA receptor blockade and hippocampal neuronal loss impair fear conditioning and position habit reversal in C57Bl/6 mice.

PubMed

Bardgett, Mark E; Boeckman, Ryan; Krochmal, Daniel; Fernando, Hiran; Ahrens, Rebecca; Csernansky, John G

2003-04-15

The interpretation of learning and memory deficits in transgenic mice has largely involved theories of NMDA receptor and/or hippocampal function. However, there is little empirical data that describes what NMDA receptors or the hippocampus do in mice. This research assessed the effects of different doses of the NMDA receptor antagonist, MK-801, or different-sized hippocampal lesions on several behavioral parameters in adult male C57Bl/6 mice. In the first set of experiments, different doses of MK-801 (0.05-0.3mg/kg, s.c.) were assayed in fear conditioning, shock sensitivity, locomotion, anxiety, and position habit reversal tests. Contextual and cued fear conditioning, and position habit reversal were impaired in a dose-dependent manner. Locomotor activity was increased immediately after injection of the highest dose of MK-801. A second set of experiments determined the behavioral effects of a moderate and large excitotoxic hippocampal lesion. Both lesions impaired contextual conditioning, while the larger lesion interfered with cued conditioning. Reversal learning was significantly diminished by the large lesion, while the moderate lesion had a detrimental effect at a trend level (P<0.10). These results provide important reference data for studies involving genetic manipulations of NMDA receptor or hippocampal function in mice. Furthermore, they serve as a basis for a non-transgenic mouse model of the NMDA receptor or hippocampal dysfunction hypothesized to occur in human cognitive disorders.

Functional expression of ionotropic glutamate receptors in the rabbit retinal ganglion cells.

PubMed

Chen, Yin-Peng; Chiao, Chuan-Chin

2012-01-03

It has been known that retinal ganglion cells (RGCs) with distinct morphologies have different physiological properties. It was hypothesized that different functions of RGCs may in part result from various expressions of N-methyl-d-aspartate (NMDA), α-amino-3-hydroxyl-5-methyl-isoxazole-4-propinoic acid (AMPA), and kainic acid (KA) receptors on their dendrites. In the present study, we aimed to characterize the functional expression of AMPA and NMDA receptors of morphologically identified RGCs in the wholemount rabbit retina. The agmatine (AGB) activation assay was used to reveal functional expression of ionotropic glutamate receptors after the RGCs were targeted by injecting Neurobiotin. To examine the excitability of these glutamate receptors in an agonist specific manner, the lower concentrations of AMPA (2 μM) and NMDA (100 μM) were chosen to examine G7 (ON-OFF direction selective ganglion cells) and G11 (alpha ganglion cells) types of RGCs. We found that less than 40% of G7 type RGCs had salient AGB activation when incubated with 2 μM AMPA or 100 μM NMDA. The G11 type RGCs also showed similar activation frequencies, except that all of the OFF subtype examined had no AGB permeation under the same AMPA concentration. These results suggest that RGCs with large somata (G7 and G11 types) may express various heterogeneous functional ionotropic glutamate receptors, thus in part rendering their functional diversity. Copyright © 2011 Elsevier B.V. All rights reserved.

PSD-95 uncoupling from NMDA receptors by Tat- N-dimer ameliorates neuronal depolarization in cortical spreading depression.

PubMed

Kucharz, Krzysztof; Søndergaard Rasmussen, Ida; Bach, Anders; Strømgaard, Kristian; Lauritzen, Martin

2017-05-01

Cortical spreading depression is associated with activation of NMDA receptors, which interact with the postsynaptic density protein 95 (PSD-95) that binds to nitric oxide synthase (nNOS). Here, we tested whether inhibition of the nNOS/PSD-95/NMDA receptor complex formation by anti-ischemic compound, UCCB01-144 (Tat- N-dimer) ameliorates the persistent effects of cortical spreading depression on cortical function. Using in vivo two-photon microscopy in somatosensory cortex in mice, we show that fluorescently labelled Tat- N-dimer readily crosses blood-brain barrier and accumulates in nerve cells during the first hour after i.v. injection. The Tat- N-dimer suppressed stimulation-evoked synaptic activity by 2-20%, while cortical blood flow and cerebral oxygen metabolic (CMRO 2 ) responses were preserved. During cortical spreading depression, the Tat- N-dimer reduced the average amplitude of the negative shift in direct current potential by 33% (4.1 mV). Furthermore, the compound diminished the average depression of spontaneous electrocorticographic activity by 11% during first 40 min of post-cortical spreading depression recovery, but did not mitigate the suppressing effect of cortical spreading depression on cortical blood flow and CMRO 2 . We suggest that uncoupling of PSD-95 from NMDA receptors reduces overall neuronal excitability and the amplitude of the spreading depolarization wave. These findings may be of interest for understanding the neuroprotective effects of the nNOS/PSD-95 uncoupling in stroke.

Region-selective effects of neuroinflammation and antioxidant treatment on peripheral benzodiazepine receptors and NMDA receptors in the rat brain

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

Biegon, A.; Alvarado, M.; Budinger, T.F.

2001-12-10

Following induction of acute neuroinflammation by intracisternal injection of endotoxin (lipopolysaccharide) in rats, quantitative autoradiography was used to assess the regional level of microglial activation and glutamate (NMDA) receptor binding. The possible protective action of the antioxidant phenyl-tert-butyl nitrone in this model was tested by administering the drug in the drinking water for 6 days starting 24 hours after endotoxin injection. Animals were killed 7 days post-injection and consecutive cryostat brain sections labeled with [3H]PK11195 as a marker of activated microglia and [125I]iodoMK801 as a marker of the open-channel, activated state of NMDA receptors. Lipopolysaccharide increased [3H]PK11195 binding in themore » brain, with the largest increases (2-3 fold) in temporal and entorhinal cortex, hippocampus, and substantia innominata. A significant (>50 percent) decrease in [125I]iodoMK801 binding was found in the same brain regions. Phenyl-tert-butyl nitrone treatment resulted in a partial inhibition ({approx}25 percent decrease) of the lipopolysaccharide-induced increase in [3H]PK11195 binding but completely reversed the lipopolysaccharide-induced decrease in [125I]iodoMK80 binding in the entorhinal cortex, hippocampus, and substantia innominata. Loss of NMDA receptor function in cortical and hippocampal regions may contribute to the cognitive deficits observed in diseases with a neuroinflammatory component, such as meningitis or Alzheimer's disease.« less

(+)-3-( sup 123 I)Iodo-MK-801: Synthesis and characterization of binding to the N-methyl-D-aspartate receptor complex

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

Ransom, R.W.; Wai-si Eng; Burns, H.D.

1990-01-01

Synthetic methods have been established for preparing high specific activity (+)-3-({sup 123}I)Iodo-MK-801 in high radiochemical yield. The binding of the radiotracer to rat cortical membranes has been examine to assess its potential use as an in vivo imaging agent for the N-methyl-D-aspartate (NMDA) receptor-ion channel complex. Under the conditions of the assay, specific (+)-3-({sup 123}I)Iodo-MK-801 binding to membrane homogenates represented greater than 95% of the total binding. Several structurally distinct, noncompetitive NMDA receptor antagonists inhibited binding with potencies in accordance with their reported inhibitory activity at the receptor complex. The concentration of ({plus minus})-3-Iodo-MK-801 required to inhibit 50% of (+)-3-({supmore » 123}I)Iodo-MK-801 binding (IC{sub 50}) was 3.4 nM when using a low ionic strength assay buffer and 5.5 nM in a physiological buffer. In a thoroughly washed membrane preparation, (+)-3-({sup 123}I)Iodo-MK-801 binding was enhanced by L-glutamate and glycine at concentrations known to activate the NMDA receptor. The results indicate that (+)-3-({sup 123}I)Iodo-MK-801 specifically labels the NMDA receptor complex in rat brain membranes and the retention of high affinity under near physiological assay conditions suggests that it may be useful as a SPECT imaging agent for the receptor in vivo.« less

Synthesis and biological evaluation of cyclopropyl analogues of 2-amino-5-phosphonopentanoic acid

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

Dappen, M.S.; Pellicciari, R.; Natalini, B.

1991-01-01

A series of cyclopropyl analogues related to 2-amino-5-phosphonopentanoic acid (AP5) were synthesized and their biological activity was assessed as competitive antagonists for the N-methyl-D-aspartate (NMDA) receptor. In vitro receptor binding using (3H)-L-glutamate as the radioligand provided affinity data, while modulation of (3H)MK-801 binding was used as a functional assay. The analogues were also evaluated in (3H)kainate binding to assess selectivity over non-NMDA glutamate receptors. Of the compounds tested, 4,5-methano-AP5 analogue 26 was the most potent selective NMDA antagonist; however, potency was lower than that for (((+/-)-2-carboxypiperidin-4-yl)methyl)phosphonic acid (CGS 19755, 5).

[The role of glycine binding site in NMDA receptor--interactions between NMDA and D-serine in artificial anoxia/agycemia rat hippocampus].

PubMed

Kawasaki, Kazuyoshi; Ogawa, Seturou

2003-01-01

NMDA receptor contributes to cause neuronal death in anoxic condition. It is not known how a part of NMDA receptors, NMDA-binding site and/or glycine-binding site, influence neuronal damage in rats' hippocampus in vitro. Rats' hippocampus, labeled with norepinephrine (3H-NE), was incubated in artificial cerebrospinal fluid (aCSF) and we measured 3H-NE in superfusion solution and remaining tissue. Glucose was eliminated from aCSF and 95% N2 + 5% CO2 produced the anoxic state. The amount of 3H-NE release increased in anoxia with NMDA (NMDA-binding site agonist), while there was no influence on NMDA receptor in non-anoxic state even after D-serine (glycine-binding site agonist) has been administered. The 3H-NE was released more when D-serine (100 mu mM) and NMDA (100 mu mM) were administered together than when only D-serine (10 mu mM, 100 mu mM, 1000 mu mM) in anoxia or NMDA (10 mu mM, 100 mu mM, 1000 mu mM) in anoxia was administered. Glycine-binding site agonist alone does not act significantly but ion channels in NMDA receptor open more and become more effective when both glycine-binding site agonist and NMDA-binding site agonist exist, suggesting that there are interactions between NMDA-binding site and glycine-binding site in NMDA-receptor during anoxia.

Glutamate and GABA in lateral hypothalamic mechanisms controlling food intake.

PubMed

Stanley, B G; Urstadt, K R; Charles, J R; Kee, T

2011-07-25

By the 1990s a convergence of evidence had accumulated to suggest that neurons within the lateral hypothalamus (LH) play important roles in the stimulation of feeding behavior. However, there was little direct evidence demonstrating that neurotransmitters in the LH could, like electrical stimulation, elicit feeding in satiated animals. The present paper is a brief review in honor of Bartley Hoebel's scientific contributions, emphasizing the evidence from my lab that the excitatory neurotransmitter glutamate and the inhibitory neurotransmitter gamma aminobutyric acid (GABA) in the LH mediate feeding stimulation and feeding inhibition respectively. Specifically, we summarize evidence that LH injection of glutamate, or agonists of its N-methyl-D-aspartate (NMDA) and non-NMDA receptors, elicits feeding in satiated rats, that NMDA receptor antagonists block the eating elicited by NMDA and, more importantly, that NMDA blockade suppresses natural feeding and can reduce body weight. Conversely, GABA(A) agonists injected into the LH suppress feeding and can also reduce body weight, while GABA(A) receptor antagonists actually elicit eating when injected into the LH of satiated rats. It is suggested that natural feeding may reflect the moment-to-moment balance in the activity of glutamate and GABA within the LH. Copyright © 2011 Elsevier Inc. All rights reserved.

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.

An N-methyl-D-aspartate receptor-independent excitatory action of partial reduction of extracellular [Mg2+] in CA1-region of rat hippocampal slices.

PubMed

Hamon, B; Stanton, P K; Heinemann, U

1987-03-31

Partial reduction of [Mg2+]o from 2 to 1 mM markedly enhanced neuronal responses evoked by Schaffer collateral-commissural fiber stimulation in the CA1-region of rat hippocampal slices. The amplitude of extracellular population potentials recorded in the CA1-pyramidal cell layer and maximum dV/dt of extracellular population EPSP's recorded in the CA1-pyramidal apical dendritic layer were both increased. However, unlike findings from slices where Mg2+ was completely removed from the bathing medium, there was no spontaneous or evoked epileptiform activity, and the N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonovalerate (2-APV) did not antagonize the enhancement of evoked responses. These results indicate that, in addition to the participation of NMDA receptors in the epileptiform activity observed when Mg2+ is completely removed from the bathing medium, there is also an NMDA receptor-independent excitatory action of partial reduction of [Mg2+]o in hippocampal slices.

Multiple mechanisms of serotonin 5-HT2 receptor desensitization.

PubMed

Rahman, S; Neuman, R S

1993-07-20

Desensitization of serotonin 5-HT2 receptor-mediated enhancement of the N-methyl-D-aspartate (NMDA) depolarization was studied in rat cortical neurons. Serotonin and (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) induced long term desensitization. Staurosporine, a nonspecific protein kinase C inhibitor, potentiated the serotonin and DOI facilitation, suggesting acute desensitization was operative. In the case of DOI, long term desensitization was prevented by staurosporine. Activators of protein kinase C abolished the serotonin facilitation, an action prevented by staurosporine. Concanavalin A potentiated the facilitation at 100 microM, but not 30 microM serotonin, suggesting these receptors undergo dose dependent internalization. Calmodulin antagonists prevent long term desensitization induced by serotonin. The depolarization induced by NMDA alone was not altered by staurosporine, protein kinase C activators, concanavalin A or calmodulin antagonists. Serotonin at 100 microM, but not 30 microM, induced heterologous desensitization of phenylephrine and carbachol induced facilitation of the NMDA depolarization. We conclude that serotonin 5-HT2 receptors both induce and undergo several forms of desensitization.

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.

Effect of thiopental sodium on N-methyl-D-aspartate-gated currents.

PubMed

Liu, Hongliang; Dai, Tijun; Yao, Shanglong

2006-05-01

N-methyl-D-aspartate (NMDA) receptors in the prefrontal cortex (PFC) are closely related with the excitability of pyramidal neurons and PFC function. As the effect of thiopental sodium on the central nervous system may partly result from the inhibition of PFC NMDA receptors, we investigated the effect of thiopental sodium with different concentrations on NMDA-gated currents in acutely dissociated rat PFC pyramidal neurons. We sought to determine whether thiopental sodium inhibits NMDA receptor function. Three to four week old male Sprague-Dawley rats were sacrificed and the PFC was dissected. Pyramidal neurons from the PFC were prepared and standard whole-cell patch clamp recordings were performed. Escalating concentrations from 3-1000 microM NMDA were applied 100 microm from the pyramidal cells, and the concentration in the effect compartment related to 50% effect (EC50) of NMDA was determined for the ensuing experiments. One hundred microM NMDA alone (control) or NMDA with different concentrations (10-1000 microM) of thiopental sodium were applied. After the inhibitory concentration, in 50% of NMDA effect (IC50) of thiopental sodium was established this IC50 and NMDA 3-1000 microM were applied 100 microm from the pyramidal cells. The EC50 value of NMDA under the effect of IC50 thiopental sodium was determined. N-methyl-D-aspartate induced inward currents in a concentration-dependent manner, which were completely antagonized by 50 microM AP5. The maximal amplitude of NMDA-induced current was 1.15 +/- 0.27 nA. The EC50 of NMDA was 53.6 +/- 12.4 microM. The NMDA (100 microM)-gated current was inhibited by thiopental sodium in a concentration-dependent manner, and the IC50 of thiopental sodium was 33.6 +/- 6.1 microM. Under the effect of 33.6 microM thiopental sodium, the maximal amplitude of NMDA-induced current was 0.87 +/- 0.17 nA. The concentration-response curve of NMDA was shifted rightwards. The EC50 of NMDA was 128 +/- 15 microM, which was greater than that of NMDA without thiopental sodium (P < 0.01). Thiopental sodium decreases NMDA-gated currents in acutely dissociated rat prefrontal cortical pyramidal neurons in a concentration-dependent manner.

Blockage of N-methyl-D-aspartate receptors decreases testosterone levels and enhances postnatal neuronal apoptosis in the preoptic area of male rats.

PubMed

Hsu, C; Hsieh, Y L; Yang, R C; Hsu, H K

2000-05-01

Sexual dimorphism has been found in the preoptic area of the hypothalamus (POA), a major site of glutamate actions via N-methyl-D-aspartate (NMDA) receptors. The sexually dimorphic nucleus of the preoptic area (SDN-POA) of male rats exhibits about seven-fold greater nuclear volume than that of females. A naturally occurring neonatal neuronal apoptosis, that can be prevented by testosterone, may contribute to this sexual difference in SDN-POA nuclear volume. Since activation of NMDA receptors in the POA induces GnRH secretion, it may be involved in both elevation of serum testosterone and prevention of neuronal death in the SDN-POA. In the present study, protein expression of NMDA receptors in the POA of male and female fetuses was quantified on the day preceding the fetal testosterone peak (embryonic day 16; ED 16). Rats were then distributed in four groups: (1) untreated males, (2) untreated females, (3) males pretreated with MK-801 (a noncompetitive NMDA receptor antagonist), and (4) females pretreated with MK-801. Serum levels of testosterone were estimated on the afternoon of ED 18. Expression of Bcl-2 and Bax, as well as neuronal apoptosis in SDN-POA, were observed on postnatal day 8. The results showed that (1) expression of NMDA receptors in the POA of male fetuses was higher than that of females on ED 16; (2) levels of testosterone were lower in MK-801 pretreated male fetuses than in intact males on ED 18; (3) expression of Bcl-2 in the POA of MK-801 pretreated male rats was significantly less than that of control males; (4) the apoptotic incidence in the SDN-POA of MK-801 pretreated male rats was significantly greater than in control males, while there was no significant difference in apoptotic incidence in the SDN-POA between MK-801 pretreated and intact females. These results suggest that the NMDA receptor is highly expressed in prenatal male fetuses, and that it might play an important role in the elevation of testosterone levels. Moreover, activation of NMDA receptors may protect SDN-POA neurons from naturally occurring neuronal death, by modulating testosterone and/or Bcl-2 expression. Copyright 2000 S. Karger AG, Basel

Rosiglitazone Suppresses In Vitro Seizures in Hippocampal Slice by Inhibiting Presynaptic Glutamate Release in a Model of Temporal Lobe Epilepsy.

PubMed

Wong, Shi-Bing; Cheng, Sin-Jhong; Hung, Wei-Chen; Lee, Wang-Tso; Min, Ming-Yuan

2015-01-01

Peroxisomal proliferator-activated receptor gamma (PPARγ) is a nuclear hormone receptor whose agonist, rosiglitazone has a neuroprotective effect to hippocampal neurons in pilocarpine-induced seizures. Hippocampal slice preparations treated in Mg2+ free medium can induce ictal and interictal-like epileptiform discharges, which is regarded as an in vitro model of N-methyl-D-aspartate (NMDA) receptor-mediated temporal lobe epilepsy (TLE). We applied rosiglitazone in hippocampal slices treated in Mg2+ free medium. The effects of rosiglitazone on hippocampal CA1-Schaffer collateral synaptic transmission were tested. We also examined the neuroprotective effect of rosiglitazone toward NMDA excitotoxicity on cultured hippocampal slices. Application of 10 μM rosiglitazone significantly suppressed amplitude and frequency of epileptiform discharges in CA1 neurons. Pretreatment with the PPARγ antagonist GW9662 did not block the effect of rosiglitazone on suppressing discharge frequency, but reverse the effect on suppressing discharge amplitude. Application of rosiglitazone suppressed synaptic transmission in the CA1-Schaffer collateral pathway. By miniature excitatory-potential synaptic current (mEPSC) analysis, rosiglitazone significantly suppressed presynaptic neurotransmitter release. This phenomenon can be reversed by pretreating PPARγ antagonist GW9662. Also, rosiglitazone protected cultured hippocampal slices from NMDA-induced excitotoxicity. The protective effect of 10 μM rosiglitazone was partially antagonized by concomitant high dose GW9662 treatment, indicating that this effect is partially mediated by PPARγ receptors. In conclusion, rosiglitazone suppressed NMDA receptor-mediated epileptiform discharges by inhibition of presynaptic neurotransmitter release. Rosiglitazone protected hippocampal slice from NMDA excitotoxicity partially by PPARγ activation. We suggest that rosiglitazone could be a potential agent to treat patients with TLE.

Chronic nicotine treatment differentially modifies acute nicotine and alcohol actions on GABA(A) and glutamate receptors in hippocampal brain slices.

PubMed

Proctor, William R; Dobelis, Peter; Moritz, Anna T; Wu, Peter H

2011-03-01

Tobacco and alcohol are often co-abused producing interactive effects in the brain. Although nicotine enhances memory while ethanol impairs it, variable cognitive changes have been reported from concomitant use. This study was designed to determine how nicotine and alcohol interact at synaptic sites to modulate neuronal processes. Acute effects of nicotine, ethanol, and both drugs on synaptic excitatory glutamatergic and inhibitory GABAergic transmission were measured using whole-cell recording in hippocampal CA1 pyramidal neurons from brain slices of mice on control or nicotine-containing diets. Acute nicotine (50 nM) enhanced both GABAergic and glutamatergic synaptic transmission; potentiated GABA(A) receptor currents via activation of α7* and α4β2* nAChRs, and increased N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor currents through α7* receptors. While ethanol (80 mM) also increased GABA(A) currents, it inhibited NMDA currents. Although ethanol had no effect on AMPA currents, it blocked nicotine-induced increases in NMDA and AMPA currents. Following chronic nicotine treatment, acute nicotine or ethanol did not affect NMDA currents, while the effects of GABAergic responses were not altered. Acute ethanol ingestion selectively attenuated nicotine enhancement of excitatory glutamatergic NMDA and AMPA receptor function, suggesting an overall reduction in excitatory output from the hippocampus. It also indicated that ethanol could decrease the beneficial effects of nicotine on memory performance. In addition, chronic nicotine treatment produced tolerance to the effects of nicotine and cross-tolerance to the effects of ethanol on glutamatergic activity, leading to a potential increase in the use of these drugs. British Journal of Pharmacology © 2011 The British Pharmacological Society. No claim to original US government works.

Coping with dehydration: sympathetic activation and regulation of glutamatergic transmission in the hypothalamic PVN

PubMed Central

Bardgett, Megan E.; Chen, Qing-Hui; Guo, Qing; Calderon, Alfredo S.; Andrade, Mary Ann

2014-01-01

Autonomic and endocrine profiles of chronic hypertension and heart failure resemble those of acute dehydration. Importantly, all of these conditions are associated with exaggerated sympathetic nerve activity (SNA) driven by glutamatergic activation of the hypothalamic paraventricular nucleus (PVN). Here, studies sought to gain insight into mechanisms of disease by determining the role of PVN ionotropic glutamate receptors in supporting SNA and mean arterial pressure (MAP) during dehydration and by elucidating mechanisms regulating receptor activity. Blockade of PVN N-methyl-d-aspartate (NMDA) receptors reduced (P < 0.01) renal SNA and MAP in urethane-chloralose-anesthetized dehydrated (DH) (48 h water deprivation) rats, but had no effect in euhydrated (EH) controls. Blockade of PVN α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors had no effect in either group. NMDA in PVN caused dose-dependent increases of renal SNA and MAP in both groups, but the maximum agonist evoked response (Emax) of the renal SNA response was greater (P < 0.05) in DH rats. The latter was not explained by increased PVN expression of NMDA receptor NR1 subunit protein, increased PVN neuronal excitability, or decreased brain water content. Interestingly, PVN injection of the pan-specific excitatory amino acid transporter (EAAT) inhibitor dl-threo-β-benzyloxyaspartic acid produced smaller sympathoexcitatory and pressor responses in DH rats, which was associated with reduced glial expression of EAAT2 in PVN. Like chronic hypertension and heart failure, dehydration increases excitatory NMDA receptor tone in PVN. Reduced glial-mediated glutamate uptake was identified as a key contributing factor. Defective glutamate uptake in PVN could therefore be an important, but as yet unexplored, mechanism driving sympathetic hyperactivity in chronic cardiovascular diseases. PMID:24671240

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.

Protection of Retinal Ganglion Cells by Caspase Substrate-Binding Peptide IQACRG from N-Methyl-d-Aspartate Receptor-Mediated Excitotoxicity

PubMed Central

Seki, Masaaki; Soussou, Walid; Manabe, Shin-ichi

2010-01-01

Purpose. This study investigated whether the enzymatically inactive caspase mimetic IQACRG protects rat retinal ganglion cells (RGCs) from excitotoxic insults. Minimally invasive delivery of the peptide to the retina was explored, and the mechanisms of neuroprotection were elucidated. Methods. IQACRG was linked to penetratin (P-IQACRG) to facilitate cellular uptake. RGC labeling by biotinylated-P-IQACRG delivered via intravitreal or subconjunctival injection was demonstrated by avidin-biotin chemistry. The authors used histologic and electrophysiological measures to evaluate the neuroprotective potential of P-IQACRG against RGC death induced by N-methyl-d-aspartate (NMDA) in vitro and in vivo. In addition, they monitored activity of an enzyme that is downstream of caspase-1, matrix metalloproteinase-9 (MMP-9), and protein levels of the caspase-3/7 substrate, myocyte enhancer factor 2C (MEF2C), to determine the effectiveness of IQACRG in blocking excessive caspase activity. Results. IQACRG significantly reduced NMDA-induced RGC death in culture and in vivo. Ex vivo electrophysiological recording of the retina on multielectrode arrays demonstrated functional rescue of RGCs by IQACRG. The authors also found that delivery of IQACRG to the retina inhibited NMDA-triggered MMP-9 activity and prevented cleavage of MEF2C protein that would otherwise have been engendered by caspase activation preceding RGC death. Strikingly, subconjunctival injection of P-IQACRG was very effective in preventing NMDA-induced RGC death in vivo. Conclusions. These data demonstrate that IQACRG protects RGCs from excitotoxicity in vitro and in vivo. The positive results with subconjunctival administration of P-IQACRG suggest that in the future this treatment may be useful clinically in diseases such as glaucoma and retinal ischemia. PMID:19815732

Norrin mediates neuroprotective effects on retinal ganglion cells via activation of the Wnt/beta-catenin signaling pathway and the induction of neuroprotective growth factors in Muller cells.

PubMed

Seitz, Roswitha; Hackl, Simon; Seibuchner, Thomas; Tamm, Ernst R; Ohlmann, Andreas

2010-04-28

Norrin is a secreted protein that binds to frizzled 4 and controls development of capillaries in retina and inner ear. We provide evidence that Norrin has distinct neuroprotective properties that are independent from its effects on vascular development. The function of Norrin was investigated in a mouse model of excitotoxic retinal ganglion cell (RGC) damage after intravitreal injection of NMDA, and in cultured Müller glia or immortalized RGC-5 cells. Intravitreal injection of Norrin significantly increased the number of surviving RGC axons in the optic nerve and decreased apoptotic death of retinal neurons following NMDA-mediated damage. This effect could be blocked by adding dickkopf (DKK)-1, an inhibitor of the Wnt/beta-catenin signaling pathway. Treatment of eyes with combined Norrin/NMDA activated Wnt/beta-catenin signaling and increased the retinal expression of leukemia inhibitory factor and endothelin-2, as well as that of neurotrophic growth factors such as fibroblast growth factor-2, brain-derived neurotrophic factor, lens epithelium-derived growth factor, and ciliary neurotrophic factor. A similar activation of Wnt/beta-catenin signaling and an increased expression of neurotrophic factors was observed in cultured Müller cells after treatment with Norrin, effects that again could be blocked by adding DKK-1. In addition, conditioned cell culture medium of Norrin-treated Müller cells increased survival of differentiated RGC-5 cells. We conclude that Norrin has pronounced neuroprotective properties on retinal neurons with the distinct potential to decrease the damaging effects of NMDA-induced RGC loss. The effects of Norrin involve activation of Wnt/beta-catenin signaling and subsequent induction of neurotrophic growth factors in Müller cells.

Functional cardiovascular action of L-cysteine microinjected into pressor sites of the rostral ventrolateral medulla of the rat.

PubMed

Takemoto, Yumi

2014-04-01

The endogenous sulfur-containing amino acid L-cysteine injected into the cerebrospinal fluid space of the cisterna magna increases arterial blood pressure (ABP) and heart rate (HR) in the freely moving rat. The present study examined (1) cardiovascular responses to L-cysteine microinjected into the rostral ventrolateral medulla (RVLM), where a group of neurons regulate activities of cardiovascular sympathetic neurons and (2) involvement of ionotropic excitatory amino acid (iEAA) receptors in response. In the RVLM of urethane-anesthetized rats accessed ventrally and identified with pressor responses to L-glutamate (10 mM, 34 nl), microinjections of L-cysteine increased ABP and HR dose dependently (3-100 mM, 34 nl). The cardiovascular responses to L-cysteine (30 mM) were not attenuated by a prior injection of either antagonist alone, MK801 (20 mM, 68 nl) for the NMDA type of iEAA receptors, or CNQX (2 mM) for the non-NMDA type. However, inhibition of both NMDA and non-NMDA receptors with additional prior injection of either antagonist completely blocked those responses to L-cysteine. The results indicate that L-cysteine has functional cardiovascular action in the RVLM of the anesthetized rat, and the responses to L-cysteine involve both NMDA and non-NMDA receptors albeit in a mutually exclusive parallel fashion. The findings may suggest endogenous roles of L-cysteine indirectly via iEAA receptors in the neuronal network of the RVLM for cardiovascular regulation in physiological and pathological situations.

D-cycloserine in Schizophrenia: New Strategies for Improving Clinical Outcomes by Enhancing Plasticity

PubMed Central

Goff, Donald C.

2017-01-01

Background Dysregulation of N-methyl D-aspartate (NMDA) receptor signaling is strongly implicated in schizophrenia. Based on the ketamine model of NMDA receptor hypoactivity, therapeutic approaches designed to maintain a sustained increase in agonist activity at the glycine site of the NMDA receptor have produced promising, although inconsistent, efficacy for negative symptoms. Methods A review of the published literature on D-cycloserine (DCS) pharmacology in animal models and in clinical studies was performed. Findings relevant to DCS effects on memory and plasticity and their potential clinical application to schizophrenia were summarized. Results Studies in animals and clinical trials in patients with anxiety disorders have demonstrated that single or intermittent dosing with DCS enhances memory consolidation. Preliminary trials in patients with schizophrenia suggest that intermittent dosing with DCS may produce persistent improvement of negative symptoms and enhance learning when combined with cognitive behavioral therapy for delusions or with cognitive remediation. The pharmacology of DCS is complex, since it acts as a “super agonist” at NMDA receptors containing GluN2C subunits and, under certain conditions, it may act as an antagonist at NMDA receptors containing GluN2B subunits. Conclusions There are preliminary findings that support a role for D-cycloserine in schizophrenia as a strategy to enhance neuroplasticity and memory. However, additional studies with DCS are needed to confirm these findings. In addition, clinical trials with positive and negative allosteric modulators with greater specificity for NMDA receptor subtypes are needed to identify the optimal strategy for enhancing neuroplasticity in schizophrenia. PMID:26915421

NMDA and AMPA/kainate glutamatergic receptors in the prelimbic medial prefrontal cortex modulate the elaborated defensive behavior and innate fear-induced antinociception elicited by GABAA receptor blockade in the medial hypothalamus.

PubMed

de Freitas, Renato Leonardo; Salgado-Rohner, Carlos José; Biagioni, Audrey Francisco; Medeiros, Priscila; Hallak, Jaime Eduardo Cecílio; Crippa, José Alexandre S; Coimbra, Norberto Cysne

2014-06-01

The aim of the present study was to investigate the involvement of N-methyl-d-aspartate (NMDA) and amino-3-hydroxy-5-methyl-isoxazole-4-proprionate (AMPA)/kainate receptors of the prelimbic (PL) division of the medial prefrontal cortex (MPFC) on the panic attack-like reactions evoked by γ-aminobutyric acid-A receptor blockade in the medial hypothalamus (MH). Rats were pretreated with NaCl 0.9%, LY235959 (NMDA receptor antagonist), and NBQX (AMPA/kainate receptor antagonist) in the PL at 3 different concentrations. Ten minutes later, the MH was treated with bicuculline, and the defensive responses were recorded for 10 min. The antagonism of NMDA receptors in the PL decreased the frequency and duration of all defensive behaviors evoked by the stimulation of the MH and reduced the innate fear-induced antinociception. However, the pretreatment of the PL cortex with NBQX was able to decrease only part of defensive responses and innate fear-induced antinociception. The present findings suggest that the NMDA-glutamatergic system of the PL is critically involved in panic-like responses and innate fear-induced antinociception and those AMPA/kainate receptors are also recruited during the elaboration of fear-induced antinociception and in panic attack-related response. The activation of the glutamatergic neurotransmission of PL division of the MPFC during the elaboration of oriented behavioral reactions elicited by the chemical stimulation of the MH recruits mainly NMDA receptors in comparison with AMPA/kainate receptors.

Nedd4 is a Specific E3 Ubiquitin Ligase for the NMDA Receptor Subunit GluN2D

PubMed Central

Gautam, Vivek; Trinidad, Jonathan C.; Rimerman, Ronald A.; Costa, Blaise M.; Burlingame, Alma L.; Monaghan, Daniel T.

2013-01-01

NMDA receptors are a family of glutamate-gated ion channels that regulate various CNS functions such as synaptic plasticity and learning. However hypo-or hyper-activation of NMDA receptors is critically involved in many neurological and psychiatric conditions such as pain, stroke, epilepsy, neurodegeneration, schizophrenia, and depression. Thus, it is important to identify mechanisms (such as by targeted ubiquitination) that regulate the levels of individual subtypes of NMDA receptors. In this study, we used a series of tagged, carboxy terminal constructs of GluN2D to identify associating proteins from rat brain. Of seven different GluN2D C-terminal fragments used as bait, only the construct containing amino acids 983-1097 associated with an E3 ligase, Nedd4. A direct interaction between GluN2D and Nedd4 was confirmed both in vivo and in vitro. This association is mediated by an interaction between GluN2D's C-terminal PPXY motif and the 2nd and 3rd WW domains of Nedd4. Of the four GluN2 subunits, Nedd4 directly interacted with GluN2D and also weakly with GluN2A. Nedd4 coexpression with GluN2D enhances GluN2D ubiquitination and reduces GluN1/GluN2D NMDA receptor responses. These results identify Nedd4 as a novel binding partner for GluN2D and suggest a mechanism for the regulation of NMDA receptors that contains GluN2D subunit through ubiquitination-dependent downregulation. PMID:23639431

AVP and Glu systems interact to regulate levels of anxiety in BALB/cJ mice.

PubMed

An, Xiao-Lei; Tai, Fa-Dao

2014-07-01

Whilethe roles of glutamic acid (Glu), arginine vasopressin (AVP) and their respective receptors in anxiety have been thoroughly investigated, the effects of interactions among Glu, N-methyl-D-aspartic acid (NMDA) receptor, AVP and a-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor on anxiety are still unclear. In the present study, the agonist and antagonist of the NMDA receptor and AMPA receptor, as well as the antagonist of AVP V1 receptor (V1aR) were introduced into BALB/cJ mice by intracerebroventricular microinjection, and the anxiety-like behaviors of the mice were evaluated by open field and elevated plus-maze tests. Compared with C57BL/6 mice, BALB/cJ mice displayed higher levels of anxiety-like behavior. Significant anxiolytic effects were found in the NMDA receptor antagonist (MK-801) and the AMPA receptor or V1aR antagonist (SSRI49415), as well as combinations of AVP/MK-801 and SSRI49415/DNQX. These results indicated that anxiety-like behaviors expressed in BALB/CJ mice may be due to a coordination disorder among glutamate, NMDA receptor, AMPA receptor, AVP and V1aR, resulting in the up-regulation of the NMDA receptor and V1aR and down-regulation of the AMPA receptor. However, because the AMPA receptor can execute its anxiolytic function by suppressing AVP and V1aR, we cannot exclude the possibility of the NMDA receptor being activated by AVP acting on V1aR.

[Beta]-Adrenergic Receptor Activation Rescues Theta Frequency Stimulation-Induced LTP Deficits in Mice Expressing C-Terminally Truncated NMDA Receptor GluN2A Subunits

ERIC Educational Resources Information Center

Moody, Teena D.; Watabe, Ayako M.; Indersmitten, Tim; Komiyama, Noboru H.; Grant, Seth G. N.; O'Dell, Thomas J.

2011-01-01

Through protein interactions mediated by their cytoplasmic C termini the GluN2A and GluN2B subunits of NMDA receptors (NMDARs) have a key role in the formation of NMDAR signaling complexes at excitatory synapses. Although these signaling complexes are thought to have a crucial role in NMDAR-dependent forms of synaptic plasticity such as long-term…

[Anti-NMDA-receptor encephalitis: a new axis-III disorder in the differential diagnosis of childhood disintegrative disorder, early onset schizophrenia and late onset autism].

PubMed

Creten, C; van der Zwaan, S; Blankespoor, R J; Maatkamp, A; Klinkenberg, S; van Kranen-Mastenbroek, V H J M; Nicolai, J; Dhossche, D M; van Os, J; Schieveld, J N M

2012-01-01

Childhood disintegrative disorder (CDD), early onset schizophrenia (EOS), and late onset autism (LOA) often follow a similar course: initially, development is normal, then there is a sudden neuropsychiatric deterioration of social interaction and communication skills, which is combined with a decline in intelligence and reduction in daily activities. A 9-year-old boy was admitted to the paediatric ward with acute onset of secondary epileptic seizures. It was not long until the boy's symptoms resembled that of patients with cdd, eos and loa. Intensive tests led to the diagnosis of anti-NMDA-receptor encephalitis. Anti-NMDA-receptor encephalitis should be regarded as a possible organic cause underlying the syndromal presentation of CDD, EOS and LOA.

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.

A novel system applying the 2-deoxyglucose method to fish for characterization of environmental neurotoxins.

PubMed

Choich, J A; Sass, J B; Silbergeld, E K

2002-01-01

Methods of identifying and preventing ecotoxicity related to environmental stressors on wildlife species are underdeveloped. To detect sublethal effects, we have devised a neurochemical method of evaluating environmental neurotoxins by a measuring changes in regional neural activity in the central nervous system of fish. Our system is a unique adaptation of the 2-deoxyglucose (2-DG) method originally developed by L. Sokoloff in 1977, which is based on the direct relationship between glucose metabolism and neural functioning at the regional level. We applied these concepts to test the assumption that changes in neural activity as a result of chemical exposure would produce measurable effects on the amount of [(14)C]2-DG accumulated regionally in the brain of Tilapia nilatica. For purposes of this study, we utilized the excitotoxin N-methyl-D-aspartate (NMDA) to characterize the response of the central nervous system. Regional accumulation of [(14)C]2-DG was visualized by autoradiography and digital image processing. Observable increases in regional [(14) C] 2-DG uptake were evident in all NMDA-treated groups as compared to controls. Specific areas of increased [(14)C] 2-DG uptake included the telencephalon, optic tectum, and regions of the cerebellum, all areas in which high concentrations of NMDA-subtype glutamate receptors have been found in Tilapia monsanbica. These results are consistent with the known neural excitatory action of NMDA.

Modeling the effect of glutamate diffusion and uptake on NMDA and non-NMDA receptor saturation.

PubMed Central

Holmes, W R

1995-01-01

One- and two-dimensional models of glutamate diffusion, uptake, and binding in the synaptic cleft were developed to determine if the release of single vesicles of glutamate would saturate NMDA and non-NMDA receptors. Ranges of parameter values were used in the simulations to determine the conditions when saturation could occur. Single vesicles of glutamate did not saturate NMDA receptors unless diffusion was very slow and the number of glutamate molecules in a vesicle was large. However, the release of eight vesicles at 400 Hz caused NMDA receptor saturation for all parameter values tested. Glutamate uptake was found to reduce NMDA receptor saturation, but the effect was smaller than that of changes in the diffusion coefficient or in the number of glutamate molecules in a vesicle. Non-NMDA receptors were not saturated unless diffusion was very slow and the number of glutamate molecules in a vesicle was large. The release of eight vesicles at 400 Hz caused significant non-NMDA receptor desensitization. The results suggest that NMDA and non-NMDA receptors are not saturated by single vesicles of glutamate under usual conditions, and that tetanic input, of the type typically used to induce long-term potentiation, will increase calcium influx by increasing receptor binding as well as by reducing voltage-dependent block of NMDA receptors. Images FIGURE 1 PMID:8580317

NMDA receptor antagonism with novel indolyl, 2-(1,1-Dimethyl-1,3-dihydro-benzo[e]indol-2-ylidene)-malonaldehyde, reduces seizures duration in a rat model of epilepsy

PubMed Central

Rothan, Hussin A.; Amini, Elham; Faraj, Fadihl L.; Golpich, Mojtaba; Teoh, Teow Chong; Gholami, Khadijeh; Yusof, Rohana

2017-01-01

N-methyl-D-aspartate receptors (NMDAR) play a central role in epileptogensis and NMDAR antagonists have been shown to have antiepileptic effects in animals and humans. Despite significant progress in the development of antiepileptic therapies over the previous 3 decades, a need still exists for novel therapies. We screened an in-house library of small molecules targeting the NMDA receptor. A novel indolyl compound, 2-(1,1-Dimethyl-1,3-dihydro-benzo[e]indol-2-ylidene)-malonaldehyde, (DDBM) showed the best binding with the NMDA receptor and computational docking data showed that DDBM antagonised the binding sites of the NMDA receptor at lower docking energies compared to other molecules. Using a rat electroconvulsive shock (ECS) model of epilepsy we showed that DDBM decreased seizure duration and improved the histological outcomes. Our data show for the first time that indolyls like DDBM have robust anticonvulsive activity and have the potential to be developed as novel anticonvulsants. PMID:28358047

Two Coincidence Detectors for Spike Timing-Dependent Plasticity in Somatosensory Cortex

PubMed Central

Bender, Vanessa A.; Bender, Kevin J.; Brasier, Daniel J.; Feldman, Daniel E.

2011-01-01

Many cortical synapses exhibit spike timing-dependent plasticity (STDP) in which the precise timing of presynaptic and postsynaptic spikes induces synaptic strengthening [long-term potentiation (LTP)] or weakening [long-term depression (LTD)]. Standard models posit a single, postsynaptic, NMDA receptor-based coincidence detector for LTP and LTD components of STDP. We show instead that STDP at layer 4 to layer 2/3 synapses in somatosensory (S1) cortex involves separate calcium sources and coincidence detection mechanisms for LTP and LTD. LTP showed classical NMDA receptor dependence. LTD was independent of postsynaptic NMDA receptors and instead required group I metabotropic glutamate receptors and calcium from voltage-sensitive channels and IP3 receptor-gated stores. Downstream of postsynaptic calcium, LTD required retrograde endocannabinoid signaling, leading to presynaptic LTD expression, and also required activation of apparently presynaptic NMDA receptors. These LTP and LTD mechanisms detected firing coincidence on ~25 and ~125 ms time scales, respectively, and combined to implement the overall STDP rule. These findings indicate that STDP is not a unitary process and suggest that endocannabinoid-dependent LTD may be relevant to cortical map plasticity. PMID:16624937

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

Tao-Cheng, Jung-Hwa; Yang, Yijung; Bayer, K. Ulrich

Highlights: • NMDA-induces accumulation of Shank at the postsynaptic density. • Shank accumulation is preferential to the distal region of the postsynaptic density. • Shank accumulation is mediated by CaMKII. - Abstract: Shank is a specialized scaffold protein present in high abundance at the postsynaptic density (PSD). Using pre-embedding immunogold electron microscopy on cultured hippocampal neurons, we had previously demonstrated further accumulation of Shank at the PSD under excitatory conditions. Here, using the same experimental protocol, we demonstrate that a cell permeable CaMKII inhibitor, tatCN21, blocks NMDA-induced accumulation of Shank at the PSD. Furthermore we show that NMDA application changesmore » the distribution pattern of Shank at the PSD, promoting a 7–10 nm shift in the median distance of Shank labels away from the postsynaptic membrane. Inhibition of CaMKII with tatCN21 also blocks this shift in the distribution of Shank. Altogether these results imply that upon activation of NMDA receptors, CaMKII mediates accumulation of Shank, preferentially at the distal regions of the PSD complex extending toward the cytoplasm.« less

Behavioral analysis of the consequences of chronic blockade of NMDA-type glutamate receptors in the early postnatal period in rats.

PubMed

Latysheva, N V; Raevskii, K S

2003-02-01

Considering data on the possible glutamatergic nature of the pathogenesis of schizophrenia, we attempted to model cognitive derangements in animals by chronic blockade of NMDA glutamate receptors. Wistar rats received daily s.c. injections of the non-competitive NMDA glutamate receptor antagonist MK-801 (0.05 mg/kg) from days 7 to day 49 of postnatal life. One day after the antagonist injections given on days 27 and 28 of life, animals of the experimental group showed decreased levels of spontaneous movement and orientational-investigative activity as compared with controls, where there was no change in the elevated locomotor reaction produced in response to the direct action of MK-801. These animals showed decreases in the level of anxiety (on day 40 of life) and derangement in spatial learning with food reinforcement (days 50-54 of life). It is suggested that early neonatal blockade of NMDA glutamate receptors leads to the development in animals of disturbances to situational perception and assessment of incoming sensory information.

Brain purine metabolism and xanthine dehydrogenase/oxidase conversion in hyperammonemia are under control of NMDA receptors and nitric oxide.

PubMed

Kaminsky, Yury; Kosenko, Elena

2009-10-19

In hyperammonemia, a decrease in brain ATP can be a result of adenine nucleotide catabolism. Xanthine dehydrogenase (XD) and xanthine oxidase (XO) are the end steps in the purine catabolic pathway and directly involved in depletion of the adenylate pool in the cell. Besides, XD can easily be converted to XO to produce reactive oxygen species in the cell. In this study, the effects of acute ammonia intoxication in vivo on brain adenine nucleotide pool and xanthine and hypoxanthine, the end degradation products of adenine nucleotides, during the conversion of XD to XO were studied. Injection of rats with ammonium acetate was shown to lead to the dramatic decrease in the ATP level, adenine nucleotide pool size and adenylate energy charge and to the great increase in hypoxanthine and xanthine 11 min after the lethal dose indicating rapid degradation of adenylates. Conversion of XD to XO in hyperammonemic rat brain was evidenced by elevated XO/XD activity ratio. Injection of MK-801, a NMDA receptor blocker, prevented ammonia-induced catabolism of adenine nucleotides and conversion of XD to XO suggesting that in vivo these processes are mediated by activation of NMDA receptors. The in vitro dose-dependent effects of sodium nitroprusside, a NO donor, on XD and XO activities are indicative of the direct modification of the enzymes by nitric oxide. This is the first report evidencing the increase in brain xanthine and hypoxanthine levels and adenine nucleotide breakdown in acute ammonia intoxication and NMDA receptor-mediated prevention of these alterations.

Effects of the H3 Antagonist, Thioperamide, on Behavioral Alterations Induced by Systemic MK-801 Administration in Rats

PubMed Central

Bardgett, Mark E.; Points, Megan; Roflow, John; Blankenship, Meredith; Griffith, Molly S.

2009-01-01

Rationale Recent studies have raised the possibility that antagonists of H3 histamine receptors possess cognitive-enhancing and antipsychotic properties. However, little work has assessed these compounds in classic animal models of schizophrenia. Objectives The purpose of this study was to determine if a prototypical H3 antagonist, thioperamide, could alter behavioral deficits caused by the NMDA receptor antagonist, MK-801, in adult male rats. MK-801 was chosen for study since it produces a state of NMDA receptor hypofunction in rats that may be analogous to the one hypothesized to occur in schizophrenia. Methods The interaction between thioperamide and MK-801 was measured in three behavioral tests: locomotor activity, prepulse inhibition (PPI), and delayed spatial alternation. In each test, rats received a subcutaneous injection of saline or thioperamide (3.0 & 10 mg/kg) followed 20 minutes later by a subcutaneous injection of saline or MK-801 (0.05, 0.10, & 0.30 mg/kg). Results Locomotor activity was significantly elevated by MK-801 in a dose-dependent manner. Thioperamide pretreatment alone did not alter locomotor activity, however its impact on MK-801 was dose-dependent. Each thioperamide dose enhanced the effects of two lower doses of MK801 but reduced the effect of a higher MK-801 dose. Clear deficits in PPI and delayed spatial alternation were produced by MK-801 treatment, but neither impairment was significantly modified by thioperamide pretreatment. Conclusions H3 receptors modulate responses to NMDA antagonists in behaviorally-specific ways and dependent upon the level of NMDA receptor blockade. PMID:19466392

Insulin-Like Growth Factor-I Regulates LH Release by Modulation of Kisspeptin and NMDA-Mediated Neurotransmission in Young and Middle-Aged Female Rats

PubMed Central

Yao, Dachun; Shu, Jun; Sun, Yan; Etgen, Anne M.

2014-01-01

This study investigated potential mechanisms by which age and IGF-I receptor (IGF-Ir) signaling in the neuroendocrine hypothalamus affect estradiol-positive feedback effects on GnRH neuronal activation and on kisspeptin and N-methyl-D-aspartate (NMDA)-induced LH release and on the abundance of NMDA receptor subunits Nr1 and Nr2b and Kiss1r transcript and protein in the hypothalamus of young and middle-aged female rats. We infused vehicle, IGF-I, or JB-1, a selective antagonist of IGF-Ir, into the third ventricle of ovariectomized female rats primed with estradiol or vehicle and injected with vehicle, kisspeptin (3 or 30 nmol/kg), or NMDA (15 or 30 mg/kg). Regardless of dose, NMDA and kisspeptin resulted in significantly more LH release, GnRH/c-Fos colabeling, and c-Fos immunoreative cells in young than in middle-aged females. Estradiol priming significantly increased Kiss1r, Nr1, and Nr2b receptor transcript and protein abundance in young but not middle-aged female hypothalamus. JB-1 attenuated kisspeptin and NMDA-induced LH release, numbers of GnRH/c-Fos and c-Fos cells, and Kiss1r, Nr1, and Nr2b transcript and protein abundance in young females to levels observed in middle-aged females. IGF-I significantly enhanced NMDA and kisspeptin-induced LH release in middle-aged females without increasing numbers of GnRH/c-Fos or c-Fos immunoreactive cells. IGF-I infusion in middle-aged females also increased Kiss1r, Nr1, and Nr2b protein and transcript to levels that were equivalent to young estradiol-primed females. These findings indicate that age-related changes in estradiol-regulated responsiveness to excitatory input from glutamate and kisspeptin reflect reduced IGF-Ir signaling. PMID:24617524

Implication of NMDA type glutamate receptors in neural regeneration and neoformation of synapses after excitotoxic injury in the guinea pig cochlea.

PubMed

d'Aldin, C G; Ruel, J; Assié, R; Pujol, R; Puel, J L

1997-07-01

In the adult mammalian cochlea, the ability of nerve fibres to regenerate has been observed following disruption of the organ of Corti by various means, or transsection of the cochlear nerve in the internal auditory meatus. Based upon the implication of glutamate as a neurotransmitter at synapses between sensory hair cells and terminal dendrites of the auditory nerve in the mammalian cochlea, we have developed, in a previous study, an in vivo model of neural regeneration and formation of synapses after the destruction of the afferent nerve endings by local application of the glutamate agonist alpha-amino-3-hydroxy-5-methyl-isoxazol-propionic acid (AMPA). In situ hybridization experiments performed during the re-innervation process revealed an overexpression of mRNA coding for NR1 subunit of N-methyl-D-aspartate (NMDA) receptors in the spiral ganglion neurons, suggesting that these receptors are implicated in neural regenerative processes. The present study has been designed to study the functional implication of NMDA receptors in the regrowth and synaptic repair of auditory dendrites in the guinea pig cochlea, by blocking the NMDA receptors during the period of normal functional recovery. In a first set of experiments, we recorded compound action potential after acute perilymphatic perfusion of cumulative doses (0.03-10mM) of DL 2-amino-5-phosphonovalerate (D-AP5), a NMDA antagonist, to determine the efficiency of the drug. In a second set of experiments, the auditory dendrites were destroyed by local application of the glutamate agonist AMPA. The blockage of NMDA by the antagonist D-AP5 applied with an osmotic micropump delayed the functional recovery and the regrowth of auditory dendrites. The findings of our study support the hypothesis that, in addition to acting as a fast transmitter, glutamate has a neurotrophic role via the activation of NMDA receptors.

Neuroprotection of a Novel Cyclopeptide C*HSDGIC* from the Cyclization of PACAP (1–5) in Cellular and Rodent Models of Retinal Ganglion Cell Apoptosis

PubMed Central

Cheng, Huanhuan; Ding, Yong; Yu, Rongjie; Chen, Jiansu; Wu, Chunyun

2014-01-01

Purpose To investigate the protective effects of a novel cyclopeptide C*HSDGIC* (CHC) from the cyclization of Pituitary adenylate cyclase-activating polypeptide (PACAP) (1–5) in cellular and rodent models of retinal ganglion cell apoptosis. Methodology/Principal Findings Double-labeling immunohistochemistry was used to detect the expression of Thy-1 and PACAP receptor type 1 in a retinal ganglion cell line RGC-5. The apoptosis of RGC-5 cells was induced by 0.02 J/cm2 Ultraviolet B irradiation. MTT assay, flow cytometry, fluorescence microscopy were used to investigate the viability, the level of reactive oxygen species (ROS) and apoptosis of RGC-5 cells respectively. CHC attenuated apoptotic cell death induced by Ultraviolet B irradiation and inhibited the excessive generation of ROS. Moreover, CHC treatment resulted in decreased expression of Bax and concomitant increase of Bcl-2, as was revealed by western-blot analysis. The in vivo apoptosis of retinal ganglion cells was induced by injecting 50 mM N-methyl-D-aspartate (NMDA) (100 nmol in a 2 µL saline solution) intravitreally, and different dosages of CHC were administered. At day 7, rats in CHC+ NMDA-treated groups showed obvious aversion to light when compared to NMDA rats. Electroretinogram recordings revealed a marked decrease in the amplitudes of a-wave, b-wave, and photopic negative response due to NMDA damage. In retina receiving intravitreal NMDA and CHC co-treatment, these values were significantly increased. CHC treatment also resulted in less NMDA-induced cell loss and a decrease in the proportion of dUTP end-labeling-positive cells in ganglion cell line. Conclusions C*HSDGIC*, a novel cyclopeptide from PACAP (1–5) attenuates apoptosis in RGC-5 cells and inhibits NMDA-induced retinal neuronal death. The beneficial effects may occur via the mitochondria pathway. PACAP derivatives like CHC may serve as a promising candidate for neuroprotection in glaucoma. PMID:25286089

Involvement of N-methyl-d-aspartate receptors in the antidepressant-like effect of 5-hydroxytryptamine 3 antagonists in mouse forced swimming test and tail suspension test.

PubMed

Kordjazy, Nastaran; Haj-Mirzaian, Arya; Amiri, Shayan; Ostadhadi, Sattar; Amini-Khoei, Hossein; Dehpour, Ahmad Reza

2016-02-01

Recent evidence indicates that 5-hydroxytryptamine 3 (5-HT3) antagonists such as ondansetron and tropisetron exert positive behavioral effects in animal models of depression. Due to the ionotropic nature of 5-HT3 and N-methyl-d-aspartate (NMDA) receptors, plus their contribution to the pathophysiology of depression, we investigated the possible role of NMDA receptors in the antidepressant-like effect of 5-HT3 receptor antagonists in male mice. In order to evaluate the animals' behavior in response to different treatments, we performed open-field test (OFT), forced swimming test (FST), and tail-suspension test (TST), which are considered as valid tasks for measuring locomotor activity and depressive-like behaviors in mice. Our data revealed that intraperitoneal (i.p.) administration of tropisetron (5, 10, and 30mg/kg) and ondansetron (0.01, and 0.1μg/kg) significantly decreased the immobility time in FST and TST. Also, co-administration of subeffective doses of tropisetron (1mg/kg, i.p.) or ondansetron (0.001μg/kg, i.p.) with subeffective doses of NMDA receptor antagonists, ketamine (1mg/kg, i.p.), MK-801 (0.05mg/kg, i.p.) and magnesium sulfate (10mg/kg, i.p.) resulted in a reduced immobility time both in FST and TST. The subeffective dose of NMDA (NMDA receptor agonist, 75mg/kg, i.p.) abolished the effects of 5-HT3 antagonists in FST and TST, further supporting the presumed interaction between 5-HT3 and NMDA receptors. These treatments did not affect the locomotor behavior of animals in OFT. Finally, the results of our study suggest that the positive effects of 5-HT3 antagonists on the coping behavior of mice in FST and TST are at least partly mediated through NMDA receptors participation. Copyright © 2015 Elsevier Inc. All rights reserved.

Mitochondrial uncoupling agents antagonize rotenone actions in rat substantia nigra dopamine neurons.

PubMed

Wu, Yan-Na; Munhall, Adam C; Johnson, Steven W

2011-06-13

Mild uncoupling of oxidative phosphorylation has been reported to reduce generation of reactive oxygen species (ROS) and therefore may be neuroprotective. We reported previously that the mitochondrial poison rotenone enhanced currents evoked by N-methyl-D-aspartate (NMDA) by a ROS-dependent mechanism in rat midbrain dopamine neurons. Thus, rotenone, which produces a model of Parkinson's disease in rodents, may increase the risk of dopamine neuron excitotoxicity. The purpose of this study was to test the hypothesis that oxidative phosphorylation uncoupling agents would antagonize the effect of rotenone on NMDA current. We used patch pipettes to record whole-cell currents under voltage-clamp (-60 mV) in substantia nigra dopamine neurons in slices of rat brain. Rotenone, NMDA and uncoupling agents were added to the brain slice superfusate. Inward currents evoked by NMDA (30 μM) more than doubled in amplitude after slices were superfused for 30 min with 100 nM rotenone. Continuous superfusion with the uncoupling agent carbonyl cyanide-p-trifluoromethoxy-phenylhydrazone (1-3 nM) or 2,4-dinitrophenol (100 nM) significantly antagonized and delayed the ability of rotenone to potentiate NMDA currents. Coenzyme Q₁₀ (1-10 nM), which has been reported to facilitate uncoupling protein activity, also antagonized this action of rotenone. These results suggest that mild uncoupling of oxidative phosphorylation may protect dopamine neurons against injury from mitochondrial poisons such as rotenone. Published by Elsevier B.V.

Negative Allosteric Modulators Selective for The NR2B Subtype of The NMDA Receptor Impair Cognition in Multiple Domains

PubMed Central

Weed, Michael R; Bookbinder, Mark; Polino, Joseph; Keavy, Deborah; Cardinal, Rudolf N; Simmermacher-Mayer, Jean; Cometa, Fu-ni L; King, Dalton; Thangathirupathy, Srinivasan; Macor, John E; Bristow, Linda J

2016-01-01

Antidepressant activity of N-methyl-D-aspartate (NMDA) receptor antagonists and negative allosteric modulators (NAMs) has led to increased investigation of their behavioral pharmacology. NMDA antagonists, such as ketamine, impair cognition in multiple species and in multiple cognitive domains. However, studies with NR2B subtype-selective NAMs have reported mixed results in rodents including increased impulsivity, no effect on cognition, impairment or even improvement of some cognitive tasks. To date, the effects of NR2B-selective NAMs on cognitive tests have not been reported in nonhuman primates. The current study evaluated two selective NR2B NAMs, CP101,606 and BMT-108908, along with the nonselective NMDA antagonists, ketamine and AZD6765, in the nonhuman primate Cambridge Neuropsychological Test Automated Battery (CANTAB) list-based delayed match to sample (list-DMS) task. Ketamine and the two NMDA NR2B NAMs produced selective impairments in memory in the list-DMS task. AZD6765 impaired performance in a non-specific manner. In a separate cohort, CP101,606 impaired performance of the nonhuman primate CANTAB visuo-spatial Paired Associates Learning (vsPAL) task with a selective impairment at more difficult conditions. The results of these studies clearly show that systemic administration of a selective NR2B NAM can cause transient cognitive impairment in multiple cognitive domains. PMID:26105137

Evidence for involvement of nitric oxide and GABAB receptors in MK-801- stimulated release of glutamate in rat prefrontal cortex

PubMed Central

Roenker, Nicole L.; Gudelsky, Gary A.; Ahlbrand, Rebecca; Horn, Paul S.; Richtand, Neil M.

2012-01-01

Systemic administration of NMDA receptor antagonists elevates extracellular glutamate within prefrontal cortex. The cognitive and behavioral effects of NMDA receptor blockade have direct relevance to symptoms of schizophrenia, and recent studies demonstrate an important role for nitric oxide and GABAB receptors in mediating the effects of NMDA receptor blockade on these behaviors. We sought to extend those observations by directly measuring the effects of nitric oxide and GABAB receptor mechanisms on MK-801-induced glutamate release in the prefrontal cortex. Systemic MK-801 injection (0.3 mg/kg) to male Sprague-Dawley rats significantly increased extracellular glutamate levels in prefrontal cortex, as determined by microdialysis. This effect was blocked by pretreatment with the nitric oxide synthase inhibitor L-NAME (60 mg/kg). Reverse dialysis of the nitric oxide donor SNAP (0.5 – 5 mM) directly into prefrontal cortex mimicked the effect of systemic MK-801, dose-dependently elevating cortical extracellular glutamate. The effect of MK-801 was also blocked by systemic treatment with the GABAB receptor agonist baclofen (5 mg/kg). In combination, these data suggest increased nitric oxide formation is necessary for NMDA antagonist-induced elevations of extracellular glutamate in the prefrontal cortex. Additionally, the data suggest GABAB receptor activation can modulate the NMDA antagonist-induced increase in cortical glutamate release. PMID:22579658

NMDA Receptor Modulators in the Treatment of Drug Addiction.

PubMed

Tomek, Seven E; Lacrosse, Amber L; Nemirovsky, Natali E; Olive, M Foster

2013-02-06

Glutamate plays a pivotal role in drug addiction, and the N-methyl-D-aspartate (NMDA) glutamate receptor subtype serves as a molecular target for several drugs of abuse. In this review, we will provide an overview of NMDA receptor structure and function, followed by a review of the mechanism of action, clinical efficacy, and side effect profile of NMDA receptor ligands that are currently in use or being explored for the treatment of drug addiction. These ligands include the NMDA receptor modulators memantine and acamprosate, as well as the partial NMDA agonist D-cycloserine. Data collected to date suggest that direct NMDA receptor modulators have relatively limited efficacy in the treatment of drug addiction, and that partial agonism of NMDA receptors may have some efficacy with regards to extinction learning during cue exposure therapy. However, the lack of consistency in results to date clearly indicates that additional studies are needed, as are studies examining novel ligands with indirect mechanisms for altering NMDA receptor function.

Bisphenol-A rapidly promotes dynamic changes in hippocampal dendritic morphology through estrogen receptor-mediated pathway by concomitant phosphorylation of NMDA receptor subunit NR2B

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

Xu Xiaohong, E-mail: xuxh63@zjnu.cn; Ye Yinping; Li Tao

Bisphenol-A (BPA) is known to be a potent endocrine disrupter. Evidence is emerging that estrogen exerts a rapid influence on hippocampal synaptic plasticity and the dendritic spine density, which requires activation of NMDA receptors. In the present study, we investigated the effects of BPA (ranging from 1 to 1000 nM), focusing on the rapid dynamic changes in dendritic filopodia and the expressions of estrogen receptor (ER) {beta} and NMDA receptor, as well as the phosphorylation of NMDA receptor subunit NR2B in the cultured hippocampal neurons. A specific ER antagonist ICI 182,780 was used to examine the potential involvement of ERs.more » The results demonstrated that exposure to BPA (ranging from 10 to 1000 nM) for 30 min rapidly enhanced the motility and the density of dendritic filopodia in the cultured hippocampal neurons, as well as the phosphorylation of NR2B (pNR2B), though the expressions of NMDA receptor subunits NR1, NR2B, and ER{beta} were not changed. The antagonist of ERs completely inhibited the BPA-induced increases in the filopodial motility and the number of filopodia extending from dendrites. The increased pNR2B induced by BPA (100 nM) was also completely eliminated. Furthermore, BPA attenuated the effects of 17{beta}-estradiol (17{beta}-E{sub 2}) on the dendritic filopodia outgrowth and the expression of pNR2B when BPA was co-treated with 17{beta}-E{sub 2}. The present results suggest that BPA, like 17{beta}-E{sub 2}, rapidly results in the enhanced motility and density of dendritic filopodia in the cultured hippocampal neurons with the concomitant activation of NMDA receptor subunit NR2B via an ER-mediated signaling pathway. Meanwhile, BPA suppressed the enhancement effects of 17{beta}-E{sub 2} when it coexists with 17{beta}-E{sub 2}. These results provided important evidence suggesting the neurotoxicity of the low levels of BPA during the early postnatal development of the brain.« less

NMDA receptor modulators: an updated patent review (2013-2014).

PubMed

Strong, Katie L; Jing, Yao; Prosser, Anthony R; Traynelis, Stephen F; Liotta, Dennis C

2014-12-01

The NMDA receptor mediates a slow component of excitatory synaptic transmission, and NMDA receptor dysfunction has been implicated in numerous neurological disorders. Thus, interest in developing modulators that are capable of regulating the channel continues to be strong. Recent research has led to the discovery of a number of compounds that hold therapeutic and clinical value. Deeper insight into the NMDA intersubunit interactions and structural motifs gleaned from the recently solved crystal structures of the NMDA receptor should facilitate a deeper understanding of how these compounds modulate the receptor. This article discusses the known pharmacology of NMDA receptors. A discussion of the patent literature since 2012 is also included, with an emphasis on those that claimed new chemical entities as regulators of the NMDA receptor. The number of patents involving novel NMDA receptor modulators suggests a renewed interest in the NMDA receptor as a therapeutic target. Subunit-selective modulators continue to show promise, and the development of new subunit-selective NMDA receptor modulators appears poised for continued growth. Although a modest number of channel blocker patents were published, successful clinical outcomes involving ketamine have led to a resurgent interest in low-affinity channel blockers as therapeutics.

A segmental chronic pain syndrome in rats associated with intrathecal infusion of NMDA: evidence for selective action in the dorsal horn.

PubMed

Zochodne, D W; Murray, M; Nag, S; Riopelle, R J

1994-02-01

We explored the effects of chronic lumbar intrathecal NMDA infusion (mini-osmotic pumps) in Sprague-Dawley rats on motor and sensory axon integrity. Several different infusion protocols, each given over a 4 week period were examined: 0.15 M NMDA in phosphate buffered saline; phosphate buffered saline without NMDA; and 0.20 M magnesium sulfate plus 0.15 M NMDA; 0.35 M NMDA. In two additional protocols, 0.15 M NMDA or phosphate buffered saline were infused for a total of 8 weeks. Within 1-2 weeks of the onset of NMDA, but not phosphate buffered saline infusions, the rats exhibited irritability, circling, biting and excessive grooming resulting in loss of hair, and skin ulcerations from autotomy localized to lumbar and sacral innervated dermatomes. Co-infusion of NMDA with magnesium sulfate almost completely prevented these findings. The behavioural changes were not associated with abnormalities of sensory or motor conduction. Intrathecal infusion of NMDA induces a chronic "central" experimental pain disorder in rats, localized to the cord segment with the greatest exposure to the infusion, without involvement of peripheral sensory axons and sparing the axonal integrity of anterior horn cells.

Modulating NMDA Receptor Function with D-Amino Acid Oxidase Inhibitors: Understanding Functional Activity in PCP-Treated Mouse Model

PubMed Central

Sershen, Henry; Hashim, Audrey; Dunlop, David S.; Suckow, Raymond F.; Cooper, Tom B.; Javitt, Daniel C.

2016-01-01

Deficits in N-methyl-D-aspartate receptor (NMDAR) function are increasingly linked to persistent negative symptoms and cognitive deficits in schizophrenia. Accordingly, clinical studies have been targeting the modulatory site of the NMDA receptor, based on the decreased function of NMDA receptor, to see whether increasing NMDA function can potentially help treat the negative and cognitive deficits seen in the disease. Glycine and D-serine are endogenous ligands to the NMDA modulatory site, but since high doses are needed to affect brain levels, related compounds are being developed, for example glycine transport (GlyT) inhibitors to potentially elevate brain glycine or targeting enzymes, such as D-amino acid oxidase (DAAO) to slow the breakdown and increase the brain level of D-serine. In the present study we further evaluated the effect of DAAO inhibitors 5-chloro-benzo[d]isoxazol-3-ol (CBIO) and sodium benzoate (NaB) in a phencyclidine (PCP) rodent mouse model to see if the inhibitors affect PCP-induced locomotor activity, alter brain D-serine level, and thereby potentially enhance D-serine responses. D-Serine dose-dependently reduced the PCP-induced locomotor activity at doses above 1000 mg/kg. Acute CBIO (30 mg/kg) did not affect PCP-induced locomotor activity, but appeared to reduce locomotor activity when given with D-serine (600 mg/kg); a dose that by itself did not have an effect. However, the effect was also present when the vehicle (Trappsol®) was tested with D-serine, suggesting that the reduction in locomotor activity was not related to DAAO inhibition, but possibly reflected enhanced bioavailability of D-serine across the blood brain barrier related to the vehicle. With this acute dose of CBIO, D-serine level in brain and plasma were not increased. Another weaker DAAO inhibitor sodium benzoate (NaB) (400 mg/kg), and NaB plus D-serine also significantly reduced PCP-induced locomotor activity, but without affecting plasma or brain D-serine level, arguing against a DAAO-mediated effect. However, NaB reduced plasma L-serine and based on reports that NaB also elevates various plasma metabolites, for example aminoisobutyric acid (AIB), a potential effect via the System A amino acid carrier may be involved in the regulation of synaptic glycine level to modulate NMDAR function needs to be investigated. Acute ascorbic acid (300 mg/kg) also inhibited PCP-induced locomotor activity, which was further attenuated in the presence of D-serine (600 mg/kg). Ascorbic acid may have an action at the dopamine membrane carrier and/or altering redox mechanisms that modulate NMDARs, but this needs to be further investigated. The findings support an effect of D-serine on PCP-induced hyperactivity. They also offer suggestions on an interaction of NaB via an unknown mechanism, other than DAAO inhibition, perhaps through metabolomic changes, and find unexpected synergy between D-serine and ascorbic acid that supports combined NMDA glycine- and redox-site intervention. Although mechanisms of these specific agents need to be determined, overall it supports continued glutamatergic drug development. PMID:26857796

Quinolinic acid induces neuritogenesis in SH-SY5Y neuroblastoma cells independently of NMDA receptor activation.

PubMed

Hernandez-Martinez, Juan-Manuel; Forrest, Caroline M; Darlington, L Gail; Smith, Robert A; Stone, Trevor W

2017-03-01

Glutamate and nicotinamide adenine dinucleotide (NAD + ) have been implicated in neuronal development and several types of cancer. The kynurenine pathway of tryptophan metabolism includes quinolinic acid (QA) which is both a selective agonist at N-methyl-D-aspartate (NMDA) receptors and also a precursor for the formation of NAD + . The effect of QA on cell survival and differentiation has therefore been examined on SH-SY5Y human neuroblastoma cells. Retinoic acid (RA, 10 μm) induced differentiation of SH-SY5Y cells into a neuronal phenotype showing neurite growth. QA (50-150 nm) also caused a concentration-dependent increase in the neurite/soma ratio, indicating differentiation. Both RA and QA increased expression of the neuronal marker β3-tubulin in whole-cell homogenates and in the neuritic fraction assessed using a neurite outgrowth assay. Expression of the neuronal proliferation marker doublecortin revealed that, unlike RA, QA did not decrease the number of mitotic cells. QA-induced neuritogenesis coincided with an increase in the generation of reactive oxygen species. Neuritogenesis was prevented by diphenylene-iodonium (an inhibitor of NADPH oxidase) and superoxide dismutase, supporting the involvement of reactive oxygen species. NMDA itself did not promote neuritogenesis and the NMDA antagonist dizocilpine (MK-801) did not prevent quinolinate-induced neuritogenesis, indicating that the effects of QA were independent of NMDA receptors. Nicotinamide caused a significant increase in the neurite/soma ratio and the expression of β3-tubulin in the neuritic fraction. Taken together, these results suggest that QA induces neuritogenesis by promoting oxidizing conditions and affecting the availability of NAD + , independently of NMDA receptors. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Increased cerebral oxygen consumption in Eker rats and effects of N-methyl-D-aspartate blockade: Implications for autism.

PubMed

Weiss, Harvey R; Liu, Xia; Zhang, Qihang; Chi, Oak Z

2007-08-15

Because there is a strong correlation between tuberous sclerosis and autism, we used a tuberous sclerosis model (Eker rat) to test the hypothesis that these animals would have an altered regional cerebral O2 consumption that might be associated with autism. We also examined whether the altered cerebral O2 consumption was related to changes in the importance of N-methyl-D-aspartate (NMDA) receptors. Young (4 weeks) male control Long Evans (N = 14) and Eker (N = 14) rats (70-100 g) were divided into control and CGS-19755 (10 mg/kg, competitive NMDA antagonist)-treated animals. Cerebral regional blood flow (14C-iodoantipyrine) and O2 consumption (cryomicrospectrophotometry) were determined in isoflurane-anesthetized rats. NMDA receptor protein levels were determined by Western immunoblotting. We found significantly increased basal O2 consumption in the cortex (6.2 +/- 0.6 ml O2/min/100 g Eker vs. 4.7 +/- 0.4 Long Evans), hippocampus, cerebellum, and pons. Regional cerebral blood flow was also elevated in Eker rats at baseline, but cerebral O2 extraction was similar. CGS-19755 significantly lowered O2 consumption in the cortex (2.8 +/- 0.3), hippocampus, and pons of the Long Evans rats but had no effect on cortex (5.8 +/- 0.8) or other regions of the Eker rats. Cerebral blood flow followed a similar pattern. NMDA receptor protein levels (NR1 subunit) were similar between groups. In conclusion, Eker rats had significantly elevated cerebral O2 consumption and blood flow, but this was not related to NMDA receptor activation. In fact, the importance of NMDA receptors in the control of basal cerebral O2 consumption was reduced. This might have important implications in the treatment of autism. Copyright 2007 Wiley-Liss, Inc.

Periaqueductal gray glutamatergic, cannabinoid and vanilloid receptor interplay in defensive behavior and aversive memory formation.

PubMed

Back, Franklin P; Carobrez, Antonio P

2018-06-01

Stimulation of the midbrain periaqueductal gray matter (PAG) in humans elicits sensations of fear and impending terror, and mediates predator defensive responses in rodents. In rats, pharmacological stimulation of the dorsolateral portion of the PAG (dlPAG) with N-Methyl-d-Aspartate (NMDA) induces aversive conditioning that acts as an unconditioned stimulus (US). In the present work, we investigated the interplay between the vanilloid TRPV1 and cannabinoid CB1 receptors in the NMDA-dlPAG defensive response and in subsequent aversive learning. Rats were subjected to dlPAG NMDA infusion in an olfactory conditioned stimulus (CS) task allowing the evaluation of immediate and long-term defensive behavioral responses during CS presentation. The results indicated that an intermediate dose of NMDA (50 pmol) induced both immediate and long-term effects. A sub-effective dose of NMDA (25 pmol) was potentiated by the TRPV1 receptor agonist capsaicin (CAP, 1 nmol) and the CB1 receptor antagonist, AM251 (200 pmol). CAP (10 nmol) or the combination of CAP (1 nmol) and AM251 (200 pmol) induced long-term effects without increasing immediate defensive responses. The glutamate release inhibitor riluzole (2 or 4 nmol) and the AMPA/kainate receptor antagonist DNQX (2 or 4 nmol) potentiated the immediate effects but blocked the long-term effects. The results showed that immediate defensive responses rely on NMDA receptors, and aversive learning on the fine-tuning of TRPV1, CB1, metabotropic glutamate and AMPA receptors located in pre- and postsynaptic membranes. In conclusion, the activity of the dlPAG determines core affective aspects of aversive memory formation controlled by local TRPV1/CB1 balance. Copyright © 2018 Elsevier Ltd. All rights reserved.

Separate Intramolecular Targets for Protein Kinase A Control N-Methyl-d-aspartate Receptor Gating and Ca2+ Permeability*

PubMed Central

Aman, Teresa K.; Maki, Bruce A.; Ruffino, Thomas J.; Kasperek, Eileen M.; Popescu, Gabriela K.

2014-01-01

Protein kinase A (PKA) enhances synaptic plasticity in the central nervous system by increasing NMDA receptor current amplitude and Ca2+ flux in an isoform-dependent yet poorly understood manner. PKA phosphorylates multiple residues on GluN1, GluN2A, and GluN2B subunits in vivo, but the functional significance of this multiplicity is unknown. We examined gating and permeation properties of recombinant NMDA receptor isoforms and of receptors with altered C-terminal domain (CTDs) prior to and after pharmacological inhibition of PKA. We found that PKA inhibition decreased GluN1/GluN2B but not GluN1/GluN2A gating; this effect was due to slower rates for receptor activation and resensitization and was mediated exclusively by the GluN2B CTD. In contrast, PKA inhibition reduced NMDA receptor-relative Ca2+ permeability (PCa/PNa) regardless of the GluN2 isoform and required the GluN1 CTD; this effect was due primarily to decreased unitary Ca2+ conductance, because neither Na+ conductance nor Ca2+-dependent block was altered substantially. Finally, we show that both the gating and permeation effects can be reproduced by changing the phosphorylation state of a single residue: GluN2B Ser-1166 and GluN1 Ser-897, respectively. We conclude that PKA effects on NMDA receptor gating and Ca2+ permeability rely on distinct phosphorylation sites located on the CTD of GluN2B and GluN1 subunits. This separate control of NMDA receptor properties by PKA may account for the specific effects of PKA on plasticity during synaptic development and may lead to drugs targeted to alter NMDA receptor gating or Ca2+ permeability. PMID:24847051

Access of inhibitory neurosteroids to the NMDA receptor

PubMed Central

Borovska, Jirina; Vyklicky, Vojtech; Stastna, Eva; Kapras, Vojtech; Slavikova, Barbora; Horak, Martin; Chodounska, Hana; Vyklicky Jr, Ladislav

2012-01-01

BACKGROUND AND PURPOSE NMDA receptors are glutamatergic ionotropic receptors involved in excitatory neurotransmission, synaptic plasticity and excitotoxic cell death. Many allosteric modulators can influence the activity of these receptors positively or negatively, with behavioural consequences. 20-Oxo-5β-pregnan-3α-yl sulphate (pregnanolone sulphate; PA-6) is an endogenous neurosteroid that inhibits NMDA receptors and is neuroprotective. We tested the hypothesis that the interaction of PA-6 with the plasma membrane is critical for its inhibitory effect at NMDA receptors. EXPERIMENTAL APPROACH Electrophysiological recordings and live microscopy were performed on heterologous HEK293 cells expressing GluN1/GluN2B receptors and cultured rat hippocampal neurons. KEY RESULTS Our experiments showed that the kinetics of the steroid inhibition were slow and not typical of drug-receptor interaction in an aqueous solution. In addition, the recovery from steroid inhibition was accelerated by β- and γ-cyclodextrin. Values of IC50 assessed for novel synthetic C3 analogues of PA-6 differed by more than 30-fold and were positively correlated with the lipophilicity of the PA-6 analogues. Finally, the onset of inhibition induced by C3 analogues of PA-6 ranged from use-dependent to use-independent. The onset and offset of cell staining by fluorescent analogues of PA-6 were slower than those of steroid-induced inhibition of current responses mediated by NMDA receptors. CONCLUSION AND IMPLICATIONS We conclude that steroid accumulation in the plasma membrane is the route by which it accesses a binding site on the NMDA receptor. Thus, our results provide a possible structural framework for pharmacologically targeting the transmembrane domains of the receptor. PMID:22188257

The spread of Ras activity triggered by activation of a single dendritic spine.

PubMed

Harvey, Christopher D; Yasuda, Ryohei; Zhong, Haining; Svoboda, Karel

2008-07-04

In neurons, individual dendritic spines isolate N-methyl-d-aspartate (NMDA) receptor-mediated calcium ion (Ca2+) accumulations from the dendrite and other spines. However, the extent to which spines compartmentalize signaling events downstream of Ca2+ influx is not known. We combined two-photon fluorescence lifetime imaging with two-photon glutamate uncaging to image the activity of the small guanosine triphosphatase Ras after NMDA receptor activation at individual spines. Induction of long-term potentiation (LTP) triggered robust Ca2+-dependent Ras activation in single spines that decayed in approximately 5 minutes. Ras activity spread over approximately 10 micrometers of dendrite and invaded neighboring spines by diffusion. The spread of Ras-dependent signaling was necessary for the local regulation of the threshold for LTP induction. Thus, Ca2+-dependent synaptic signals can spread to couple multiple synapses on short stretches of dendrite.

Spinal sigma-1 receptor activation increases the production of D-serine in astrocytes which contributes to the development of mechanical allodynia in a mouse model of neuropathic pain.

PubMed

Moon, Ji-Young; Choi, Sheu-Ran; Roh, Dae-Hyun; Yoon, Seo-Yeon; Kwon, Soon-Gu; Choi, Hoon-Seong; Kang, Suk-Yun; Han, Ho-Jae; Kim, Hyun-Woo; Beitz, Alvin J; Oh, Seog-Bae; Lee, Jang-Hern

2015-10-01

We have previously demonstrated that activation of the spinal sigma-1 receptor (Sig-1R) plays an important role in the development of mechanical allodynia (MA) via secondary activation of the N-methyl-d-aspartate (NMDA) receptor. Sig-1Rs have been shown to localize to astrocytes, and blockade of Sig-1Rs inhibits the pathologic activation of astrocytes in neuropathic mice. However, the mechanism by which Sig-1R activation in astrocytes modulates NMDA receptors in neurons is currently unknown. d-serine, synthesized from l-serine by serine racemase (Srr) in astrocytes, is an endogenous co-agonist for the NMDA receptor glycine site and can control NMDA receptor activity. Here, we investigated the role of d-serine in the development of MA induced by spinal Sig-1R activation in chronic constriction injury (CCI) mice. The production of d-serine and Srr expression were both significantly increased in the spinal cord dorsal horn post-CCI surgery. Srr and d-serine were only localized to astrocytes in the superficial dorsal horn, while d-serine was also localized to neurons in the deep dorsal horn. Moreover, we found that Srr exists in astrocytes that express Sig-1Rs. The CCI-induced increase in the levels of d-serine and Srr was attenuated by sustained intrathecal treatment with the Sig-1R antagonist, BD-1047 during the induction phase of neuropathic pain. In behavioral experiments, degradation of endogenous d-serine with DAAO, or selective blockade of Srr by LSOS, effectively reduced the development of MA, but not thermal hyperalgesia in CCI mice. Finally, BD-1047 administration inhibited the development of MA and this inhibition was reversed by intrathecal treatment with exogenous d-serine. These findings demonstrate for the first time that the activation of Sig-1Rs increases the expression of Srr and d-serine in astrocytes. The increased production of d-serine induced by CCI ultimately affects dorsal horn neurons that are involved in the development of MA in neuropathic mice. Copyright © 2015 Elsevier Ltd. All rights reserved.

NMDA inhibits oxotremorine-induced acid secretion via the NO-dependent cyclic GMP system in rat stomach.

PubMed

Tsai, L H; Lee, Y J

2001-12-31

The mechanism of N-methyl-D-aspartate (NMDA) inhibits oxotremorine-induced acid secretion was examined in rat stomach, in relation to the cyclic GMP system. NMDA (10(-7) M) did not affect the spontaneous acid secretion from the everted preparations of isolated rat stomach, but inhibited the acid secretion stimulated by oxotremorine, and this effect of NMDA was antagonized by 2-amino-5-phosphonovaleric acid (AP-5), (+/-)3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) or N(G)-nitro-L-arginine (L-NNA). NMDA also elevated the cyclic GMP content of mucosal slices from rat stomach, and this effect of NMDA was antagonized by L-NNA. These results indicate that NMDA receptors are present in the rat stomach and regulate the gastric acid secretion. The mechanism underlying the effect of NMDA inhibits oxotremorine-induced acid secretion may be mediated by the NO-dependent cyclic GMP system.

Novel Functional Properties of Drosophila CNS Glutamate Receptors

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

Li, Yan; Dharkar, Poorva; Han, Tae-Hee

Phylogenetic analysis reveals AMPA, kainate, and NMDA receptor families in insect genomes, suggesting conserved functional properties corresponding to their vertebrate counterparts. However, heterologous expression of the Drosophila kainate receptor DKaiR1D and the AMPA receptor DGluR1A revealed novel ligand selectivity at odds with the classification used for vertebrate glutamate receptor ion channels (iGluRs). DKaiR1D forms a rapidly activating and desensitizing receptor that is inhibited by both NMDA and the NMDA receptor antagonist AP5; crystallization of the KaiR1D ligand-binding domain reveals that these ligands stabilize open cleft conformations, explaining their action as antagonists. Surprisingly, the AMPA receptor DGluR1A shows weak activation bymore » its namesake agonist AMPA and also by quisqualate. Crystallization of the DGluR1A ligand-binding domain reveals amino acid exchanges that interfere with binding of these ligands. The unexpected ligand-binding profiles of insect iGluRs allows classical tools to be used in novel approaches for the study of synaptic regulation.« less

Magnesium ions and opioid agonists in vincristine-induced neuropathy.

PubMed

Bujalska, Magdalena; Makulska-Nowak, Helena; Gumułka, Stanisław W

2009-01-01

Neuropathic pain is difficult to treat. Classic analgesics (i.e., opioid receptor agonists) usually possess low activity. Therefore other agents such as antidepressants, anticonvulsants, and corticosteroids are used. It is commonly known that NMDA antagonists increase analgesic activity of opioids. Unfortunately, clinical use of NMDA antagonists is limited because of the relatively frequent occurrence of adverse effects e.g., memory impairment, psychomimetic effects, ataxia and motor in-coordination. Magnesium ions (Mg(2+)) are NMDA receptor blockers in physiological conditions. Therefore, in this study the effect of opioid receptor agonists and the influence of Mg(2+) on the action of opioid agonists in vincristine-induced hyperalgesia were examined. Opioid agonists such as morphine (5 mg/kg, ip), and fentanyl (0.0625 mg/kg, ip), as well as the partial agonist buprenorphine (0.075 mg/kg, ip) administered alone on 5 consecutives days did not modify the hyperalgesia in vincristine rats. In contrast, pretreatment with a low dose of magnesium sulfate (30 mg/kg, ip) resulted in a progressive increase of the analgesic action of all three investigated opioids. After discontinuation of drug administration, the effect persisted for several days.

Functional ionotropic glutamate receptors on peripheral axons and myelin.

PubMed

Christensen, Pia Crone; Welch, Nicole Cheryl; Brideau, Craig; Stys, Peter K

2016-09-01

Neurotransmitter-dependent signaling is traditionally restricted to axon terminals. However, receptors are present on myelinating glia, suggesting that chemical transmission may also occur along axons. Confocal microscopy and Ca(2+) -imaging using an axonally expressed FRET-based reporter was used to measure Ca(2+) changes and morphological alterations in myelin in response to stimulation of glutamate receptors. Activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) or N-methyl-D-aspartate (NMDA) receptors induced a Ca(2+) increase in axon cylinders. However, only the latter caused structural alterations in axons, despite similar Ca(2+) increases. Myelin morphology was significantly altered by NMDA receptor activation, but not by AMPA receptors. Cu(2+) ions influenced the NMDA receptor-dependent response, suggesting that this metal modulates axonal receptors. Glutamate increased ribosomal signal in Schwann cell cytoplasm. Axon cylinders and myelin of peripheral nervous system axons respond to glutamate, with a consequence being an increase in Schwann cell ribosomes. This may have implications for nerve pathology and regeneration. Muscle Nerve 54: 451-459, 2016. © 2016 Wiley Periodicals, Inc.

Presynaptic serotonin 2A receptors modulate thalamocortical plasticity and associative learning

PubMed Central

Barre, Alexander; Berthoux, Coralie; De Bundel, Dimitri; Valjent, Emmanuel; Bockaert, Joël; Marin, Philippe; Bécamel, Carine

2016-01-01

Higher-level cognitive processes strongly depend on a complex interplay between mediodorsal thalamus nuclei and the prefrontal cortex (PFC). Alteration of thalamofrontal connectivity has been involved in cognitive deficits of schizophrenia. Prefrontal serotonin (5-HT)2A receptors play an essential role in cortical network activity, but the mechanism underlying their modulation of glutamatergic transmission and plasticity at thalamocortical synapses remains largely unexplored. Here, we show that 5-HT2A receptor activation enhances NMDA transmission and gates the induction of temporal-dependent plasticity mediated by NMDA receptors at thalamocortical synapses in acute PFC slices. Expressing 5-HT2A receptors in the mediodorsal thalamus (presynaptic site) of 5-HT2A receptor-deficient mice, but not in the PFC (postsynaptic site), using a viral gene-delivery approach, rescued the otherwise absent potentiation of NMDA transmission, induction of temporal plasticity, and deficit in associative memory. These results provide, to our knowledge, the first physiological evidence of a role of presynaptic 5-HT2A receptors located at thalamocortical synapses in the control of thalamofrontal connectivity and the associated cognitive functions. PMID:26903620

NMDA receptor-mediated long term modulation of electrically evoked field potentials in the rat medial vestibular nuclei.

PubMed

Capocchi, G; Della Torre, G; Grassi, S; Pettorossi, V E; Zampolini, M

1992-01-01

The effect of high frequency stimulation (HFS) of the primary vestibular afferents on field potentials recorded in the ipsilateral Medial Vestibular Nuclei (MVN) was studied. Our results show that potentiation and depression can be induced in different portions of MVN, which are distinguishable by their anatomical organization. HFS induces potentiation of the monosynaptic component in the ventral portion of the MVN, whereas it provokes depression of the polysynaptic component in the dorsal portion of the same nucleus. The induction of both potentiation and depression was blocked under AP5 perfusion, thus demonstrating that NMDA receptor activation mediates both phenomena. Furthermore, the finding that the field potentials were not modified during perfusion with DL-AP5, as previously reported, supports the hypothesis that NMDA receptors are not involved in the normal synaptic transmission from the primary vestibular afferent fibres, but are only activated following hyperstimulation of this afferent system. Our results suggest that the mechanisms of long term modification of synaptic efficacy observed in MVN may underlie the plasticity phenomena occurring in vestibular nuclei.

Novel Functional Properties of Drosophila CNS Glutamate Receptors.

PubMed

Li, Yan; Dharkar, Poorva; Han, Tae-Hee; Serpe, Mihaela; Lee, Chi-Hon; Mayer, Mark L

2016-12-07

Phylogenetic analysis reveals AMPA, kainate, and NMDA receptor families in insect genomes, suggesting conserved functional properties corresponding to their vertebrate counterparts. However, heterologous expression of the Drosophila kainate receptor DKaiR1D and the AMPA receptor DGluR1A revealed novel ligand selectivity at odds with the classification used for vertebrate glutamate receptor ion channels (iGluRs). DKaiR1D forms a rapidly activating and desensitizing receptor that is inhibited by both NMDA and the NMDA receptor antagonist AP5; crystallization of the KaiR1D ligand-binding domain reveals that these ligands stabilize open cleft conformations, explaining their action as antagonists. Surprisingly, the AMPA receptor DGluR1A shows weak activation by its namesake agonist AMPA and also by quisqualate. Crystallization of the DGluR1A ligand-binding domain reveals amino acid exchanges that interfere with binding of these ligands. The unexpected ligand-binding profiles of insect iGluRs allows classical tools to be used in novel approaches for the study of synaptic regulation. VIDEO ABSTRACT. Published by Elsevier Inc.

The A-Current Modulates Learning via NMDA Receptors Containing the NR2B Subunit

PubMed Central

Fontán-Lozano, Ángela; Suárez-Pereira, Irene; González-Forero, David; Carrión, Ángel Manuel

2011-01-01

Synaptic plasticity involves short- and long-term events, although the molecular mechanisms that underlie these processes are not fully understood. The transient A-type K+ current (IA) controls the excitability of the dendrites from CA1 pyramidal neurons by regulating the back-propagation of action potentials and shaping synaptic input. Here, we have studied how decreases in IA affect cognitive processes and synaptic plasticity. Using wild-type mice treated with 4-AP, an IA inhibitor, and mice lacking the DREAM protein, a transcriptional repressor and modulator of the IA, we demonstrate that impairment of IA decreases the stimulation threshold for learning and the induction of early-LTP. Hippocampal electrical recordings in both models revealed alterations in basal electrical oscillatory properties toward low-theta frequencies. In addition, we demonstrated that the facilitated learning induced by decreased IA requires the activation of NMDA receptors containing the NR2B subunit. Together, these findings point to a balance between the IA and the activity of NR2B-containing NMDA receptors in the regulation of learning. PMID:21966384

Pharmacological Blockade of Serotonin 5-HT7 Receptor Reverses Working Memory Deficits in Rats by Normalizing Cortical Glutamate Neurotransmission

PubMed Central

Bonaventure, Pascal; Aluisio, Leah; Shoblock, James; Boggs, Jamin D.; Fraser, Ian C.; Lord, Brian; Lovenberg, Timothy W.; Galici, Ruggero

2011-01-01

The role of 5-HT7 receptor has been demonstrated in various animal models of mood disorders; however its function in cognition remains largely speculative. This study evaluates the effects of SB-269970, a selective 5-HT7 antagonist, in a translational model of working memory deficit and investigates whether it modulates cortical glutamate and/or dopamine neurotransmission in rats. The effect of SB-269970 was evaluated in the delayed non-matching to position task alone or in combination with MK-801, a non-competitive NMDA receptor antagonist, and, in separate experiments, with scopolamine, a non-selective muscarinic antagonist. SB-269970 (10 mg/kg) significantly reversed the deficits induced by MK-801 (0.1 mg/kg) but augmented the deficit induced by scopolamine (0.06 mg/kg). The ability of SB-269970 to modulate MK-801-induced glutamate and dopamine extracellular levels was separately evaluated using biosensor technology and microdialysis in the prefrontal cortex of freely moving rats. SB-269970 normalized MK-801 -induced glutamate but not dopamine extracellular levels in the prefrontal cortex. Rat plasma and brain concentrations of MK-801 were not affected by co-administration of SB-269970, arguing for a pharmacodynamic rather than a pharmacokinetic mechanism. These results indicate that 5-HT7 receptor antagonists might reverse cognitive deficits associated with NMDA receptor hypofunction by selectively normalizing glutamatergic neurotransmission. PMID:21701689

Evaluation of 11C-Me-NB1 as a Potential PET Radioligand for Measuring GluN2B-Containing NMDA Receptors, Drug Occupancy, and Receptor Cross Talk.

PubMed

Krämer, Stefanie D; Betzel, Thomas; Mu, Linjing; Haider, Ahmed; Herde, Adrienne Müller; Boninsegni, Anna K; Keller, Claudia; Szermerski, Marina; Schibli, Roger; Wünsch, Bernhard; Ametamey, Simon M

2018-04-01

Clinical and preclinical research with modulators at the N -methyl-d-aspartate (NMDA) receptor GluN2B N-terminal domain (NTD) aims for the treatment of various neurologic diseases. The interpretation of the results is hampered by the lack of a suitable NMDA PET tracer for assessing the receptor occupancy of potential drugs. We have developed 11 C-Me-NB1 as a PET tracer for imaging GluN1/GluN2B-containing NMDA receptors and used it to investigate in rats the dose-dependent receptor occupancy of eliprodil, a GluN2B NTD modulator. Methods: 11 C-Me-NB1 was synthesized and characterized by in vitro displacement binding experiments with rat brain membranes, in vitro autoradiography, and blocking and displacement experiments by PET and PET kinetic modeling. Receptor occupancy by eliprodil was studied by PET with 11 C-Me-NB1. Results: 11 C-Me-NB1 was synthesized at 290 ± 90 GBq/μmol molar activity, 7.4 ± 1.9 GBq total activity at the end of synthesis ( n = 17), and more than 99% radiochemical purity. 11 C-Me-NB1 binding in rat brain was blocked in vitro and in vivo by the NTD modulators Ro-25-6981 and eliprodil. Half-maximal receptor occupancy by eliprodil occurred at 1.5 μg/kg. At 1 mg/kg of eliprodil, a dose with reported neuroprotective effects, more than 99.5% of binding sites were occupied. In vitro, 11 C-Me-NB1 binding was independent of the σ-1 receptor (Sigma1R), and the Sigma1R agonist (+)-pentazocine did not compete for high-affinity binding. In vivo, a 2.5 mg/kg dose of (+)-pentazocine abolished 11 C-Me-NB1-specific binding, indicating an indirect effect of Sigma1R on 11 C-Me-NB1 binding. Conclusion: 11 C-Me-NB1 is suitable for the in vivo imaging of NMDA GluN1/GluN2B receptors and the assessment of receptor occupancy by NTD modulators. GluN1/GluN2B NMDA receptors are fully occupied at neuroprotective doses of eliprodil. Furthermore, 11 C-Me-NB1 enables imaging of GluN1/GluN2B NMDA receptor cross talk. © 2018 by the Society of Nuclear Medicine and Molecular Imaging.

Blonanserin Ameliorates Phencyclidine-Induced Visual-Recognition Memory Deficits: the Complex Mechanism of Blonanserin Action Involving D3-5-HT2A and D1-NMDA Receptors in the mPFC

PubMed Central

Hida, Hirotake; Mouri, Akihiro; Mori, Kentaro; Matsumoto, Yurie; Seki, Takeshi; Taniguchi, Masayuki; Yamada, Kiyofumi; Iwamoto, Kunihiro; Ozaki, Norio; Nabeshima, Toshitaka; Noda, Yukihiro

2015-01-01

Blonanserin differs from currently used serotonin 5-HT2A/dopamine-D2 receptor antagonists in that it exhibits higher affinity for dopamine-D2/3 receptors than for serotonin 5-HT2A receptors. We investigated the involvement of dopamine-D3 receptors in the effects of blonanserin on cognitive impairment in an animal model of schizophrenia. We also sought to elucidate the molecular mechanism underlying this involvement. Blonanserin, as well as olanzapine, significantly ameliorated phencyclidine (PCP)-induced impairment of visual-recognition memory, as demonstrated by the novel-object recognition test (NORT) and increased extracellular dopamine levels in the medial prefrontal cortex (mPFC). With blonanserin, both of these effects were antagonized by DOI (a serotonin 5-HT2A receptor agonist) and 7-OH-DPAT (a dopamine-D3 receptor agonist), whereas the effects of olanzapine were antagonized by DOI but not by 7-OH-DPAT. The ameliorating effect was also antagonized by SCH23390 (a dopamine-D1 receptor antagonist) and H-89 (a protein kinase A (PKA) inhibitor). Blonanserin significantly remediated the decrease in phosphorylation levels of PKA at Thr197 and of NR1 (an essential subunit of N-methyl-D-aspartate (NMDA) receptors) at Ser897 by PKA in the mPFC after a NORT training session in the PCP-administered mice. There were no differences in the levels of NR1 phosphorylated at Ser896 by PKC in any group. These results suggest that the ameliorating effect of blonanserin on PCP-induced cognitive impairment is associated with indirect functional stimulation of the dopamine-D1-PKA-NMDA receptor pathway following augmentation of dopaminergic neurotransmission due to inhibition of both dopamine-D3 and serotonin 5-HT2A receptors in the mPFC. PMID:25120077

The roles of NMDA receptor activation and nucleus reticularis gigantocellularis in the time-dependent changes in descending inhibition after inflammation.

PubMed

Terayama, R; Dubner, R; Ren, K

2002-05-01

Previous studies indicate that descending modulation of nociception is progressively increased following persistent inflammation. The present study was designed to further examine the role of supraspinal neurons in descending modulation following persistent inflammation. Constant levels of paw withdrawal (PW) and tail flick (TF) latencies to noxious heat stimuli were achieved in lightly anesthetized rats (pentobarbital sodium 3-10 mg/kg/h, i.v.). Electrical stimulation (ES, 0.1 ms, 100 Hz, 20-200 A) was delivered to the rostral ventromedial medulla (RVM), mainly the nucleus raphe magnus (NRM). ES produced intensity-dependent inhibition of PW and TF. Following a unilateral hindpaw inflammation produced by injection of complete Freund's adjuvant (CFA), ES-produced inhibition underwent time-dependent changes. There was an initial decrease at 3 h after inflammation and a subsequent increase after inflammation in the excitability of RVM neurons and the inhibition of nocifensive responses. These changes were most robust after stimulation of the inflamed paw although similar findings were seen on the non-inflamed paw and tail. The inflammation-induced dynamic changes in descending modulation appeared to be correlated with changes in the activation of the N-methyl--aspartate (NMDA) excitatory amino acid receptor. Microinjection of an NMDA receptor antagonist, AP5 (1 pmol), resulted in an increase in the current intensity required for inhibition of the PW and TF. The effect of AP5 was less at 3 h after inflammation and significantly greater at 11-24 h after inflammation. In a subsequent experiment, ES-produced inhibition of nocifensive responses after inflammation was examined following selective chemical lesions of the nuclei reticularis gigantocellularis (NGC). Compared to vehicle-injected animals, microinjection of a soma-selective excitotoxin, ibotenic acid, enhanced ES-produced inhibition at 3 h but not at 24 h after inflammation. We propose that these time course changes reflect dynamic alterations in concomitant descending facilitation and inhibition. At early time points, NMDA receptor and NGC activation enhance descending facilitation; as time progresses, the dose-response curve of NMDA shifts to the left and descending inhibition dominates and masks any descending facilitation.

Ventral tegmental ionotropic glutamate receptor stimulation of nucleus accumbens tonic dopamine efflux blunts hindbrain-evoked phasic neurotransmission: implications for dopamine dysregulation disorders.

PubMed

Tye, S J; Miller, A D; Blaha, C D

2013-11-12

Activation of glutamate receptors within the ventral tegmental area (VTA) stimulates extrasynaptic (basal) dopamine release in terminal regions, including the nucleus accumbens (NAc). Hindbrain inputs from the laterodorsal tegmental nucleus (LDT) are critical for elicitation of phasic VTA dopamine cell activity and consequent transient dopamine release. This study investigated the role of VTA ionotropic glutamate receptor (iGluR) stimulation on both basal and LDT electrical stimulation-evoked dopamine efflux in the NAc using in vivo chronoamperometry and fixed potential amperometry in combination with stearate-graphite paste and carbon fiber electrodes, respectively. Intra-VTA infusion of the iGluR agonists (±)-α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA; 1 μg/μl) or N-methyl-d-aspartic acid (NMDA; 2 μg/μl) enhanced basal NAc dopamine efflux. This iGluR-mediated potentiation of basal dopamine efflux was paralleled by an attenuation of LDT-evoked transient NAc dopamine efflux, suggesting that excitation of basal activity effectively inhibited the capacity of hindbrain afferents to elicit transient dopamine efflux. In line with this, post-NMDA infusion of the dopamine D2 autoreceptor (D2R) agonist quinpirole (1 μg/μl; intra-VTA) partially recovered NMDA-mediated attenuation of LDT-evoked NAc dopamine, while concurrently attenuating NMDA-mediated potentiation of basal dopamine efflux. Post-NMDA infusion of quinpirole (1 μg/μl) alone attenuated basal and LDT-evoked dopamine efflux. Taken together, these data reveal that hyperstimulation of basal dopamine transmission can stunt hindbrain burst-like stimulation-evoked dopamine efflux. Inhibitory autoreceptor mechanisms within the VTA help to partially recover the magnitude of phasic dopamine efflux, highlighting the importance of both iGluRs and D2 autoreceptors in maintaining the functional balance of tonic and phasic dopamine neurotransmission. Dysregulation of this balance may have important implications for disorders of dopamine dysregulation such as attention deficit hyperactivity disorder. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

Neuroprotective effects of vinpocetine and its major metabolite cis-apovincaminic acid on NMDA-induced neurotoxicity in a rat entorhinal cortex lesion model.

PubMed

Nyakas, Csaba; Felszeghy, Klára; Szabó, Róbert; Keijser, Jan N; Luiten, Paul G M; Szombathelyi, Zsolt; Tihanyi, Károly

2009-01-01

Vinpocetine (ethyl-apovincaminate, Cavinton), a synthetic derivative of the Vinca minor alkaloid vincamine, has been used now for decades for prevention and treatment of cerebrovascular diseases predisposing to development of dementia. Both vinpocetine and its main metabolite cis-apovincaminic acid (cAVA) exert a neuroprotective type of action. Bilateral N-methyl-D-aspartate (NMDA)-induced neurodegeneration in the entorhinal cortex of rat was used as a dementia model to confirm the neuroprotective action of these compounds in vivo. NMDA-lesioned rats were treated 60 min before lesion and throughout 3 postoperative days with a 10 mg/kg intraperitoneal dose of vinpocetine or cAVA. Behavioral tests started after termination of drug treatment and consisted of novel object recognition, social discrimination, and spontaneous alternation in a Y-maze, and spatial learning in the Morris water maze. At the end of behavioral testing brains were perfused with fixative and the size of the excitotoxic neuronal lesion and that of microglial activation around the lesion were assayed quantitatively on brain sections immunostained for neuron-specific nuclear protein (NeuN) and integrin CD11b, respectively. Entorhinal NMDA lesions impaired recognition of novel objects and the new social partner, and suppressed spontaneous alternation and spatial learning performance in the Morris maze. Both vinpocetine and cAVA effectively attenuated the behavioral deficits, and significantly decreased lesion size and the region of microglia activation. Both lesion-induced attention deficit and learning disabilities were markedly alleviated by vinpocetine and cAVA. The morphological findings corroborated the behavioral observations and indicated reduced lesion size and microglia activation especially after vinpocetine treatment which supports an in vivo neuroprotective mode of action of vinpocitine and a less potent action of cAVA.

An in vivo evaluation of the antiseizure activity and acute neurotoxicity of agmatine.

PubMed

Bence, Aimee K; Worthen, David R; Stables, James P; Crooks, Peter A

2003-02-01

Agmatine, an endogenous cationic amine, exerts a wide range of biological effects, including modulation of glutamate-activated N-methyl-D-aspartate (NMDA) receptor function in the central nervous system (CNS). Since glutamate and the NMDA receptor have been implicated in the initiation and spread of seizure activity, the capacity of agmatine to inhibit seizure spread was evaluated in vivo. Orally administered agmatine (30 mg/kg) protected against maximal electroshock seizure (MES)-induced seizure spread in rats as rapidly as 15 min and for as long as 6 h after administration. Inhibition of MES-induced seizure spread was also observed when agmatine was administered intraperitoneally. Agmatine's antiseizure activity did not appear to be dose-dependent. An in vivo neurotoxicity screen indicated that agmatine was devoid of any acute neurological toxicity at the doses tested. These preliminary data suggest that agmatine has promising anticonvulsant activity.

Does anesthetic additivity imply a similar molecular mechanism of anesthetic action at N-methyl-D-aspartate receptors?

PubMed

Brosnan, Robert J; Pham, Trung L

2011-03-01

Isoflurane and carbon dioxide (CO(2)) negatively modulate N-methyl-d-aspartate (NMDA) receptors, but via different mechanisms. Isoflurane is a competitive antagonist at the NMDA receptor glycine binding site, whereas CO(2) inhibits NMDA receptor current through extracellular acidification. Isoflurane and CO(2) exhibit additive minimum alveolar concentration effects in rats, but we hypothesized that they would not additively inhibit NMDA receptor currents in vitro because they act at different molecular sites. NMDA receptors were expressed in frog oocytes and studied using 2-electrode voltage clamp techniques. A glycine concentration response for NMDA was measured in the presence and absence of CO(2). Concentration-response curves for isoflurane, H(+), CO(2), and ketamine as a function of NMDA inhibition were measured, and a Hill equation was used to calculate the EC(50) for each compound. Binary drug combinations containing ½ EC(50) were additive if NMDA current inhibition was not statistically different from 50%. The ½ EC(50) binary drug combinations decreased the percentage baseline NMDA receptor current as follows (mean ± SD, n = 5 to 6 oocytes each): CO(2)+ H(+) (51% ± 5%), CO(2 )+ isoflurane (54% ± 5%), H(+) + isoflurane (51% ± 3%), CO(2)+ ketamine (67% ± 8%), and H(+) + ketamine (64% ± 2%). In contrast to our hypothesis, NMDA receptor inhibition by CO(2) and isoflurane is additive. Possibly, CO(2) acidification modulates a pH-sensitive loop on the NMDA receptor that in turn alters glycine binding affinity on the GluN1 subunit. However, ketamine plus either CO(2) or H(+) synergistically inhibits NMDA receptor currents. Drugs acting via different mechanisms can thus exhibit additive or synergistic receptor effects. Additivity may not robustly indicate commonality between molecular anesthetic mechanisms.

A family of photoswitchable NMDA receptors

PubMed Central

Berlin, Shai; Szobota, Stephanie; Reiner, Andreas; Carroll, Elizabeth C; Kienzler, Michael A; Guyon, Alice; Xiao, Tong; Trauner, Dirk; Isacoff, Ehud Y

2016-01-01

NMDA receptors, which regulate synaptic strength and are implicated in learning and memory, consist of several subtypes with distinct subunit compositions and functional properties. To enable spatiotemporally defined, rapid and reproducible manipulation of function of specific subtypes, we engineered a set of photoswitchable GluN subunits ('LiGluNs'). Photo-agonism of GluN2A or GluN2B elicits an excitatory drive to hippocampal neurons that can be shaped in time to mimic synaptic activation. Photo-agonism of GluN2A at single dendritic spines evokes spine-specific calcium elevation and expansion, the morphological correlate of LTP. Photo-antagonism of GluN2A alone, or in combination with photo-antagonism of GluN1a, reversibly blocks excitatory synaptic currents, prevents the induction of long-term potentiation and prevents spine expansion. In addition, photo-antagonism in vivo disrupts synaptic pruning of developing retino-tectal projections in larval zebrafish. By providing precise and rapidly reversible optical control of NMDA receptor subtypes, LiGluNs should help unravel the contribution of specific NMDA receptors to synaptic transmission, integration and plasticity. DOI: http://dx.doi.org/10.7554/eLife.12040.001 PMID:26929991

BDNF serum levels in schizophrenic patients during treatment augmentation with sarcosine (results of the PULSAR study).

PubMed

Strzelecki, Dominik; Kałużyńska, Olga; Wysokiński, Adam

2016-08-30

Finding a relationship between schizophrenia symptoms severity and initial level of BDNF and its changes during augmentation of antipsychotic treatment with sarcosine. 57 individuals with schizophrenia with predominantly negative symptoms completed a 6-month RCT prospective study. The patients received 2g of sarcosine (n=27) or placebo (n=30) daily. At the beginning, after 6 weeks and 6 months BDNF levels were measured. Severity of symptoms was assessed using the Positive and Negative Syndrome Scale (PANSS) and Calgary Depression Scale for Schizophrenia (CDSS). BDNF serum levels were stable after 6 weeks and 6 months in both groups. We noted improvement in negative symptoms, general psychopathology and total PANSS score in sarcosine group comparing to placebo, however there was no correlations between serum BDNF concentrations and PANSS scores in all assessments. Initial serum BDNF concentrations cannot be used as a predictor of the improvement resulting from adding sarcosine. Our results indicate that either BDNF is not involved in the NMDA-dependent mechanism of sarcosine action or global changes in BDNF concentrations induced by amino-acid cannot be detected in blood assessments. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Effects of Ethanol on Phosphorylation Site Mutants of Recombinant NMDA Receptors

PubMed Central

Xu, Minfu; Smothers, Corigan T.; Woodward, John J.

2010-01-01

N-methyl-D-aspartate (NMDA) receptors are ligand-gated ion channels activated by the neurotransmitter glutamate. These channels are highly expressed by brain neurons and are critically involved in excitatory synaptic transmission. Results from previous studies show that both native and recombinant NMDA receptors are inhibited by ethanol at concentrations associated with signs of behavioral impairment and intoxication. Given the important role that NMDA receptors play in synaptic transmission and brain function, it is important to understand the factors that regulate the ethanol inhibition of these receptors. One dynamic mechanism for regulating ethanol action may be via phosphorylation of NMDA subunits by serine-threonine and tyrosine kinases. Both NR1 and NR2 subunits contain multiple sites of phosphorylation and in the NR1 subunit, most of these are contained within the C1 domain, a carboxy-terminal cassette that is subject to alternative splicing. While results from our previous studies suggest that single phosphorylation sites do not greatly affect ethanol sensitivity of NMDA receptors, it is likely that in vivo, these subunits are phosphorylated at multiple sites by different kinases. In the present study, we constructed a series of NMDA receptor mutants at serine (S) or threonine (T) residues proposed to be sites of phosphorylation by PKA and various isoforms of PKC. Ethanol (100 mM) inhibited currents from wild-type NR1/2A and NR1/2B receptors expressed in HEK293 cells by approximately 25% and 30% respectively. This inhibition was not different in single site mutants expressing alanine (A) or aspartate/glutamate (D/E) at positions T879, S896 or T900. The mutant NR1(S890D) showed greater ethanol inhibition than NR1(890A) containing receptors although this was only observed when it was combined with the NR2A subunit. Ethanol inhibition was not altered by aspartate substitution at four serines (positions 889, 890, 896, 897) or when T879D was added to the four serine-substituted mutant. Ethanol inhibition was increased when T900E was added to the five serine/threonine substituted mutant but again this was selective for NR2A containing receptors. Together with previously published data, these findings suggest that modification of putative phosphorylation sites could contribute to the overall acute ethanol sensitivity of recombinant NMDA receptors. Supported by R37 AA009986. PMID:21163614

Threshold to N-methyl-D-aspartate-induced seizures in mice undergoing chronic nutritional magnesium deprivation is lowered in a way partly responsive to acute magnesium and antioxidant administrations.

PubMed

Maurois, Pierre; Pages, Nicole; Bac, Pierre; German-Fattal, Michèle; Agnani, Geneviève; Delplanque, Bernadette; Durlach, Jean; Poupaert, Jacques; Vamecq, Joseph

2009-02-01

Magnesium deficiency may be induced by a diet impoverished in magnesium. This nutritional deficit promotes chronic inflammatory and oxidative stresses, hyperexcitability and, in mice, susceptibility to audiogenic seizures. Potentiation by low-magnesium concentrations of the opening of N-methyl-D-aspartate (NMDA) receptor/calcium channel in in vitro and ex vivo studies, and responsiveness to magnesium of in vivo brain injury states are now well established. By contrast, little or no specific attention has been, however, paid to the in vivo NMDA receptor function/excitability in magnesium deficiency. The present work reports for the first time that, in mice undergoing chronic nutritional deprivation in magnesium (35 v. 930 parts per million for 27 d in OF1 mice), NMDA-induced seizure threshold is significantly decreased (38 % of normal values). The attenuation in the drop of NMDA seizure threshold (percentage of reversal) was 58 and 20 % upon acute intraperitoneal administrations of magnesium chloride hexahydrate (28 mg magnesium/kg) and the antioxidant ebselen (20 mg/kg), respectively. In nutritionally magnesium-deprived animals, audiogenic seizures are completely prevented by these compound doses. Taken as a whole, our data emphasise that chronic magnesium deprivation in mice is a nutritional in vivo model for a lowered NMDA receptor activation threshold. This nutritional model responds remarkably to acute magnesium supply and moderately to acute antioxidant administration.

NMDA antagonists exert distinct effects in experimental organophosphate or carbamate poisoning in mice

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

Dekundy, Andrzej; Kaminski, Rafal M.; Zielinska, Elzbieta

2007-03-15

Organophosphate (OP) and carbamate acetylcholinesterase (AChE) inhibitors produce seizures and lethality in mammals. Anticonvulsant and neuroprotective properties of N-methyl-D-aspartate (NMDA) antagonists encourage the investigation of their effects in AChE inhibitor-induced poisonings. In the present study, the effects of dizocilpine (MK-801, 1 mg/kg) or 3-((RS)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP, 10 mg/kg), alone or combined with muscarinic antagonist atropine (1.8 mg/kg), on convulsant and lethal properties of an OP pesticide dichlorvos or a carbamate drug physostigmine, were studied in mice. Both dichlorvos and physostigmine induced dose-dependent seizure activity and lethality. Atropine did not prevent the occurrence of convulsions but decreased the lethal effects ofmore » both dichlorvos and physostigmine. MK-801 or CPP blocked or attenuated, respectively, dichlorvos-induced convulsions. Contrariwise, NMDA antagonists had no effect in physostigmine-induced seizures or lethality produced by dichlorvos or physostigmine. Concurrent pretreatment with atropine and either MK-801 or CPP blocked or alleviated seizures produced by dichlorvos, but not by physostigmine. Both MK-801 and CPP co-administered with atropine enhanced its antilethal effects in both dichlorvos and physostigmine poisoning. In both saline- and AChE inhibitor-treated mice, no interaction of the investigated antidotes with brain cholinesterase was found. The data indicate that both muscarinic ACh and NMDA receptor-mediated mechanisms contribute to the acute toxicity of AChE inhibitors, and NMDA receptors seem critical to OP-induced seizures.« less

Adult forebrain NMDA receptors gate social motivation and social memory.

PubMed

Jacobs, Stephanie; Tsien, Joe Z

2017-02-01

Motivation to engage in social interaction is critical to ensure normal social behaviors, whereas dysregulation in social motivation can contribute to psychiatric diseases such as schizophrenia, autism, social anxiety disorders and post-traumatic stress disorder (PTSD). While dopamine is well known to regulate motivation, its downstream targets are poorly understood. Given the fact that the dopamine 1 (D1) receptors are often physically coupled with the NMDA receptors, we hypothesize that the NMDA receptor activity in the adult forebrain principal neurons are crucial not only for learning and memory, but also for the proper gating of social motivation. Here, we tested this hypothesis by examining sociability and social memory in inducible forebrain-specific NR1 knockout mice. These mice are ideal for exploring the role of the NR1 subunit in social behavior because the NR1 subunit can be selectively knocked out after the critical developmental period, in which NR1 is required for normal development. We found that the inducible deletion of the NMDA receptors prior to behavioral assays impaired, not only object and social recognition memory tests, but also resulted in profound deficits in social motivation. Mice with ablated NR1 subunits in the forebrain demonstrated significant decreases in sociability compared to their wild type counterparts. These results suggest that in addition to its crucial role in learning and memory, the NMDA receptors in the adult forebrain principal neurons gate social motivation, independent of neuronal development. Copyright © 2016 Elsevier Inc. All rights reserved.

EVALUATING THE NMDA-GLUTAMATE RECEPTOR AS A SITE OF ACTION FOR TOLUENE, IN VIVO

EPA Science Inventory

In vitro, toluene disrupts the function of NMDA-glutamate receptors, indicating that effects on NMDA receptor function may contribute to toluene neurotoxicity. NMDA-glutamate receptors are widely present in the visual system and contribute to pattern-elicited visual evoked potent...

The Neurogenesis Actuator and NR2B/NMDA Receptor Antagonist Ro25-6981 Consistently Improves Spatial Memory Retraining Via Brain Region-Specific Gene Expression.

PubMed

Gruden, Marina A; Ratmirov, Alexander M; Storozheva, Zinaida I; Solovieva, Olga A; Sherstnev, Vladimir V; Sewell, Robert D E

2018-05-22

NR2B-containing NMDA (NR2B/NMDA) receptors are important in controlling neurogenesis and are involved in generating spatial memory. Ro25-6981 is a selective antagonist at these receptors and actuates neurogenesis and spatial memory. Inter-structural neuroanatomical profiles of gene expression regulating adult neurogenesis and neuroapoptosis require examination in the context of memory retrieval and reversal learning. The aim was to investigate spatial memory retrieval and reversal learning in relation to gene expression-linked neurogenetic processes following blockade of NR2B/NMDA receptors by Ro25-6981. Rats were trained in Morris water maze (MWM) platform location for 5 days. Ro25-6981 was administered (protocol days 6-7) followed by retraining (days 15-18 or 29-32). Platform location was tested (on days 19 or 33) then post-mortem brain tissue sampling (on days 20 or 34). The expression of three genes known to regulate cell proliferation (S100a6), differentiation (Ascl1), and apoptosis (Casp-3) were concomitantly evaluated in the hippocampus, prefrontal cortex, and cerebellum in relation to the MWM performance protocol. Following initial training, Ro25-6981 enhanced visuospatial memory retrieval performance during further retraining (protocol days 29-32) but did not influence visuospatial reversal learning (day 33). Hippocampal Ascl1 and Casp-3 expressions were correspondingly increased and decreased while cerebellar S100a6 and Casp-3 activities were decreased and increased respectively 27 days after Ro25-6981 treatment. Chronological analysis indicated a possible involvement of new mature neurons in the reconfiguration of memory processes. This was attended by behavioral/gene correlations which revealed direct links between spatial memory retrieval enhancement and modified gene activity induced by NR2B/NMDA receptor blockade and upregulation.

Pharmacological evidence for the involvement of the NMDA receptor and nitric oxide pathway in the antidepressant-like effect of lamotrigine in the mouse forced swimming test.

PubMed

Ostadhadi, Sattar; Ahangari, Mohammad; Nikoui, Vahid; Norouzi-Javidan, Abbas; Zolfaghari, Samira; Jazaeri, Farahnaz; Chamanara, Mohsen; Akbarian, Reyhaneh; Dehpour, Ahmad-Reza

2016-08-01

Lamotrigine is an anticonvulsant agent that shows clinical antidepressant properties. The aim of the present study was to investigate the involvement of N-methyl-d-aspartate (NMDA) receptors and nitric oxide-cyclic guanosine monophosphate (NO-cGMP) synthesis in possible antidepressant-like effect of lamotrigine in forced swimming test (FST) in mice. Intraperitoneal administration of lamotrigine (10mg/kg) decreased the immobility time in the FST (P<0.01) without any effect on locomotor activity in the open-field test (OFT), while higher dose of lamotrigine (30mg/kg) reduced the immobility time in the FST (P<0.001) as well as the number of crossings in the OFT. Pretreatment of animals with NMDA (75mg/kg), l-arginine (750mg/kg, a substrate for nitric oxide synthase [NOS]) or sildenafil (5mg/kg, a phosphodiesterase [PDE] 5 inhibitor) reversed the antidepressant-like effect of lamotrigine (10mg/kg) in the FST. Injection of l-nitroarginine methyl ester (l-NAME, 10mg/kg, a non-specific NOS inhibitor), 7-nitroindazole (30mg/kg, a neuronal NOS inhibitor), methylene blue (20mg/kg, an inhibitor of both NOS and soluble guanylate cyclase [sGC]), or MK-801 (0.05mg/kg), ketamine (1mg/kg), and magnesium sulfate (10mg/kg) as NMDA receptor antagonists in combination with a sub-effective dose of lamotrigine (5mg/kg) diminished the immobility time of animals in the FST compared with either drug alone. None of the drugs produced significant effects on the locomotor activity in the OFT. Based on our findings, it is suggested that the antidepressant-like effect of lamotrigine might mediated through inhibition of either NMDA receptors or NO-cGMP synthesis. Copyright © 2016. Published by Elsevier Masson SAS.

The use of antioxidants to prevent glutamate-induced derangement of calcium ion metabolism in rat cerebral cortex synaptosomes.

PubMed

Avrova, N F; Shestak, K I; Zakharova, I O; Sokolova, T V; Tyurina, Y Y; Tyurin, V A

2000-01-01

Glutamate is shown to induce increases in intracellular Ca2+ concentrations ([Ca2+]i), increases in 45Ca2+ influx, decreases in the activity of Na+,K+-ATPase activity, and activation of the Na+/Ca2+ exchanger in rat cerebral cortex synaptosomes. NMDA receptor antagonists virtually prevented these effects. Preincubation of synaptosomes with alpha-tocopherol, superoxide dismutase, and ganglioside GM1 normalized [Ca2+]i, 45Ca2+ influx, and Na+,K+-ATPase activity in rat cerebral cortex synaptosomes exposed to glutamate. Glutamate and GM1 activated the Na+/K+ exchanger, and their effects were additive. Calcium ions entering cerebral cortex nerve cells via NMDA receptors during exposure to high glutamate concentrations appeared to be only the trigger for the processes activating free-radical reactions. Activation of these reactions led to increases in Ca2+ influx into cells, decreases in Na+,K+-ATPase activity, and significant increases in [Ca2+]i, though this could be prevented by antioxidants and gangliosides.

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.

Modulating the Intrinsic Disorder in the Cytoplasmic Domain Alters the Biological Activity of the N-Methyl-d-aspartate-sensitive Glutamate Receptor*

PubMed Central

Choi, Ucheor B.; Kazi, Rashek; Stenzoski, Natalie; Wollmuth, Lonnie P.; Uversky, Vladimir N.; Bowen, Mark E.

2013-01-01

The NMDA-sensitive glutamate receptor is a ligand-gated ion channel that mediates excitatory synaptic transmission in the nervous system. Extracellular zinc allosterically regulates the NMDA receptor by binding to the extracellular N-terminal domain, which inhibits channel gating. Phosphorylation of the intrinsically disordered intracellular C-terminal domain alleviates inhibition by extracellular zinc. The mechanism for this functional effect is largely unknown. Proline is a hallmark of intrinsic disorder, so we used proline mutagenesis to modulate disorder in the cytoplasmic domain. Proline depletion selectively uncoupled zinc inhibition with little effect on receptor biogenesis, surface trafficking, or ligand-activated gating. Proline depletion also reduced the affinity for a PDZ domain involved in synaptic trafficking and affected small molecule binding. To understand the origin of these phenomena, we used single molecule fluorescence and ensemble biophysical methods to characterize the structural effects of proline mutagenesis. Proline depletion did not eliminate intrinsic disorder, but the underlying conformational dynamics were changed. Thus, we altered the form of intrinsic disorder, which appears sufficient to affect the biological activity. These findings suggest that conformational dynamics within the intrinsically disordered cytoplasmic domain are important for the allosteric regulation of NMDA receptor gating. PMID:23782697

Cdk5 regulates PSD-95 ubiquitination in neurons

PubMed Central

Bianchetta, Michael J.; Lam, TuKiet T.; Jones, Stephen N.; Morabito, Maria A.

2011-01-01

The kinase Cdk5 and its activator p35 have been implicated in drug addiction, neurodegenerative diseases such as Alzheimer’s, learning and memory, and synapse maturation and plasticity. However the molecular mechanisms by which Cdk5 regulates synaptic plasticity are still unclear. PSD-95 is a major postsynaptic scaffolding protein of glutamatergic synapses that regulates synaptic strength and plasticity. PSD-95 is ubiquitinated by the Ubiquitin E3 Ligase Mdm2, and rapid and transient PSD-95 ubiquitination has been implicated in NMDA receptor-induced AMPA receptor endocytosis. Here we demonstrate that genetic or pharmacological reduction of Cdk5 activity increases the interaction of Mdm2 with PSD-95 and enhances PSD-95 ubiquitination without affecting PSD-95 protein levels in vivo in mice, suggesting a non-proteolytic function of ubiquitinated PSD-95 at synapses. We show that PSD-95 ubiquitination correlates with increased interaction with β-adaptin, a subunit of the clathrin adaptor protein complex AP-2. This interaction is increased by genetic reduction of Cdk5 activity or NMDA receptor stimulation and is dependent on Mdm2. Together these results support a function for Cdk5 in regulating PSD-95 ubiqutination and its interaction with AP-2 and suggest a mechanism by which PSD-95 may regulate NMDA receptor-induced AMPA receptor endocytosis. PMID:21849563

Neonatal (+)-methamphetamine exposure in rats alters adult locomotor responses to dopamine D1 and D2 agonists and to a glutamate NMDA receptor antagonist, but not to serotonin agonists

PubMed Central

Graham, Devon L.; Amos-Kroohs, Robyn M.; Braun, Amanda A.; Grace, Curtis E.; Schaefer, Tori L.; Skelton, Matthew R.; Williams, Michael T.; Vorhees, Charles V.

2015-01-01

Neonatal exposure to (+)-methamphetamine (Meth) results in long-term behavioural abnormalities but its developmental mechanisms are unknown. In a series of experiments, rats were treated from post-natal days (PD) 11–20 (stage that approximates human development from the second to third trimester) with Meth or saline and assessed using locomotor activity as the readout following pharmacological challenge doses with dopamine, serotonin and glutamate agonists or antagonists during adulthood. Exposure to Meth early in life resulted in an exaggerated adult locomotor hyperactivity response to the dopamine D1 agonist SKF-82958 at multiple doses, a high dose only under-response activating effect of the D2 agonist quinpirole, and an exaggerated under-response to the activating effect of the N-methyl-D-aspartic acid (NMDA) receptor antagonist, MK-801. No change in locomotor response was seen following challenge with the 5-HT releaser p-chloroamphetamine or the 5-HT2/3 receptor agonist, quipazine. These are the first data to show that PD 11-20 Meth exposure induces long-lasting alterations to dopamine D1, D2 and glutamate NMDA receptor function and may suggest how developmental Meth exposure leads to many of its long-term adverse effects. PMID:22391043

Structural Analogues of Selfotel.

PubMed

Dziuganowska, Zofia A; Ślepokura, Katarzyna; Volle, Jean-Noël; Virieux, David; Pirat, Jean-Luc; Kafarski, Paweł

2016-06-17

A small library of phosphonopiperidylcarboxylic acids, analogues of NMDA antagonist selfotel (CGS 19755), was synthesized. First, the series of aromatic esters was obtained via a palladium-catalyzed cross-coupling reaction (Hirao coupling) of dialkyl phosphites with bromopyridinecarboxylates, followed by their hydrolysis. Then, hydrogenation of the resulting phosphonopyridylcarboxylic acids over PtO2 yielded the desired phosphonopiperidylcarboxylic acids. NMR studies indicated that the hydrogenation reaction proceeds predominantly by cis addition. Several compounds were obtained as monocrystal structures. Preliminary biological studies performed on cultures of neurons suggest that the obtained compounds possess promising activity toward NMDA receptors.

Neonatal olfactory bulbectomy enhances locomotor activity, exploratory behavior and binding of NMDA receptors in pre-pubertal rats.

PubMed

Flores, G; Ibañez-Sandoval, O; Silva-Gómez, A B; Camacho-Abrego, I; Rodríguez-Moreno, A; Morales-Medina, J C

2014-02-14

In this study, we investigated the effect of neonatal olfactory bulbectomy (nOBX) on behavioral paradigms related to olfaction such as exploratory behavior, locomotor activity in a novel environment and social interaction. We also studied the effect of nOBX on the activity of the N-methyl-d-aspartate (NMDA) subtype of glutamate receptors during development. The behavioral effects of nOBX (postnatal day 7, PD7) were investigated in pre- (PD30) and post-pubertal (PD60) Wistar rats. NMDA receptor activity was measured with [(125)I]MK-801 in the brain regions associated with the olfactory circuitry. A significant increase in the novelty-induced locomotion was seen in the pre-pubertal nOBX rats. Although the locomotor effect was less marked than in pre-pubertal rats, the nOBX rats tested post-pubertally failed to habituate to the novel situation as quickly as the sham- and normal- controls. Pre-pubertally, the head-dipping behavior was enhanced in nOBX rats compared with sham-operated and normal controls, while normal exploratory behavior was observed between groups in adulthood. In contrast, social interaction was increased in post-pubertal animals that underwent nOBX. Both pre- and post-pubertal nOBX rats recovered olfaction. Interestingly, pre-pubertal rats showed a significant increase in the [(125)I]MK-801 binding in the piriform cortex, dorsal hippocampus, inner and outer layers of the frontal cortex and outer layer of the cingulate cortex. At post-pubertal age, no significant differences in [(125)I]MK-801 binding were observed between groups at any of the brain regions analyzed. These results suggest that nOBX produces pre-pubertal behavioral disturbances and NMDA receptor changes that are transitory with recovery of olfaction early in adulthood. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

Single-Cell Resolution Imaging of Retinal Ganglion Cell Apoptosis In Vivo Using a Cell-Penetrating Caspase-Activatable Peptide Probe

PubMed Central

Qiu, Xudong; Johnson, James R.; Wilson, Bradley S.; Gammon, Seth T.; Piwnica-Worms, David; Barnett, Edward M.

2014-01-01

Peptide probes for imaging retinal ganglion cell (RGC) apoptosis consist of a cell-penetrating peptide targeting moiety and a fluorophore-quencher pair flanking an effector caspase consensus sequence. Using ex vivo fluorescence imaging, we previously validated the capacity of these probes to identify apoptotic RGCs in cell culture and in an in vivo rat model of N-methyl- D-aspartate (NMDA)-induced neurotoxicity. Herein, using TcapQ488, a new probe designed and synthesized for compatibility with clinically-relevant imaging instruments, and real time imaging of a live rat RGC degeneration model, we fully characterized time- and dose-dependent probe activation, signal-to-noise ratios, and probe safety profiles in vivo. Adult rats received intravitreal injections of four NMDA concentrations followed by varying TcapQ488 doses. Fluorescence fundus imaging was performed sequentially in vivo using a confocal scanning laser ophthalmoscope and individual RGCs displaying activated probe were counted and analyzed. Rats also underwent electroretinography following intravitreal injection of probe. In vivo fluorescence fundus imaging revealed distinct single-cell probe activation as an indicator of RGC apoptosis induced by intravitreal NMDA injection that corresponded to the identical cells observed in retinal flat mounts of the same eye. Peak activation of probe in vivo was detected 12 hours post probe injection. Detectable fluorescent RGCs increased with increasing NMDA concentration; sensitivity of detection generally increased with increasing TcapQ488 dose until saturating at 0.387 nmol. Electroretinography following intravitreal injections of TcapQ488 showed no significant difference compared with control injections. We optimized the signal-to-noise ratio of a caspase-activatable cell penetrating peptide probe for quantitative non-invasive detection of RGC apoptosis in vivo. Full characterization of probe performance in this setting creates an important in vivo imaging standard for functional evaluation of future probe analogues and provides a basis for extending this strategy into glaucoma-specific animal models. PMID:24586415

Anesthetics inhibit extracellular signal-regulated Kinase1/2 phosphorylation via NMDA receptor, phospholipase C and protein kinase C in mouse hippocampal slices.

PubMed

Haiying, Gao; Mingjie, Han; Lingyu, Zhang; Qingxiang, Wang; Haisong, Wang; Bingxi, Zhang

2017-02-01

Extracellular signal-regulated kinase 1/2 (ERK1/2) has been implicated in learning and memory; however, whether intravenous anesthetics modulate ERK1/2 remains unknown. The aim of this study was to examine the effect of several intravenous anesthetics on the phosphorylation of ERK1/2 in the hippocampus of adult mice. Western blotting was used to examine cellular levels of phosphorylated and unphosphorylated ERK1/2 in mouse hippocampus slices, which were incubated with or without anesthetics including propofol, etomidate, ketamine and midazolam, a protein kinase C (PKC) activator or inhibitor, or phospholipase C (PLC) activator or inhibitor. Propofol, etomidate, ketamine and midazolam reduced phosphorylation of ERK1/2 in a time-dependent manner. Washing out propofol after 5 min increased ERK1/2 phosphorylation. The anesthetic-induced depression of ERK1/2 phosphorylation was blocked by 0.1 μM phorbol-12-myristate 13-acetate (an activator of PKC), 50 μM U73122 (an inhibitor of PLC). The anesthetic-induced depression of ERK1 phosphorylation was blocked by 1 mMN-methyl-d-aspartate (NMDA). Whereas 100 μM chelerythrine (an inhibitor of PKC) and 100 μM carbachol (an activator of PLC) and 20 μM PD-98059 (an inhibitor of MEK) had additive effects on propofol-induced inhibition of ERK1/2 phosphorylation. In contrast, 10 μM MK801 (a NMDA receptor antagonist) did not block anesthetic-induced inhibition of ERK1/2 phosphorylation. Intravenous anesthetics markedly decreased phosphorylation of ERK1/2 in mouse hippocampal slices, most likely via the NMDA receptor, and PLC- and PKC-dependent pathways. Thus, ERK1/2 represents a target for anesthetics in the brain. Copyright © 2016. Published by Elsevier Ltd.

Non-conventional apoptotic response to ionising radiation mediated by N-methyl D-aspartate receptors in immature neuronal cells

PubMed Central

SAMARI, NADA; DE SAINT-GEORGES, LOUIS; PANI, GIUSEPPE; BAATOUT, SARAH; LEYNS, LUC; BENOTMANE, MOHAMMED ABDERRAFI

2013-01-01

During cortical development, N-methyl D-aspartate (NMDA) receptors are highly involved in neuronal maturation and synapse establishment. Their implication in the phenomenon of excitotoxicity has been extensively described in several neurodegenerative diseases due to the permissive entry of Ca2+ ions and massive accumulation in the intracellular compartment, which is highly toxic to cells. Ionising radiation is also a source of stress to the cells, particularly immature neurons. Their capacity to induce cell death has been described for various cell types either by directly damaging the DNA or indirectly through the generation of reactive oxygen species responsible for the activation of a battery of stress response effectors leading in certain cases, to cell death. In this study, in order to determine whether a link exists between NMDA receptors-mediated excitotoxicity and radiation-induced cell death, we evaluated radiation-induced cell death in vitro and in vivo in maturing neurons during the fetal period. Cell death induction was assessed by TUNEL, caspase-3 activity and DNA ladder assays, with or without the administration of dizocilpine (MK-801), a non-competitive NMDA receptor antagonist which blocks neuronal Ca2+ influx. To further investigate the possible involvement of Ca2+-dependent enzyme activation, known to occur at high Ca2+ concentrations, we examined the protective effect of a calpain inhibitor on cell death induced by radiation. Doses ranging from 0.2 to 0.6 Gy of X-rays elicited a clear apoptotic response that was prevented by the injection of dizocilpine (MK-801) or calpain inhibitor. These data demonstrate the involvement of NMDA receptors in radiation-induced neuronal death by the activation of downstream effectors, including calpain-related pathways. An increased apoptotic process elicited by radiation, occurring independently of the normal developmental scheme, may eliminate post-mitotic but immature neuronal cells and deeply impair the establishment of the neuronal network, which in the case of cortical development is critical for cognitive capacities. PMID:23338045

CXCL13 regulates the trafficking of GluN2B-containing NMDA receptor via IL-17 in the development of remifentanil-induced hyperalgesia in rats.

PubMed

Zhu, M; Yuan, S T; Yu, W L; Jia, L L; Sun, Y

2017-05-01

This study aimed to investigate whether CXCL13 modulated the trafficking of NMDA receptor via interleukin (IL)-17 in a rat model of remifentanil-induced hyperalgesia (RIH).Although chemokines are crucial regulators of neuroinflammation, spinal N-methyl-d-aspartate (NMDA) receptor activation, and development of hypernociceptive process, little is known about specific pathogenesis and effective treatment. Inflammatory mediators are required for excitatory synaptic transmission in pathologic pain. A neutralizing antibody against CXCL13 (anti-CXCL13), antiserum against IL-17 (anti-IL-17), and recombinant CXCL13 and IL-17 were administered intrathecally to explore the roles of CXCL13, IL-17, and NMDA receptor, as well as the prevention of hyperalgesia. Paw withdrawal threshold and paw withdrawal latency were employed to record mechanical allodynia and thermal hyperalgesia. Reverse transcriptase quantitative polymerase chain reaction was used to evaluate the levels of CXCL13/CXCR5 and IL-17/IL-17RA in the spinal dorsal horn. The trafficking of spinal GluN2B-containing NMDA receptor was assessed by Western blot after nociceptive testing. This study found mechanical allodynia and thermal hyperalgesia with a remarkable increase in the expression of spinal CXCL13/CXCR5 and IL-17/IL-17RA and trafficking of GluN2B-containing NMDA receptor after remifentanil exposure. Behavioral RIH and elevated GluN2B trafficking were dampened by intrathecal anti-CXCL13 and anti-IL-17, respectively. The delivery of exogenous CXCL13 dose-dependently generated a rapid nociceptive hypersensitivity in naïve rats, which was prevented by coadministering anti-IL-17. CXCL13-induced IL-17RA overproduction and GluN2B trafficking were reversed by anti-IL-17 treatment. GluN2B antagonist also blocked CXCL13, and IL-17 directly induced hyperalgesia. This study highlighted the contribution of IL-17 pathway in the trafficking of CXCL13-induced GluN2B-containing NMDA receptor in the pathogenesis of RIH. Copyright © 2017 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.

Pulmonary stretch receptor afferents activate excitatory amino acid receptors in the nucleus tractus solitarii in rats.

PubMed

Bonham, A C; Coles, S K; McCrimmon, D R

1993-05-01

1. The goal of the present study was to identify potential neurotransmitter candidates in the Breuer-Hering (BH) reflex pathway, specifically at synapses between the primary afferents and probable second-order neurones (pump cells) within the nucleus tractus solitarii (NTS). We hypothesized that if activation of specific receptors in the NTS is required for production of the BH reflex, then (1) injection of the receptor agonist(s) would mimic the reflex response (apnoea), (2) injection of appropriate antagonists would impair the apnoea produced by either lung inflation or agonist injection, and (3) second-order neurones in the pathway would be excited by either lung inflation or agonists while antagonists would prevent the response to either. 2. Studies were carried out either in spontaneously breathing or in paralysed, thoracotomized and ventilated rats in which either diaphragm EMG or phrenic nerve activity, expired CO2 concentration and arterial pressure were continuously monitored. The BH reflex was physiologically activated by inflating the lungs. 3. Pressure injections (0.03-15 pmol) of selective excitatory amino acid (EAA) receptor agonists, quisqualic acid (Quis) and N-methyl-D-aspartic acid (NMDA) into an area of the NTS shown previously to contain neurones required for production of the BH reflex produced dose-dependent apnoeas that mimicked the response to lung inflation. Injection of substance P (0.03-4 pmol) did not alter baseline respiratory pattern. 4. Injections of the EAA antagonists, kynurenic acid (Kyn; 0.6-240 pmol), 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX) or 6,7-dinitroquinoxaline-2,3-dione (DNQX) into the BH region of the NTS reversibly impaired the apnoea produced by lung inflation. All three antagonists reduced or abolished the apnoeas resulting from injection of Quis or NMDA, and slowed baseline respiratory frequency. In contrast, injections of the highly selective NMDA receptor antagonist, D-2-amino-5-phosphonovaleric acids (AP5), in doses sufficient to block the apnoeic response to NMDA, neither altered the reflex apnoea evoked by lung inflation nor the baseline respiratory pattern. 5. Pump cells located within the BH region were excited by pressure injections of the broad spectrum EAA agonist, DL-homocysteic acid (DLH). Kyn reversibly blocked the excitation of pump cells in response to either lung inflation or DLH injection. 6. These findings suggest that EAAs mediate primary afferent excitation of second-order neurones in the Breuer-Hering reflex pathway, primarily through the activation of non-NMDA EAA receptor subtypes.

Non-apoptotic function of BAD and BAX in long-term depression of synaptic transmission

PubMed Central

Jiao, Song; Li, Zheng

2011-01-01

Summary It has recently been found that caspases not only function in apoptosis, but are also crucial for non-apoptotic processes such as NMDA receptor-dependent long-term depression (LTD) of synaptic transmission. It remains unknown, however, how caspases are activated and how neurons escape death in LTD. Here we show that caspase-3 is activated by the BAD-BAX cascade for LTD induction. This cascade is required specifically for NMDA receptor-dependent LTD but not for mGluR-LTD, and its activation is sufficient to induce synaptic depression. In contrast to apoptosis, however, BAD is activated only moderately and transiently and BAX is not translocated to mitochondria, resulting in only modest caspase-3 activation. We further demonstrate that the intensity and duration of caspase-3 activation determin whether it leads to cell death or LTD, thus fine-tuning of caspase-3 activation is critical in distinguishing between these two pathways. PMID:21609830

Involvement of CRF but not NPY in the anxiety regulation via NMDA receptors.

PubMed

Wierońska, Joanna M; Szewczyk, Bernadeta; Pałucha, Agnieszka; Brański, Piotr; Smiałowska, Maria

2003-01-01

The study attempts to evaluate whether neuropeptide Y (NPY) and corticotropin-releasing factor (CRF) are involved in anxiogenic and anxiolytic reactions induced by NMDA receptor ligands. The animals were given MK-801 (1 mg/kg, ip), a non-competitive NMDA-receptor antagonist, which acts as anxiolytic agent, or NMDA (15 mg/kg, ip), which has an anxiogenic effect. The anxiogenic or anxiolytic actions of these compounds were evaluated in the plus-maze test. The animals, which were given MK-801, were administered BIBO 3304 (130 ng/0.5 microl/site) intraamygdalarly and the animals which were given NMDA were administered alpha-helical CRF (500 ng/0.5 microl/site). BIBO 3304 did not attenuate MK-801-induced anxiolysis and alpha-helical CRF abolished NMDA-induced anxiogenesis. Our results show that anxiogenic effect of NMDA is mediated via CRF1 receptors and anxiolytic action of MK-801 is not dependent on Y1 receptors.

Large variability in synaptic N-methyl-D-aspartate receptor density on interneurons and a comparison with pyramidal-cell spines in the rat hippocampus.

PubMed

Nyíri, G; Stephenson, F A; Freund, T F; Somogyi, P

2003-01-01

Pyramidal cells receive input from several types of GABA-releasing interneurons and innervate them reciprocally. Glutamatergic activation of interneurons involves both alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) type glutamate receptors expressed in type I synapses, mostly on their dendritic shafts. On average, the synaptic AMPA receptor content is several times higher on interneurons than in the spines of pyramidal cells. To compare the NMDA receptor content of synapses, we used a quantitative postembedding immunogold technique on serial electron microscopic sections, and analysed the synapses on interneuron dendrites and pyramidal cell spines in the CA1 area. Because all NMDA receptors contain the obligatory NR1 subunit, receptor localisation was carried out using antibodies recognising all splice variants of the NR1 subunit. Four populations of synapse were examined: i). on spines of pyramidal cells in stratum (str.) radiatum and str. oriens; ii). on parvalbumin-positive interneuronal dendritic shafts in str. radiatum; iii). on randomly found dendritic shafts in str. oriens and iv). on somatostatin-positive interneuronal dendritic shafts and somata in str. oriens. On average, the size of the synapses on spines was about half of those on interneurons. The four populations of synapse significantly differed in labelling for the NR1 subunit. The median density of NR1 subunit labelling was highest on pyramidal cell spines. It was lowest in the synapses on parvalbumin-positive dendrites in str. radiatum, where more than half of these synapses were immunonegative. In str. oriens, synapses on interneurons had a high variability of receptor content; some dendrites were similar to those in str. radiatum, including the proximal synapses of somatostatin-positive cells, whereas others had immunoreactivity for the NR1 subunit similar to or higher than synapses on pyramidal cell spines. These results show that synaptic NMDA receptor density differs between pyramidal cells and interneurons. Some interneurons may have a high NMDA receptor content, whereas others, like some parvalbumin-expressing cells, a particularly low synaptic NMDA receptor content. Consequently, fast glutamatergic activation of interneurons is expected to show cell type-specific time course and state-dependent dynamics.

[The antioxidant prevention of disorders in calcium ion metabolism under the action of glutamate on the synaptosomes of the rat cerebral cortex].

PubMed

Avrova, N F; Shestak, K I; Zakharova, I O; Sokolova, T V; Tiurina, Iu Iu; Tiurin, V A

1999-04-01

An increase of intracellular calcium ion concentration and of the 45Ca2+ entry, a decrease in Na+,K(+)-ATPase activity, and activation of Na+/Ca2+ exchange were shown to be initiated by glutamate in the rat brain cortex synaptosomes. These effects could be prevented with antagonists and blocking agents of the NMDA receptors. Pre-incubation of the synaptosomes with alpha-tocopherol, superoxide dismutase, and ganglioside GM1 was shown to normalise [45Ca2+], the rate of 45Ca2+ entry, and the activity of Na+,K(+)-ATPase in the synaptosomes. The data obtained suggest that calcium ions entering the brain cortex neurones via the NMDA receptors in presence of excessive glutamate, trigger activation of free radical reactions damaging the neurones in ischemia, cerebral lesions, and other pathological conditions.

Vitamin C modulates glutamate transport and NMDA receptor function in the retina.

PubMed

Domith, Ivan; Socodato, Renato; Portugal, Camila C; Munis, Andressa F; Duarte-Silva, Aline T; Paes-de-Carvalho, Roberto

2018-02-01

Vitamin C (in the reduced form ascorbate or in the oxidized form dehydroascorbate) is implicated in signaling events throughout the central nervous system (CNS). In the retina, a high-affinity transport system for ascorbate has been described and glutamatergic signaling has been reported to control ascorbate release. Here, we investigated the modulatory role played by vitamin C upon glutamate uptake and N-methyl-d-aspartate (NMDA) receptor activation in cultured retinal cells or in intact retinal tissue using biochemical and imaging techniques. We show that both forms of vitamin C, ascorbate or dehydroascorbate, promote an accumulation of extracellular glutamate by a mechanism involving the inhibition of glutamate uptake. This inhibition correlates with the finding that ascorbate promotes a decrease in cell surface levels of the neuronal glutamate transporter excitatory amino acid transporter 3 in retinal neuronal cultures. Interestingly, vitamin C is prone to increase the activity of NMDA receptors but also promotes a decrease in glutamate-stimulated [ 3 H] MK801 binding and decreases cell membrane content of NMDA receptor glutamate ionotropic receptor subunit 1 (GluN1) subunits. Both compounds were also able to increase cAMP response element-binding protein phosphorylation in neuronal nuclei in a glutamate receptor and calcium/calmodulin kinase-dependent manner. Moreover, the effect of ascorbate is not blocked by sulfinpyrazone and then does not depend on its uptake by retinal cells. Overall, these data indicate a novel molecular and functional target for vitamin C impacting on glutamate signaling in retinal neurons. © 2017 International Society for Neurochemistry.

Human immunodeficiency virus-1 protein Tat induces excitotoxic loss of presynaptic terminals in hippocampal cultures.

PubMed

Shin, Angela H; Thayer, Stanley A

2013-05-01

Human immunodeficiency virus (HIV) infection of the CNS produces dendritic damage that correlates with cognitive decline in patients with HIV-associated neurocognitive disorders (HAND). HIV-induced neurotoxicity results in part from viral proteins shed from infected cells, including the HIV transactivator of transcription (Tat). We previously showed that Tat binds to the low density lipoprotein receptor-related protein (LRP), resulting in overactivation of NMDA receptors, activation of the ubiquitin-proteasome pathway, and subsequent loss of postsynaptic densities. Here, we show that Tat also induces a loss of presynaptic terminals. The number of presynaptic terminals was quantified using confocal imaging of synaptophysin fused to green fluorescent protein (Syn-GFP). Tat-induced loss of presynaptic terminals was secondary to excitatory postsynaptic mechanisms because treatment with an LRP antagonist or an NMDA receptor antagonist inhibited this loss. Treatment with nutlin-3, an E3 ligase inhibitor, prevented Tat-induced loss of presynaptic terminals. These data suggest that Tat-induced loss of presynaptic terminals is a consequence of excitotoxic postsynaptic activity. We previously found that ifenprodil, an NR2B subunit-selective NMDA receptor antagonist, induced recovery of postsynaptic densities. Here we show that Tat-induced loss of presynaptic terminals was reversed by ifenprodil treatment. Thus, Tat-induced loss of presynaptic terminals is reversible, and this recovery can be initiated by inhibiting a subset of postsynaptic NMDA receptors. Understanding the dynamics of synaptic changes in response to HIV infection of the CNS may lead to the design of improved pharmacotherapies for HAND patients. Copyright © 2012 Elsevier Inc. All rights reserved.

Effects of NMDA and non-NMDA ionotropic glutamate receptors in the medial preoptic area on body temperature in awake rats.

PubMed

Sengupta, Trina; Jaryal, Ashok Kumar; Mallick, Hruda Nanda

2016-10-01

Glutamate when microinjected at the medial preoptic area (mPOA) influences brain temperature (T br ) and body temperature (T b ) in rats. Glutamate and its various receptors are present at the mPOA. The aim of this study was to identify the contribution of each of the ionotropic glutamatergic receptors at the mPOA on changes in T br and T b in freely moving rats. Adult male Wistar rats (n=40) were implanted with bilateral guide cannula with indwelling styli above the mPOA. A telemetric transmitter was implanted at the peritoneum to record T b and locomotor activity (LMA). A precalibrated thermocouple wire implanted near the hypothalamus was used to assess T br . Specific agonist for each ionotropic glutamate receptor was microinjected into the mPOA and its effects on temperature and LMA were measured in the rats. The rats were also microinjected with the respective ionotropic receptor antagonists, 15min prior to the microinjection of each agonist. Amongst amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), N-methyl-d-aspartate (NMDA) and kainic acid, AMPA increased T b and LMA when injected at the mPOA. Specific antagonists for AMPA receptors was able to attenuate this increase (p<0.005). Pharmacological blockade of NMDA was able to lower T br only. Microinjection of kainic acid and its antagonist had no effect on the variables. The finding of the study suggests that activation of the AMPA receptors at the mPOA, leads to the rise in body temperature. Copyright © 2016 Elsevier Ltd. All rights reserved.

Properties of Contextual Memory Formed in the Absence of αCaMKII Autophosphorylation

PubMed Central

2011-01-01

The alpha-isoform of calcium/calmodulin-dependent kinase II (αCaMKII) is a major synaptic kinase that undergoes autophosphorylation after NMDA receptor activation, switching the kinase into a calcium-independent activity state. This αCaMKII autophosphorylation is essential for NMDA receptor-dependent long-term potentiation (LTP), induced by a single tetanus, in hippocampal area CA1 and in neocortex. Furthermore, the αCaMKII autophosphorylation is essential for contextual long-term memory (LTM) formation after a single training trial but not after a massed training session. Here, we show that in the absence of αCaMKII autophosphorylation contextual fear conditioning is hippocampus dependent and that multi-tetanus-dependent late-LTP cannot be induced in hippocampal area CA1. Furthermore, we show that in the absence of αCaMKII autophosphorylation contextual LTM persists for 30 days, the latest time point tested. Additionally, contextual, but not cued, LTM formation in the absence of αCaMKII autophosphorylation appears to be impaired in 18 month-old mice. Taken together, our findings suggest that αCaMKII autophosphorylation-independent plasticity in the hippocampus is sufficient for contextual LTM formation and that αCaMKII autophosphorylation may be important for delaying age-related impairments in hippocampal memory formation. Furthermore, they propose that NMDA receptor-dependent LTP in hippocampal area CA1 is essential for contextual LTM formation after a single trial but not after massed training. Finally, our results challenge the proposal that NMDA receptor-dependent LTP in neocortex is required for remote contextual LTM. PMID:21276220

Divergent cellular pathways of hippocampal memory consolidation and reconsolidation

PubMed Central

Lee, Jonathan L. C.; Hynds, Robert E.

2013-01-01

The reconsolidation of memories after their retrieval involves cellular mechanisms that recapitulate much of the initial consolidation process. However, we have previously demonstrated that there are independent cellular mechanisms of consolidation and reconsolidation in the dorsal hippocampus for contextual fear memories. Expression of BDNF was required for consolidation, while Zif268 expression was necessary for reconsolidation. Given the dichotomy between the obvious mechanistic similarity and notable dissociations between consolidation and reconsolidation, we sought to determine whether the separation at the level of gene expression reflected either parallel and independent upstream signalling pathways, or common upstream mechanisms that diverge by the level of transcriptional activation. Here we show that while consolidation and reconsolidation are commonly dependent upon NMDA receptor activation in the dorsal hippocampus there is a double dissociation between the effects of the MEK inhibitor U0126 and the IKK inhibitor sulfasalazine. Moreover, rescue experiments and western blot analyses show that there are functional NMDA receptor–ERK1–BDNF and NMDA receptor–IKKα–Zif268 pathways for consolidation and reconsolidation, respectively. Therefore, there are divergent pathways of hippocampal memory consolidation and reconsolidation, involving commonality at the cell surface, but separable downstream kinase cascades and transcriptional regulation. PMID:23197404

A redox-based mechanism for the neuroprotective and neurodestructive effects of nitric oxide and related nitroso-compounds.

PubMed

Lipton, S A; Choi, Y B; Pan, Z H; Lei, S Z; Chen, H S; Sucher, N J; Loscalzo, J; Singel, D J; Stamler, J S

1993-08-12

Congeners of nitrogen monoxide (NO) are neuroprotective and neurodestructive. To address this apparent paradox, we considered the effects on neurons of compounds characterized by alternative redox states of NO: nitric oxide (NO.) and nitrosonium ion (NO+). Nitric oxide, generated from NO. donors or synthesized endogenously after NMDA (N-methyl-D-aspartate) receptor activation, can lead to neurotoxicity. Here, we report that NO.- mediated neurotoxicity is engendered, at least in part, by reaction with superoxide anion (O2.-), apparently leading to formation of peroxynitrite (ONOO-), and not by NO. alone. In contrast, the neuroprotective effects of NO result from downregulation of NMDA-receptor activity by reaction with thiol group(s) of the receptor's redox modulatory site. This reaction is not mediated by NO. itself, but occurs under conditions supporting S-nitrosylation of NMDA receptor thiol (reaction or transfer of NO+). Moreover, the redox versatility of NO allows for its interconversion from neuroprotective to neurotoxic species by a change in the ambient redox milieu. The details of this complex redox chemistry of NO may provide a mechanism for harnessing neuroprotective effects and avoiding neurotoxicity in the central nervous system.

Molecular basis for subtype-specificity and high-affinity zinc inhibition in the GluN1-GluN2A NMDA receptor amino terminal domain

PubMed Central

Romero-Hernandez, Annabel; Simorowski, Noriko; Karakas, Erkan

2016-01-01

Summary Zinc is vastly present in the mammalian brain and controls functions of various cell surface receptors to regulate neurotransmission. A distinctive characteristic of N-methyl-D-aspartate (NMDA) receptors containing a GluN2A subunit is that their ion channel activity is allosterically inhibited by a nano-molar concentration of zinc that binds to an extracellular domain called an amino terminal domain (ATD). Despite physiological importance, the molecular mechanism underlying the high-affinity zinc inhibition has been incomplete due to lack of a GluN2A ATD structure. Here we show the first crystal structures of the heterodimeric GluN1-GluN2A ATD, which provide the complete map of the high-affinity zinc binding site and reveals distinctive features from the ATD of the GluN1-GluN2B subtype. Perturbation of hydrogen bond networks at the hinge of the GluN2A bi-lobe structure affects both zinc inhibition and open probability supporting the general model where the bi-lobe motion in ATD regulates the channel activity in NMDA receptors. PMID:27916457

DYNAMICS OF EXTRACELLULAR SIGNAL-REGULATED KINASE (ERK) ACTIVATION IN DEVELOPING CEREBELLAR GRANULE CELLS (CGC): A SYSTEMS BIOLOGY-ORIENTED STUDY

EPA Science Inventory

The objective of this study was to 1) characterize the dynamics of ERK activation in response to BDNF and NMDA; 2) use computational models to promote understanding of the signaling network underlying ERK activation.

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.

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

The role of excitatory amino acids and substance P in the mediation of the cough reflex within the nucleus tractus solitarii of the rabbit.

PubMed

Mutolo, Donatella; Bongianni, Fulvia; Fontana, Giovanni A; Pantaleo, Tito

2007-09-28

We hypothesized that cough evoked by mechanical stimulation of the tracheobronchial tree in the rabbit is primarily mediated by glutamatergic neurotransmission at the level of the caudal portions of the medial subnucleus of the nucleus tractus solitarii (NTS) and the lateral commissural NTS where cough-related afferents terminate, and that this reflex is potentiated by local release of substance P. To test our hypothesis, we performed bilateral microinjections (30-50 nl) of ionotropic glutamate receptor antagonists or substance P into these locations in pentobarbitone anaesthetized, spontaneously breathing rabbits. Blockade of NMDA and non-NMDA receptors by 50mM kynurenic acid abolished the cough reflex without affecting the Breuer-Hering inflation reflex or the pulmonary chemoreflex. Blockade of non-NMDA receptors using 10mM CNQX or 5mM NBQX caused identical effects. Blockade of NMDA receptors by 10mM D-AP5 strongly reduced, but did not abolish cough responses. Microinjections of 1mM substance P increased peak and rate of rise of abdominal muscle activity as well as cough number. These results are the first to provide evidence that ionotropic glutamate receptors, especially non-NMDA receptors, located within specific regions of NTS are primarily involved in the mediation of cough evoked by mechanical stimulation of the tracheobronchial tree in the rabbit. Present findings on substance P cough-enhancing effects extend previous observations and are relevant to the tachykinin-mediated central sensitization of the cough reflex. They also may provide hints for further studies on centrally acting antitussive drugs.

Separate intramolecular targets for protein kinase A control N-methyl-D-aspartate receptor gating and Ca2+ permeability.

PubMed

Aman, Teresa K; Maki, Bruce A; Ruffino, Thomas J; Kasperek, Eileen M; Popescu, Gabriela K

2014-07-04

Protein kinase A (PKA) enhances synaptic plasticity in the central nervous system by increasing NMDA receptor current amplitude and Ca(2+) flux in an isoform-dependent yet poorly understood manner. PKA phosphorylates multiple residues on GluN1, GluN2A, and GluN2B subunits in vivo, but the functional significance of this multiplicity is unknown. We examined gating and permeation properties of recombinant NMDA receptor isoforms and of receptors with altered C-terminal domain (CTDs) prior to and after pharmacological inhibition of PKA. We found that PKA inhibition decreased GluN1/GluN2B but not GluN1/GluN2A gating; this effect was due to slower rates for receptor activation and resensitization and was mediated exclusively by the GluN2B CTD. In contrast, PKA inhibition reduced NMDA receptor-relative Ca(2+) permeability (PCa/PNa) regardless of the GluN2 isoform and required the GluN1 CTD; this effect was due primarily to decreased unitary Ca(2+) conductance, because neither Na(+) conductance nor Ca(2+)-dependent block was altered substantially. Finally, we show that both the gating and permeation effects can be reproduced by changing the phosphorylation state of a single residue: GluN2B Ser-1166 and GluN1 Ser-897, respectively. We conclude that PKA effects on NMDA receptor gating and Ca(2+) permeability rely on distinct phosphorylation sites located on the CTD of GluN2B and GluN1 subunits. This separate control of NMDA receptor properties by PKA may account for the specific effects of PKA on plasticity during synaptic development and may lead to drugs targeted to alter NMDA receptor gating or Ca(2+) permeability. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

The lathyrus toxin, {beta}-N-oxalyl-L-{alpha},{beta}-diaminopropionic acid (ODAP), and homocysteic acid sensitize CA1 pyramidal neurons to cystine and L-2-amino-6-phosphonohexanoic acid

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

Chase, L.A.; Peterson, N.L.; Koerner, J.F.

2007-02-15

A brief exposure of hippocampal slices to L-quisqualic acid (QUIS) sensitizes CA1 pyramidal neurons 30- to 250-fold to depolarization by certain excitatory amino acids analogues, e.g., L-2-amino-6-phosphonohexanoic acid (L-AP6), and by the endogenous compound, L-cystine. This phenomenon has been termed QUIS sensitization. A mechanism similar to that previously described for QUIS neurotoxicity has been proposed to describe QUIS sensitization. Specifically, QUIS has been shown to be sequestered into GABAergic interneurons by the System x{sub c} {sup -} and subsequently released by heteroexchange with cystine or L-AP6, resulting in activation of non-NMDA receptors. We now report two additional neurotoxins, the Lathyrusmore » excitotoxin, {beta}-N-oxalyl-L-{alpha},{beta}-diaminopropionic acid (ODAP), and the endogenous compound, L-homocysteic acid (HCA), sensitize CA1 hippocampal neurons > 50-fold to L-AP6 and > 10-fold to cystine in a manner similar to QUIS. While the cystine- or L-AP6-mediated depolarization can be inhibited by the non-NMDA receptor antagonist CNQX in ODAP- or QUIS-sensitized slices, the NMDA antagonist D-AP5 inhibits depolarization by cystine or L-AP6 in HCA-sensitized slices. Thus, HCA is the first identified NMDA agonist that induces phosphonate or cystine sensitization. Like QUIS sensitization, the sensitization evoked by either ODAP or HCA can be reversed by a subsequent exposure to 2 mM {alpha}-aminoadipic acid. Finally, we have demonstrated that there is a correlation between the potency of inducers for triggering phosphonate or cystine sensitivity and their affinities for System x{sub c} {sup -} and either the non-NMDA or NMDA receptor. Thus, the results of this study support our previous model of QUIS sensitization and have important implications for the mechanisms of neurotoxicity, neurolathyrism and hyperhomocystinemia.« less

Harmaline competitively inhibits [3H]MK-801 binding to the NMDA receptor in rabbit brain.

PubMed

Du, W; Aloyo, V J; Harvey, J A

1997-10-03

Harmaline, a beta-carboline derivative, is known to produce tremor through a direct activation of cells in the inferior olive. However, the receptor(s) through which harmaline acts remains unknown. It was recently reported that the tremorogenic actions of harmaline could be blocked by the noncompetitive NMDA channel blocker, MK-801. This study examined whether the blockade of harmaline's action, in the rabbit, by MK-801 was due to a pharmacological antagonism at the MK-801 binding site. This was accomplished by measurement of [3H]MK-801 binding in membrane fractions derived from tissue containing the inferior olivary nucleus and from cerebral cortex. Harmaline completely displaced saturable [3H]MK-801 binding in both the inferior olive and cortex with apparent IC50 values of 60 and 170 microM, respectively. These IC50 values are consistent with the high doses of harmaline required to produce tremor, e.g., 10-30 mg/kg. Non-linear curve fitting analysis of [3H]MK-801 saturation experiments indicated that [3H]MK-801 bound to a single site and that harmaline's displacement of [3H]MK-801 binding to the NMDA receptor was competitive as indicated by a shift in Kd but not in Bmax. In addition, a Schild plot gave a slope that was not significantly different from 1 indicating that harmaline was producing a displacement of [3H]MK-801 from its binding site within the NMDA cation channel and not through an action at the glutamate or other allosteric sites on the NMDA receptor. These findings provide in vitro evidence that the competitive blockade of harmaline-induced tremor by MK-801 occurs within the calcium channel coupled to the NMDA receptor. Our hypothesis is that harmaline produces tremor by acting as an inverse agonist at the MK-801 binding site and thus opening the cation channel.

Ketamine Disrupts Frontal and Hippocampal Contribution to Encoding and Retrieval of Episodic Memory: An fMRI Study

PubMed Central

Honey, G.D.; Honey, R.A.E.; O’Loughlin, C.; Sharar, S.R.; Kumaran, D.; Suckling, J.; Menon, D.K.; Sleator, C.; Bullmore, E.T.; Fletcher, P.C.

2012-01-01

The N-methyl-d-aspartate (NMDA) receptor antagonist ketamine produces episodic memory deficits. We used functional magnetic resonance imaging to characterize the effects of ketamine on frontal and hippocampal responses to memory encoding and retrieval in healthy volunteers using a double-blind, placebo-controlled, randomized, within-subjects comparison of two doses of intravenous ketamine. Dissociation of the effects of ketamine on encoding and retrieval processes was achieved using two study-test cycles: in the first, items were encoded prior to drug infusion and retrieval tested, during scanning, on drug; in the second, encoding was scanned on drug, and retrieval tested once ketamine plasma levels had declined. We additionally determined the interaction of ketamine with the depth of processing that occurred at encoding. A number of effects upon task-dependent activations were seen. Overall, our results suggest that left frontal activation is augmented by ketamine when elaborative semantic processing is required at encoding. In addition, successful encoding on ketamine is supplemented by additional non-verbal processing that is incidental to task demands. The effects of ketamine at retrieval are consistent with impaired access to accompanying contextual features of studied items. Our findings show that, even when overt behaviour is unimpaired, ketamine has an impact upon the recruitment of key regions in episodic memory task performance. PMID:15537676

NMDA Receptors Are Not Required for Pattern Completion During Associative Memory Recall

PubMed Central

Gu, Yiran; Cui, Zhenzhong; Tsien, Joe Z.

2011-01-01

Pattern completion, the ability to retrieve complete memories initiated by subsets of external cues, has been a major focus of many computation models. A previously study reports that such pattern completion requires NMDA receptors in the hippocampus. However, such a claim was derived from a non-inducible gene knockout experiment in which the NMDA receptors were absent throughout all stages of memory processes as well as animal's adult life. This raises the critical question regarding whether the previously described results were truly resulting from the requirement of the NMDA receptors in retrieval. Here, we have examined the role of the NMDA receptors in pattern completion via inducible knockout of NMDA receptors limited to the memory retrieval stage. By using two independent mouse lines, we found that inducible knockout mice, lacking NMDA receptor in either forebrain or hippocampus CA1 region at the time of memory retrieval, exhibited normal recall of associative spatial reference memory regardless of whether retrievals took place under full-cue or partial-cue conditions. Moreover, systemic antagonism of NMDA receptor during retention tests also had no effect on full-cue or partial-cue recall of spatial water maze memories. Thus, both genetic and pharmacological experiments collectively demonstrate that pattern completion during spatial associative memory recall does not require the NMDA receptor in the hippocampus or forebrain. PMID:21559402

The NMDA receptor/ion channel complex: a drug target for modulating synaptic plasticity and excitotoxicity.

PubMed

Albensi, Benedict C

2007-01-01

A recent search on PubMed for the phrase NMDA receptor results in 2,190 hits on this topic for review articles and 20,100 hits for experimental papers. This is a direct reflection of the intensiveness, significance, and complexity associated with the research on this key receptor protein over the last several decades. In this review, we briefly describe the NMDA receptor structure, discuss the role of NMDA receptors in modulating synaptic plasticity and excitotoxicity, explore age-dependent changes in NMDA receptor functioning, and survey interesting NMDA receptor blockers. Given the huge existing literature on the subject, an exhaustive review has not been endeavored. Instead, an attempt was made to point out those studies that have been instrumental in the field or that are of special interest.

Activation of the prelimbic medial prefrontal cortex induces anxiety-like behaviors via N-Methyl-D-aspartate receptor-mediated glutamatergic neurotransmission in mice.

PubMed

Saitoh, Akiyoshi; Ohashi, Masanori; Suzuki, Satoshi; Tsukagoshi, Mai; Sugiyama, Azusa; Yamada, Misa; Oka, Jun-Ichiro; Inagaki, Masatoshi; Yamada, Mitsuhiko

2014-08-01

We investigated the possible roles of the prelimbic medial prefrontal cortex (PL) in the regulation of anxiety-like behaviors by pharmacologically activating the terminals of neuronal inputs or postsynaptic efferent neurons with a sodium channel activator veratrine. The extracellular glutamate levels were measured by in vivo microdialysis, and the behaviors were assessed with the open field (OF) test in mice simultaneously. The samples were collected every 10 min for 60 min, as basal levels of glutamate. The medium containing drugs were perfused for 30 min. The OF test was performed in the last 10 min of drug perfusion. After the drug treatments, the perfusion medium containing drugs was switched back to perfusion medium without drugs, and then samples were collected for another 90 min. The extracellular glutamate levels were significantly elevated after local perfusion of veratrine in the PL. At the same time, perfusion of veratrine in the PL produced anxiety-like behaviors in mice. Local coperfusion of a sodium channel blocker, lamotrigine, completely diminished the veratrine-induced elevated extracellular glutamate levels and the behavioral changes. Local coperfusion of an NMDA receptor antagonist, MK-801, but not a non-NMDA (AMPA/kainate) receptor antagonist, CNQX, completely diminished the behavioral changes without any effects on the veratrine-induced elevated extracellular glutamate levels. This study demonstrates that the activation of the PL with veratrine induces anxiety-like behaviors via NMDA receptor-mediated glutamatergic neurotransmission in mice. © 2014 Wiley Periodicals, Inc.

Laminar circuit organization and response modulation in mouse visual cortex

PubMed Central

Olivas, Nicholas D.; Quintanar-Zilinskas, Victor; Nenadic, Zoran; Xu, Xiangmin

2012-01-01

The mouse has become an increasingly important animal model for visual system studies, but few studies have investigated local functional circuit organization of mouse visual cortex. Here we used our newly developed mapping technique combining laser scanning photostimulation (LSPS) with fast voltage-sensitive dye (VSD) imaging to examine the spatial organization and temporal dynamics of laminar circuit responses in living slice preparations of mouse primary visual cortex (V1). During experiments, LSPS using caged glutamate provided spatially restricted neuronal activation in a specific cortical layer, and evoked responses from the stimulated layer to its functionally connected regions were detected by VSD imaging. In this study, we first provided a detailed analysis of spatiotemporal activation patterns at specific V1 laminar locations and measured local circuit connectivity. Then we examined the role of cortical inhibition in the propagation of evoked cortical responses by comparing circuit activity patterns in control and in the presence of GABAa receptor antagonists. We found that GABAergic inhibition was critical in restricting layer-specific excitatory activity spread and maintaining topographical projections. In addition, we investigated how AMPA and NMDA receptors influenced cortical responses and found that blocking AMPA receptors abolished interlaminar functional projections, and the NMDA receptor activity was important in controlling visual cortical circuit excitability and modulating activity propagation. The NMDA receptor antagonist reduced neuronal population activity in time-dependent and laminar-specific manners. Finally, we used the quantitative information derived from the mapping experiments and presented computational modeling analysis of V1 circuit organization. Taken together, the present study has provided important new information about mouse V1 circuit organization and response modulation. PMID:23060751

Glutamatergic model psychoses: prediction error, learning, and inference.

PubMed

Corlett, Philip R; Honey, Garry D; Krystal, John H; Fletcher, Paul C

2011-01-01

Modulating glutamatergic neurotransmission induces alterations in conscious experience that mimic the symptoms of early psychotic illness. We review studies that use intravenous administration of ketamine, focusing on interindividual variability in the profundity of the ketamine experience. We will consider this individual variability within a hypothetical model of brain and cognitive function centered upon learning and inference. Within this model, the brains, neural systems, and even single neurons specify expectations about their inputs and responding to violations of those expectations with new learning that renders future inputs more predictable. We argue that ketamine temporarily deranges this ability by perturbing both the ways in which prior expectations are specified and the ways in which expectancy violations are signaled. We suggest that the former effect is predominantly mediated by NMDA blockade and the latter by augmented and inappropriate feedforward glutamatergic signaling. We suggest that the observed interindividual variability emerges from individual differences in neural circuits that normally underpin the learning and inference processes described. The exact source for that variability is uncertain, although it is likely to arise not only from genetic variation but also from subjects' previous experiences and prior learning. Furthermore, we argue that chronic, unlike acute, NMDA blockade alters the specification of expectancies more profoundly and permanently. Scrutinizing individual differences in the effects of acute and chronic ketamine administration in the context of the Bayesian brain model may generate new insights about the symptoms of psychosis; their underlying cognitive processes and neurocircuitry.

Memantine ameliorates autistic behavior, biochemistry & blood brain barrier impairments in rats.

PubMed

Kumar, Hariom; Sharma, Bhupesh

2016-06-01

Autism spectrum disorder (ASD) is a neurodevelopmental disorder, commonly characterized by altered social behavior, communication, biochemistry and pathological conditions. One percent of the worldwide population suffers from autism and males suffer more than females. NMDA receptors have the important role in neurodevelopment, neuropsychiatric and neurodegenerative disorders. This study has been designed to investigate the role of memantine, a NMDA receptor modulator, in prenatal valproic acid-induced autism in rats. Animals with prenatal valproic acid have shown the reduction in social interaction (three-chamber social behavior apparatus), spontaneous alternation (Y-Maze), exploratory activity (Hole board test), intestinal motility, serotonin levels (both in prefrontal cortex and ileum) and prefrontal cortex mitochondrial complex activity (complex I, II, IV). Furthermore, prenatal valproic acid-treated animals have shown an increase in locomotion (actophotometer), anxiety (elevated plus maze), brain oxidative stress (thiobarbituric acid reactive species, glutathione, catalase), nitrosative stress (nitrite/nitrate), inflammation (both in brain and ileum myeloperoxidase activity), calcium and blood-brain barrier permeability. Treatment with memantine has significantly attenuated prenatal valproic acid-induced reduction in social interaction, spontaneous alteration, exploratory activity intestinal motility, serotonin levels and prefrontal cortex mitochondrial complex activity. Furthermore, memantine has also attenuated the prenatal valproic acid-induced increase in locomotion, anxiety, brain oxidative and nitrosative stress, inflammation, calcium and blood-brain barrier permeability. Thus, it may be concluded that prenatal valproic acid has induced autistic behavior, biochemistry and blood-brain barrier impairment in animals, which were significantly attenuated by memantine. NMDA receptor modulators like memantine should be explored further for the therapeutic benefits in autism. Copyright © 2016 Elsevier Inc. All rights reserved.

Temporal and regional alterations in NMDA receptor expression in Mecp2-null mice

PubMed Central

Blue, Mary E.; Kaufmann, Walter E.; Bressler, Joseph; Eyring, Charlotte; O’Driscoll, Cliona; Naidu, SakkuBai; Johnston, Michael V.

2014-01-01

Our previous postmortem study of girls with Rett Syndrome (RTT), a development disorder caused by MECP2 mutations, found increases in the density of NMDA receptors in the prefrontal cortex of 2–8 year-old girls, while girls older than 10 years had reductions in NMDA receptors compared to age matched controls (Blue et al., 1999b). Using [3H]-CGP to label NMDA type glutamate receptors in 2 and 7 week old wildtype (WT), Mecp2-null and Mecp2-heterozygous (HET) mice (Bird model), we found that frontal areas of the brain also exhibited a bimodal pattern in NMDA expression, with increased densities of NMDA receptors in Mecp2-null mice at 2 weeks of age, but decreased densities at 7 weeks of age. Visual cortex showed a similar pattern, while other cortical regions only exhibited changes in NMDA receptor densities at 2 weeks (retrosplenial granular) or 7 weeks (somatosensory). In thalamus of null mice, NMDA receptors were increased at 2 and 7 weeks. No significant differences in density were found between HET and WT mice at both ages. Western blots for NMDAR1 expression in frontal brain showed higher levels of expression in Mecp2-null mice at two weeks of age, but not at 1 or 7 weeks of age. Our mouse data support the notion that deficient MeCP2 function is the primary cause of the NMDA receptor changes we observed in RTT. Furthermore, the findings of regional and temporal differences in NMDA expression illustrate the importance of age and brain region in evaluating different genotypes of mice. PMID:21901842

Seizure activity results in calcium- and mitochondria-independent ROS production via NADPH and xanthine oxidase activation

PubMed Central

Kovac, S; Domijan, A-M; Walker, M C; Abramov, A Y

2014-01-01

Seizure activity has been proposed to result in the generation of reactive oxygen species (ROS), which then contribute to seizure-induced neuronal damage and eventually cell death. Although the mechanisms of seizure-induced ROS generation are unclear, mitochondria and cellular calcium overload have been proposed to have a crucial role. We aim to determine the sources of seizure-induced ROS and their contribution to seizure-induced cell death. Using live cell imaging techniques in glioneuronal cultures, we show that prolonged seizure-like activity increases ROS production in an NMDA receptor-dependent manner. Unexpectedly, however, mitochondria did not contribute to ROS production during seizure-like activity. ROS were generated primarily by NADPH oxidase and later by xanthine oxidase (XO) activity in a calcium-independent manner. This calcium-independent neuronal ROS production was accompanied by an increase in intracellular [Na+] through NMDA receptor activation. Inhibition of NADPH or XO markedly reduced seizure-like activity-induced neuronal apoptosis. These findings demonstrate a critical role for ROS in seizure-induced neuronal cell death and identify novel therapeutic targets. PMID:25275601

Non-ionotropic signaling by the NMDA receptor: controversy and opportunity.

PubMed

Gray, John A; Zito, Karen; Hell, Johannes W

2016-01-01

Provocative emerging evidence suggests that the N-methyl-d-aspartate (NMDA) receptor can signal in the absence of ion flux through the receptor. This non-ionotropic signaling is thought to be due to agonist-induced conformational changes in the receptor, independently of channel opening. Non-ionotropic NMDA receptor signaling has been proposed to be sufficient to induce synaptic long-term depression (LTD), directly challenging the decades-old model that prolonged low-level calcium influx is required to induce LTD. Here, we briefly review these recent findings, focusing primarily on the potential role of non-ionotropic signaling in NMDA receptor-mediated LTD. Further reports concerning additional roles of non-ionotropic NMDA receptor signaling are also discussed. If validated, this new view of NMDA receptor-mediated signaling will usher in an exciting new era of exploring synapse function and dysfunction.

Non-ionotropic signaling by the NMDA receptor: controversy and opportunity

PubMed Central

Gray, John A.; Zito, Karen; Hell, Johannes W.

2016-01-01

Provocative emerging evidence suggests that the N-methyl-d-aspartate (NMDA) receptor can signal in the absence of ion flux through the receptor. This non-ionotropic signaling is thought to be due to agonist-induced conformational changes in the receptor, independently of channel opening. Non-ionotropic NMDA receptor signaling has been proposed to be sufficient to induce synaptic long-term depression (LTD), directly challenging the decades-old model that prolonged low-level calcium influx is required to induce LTD. Here, we briefly review these recent findings, focusing primarily on the potential role of non-ionotropic signaling in NMDA receptor-mediated LTD. Further reports concerning additional roles of non-ionotropic NMDA receptor signaling are also discussed. If validated, this new view of NMDA receptor-mediated signaling will usher in an exciting new era of exploring synapse function and dysfunction. PMID:27303637

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

Discussion of Bogerts' temporolimbic system theory of paranoid schizophrenia.

PubMed

Olney, J W; Farber, N B

1997-01-01

Olney and Farber present their work with N-methyl-D-aspartate (NMDA) antagonists, which are psychotogens, and propose that the structural changes described by Bogerts could be accounted for by a two-stage process. The first stage of the process would occur early in life and would culminate in the selective loss of NMDA-receptor bearing gamma-aminobutyric acid (GABA)ergic neurons and thus render the brain into a NMDA receptor hypofunctional (NRH) state. Such a loss would set the foundation for the second stage in which the neural circuits that have been altered by the loss of these GABAergic interneurons would become activated in late adolescence but would be dysfunctional. Dysfunction of this circuit would lead to the psychopathology of schizophrenia and potentially, if severe enough, to neuronal degeneration. Thus, the changes described by Bogerts could originate partially in early life and partially in adulthood. Based on their animal model, the authors suggest studies that should be carried out in humans.

In vitro studies on the putative function of N-acetylaspartate as an osmoregulator.

PubMed

Tranberg, Mattias; Abbas, Abdul-Karim; Sandberg, Mats

2007-07-01

Efflux and tissue content of N-acetylaspartate (NAA) and amino acids were evaluated from cultured and acutely prepared hippocampal slices in response to changes in osmolarity. The osmoregulator taurine, but not NAA, was lost from both types of slices after moderate reductions in extracellular osmolarity (-60 mOsm) for 10-48 h. Hypoosmotic shock (-166 mOsm) for 5 min resulted in unselective efflux of several amino acids from acutely prepared slices. Notably, the efflux of taurine, but not NAA, was prominent also after the shock. Efflux of NAA was markedly enhanced by NMDA and high K(+), in particular after the stimulation period. The high K(+)-mediated efflux was decreased by high extracellular osmolarity and a NMDA-receptor antagonist. The results indicate that NAA efflux can be induced by a sudden non-physiological decrease in extracellular osmolarity but not by prolonged more moderate changes in osmolarity. The mechanisms behind the efflux of NAA by high K(+) are complex and may involve both swelling and activation of NMDA-receptors.

Microinjection of l-glutamate into the nucleus ambiguus partially inhibits gastric motility through the NMDA receptor - nitric oxide pathway.

PubMed

Sun, Hong-Zhao; Zhao, Shu-Zhen; Ai, Hong-Bin

2014-06-01

We have previously reported that both l-glutamate (l-Glu) and nitric oxide (NO) modulate gastric motility in the nucleus ambiguus (NA). The aim of this study is to explore the potential correlation between the l-Glu and NO. A latex balloon connected to a pressure transducer was inserted into the pylorus through the fundus of anesthetized male Wistar rats to continuously record changes in gastric smooth muscle contractile curves. Pretreatment with the NO-synthase inhibitor N-nitro-l-arginine methylester (l-NAME) did not completely abolish the inhibitory effect of l-Glu on gastric motility, but intravenous injection of the ganglionic blocker hexamethonium bromide (Hb) did. By using a specific N-methyl-d-aspartic acid (NMDA) receptor antagonist, we blocked the inhibitory effect of the NO-donor sodium nitroprusside (SNP) on gastric motility. These results suggest that microinjections of l-Glu into the NA inhibits gastric motility by activating the cholinergic preganglionic neurons, partially through the NMDA receptor - NO pathway.

Structure and symmetry inform gating principles of ionotropic glutamate receptors.

PubMed

Zhu, Shujia; Gouaux, Eric

2017-01-01

Ionotropic glutamate receptors (iGluRs) transduce signals derived from release of the excitatory neurotransmitter glutamate from pre-synaptic neurons into excitation of post-synaptic neurons on a millisecond time-scale. In recent years, the elucidation of full-length iGluR structures of NMDA, AMPA and kainate receptors by X-ray crystallography and single particle cryo-electron microscopy has greatly enhanced our understanding of the interrelationships between receptor architecture and gating mechanism. Here we briefly review full-length iGluR structures and discuss the similarities and differences between NMDA receptors and non-NMDA iGluRs. We focus on distinct conformations, including ligand-free, agonist-bound active, agonist-bound desensitized and antagonist-bound conformations as well as modulator and auxiliary protein-bound states. These findings provide insights into structure-based mechanisms of iGluR gating and modulation which together shape the amplitude and time course of the excitatory postsynaptic potential. This article is part of the Special Issue entitled 'Ionotropic glutamate receptors'. Copyright © 2016 Elsevier Ltd. All rights reserved.

On the ligand binding profile and desensitization of plant ionotropic glutamate receptor (iGluR)-like channels functioning in MAMP-triggered Ca²⁺ influx.

PubMed

Kwaaitaal, Mark; Maintz, Jens; Cavdar, Meltem; Panstruga, Ralph

2012-11-01

The generation of intracellular microbe-associated molecular pattern (MAMP)-triggered Ca²⁺ transients was recently demonstrated to involve ionotropic Glutamate Receptor (iGluR)-like channels in Arabidopsis and tobacco. Here we elaborate on our previous findings and refine our insights in the putative agonist binding profile and potential mode of desensitization of MAMP-activated plant iGluRs. Based on results from pharmacological inhibition and desensitization experiments, we propose that plant iGluR complexes responsible for the MAMP-triggered Ca²⁺ signature have a binding profile that combines the specificities of mammalian NMDA-and non-NMDA types of iGluRs, possibly reflecting the evolutionary history of plant and animal iGluRs. We further hypothesize that, analogous to the mammalian NMDA-NR1 receptor, desensitization of plant iGluR-like channels might involve binding of the ubiquitous Ca²⁺ sensor calmodulin to a cytoplasmic C-terminal domain.

The system N transporter SN2 doubles as a transmitter precursor furnisher and a potential regulator of NMDA receptors.

PubMed

Hamdani, El Hassan; Gudbrandsen, Marius; Bjørkmo, Mona; Chaudhry, Farrukh Abbas

2012-11-01

Activation of NMDA receptor requires two co-agonists, glutamate and glycine. Despite its intrinsic role in brain functions molecular mechanisms involved in glutamate replenishment and identification of the origin of glycine have eluded characterization. We have performed direct measurements of glycine flux by SN2 (Slc38a5; also known as SNAT5), executed extensive electrophysiological characterization as well as implemented ratiometric analyses to show that SN2 transport resembles SN1 in mechanism but differ in functional implications. We report that rat SN2 mediates electroneutral and bidirectional transport of glutamine and glycine at perisynaptic astroglial membranes. Sophisticated coupled and uncoupled movements of H(+) differentially associate with glutamine and glycine transport by SN2 and regulate pH(i) and the release mode of the transporter. Consequently, SN2 doubles as a transmitter precursor furnisher and a potential regulator of NMDA receptors. Copyright © 2012 Wiley Periodicals, Inc.

Excitotoxicity Induced by Realgar in the Rat Hippocampus: the Involvement of Learning Memory Injury, Dysfunction of Glutamate Metabolism and NMDA Receptors.

PubMed

Huo, Tao-guang; Li, Wei-kai; Zhang, Ying-hua; Yuan, Jie; Gao, Lan-yue; Yuan, Yuan; Yang, Hui-lei; Jiang, Hong; Sun, Gui-fan

2015-01-01

Realgar is a type of mineral drug containing arsenic. The nervous system toxicity of realgar has received extensive attention. However, the underlying mechanisms of realgar-induced neurotoxicity have not been clearly elucidated. To explore the mechanisms that contribute to realgar-induced neurotoxicity, weanling rats were exposed to realgar (0, 0.3, 0.9, 2.7 g/kg) for 6 weeks, and cognitive ability was tested using the Morris water maze (MWM) test and object recognition task (ORT). The levels of arsenic in the blood and hippocampus were monitored. The ultrastructures of hippocampal neurons were observed. The levels of glutamate (Glu) and glutamine (Gln) in the hippocampus and hippocampal CA1 region; the activities of glutamine synthetase (GS) and phosphate-activated glutaminase (PAG); the mRNA and protein expression of glutamate transporter 1 (GLT-1), glutamate/aspartate transporter (GLAST), and N-methyl-D-aspartate (NMDA) receptors; and the level of intracellular Ca(2+) were also investigated. The results indicate that the rats developed deficiencies in cognitive ability after a 6-week exposure to realgar. The arsenic contained in realgar and the arsenic metabolites passed through the blood-brain barrier (BBB) and accumulated in the hippocampus, which resulted in the excessive accumulation of Glu in the extracellular space. The excessive accumulation of Glu in the extracellular space induced excitotoxicity, which was shown by enhanced GS and PAG activities, inhibition of GLT-1 mRNA and protein expression, alterations in NMDA receptor mRNA and protein expression, disturbance of intracellular Ca(2+) homeostasis, and ultrastructural changes in hippocampal neurons. In conclusion, the findings from our study indicate that exposure to realgar induces excitotoxicity and that the mechanism by which this occurs may be associated with disturbances in Glu metabolism and transportation and alterations in NMDA receptor expression.

Synaptically activated Ca2+ waves and NMDA spikes locally suppress voltage-dependent Ca2+ signalling in rat pyramidal cell dendrites

PubMed Central

Manita, Satoshi; Miyazaki, Kenichi; Ross, William N

2011-01-01

Abstract Postsynaptic [Ca2+]i changes contribute to several kinds of plasticity in pyramidal neurons. We examined the effects of synaptically activated Ca2+ waves and NMDA spikes on subsequent Ca2+ signalling in CA1 pyramidal cell dendrites in hippocampal slices. Tetanic synaptic stimulation evoked a localized Ca2+ wave in the primary apical dendrites. The [Ca2+]i increase from a backpropagating action potential (bAP) or subthreshold depolarization was reduced if it was generated immediately after the wave. The suppression had a recovery time of 30–60 s. The suppression only occurred where the wave was generated and was not due to a change in bAP amplitude or shape. The suppression also could be generated by Ca2+ waves evoked by uncaging IP3, showing that other signalling pathways activated by the synaptic tetanus were not required. The suppression was proportional to the amplitude of the [Ca2+]i change of the Ca2+ wave and was not blocked by a spectrum of kinase or phosphatase inhibitors, consistent with suppression due to Ca2+-dependent inactivation of Ca2+ channels. The waves also reduced the frequency and amplitude of spontaneous, localized Ca2+ release events in the dendrites by a different mechanism, probably by depleting the stores at the site of wave generation. The same synaptic tetanus often evoked NMDA spike-mediated [Ca2+]i increases in the oblique dendrites where Ca2+ waves do not propagate. These NMDA spikes suppressed the [Ca2+]i increase caused by bAPs in those regions. [Ca2+]i increases by Ca2+ entry through voltage-gated Ca2+ channels also suppressed the [Ca2+]i increases from subsequent bAPs in regions where the voltage-gated [Ca2+]i increases were largest, showing that all ways of raising [Ca2+]i could cause suppression. PMID:21844002

The effects of an acute challenge with the NMDA receptor antagonists, MK-801, PEAQX, and ifenprodil, on social inhibition in adolescent and adult male rats

PubMed Central

Spear, Linda P.

2013-01-01

Rationale NMDA antagonists consistently produce social inhibition in adult animals, although effects of these manipulations on social behavior of adolescents are relatively unknown. Objectives The aim of this study was to assess potential age differences in the socially inhibitory effects of the non-competitive NMDA antagonist, MK-801, as well as NR2 subunit selective effects, given the regional and developmental differences that exist for the NR2 subunit during ontogeny. Methods In separate experiments, adolescent and adult male Sprague–Dawley rats were treated acutely with MK-801 (0, 0.05, 0.1, 0.2 mg/kg, i.p.), the NR2A antagonist, PEAQX (2.5, 5, 10, 20 mg/kg, s.c.), or the NR2B antagonist, ifenprodil (1.5, 3, 6, 12 mg/kg, i.p.), 10 min prior to a social interaction test. Results Adolescents required higher doses of MK-801 (0.1 and 0.2 mg/kg) to induce social suppression, whereas adults demonstrated reductions in social activity after all doses. Likewise, adolescents required higher doses of ifenprodil (6 and 12 mg/kg) to produce social inhibitory effects relative to adults (all doses). In contrast, adults were less sensitive to PEAQX than adolescents, with adults showing social inhibition after 20 mg/kg whereas adolescents showed this effect following 10 and 20 mg/kg. Although locomotor activity was generally reduced at both ages by all drugs tested, ANCOVAs using locomotor activity as a covariate revealed similar patterns of social inhibitory effects. Conclusions Adolescents are less sensitive than adults to the disruption of social behavior by NMDA and NR2B-selective receptor antagonism, but not by an NR2A antagonist—age differences that may be related to different subunit expression patterns during development. PMID:24043344

Nuclear respiratory factor 2 regulates the expression of the same NMDA receptor subunit genes as NRF-1: both factors act by a concurrent and parallel mechanism to couple energy metabolism and synaptic transmission.

PubMed

Priya, Anusha; Johar, Kaid; Wong-Riley, Margaret T T

2013-01-01

Neuronal activity and energy metabolism are tightly coupled processes. Previously, we found that nuclear respiratory factor 1 (NRF-1) transcriptionally co-regulates energy metabolism and neuronal activity by regulating all 13 subunits of the critical energy generating enzyme, cytochrome c oxidase (COX), as well as N-methyl-d-aspartate (NMDA) receptor subunits 1 and 2B, GluN1 (Grin1) and GluN2B (Grin2b). We also found that another transcription factor, nuclear respiratory factor 2 (NRF-2 or GA-binding protein) regulates all subunits of COX as well. The goal of the present study was to test our hypothesis that NRF-2 also regulates specific subunits of NMDA receptors, and that it functions with NRF-1 via one of three mechanisms: complementary, concurrent and parallel, or a combination of complementary and concurrent/parallel. By means of multiple approaches, including in silico analysis, electrophoretic mobility shift and supershift assays, in vivo chromatin immunoprecipitation of mouse neuroblastoma cells and rat visual cortical tissue, promoter mutations, real-time quantitative PCR, and western blot analysis, NRF-2 was found to functionally regulate Grin1 and Grin2b genes, but not any other NMDA subunit genes. Grin1 and Grin2b transcripts were up-regulated by depolarizing KCl, but silencing of NRF-2 prevented this up-regulation. On the other hand, over-expression of NRF-2 rescued the down-regulation of these subunits by the impulse blocker TTX. NRF-2 binding sites on Grin1 and Grin2b are conserved among species. Our data indicate that NRF-2 and NRF-1 operate in a concurrent and parallel manner in mediating the tight coupling between energy metabolism and neuronal activity at the molecular level. Copyright © 2012 Elsevier B.V. All rights reserved.

Inhibition of Morphine Tolerance and Dependence by the NMDA Receptor Antagonist MK-801

NASA Astrophysics Data System (ADS)

Trujillo, Keith A.; Akil, Huda

1991-01-01

The N-methyl-D-aspartate (NMDA) subtype of the glutamate receptor is an important mediator of several forms of neural and behavioral plasticity. The present studies examined whether NMDA receptors might be involved in the development of opiate tolerance and dependence, two examples of behavioral plasticity. The noncompetitive NMDA receptor antagonist MK-801 attenuated the development of tolerance to the analgesic effect of morphine without affecting acute morphine analgesia. In addition, MK-801 attenuated the development of morphine dependence as assessed by naloxone-precipitated withdrawal. These results suggest that NMDA receptors may be important in the development of opiate tolerance and dependence.

Mapping and Deciphering Neural Codes of NMDA Receptor-Dependent Fear Memory Engrams in the Hippocampus

PubMed Central

Tsien, Joe Z.

2013-01-01

Mapping and decoding brain activity patterns underlying learning and memory represents both great interest and immense challenge. At present, very little is known regarding many of the very basic questions regarding the neural codes of memory: are fear memories retrieved during the freezing state or non-freezing state of the animals? How do individual memory traces give arise to a holistic, real-time associative memory engram? How are memory codes regulated by synaptic plasticity? Here, by applying high-density electrode arrays and dimensionality-reduction decoding algorithms, we investigate hippocampal CA1 activity patterns of trace fear conditioning memory code in inducible NMDA receptor knockout mice and their control littermates. Our analyses showed that the conditioned tone (CS) and unconditioned foot-shock (US) can evoke hippocampal ensemble responses in control and mutant mice. Yet, temporal formats and contents of CA1 fear memory engrams differ significantly between the genotypes. The mutant mice with disabled NMDA receptor plasticity failed to generate CS-to-US or US-to-CS associative memory traces. Moreover, the mutant CA1 region lacked memory traces for “what at when” information that predicts the timing relationship between the conditioned tone and the foot shock. The degraded associative fear memory engram is further manifested in its lack of intertwined and alternating temporal association between CS and US memory traces that are characteristic to the holistic memory recall in the wild-type animals. Therefore, our study has decoded real-time memory contents, timing relationship between CS and US, and temporal organizing patterns of fear memory engrams and demonstrated how hippocampal memory codes are regulated by NMDA receptor synaptic plasticity. PMID:24302990

Differential antagonism of tetramethylenedisulfotetramine-induced seizures by agents acting at NMDA and GABAA receptors

PubMed Central

Shakarjian, Michael P.; Velíšková, Jana; Stanton, Patric K.; Velíšek, Libor

2012-01-01

Tetramethylenedisulfotetramine (TMDT) is a highly lethal neuroactive rodenticide responsible for many accidental and intentional poisonings in mainland China. Ease of synthesis, water solubility, potency, and difficulty to treat make TMDT a potential weapon for terrorist activity. We characterized TMDT-induced convulsions and mortality in male C57BL/6 mice. TMDT (ip) produced a continuum of twitches, clonic, and tonic-clonic seizures decreasing in onset latency and increasing in severity with increasing dose; 0.4 mg/kg was 100% lethal. The NMDA antagonist, ketamine (35 mg/kg) injected ip immediately after the first TMDT-induced seizure, did not change number of tonic-clonic seizures or lethality, but increased the number of clonic seizures. Doubling the ketamine dose decreased tonic-clonic seizures and eliminated lethality through a 60 min observation period. Treating mice with another NMDA antagonist, MK-801, 0.5 or 1 mg/kg ip, showed similar effects as low and high doses of ketamine, respectively, and prevented lethality, converting status epilepticus EEG activity to isolated interictal discharges. Treatment with these agents 15 min prior to TMDT administration did not increase their effectiveness. Post-treatment with the GABAA receptor allosteric enhancer diazepam (5 mg/kg) greatly reduced seizure manifestations and prevented lethality 60 min post-TMDT, but ictal events were evident in EEG recordings and, hours post-treatment, mice experienced status epilepticus and died. Thus, TMDT is a highly potent and lethal convulsant for which single-dose benzodiazepine treatment is inadequate in managing electrographic seizures or lethality. Repeated benzodiazepine dosing or combined application of benzodiazepines and NMDA receptor antagonists are more likely to be effective in treating TMDT poisoning. PMID:23022509

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.

Modulation of benzo[a]pyrene induced neurotoxicity in female mice actively immunized with a B[a]P–diphtheria toxoid conjugate

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

Schellenberger, Mario T.; Grova, Nathalie; Farinelle, Sophie

Benzo[a]pyrene (B[a]P) is a small molecular weight carcinogen and the prototype of polycyclic aromatic hydrocarbons (PAHs). While these compounds are primarily known for their carcinogenicity, B[a]P and its metabolites are also neurotoxic for mammalian species. To develop a prophylactic immune strategy against detrimental effects of B[a]P, female Balb/c mice immunized with a B[a]P–diphtheria toxoid (B[a]P–DT) conjugate vaccine were sub-acutely exposed to 2 mg/kg B[a]P and behavioral performances were monitored in tests related to learning and memory, anxiety and motor coordination. mRNA expression of the NMDA receptor (NR1, 2A and 2B subunits) involved in the above behavioral functions was measured inmore » 5 brain regions. B[a]P induced NMDA1 expression in three (hippocampus, amygdala and cerebellum) of five brain regions investigated, and modulated NMDA2 in two of the five brain regions (frontal cortex and cerebellum). Each one of these B[a]P-effects was reversed in mice that were immunized against this PAH, with measurable consequences on behavior such as anxiety, short term learning and memory. Thus active immunization against B[a]P with a B[a]P–DT conjugate vaccine had a protective effect and attenuated the pharmacological and neurotoxic effects even of high concentrations of B[a]P. - Highlights: • B[a]P-antibodies attenuated B[a]P induced NMDA expression in several brain regions. • B[a]P had measurable consequences on anxiety, short term learning and memory. • B[a]P immunization attenuated the pharmacological and neurotoxic effects of B[a]P. • Vaccination may also provide some protection against chemical carcinogenesis.« less

Memantine alters striatal plasticity inducing a shift of synaptic responses toward long-term depression.

PubMed

Mancini, Maria; Ghiglieri, Veronica; Bagetta, Vincenza; Pendolino, Valentina; Vannelli, Anna; Cacace, Fabrizio; Mineo, Desireé; Calabresi, Paolo; Picconi, Barbara

2016-02-01

Memantine is an open channel blocker that antagonizes NMDA receptors reducing the inappropriate calcium (Ca(2+)) influx occurring in presence of moderately increased glutamate levels. At the same time, memantine has the ability to preserve the transient physiological activation of NMDA receptor, essential for learning and memory formation at synaptic level. In the present study we investigated the effects exerted by memantine on striatal synaptic plasticity in rat striatal spiny projection neurons (SPNs). In vitro application of memantine in striatal slices elicited a disruption of long-term potentiation (LTP) induction and maintenance, and revealed, in the majority of the recorded neurons, a long-term depression (LTD), whose amplitude was concentration-dependent (0.3-10 μM). Interestingly, preincubation with the dopamine (DA) D2 receptor antagonist sulpiride (10 μM) prevented memantine-induced LTD and restored LTP. Moreover, the DA D2 agonist quinpirole (10 μM), similarly to memantine, induced LTD in a subgroup of SPNs. In addition, memantine-induced LTD was also prevented by the CB1 endocannabinoid receptor antagonist AM 251 (1 μM). These results suggest that the actions exerted by memantine on striatal synaptic plasticity, and in particular the induction of LTD observed in SPNs, could be attributed to its ability to activate DA D2 receptors. By contrast, blockade of NMDA receptor is not involved in memantine-induced LTD since APV (30 μM) and MK801 (10 μM), two NMDA receptor antagonists, failed to induce this form of synaptic plasticity. Our data indicate that memantine could be used as treatment of neurological disorders in which DA D2 receptor represents a possible therapeutic target. Copyright © 2015 Elsevier Ltd. All rights reserved.

Genetic differences in NMDA and D1 receptor levels, and operant responding for food and morphine in Lewis and Fischer 344 rats.

PubMed

Martín, Sonsoles; Lyupina, Yulia; Crespo, José Antonio; González, Begoña; García-Lecumberri, Carmen; Ambrosio, Emilio

2003-05-30

Previously, we have shown that Lewis (LEW) rats acquire faster than Fischer 344 (F344) rats operant food- and morphine-reinforced tasks under fixed-ratio schedules of reinforcement. The first purpose of the present work has been to study if differences in operant responding behavior may participate in the reported differences in morphine self-administration behavior between both inbred rat strains. To this end, we have analyzed the microstructure of responding obtained under a variable-interval (VI) of food reinforcement by calculating the inter-response time (IRT) for each rat strain. LEW rats exhibited shorter IRTs than F344 rats, suggesting that LEW rats may have an inherent high or compulsive operant responding activity. When subjects of both inbred rat strains were submitted to a schedule of morphine reinforcement of high responding requirements such as progressive ratio schedules, LEW rats also reached significantly higher breaking points and final response ratio than F344 rats for i.v. morphine self-administration. Given that there are neurochemical differences between both rat strains and that glutamatergic N-methyl-D-aspartate (NMDA) and dopaminergic D(1) receptors have been involved in operant responding behavior, a second purpose of this work has been to measure basal NMDA and D(1) receptor levels in these rat strains by quantitative receptor autoradiography. Compared to F344 rats, LEW rats showed higher basal NMDA receptor levels in frontal and cingulate cortex, caudate putamen, central amygdaloid nuclei, and intermediate white layer of superior colliculus, and higher basal D(1) receptor levels in several areas of hippocampus and thalamus, and substantia nigra pars reticulata. Taken together, these results suggest that an inherent high operant responding activity of LEW rats may have a role in the previous reported faster acquisition of opiate-reinforced behavior in operant self-administration paradigms under fixed-ratio schedules of reinforcement. In addition, a basal higher NMDA and D(1) receptor levels of LEW rats compared to F344 rats may participate in the neurochemical background that mediates the behavioral differences between both inbred rat strains.

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

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

Magnesium Lithospermate B Implicates 3'-5'-Cyclic Adenosine Monophosphate/Protein Kinase A Pathway and N-Methyl-d-Aspartate Receptors in an Experimental Traumatic Brain Injury.

PubMed

Chang, Chih-Zen; Wu, Shu-Chuan; Kwan, Aij-Lie; Lin, Chih-Lung

2015-10-01

Decreased 3'-5'-cyclic adenosine monophosphate (cAMP), protein kinase A (PKA), and increased N-methyl-d-aspartate (NMDA) related apoptosis were observed in traumatic brain injury (TBI). It is of interest to examine the effect of magnesium lithospermate B (MLB) on cAMP/PKA pathway and NMDAR in TBI. A rodent weight-drop TBI model was used. Administration of MLB was initiated 1 week before (precondition) and 24 hours later (reversal). Cortical homogenates were harvested to measure cAMP (enzyme-linked immunosorbent assay), soluble guanylyl cyclases, PKA and NMDA receptor-2β (Western blot). In addition, cAMP kinase antagonist and H-89 dihydrochloride hydrate were used to test MLB's effect on the cytoplasm cAMP/PKA pathway after TBI. Morphologically, vacuolated neuron and activated microglia were observed in the TBI groups but absent in the MLB preconditioning and healthy controls. Induced cAMP, soluble guanylyl cyclase α1, and PKA were observed in the MLB groups, when compared with the TBI group (P < 0.01) Administration of H-89 dihydrochloride hydrate reversed the effect of MLB on cortical PKA and NMDA-2β expression after TBI. This study showed that MLB exerted an antioxidant effect on the enhancement of cytoplasm cAMP and PKA. This compound also decreased NMDA-2β levels, which may correspond to its neuroprotective effects. This finding lends credence to the presumption that MLB modulates the NMDA-2β neurotoxicity through a cAMP-dependent mechanism in the pathogenesis of TBI. Copyright © 2015 Elsevier Inc. All rights reserved.

Disruption of social approach by MK-801, amphetamine, and fluoxetine in adolescent C57BL/6J mice.

PubMed

Moy, Sheryl S; Nonneman, Randal J; Shafer, Geoffrey O; Nikolova, Viktoriya D; Riddick, Natallia V; Agster, Kara L; Baker, Lorinda K; Knapp, Darin J

2013-01-01

Autism is a severe neurodevelopmental disorder, diagnosed on the basis of core behavioral symptoms. Although the mechanistic basis for the disorder is not yet known, genetic analyses have suggested a role for abnormal excitatory/inhibitory signaling systems in brain, including dysregulation of glutamatergic neurotransmission. In mice, the constitutive knockdown of NMDA receptors leads to social deficits, repetitive behavior, and self-injurious responses that reflect aspects of the autism clinical profile. However, social phenotypes differ with age: mice with reduced NMDA-receptor function exhibit hypersociability in adolescence, but markedly deficient sociability in adulthood. The present studies determined whether acute disruption of NMDA neurotransmission leads to exaggerated social approach, similar to that observed with constitutive disruption, in adolescent C57BL/6J mice. The effects of MK-801, an NMDA receptor antagonist, were compared with amphetamine, a dopamine agonist, and fluoxetine, a selective serotonin reuptake inhibitor, on performance in a three-chamber choice task. Results showed that acute treatment with MK-801 led to social approach deficits at doses without effects on entry numbers. Amphetamine also decreased social preference, but increased number of entries at every dose. Fluoxetine (10 mg/kg) had selective effects on social novelty preference. Withdrawal from a chronic ethanol regimen decreased activity, but did not attenuate sociability. Low doses of MK-801 and amphetamine were also evaluated in a marble-burying assay for repetitive behavior. MK-801, at a dose that did not disrupt sociability or alter entries, led to a profound reduction in marble-burying. Overall, these findings demonstrate that moderate alteration of NMDA, dopamine, or serotonin function can attenuate social preference in wild type mice. Copyright © 2012 Elsevier Inc. All rights reserved.

D-Serine and a glycine transporter inhibitor improve MK-801-induced cognitive deficits in a novel object recognition test in rats.

PubMed

Karasawa, Jun-Ichi; Hashimoto, Kenji; Chaki, Shigeyuki

2008-01-10

Compounds enhancing N-methyl-d-aspartate (NMDA) glutamate receptor function have been reported to improve cognitive deficits. Since cognitive deficits are considered to be the core symptom of schizophrenia, enhancing NMDA receptor function represents a promising approach to treating schizophrenia. In the present study, we investigated whether d-serine or a glycine transporter inhibitor N-[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl]sarcosine (NFPS), both of which enhance NMDA receptor function, could improve MK-801-induced cognitive deficits in rats, and compared their effects with those of the atypical antipsychotic clozapine and of the typical antipsychotic haloperidol. To assess cognitive function, we used a novel object recognition test in rats that measured spontaneous exploratory activity of a novel object when paired with a familiar object. We then evaluated the effects of the compounds on cognitive deficits induced by treatment with MK-801, the NMDA receptor antagonist. Pretreatment with clozapine (1, 5 mg/kg, i.p.) but not haloperidol (0.03, 0.1 mg/kg, i.p.) significantly improved MK-801-induced cognitive deficits. Pretreatment with D-serine at 800 mg/kg (i.p.) or NFPS (0.3, 1 mg/kg, i.p.) significantly improved MK-801-induced cognitive deficits under this test paradigm. These findings suggest that impaired preference for novel objects induced by MK-801 in the novel object recognition test could be a useful animal model for evaluating the efficacy of compounds targeting the cognitive deficits observed in schizophrenic patients. The results also suggest that enhancing NMDA receptor function is an effective way for treating the cognitive deficits associated with schizophrenia.

Control of βAR- and N-methyl-D-aspartate (NMDA) Receptor-Dependent cAMP Dynamics in Hippocampal Neurons

PubMed Central

Chay, Andrew; Zamparo, Ilaria; Koschinski, Andreas; Zaccolo, Manuela; Blackwell, Kim T.

2016-01-01

Norepinephrine, a neuromodulator that activates β-adrenergic receptors (βARs), facilitates learning and memory as well as the induction of synaptic plasticity in the hippocampus. Several forms of long-term potentiation (LTP) at the Schaffer collateral CA1 synapse require stimulation of both βARs and N-methyl-D-aspartate receptors (NMDARs). To understand the mechanisms mediating the interactions between βAR and NMDAR signaling pathways, we combined FRET imaging of cAMP in hippocampal neuron cultures with spatial mechanistic modeling of signaling pathways in the CA1 pyramidal neuron. Previous work implied that cAMP is synergistically produced in the presence of the βAR agonist isoproterenol and intracellular calcium. In contrast, we show that when application of isoproterenol precedes application of NMDA by several minutes, as is typical of βAR-facilitated LTP experiments, the average amplitude of the cAMP response to NMDA is attenuated compared with the response to NMDA alone. Models simulations suggest that, although the negative feedback loop formed by cAMP, cAMP-dependent protein kinase (PKA), and type 4 phosphodiesterase may be involved in attenuating the cAMP response to NMDA, it is insufficient to explain the range of experimental observations. Instead, attenuation of the cAMP response requires mechanisms upstream of adenylyl cyclase. Our model demonstrates that Gs-to-Gi switching due to PKA phosphorylation of βARs as well as Gi inhibition of type 1 adenylyl cyclase may underlie the experimental observations. This suggests that signaling by β-adrenergic receptors depends on temporal pattern of stimulation, and that switching may represent a novel mechanism for recruiting kinases involved in synaptic plasticity and memory. PMID:26901880

The BDNF Val66Met polymorphism impairs synaptic transmission and plasticity in the infralimbic medial prefrontal cortex

PubMed Central

Pattwell, Siobhan S.; Bath, Kevin G.; Perez-Castro, Rosalia; Lee, Francis S.; Chao, Moses V.; Ninan, Ipe

2012-01-01

The brain-derived neurotrophic factor (BDNF) Val66Met polymorphism is a common human single nucleotide polymorphism (SNP) that affects the regulated release of BDNF, and has been implicated in affective disorders and cognitive dysfunction. A decreased activation of the infralimbic medial prefrontal cortex (IL-mPFC), a brain region critical for the regulation of affective behaviors, has been described in BDNFMet carriers. However, it is unclear whether and how the Val66Met polymorphism affects the IL-mPFC synapses. Here we report that spike timing-dependent plasticity (STDP) was absent in the IL-mPFC pyramidal neurons from BDNFMet/Met mice, a mouse that recapitulates the specific phenotypic properties of the human BDNF Val66Met polymorphism. Also, we observed a decrease in N-methyl-D-aspartic acid (NMDA) and γ-aminobutyric acid (GABA) receptor-mediated synaptic transmission in the pyramidal neurons of BDNFMet/Met mice. While BDNF enhanced non-NMDA receptor transmission and depressed GABA receptor transmission in the wild-type mice, both effects were absent in BDNFMet/Met mice after BDNF treatment. Indeed, exogenous BDNF reversed the deficits in STDP and NMDA receptor transmission in BDNFMet/Met neurons. BDNF-mediated selective reversal of the deficit in plasticity and NMDA receptor transmission, but its lack of effect on GABA and non-NMDA receptor transmission in BDNFMet/Met mice, suggests separate mechanisms of Val66Met polymorphism upon synaptic transmission. The effect of the Val66Met polymorphism on synaptic transmission and plasticity in the IL-mPFC represents a mechanism to account for this SNP's impact on affective disorders and cognitive dysfunction. PMID:22396415

External pH changes affect NMDA-evoked and spontaneous release of cholecystokinin, somatostatin and noradrenaline from rat cerebrocortical nerve endings.

PubMed

Gemignani, Anita; Paudice, Paolo; Longordo, Fabio; Raiteri, Maurizio

2004-10-01

It was previously reported that the K+-evoked release of somatostatin-like immunoreactivity (SRIF-LI) and of cholecystokinin-like immunoreactivity (CCK-LI) from superfused rat cerebrocortical synaptosomes can be enhanced by NMDA or D-serine alone. We here studied the effects of extraterminal pH changes on SRIF-LI and CCK-LI release. Lowering pH from 7.4 to 6.9 or 6.4 abolished the effects of NMDA or D-serine on the K+-evoked peptide release. Identical results were obtained when external pH was raised to 8 or 8.7. Sudden alkalinization of the superfusion medium, in absence of K+-depolarization, induced SRIF-LI or CCK-LI release which was insensitive to NMDA. Based on experiments in Ca2+-free medium and with voltage-sensitive Ca2+ channel (VSCC) blockers, the pH 8.7-induced release of SRIF-LI and CCK-LI was only in part (30-50%) dependent on external Ca2+ and Ca2+ channel activation. In contrast, the alkalinization-evoked release of [3H]noradrenaline was highly sensitive to external Ca2+ removal and to blockade of Ca2+ channels with omega-conotoxins. The pH 8.7-evoked SRIF-LI and CCK-LI was about halved in synaptosomes intoxicated with botulinum toxin C1. The results suggest that the pH-sensitive NMDA receptors mediating somatostatin and cholecystokinin release contain NR1 subunits lacking the exon-5 cassette. Alkalinization represents a novel releasing stimulus which elicits neuropeptide release in part by conventional exocytosis and largely by an external Ca2+-independent mechanism. Differently, the release of noradrenaline provoked by alkalinization occurs entirely by conventional exocytosis.

Disruption of social approach by MK-801, amphetamine, and fluoxetine in adolescent C57BL/6J mice

PubMed Central

Moy, Sheryl S.; Nonneman, Randal J.; Shafer, Geoffrey O.; Nikolova, Viktoriya D.; Riddick, Natallia V.; Agster, Kara L.; Baker, Lorinda K.; Knapp, Darin J.

2012-01-01

Autism is a severe neurodevelopmental disorder, diagnosed on the basis of core behavioral symptoms. Although the mechanistic basis for the disorder is not yet known, genetic analyses have suggested a role for abnormal excitatory/inhibitory signaling systems in brain, including dysregulation of glutamatergic neurotransmission. In mice, the constitutive knockdown of NMDA receptors leads to social deficits, repetitive behavior, and self-injurious responses that reflect aspects of the autism clinical profile. However, social phenotypes differ with age: mice with reduced NMDA-receptor function exhibit hypersociability in adolescence, but markedly deficient sociability in adulthood. The present studies determined whether acute disruption of NMDA neurotransmission leads to exaggerated social approach, similar to that observed with constitutive disruption, in adolescent C57BL/6J mice. The effects of MK-801, an NMDA receptor antagonist, were compared with amphetamine, a dopamine agonist, and fluoxetine, a selective serotonin reuptake inhibitor, on performance in a three-chamber choice task. Results showed that acute treatment with MK-801 led to social approach deficits at doses without effects on entry numbers. Amphetamine also decreased social preference, but increased number of entries at every dose. Fluoxetine (10 mg/kg) had selective effects on social novelty preference. Withdrawal from a chronic ethanol regimen decreased activity, but did not attenuate sociability. Low doses of MK-801 and amphetamine were also evaluated in a marble-burying assay for repetitive behavior. MK-801, at a dose that did not disrupt sociability or alter entries, led to a profound reduction in marble-burying. Overall, these findings demonstrate that moderate alteration of NMDA, dopamine, or serotonin function can attenuate social preference in wild type mice. PMID:22898204

Effects of a glycine transporter-1 inhibitor and D-serine on MK-801-induced immobility in the forced swimming test in rats.

PubMed

Kawaura, Kazuaki; Koike, Hiroyuki; Kinoshita, Kohnosuke; Kambe, Daiji; Kaku, Ayaka; Karasawa, Jun-ichi; Chaki, Shigeyuki; Hikichi, Hirohiko

2015-02-01

Glutamatergic dysfunction, particularly the hypofunction of N-methyl-D-aspartate (NMDA) receptors, is involved in the pathophysiology of schizophrenia. The positive modulation of the glycine site on the NMDA receptor has been proposed as a novel therapeutic approach for schizophrenia. However, its efficacy against negative symptoms, which are poorly managed by current medications, has not been fully addressed. In the present study, the effects of the positive modulation of the glycine site on the NMDA receptor were investigated in an animal model of negative symptoms of schizophrenia. The subchronic administration of MK-801 increased immobility in the forced swimming test in rats without affecting spontaneous locomotor activity. The increased immobility induced by MK-801 was attenuated by the atypical antipsychotic clozapine but not by either the typical antipsychotic haloperidol or the antidepressant imipramine, indicating that the increased immobility induced by subchronic treatment with MK-801 in the forced swimming test may represent a negative symptom of schizophrenia. Likewise, positive modulation of the glycine sites on the NMDA receptor using an agonist for the glycine site, D-serine, and a glycine transporter-1 inhibitor, N-[(3R)-3-([1,1'-biphenyl]-4-yloxy)-3-(4-fluorophenyl)propyl]-N-methylglycine hydrochloride (NFPS), significantly reversed the increase in immobility in MK-801-treated rats without reducing the immobility time in vehicle-treated rats. The present results show that the stimulation of the NMDA receptor through the glycine site on the receptor either directly with D-serine or by blocking glycine transporter-1 attenuates the immobility elicited by the subchronic administration of MK-801 and may be potentially useful for the treatment of negative symptoms of schizophrenia. Copyright © 2014 Elsevier B.V. All rights reserved.

Alpha7 Nicotinic Acetylcholine Receptors Play a Predominant Role in the Cholinergic Potentiation of N-Methyl-D-Aspartate Evoked Firing Responses of Hippocampal CA1 Pyramidal Cells

PubMed Central

Bali, Zsolt K.; Nagy, Lili V.; Hernádi, István

2017-01-01

The aim of the present study was to identify in vivo electrophysiological correlates of the interaction between cholinergic and glutamatergic neurotransmission underlying memory. Extracellular spike recordings were performed in the hippocampal CA1 region of anesthetized rats in combination with local microiontophoretic administration of N-methyl-D-aspartate (NMDA) and acetylcholine (ACh). Both NMDA and ACh increased the firing rate of the neurons. Furthermore, the simultaneous delivery of NMDA and ACh resulted in a more pronounced excitatory effect that was superadditive over the sum of the two mono-treatment effects and that was explained by cholinergic potentiation of glutamatergic neurotransmission. Next, animals were systemically treated with scopolamine or methyllycaconitine (MLA) to assess the contribution of muscarinic ACh receptor (mAChR) or α7 nicotinic ACh receptor (nAChR) receptor-mediated mechanisms to the observed effects. Scopolamine totally inhibited ACh-evoked firing, and attenuated the firing rate increase evoked by simultaneous application of NMDA and ACh. However, the superadditive nature of the combined effect was preserved. The α7 nAChR antagonist MLA robustly decreased the firing response to simultaneous application of NMDA and ACh, suspending their superadditive effect, without modifying the tonic firing rate increasing effect of ACh. These results provide the first in vivo electrophysiological evidence that, in the hippocampal CA1 region, α7 nAChRs contribute to pyramidal cell activity mainly through potentiation of glutamatergic signaling, while the direct cholinergic modulation of tonic firing is notably mediated by mAChRs. Furthermore, the present findings also reveal cellular physiological correlates of the interplay between cholinergic and glutamatergic agents in behavioral pharmacological models of cognitive decline. PMID:28928637

D-Cycloserine improves functional outcome after traumatic brain injury with wide therapeutic window

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

Adeleye, A.; Biegon, A.; Adeleye, A.

It has been long thought that hyperactivation of N-methyl-D-aspartate (NMDA) receptors underlies neurological decline after traumatic brain injury. However, all clinical trials with NMDA receptor antagonists failed. Since NMDA receptors are down-regulated from 4 h to 2 weeks after brain injury, activation at 24 h, rather than inhibition, of these receptors, was previously shown to be beneficial in mice. Here, we tested the therapeutic window, dose regimen and mechanism of action of the NMDA receptor partial agonist d-cycloserine (DCS) in traumatic brain injury. Male mice were subjected to trauma using a weight-drop model, and administered 10 mg/kg (i.p.) DCS ormore » vehicle once (8, 16, 24, or 72 h) twice (24 and 48 h) or three times (24, 48 and 72 h). Functional recovery was assessed for up to 60 days, using a Neurological Severity Score that measures neurobehavioral parameters. In all groups in which treatment was begun at 24 or 72 h neurobehavioral function was significantly better than in the vehicle-treated groups. Additional doses, on days 2 and 3 did not further improve recovery. Mice treated at 8 h or 16 h post injury did not differ from the vehicle-treated controls. Co-administration of the NMDA receptor antagonist MK-801 completely blocked the protective effect of DCS given at 24 h. Infarct volume measured by 2,3,5-triphenyltetrazolium chloride staining at 48 h or by cresyl violet at 28 days was not affected by DCS treatment. Since DCS is used clinically for other indications, the present study offers a novel approach for treating human traumatic brain injury with a therapeutic window of at least 24 h.« less

Properties of single NMDA receptor channels in human dentate gyrus granule cells

PubMed Central

Lieberman, David N; Mody, Istvan

1999-01-01

Cell-attached single-channel recordings of NMDA channels were carried out in human dentate gyrus granule cells acutely dissociated from slices prepared from hippocampi surgically removed for the treatment of temporal lobe epilepsy (TLE). The channels were activated by l-aspartate (250–500 nm) in the presence of saturating glycine (8 μm). The main conductance was 51 ± 3 pS. In ten of thirty granule cells, clear subconductance states were observed with a mean conductance of 42 ± 3 pS, representing 8 ± 2% of the total openings. The mean open times varied from cell to cell, possibly owing to differences in the epileptogenicity of the tissue of origin. The mean open time was 2.70 ± 0.95 ms (range, 1.24–4.78 ms). In 87% of the cells, three exponential components were required to fit the apparent open time distributions. In the remaining neurons, as in control rat granule cells, two exponentials were sufficient. Shut time distributions were fitted by five exponential components. The average numbers of openings in bursts (1.74 ± 0.09) and clusters (3.06 ± 0.26) were similar to values obtained in rodents. The mean burst (6.66 ± 0.9 ms), cluster (20.1 ± 3.3 ms) and supercluster lengths (116.7 ± 17.5 ms) were longer than those in control rat granule cells, but approached the values previously reported for TLE (kindled) rats. As in rat NMDA channels, adjacent open and shut intervals appeared to be inversely related to each other, but it was only the relative areas of the three open time constants that changed with adjacent shut time intervals. The long openings of human TLE NMDA channels resembled those produced by calcineurin inhibitors in control rat granule cells. Yet the calcineurin inhibitor FK-506 (500 nm) did not prolong the openings of human channels, consistent with a decreased calcineurin activity in human TLE. Many properties of the human NMDA channels resemble those recorded in rat hippocampal neurons. Both have similar slope conductances, five exponential shut time distributions, complex groupings of openings, and a comparable number of openings per grouping. Other properties of human TLE NMDA channels correspond to those observed in kindling; the openings are considerably long, requiring an additional exponential component to fit their distributions, and inhibition of calcineurin is without effect in prolonging the openings. PMID:10373689

[Neuroprotective effect of erigeron breviscapus (vant) hand-mazz on NMDA-induced retinal neuron injury in the rats].

PubMed

Shi, Jingming; Jiag, Youqin; Liu, Xuyang

2004-07-01

To investigate if Erigeron Breviscapus (vant) Hand-Mazz (EBHM) has a neuroprotective effect against NMDA-induced neuron death in retinal ganglion cell layer (RGCL). Sixty healthy SD rats were randomly divided into four groups. 6 animals were in normal control group (group A). The others were divided as group B (EBHM group), group C (normal saline+NMDA group), group D (EBHM+NMDA group). Each group has 18 rats. 10 nmol NMDA was chosen for intravitreal injection to cause partial damage of the neurons in RGCL in the right eyes of Groups C and D. Same volume PBS was intravitreal injected in the left eyes as self-control. Groups B and D were pre-treated intraperitoneally with 6% EBHM solution at a dose of 15 mg x 100 g(-1) x d(-1) seven days before and after NMDA treatment. Group C were administrated intraperitoneally with 0.9% normal saline at the same time of EBHM injection. Rats were sacrificed in 4, 7, 14 days after NMDA treatment. Flat preparation of whole retinas were stained with 0.5% cresyl violet and neuron counting in RGCL from both eyes. Each subgroup has 6 rats. There was no significant difference between the right eye and the left eye of neuron counting from RGCL in normal control group (group A) (P=0.200). There was no significant difference between normal control group and EBHM group either in the right eyes or in the left eye in 4 days, 7 days and 14 days respectively after intravitreal injection of 10 nmol NMDA in group C and group D. (P=0.636, P=0.193). Neuron counting from RGCL of group C and group D were significant decreased in the NMDA-treated eyes in 4 days, 7 days and 14 days after intravitreal injection (P < 0.001). There ws no significant difference between self-control eyes and normal control group (P > 0.05). Neuron counting was significantly higher in the EBHM+NMDA group than normal saline+NMDA group at 14 days after intraviteal injection (P=0.044). However,it is obvious that the difference was still significant between normal control group and EBHM+NMDA group (P < 0.05). EBHM has no effect on neuron counting of RGCL when administered alone in normal rats. It is suggested that EBHM has partial protective effect on NMDA-induced neuron loss in RGCL in the rat.

Antinociceptive actions of honokiol and magnolol on glutamatergic and inflammatory pain

PubMed Central

2009-01-01

The antinociceptive effects of honokiol and magnolol, two major bioactive constituents of the bark of Magnolia officinalis, were investigated on animal paw licking responses and thermal hyperalgesia induced by glutamate receptor agonists including glutamate, N-methyl-D-aspartate (NMDA), and metabotropic glutamate 5 receptor (mGluR5) activator (RS)-2-chloro-5-hydroxyphenylglycine (CHPG), as well as inflammatory mediators such as substance P and prostaglandin E2 (PGE2) in mice. The actions of honokiol and magnolol on glutamate-induced c-Fos expression in the spinal cord dorsal horn were also examined. Our data showed that honokiol and magnolol blocked glutamate-, substance P- and PGE2-induced inflammatory pain with similar potency and efficacy. Consistently, honokiol and magnolol significantly decreased glutamate-induced c-Fos protein expression in superficial (I-II) laminae of the L4-L5 lumbar dorsal horn. However, honokiol was more selective than magnolol for inhibition of NMDA-induced licking behavioral and thermal hyperalgesia. In contrast, magnolol was more potent to block CHPG-mediated thermal hyperalgesia. These results demonstrate that honokiol and magnolol effectively decreased the inflammatory pain. Furthermore, their different potency on inhibition of nociception provoked by NMDA receptor and mGluR5 activation should be considered. PMID:19832997

MDMA-induced loss of parvalbumin interneurons within the dentate gyrus is mediated by 5HT2A and NMDA receptors

PubMed Central

Collins, Stuart A.; Gudelsky, Gary A.; Yamamoto, Bryan K.

2015-01-01

MDMA is a widely abused psychostimulant which causes a rapid and robust release of the monoaminergic neurotransmitters dopamine and serotonin. Recently, it was shown that MDMA increases extracellular glutamate concentrations in the dorsal hippocampus, which is dependent on serotonin release and 5HT2A/2C receptor activation. The increased extracellular glutamate concentration coincides with a loss of parvalbumin-immunoreactive (PV-IR) interneurons of the dentate gyrus region. Given the known susceptibility of PV interneurons to excitotoxicity, we examined whether MDMA-induced increases in extracellular glutamate in the dentate gyrus are necessary for the loss of PV cells in rats. Extracellular glutamate concentrations increased in the dentate gyrus during systemic and local administration of MDMA. Administration of the NMDA receptor antagonist, MK-801, during systemic injections of MDMA, prevented the loss of PV-IR interneurons seen 10 days after MDMA exposure. Local administration of MDL100907, a selective 5HT2A receptor antagonist, prevented the increases in glutamate caused by reverse dialysis of MDMA directly into the dentate gyrus and prevented the reduction of PV-IR. These findings provide evidence that MDMA causes decreases in PV within the dentate gyrus through a 5HT2A receptor-mediated increase in glutamate and subsequent NMDA receptor activation. PMID:25936514

Enhanced NMDA receptor tyrosine phosphorylation and increased brain injury following neonatal hypoxia–ischemia in mice with neuronal Fyn overexpression

PubMed Central

Knox, Renatta; Zhao, Chong; Miguel-Perez, Dario; Wang, Steven; Yuan, Jinwei; Ferriero, Donna; Jiang, Xiangning

2013-01-01

The Src family kinases (SFKs) Src and Fyn are implicated in hypoxic–ischemic (HI) injury in the developing brain. However, it is unclear how these particular SFKs contribute to brain injury. Using neuron-specific Fyn overexpressing (OE) mice, we investigated the role of neuronal Fyn in neonatal brain HI. Wild type (WT) and Fyn OE mice were subjected to HI using the Vannucci model at postnatal day 7. Brains were scored five days later for evaluation of damage using cresyl violet and iron staining. Western blotting with postsynaptic density (PSD)-associated synaptic membrane proteins and co-immunoprecipitation with cortical lysates were performed at various time points after HI to determine NMDA receptor tyrosine phosphorylation and Fyn kinase activity. Fyn OE mice had significantly higher mortality and brain injury compared to their WT littermates. Neuronal Fyn overexpression led to sustained NR2A and NR2B tyrosine phosphorylation and enhanced NR2B phosphorylation at tyrosine (Y) 1472 and Y1252 in synaptic membranes. These early changes correlated with higher calpain activity 24 h after HI in Fyn OE mice relative to WT animals. Our findings suggest a role for Fyn kinase in neuronal death after neonatal HI, possibly via up-regulation of NMDA receptor tyrosine phosphorylation. PMID:23127881

Group III mGlu receptor agonists potentiate the anticonvulsant effect of AMPA and NMDA receptor block.

PubMed

De Sarro, Giovambattista; Chimirri, Alba; Meldrum, Brian S

2002-09-06

We report the anticonvulsant action in DBA/2 mice of two mGlu Group III receptor agonists: (R,S)-4-phosphonophenylglycine, (R,S)-PPG, a compound with moderate mGlu8 selectivity, and of (1S,3R,4S)-1-aminocyclopentane-1,2,4-tricarboxylic acid, ACPT-1, a selective agonist for mGlu4alpha receptors. Both compounds, given intracerebroventricularly at doses which did not show marked anticonvulsant activity, produced a consistent shift to the left of the dose-response curves (i.e. enhanced the anticonvulsant properties) of 1-(4'-aminophenyl)-3,5-dihydro-7,8-dimethoxy-4H-2,3-benzodiazepin-4-one hydrochloride, CFM-2, a noncompetitive AMPA receptor antagonist, and 3-((+/-)-2-carboxypiperazin-4-yl)-1-phosphonic acid, CPPene, a competitive NMDA receptor antagonist, in DBA/2 mice. In addition, (R,S)-PPG and ACPT-1 administered intracerebroventricularly prolonged the time course of the anticonvulsant properties of CFM-2 (33 micromol/kg, i.p.) and CPPene (3.3 micromol/kg, i.p.) administered intraperitoneally. We conclude that modest reduction of synaptic glutamate release by activation of Group III metabotropic receptors potentiates the anticonvulsant effect of AMPA and NMDA receptor blockade. Copyright 2002 Elsevier Science B.V.

Activation of NOX2 by the stimulation of ionotropic and metabotropic glutamate receptors contributes to glutamate neurotoxicity in vivo through the production of reactive oxygen species and calpain activation.

PubMed

Guemez-Gamboa, Alicia; Estrada-Sánchez, Ana María; Montiel, Teresa; Páramo, Blanca; Massieu, Lourdes; Morán, Julio

2011-11-01

Prolonged activation of glutamate receptors leads to excitotoxicity. Several processes such as reactive oxygen species (ROS) production and activation of the calcium-dependent protease, calpain, contribute to glutamate-induced damage. It has been suggested that the ROS-producing enzyme, NADPH oxidase (NOX), plays a role in excitotoxicity. Studies have reported NOX activation after NMDA receptor stimulation during excitotoxic damage, but the role of non-NMDA and metabotropic receptors is unknown. We evaluated the roles of different glutamate receptor subtypes on NOX activation and neuronal death induced by the intrastriatal administration of glutamate in mice. In wild-type mice, NOX2 immunoreactivity in neurons and microglia was stimulated by glutamate administration, and it progressively increased as microglia became activated; calpain activity was also induced. By contrast, mice lacking NOX2 were less vulnerable to excitotoxicity, and there was reduced ROS production and protein nitrosylation, microglial reactivity, and calpain activation. These results suggest that NOX2 is stimulated by glutamate in neurons and reactive microglia through the activation of ionotropic and metabotropic receptors. Neuronal damage involves ROS production by NOX2, which, in turn, contributes to calpain activation.

Synaptic potentials in respiratory neurones during evoked phase switching after NMDA receptor blockade in the cat

PubMed Central

Pierrefiche, O; Haji, A; Foutz, A S; Takeda, R; Champagnat, J; Denavit-Saubié, M

1998-01-01

Blockade of NMDA receptors by dizocilpine impairs the inspiratory off-switch (IOS) of central origin but not the IOS evoked by stimulation of sensory afferents. To investigate whether this difference was due to the effects of different patterns of synaptic interactions on respiratory neurones, we stimulated electrically the superior laryngeal nerve (SLN) or vagus nerve in decerebrate cats before and after i.v. administration of dizocilpine, whilst recording intracellularly. Phrenic nerve responses to ipsilateral SLN or vagal stimulation were: at mid-inspiration, a transient inhibition often followed by a brief burst of activity; at late inspiration, an IOS; and at mid-expiration, a late burst of activity. In all neurones (n = 16), SLN stimulation at mid-inspiration evoked an early EPSP during phase 1 (latency to the arrest of phrenic nerve activity), followed by an IPSP in inspiratory (I) neurones (n = 8) and by a wave of EPSPs in post-inspiratory (PI) neurones (n = 8) during phase 2 (inhibition of phrenic activity). An EPSP in I neurones and an IPSP in PI neurones occurred during phase 3 (brief phrenic burst) following phase 2. Evoked IOS was associated with a fast (phase 1) activation of PI neurones, whereas during spontaneous IOS, a progressive (30-50 ms) depolarization of PI neurones preceded the arrest of phrenic activity. Phase 3 PSPs were similar to those occurring during the burst of activity seen at the start of spontaneous inspiration. Dizocilpine did not suppress the evoked phrenic inhibition and the late burst of activity. The shapes and timing of the evoked PSPs and the changes in membrane potential in I and PI neurones during the phase transition were not altered. We hypothesize that afferent sensory pathways not requiring NMDA receptors (1) terminate inspiration through a premature activation of PI neurones, and (2) evoke a late burst of phrenic activity which might be the first stage of the inspiratory on-switch. PMID:9508816

NMDA receptor agonists reverse impaired psychomotor and cognitive functions associated with hippocampal Hbegf-deficiency in mice.

PubMed

Sasaki, Keita; Omotuyi, Olaposi Idowu; Ueda, Mutsumi; Shinohara, Kazuyuki; Ueda, Hiroshi

2015-12-04

Structural and functional changes of the hippocampus are correlated with psychiatric disorders and cognitive dysfunctions. Genetic deletion of heparin-binding epidermal growth factor-like growth factor (HB-EGF), which is predominantly expressed in cortex and hippocampus, also causes similar psychiatric and cognitive dysfunctions, accompanying down-regulated NMDA receptor signaling. However, little is known of such dysfunctions in hippocampus-specific Hbegf cKO mice. We successfully developed hippocampus-specific cKO mice by crossbreeding floxed Hbegf and Gng7-Cre knock-in mice, as Gng7 promoter-driven Cre is highly expressed in hippocampal neurons as well as striatal medium spiny neurons. In mice lacking hippocampus Hbegf gene, there was a decreased neurogenesis in the subgranular zone (SGZ) of the dentate gyrus as well as down-regulation of PSD-95/NMDA-receptor-NR1/NR2B subunits and related NMDA receptor signaling. Psychiatric, social-behavioral and cognitive abnormalities were also observed in hippocampal cKO mice. Interestingly, D-cycloserine and nefiracetam, positive allosteric modulators (PAMs) of NMDA receptor reversed the apparent reduction in NMDA receptor signaling and most behavioral abnormalities. Furthermore, decreased SGZ neurogenesis in hippocampal cKO mice was reversed by nefiracetam. The present study demonstrates that PAMs of NMDA receptor have pharmacotherapeutic potentials to reverse down-regulated NMDA receptor signaling, neuro-socio-cognitive abnormalities and decreased neurogenesis in hippocampal cKO mice.

Role of the JAKs/STATs pathway in the intracellular calcium changes induced by interleukin-6 in hippocampal neurons.

PubMed

Orellana, D I; Quintanilla, R A; Gonzalez-Billault, C; Maccioni, R B

2005-11-01

Recent studies show that inflammation has an active role in the onset of neurodegenerative diseases. It is known that in response to extracellular insults microglia and/or astrocytes produce inflammatory agents. These contribute to the neuropathological events in the aging process and neuronal degeneration. Interleukin-6 (IL-6) has been involved in the pathogenesis of neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases. Here, we show that IL-6 treatment of rat hippocampal neurons increases the calcium influx via NMDA-receptor, an effect that is prevented by the specific NMDA receptor antagonist MK-801 (dizocilpine). We also show that this calcium influx is mediated by the JAKs/STATs pathway, since the inhibitor of JAKs/STATs pathway, JAK 3 inhibitor, blocks calcium influx even in the presence of IL-6. This increase in calcium signal was dependent on external sources, since this signal was not observed in the presence of EGTA. Additional studies indicate that the increase in cytosolic calcium induces tau protein hyperphosphorylation, as revealed by using specific antibodies against Alzheimer phosphoepitopes. This anomalous tau hyperphosphorylation was dependent on both the JAKs/STATs pathway and NMDA receptor. These results suggest that IL-6 would induce a cascade of molecular events that produce a calcium influx through NMDA receptors, mediated by the JAKs/STATs pathway, which subsequently modifies the tau hyperphosphorylation patterns.

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.

Antidepressant-like effect of folic acid: Involvement of NMDA receptors and L-arginine-nitric oxide-cyclic guanosine monophosphate pathway.

PubMed

Brocardo, Patrícia de Souza; Budni, Josiane; Lobato, Kelly Ribas; Kaster, Manuella Pinto; Rodrigues, Ana Lúcia S

2008-11-19

Antidepressant-like activity of folic acid in forced swimming test and in the tail suspension test was demonstrated previously by our group. In this study we investigated the involvement of N-methyl-d-aspartate (NMDA) receptors and l-arginine-nitric oxide (NO)-cyclic guanosine monophosphate pathway in its antidepressant-like effect in the forced swimming test in mice. The antidepressant-like effect of folic acid (10 nmol/site, i.c.v.) was prevented by the pretreatment of mice with NMDA (0.1 pmol/site, i.c.v.), l-arginine (750 mg/kg, i.p., substrate for nitric oxide synthase), S-nitroso-N-acetyl-penicillamine (SNAP, 25 microg/site, i.c.v, a NO donor) or sildenafil (5 mg/kg, i.p., phosphodiesterase 5 inhibitor). The administration of 7-nitroindazole (25 and 50 mg/kg, i.p., a specific neuronal nitric oxide synthase (nNOS) inhibitor) or methylene blue (20 mg/kg, i.p., direct inhibitor of both nitric oxide synthase and soluble guanylate cyclase) in combination with a sub-effective dose of folic acid (1 nmol/site, i.c.v.) reduced the immobility time in the FST as compared with either drug alone. Together the results suggest that the antidepressant-like effect of folic acid in the forced swimming test is dependent on an inhibition of either NMDA receptors or NO and cGMP synthesis.

Factors Underlying Bursting Behavior in a Network of Cultured Hippocampal Neurons Exposed to Zero Magnesium

PubMed Central

Mangan, Patrick S.; Kapur, Jaideep

2010-01-01

Factors contributing to reduced magnesium-induced neuronal action potential bursting were investigated in primary hippocampal cell culture at high and low culture density. In nominally zero external magnesium medium, pyramidal neurons from high-density cultures produced recurrent spontaneous action potential bursts superimposed on prolonged depolarizations. These bursts were partially attenuated by the NMDA receptor antagonist D-APV. Pharmacological analysis of miniature excitatory postsynaptic currents (EPSCs) revealed 2 components: one sensitive to D-APV and another to the AMPA receptor antagonist DNQX. The components were kinetically distinct. Participation of NMDA receptors in reduced magnesium-induced synaptic events was supported by the localization of the NR1 subunit of the NMDA receptor with the presynaptic vesicular protein synaptophysin. Presynaptically, zero magnesium induced a significant increase in EPSC frequency likely attributable to increased neuronal hyperexcitability induced by reduced membrane surface charge screening. Mean quantal content was significantly increased in zero magnesium. Cells from low-density cultures did not exhibit action potential bursting in zero magnesium but did show increased EPSC frequency. Low-density neurons had less synaptophysin immunofluorescence and fewer active synapses as determined by FM1-43 analysis. These results demonstrate that multiple factors are involved in network bursting. Increased probability of transmitter release presynaptically, enhanced NMDA receptor-mediated excitability postsynaptically, and extent of neuronal interconnectivity contribute to initiation and maintenance of elevated network excitability. PMID:14534286

Central phencyclidine (PCP) receptor binding is glutamate dependent: evidence for a PCP/excitatory amino acid receptor (EAAR) complex

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

Loo, P.; Braunwalder, A.; Lehmann, J.

PCP and other dissociative anesthetica block the increase in neuronal firing rate evoked by the EAAR agonist, N-methyl-Daspartate. NMDA and other EAAs such as glutamate (glu) have not been previously shown to affect PCP ligand binding. In the present study, using once washed rat forebrain membranes, 10 ..mu..M-glu was found to increase the binding of (/sup 3/H)TCP, a PCP analog, to defined PCP recognition sites by 20%. Removal of glu and aspartate (asp) by extensive washing decreased TCP binding by 75-90%. In these membranes, 10 ..mu..M L-glu increased TCP binding 3-fold. This effect was stereospecific and evoked by other EAAsmore » with the order of activity, L-glu > D-asp > L- asp > NMDA > D-glu > quisqualate. Kainate, GABA, NE, DA, 5-HT, 2-chloroadenosine, oxotremorine and histamine had no effect on TCP binding at concentrations up to 100 ..mu..M. The effects of L-glu were attenuated by the NMDA-type receptor antagonist, 2-amino-7--phosphonoheptanoate (AP7; 10 ..mu..M-1 mM). These findings indicate that EAAS facilitate TCP binding, possibly through NMDA-type receptors. The observed interaction between the PCP receptor and EAARs may reflect the existence of a macromolecular receptor complex similar to that demonstrated for the benzodiazepines and GABA.« less

MK-801 and dextromethorphan block microglial activation and protect against methamphetamine-induced neurotoxicity.

PubMed

Thomas, David M; Kuhn, Donald M

2005-07-19

Methamphetamine causes long-term toxicity to dopamine nerve endings of the striatum. Evidence is emerging that microglia can contribute to the neuronal damage associated with disease, injury, or inflammation, but their role in methamphetamine-induced neurotoxicity has received relatively little attention. Lipopolysaccharide (LPS) and the neurotoxic HIV Tat protein, which cause dopamine neuronal toxicity after direct infusion into brain, cause activation of cultured mouse microglial cells as evidenced by increased expression of intracellular cyclooxygenase-2 and elevated secretion of tumor necrosis factor-alpha. MK-801, a non-competitive NMDA receptor antagonist that is known to protect against methamphetamine neurotoxicity, prevents microglial activation by LPS and HIV Tat. Dextromethorphan, an antitussive agent with NMDA receptor blocking properties, also prevents microglial activation. In vivo, MK-801 and dextromethorphan reduce methamphetamine-induced activation of microglia in striatum and they protect dopamine nerve endings against drug-induced nerve terminal damage. The present results indicate that the ability of MK-801 and dextromethorphan to protect against methamphetamine neurotoxicity is related to their common property as blockers of microglial activation.

Effect of the non-NMDA receptor antagonist GYKI 52466 on the microdialysate and tissue concentrations of amino acids following transient forebrain ischaemia.

PubMed

Arvin, B; Lekieffre, D; Graham, J L; Moncada, C; Chapman, A G; Meldrum, B S

1994-04-01

The effect of the non-N-methyl-D-aspartate (non-NMDA) receptor antagonist 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine hydrochloride (GYKI 52466) on ischaemia-induced changes in the microdialysate and tissue concentrations of glutamate, aspartate, and gamma-aminobutyric acid (GABA) was studied in rats. Twenty minutes of four-vessel occlusion resulted in a transient increase in microdialysate levels of glutamate, aspartate, and GABA in striatum, cortex, and hippocampus. Administration of GYKI 52466 (10 mg/kg bolus + 10 mg/kg/60 min intravenously starting 20 min before onset of ischaemia) inhibited ischaemia-induced increases in microdialysate glutamate and GABA in striatum without affecting the increases in hippocampus or cortex. Twenty minutes of four-vessel occlusion resulted in immediate small decreases and larger delayed (72 h) decreases in tissue levels of glutamate and aspartate. Transient increases in tissue levels of GABA were shown in all three structures at the end of the ischaemic period. At 72 h, after the ischaemic period, significantly reduced GABA levels were observed in striatum and hippocampus. GYKI 52466, given under identical conditions as above, augmented the ischaemia-induced decrease in striatal tissue levels of glutamate and aspartate, without significantly affecting the decreases in hippocampus and cortex. Twenty minutes of ischaemia resulted in a large increase in microdialysate dopamine in striatum. GYKI 52466 failed to inhibit this increase. Kainic acid (500 microM infused through the probe for 20 min) caused increases in microdialysate glutamate and aspartate in the striatum. GYKI 52466 (10 mg/kg bolus + 10 mg/kg/60 min) completely inhibited the kainic acid-induced glutamate release. In conclusion, the action of the non-NMDA antagonist, GYKI 52466, in the striatum is different from that in the cortex and hippocampus. The inhibition by GYKI 52466 of ischaemia-induced and kainate-induced increases in microdialysate glutamate concentration in the striatum may be related to the neuroprotection provided by GYKI 52466 in this region.

Synthesis and pharmacological evaluation of conformationally constrained glutamic acid higher homologues.

PubMed

Tamborini, Lucia; Cullia, Gregorio; Nielsen, Birgitte; De Micheli, Carlo; Conti, Paola; Pinto, Andrea

2016-11-15

Homologation of glutamic acid chain together with conformational constraint is a commonly used strategy to achieve selectivity towards different types of glutamate receptors. In the present work, starting from two potent and selective unnatural amino acids previously developed by us, we investigated the effects on the activity/selectivity profile produced by a further increase in the distance between the amino acidic moiety and the distal carboxylate group. Interestingly, the insertion of an aromatic ring as a spacer produced a low micromolar affinity NMDA ligand that might represent a lead for the development of a new class of NMDA antagonists. Copyright © 2016 Elsevier Ltd. All rights reserved.

Relative roles of different mechanisms of depression at the mouse endbulb of Held

PubMed Central

Yang, Hua; Xu-Friedman, Matthew A.

2010-01-01

Several mechanisms can underlie short-term synaptic depression, including vesicle depletion, receptor desensitization, and changes in presynaptic release probability. To determine which mechanisms affect depression under physiological conditions, we studied the synapse formed by auditory nerve fibers onto bushy cells in the anteroventral cochlear nucleus (the “endbulb of Held”) using voltage-clamp recordings of brain slices from P15–21 mice near physiological temperatures. Depression of both AMPA and NMDA EPSCs showed two phases of recovery. The fast component of depression for the AMPA EPSC was eliminated by cyclothiazide and aniracetam, suggesting it results from desensitization. The fast component of depression for the NMDA EPSC was reduced by the low-affinity antagonist L-AP5, suggesting it results from saturation. The remaining depression in AMPA and NMDA components is identical and therefore presynaptic in origin. It is likely to result from presynaptic vesicle depletion. Recovery from depression after trains of activity was slowed by the application of EGTA-AM, suggesting that the endbulb has a residual-calcium-dependent form of recovery. We developed a model that incorporates depletion, desensitization, and calcium-dependent recovery. This model replicated experimental findings over a range of experimental conditions. The model further indicated that desensitization plays only a minor role during prolonged activity, in large part because presynaptic release is so depleted. Thus, depletion appears to be the dominant mechanism of depression at the endbulb during normal activity. Furthermore, calcium-dependent recovery at the endbulb is critical to prevent complete run-down during high activity and to preserve the reliability of information transmission. PMID:18367696

Pharmacological Analysis of Ionotropic Glutamate Receptor Function in Neuronal Circuits of the Zebrafish Olfactory Bulb

PubMed Central

Tabor, Rico; Friedrich, Rainer W.

2008-01-01

Although synaptic functions of ionotropic glutamate receptors in the olfactory bulb have been studied in vitro, their roles in pattern processing in the intact system remain controversial. We therefore examined the functions of ionotropic glutamate receptors during odor processing in the intact olfactory bulb of zebrafish using pharmacological manipulations. Odor responses of mitral cells and interneurons were recorded by electrophysiology and 2-photon Ca2+ imaging. The combined blockade of AMPA/kainate and NMDA receptors abolished odor-evoked excitation of mitral cells. The blockade of AMPA/kainate receptors alone, in contrast, increased the mean response of mitral cells and decreased the mean response of interneurons. The blockade of NMDA receptors caused little or no change in the mean responses of mitral cells and interneurons. However, antagonists of both receptor types had diverse effects on the magnitude and time course of individual mitral cell and interneuron responses and, thus, changed spatio-temporal activity patterns across neuronal populations. Oscillatory synchronization was abolished or reduced by AMPA/kainate and NMDA receptor antagonists, respectively. These results indicate that (1) interneuron responses depend mainly on AMPA/kainate receptor input during an odor response, (2) interactions among mitral cells and interneurons regulate the total olfactory bulb output activity, (3) AMPA/kainate receptors participate in the synchronization of odor-dependent neuronal ensembles, and (4) ionotropic glutamate receptor-containing synaptic circuits shape odor-specific patterns of olfactory bulb output activity. These mechanisms are likely to be important for the processing of odor-encoding activity patterns in the olfactory bulb. PMID:18183297

Salicylate enables cochlear arachidonic-acid-sensitive NMDA receptor responses.

PubMed

Ruel, Jérôme; Chabbert, Christian; Nouvian, Régis; Bendris, Rim; Eybalin, Michel; Leger, Claude Louis; Bourien, Jérôme; Mersel, Marcel; Puel, Jean-Luc

2008-07-16

Currently, many millions of people treated for various ailments receive high doses of salicylate. Consequently, understanding the mechanisms by which salicylate induces tinnitus is an important issue for the research community. Behavioral testing in rats have shown that tinnitus induced by salicylate or mefenamate (both cyclooxygenase blockers) are mediated by cochlear NMDA receptors. Here we report that the synapses between the sensory inner hair cells and the dendrites of the cochlear spiral ganglion neurons express NMDA receptors. Patch-clamp recordings and two-photon calcium imaging demonstrated that salicylate and arachidonate (a substrate of cyclooxygenase) enabled the calcium flux and the neural excitatory effects of NMDA on cochlear spiral ganglion neurons. Salicylate also increased the arachidonate content of the whole cochlea in vivo. Single-unit recordings of auditory nerve fibers in adult guinea pig confirmed the neural excitatory effect of salicylate and the blockade of this effect by NMDA antagonist. These results suggest that salicylate inhibits cochlear cyclooxygenase, which increased levels of arachidonate. The increased levels of arachidonate then act on NMDA receptors to enable NMDA responses to glutamate that inner hair cells spontaneously release. This new pharmacological profile of salicylate provides a molecular mechanism for the generation of tinnitus at the periphery of the auditory system.

Long-lasting ibogaine protection against NMDA-induced convulsions in mice.

PubMed

Leal, M B; de Souza, D O; Elisabetsky, E

2000-08-01

Ibogaine, a putative antiaddictive drug, is remarkable in its apparent ability to downgrade withdrawal symptoms and drug craving for extended periods of time after a single dose. Ibogaine acts as a non-competitive NMDA receptor antagonist, while NMDA has been implicated in long lasting changes in neuronal function and in the physiological basis of drug addiction. The purpose of this study was to verify if persistent changes in NMDA receptors could be shown in vivo and in vitro after a single administration of ibogaine. The time course of ibogaine effects were examined on NMDA-induced seizures and [3H] MK-801 binding to cortical membranes in mice 30 min, 24, 48, and 72 h post treatment. Ibogaine (80 mg/kg, ip) was effective in inhibiting convulsions induced by NMDA at 24 and 72 hours post administration. Likewise, [3H] MK-801 binding was significantly decreased at 24 and 72 h post ibogaine. No significant differences from controls were found at 30 min or 48 h post ibogaine. This long lasting and complex pattern of modulation of NMDA receptors prompted by a single dose of ibogaine may be associated to its antiaddictive properties.

Class I histone deacetylase-mediated repression of the proximal promoter of the activity-regulated cytoskeleton-associated protein gene regulates its response to brain-derived neurotrophic factor.

PubMed

Fukuchi, Mamoru; Nakashima, Fukumi; Tabuchi, Akiko; Shimotori, Masataka; Tatsumi, Saori; Okuno, Hiroyuki; Bito, Haruhiko; Tsuda, Masaaki

2015-03-13

We examined the transcriptional regulation of the activity-regulated cytoskeleton-associated protein gene (Arc), focusing on BDNF-induced Arc expression in cultured rat cortical cells. Although the synaptic activity-responsive element (SARE), located -7 kbp upstream of the Arc transcription start site, responded to NMDA, BDNF, or FGF2, the proximal region of the promoter (Arc/-1679) was activated by BDNF or FGF2, but not by NMDA, suggesting the presence of at least two distinct Arc promoter regions, distal and proximal, that respond to extracellular stimuli. Specificity protein 4 (SP4) and early growth response 1 (EGR1) controlled Arc/-1679 transcriptional activity via the region encompassing -169 to -37 of the Arc promoter. We found that trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, significantly enhanced the inductive effects of BDNF or FGF2, but not those of NMDA on Arc expression. Inhibitors of class I/IIb HDACs, SAHA, and class I HDACs, MS-275, but not of class II HDACs, MC1568, enhanced BDNF-induced Arc expression. The enhancing effect of TSA was mediated by the region from -1027 to -1000 bp, to which serum response factor (SRF) and HDAC1 bound. The binding of HDAC1 to this region was reduced by TSA. Thus, Arc expression was suppressed by class I HDAC-mediated mechanisms via chromatin modification of the proximal promoter whereas the inhibition of HDAC allowed Arc expression to be markedly enhanced in response to BDNF or FGF2. These results contribute to our understanding of the physiological role of Arc expression in neuronal functions such as memory consolidation. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Interplay between presynaptic and postsynaptic activities is required for dendritic plasticity and synaptogenesis in the supraoptic nucleus.

PubMed

Chevaleyre, Vivien; Moos, Francoise C; Desarménien, Michel G

2002-01-01

Developing oxytocin and vasopressin (OT/AVP) supraoptic nucleus (SON) neurons positively autocontrol their electrical activity via dendritic release of their respective peptide. The effects of this autocontrol are maximum during the second postnatal week (PW2), when the dendritic arbor transiently increases and glutamatergic postsynaptic potentials appear. Here, we studied the role and interaction of dendritic OT/AVP release and glutamate release in dendritic plasticity and synaptogenesis in SON. In vivo treatment with the peptides antagonists or with an NMDA antagonist suppressed the transient increase in dendritic arbor of SON neurons at the beginning of PW2. Incubation of acute slices with these compounds decreased the dendritic arbor on a short time scale (3-8 hr) in slices of postnatal day 7 (P7) to P9 rats. Conversely, application of OT/AVP or NMDA increased dendritic branches in slices of P3-P6 rats. Their effects were inhibited by blockade of electrical activity, voltage-gated Ca2+ channels, or intracellular Ca2+ mobilization. They were also interdependent because both OT/AVP and NMDA (but not AMPA) receptor activation were required for increasing the dendritic arbor. Part of this interdependence probably results from a retrograde action of the peptides facilitating glutamate release. Finally, blocking OT/AVP receptors by in vivo treatment with the peptides antagonists during development decreased spontaneous glutamatergic synaptic activity recorded in young adults. These results show that an interplay between postsynaptic dendritic peptide release and presynaptic glutamate release is involved in the transient increase in dendritic arbor of SON neurons and indicate that OT/AVP are required for normal synaptogenesis of glutamatergic inputs in SON.

Antinociceptive Activity of Borreria verticillata: In vivo and In silico Studies

PubMed Central

Silva, Rosa H. M.; Lima, Nathália de Fátima M.; Lopes, Alberto J. O.; Vasconcelos, Cleydlenne C.; de Mesquita, José W. C.; de Mesquita, Ludmilla S. S.; Lima, Fernando C. V. M.; Ribeiro, Maria N. de S.; Ramos, Ricardo M.; Cartágenes, Maria do Socorro de S.; Garcia, João B. S.

2017-01-01

Borreria verticillata (L.) G. Mey. known vassourinha has antibacterial, antimalarial, hepatoprotective, antioxidative, analgesic, and anti-inflammatory, however, its antinociceptive action requires further studies. Aim of the study evaluated the antinociceptive activity of B. verticillata hydroalcoholic extract (EHBv) and ethyl acetate fraction (FAc) by in vivo and in silico studies. In vivo assessment included the paw edema test, writhing test, formalin test and tail flick test. Wistar rats and Swiss mice were divided into 6 groups and given the following treatments oral: 0.9% NaCl control group (CTRL), 10 mg/kg memantine (MEM), 10 mg/kg indomethacin (INDO), 500 mg/kg EHBv (EHBv 500), 25 mg/kg FAc (FAc 25) and 50 mg/kg FAc (FAc 50). EHBv, FAc 25 and 50 treatments exhibited anti-edematous and peripheral antinociceptive effects. For in silico assessment, compounds identified in FAc were subjected to molecular docking with COX-2, GluN1a and GluN2B. Ursolic acid (UA) was the compound with best affinity parameters (binding energy and inhibition constant) for COX-2, GluN1a, GluN2B, and was selected for further analysis with molecular dynamics (MD) simulations. In MD simulations, UA exhibited highly frequent interactions with residues Arg120 and Glu524 in the COX-2 active site and NMDA, whereby it might prevent COX-2 and NMDA receptor activation. Treatment with UA 10 mg/Kg showed peripheral and central antinociceptive effect. The antinociceptive effect of B. verticillata might be predominantly attributed to peripheral actions, including the participation of anti-inflammatory components. Ursolic acid is the main active component and seems to be a promising source of COX-2 inhibitors and NMDA receptor antagonists. PMID:28588488

Antidepressant action of ketamine via mTOR is mediated by inhibition of nitrergic Rheb degradation.

PubMed

Harraz, M M; Tyagi, R; Cortés, P; Snyder, S H

2016-03-01

As traditional antidepressants act only after weeks/months, the discovery that ketamine, an antagonist of glutamate/N-methyl-D-aspartate (NMDA) receptors, elicits antidepressant actions in hours has been transformative. Its mechanism of action has been elusive, though enhanced mammalian target of rapamycin (mTOR) signaling is a major feature. We report a novel signaling pathway wherein NMDA receptor activation stimulates generation of nitric oxide (NO), which S-nitrosylates glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Nitrosylated GAPDH complexes with the ubiquitin-E3-ligase Siah1 and Rheb, a small G protein that activates mTOR. Siah1 degrades Rheb leading to reduced mTOR signaling, while ketamine, conversely, stabilizes Rheb that enhances mTOR signaling. Drugs selectively targeting components of this pathway may offer novel approaches to the treatment of depression.

Facilitation of granule cell epileptiform activity by mossy fiber-released zinc in the pilocarpine model of temporal lobe epilepsy.

PubMed

Timofeeva, Olga; Nadler, J Victor

2006-03-17

Recurrent mossy fiber synapses in the dentate gyrus of epileptic brain facilitate the synchronous firing of granule cells and may promote seizure propagation. Mossy fiber terminals contain and release zinc. Released zinc inhibits the activation of NMDA receptors and may therefore oppose the development of granule cell epileptiform activity. Hippocampal slices from rats that had experienced pilocarpine-induced status epilepticus and developed a recurrent mossy fiber pathway were used to investigate this possibility. Actions of released zinc were inferred from the effects of chelation with 1 mM calcium disodium EDTA (CaEDTA). When granule cell population bursts were evoked by mossy fiber stimulation in the presence of 6 mM K(+) and 30 microM bicuculline, CaEDTA slowed the rate at which evoked bursting developed, but did not change the magnitude of the bursts once they had developed fully. The effects of CaEDTA were then studied on the pharmacologically isolated NMDA receptor- and AMPA/kainate receptor-mediated components of the fully developed bursts. CaEDTA increased the magnitude of NMDA receptor-mediated bursts and reduced the magnitude of AMPA/kainate receptor-mediated bursts. CaEDTA did not affect the granule cell bursts evoked in slices from untreated rats by stimulating the perforant path in the presence of bicuculline and 6 mM K(+). These results suggest that zinc released from the recurrent mossy fibers serves mainly to facilitate the recruitment of dentate granule cells into population bursts.

Fear extinction induces mGluR5-mediated synaptic and intrinsic plasticity in infralimbic neurons.

PubMed

Sepulveda-Orengo, Marian T; Lopez, Ana V; Soler-Cedeño, Omar; Porter, James T

2013-04-24

Studies suggest that plasticity in the infralimbic prefrontal cortex (IL) in rodents and its homolog in humans is necessary for inhibition of fear during the recall of fear extinction. The recall of extinction is impaired by locally blocking metabotropic glutamate receptor type 5 (mGluR5) activation in IL during extinction training. This finding suggests that mGluR5 stimulation may lead to IL plasticity needed for fear extinction. To test this hypothesis, we recorded AMPA and NMDA currents, AMPA receptor (AMPAR) rectification, and intrinsic excitability in IL pyramidal neurons in slices from trained rats using whole-cell patch-clamp recording. We observed that fear extinction increases the AMPA/NMDA ratio, consistent with insertion of AMPARs into IL synapses. In addition, extinction training increased inward rectification, suggesting that extinction induces the insertion of calcium-permeable (GluA2-lacking) AMPARs into IL synapses. Consistent with this, selectively blocking calcium-permeable AMPARs with Naspm reduced the AMPA EPSCs in IL neurons to a larger degree after extinction. Extinction-induced changes in AMPA/NMDA ratio, rectification, and intrinsic excitability were blocked with an mGluR5 antagonist. These findings suggest that mGluR5 activation leads to consolidation of fear extinction by regulating the intrinsic excitability of IL neurons and modifying the composition of AMPARs in IL synapses. Therefore, impaired mGluR5 activity in IL synapses could be one factor that causes inappropriate modulation of fear expression leading to anxiety disorders.

Inducible Nitric Oxide Inhibitors Block NMDA Antagonist-Stimulated Motoric Behaviors and Medial Prefrontal Cortical Glutamate Efflux

PubMed Central

Bergstrom, Hadley C.; Darvesh, Altaf S.; Berger, S. P.

2015-01-01

Nitric oxide (NO) plays a critical role in the motoric and glutamate releasing action of N-methyl-D-aspartate (NMDA)-antagonist stimulants. Earlier studies utilized neuronal nitric oxide synthase inhibitors (nNOS) for studying the neurobehavioral effects of non-competitive NMDA-antagonist stimulants such as dizocilpine (MK-801) and phencyclidine (PCP). This study explores the role of the inducible nitric oxide synthase inhibitors (iNOS) aminoguanidine (AG) and (-)-epigallocatechin-3-gallate (EGCG) in NMDA-antagonist induced motoric behavior and prefrontal cortical glutamate efflux. Adult male rats were administered a dose range of AG, EGCG, or vehicle prior to receiving NMDA antagonists MK-801, PCP, or a conventional psychostimulant (cocaine) and tested for motoric behavior in an open arena. Glutamate in the medial prefrontal cortex (mPFC) was measured using in vivo microdialysis after a combination of AG or EGCG prior to MK-801. Acute administration of AG or EGCG dose-dependently attenuated the locomotor and ataxic properties of MK-801 and PCP. Both AG and EGCG were unable to block the motoric effects of cocaine, indicating the acute pharmacologic action of AG and EGCG is specific to NMDA antagonism and not generalizable to all stimulant class drugs. AG and EGCG normalized MK-801-stimulated mPFC glutamate efflux. These data demonstrate that AG and EGCG attenuates NMDA antagonist-stimulated motoric behavior and cortical glutamate efflux. Our results suggest that EGCG-like polyphenol nutraceuticals (contained in “green tea” and chocolate) may be clinically useful in protecting against the adverse behavioral dissociative and cortical glutamate stimulating effects of NMDA antagonists. Medications that interfere with NMDA antagonists such as MK-801 and PCP have been proposed as treatments for schizophrenia. PMID:26696891

The neuropsychopharmacology of phencyclidine: from NMDA receptor hypofunction to the dopamine hypothesis of schizophrenia.

PubMed

Jentsch, J D; Roth, R H

1999-03-01

Administration of noncompetitive NMDA/glutamate receptor antagonists, such as phencyclidine (PCP) and ketamine, to humans induces a broad range of schizophrenic-like symptomatology, findings that have contributed to a hypoglutamatergic hypothesis of schizophrenia. Moreover, a history of experimental investigations of the effects of these drugs in animals suggests that NMDA receptor antagonists may model some behavioral symptoms of schizophrenia in nonhuman subjects. In this review, the usefulness of PCP administration as a potential animal model of schizophrenia is considered. To support the contention that NMDA receptor antagonist administration represents a viable model of schizophrenia, the behavioral and neurobiological effects of these drugs are discussed, especially with regard to differing profiles following single-dose and long-term exposure. The neurochemical effects of NMDA receptor antagonist administration are argued to support a neurobiological hypothesis of schizophrenia, which includes pathophysiology within several neurotransmitter systems, manifested in behavioral pathology. Future directions for the application of NMDA receptor antagonist models of schizophrenia to preclinical and pathophysiological research are offered.

Pharmacological enhancement of behavioral therapy: focus on posttraumatic stress disorder.

PubMed

Choi, Dennis C; Rothbaum, Barbara O; Gerardi, Maryrose; Ressler, Kerry J

2010-01-01

Improved efficacy in the treatment of posttraumatic stress disorder (PTSD) and other anxiety disorders is urgently needed. Traditional anxiety treatments of hypnosis and psychodynamic therapy may be of some help, but uncontrolled studies lead to inconclusive results on the efficacy of these treatment techniques. There is a larger literature supporting the efficacy of cognitive-behavioral procedures with PTSD, including prolonged exposure therapy, eye movement desensitization and reprocessing, and anxiety management techniques. The cutting-edge technology of virtual reality-based exposure therapy for PTSD is particularly exciting. To further build on effective psychosocial treatments, current pharmacological augmentation approaches to emotional learning are being combined with psychotherapy. In particular, D-cycloserine, a partial NMDA agonist, has shown to be effective in facilitating the exposure/extinction therapy to improve the efficacy of treating anxiety disorders, and may guide the way for new pharmacological enhancements of behavioral therapy.

The Relationship Between the Renin-Angiotensin-Aldosterone System and NMDA Receptor-Mediated Signal and the Prevention of Retinal Ganglion Cell Death.

PubMed

Kobayashi, Mamoru; Hirooka, Kazuyuki; Ono, Aoi; Nakano, Yuki; Nishiyama, Akira; Tsujikawa, Akitaka

2017-03-01

Excitotoxicity, which is due to glutamate-induced toxic effects on the retinal ganglion cell (RGC), is one of several mechanisms of RGC loss. The renin-angiotensin-aldosterone system (RAAS) has also been implicated in RGC death. Therefore, it is important to determine the exact relationship between the RAAS and N-methyl-d-aspartate (NMDA) receptor-mediated signal in order to prevent RGC death. N-methyl-d-aspartate or aldosterone was injected into the vitreous body. After intravitreal injection of NMDA or aldosterone, animals were treated with spironolactone or memantine. Retinal damage was evaluated by measuring the number of RGCs at 4 weeks after local administration of aldosterone or at 2 weeks after local administration of NMDA. Vitreous humor levels of aldosterone were measured using enzyme immunoassay kits. A significantly decreased number of RGCs were observed after intravitreal injection of NMDA. Although spironolactone did not show any neuroprotective effects, memantine significantly reduced NMDA-induced degeneration in the retina. Furthermore, a significant decrease in the number of RGCs was observed after an intravitreal injection of aldosterone. While memantine did not exhibit any neuroprotective effects, spironolactone caused a significant reduction in the aldosterone-induced degeneration in the retina. There was no change in the aldosterone concentration in the vitreous humor after an NMDA injection. Our findings indirectly show that there is no relationship between the RAAS and NMDA receptor-mediated signal with regard to RGC death.

Cutoff in Potency Implicates Alcohol Inhibition of N-Methyl-D-Aspartate Receptors in Alcohol Intoxication

NASA Astrophysics Data System (ADS)

Peoples, Robert W.; Weight, Forrest F.

1995-03-01

As the number of carbon atoms in an aliphatic n-alcohol is increased from one to five, intoxicating potency, lipid solubility, and membrane lipid disordering potency all increase in a similar exponential manner. However, the potency of aliphatic n-alcohols for producing intoxication reaches a maximum at six to eight carbon atoms and then decreases. The molecular basis of this "cutoff" effect is not understood, as it is not correlated with either the lipid solubility or the membrane disordering potency of the alcohols, which continue to increase exponentially. Since it has been suggested that inhibition of N-methyl-D-aspartate (NMDA) receptors by alcohols may play a role in alcohol intoxication, we investigated whether a series of aliphatic n-alcohols would exhibit a cutoff in potency for inhibition of NMDA receptors. We found that although potency for inhibition of NMDA receptors increased exponentially for alcohols with one to five carbon atoms, potency for inhibition of NMDA receptors reached a maximum at six to eight carbon atoms and then abruptly disappeared. This cutoff for alcohol inhibition of NMDA receptors is consistent with an interaction of the alcohols with a hydrophobic pocket on the receptor protein. In addition, the similarity of the cutoffs for alcohol inhibition of NMDA receptors and alcohol intoxication suggests that the cutoff for NMDA receptor inhibition may contribute to the cutoff for alcohol intoxication, which is consistent with an important role of NMDA receptors in alcohol intoxication.

Molecular mechanisms of neuroprotective action of immunosuppressants--facts and hypotheses.

PubMed

Kaminska, Bozena; Gaweda-Walerych, Katarzyna; Zawadzka, Malgorzata

2004-01-01

Cyclosporin A (CsA) and FK506 (Tacrolimus) are short polypeptides which block the activation of lymphocytes and other immune system cells. Immunosuppressants exert neuroprotective and neurotrophic action in traumatic brain injury, sciatic nerve injury, focal and global ischemia in animals. Their neuroprotective actions are not understood and many hypotheses have been formed to explain such effects. We discuss a role of drug target--calcineurin in neuroprotective action of immunosuppressants. Protein dephosphorylation by calcineurin plays an important role in neuronal signal transduction due to its ability to regulate the activity of ion channels, glutamate release, and synaptic plasticity. In vitro FK506 protects cortex neurons from NMDA-induced death, augments NOS phosphorylation inhibiting its activity and NO synthesis. However, in vivo experiments demonstrated that FK506 in neuroprotective doses did not block excitotoxic cell death nor did it alter NO production during ischemia/reperfusion. Tissue damage in ischemia is the result of a complex pathophysiological cascade, which comprises a variety of distinct pathological events. Resident non-neuronal brain cells respond rapidly to neuronal cell death and may have both deleterious and useful role in neuronal damage. There is increasing evidence that reactive gliosis and post-ischemic inflammation involving microglia contribute to ischemic damage. We have demonstrated that FK506 modulates hypertrophic/proliferative responses and proinflammatory cytokine expression in astrocytes and microglia in vitro and in focal transient brain ischemia. Our findings suggest that astrocytes and microglia are direct targets of FK506 and modulation of glial response and inflammation is a possible mechanism of FK506-mediated neuroprotection in ischemia.

Alkaloid fraction of Uncaria rhynchophylla protects against N-methyl-D-aspartate-induced apoptosis in rat hippocampal slices.

PubMed

Lee, Jongseok; Son, Dongwook; Lee, Pyeongjae; Kim, Sun-Yeou; Kim, Hocheol; Kim, Chang-Ju; Lim, Eunhee

2003-09-04

Uncaria rhynchophylla is a medicinal herb which has sedative and anticonvulsive effects and has been applied in the treatment of epilepsy in Oriental medicine. In this study, the effect of alkaloid fraction of U. rhynchophylla against N-methyl-D-aspartate (NMDA)-induced neuronal cell death was investigated. Pretreatment with an alkaloid fraction of U. rhynchophylla for 1 h decreased the degree of neuronal damage induced by NMDA exposure in cultured hippocampal slices and also inhibited NMDA-induced enhanced expressions of apoptosis-related genes such as c-jun, p53, and bax. In the present study, the alkaloid fraction of U. rhynchophylla was shown to have a protective property against NMDA-induced cytotoxicity by suppressing the NMDA-induced apoptosis in rat hippocampal slices.

Neonatal NMDA Receptor Blockade Disrupts Spike Timing and Glutamatergic Synapses in Fast Spiking Interneurons in a NMDA Receptor Hypofunction Model of Schizophrenia

PubMed Central

Jones, Kevin S.; Corbin, Joshua G.; Huntsman, Molly M.

2014-01-01

The dysfunction of parvalbumin-positive, fast-spiking interneurons (FSI) is considered a primary contributor to the pathophysiology of schizophrenia (SZ), but deficits in FSI physiology have not been explicitly characterized. We show for the first time, that a widely-employed model of schizophrenia minimizes first spike latency and increases GluN2B-mediated current in neocortical FSIs. The reduction in FSI first-spike latency coincides with reduced expression of the Kv1.1 potassium channel subunit which provides a biophysical explanation for the abnormal spiking behavior. Similarly, the increase in NMDA current coincides with enhanced expression of the GluN2B NMDA receptor subunit, specifically in FSIs. In this study mice were treated with the NMDA receptor antagonist, MK-801, during the first week of life. During adolescence, we detected reduced spike latency and increased GluN2B-mediated NMDA current in FSIs, which suggests transient disruption of NMDA signaling during neonatal development exerts lasting changes in the cellular and synaptic physiology of neocortical FSIs. Overall, we propose these physiological disturbances represent a general impairment to the physiological maturation of FSIs which may contribute to schizophrenia-like behaviors produced by this model. PMID:25290690

P2X7, NMDA and BDNF receptors converge on GSK3 phosphorylation and cooperate to promote survival in cerebellar granule neurons.

PubMed

Ortega, Felipe; Pérez-Sen, Raquel; Morente, Verónica; Delicado, Esmerilda G; Miras-Portugal, Maria Teresa

2010-05-01

Glycogen synthase kinase-3 (GSK3) is a key player in the regulation of neuronal survival. Herein, we report evidence of an interaction between P2X7 receptors with NMDA and BDNF receptors at the level of GSK3 signalling and neuroprotection. The activation of these receptors in granule neurons led to a sustained pattern of GSK3 phosphorylation that was mainly PKC-dependent. BDNF was the most potent at inducing GSK3 phosphorylation, which was also dependent on PI3K. The P2X7 agonist, BzATP, exhibited additive effects with both NMDA and BDNF to rescue granule neurons from cell death induced by PI3K inhibition. This survival effect was mediated by the PKC-dependent GSK3 pathway. In addition, ERK1/2 proteins were also involved in BDNF protective effect. These results show the function of ATP in amplifying neuroprotective actions of glutamate and neurotrophins, and support the role of GSK3 as an important convergence point for these survival promoting factors in granule neurons.

Synthesis and Structure Activity Relationship of Tetrahydroisoquinoline-based Potentiators of GluN2C and GluN2D Containing N-Methyl-D-Aspartate Receptors

PubMed Central

Santangelo Freel, Rose M.; Ogden, Kevin K.; Strong, Katie L.; Khatri, Alpa; Chepiga, Kathryn M.; Jensen, Henrik S.; Traynelis, Stephen F.; Liotta, Dennis C.

2015-01-01

We describe here the synthesis and evaluation of a series of tetrahydroisoquinolines that show subunit-selective potentiation of NMDA receptors containing the GluN2C or GluN2D subunits. Bischler-Napieralski conditions were employed in the key step for the conversion of acyclic amides to the corresponding tetrahydroisoquinoline containing analogs. Compounds were evaluated using both two electrode voltage clamp recordings from Xenopus laevis oocytes and imaging of mammalian BHK cells loaded with Ca2+-sensitive dyes. The most potent analogues had EC50 values of 300 nM and showed over 2-fold potentiation of the response to maximally effective concentrations of glutamate and glycine, but had no effect on responses from NMDA receptors containing the GluN2A or GluN2B subunits, AMPA, kainate, GABA, or glycine receptors or a variety of other potential targets. These compounds represent a potent class of small molecule subunit-selective potentiators of NMDA receptors. PMID:23627311

Revisiting the Quinoxalinedione Scaffold in the Construction of New Ligands for the Ionotropic Glutamate Receptors.

PubMed

Demmer, Charles S; Rombach, David; Liu, Na; Nielsen, Birgitte; Pickering, Darryl S; Bunch, Lennart

2017-11-15

More than two decades ago, the quinoxalinedione scaffold was shown to act as an α-amino acid bioisoster. Following extensive structure-activity relationship (SAR) studies, the antagonists DNQX, CNQX, and NBQX in the ionotropic glutamate receptor field were identified. In this work, we revisit the quinoxalinedione scaffold and explore the incorporation of an acid functionality in the 6-position. The SAR studies disclose that by this strategy it was possible to tune in iGluR selectivity among the AMPA, NMDA, and KA receptors, and to some extent also obtain full receptor subtype selectivity. Highlights of the study of 44 new analogues are compound 2m being a high affinity ligand for native AMPA receptors (IC 50 = 0.48 μM), analogues 2e,f,h,k,v all displayed selectivity for native NMDA receptors, and compounds 2s,t,u are selective ligand for the GluK1 receptor. Most interestingly, compound 2w was shown to be a GluK3-preferring ligand with full selectivity over native AMPA, KA and NMDA receptors.

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

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

Activation of PAF-synthesizing enzymes in rat brain stem slices after LTP induction in the medial vestibular nuclei.

PubMed

Francescangeli, Ermelinda; Grassi, Silvarosa; Pettorossi, Vito E; Goracci, Gianfrancesco

2002-11-01

LysoPAF acetyltransferase (lysoPAF-AT) and PAF-synthesizing phosphocholinetransferase (PAF-PCT) are the two enzymes which catalyze the final reactions for the synthesis of PAF. Their activities, assayed in the homogenate of rat brain stem slices and under their optimal conditions, increased 5 min after high frequency stimulation of vestibular afferents, inducing LTP in the medial vestibular nuclei. The activity of phosphatidylcholine-synthesizing phosphocholinetransferase, was not affected. Sixty minutes from the induction of LTP, PAF-PCT activity, but not that of lysoPAF-AT, was still significantly higher with respect to 5 min test stimulated control. We used AP-5 to verify whether this increase was strictly dependent upon LTP induction, which requires NMDA receptor activation. In AP-5 treated slices, lysoPAF-acetyltransferase and PAF-synthesizing phosphocholinetransferase activities increased, but they were reduced after high frequency stimulation under AP-5. In conclusion, we have demonstrated that the activities of PAF-synthesizing enzymes are activated soon after the induction of LTP and that this effect is linked to the activation of NMDA-receptors. We suggest that the enzyme activation by AP-5, preventing LTP, might be due to glutamate enhancement but, in neurons showing LTP and under normal conditions, the activation of potentiation mechanisms is critical for the enhancement of enzyme activities.

Effects of ketamine and N-methyl-D-aspartate on fluoxetine-induced antidepressant-related behavior using the forced swimming test.

PubMed

Owolabi, Rotimi Adegbenga; Akanmu, Moses Atanda; Adeyemi, Oluwole Isaac

2014-04-30

This study investigated the effects of ketamine on fluoxetine-induced antidepressant behavior using the forced swimming test (FST) in mice. In order to understand the possible role of N-methyl-d-aspartate (NMDA) neurotransmission in the antidepressant effect of fluoxetine, different groups of mice (n=10) were administered with acute ketamine (3mg/kg, i.p.), acute NMDA (75mg/kg and 150mg/kg, i.p.) and a 21-day chronic ketamine (15mg/kg, i.p./day) were administered prior to the administration of fluoxetine (20mg/kg, i.p.) in the mice. Antidepressant related behavior (immobility score) was measured using the forced swimming test. The results showed that the acute ketamine and fluoxetine alone treatments elicited a significant (p<0.05) reduction in immobility score compared with saline control. Furthermore, pre-treatment with acute ketamine significantly enhanced by the fluoxetine-induced decrease in immobility score. In contrast, pre-treatment with NMDA (150mg/kg) significantly (p<0.05) reversed fluoxetine-induced decrease in immobility score. On the other hand, chronic administration of ketamine significantly elicited an increase in immobility score as well as reversed the reduction induced by fluoxetine. Similarly, NMDA administration at both 75mg/kg and 150mg/kg increased immobility score in chronically administered ketamine groups. Furthermore, chronic administration of ketamine, followed by NMDA (75mg/kg) and fluoxetine significantly elevated the immobility score when compared with the group that received NMDA and fluoxetine but not chronically treated with ketamine. It can be suggested) that facilitation of NMDA transmission blocked fluoxetine-induced reduction in immobility score, while down-regulation of NMDA transmission is associated with increase in fluoxetine-induced antidepressant-related behavior in mice. Down-regulation of the NMDA transmission is proposed as an essential component of mechanism of suppression of depression related behaviors by fluoxetine. Modulation of NMDA transmission is suggested to be relevant in the mechanism of action of fluoxetine. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

HDAC inhibitors as cognitive enhancers in fear, anxiety and trauma therapy: where do we stand?

PubMed Central

Whittle, Nigel; Singewald, Nicolas

2014-01-01

A novel strategy to treat anxiety and fear-related disorders such as phobias, panic and PTSD (post-traumatic stress disorder) is combining CBT (cognitive behavioural therapy), including extinction-based exposure therapy, with cognitive enhancers. By targeting and boosting mechanisms underlying learning, drug development in this field aims at designing CBT-augmenting compounds that help to overcome extinction learning deficits, promote long-term fear inhibition and thus support relapse prevention. Progress in revealing the role of epigenetic regulation of specific genes associated with extinction memory generation has opened new avenues in this direction. The present review examines recent evidence from pre-clinical studies showing that increasing histone acetylation, either via genetic or pharmacological inhibition of HDACs (histone deacetylases) by e.g. vorinostat/SAHA (suberoylanilide hydroxamic acid), entinostat/MS-275, sodium butyrate, TSA (trichostatin A) or VPA (valproic acid), or by targeting HATs (histone acetyltransferases), augments fear extinction and, importantly, generates a long-term extinction memory that can protect from return of fear phenomena. The molecular mechanisms and pathways involved including BDNF (brain-derived neurotrophic factor) and NMDA (N-methyl-D-aspartate) receptor signalling are just beginning to be revealed. First studies in healthy humans are in support of extinction-facilitating effects of HDAC inhibitors. Very recent evidence that HDAC inhibitors can rescue deficits in extinction-memory-impaired rodents indicates a potential clinical utility of this approach also for exposure therapy-resistant patients. Important future work includes investigation of the long-term safety aspects of HDAC inhibitor treatment, as well as design of isotype(s)-specific inhibitors. Taken together, HDAC inhibitors display promising potential as pharmacological adjuncts to augment the efficacy of exposure-based approaches in anxiety and trauma therapy. PMID:24646280

Ketamine-induced inhibition of glycogen synthase kinase-3 contributes to the augmentation of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor signaling.

PubMed

Beurel, Eléonore; Grieco, Steven F; Amadei, Celeste; Downey, Kimberlee; Jope, Richard S

2016-09-01

Sub-anesthetic doses of ketamine have been found to provide rapid antidepressant actions, indicating that the cellular signaling systems targeted by ketamine are potential sites for therapeutic intervention. Ketamine acts as an antagonist of N-methyl-D-aspartate (NMDA) receptors, and animal studies indicate that subsequent augmentation of signaling by α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors is critical for the antidepressant outcome. In this study, we tested if the inhibitory effect of ketamine on glycogen synthase kinase-3 (GSK3) affected hippocampal cell-surface AMPA receptors using immunoblotting of membrane and synaptosomal extracts from wild-type and GSK3 knockin mice. Treatment with an antidepressant dose of ketamine increased the hippocampal membrane level of the AMPA glutamate receptor (GluA)1 subunit, but did not alter the localization of GluA2, GluA3, or GluA4. This effect of ketamine was abrogated in GSK3 knockin mice expressing mutant GSK3 that cannot be inhibited by ketamine, demonstrating that ketamine-induced inhibition of GSK3 is necessary for up-regulation of cell surface AMPA GluA1 subunits. AMPA receptor trafficking is regulated by post-synaptic density-95 (PSD-95), a substrate for GSK3. Ketamine treatment decreased the hippocampal membrane level of phosphorylated PSD-95 on Thr-19, the target of GSK3 that promotes AMPA receptor internalization. These results demonstrate that ketamine-induced inhibition of GSK3 causes reduced phosphorylation of PSD-95, diminishing the internalization of AMPA GluA1 subunits to allow for augmented signaling through AMPA receptors following ketamine treatment. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Ketamine-induced inhibition of glycogen synthase kinase-3 contributes to the augmentation of AMPA receptor signaling

PubMed Central

Beurel, Eléonore; Grieco, Steven F; Amadei, Celeste; Downey, Kimberlee; Jope, Richard S

2016-01-01

Objectives Sub-anesthetic doses of ketamine have been found to provide rapid antidepressant actions, indicating that the cellular signaling systems targeted by ketamine are potential sites for therapeutic intervention. Ketamine acts as an antagonist of N-methyl-D-aspartate (NMDA) receptors, and animal studies indicate that subsequent augmentation of signaling by α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors is critical for the antidepressant outcome. Methods In this study, we tested if the inhibitory effect of ketamine on glycogen synthase kinase-3 (GSK3) affected hippocampal cell-surface AMPA receptors using immunoblotting of membrane and synaptosomal extracts from wild-type and GSK3 knockin mice. Results Treatment with an antidepressant dose of ketamine increased the hippocampal membrane level of the AMPA glutamate receptor (GluA)1 subunit, but did not alter the localization of GluA2, GluA3, or GluA4. This effect of ketamine was abrogated in GSK3 knockin mice expressing mutant GSK3 that cannot be inhibited by ketamine, demonstrating that ketamine-induced inhibition of GSK3 is necessary for up-regulation of cell surface AMPA GluA1 subunits. AMPA receptor trafficking is regulated by post-synaptic density-95 (PSD-95), a substrate for GSK3. Ketamine treatment decreased the hippocampal membrane level of phosphorylated PSD-95 on Thr-19, the target of GSK3 that promotes AMPA receptor internalization. Conclusions These results demonstrate that ketamine-induced inhibition of GSK3 causes reduced phosphorylation of PSD-95, diminishing the internalization of AMPA GluA1 subunits to allow for augmented signaling through AMPA receptors following ketamine treatment. PMID:27687706

Comparison of Pharmacological Potency and Safety of Glutamate Blocker IEM-1913 and Memantine.

PubMed

Gmiro, V E; Serdyuk, S E; Veselkina, O S

2015-11-01

Adamantane-containing glutamate blocker IEM-1913 (1-amino-4-(1-adamantane-amino)-butane dihydrochloride) equals to memantine in antiparkinsonian potency, but surpasses it in anticonvulsive, antidepressant, and analgesic activities. Moreover, its use is less toxic and safer. IEM-1913 produces significant pharmacological effects at a wide concentration diapason (0.03-1.00 mg/kg), while memantine is effective within a narrow range only (15-20 mg/kg). High pharmacological efficacy and low toxicity of IEM-1913 can be explained by the fact that in contrast to monocationic selective NMDA antagonist memantine, the dicationic glutamate blocker IEM-1913 produces a combined block of cerebral NMDA and AMPA receptors.

Memantine Can Reduce Ethanol-Induced Caspase-3 Activity and Apoptosis in H4 Cells by Decreasing Intracellular Calcium.

PubMed

Wang, Xiaolong; Chen, Jiajun; Wang, Hongbo; Yu, Hao; Wang, Changliang; You, Jiabin; Wang, Pengfei; Feng, Chunmei; Xu, Guohui; Wu, Xu; Zhao, Rui; Zhang, Guohua

2017-08-01

Caspase-3 activation and apoptosis are associated with various neurodegenerative disorders. Calcium activation is an important factor in promoting apoptosis. We, therefore, assessed the role of intracellular calcium in ethanol-induced activation of caspase-3 in H4 human neuroglioma cells and the protective effect of the NMDA receptor antagonist, memantine, on ethanol-induced apoptosis in H4 cells. H4 cells were treated with 100 mM EtOH (in culture medium) for 2 days. For interaction studies, cells were treated with memantine (4 μM), EDTA (1 mM), or BAPTA-AM (10 μM) before treatment with EtOH. Knockdown of the gene encoding the NR1 subunit of the NMDA receptor was performed using RNAi. Apoptosis was detected by Annexin V-FITC/PI staining and flow cytometry. Cell viability was detected using an MTS cell proliferation kit. Fluorescence dual wavelength spectrophotometry was used to determine the intracellular calcium concentration. The levels of NR1, caspase-3, IP3R1, and SERCA1 proteins were detected by western blotting. NR1, IP3R1, and SERCA1 mRNA levels were detected by qPCR. We observed increased expression of NR1, IP3R1, SERCA1, and increased intracellular levels of calcium ions in H4 cells exposed to ethanol. In addition, the calcium chelators, EDTA and BAPTA, and RNAi disruption of the NMDA receptor reduced ethanol-induced caspase-3 activation in H4 cells. Memantine treatment reduced the ethanol-induced increase of intracellular calcium, caspase-3 activation, apoptosis, and the ethanol-induced decrease in cell viability. Our results indicate that ethanol-induced caspase-3 activation and apoptosis are likely to be dependent on cytosolic calcium levels and that they can be reduced by memantine treatment.

Protective effect of thalidomide against N-methyl-D-aspartate-induced retinal neurotoxicity.

PubMed

Takada, Kazuhide; Munemasa, Yasunari; Kuribayashi, Junko; Fujino, Hiromi; Kitaoka, Yasushi

2011-10-01

Thalidomide, an inhibitor of tumor necrosis factor-α (TNF-α) production, has been indicated to be useful for many inflammatory and oncogenic diseases. In the present study, we examined whether thalidomide (50 mg/kg/day, p.o.) has a protective effect against N-methyl-D-aspartate (NMDA)-induced retinal neurotoxicity in rats. A morphometric analysis showed that systemic administration of thalidomide protects neural cells in the ganglion cell layer (GCL) in a dose-dependent manner and significantly decreases the number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells in GCL and in the inner nuclear layer (INL). ELISA showed that thalidomide significantly suppressed the elevation of TNF-α 6 and 24 hr after an NMDA injection. Western blot analysis revealed a significant increase in nuclear factor-κB (NF-κB) p65 level in the retinas treated with NMDA at 24 hr after the injection, but not at 6 or 72 hr. Furthermore, an increase in p-JNK and p-p38 levels was also observed in the retina after NMDA injection. Thalidomide suppressed the increased expressions of NF-κB p65, p-JNK, and p-p38 after NMDA injection. Immunohistochemical analysis showed that thalidomide attenuated NF-κB p65 immunoreactivity in the GCL induced by NMDA treatment. In the NMDA-treated group, translocation of NF-κB p65 from the cytoplasm to the nucleus was detected in TUNEL-positive cells exposed to NMDA treatment. These results suggest new indications for thalidomide against neurodegenerative diseases. Copyright © 2011 Wiley-Liss, Inc.

Long-term depression-associated signaling is required for an in vitro model of NMDA receptor-dependent synapse pruning

PubMed Central

Henson, Maile A.; Tucker, Charles J.; Zhao, Meilan; Dudek, Serena M.

2016-01-01

Activity-dependent pruning of synaptic contacts plays a critical role in shaping neuronal circuitry in response to the environment during postnatal brain development. Although there is compelling evidence that shrinkage of dendritic spines coincides with synaptic long-term depression (LTD), and that LTD is accompanied by synapse loss, whether NMDA receptor (NMDAR)-dependent LTD is a required step in the progression toward synapse pruning is still unknown. Using repeated applications of NMDA to induce LTD in dissociated rat neuronal cultures, we found that synapse density, as measured by colocalization of fluorescent markers for pre- and postsynaptic structures, was decreased irrespective of the presynaptic marker used, post-treatment recovery time, and the dendritic location of synapses. Consistent with previous studies, we found that synapse loss could occur without apparent net spine loss or cell death. Furthermore, synapse loss was unlikely to require direct contact with microglia, as the number of these cells was minimal in our culture preparations. Supporting a model by which NMDAR-LTD is required for synapse loss, the effect of NMDA on fluorescence colocalization was prevented by phosphatase and caspase inhibitors. In addition, gene transcription and protein translation also appeared to be required for loss of putative synapses. These data support the idea that NMDAR-dependent LTD is a required step in synapse pruning and contribute to our understanding of the basic mechanisms of this developmental process. PMID:27794462

Inflammatory pain-induced signaling events following a conditional deletion of the N-methyl-D-aspartate receptor in spinal cord dorsal horn.

PubMed

Cheng, H T; Suzuki, M; Hegarty, D M; Xu, Q; Weyerbacher, A R; South, S M; Ohata, M; Inturrisi, C E

2008-08-26

The N-methyl-d-aspartate (NMDA) receptor in the spinal cord dorsal horn (SCDH) is one of the mechanisms involved in central sensitization during chronic pain. Previously, this laboratory created a spatio-temporal knockout (KO) of the N-methyl-d-aspartate receptor I (NR1) subunit in the mouse SCDH. The NR1 KO completely blocks NR1 gene and subsequent NMDA receptor expression and function in SCDH neurons. In the NR1 KO mice, the mechanical and cold allodynia induced at 24 h after complete Freund's adjuvant (CFA) was reduced. However, the protective effects of KO were transient and were not seen at 48 h after CFA. These observations suggest the presence of NMDA-independent pathways that contribute to CFA-induced pain. CFA induces the activation of several signaling cascades in the SCDH, including protein kinase C (PKC)gamma and extracellular signal-regulated kinases (ERK1/2). The phosphorylation of PKCgamma and ERK1/2 was inhibited in the SCDH of NR1 KO mice up to 48 h after CFA treatment, suggesting that these pathways are NMDA receptor-dependent. Interestingly, neuronal cyclooxygenase (COX) -2 expression and microglial p38 phosphorylation were induced in the SCDH of the NR1 KO at 48 h after CFA. Our findings provide evidence that inflammatory reactions are responsible for the recurrence of pain after NR1 KO in the SCDH.

MDMA-induced loss of parvalbumin interneurons within the dentate gyrus is mediated by 5HT2A and NMDA receptors.

PubMed

Collins, Stuart A; Gudelsky, Gary A; Yamamoto, Bryan K

2015-08-15

MDMA is a widely abused psychostimulant which causes a rapid and robust release of the monoaminergic neurotransmitters dopamine and serotonin. Recently, it was shown that MDMA increases extracellular glutamate concentrations in the dorsal hippocampus, which is dependent on serotonin release and 5HT2A/2C receptor activation. The increased extracellular glutamate concentration coincides with a loss of parvalbumin-immunoreactive (PV-IR) interneurons of the dentate gyrus region. Given the known susceptibility of PV interneurons to excitotoxicity, we examined whether MDMA-induced increases in extracellular glutamate in the dentate gyrus are necessary for the loss of PV cells in rats. Extracellular glutamate concentrations increased in the dentate gyrus during systemic and local administration of MDMA. Administration of the NMDA receptor antagonist, MK-801, during systemic injections of MDMA, prevented the loss of PV-IR interneurons seen 10 days after MDMA exposure. Local administration of MDL100907, a selective 5HT2A receptor antagonist, prevented the increases in glutamate caused by reverse dialysis of MDMA directly into the dentate gyrus and prevented the reduction of PV-IR. These findings provide evidence that MDMA causes decreases in PV within the dentate gyrus through a 5HT2A receptor-mediated increase in glutamate and subsequent NMDA receptor activation. Copyright © 2015 Elsevier B.V. All rights reserved.

Role of different types of potassium channels in the antidepressant-like effect of agmatine in the mouse forced swimming test.

PubMed

Budni, Josiane; Gadotti, Vinícius M; Kaster, Manuella P; Santos, Adair R S; Rodrigues, Ana Lúcia S

2007-12-01

The administration of agmatine elicits an antidepressant-like effect in the mouse forced swimming test by a mechanism dependent on the inhibition of the NMDA receptors and the L-arginine-nitric oxide (NO) pathway. Since it has been reported that the NO can activate different types of potassium (K(+)) channels in several tissues, the present study investigates the possibility of synergistic interactions between different types of K(+) channel inhibitors and agmatine in the forced swimming test. Treatment of mice by i.c.v. route with subeffective doses of tetraethylammonium (a non specific inhibitor of K(+) channels, 25 pg/site), glibenclamide (an ATP-sensitive K(+) channels inhibitor, 0.5 pg/site), charybdotoxin (a large- and intermediate-conductance calcium-activated K(+) channel inhibitor, 25 pg/site) or apamin (a small-conductance calcium-activated K(+) channel inhibitor, 10 pg/site), augmented the effect of agmatine (0.001 mg/kg, i.p.) in the forced swimming test. Furthermore, the administration of agmatine and the K(+) channel inhibitors, alone or in combination, did not affect locomotion in the open-field test. Moreover, the reduction in the immobility time elicited by an active dose of agmatine (10 mg/kg, i.p.) in the forced swimming test was prevented by the pre-treatment of mice with the K(+) channel openers cromakalim (10 microg/site, i.c.v.) and minoxidil (10 microg/site, i.c.v.), without affecting locomotion. Together these data raise the possibility that the antidepressant-like effect of agmatine in the forced swimming test is related to its modulatory effects on neuronal excitability, via inhibition of K(+) channels.

Brain state-dependent abnormal LFP activity in the auditory cortex of a schizophrenia mouse model

PubMed Central

Nakao, Kazuhito; Nakazawa, Kazu

2014-01-01

In schizophrenia, evoked 40-Hz auditory steady-state responses (ASSRs) are impaired, which reflects the sensory deficits in this disorder, and baseline spontaneous oscillatory activity also appears to be abnormal. It has been debated whether the evoked ASSR impairments are due to the possible increase in baseline power. GABAergic interneuron-specific NMDA receptor (NMDAR) hypofunction mutant mice mimic some behavioral and pathophysiological aspects of schizophrenia. To determine the presence and extent of sensory deficits in these mutant mice, we recorded spontaneous local field potential (LFP) activity and its click-train evoked ASSRs from primary auditory cortex of awake, head-restrained mice. Baseline spontaneous LFP power in the pre-stimulus period before application of the first click trains was augmented at a wide range of frequencies. However, when repetitive ASSR stimuli were presented every 20 s, averaged spontaneous LFP power amplitudes during the inter-ASSR stimulus intervals in the mutant mice became indistinguishable from the levels of control mice. Nonetheless, the evoked 40-Hz ASSR power and their phase locking to click trains were robustly impaired in the mutants, although the evoked 20-Hz ASSRs were also somewhat diminished. These results suggested that NMDAR hypofunction in cortical GABAergic neurons confers two brain state-dependent LFP abnormalities in the auditory cortex; (1) a broadband increase in spontaneous LFP power in the absence of external inputs, and (2) a robust deficit in the evoked ASSR power and its phase-locking despite of normal baseline LFP power magnitude during the repetitive auditory stimuli. The “paradoxically” high spontaneous LFP activity of the primary auditory cortex in the absence of external stimuli may possibly contribute to the emergence of schizophrenia-related aberrant auditory perception. PMID:25018691

Neuroprotective effects of formononetin against NMDA-induced apoptosis in cortical neurons.

PubMed

Tian, Zhen; Liu, Shui-Bing; Wang, Yu-Cai; Li, Xiao-Qiang; Zheng, Lian-He; Zhao, Ming-Gao

2013-12-01

Formononetin (FMNT) is an isoflavone found in many herbs including Trifolium pratense L., Spatholobus suberectus Dunn., and Astragalus mongholicus Bunge. The purpose of this study is to investigate pharmacological properties of FMNT on neurotoxicity induced by N-methyl-D-asparate (NMDA) in primary-cultured cortical neurons. The cell viability was significantly decreased after exposure to NMDA (200 μM) for 40 min. Pretreatment of FMNT (10 μM) for 12 h significantly attenuated the cell loss induced by NMDA exposure. Flow cytometry analysis revealed that treatment of FMNT attenuated the number of apoptotic cells, especially the early phase apoptotic cells, induced by NMDA exposure. Western blot analysis showed that FMNT regulated the expression of apoptosis-related proteins by increasing the levels of Bcl-2 and pro-caspase-3 and decreasing the levels of Bax and caspase-3. These findings demonstrate that FMNT is capable of protecting neurons from NMDA-evoked excitotoxic injury and has a potential perspective to the clinical treatment for neurodegenerative disorders in central nervous system. Copyright © 2013 John Wiley & Sons, Ltd.

Glutamate-mediated excitotoxicity in neonatal hippocampal neurons is mediated by mGluR-induced release of Ca++ from intracellular stores and is prevented by estradiol

PubMed Central

Hilton, Genell D.; Nunez, Joseph L.; Bambrick, Linda; Thompson, Scott M.; McCarthy, Margaret M.

2008-01-01

Hypoxic/ischemic (HI) brain injury in newborn full-term and premature infants is a common and pervasive source of life time disabilities in cognitive and locomotor function. In the adult, HI induces glutamate release and excitotoxic cell death dependent on NMDA receptor activation. In animal models of the premature human infant, glutamate is also released following HI, but neurons are largely insensitive to NMDA or AMPA/kainic acid (KA) receptor-mediated damage. Using primary cultured hippocampal neurons we have determined that glutamate increases intracellular calcium much more than kainic acid. Moreover, glutamate induces cell death by activating Type I metabotropic glutamate receptors (mGluRs). Pretreatment of neurons with the gonadal steroid estradiol reduces the level of the Type I metabotropic glutamate receptors and completely prevents cell death, suggesting a novel therapeutic approach to excitotoxic brain damage in the neonate. PMID:17156362

Suppression of neurite outgrowth of primary cultured hippocampal neurons is involved in impairment of glutamate metabolism and NMDA receptor function caused by nanoparticulate TiO2.

PubMed

Hong, Fashui; Sheng, Lei; Ze, Yuguan; Hong, Jie; Zhou, Yingjun; Wang, Ling; Liu, Dong; Yu, Xiaohong; Xu, Bingqing; Zhao, Xiaoyang; Ze, Xiao

2015-06-01

Numerous studies have indicated that nano-titanium dioxide (TiO2) can induce neurotoxicity in vitro and in vivo, however, it is unclear whether nano-TiO2 affects neurite outgrowth of hippocampal neurons. In order to investigate the mechanism of neurotoxicity, rat primary cultured hippocampal neurons on the fourth day of culture were exposed to 5, 15, and 30 μg/mL nano-TiO2 for 24 h, and nano-TiO2 internalization, dendritic growth, glutamate metabolism, expression of N-methyl-D-aspartate (NMDA) receptor subunits (NR1, NR2A and NR2B), calcium homeostasis, sodium current (INa) and potassium current (IK) were examined. Our findings demonstrated that nano-TiO2 crossed the membrane into the cytoplasm or nucleus, and significantly suppressed dendritic growth of primary cultured hippocampal neurons in a concentration-dependent manner. Furthermore, nano-TiO2 induced a marked release of glutamate to the extracellular region, decreased glutamine synthetase activity and increased phosphate-activated glutaminase activity, elevated intracellular calcium ([Ca(2+)]i), down-regulated protein expression of NR1, NR2A and NR2B, and increased the amplitudes of the INa and IK. In addition, nano-TiO2 increased nitric oxide and nitrice synthase, attenuated the activities of Ca(2+)-ATPase and Na(+)/K(+)-ATPase, and increased the ADP/ATP ratio in the primary neurons. Taken together, these findings indicate that nano-TiO2 inhibits neurite outgrowth of hippocampal neurons by interfering with glutamate metabolism and impairing NMDA receptor function. Copyright © 2015 Elsevier Ltd. All rights reserved.

A hypothalamic digoxin-mediated model for autism.

PubMed

Kurup, Ravi Kumar; Kurup, Parameswara Achutha

2003-11-01

The isoprenoid pathway and its metabolites--digoxin, dolichol, and ubiquinone--were assessed in autism. The isoprenoid pathway and digoxin status was also studied for comparison in individuals of differing hemispheric dominance to determine the role of cerebral dominance in the genesis of autism. There was an upregulation of the isoprenoid pathway as evidenced by elevated HMG CoA reductase activity in autism. Digoxin, an endogenous Na+-K+ ATPase inhibitor secreted by the hypothalamus, was found to be elevated and RBC membrane Na+-K+ ATPase activity was found to be reduced in autism. Membrane Na+-K+ ATPase inhibition can result in increased intracellular Ca2+ and reduced magnesium levels. Hypothalamic digoxin can modulate conscious and subliminal perception and its dysfunction may lead to autism. Digoxin can also preferentially upregulate tryptophan transport over tyrosine resulting in increased levels of depolarizing tryptophan catabolites--serotonin, quinolinic acid (NMDA agonist), strychnine (blocks glycinergic inhibitory transmission), and nicotine (promotes dopamine release) and decreased levels of hyperpolarizing tyrosine catabolites--dopamine, noradrenaline, and morphine--contributing to membrane Na+-K+ ATPase inhibition. Increased nicotine levels can produce increased dopaminergic transmission in the presence of low dopamine levels. NMDA excitotoxicity could result from hypomagnesemia induced by membrane Na+-K+ ATPase inhibition and quinolinic acid, an NMDA agonist acting on the NMDA receptor. Hypomagnesemia and increased dolichol level can affect glycoconjugate metabolism and membranogenesis leading on to disordered synaptic connectivity in the limbic allocortex and defective presentation of viral antigens and neuronal antigens contributing to autoimmunity and viral persistence important in the pathogenesis. Membrane Na+-K+ ATPase inhibition can produce immune activation, a component of autoimmunity. Mitochondrial dysfunction consequent to altered calcium/magnesium ratios and reduced ubiquinone levels can result in increased free radical generation and reduced free radical scavenging and defective apoptosis leading to abnormal synaptogenesis. Autism can thus be considered a syndrome of hypothalamic digoxin hypersecretion consequent to an upregulated isoprenoid pathway. The biochemical patterns including hyperdigoxinemia observed in autism correlated with those obtained in right hemispheric chemical dominance. Right hemispheric chemical dominance is a predisposing factor for autism.

The effect of neonatal N-methyl-D-aspartate receptor blockade on exploratory and anxiety-like behaviors in adult BALB/c and C57BL/6 mice.

PubMed

Akillioglu, Kubra; Binokay, Secil; Kocahan, Sayad

2012-07-15

N-methyl-D-aspartate (NMDA) receptors play an important role in brain maturation and developmental processes. In our study, we evaluated the effects of neonatal NMDA receptor blockade on exploratory locomotion and anxiety-like behaviors of adult BALB/c and C57BL/6 mice. In this study, NMDA receptor hypofunction was induced 7-10 days after birth using MK-801 in BALB/c and C57BL/6 mice (0.25mg/kg twice a day for 4 days via intraperitoneal injection). The open-field (OF) and elevated plus maze (EPM) tests were used to evaluate exploratory locomotion and anxiety-like behaviors. In the OF, BALB/c mice spent less time in the center of the field (p<0.05) and had less vertical locomotor activity (p<0.01) compared to C57BL/6 mice. In BALB/c mice, MK-801 caused a decrease in vertical and horizontal locomotor activity in the OF test, compared to the control group (p<0.05). In C57BL/6 mice, MK-801 treatment increased horizontal locomotor activity and decreased time spent in the center in the OF test (p<0.05). In the EPM, the number of open-arm entries, the percentage of open-arm time (p<0.01) and total arm entries (p<0.05) were lower in BALB/c mice compared to C57BL/6 mice. In BALB/c mice, MK-801 caused an increase in the percentage of open-arm time compared to the control group (p<0.05). In C57BL/6 mice, MK-801 caused a decrease in the percentage of open-arm time compared to the control group (p<0.05). MK-801 decreased exploratory and anxiety-like behaviors in BALB/c mice. In contrast, MK-801 increased exploratory and anxiety-like behaviors in C57BL/6 mice. In conclusion, hereditary factors may play an important role in neonatal NMDA receptor blockade-induced responses. Copyright © 2012 Elsevier B.V. All rights reserved.

GluN2B-containing NMDA receptors blockade rescues bidirectional synaptic plasticity in the bed nucleus of the stria terminalis of cocaine self-administering rats.

PubMed

deBacker, Julian; Hawken, Emily R; Normandeau, Catherine P; Jones, Andrea A; Di Prospero, Cynthia; Mechefske, Elysia; Gardner Gregory, James; Hayton, Scott J; Dumont, Éric C

2015-01-01

Drugs of abuse have detrimental effects on homeostatic synaptic plasticity in the motivational brain network. Bidirectional plasticity at excitatory synapses helps keep neural circuits within a functional range to allow for behavioral flexibility. Therefore, impaired bidirectional plasticity of excitatory synapses may contribute to the behavioral hallmarks of addiction, yet this relationship remains unclear. Here we tracked excitatory synaptic strength in the oval bed nucleus of the stria terminalis (ovBNST) using whole-cell voltage-clamp recordings in brain slices from rats self-administering sucrose or cocaine. In the cocaine group, we measured both a persistent increase in AMPA to NMDA ratio (A:N) and slow decay time of NMDA currents throughout the self-administration period and after withdrawal from cocaine. In contrast, the sucrose group exhibited an early increase in A:N ratios (acquisition) that returned toward baseline values with continued self-administration (maintenance) and after withdrawal. The sucrose rats also displayed a decrease in NMDA current decay time with continued self-administration (maintenance), which normalized after withdrawal. Cocaine self-administering rats exhibited impairment in NMDA-dependent long-term depression (LTD) that could be rescued by GluN2B-containing NMDA receptor blockade. Sucrose self-administering rats demonstrated no impairment in NMDA-dependent LTD. During the maintenance period of self-administration, in vivo (daily intraperitoneally for 5 days) pharmacologic blockade of GluN2B-containing NMDA receptors did not reduce lever pressing for cocaine. However, in vivo GluN2B blockade did normalize A:N ratios in cocaine self-administrating rats, and dissociated the magnitude of ovBNST A:N ratios from drug-seeking behavior after protracted withdrawal. Altogether, our data demonstrate when and how bidirectional plasticity at ovBNST excitatory synapses becomes dysfunctional with cocaine self-administration and that NMDA-mediated potentiation of AMPA receptors in this region may be part of the neural circuits of drug relapse.

CDKL5 controls postsynaptic localization of GluN2B-containing NMDA receptors in the hippocampus and regulates seizure susceptibility.

PubMed

Okuda, Kosuke; Kobayashi, Shizuka; Fukaya, Masahiro; Watanabe, Aya; Murakami, Takuto; Hagiwara, Mai; Sato, Tempei; Ueno, Hiroe; Ogonuki, Narumi; Komano-Inoue, Sayaka; Manabe, Hiroyuki; Yamaguchi, Masahiro; Ogura, Atsuo; Asahara, Hiroshi; Sakagami, Hiroyuki; Mizuguchi, Masashi; Manabe, Toshiya; Tanaka, Teruyuki

2017-10-01

Mutations in the Cyclin-dependent kinase-like 5 (CDKL5) gene cause severe neurodevelopmental disorders accompanied by intractable epilepsies, i.e. West syndrome or atypical Rett syndrome. Here we report generation of the Cdkl5 knockout mouse and show that CDKL5 controls postsynaptic localization of GluN2B-containing N-methyl-d-aspartate (NMDA) receptors in the hippocampus and regulates seizure susceptibility. Cdkl5 -/Y mice showed normal sensitivity to kainic acid; however, they displayed significant hyperexcitability to NMDA. In concordance with this result, electrophysiological analysis in the hippocampal CA1 region disclosed an increased ratio of NMDA/α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated excitatory postsynaptic currents (EPSCs) and a significantly larger decay time constant of NMDA receptor-mediated EPSCs (NMDA-EPSCs) as well as a stronger inhibition of the NMDA-EPSCs by the GluN2B-selective antagonist ifenprodil in Cdkl5 -/Y mice. Subcellular fractionation of the hippocampus from Cdkl5 -/Y mice revealed a significant increase of GluN2B and SAP102 in the PSD (postsynaptic density)-1T fraction, without changes in the S1 (post-nuclear) fraction or mRNA transcripts, indicating an intracellular distribution shift of these proteins to the PSD. Immunoelectron microscopic analysis of the hippocampal CA1 region further confirmed postsynaptic overaccumulation of GluN2B and SAP102 in Cdkl5 -/Y mice. Furthermore, ifenprodil abrogated the NMDA-induced hyperexcitability in Cdkl5 -/Y mice, suggesting that upregulation of GluN2B accounts for the enhanced seizure susceptibility. These data indicate that CDKL5 plays an important role in controlling postsynaptic localization of the GluN2B-SAP102 complex in the hippocampus and thereby regulates seizure susceptibility, and that aberrant NMDA receptor-mediated synaptic transmission underlies the pathological mechanisms of the CDKL5 loss-of-function. Copyright © 2017 Elsevier Inc. All rights reserved.

Gap-junction blocker carbenoxolone differentially enhances NMDA-induced cell death in hippocampal neurons and astrocytes in co-culture.

PubMed

Zündorf, Gregor; Kahlert, Stefan; Reiser, Georg

2007-07-01

The beneficial or detrimental role of gap junction communication in the pathophysiology of brain injury is still controversial. We used co-cultures of hippocampal astrocytes and neurons, where we identified homocellular astrocyte-astrocyte and heterocellular astrocyte-neuron coupling by fluorescence recovery after photobleaching, which was decreased by the gap junction blocker carbenoxolone (CBX). In these cultures, we determined the cell type-specific effects of CBX on the excitotoxic damage caused by N-methyl-D-aspartate (NMDA). We determined in both astrocytes and neurons the influence of CBX, alone or together with NMDA challenge, on cytotoxicity using propidium iodide labeling. CBX alone was not cytotoxic, but CBX treatment differentially accelerated the NMDA-induced cell death in both astrocytes and neurons. In addition, we measured mitochondrial potential using rhodamine 123, membrane potential using the oxonol dye bis(1,3-diethylthiobarbituric acid)trimethine oxonol, cytosolic Ca(2+) level using fura-2, and formation of reactive oxygen species (ROS) using dihydroethidium. CBX alone induced neither an intracellular Ca(2+) rise nor a membrane depolarization. However, CBX elicited a mitochondrial depolarization in both astrocytes and neurons and increased the ROS formation in neurons. In contrast, NMDA caused a membrane depolarization in neurons, coinciding with intracellular Ca(2+) rise, but neither mitochondrial depolarization nor ROS production seem to be involved in NMDA-mediated cytotoxicity. Pre-treatment with CBX accelerated the NMDA-induced membrane depolarization and prevented the repolarization of neurons after the NMDA challenge. We hypothesize that these effects are possibly mediated via blockage of gap junctions, and might be involved in the mechanism of CBX-induced acceleration of excitotoxic cell death, whereas the CBX-induced mitochondrial depolarization and ROS formation are not responsible for the increase in cytotoxicity. We conclude that both in astrocytes and neurons gap junctions provide protection against NMDA-induced cytotoxicity.

Seizure-like activity leads to the release of BAD from 14-3-3 protein and cell death in hippocampal neurons in vitro.

PubMed

Meller, R; Schindler, C K; Chu, X P; Xiong, Z G; Cameron, J A; Simon, R P; Henshall, D C

2003-05-01

Seizure-induced neuronal death may involve engagement of the BCL-2 family of apoptosis-regulating proteins. In the present study we examined the activation of proapoptotic BAD in cultured hippocampal neurons following seizures induced by removal of chronic glutamatergic transmission blockade. Kynurenic acid withdrawal elicited an increase in seizure-like electrical activity, which was inhibited by blockers of AMPA (CNQX) and NMDA (MK801 and AP5) receptor function. However, only NMDA receptor antagonists inhibited calcium entry as assessed by fura-2, and cell death of hippocampal neurons. Seizures increased proteolysis of caspase-3 and terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) of cells. Seizure-like activity induced dephosphorylation of BAD and the disruption of its constitutive interaction with 14-3-3 proteins. In turn, BAD dimerized with antiapoptotic BCL-Xl after seizures. However, the absence of neuroprotective effects of pathway intervention suggests that BAD may perform a reinforcement rather than instigator role in cell death following seizures in vitro.

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.

The Calmodulin-Binding Transcription Activator CAMTA1 Is Required for Long-Term Memory Formation in Mice

ERIC Educational Resources Information Center

Bas-Orth, Carlos; Tan, Yan-Wei; Oliveira, Ana M. M.; Bengtson, C. Peter; Bading, Hilmar

2016-01-01

The formation of long-term memory requires signaling from the synapse to the nucleus to mediate neuronal activity-dependent gene transcription. Synapse-to-nucleus communication is initiated by influx of calcium ions through synaptic NMDA receptors and/or L-type voltage-gated calcium channels and involves the activation of transcription factors by…

Differential regulation of NMDA receptor-expressing neurons in the rat hippocampus and striatum following bilateral vestibular loss demonstrated using flow cytometry.

PubMed

Benoit, Alice; Besnard, Stephane; Guillamin, Maryline; Philoxene, Bruno; Sola, Brigitte; Le Gall, Anne; Machado, Marie-Laure; Toulouse, Joseph; Hitier, Martin; Smith, Paul F

2018-06-21

There is substantial evidence that loss of vestibular function impairs spatial learning and memory related to hippocampal (HPC) function, as well as increasing evidence that striatal (Str) plasticity is also implicated. Since the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor is considered essential to spatial memory, previous studies have investigated whether the expression of HPC NMDA receptors changes following vestibular loss; however, the results have been contradictory. Here we used a novel flow cytometric method to quantify the number of neurons expressing NMDA receptors in the HPC and Str following bilateral vestibular loss (BVL) in rats. At 7 and 30 days post-op., there was a significant increase in the number of HPC neurons expressing NMDA receptors in the BVL animals, compared to sham controls (P ≤ 0.004 and P ≤ 0.0001, respectively). By contrast, in the Str, at 7 days there was a significant reduction in the number of neurons expressing NMDA receptors in the BVL group (P ≤ 0.05); however, this difference had disappeared by 30 days post-op. These results suggest that BVL causes differential changes in the number of neurons expressing NMDA receptors in the HPC and Str, which may be related to its long-term impairment of spatial memory. Copyright © 2018. Published by Elsevier B.V.

Prolonged Exposure to NMDAR Antagonist Induces Cell-type Specific Changes of Glutamatergic Receptors in Rat Prefrontal Cortex

PubMed Central

Wang, Huai-Xing; Gao, Wen-Jun

2011-01-01

N-methyl-D-aspartic acid (NMDA) receptors are critical for both normal brain functions and the pathogenesis of schizophrenia. We investigated the functional changes of glutamatergic receptors in the pyramidal cells and fast-spiking (FS) interneurons in the adolescent rat prefrontal cortex in MK-801 model of schizophrenia. We found that although both pyramidal cells and FS interneurons were affected by in vivo subchronic blockade of NMDA receptors, MK-801 induced distinct changes in αamino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and NMDA receptors in the FS interneurons compared with pyramidal cells. Specifically, the amplitude, but not the frequency, of AMPA-mediated miniature excitatory postsynaptic currents (mEPSCs) in FS interneurons was significantly decreased whereas both the frequency and amplitude in pyramidal neurons were increased. In addition, MK-801-induced new presynaptic NMDA receptors were detected in the glutamatergic terminals targeting pyramidal neurons but not FS interneurons. MK-801 also induced distinct alterations in FS interneurons but not in pyramidal neurons, including significantly decreased rectification index and increased calcium permeability. These data suggest a distinct cell-type specific and homeostatic synaptic scaling and redistribution of AMPA and NMDA receptors in response to the subchronic blockade of NMDA receptors and thus provide a direct mechanistic explanation for the NMDA hypofunction hypothesis that have long been proposed for the schizophrenia pathophysiology. PMID:22182778

Fluoxetine reverses the behavioral despair induced by neurogenic stress in mice: role of N-methyl-d-aspartate and opioid receptors.

PubMed

Haj-Mirzaian, Arya; Kordjazy, Nastaran; Ostadhadi, Sattar; Amiri, Shayan; Haj-Mirzaian, Arvin; Dehpour, AhmadReza

2016-06-01

Opioid and N-methyl-d-aspartate (NMDA) receptors mediate different effects of fluoxetine. We investigated whether opioid and NMDA receptors are involved in the protective effect of fluoxetine against the behavioral despair induced by acute physical stress in male mice. We used the forced swimming test (FST), tail suspension test (TST), and open-field test (OFT) for behavioral evaluation. We used fluoxetine, naltrexone (opioid receptor antagonist), MK-801 (NMDA receptor antagonist), morphine (opioid receptor agonist), and NMDA (NMDA receptor agonist). Acute foot-shock stress (FSS) significantly induced behavioral despair (depressive-like) and anxiety-like behaviors in tests. Fluoxetine (5 mg/kg) reversed the depressant-like effect of FSS, but it did not alter the locomotion and anxiety-like behavior in animals. Acute administration of subeffective doses of naltrexone (0.3 mg/kg) or MK-801 (0.01 mg/kg) potentiated the antidepressant-like effect of fluoxetine, while subeffective doses of morphine (1 mg/kg) and NMDA (75 mg/kg) abolished this effect of fluoxetine. Also, co-administration of subeffective doses of naltrexone (0.05 mg/kg) and MK-801 (0.003 mg/kg) with fluoxetine (1 mg/kg) induced a significant decrease in the immobility time in FST and TST. Our results showed that opioid and NMDA receptors (alone or in combination) are involved in the antidepressant-like effect of fluoxetine against physical stress.

Involvement of NMDA receptors in the antidepressant-like effect of tramadol in the mouse forced swimming test.

PubMed

Ostadhadi, Sattar; Norouzi-Javidan, Abbas; Chamanara, Mohsen; Akbarian, Reyhaneh; Imran-Khan, Muhammad; Ghasemi, Mehdi; Dehpour, Ahmad-Reza

2017-09-01

Tramadol is an analgesic agent that is mainly used to treat moderate to severe pain. There is evidence that tramadol may have antidepressant property. However, the mechanisms underlying the antidepressant effects of tramadol have not been elucidated yet. Considering that fact that N-methyl-d-aspartate (NMDA) receptor signaling may play an important role in the pathophysiology of depression, the aim of the present study was to investigate the role of NMDA receptor signaling in the possible antidepressant-like effects of tramadol in the mouse forced swimming test (mFST). We found that tramadol exerted antidepressant-like effects at high dose (40mg/kg, intraperitoneally [i.p.]) in the mFST. Co-administration of non-effective doses of NMDA receptor antagonists (ketamine [1mg/kg, i.p.], MK-801 [0.05mg/kg, i.p.], or magnesium sulfate [10mg/kg, i.p.]) with sub-effective dose of tramadol (20mg/kg, i.p.) exerted significant antidepressant-like effects in the mFST. The antidepressant-like effects of tramadol (40mg/kg) was also inhibited by pre-treatment with non-effective dose of the NMDA receptor agonist NMDA (75mg/kg, i.p.). Our data suggest a role for NMDA receptor signaling in the antidepressant-like effects of tramadol in the mFST. Copyright © 2017 Elsevier Inc. All rights reserved.

Glycine aggravates ischemia reperfusion-induced acute kidney injury through N-Methyl-D-Aspartate receptor activation in rats.

PubMed

Arora, Shiyana; Kaur, Tajpreet; Kaur, Anudeep; Singh, Amrit Pal

2014-08-01

The present study was designed to investigate the role of glycine in ischemia reperfusion-induced acute kidney injury (AKI) in rats. The AKI was induced in rats by occluding renal pedicles for 40 min followed by reperfusion for 24 h. The AKI was assessed by measuring creatinine clearance, blood urea nitrogen, plasma uric acid, potassium, fractional excretion of sodium, and microproteinuria. The oxidative stress in renal tissues was assessed by quantification of myeloperoxidase activity, thiobarbituric acid-reactive substances, superoxide anion generation, and reduced glutathione level. Glycine (100, 200, and 400 mg/kg, i.p.) was administered to rats 30 min before subjecting to AKI. The glycinergic receptor blocker, strychnine (0.75 mg/kg i.p.), and glycine-binding site blocker at N-methyl-D-aspartate (NMDA) receptor, kynurenic acid (300 and 600 mg/kg i.p.), were used in the present study. The ischemia reperfusion induced AKI as witnessed by significant change in plasma, urinary, and tissue parameters employed in the present study. Glycine treatment increased ischemia reperfusion-induced AKI. The treatment with strychnine did not show any protection, whereas kynurenic acid ameliorated renal ischemia reperfusion-induced AKI. The results obtained in present study suggest that glycine increases ischemia reperfusion-induced renal damage through NMDA receptor agonism rather than strychnine-sensitive glycinergic receptors. Hence, it is concluded that glycine aggravates ischemia reperfusion-induced AKI. In addition, the activation of strychnine-insensitive glycine-binding site of NMDA receptors is responsible for its renal-damaging effect rather than strychnine-sensitive glycinergic receptors.

Alleviation of chronic pain following rat spinal cord compression injury with multimodal actions of huperzine A

PubMed Central

Yu, Dou; Thakor, Devang K.; Han, Inbo; Ropper, Alexander E.; Haragopal, Hariprakash; Sidman, Richard L.; Zafonte, Ross; Schachter, Steven C.; Teng, Yang D.

2013-01-01

Diverse mechanisms including activation of NMDA receptors, microglial activation, reactive astrogliosis, loss of descending inhibition, and spasticity are responsible for ∼40% of cases of intractable neuropathic pain after spinal cord injury (SCI). Because conventional treatments blocking individual mechanisms elicit only short-term effectiveness, a multimodal approach with simultaneous actions against major pain-related pathways may have value for clinical management of chronic pain. We hypothesize that [-]-huperzine A (HUP-A), an alkaloid isolated from the club moss Huperzia serrata, that is a potent reversible inhibitor of acetylcholinesterase and NMDA receptors, could mitigate pain without invoking drug tolerance or dependence by stimulating cholinergic interneurons to impede pain signaling, inhibiting inflammation via microglial cholinergic activation, and blocking NMDA-mediated central hypersensitization. We tested our hypothesis by administering HUP-A i.p. or intrathecally to female Sprague–Dawley rats (200–235 g body weight) after moderate static compression (35 g for 5 min) of T10 spinal cord. Compared with controls, HUP-A treatment demonstrates significant analgesic effects in both regimens. SCI rats manifested no drug tolerance following repeated bolus i.p. or chronic intrathecal HUP-A dosing. The pain-ameliorating effect of HUP-A is cholinergic dependent. Relative to vehicle treatment, HUP-A administration also reduced neural inflammation, retained higher numbers of calcium-impermeable GluR2-containing AMPA receptors, and prevented Homer1a up-regulation in dorsal horn sensory neurons. Therefore, HUP-A may provide safe and effective management for chronic postneurotrauma pain by reestablishing homeostasis of sensory circuits. PMID:23386718

Alleviation of chronic pain following rat spinal cord compression injury with multimodal actions of huperzine A.

PubMed

Yu, Dou; Thakor, Devang K; Han, Inbo; Ropper, Alexander E; Haragopal, Hariprakash; Sidman, Richard L; Zafonte, Ross; Schachter, Steven C; Teng, Yang D

2013-02-19

Diverse mechanisms including activation of NMDA receptors, microglial activation, reactive astrogliosis, loss of descending inhibition, and spasticity are responsible for ∼40% of cases of intractable neuropathic pain after spinal cord injury (SCI). Because conventional treatments blocking individual mechanisms elicit only short-term effectiveness, a multimodal approach with simultaneous actions against major pain-related pathways may have value for clinical management of chronic pain. We hypothesize that [-]-huperzine A (HUP-A), an alkaloid isolated from the club moss Huperzia serrata, that is a potent reversible inhibitor of acetylcholinesterase and NMDA receptors, could mitigate pain without invoking drug tolerance or dependence by stimulating cholinergic interneurons to impede pain signaling, inhibiting inflammation via microglial cholinergic activation, and blocking NMDA-mediated central hypersensitization. We tested our hypothesis by administering HUP-A i.p. or intrathecally to female Sprague-Dawley rats (200-235 g body weight) after moderate static compression (35 g for 5 min) of T10 spinal cord. Compared with controls, HUP-A treatment demonstrates significant analgesic effects in both regimens. SCI rats manifested no drug tolerance following repeated bolus i.p. or chronic intrathecal HUP-A dosing. The pain-ameliorating effect of HUP-A is cholinergic dependent. Relative to vehicle treatment, HUP-A administration also reduced neural inflammation, retained higher numbers of calcium-impermeable GluR2-containing AMPA receptors, and prevented Homer1a up-regulation in dorsal horn sensory neurons. Therefore, HUP-A may provide safe and effective management for chronic postneurotrauma pain by reestablishing homeostasis of sensory circuits.

Fear extinction induces mGluR5-mediated synaptic and intrinsic plasticity in infralimbic neurons

PubMed Central

Sepulveda-Orengo, Marian T.; Lopez, Ana V.; Soler-Cedeño, Omar; Porter, James T.

2013-01-01

Studies suggest that plasticity in the infralimbic prefrontal cortex (IL) in rodents and its homolog in humans is necessary for inhibition of fear during the recall of fear extinction. The recall of extinction is impaired by locally blocking metabotropic glutamate receptor type 5 (mGluR5) activation in IL during extinction training. This finding suggests that mGluR5 stimulation may lead to IL plasticity needed for fear extinction. To test this hypothesis, we recorded AMPA and NMDA currents, AMPA receptor rectification, and intrinsic excitability in IL pyramidal neurons in slices from trained rats using whole-cell patch-clamp. We observed that fear extinction increases the AMPA/NMDA ratio, consistent with insertion of AMPA receptors into IL synapses. In addition, extinction training increased inward rectification, suggesting that extinction induces the insertion of calcium-permeable (GluA2-lacking) AMPA receptors into IL synapses. Consistent with this, selectively blocking calcium-permeable AMPA receptors with Naspm reduced the AMPA EPSCs in IL neurons to a larger degree after extinction. Extinction-induced changes in AMPA/NMDA ratio, rectification, and intrinsic excitability were blocked with an mGluR5 antagonist. Together, these findings suggest that mGluR5 activation leads to consolidation of fear extinction by regulating the intrinsic excitability of IL neurons and modifying the composition of AMPA receptors in IL synapses. Consequently, impaired mGluR5 activity in IL synapses could be one factor that causes inappropriate modulation of fear expression leading to anxiety disorders. PMID:23616528

N-Methyl-D aspartate receptor-mediated effect on glucose transporter-3 levels of high glucose exposed-SH-SY5Y dopaminergic neurons.

PubMed

Engin, Ayse Basak; Engin, Evren Doruk; Karakus, Resul; Aral, Arzu; Gulbahar, Ozlem; Engin, Atilla

2017-11-01

High glucose and insulin lead to neuronal insulin resistance. Glucose transport into the neurons is achieved by regulatory induction of surface glucose transporter-3 (GLUT3) instead of the insulin. N-methyl-D aspartate (NMDA) receptor activity increases GLUT3 expression. This study explored whether an endogenous NMDA receptor antagonist, kynurenic acid (KynA) affects the neuronal cell viability at high glucose concentrations. SH-SY5Y neuroblastoma cells were exposed to 150-250 mg/dL glucose and 40 μU/mL insulin. In KynA and N-nitro-l-arginine methyl ester (L-NAME) supplemented cultures, oxidative stress, mitochondrial metabolic activity (MTT), nitric oxide as nitrite+nitrate (NOx) and GLUT3 were determined at the end of 24 and 48-h incubation periods. Viable cells were counted by trypan blue dye. High glucose-exposed SH-SY5Y cells showed two-times more GLUT3 expression at second 24-h period. While GLUT3-stimulated glucose transport and oxidative stress was increased, total mitochondrial metabolic activity was significantly reduced. Insulin supplementation to high glucose decreased NOx synthesis and GLUT3 levels, in contrast oxidative stress increased three-fold. KynA significantly reduced oxidative stress, and increased MTT by regulating NOx production and GLUT3 expression. KynA is a noteworthy compound, as an endogenous, specific NMDA receptor antagonist; it significantly reduces oxidative stress, while increasing cell viability at high glucose and insulin concentrations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of an NMDA antagonist on the auditory mismatch negativity response to transcranial direct current stimulation.

PubMed

Impey, Danielle; de la Salle, Sara; Baddeley, Ashley; Knott, Verner

2017-05-01

Transcranial direct current stimulation (tDCS) is a non-invasive form of brain stimulation which uses a weak constant current to alter cortical excitability and activity temporarily. tDCS-induced increases in neuronal excitability and performance improvements have been observed following anodal stimulation of brain regions associated with visual and motor functions, but relatively little research has been conducted with respect to auditory processing. Recently, pilot study results indicate that anodal tDCS can increase auditory deviance detection, whereas cathodal tDCS decreases auditory processing, as measured by a brain-based event-related potential (ERP), mismatch negativity (MMN). As evidence has shown that tDCS lasting effects may be dependent on N-methyl-D-aspartate (NMDA) receptor activity, the current study investigated the use of dextromethorphan (DMO), an NMDA antagonist, to assess possible modulation of tDCS's effects on both MMN and working memory performance. The study, conducted in 12 healthy volunteers, involved four laboratory test sessions within a randomised, placebo and sham-controlled crossover design that compared pre- and post-anodal tDCS over the auditory cortex (2 mA for 20 minutes to excite cortical activity temporarily and locally) and sham stimulation (i.e. device is turned off) during both DMO (50 mL) and placebo administration. Anodal tDCS increased MMN amplitudes with placebo administration. Significant increases were not seen with sham stimulation or with anodal stimulation during DMO administration. With sham stimulation (i.e. no stimulation), DMO decreased MMN amplitudes. Findings from this study contribute to the understanding of underlying neurobiological mechanisms mediating tDCS sensory and memory improvements.

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.

MPX-004 and MPX-007: New Pharmacological Tools to Study the Physiology of NMDA Receptors Containing the GluN2A Subunit.

PubMed

Volkmann, Robert A; Fanger, Christopher M; Anderson, David R; Sirivolu, Venkata Ramana; Paschetto, Kathy; Gordon, Earl; Virginio, Caterina; Gleyzes, Melanie; Buisson, Bruno; Steidl, Esther; Mierau, Susanna B; Fagiolini, Michela; Menniti, Frank S

2016-01-01

GluN2A is the most abundant of the GluN2 NMDA receptor subunits in the mammalian CNS. Physiological and genetic evidence implicate GluN2A-containing receptors in susceptibility to autism, schizophrenia, childhood epilepsy and neurodevelopmental disorders such as Rett Syndrome. However, GluN2A-selective pharmacological probes to explore the therapeutic potential of targeting these receptors have been lacking. Here we disclose a novel series of pyrazine-containing GluN2A antagonists exemplified by MPX-004 (5-(((3-chloro-4-fluorophenyl)sulfonamido)methyl)-N-((2-methylthiazol-5-yl)methyl)pyrazine-2-carboxamide) and MPX-007 (5-(((3-fluoro-4-fluorophenyl)sulfonamido)methyl)-N-((2-methylthiazol-5-yl)methyl)methylpyrazine-2-carboxamide). MPX-004 and MPX-007 inhibit GluN2A-containing NMDA receptors expressed in HEK cells with IC50s of 79 nM and 27 nM, respectively. In contrast, at concentrations that completely inhibited GluN2A activity these compounds have no inhibitory effect on GluN2B or GluN2D receptor-mediated responses in similar HEK cell-based assays. Potency and selectivity were confirmed in electrophysiology assays in Xenopus oocytes expressing GluN2A-D receptor subtypes. Maximal concentrations of MPX-004 and MPX-007 inhibited ~30% of the whole-cell current in rat pyramidal neurons in primary culture and MPX-004 inhibited ~60% of the total NMDA receptor-mediated EPSP in rat hippocampal slices. GluN2A-selectivity at native receptors was confirmed by the finding that MPX-004 had no inhibitory effect on NMDA receptor mediated synaptic currents in cortical slices from GRIN2A knock out mice. Thus, MPX-004 and MPX-007 offer highly selective pharmacological tools to probe GluN2A physiology and involvement in neuropsychiatric and developmental disorders.

mGluR2/3 agonist LY379268 rescues NMDA and GABAA receptor level deficits induced in a two-hit mouse model of schizophrenia.

PubMed

Engel, Martin; Snikeris, Peta; Matosin, Natalie; Newell, Kelly Anne; Huang, Xu-Feng; Frank, Elisabeth

2016-04-01

An imbalance of excitatory and inhibitory neurotransmission underlies the glutamate hypothesis of schizophrenia. Agonists of group II metabotropic glutamate receptors, mGluR2/3, have been proposed as novel therapeutic agents to correct this imbalance. However, the influence of mGluR2/3 activity on excitatory and inhibitory neurotransmitter receptors has not been explored. We aimed to investigate the ability of a novel mGluR2/3 agonist, LY379268, to modulate the availability of the excitatory N-methyl-D-aspartate receptor (NMDA-R) and the inhibitory gamma-aminobutyrate-A receptor (GABAA-R), in a two-hit mouse model of schizophrenia. Wild type (WT) and heterozygous neuregulin 1 transmembrane domain mutant mice (NRG1 HET) were treated daily with phencyclidine (10 mg/kg ip) or saline for 14 days. After a 14-day washout, an acute dose of the mGluR2/3 agonist LY379268 (3 mg/kg), olanzapine (antipsychotic drug comparison, 1.5 mg/kg), or saline was administered. NMDA-R and GABAA-R binding densities were examined by receptor autoradiography in several schizophrenia-relevant brain regions. In both WT and NRG1 HET mice, phencyclidine treatment significantly reduced NMDA-R and GABAA-R binding density in the prefrontal cortex, hippocampus, and nucleus accumbens. Acute treatment with LY379268 restored NMDA-R and GABAA-R levels in the two-hit mouse model comparable to olanzapine. We demonstrate that the mGluR2/3 agonist LY379268 restores excitatory and inhibitory deficits with similar efficiency as olanzapine in our two-hit schizophrenia mouse model. This study significantly contributes to our understanding of the mechanisms underlying the therapeutic effects of LY379268 and supports the use of agents aimed at mGluR2/3.

Involvement of NMDA receptors and L-arginine/nitric oxide/cyclic guanosine monophosphate pathway in the antidepressant-like effects of topiramate in mice forced swimming test.

PubMed

Ostadhadi, Sattar; Khan, Muhammad Imran; Norouzi-Javidan, Abbas; Chamanara, Mohsen; Jazaeri, Farahnaz; Zolfaghari, Samira; Dehpour, Ahmad-Reza

2016-04-01

Topiramate (TPM) is an agent primarily used in the treatment of epilepsy. Using mice model of forced swimming test (FST) the current study was basically aimed to investigate the influence of TPM on depression by inhibiting NMDA receptor and nitric oxide-cGMP production. When TPM was administered in a dose of 20 and 30 mg/kg by i.p. route it reduced the immobility time during FST. However this effect of TPM (30 mg/kg, i.p.) in the FST was abolished when the mice were pretreated either with NMDA (75 mg/kg, i.p.), or l-arginine (750 mg/kg, i.p. NO precursor), or sildenafil (5mg/kg, i.p. Phosphodiesterase 5 inhibitor). The immobility time in the FST was reduced after administration of L-NAME (10mg/kg, i.p, a non-specific NOS inhibitor), 7-nitoinidazol (30 mg/kg, i.p. a nNOS inhibitor) or MK-801 (0.05 mg/kg, i.p, a NMDA receptor antagonist) in combination with a subeffective dose of TPM (10mg/kg, i.p.) as compared with single use of either drug. Co-administrated of lower doses of MK-801 (0.01 mg/kg) or L-NAME (1mg/kg) failed to effect immobility time. However, simultaneous administration of these two agents in the same doses with subeffective dose of TPM (10mg/kg, i.p.), reduced the immobility time during FST. None of these drugs were found to have a profound effect on the locomotor activity per se during the open field test. Taken together, our data demonstrates that TPM exhibit antidepressant-like effect which is accomplished either due to inhibition of NMDA receptors or NO-cGMP production. Copyright © 2016 Elsevier Inc. All rights reserved.

The qEEG Signature of Selective NMDA NR2B Negative Allosteric Modulators; A Potential Translational Biomarker for Drug Development

PubMed Central

Keavy, Deborah; Bristow, Linda J.; Sivarao, Digavalli V.; Batchelder, Margaret; King, Dalton; Thangathirupathy, Srinivasan; Macor, John E.; Weed, Michael R.

2016-01-01

The antidepressant activity of the N-methyl-D-aspartate (NMDA) receptor channel blocker, ketamine, has led to the investigation of negative allosteric modulators (NAMs) selective for the NR2B receptor subtype. The clinical development of NR2B NAMs would benefit from a translational pharmacodynamic biomarker that demonstrates brain penetration and functional inhibition of NR2B receptors in preclinical species and humans. Quantitative electroencephalography (qEEG) is a translational measure that can be used to demonstrate pharmacodynamic effects across species. NMDA receptor channel blockers, such as ketamine and phencyclidine, increase the EEG gamma power band, which has been used as a pharmacodynamic biomarker in the development of NMDA receptor antagonists. However, detailed qEEG studies with ketamine or NR2B NAMs are lacking in nonhuman primates. The aim of the present study was to determine the effects on the qEEG power spectra of the NR2B NAMs traxoprodil (CP-101,606) and BMT-108908 in nonhuman primates, and to compare them to the NMDA receptor channel blockers, ketamine and lanicemine. Cynomolgus monkeys were surgically implanted with EEG radio-telemetry transmitters, and qEEG was measured after vehicle or drug administration. The relative power for a number of frequency bands was determined. Ketamine and lanicemine increased relative gamma power, whereas the NR2B NAMs traxoprodil and BMT-108908 had no effect. Robust decreases in beta power were elicited by ketamine, traxoprodil and BMT-108908; and these agents also produced decreases in alpha power and increases in delta power at the doses tested. These results suggest that measurement of power spectra in the beta and delta bands may represent a translational pharmacodynamic biomarker to demonstrate functional effects of NR2B NAMs. The results of these studies may help guide the selection of qEEG measures that can be incorporated into early clinical evaluation of NR2B NAMs in healthy humans. PMID:27035340

Modafinil: A Molecule of Military Interest

DTIC Science & Technology

2001-06-01

noradrenalin LC: locus coeruleus iR-Glu: ionotropic MCn: magnocellular nucleus glutamate receptors (NMDA and non-NMDA) DR: dorsal raphe mR-Glu: metabotropic ...21 This metabotropic receptor agonist. However, the EAA- inhibition of cortical GABA outflow is antagonized release inhibitor propentofylline has...NMDA receptor antagonist and metabotropic psychostimulant, during a sixty-hour sleep receptor agonist. deprivation experiment. Fundam Clin Pharmacol

Experience-enabled enhancement of adult visual cortex function.

PubMed

Tschetter, Wayne W; Alam, Nazia M; Yee, Christopher W; Gorz, Mario; Douglas, Robert M; Sagdullaev, Botir; Prusky, Glen T

2013-03-20

We previously reported in adult mice that visuomotor experience during monocular deprivation (MD) augmented enhancement of visual-cortex-dependent behavior through the non-deprived eye (NDE) during deprivation, and enabled enhanced function to persist after MD. We investigated the physiological substrates of this experience-enabled form of adult cortical plasticity by measuring visual behavior and visually evoked potentials (VEPs) in binocular visual cortex of the same mice before, during, and after MD. MD on its own potentiated VEPs contralateral to the NDE during MD and shifted ocular dominance (OD) in favor of the NDE in both hemispheres. Whereas we expected visuomotor experience during MD to augment these effects, instead enhanced responses contralateral to the NDE, and the OD shift ipsilateral to the NDE were attenuated. However, in the same animals, we measured NMDA receptor-dependent VEP potentiation ipsilateral to the NDE during MD, which persisted after MD. The results indicate that visuomotor experience during adult MD leads to enduring enhancement of behavioral function, not simply by amplifying MD-induced changes in cortical OD, but through an independent process of increasing NDE drive in ipsilateral visual cortex. Because the plasticity is resident in the mature visual cortex and selectively effects gain of visual behavior through experiential means, it may have the therapeutic potential to target and non-invasively treat eye- or visual-field-specific cortical impairment.

Decrement of GABAA receptor-mediated inhibitory postsynaptic currents in dentate granule cells in epileptic hippocampus.

PubMed

Isokawa, M

1996-05-01

1. Inhibitory postsynaptic currents (IPSCs) were studied in hippocampal dentate granule cells (DGCs) in the pilocarpine model and human temporal lobe epilepsy, with the use of the whole cell patch-clamp recording technique in slice preparations. 2. In the pilocarpine model, hippocampal slices were prepared from rats that were allowed to experience spontaneous seizures for 2 mo. Human hippocampal specimens were obtained from epileptic patients who underwent surgical treatment for medically intractable seizures. 3. IPSCs were generated by single perforant path stimulation and recorded at a membrane potential (Vm) of 0 mV near the reversal potential of glutamate excitatory postsynaptic currents in the voltage-clamp recording. IPSCs were pharmacologically identified as gamma-aminobutyric acid-A (GABAA) IPSCs by 10 microM bicuculline methiodide. 4. During low-frequency stimulation, IPSCs were not different in amplitude among non-seizure-experienced rat hippocampi, human nonsclerotic hippocampi, seizure-experienced rat hippocampi, and human sclerotic hippocampi. In the last two groups of DGCs, current-clamp recordings indicated the presence of prolonged excitatory postsynaptic potentials (EPSPs) mediated by the N-methyl-D-aspartate (NMDA) receptor. 5. High-frequency stimulation, administered at Vm = -30 mV to activate NMDA currents, reduced GABAA IPSC amplitude specifically in seizure-experienced rat hippocampi (t = 2.5, P < 0.03) and human sclerotic hippocampi (t = 7.7, P < 0.01). This reduction was blocked by an NMDA receptor antagonist, 2-amino-5-phosphonovaleric acid (APV) (50 microM). The time for GABAA IPSCs to recover to their original amplitude was also shortened by the application of APV. 6. I conclude that, when intensively activated, NMDA receptor-mediated excitatory transmission may interact with GABAergic synaptic inhibition in DGCs in seizure-experienced hippocampus to transiently reduce GABA(A) receptor-channel function. Such interactions may contribute to give rise to epileptic excitation in chronically seizure-prone hippocampus.

Slow-pressor angiotensin II hypertension and concomitant dendritic NMDA receptor trafficking in estrogen receptor beta-containing neurons of the mouse hypothalamic paraventricular nucleus are sex and age dependent

PubMed Central

Marques-Lopes, Jose; Van Kempen, Tracey; Waters, Elizabeth M.; Pickel, Virginia M.; Iadecola, Costantino; Milner, Teresa A.

2014-01-01

The incidence of hypertension increases after menopause. Similar to humans, “slow-pressor” doses of angiotensin II (AngII) increase blood pressure in young males, but not in young female mice. However, AngII increases blood pressure in aged female mice, paralleling reproductive hormonal changes. These changes could influence receptor trafficking in central cardiovascular circuits and contribute to hypertension. Increased post-synaptic NMDA receptor activity in the hypothalamic paraventricular nucleus (PVN) is crucial for the sympathoexcitation driving AngII hypertension. Estrogen receptors beta (ERβ) are present in PVN neurons. We tested the hypothesis that changes in ovarian hormones with age promote susceptibility to AngII hypertension, and influence NMDA receptor NR1 subunit trafficking in ERβ-containing PVN neurons. Transgenic mice expressing enhanced green fluorescent protein (EGFP) in ERβ-containing cells were implanted with osmotic minipumps delivering AngII (600 ng/kg/min) or saline for 2 weeks. AngII increased blood pressure in 2 month-old males and 18 month-old females, but not in 2 month-old females. By electron microscopy, NR1-silver-intensified immunogold (SIG) was mainly in ERβ-EGFP dendrites. At baseline, NR1-SIG density was greater in 2 month-old females than in 2 month-old males or 18 month-old females. After AngII infusion, NR1-SIG density was decreased in 2 month-old females, but increased in 2 month-old males and 18 month-old females. These findings suggest that, in young female mice, NR1 density is decreased in ERβ-PVN dendrites thus reducing NMDA receptor activity and preventing hypertension. Conversely, in young males and aged females, NR1 density is upregulated in ERβ-PVN dendrites and ultimately leads to the neurohumoral dysfunction driving hypertension. PMID:24639345

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

NMDA-receptor blockade by CPP impairs post-training consolidation of a rapidly acquired spatial representation in rat hippocampus.

PubMed

McDonald, Robert J; Hong, Nancy S; Craig, Laura A; Holahan, Matthew R; Louis, Meira; Muller, Robert U

2005-09-01

Recent evidence suggests that N-methyl-D-aspartate (NMDA)-receptor mediated plasticity in hippocampus has a more subtle role in memory-based behaviours than originally thought. One idea is that NMDA-based plasticity is essential for the consolidation of post-training memory but not for the initial encoding or for short-term memory. To further test this idea we used a three-phase variant of the hidden goal water maze task. In the first phase, rats were pre-trained to an initial location. Next, intense, massed training was done in a 2-h interval to teach the rats to go to a new location after either an injection of the NMDA receptor antagonist (6)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) or of vehicle. Finally, under drug-free conditions 24 h after new location training, a competition test was done between the original and new locations. We find that N-methyl-D-aspartate (NMDA)-receptor blockade has little or no effect on new location training. In contrast, when tested 24 h later, the strength of the trace for the new location learned during NMDA-receptor blockade was much weaker compared with the trace for the new location learned after saline injection. Further experiments showed similar effects when NMDA-receptors were blocked immediately after the new location training, suggesting that this is a memory consolidation effect. Our results therefore reinforce the notion that hippocampal NMDA-receptors participate in post-training memory consolidation but are not essential for the processes necessary to learn or retain navigational information in the short term.

Common influences of non-competitive NMDA receptor antagonists on the consolidation and reconsolidation of cocaine-cue memory.

PubMed

Alaghband, Yasaman; Marshall, John F

2013-04-01

Environmental stimuli or contexts previously associated with rewarding drugs contribute importantly to relapse among addicts, and research has focused on neurobiological processes maintaining those memories. Much research shows contributions of cell surface receptors and intracellular signaling pathways in maintaining associations between rewarding drugs (e.g., cocaine) and concurrent cues/contexts; these memories can be degraded at the time of their retrieval through reconsolidation interference. Much less studied is the consolidation of drug-cue memories during their acquisition. The present experiments use the cocaine-conditioned place preference (CPP) paradigm in rats to directly compare, in a consistent setting, the effects of N-methyl-D-aspartate (NMDA) glutamate receptor antagonists MK-801 and memantine on the consolidation and reconsolidation of cocaine-cue memories. For the consolidation studies, animals were systemically administered MK-801 or memantine immediately following training sessions. To investigate the effects of these NMDA receptor antagonists on the retention of previously established cocaine-cue memories, animals were systemically administered MK-801 or memantine immediately after memory retrieval. Animals given either NMDA receptor antagonist immediately following training sessions did not establish a preference for the cocaine-paired compartment. Post-retrieval administration of either NMDA receptor antagonist attenuated the animals' preference for the cocaine-paired compartment. Furthermore, animals given NMDA receptor antagonists post-retrieval showed a blunted response to cocaine-primed reinstatement. Using two distinct NMDA receptor antagonists in a common setting, these findings demonstrate that NMDA receptor-dependent processes contribute both to the consolidation and reconsolidation of cocaine-cue memories, and they point to the potential utility of treatments that interfere with drug-cue memory reconsolidation.

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.

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.