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1.
Life Sci ; 284: 119923, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34481865

RESUMO

AIMS: Levetiracetam (LEV) is a broad-spectrum antiepileptic drug with neuroprotective properties and novel mechanisms of action. Some evidence suggests that LEV may impact adult neurogenesis, but the results are controversial. The present study was aimed to evaluate the effects of LEV on the proliferation and differentiation of rat embryonic neural stem cells (NSCs) and to explore the role of GABAB or NMDA receptors. MAIN METHODS: NSCs were isolated from rat fetal ganglionic eminence at embryonic day 14.5. The effects of LEV on viability, proliferation, neurosphere formation, and neuronal or astroglial differentiation of NSCs were assessed using resazurin, BrdU incorporation, immunocytochemistry, quantitative real-time PCR, and western blotting. Additionally, we addressed the relationship between treatment with NMDA and GABAB receptor antagonists (MK801 and saclofen, respectively) in combination with LEV on these parameters. KEY FINDINGS: The data showed that LEV (50 µM) significantly increased the number (p < 0.01) and diameter of neurospheres (p < 0.05), enhanced proliferation (p < 0.01), and promoted neuronal differentiation, as revealed by significantly increased expressions of DCX and NeuN. The expressions of astroglial markers, GFAP and Olig2, were markedly reduced. The addition of MK801 (10 µM) significantly diminished neurospheres growth (p < 0.001), decreased the number of proliferating cells (p < 0.01), and reduced the number of new neurons (p < 0.001) but increased the astroglial cells (p < 0.001) induced by LEV. Co-treatment with saclofen (25 µM) did not significantly affect LEV-induced NSCs proliferation and differentiation. SIGNIFICANCE: Our findings suggest that LEV may enhance rat embryonic neurogenesis mainly through an NMDA receptor-mediated mechanism.


Assuntos
Embrião de Mamíferos/fisiologia , Levetiracetam/farmacologia , Neurogênese/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/metabolismo , Animais , Baclofeno/análogos & derivados , Baclofeno/farmacologia , Biomarcadores/metabolismo , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Maleato de Dizocilpina/farmacologia , Feminino , Masculino , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Células-Tronco Neurais/citologia , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/metabolismo , Neurônios/citologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos Wistar , Esferoides Celulares/citologia , Esferoides Celulares/efeitos dos fármacos
2.
Proc Natl Acad Sci U S A ; 118(39)2021 09 28.
Artigo em Inglês | MEDLINE | ID: mdl-34556581

RESUMO

d-amino acids are increasingly recognized as important signaling molecules in the mammalian central nervous system. However, the d-stereoisomer of the amino acid with the fastest spontaneous racemization ratein vitro in vitro, cysteine, has not been examined in mammals. Using chiral high-performance liquid chromatography and a stereospecific luciferase assay, we identify endogenous d-cysteine in the mammalian brain. We identify serine racemase (SR), which generates the N-methyl-d-aspartate (NMDA) glutamate receptor coagonist d-serine, as a candidate biosynthetic enzyme for d-cysteine. d-cysteine is enriched more than 20-fold in the embryonic mouse brain compared with the adult brain. d-cysteine reduces the proliferation of cultured mouse embryonic neural progenitor cells (NPCs) by ∼50%, effects not shared with d-serine or l-cysteine. The antiproliferative effect of d-cysteine is mediated by the transcription factors FoxO1 and FoxO3a. The selective influence of d-cysteine on NPC proliferation is reflected in overgrowth and aberrant lamination of the cerebral cortex in neonatal SR knockout mice. Finally, we perform an unbiased screen for d-cysteine-binding proteins in NPCs by immunoprecipitation with a d-cysteine-specific antibody followed by mass spectrometry. This approach identifies myristoylated alanine-rich C-kinase substrate (MARCKS) as a putative d-cysteine-binding protein. Together, these results establish endogenous mammalian d-cysteine and implicate it as a physiologic regulator of NPC homeostasis in the developing brain.


Assuntos
Encéfalo/fisiologia , Células-Tronco Neurais/fisiologia , Racemases e Epimerases/fisiologia , Serina/metabolismo , Animais , Animais Recém-Nascidos , Encéfalo/citologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células-Tronco Neurais/citologia , Receptores de N-Metil-D-Aspartato/metabolismo , Serina/química
3.
Zhongguo Zhong Yao Za Zhi ; 46(16): 4175-4186, 2021 Aug.
Artigo em Chinês | MEDLINE | ID: mdl-34467730

RESUMO

Excitatory toxicity(ET) is an important factor of neuropathic pain(NPP) induced by central sensitization(CS), and the association of pannexin-1(Panx1)-Src-N-methyl-D-aspartate receptor subunit 2 B(NMDAR-2 B) is an important new pathway for ET to initiate CS. The present study confirmed whether the central analgesic effect of Chuanxiong Rhizoma extract(CRE) was achieved through the synchronous regulation of the brain and spinal pathways of Panx1-Src-NMDAR-2 B. In this study, dynamic and simulta-neo-us microdialysis of the brain and spinal cord in vivo combined with behavioristics, high performance liquid chromatography(HPLC)-fluorescence detection, microdialysis analysis(ISCUS~(flex)), ultrasensitive multifactorial electrochemiluminescence immunoassay, ELISA, and Western blot was employed to investigate the protein expression of NMDAR-2 B, Src, and Panx1, extracellular excitatory amino acids, cytokines, energy metabolites, and substance P in spinal dorsal horn(SDH) and anterior cingulate cortex(ACC) after CRE intervention with the rat model of spared sciatic nerve injury(SNI) as the experimental tool. Compared with the sham group, the SNI group exhibited diminished mechanical withdrawal threshold(MWT)(P<0.01), increased cold spray scores(P<0.01), glutamate(Glu), D-serine(D-Ser), and glycine(Gly) in extracellular fluids of ACC, and Glu, D-Ser, interleukin-1ß(IL-1ß), and lactic acid(Lac) in extracellular fluids of SDH(P<0.05), dwindled tumor necrosis factor(TNF-α)(P<0.05), and elevated protein levels of NMDAR-2 B, Src, and Panx1 in ACC(P<0.05). Compared with the SNI model rats, high-and medium-dose CRE(CRE-H/M) could potentiate the analgesic activity as revealed by the MWT test(P<0.05) and CRE-M enabled the decrease in cold spray scores(P<0.05). CRE-H/M could inhibit the levels of Glu, D-Ser and Gly in the extracellular fluids of ACC(P<0.05), and the levels of Glu in the extracellular fluids of SDH(P<0.05) in SNI rats. CRE-M significantly increased the levels of glucose(Gluc), Lac, interferon-gamma(IFN-γ), keratinocyte chemoattractant/human growth-regulated oncogenes(KC/GRO), and IL-4 in extracellular fluids of SDH in SNI rats(P<0.05). CRE-H/M/L could also inhibit the levels of NMDAR-2 B, Src and Panx1 in ACC and SDH in SNI rats(P<0.05). The central analgesic effect of CRE is presumedly related to the inhibited release of excitatory amino acid transmitters(Glu, D-Ser and Gly) in ACC and SDH of SNI rats, decreased protein expression of NMDAR-2 B, Src and Panx1 in the two regions, and the regulation of the Panx1-Src-NMDAR-2 B pathway in the spinal cord and brain. The above findings partially clarified the scientific basis of clinical analgesic effect of Chuanxiong Rhizoma.


Assuntos
Neuralgia , Receptores de N-Metil-D-Aspartato , Animais , Sensibilização do Sistema Nervoso Central , Neuralgia/tratamento farmacológico , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Transdução de Sinais , Medula Espinal/metabolismo
4.
Neuron ; 109(17): 2727-2739.e3, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34380016

RESUMO

Utilizing recent advances in machine learning, we introduce a systematic approach to characterize neurons' input/output (I/O) mapping complexity. Deep neural networks (DNNs) were trained to faithfully replicate the I/O function of various biophysical models of cortical neurons at millisecond (spiking) resolution. A temporally convolutional DNN with five to eight layers was required to capture the I/O mapping of a realistic model of a layer 5 cortical pyramidal cell (L5PC). This DNN generalized well when presented with inputs widely outside the training distribution. When NMDA receptors were removed, a much simpler network (fully connected neural network with one hidden layer) was sufficient to fit the model. Analysis of the DNNs' weight matrices revealed that synaptic integration in dendritic branches could be conceptualized as pattern matching from a set of spatiotemporal templates. This study provides a unified characterization of the computational complexity of single neurons and suggests that cortical networks therefore have a unique architecture, potentially supporting their computational power.


Assuntos
Córtex Cerebral/fisiologia , Aprendizado Profundo , Modelos Neurológicos , Células Piramidais/fisiologia , Córtex Cerebral/citologia , Córtex Cerebral/metabolismo , Dendritos/metabolismo , Dendritos/fisiologia , Humanos , Células Piramidais/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo
5.
Int J Mol Sci ; 22(16)2021 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-34445137

RESUMO

Disrupted glutamate clearance in the synaptic cleft leads to synaptic dysfunction and neurological diseases. Decreased glutamate removal from the synaptic cleft is known to cause excitotoxicity. Data on the physiological effects of increased glutamate clearance are contradictory. This study investigated the consequences of ceftriaxone (CTX), an enhancer of glutamate transporter 1 expression, treatment on long-term synaptic potentiation (LTP) in the hippocampus of young rats. In this study, 5-day administration of CTX (200 mg/kg) significantly weakened LTP in CA3-CA1 synapses. As shown by electrophysiological recordings, LTP attenuation was associated with weakening of N-Methyl-D-aspartate receptor (NMDAR)-dependent signaling in synapses. However, PCR analysis did not show downregulation of NMDAR subunits or changes in the expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) subunits. We assume that extracellular burst stimulation activates fewer synapses in CTX-treated animals because increased glutamate reuptake results in reduced spillover, and neighboring synapses do not participate in neurotransmission. Attenuation of LTP was not accompanied by noticeable behavioral changes in the CTX group, with no behavioral abnormalities observed in the open field test or Morris water maze test. Thus, our experiments show that increased glutamate clearance can impair long-term synaptic plasticity and that this phenomenon can be considered a potential side effect of CTX treatment.


Assuntos
Ceftriaxona/farmacologia , Hipocampo/efeitos dos fármacos , Potenciação de Longa Duração/efeitos dos fármacos , Animais , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Ácido Glutâmico/metabolismo , Hipocampo/metabolismo , Masculino , Plasticidade Neuronal/efeitos dos fármacos , Ratos , Ratos Wistar , Receptores de AMPA/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Sinapses/efeitos dos fármacos , Sinapses/metabolismo , Transmissão Sináptica/efeitos dos fármacos , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico/metabolismo
6.
Int J Mol Sci ; 22(15)2021 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-34360983

RESUMO

Febrile seizures (FSs) in early life are significant risk factors of neurological disorders and cognitive impairment in later life. However, existing data about the impact of FSs on the developing brain are conflicting. We aimed to investigate morphological and functional changes in the hippocampus of young rats exposed to hyperthermia-induced seizures at postnatal day 10. We found that FSs led to a slight morphological disturbance. The cell numbers decreased by 10% in the CA1 and hilus but did not reduce in the CA3 or dentate gyrus areas. In contrast, functional impairments were robust. Long-term potentiation (LTP) in CA3-CA1 synapses was strongly reduced, which we attribute to the insufficient activity of N-methyl-D-aspartate receptors (NMDARs). Using whole-cell recordings, we found higher desensitization of NMDAR currents in the FS group. Since the desensitization of NMDARs depends on subunit composition, we analyzed NMDAR current decays and gene expression of subunits, which revealed no differences between control and FS rats. We suggest that an increased desensitization is due to insufficient activation of the glycine site of NMDARs, as the application of D-serine, the glycine site agonist, allows the restoration of LTP to a control value. Our results reveal a new molecular mechanism of FS impact on the developing brain.


Assuntos
Hipocampo/fisiopatologia , Potenciação de Longa Duração , Animais , Hipocampo/crescimento & desenvolvimento , Hipocampo/metabolismo , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/metabolismo , Convulsões Febris/metabolismo , Convulsões Febris/fisiopatologia , Potenciais Sinápticos
7.
ACS Chem Neurosci ; 12(18): 3335-3346, 2021 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-34449193

RESUMO

Selective inhibition of glycine transporter 1 (GlyT1) has emerged as a potential approach to alleviate N-methyl-d-aspartate receptor (NMDAR) hypofunction in patients with schizophrenia and cognitive decline. ALX5407 is a potent and selective inhibitor of GlyT1 derived from the metabolic intermediate sarcosine (N-methylglycine) that showed antipsychotic potential in a number of animal models. Whereas clinical application of ALX5407 is limited by adverse effects on motor performance and respiratory function, a suitably radiolabeled drug could represent a promising PET tracer for the visualization of GlyT1 in the brain. Herein, [18F]ALX5407 and the corresponding methyl ester, [18F]ALX5406, were prepared by alcohol-enhanced copper mediated radiofluorination and studied in vitro in rat brain slices and in vivo in normal rats. [18F]ALX5407 demonstrated accumulation consistent with the distribution of GlyT1 in in vitro autoradiographic studies but no brain uptake in µPET experiments in naïve rats. In contrast, the methyl ester [18F]ALX5406 rapidly entered the brain and was enzymatically transformed into [18F]ALX5407, resulting in a regional accumulation pattern consistent with GlyT1 specific binding. We conclude that [18F]ALX5406 is a promising and easily accessible PET probe for preclinical in vivo imaging of GlyT1 in the brain.


Assuntos
Proteínas da Membrana Plasmática de Transporte de Glicina , Pró-Fármacos , Animais , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Proteínas da Membrana Plasmática de Transporte de Glicina/metabolismo , Humanos , Tomografia por Emissão de Pósitrons , Ratos , Receptores de N-Metil-D-Aspartato/metabolismo , Sarcosina
8.
Eur J Neurosci ; 54(6): 6000-6011, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34405467

RESUMO

Proteasome activity at the excitatory synapse plays an important role in neuronal communication. The proteasome translocation to synapses is mediated by neuronal activity, in particular the activation of N-methyl-d-aspartate receptors (NMDARs). These receptors are composed of different subunits with distinct trafficking properties that provide various signalling and plasticity features to the synapse. Yet whether the interplay between the proteasome and NMDAR relies on specific subunit properties remain unclear. Using a combination of single molecule and immunocytochemistry imaging approaches in rat hippocampal neurons, we unveil a specific interplay between GluN2B-containing NMDARs (GluN2B-NMDARs) and the synaptic proteasome. Sustained proteasome activation specifically increases GluN2B-NMDAR (not GluN2A-NMDAR) lateral diffusion. In addition, when GluN2B-NMDAR expression is downregulated, the proteasome localization decreases at glutamatergic synapses. Collectively, our data fuel a model in which the cellular dynamics and location of GluN2B-NMDARs and proteasome are intermingled, shedding new lights on the NMDAR-dependent regulation of synaptic adaptation.


Assuntos
Complexo de Endopeptidases do Proteassoma , Receptores de N-Metil-D-Aspartato , Animais , Hipocampo/metabolismo , Ratos , Receptores de N-Metil-D-Aspartato/metabolismo , Transdução de Sinais , Sinapses/metabolismo
9.
Nat Commun ; 12(1): 5116, 2021 08 25.
Artigo em Inglês | MEDLINE | ID: mdl-34433814

RESUMO

NMDA receptor (NMDAR) and GABA neuronal dysfunctions are observed in animal models of autism spectrum disorders, but how these dysfunctions impair social cognition and behavior remains unclear. We report here that NMDARs in cortical parvalbumin (Pv)-positive interneurons cooperate with gap junctions to promote high-frequency (>80 Hz) Pv neuronal burst firing and social cognition. Shank2-/- mice, displaying improved sociability upon NMDAR activation, show impaired cortical social representation and inhibitory neuronal burst firing. Cortical Shank2-/- Pv neurons show decreased NMDAR activity, which suppresses the cooperation between NMDARs and gap junctions (GJs) for normal burst firing. Shank2-/- Pv neurons show compensatory increases in GJ activity that are not sufficient for social rescue. However, optogenetic boosting of Pv neuronal bursts, requiring GJs, rescues cortical social cognition in Shank2-/- mice, similar to the NMDAR-dependent social rescue. Therefore, NMDARs and gap junctions cooperate to promote cortical Pv neuronal bursts and social cognition.


Assuntos
Junções Comunicantes/metabolismo , Interneurônios/fisiologia , Proteínas do Tecido Nervoso/metabolismo , Cognição Social , Sinapses/fisiologia , Animais , Junções Comunicantes/genética , Masculino , Camundongos , Camundongos Knockout , Proteínas do Tecido Nervoso/genética , Parvalbuminas/genética , Parvalbuminas/metabolismo , Receptores de N-Metil-D-Aspartato/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Comportamento Social , Sinapses/genética
10.
Int J Mol Sci ; 22(15)2021 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-34360755

RESUMO

Increasing attention is being focused on the use of polypeptide-based N-methyl-d-aspartate (NMDA) receptor antagonists for the treatment of nervous system disorders. In our study on Achyranthes bidentata Blume, we identified an NMDA receptor subtype 2B (NR2B) antagonist that exerts distinct neuroprotective actions. This antagonist is a 33 amino acid peptide, named bidentatide, which contains three disulfide bridges that form a cysteine knot motif. We determined the neuroactive potential of bidentatide by evaluating its in vitro effects against NMDA-mediated excitotoxicity. The results showed that pretreating primary cultured hippocampal neurons with bidentatide prevented NMDA-induced cell death and apoptosis via multiple mechanisms that involved intracellular Ca2+ inhibition, NMDA current inhibition, and apoptosis-related protein expression regulation. These mechanisms were all dependent on bidentatide-induced inhibitory regulation of NR2B-containing NMDA receptors; thus, bidentatide may contribute to the development of neuroprotective agents that would likely possess the high selectivity and safety profiles inherent in peptide drugs.


Assuntos
Achyranthes/química , Hipocampo/metabolismo , Neurônios/metabolismo , Fármacos Neuroprotetores , Peptídeos , Proteínas de Plantas , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Animais , Apoptose/efeitos dos fármacos , Cálcio/metabolismo , Fármacos Neuroprotetores/química , Fármacos Neuroprotetores/isolamento & purificação , Fármacos Neuroprotetores/farmacologia , Peptídeos/química , Peptídeos/isolamento & purificação , Peptídeos/farmacologia , Proteínas de Plantas/química , Proteínas de Plantas/isolamento & purificação , Proteínas de Plantas/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/metabolismo
11.
Int J Mol Sci ; 22(15)2021 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-34360969

RESUMO

Physical exercise reduces the extent, duration, and frequency of drug use in drug addicts during the drug initiation phase, as well as during prolonged addiction, withdrawal, and recurrence. However, information about exercise-induced neurobiological changes is limited. This study aimed to investigate the effects of forced moderate endurance exercise training on methamphetamine (METH)-induced behavior and the associated neurobiological changes. Male Sprague Dawley rats were subjected to the administration of METH (1 mg/kg/day, i.p.) and/or forced moderate endurance exercise (treadmill running, 21 m/min, 60 min/day) for 2 weeks. Over the two weeks, endurance exercise training significantly reduced METH-induced hyperactivity. METH and/or exercise treatment increased striatal dopamine (DA) levels, decreased p(Thr308)-Akt expression, and increased p(Tyr216)-GSK-3ß expression. However, the phosphorylation levels of Ser9-GSK-3ß were significantly increased in the exercise group. METH administration significantly increased the expression of NMDAr1, CaMKK2, MAPKs, and PP1 in the striatum, and exercise treatment significantly decreased the expression of these molecules. Therefore, it is apparent that endurance exercise inhibited the METH-induced hyperactivity due to the decrease in GSK-3ß activation by the regulation of the striatal glutamate signaling pathway.


Assuntos
Ácido Glutâmico/metabolismo , Metanfetamina/toxicidade , Condicionamento Físico Animal/métodos , Agitação Psicomotora/terapia , Corrida , Animais , Corpo Estriado/metabolismo , Dopamina/metabolismo , Glicogênio Sintase Quinase 3 beta/metabolismo , Masculino , Proteínas Proto-Oncogênicas c-akt/metabolismo , Agitação Psicomotora/etiologia , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/metabolismo , Transdução de Sinais
12.
Transl Psychiatry ; 11(1): 444, 2021 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-34462417

RESUMO

A dysfunction of the glutamatergic transmission, especially of the NMDA receptor (NMDAR), constitutes one of the main biological substrate of psychotic disorders, such as schizophrenia. The NMDAR signaling hypofunction, through genetic and/or environmental insults, would cause a neurodevelopmental myriad of molecular, cellular, and network alterations that persist throughout life. Yet, the mechanisms underpinning NMDAR dysfunctions remain elusive. Here, we compared the membrane trafficking of NMDAR in three gold-standard models of schizophrenia, i.e., patient's cerebrospinal fluids, genetic manipulations of susceptibility genes, and prenatal developmental alterations. Using a combination of single nanoparticle tracking, electrophysiological, biochemical, and behavioral approaches in rodents, we identified that the NMDAR trafficking in hippocampal neurons was consistently altered in all these different models. Artificial manipulations of the NMDAR surface dynamics with competing ligands or antibody-induced receptor cross-link in the developing rat brain were sufficient to regulate the adult acoustic startle reflex and compensate for an early pathological challenge. Collectively, we show that the NMDAR trafficking is markedly altered in all clinically relevant models of psychosis, opening new avenues of therapeutical strategies.


Assuntos
Transtornos Psicóticos , Esquizofrenia , Animais , Hipocampo/metabolismo , Ratos , Receptores de N-Metil-D-Aspartato/metabolismo , Transdução de Sinais
13.
Int J Mol Sci ; 22(15)2021 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-34360854

RESUMO

Ketamine is a clinical anesthetic and antidepressant. Although ketamine is a known NMDA receptor antagonist, the mechanisms contributing to antidepression are unclear. This present study examined the loci and duration of ketamine's actions, and the involvement of NMDA receptors. Local field potentials were recorded from the CA1 region of mouse hippocampal slices. Ketamine was tested at antidepressant and anesthetic concentrations. Effects of NMDA receptor antagonists APV and MK-801, GABA receptor antagonist bicuculline, and a potassium channel blocker TEA were also studied. Ketamine decreased population spike amplitudes during application, but a long-lasting increase in amplitudes was seen during washout. Bicuculline reversed the acute effects of ketamine, but the washout increase was not altered. This long-term increase was statistically significant, sustained for >2 h, and involved postsynaptic mechanisms. A similar effect was produced by MK-801, but was only partially evident with APV, demonstrating the importance of the NMDA receptor ion channel block. TEA also produced a lasting excitability increase, indicating a possible involvement of potassium channel block. This is this first report of a long-lasting increase in excitability following ketamine exposure. These results support a growing literature that increased GABA inhibition contributes to ketamine anesthesia, while increased excitatory transmission contributes to its antidepressant effects.


Assuntos
Anestésicos/farmacologia , Antidepressivos/farmacologia , Hipocampo/efeitos dos fármacos , Ketamina/farmacologia , Neurônios/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Animais , Hipocampo/citologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Neurônios/citologia , Receptores de N-Metil-D-Aspartato/metabolismo
14.
Int J Mol Sci ; 22(15)2021 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-34360865

RESUMO

Traumatic brain injury (TBI) affects over 69 million people annually worldwide, and those with pre-existing depression have worse recovery. The molecular mechanisms that may contribute to poor recovery after TBI with co-morbid depression have not been established. TBI and depression have many commonalities including volume changes, myelin disruption, changes in proliferation, and changes in glutamatergic signaling. We used a well-established animal model of depression, the Wistar Kyoto (WKY) rat, to elucidate changes after TBI that may influence the recovery trajectory. We compared the histological and molecular outcomes in the hippocampal dentate gyrus after experimental TBI using the lateral fluid percussion injury (LFPI) in the WKY and the parent Wistar (WIS) strain. We showed that WKY had exaggerated myelin loss after LFPI and baseline deficits in proliferation. In addition, we showed that while after LFPI WIS rats exhibited glutamate receptor subunit changes, namely increased GluN2B, the WKY rats failed to show such injury-related changes. These differential responses to LFPI helped to elucidate the molecular characteristics that influence poor recovery after TBI in those with pre-existing depression and may lead to targets for future therapeutic interventions.


Assuntos
Lesões Encefálicas Traumáticas/metabolismo , Hipocampo , Receptores de N-Metil-D-Aspartato/metabolismo , Animais , Proliferação de Células , Transtorno Depressivo Maior/metabolismo , Hipocampo/patologia , Ratos , Ratos Endogâmicos WKY , Ratos Wistar
15.
Biomed Res Int ; 2021: 1156031, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34423030

RESUMO

Here, we report the participation of N-methyl-D-aspartate (NMDA) glutamate receptor in the mediation of cardiovascular and circulating vasopressin responses evoked by a hemorrhagic stimulus. In addition, once NMDA receptor activation is a prominent mechanism involved in nitric oxide (NO) synthesis in the brain, we investigated whether control of hemorrhagic shock by NMDA glutamate receptor was followed by changes in NO synthesis in brain supramedullary structures involved in cardiovascular and neuroendocrine control. Thus, we observed that intraperitoneal administration of the selective NMDA glutamate receptor antagonist dizocilpine maleate (MK801, 0.3 mg/kg) delayed and reduced the magnitude of hemorrhage-induced hypotension. Besides, hemorrhage induced a tachycardia response in the posthemorrhage period (i.e., recovery period) in control animals, and systemic treatment with MK801 caused a bradycardia response during hemorrhagic shock. Hemorrhagic stimulus increased plasma vasopressin levels during the recovery period and NMDA receptor antagonism increased concentration of this hormone during both the hemorrhage and postbleeding periods in relation to control animals. Moreover, hemorrhagic shock caused a decrease in NOx levels in the paraventricular nucleus of the hypothalamus (PVN), amygdala, bed nucleus of the stria terminalis (BNST), and ventral periaqueductal gray matter (vPAG). Nevertheless, treatment with MK801 did not affect these effects. Taken together, these results indicate that the NMDA glutamate receptor is involved in the hemorrhagic shock by inhibiting circulating vasopressin release. Our data also suggest a role of the NMDA receptor in tachycardia, but not in the decreased NO synthesis in the brain evoked by hemorrhage.


Assuntos
Bradicardia/induzido quimicamente , Sistema Cardiovascular/metabolismo , Maleato de Dizocilpina/administração & dosagem , Choque Hemorrágico/metabolismo , Vasopressinas/sangue , Animais , Bradicardia/sangue , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Sistema Cardiovascular/efeitos dos fármacos , Modelos Animais de Doenças , Maleato de Dizocilpina/efeitos adversos , Injeções Intraperitoneais , Masculino , Sistemas Neurossecretores/efeitos dos fármacos , Sistemas Neurossecretores/metabolismo , Óxido Nítrico/metabolismo , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/metabolismo
16.
Am J Physiol Heart Circ Physiol ; 321(3): H580-H591, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34355986

RESUMO

Tumor necrosis factor-α (TNFα) in the hypothalamic paraventricular nucleus (PVN) contributes to increased sympathetic nerve activity (SNA) in cardiovascular disease models, but mechanisms are incompletely understood. As previously reported, bilateral PVN TNFα (0.6 pmol, 50 nL) induced acute ramping of splanchnic SNA (SSNA) that averaged +64 ± 7% after 60 min and +109 ± 17% after 120 min (P < 0.0001, n = 10). Given that TNFα can rapidly strengthen glutamatergic transmission, we hypothesized that progressive activation of ionotropic glutamate receptors is critically involved. When compared with that of vehicle (n = 5), prior blockade of PVN AMPA or NMDA receptors in anesthetized (urethane/α-chloralose) adult male Sprague-Dawley rats dose-dependently (ED50: 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX), 2.48 nmol; D-(-)-2-amino-5-phosphonopentanoic acid (APV), 12.33 nmol), but incompletely (Emax: NBQX, 64%; APV, 41%), attenuated TNFα-induced SSNA ramping (n = 5/dose). By contrast, combined receptor blockade prevented ramping (1.3 ± 2.1%, P < 0.0001, n = 5). Whereas separate blockade of PVN AMPA or NMDA receptors (n = 5/group) had little effect on continued SSNA ramping when performed 60 min after TNFα injection, combined blockade (n = 5) or PVN inhibition with the GABA-A receptor agonist muscimol (n = 5) effectively stalled, without reversing, the SSNA ramp. Notably, PVN TNFα increased local TNFα immunofluorescence after 120, but not 60 min. Findings indicate that AMPA and NMDA receptors each contribute to SSNA ramping to PVN TNFα, and that their collective availability and ongoing activity are required to initiate and sustain the ramping response. We conclude that acute sympathetic activation by PVN TNFα involves progressive local glutamatergic excitation that recruits downstream neurons capable of maintaining heightened SSNA, but incapable of sustaining SSNA ramping.NEW & NOTEWORTHY The proinflammatory cytokine TNFα contributes to heightened SNA in cardiovascular disease models, but mechanisms remain obscure. Here, we demonstrate that TNFα injection into the hypothalamic PVN triggers SNA ramping by mechanisms dependent on local ionotropic glutamate receptor availability, but largely independent of TNFα autoinduction. Continued SNA ramping depends on ionotropic glutamate receptor and neuronal activity in PVN, indicating that strengthening and/or increased efficacy of glutamatergic transmission is necessary for acute sympathoexcitation by PVN TNFα.


Assuntos
Núcleo Hipotalâmico Paraventricular/metabolismo , Receptores de AMPA/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Nervos Esplâncnicos/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Antagonistas de Aminoácidos Excitatórios/farmacologia , Agonistas de Receptores de GABA-A/farmacologia , Masculino , Muscimol/farmacologia , Núcleo Hipotalâmico Paraventricular/fisiologia , Quinoxalinas/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de GABA-A/metabolismo , Nervos Esplâncnicos/efeitos dos fármacos , Nervos Esplâncnicos/fisiologia
17.
Biomolecules ; 11(7)2021 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-34356650

RESUMO

Evidence from clinical and preclinical studies implicates dysfunction of N-methyl-D-aspartate receptors (NMDARs) in schizophrenia progression and symptoms. We investigated the antipsychotic effect of two neuroactive steroids in an animal model of schizophrenia induced by systemic application of MK-801. The neuroactive steroids differ in their mechanism of action at NMDARs. MS-249 is positive, while PA-Glu is a negative allosteric NMDAR modulator. We hypothesized that the positive NMDA receptor modulator would attenuate deficits caused by MK-801 co-application more effectively than PA-Glu. The rats were tested in a battery of tests assessing spontaneous locomotion, anxiety and cognition. Contrary to our expectations, PA-Glu exhibited a superior antipsychotic effect to MS-249. The performance of MS-249-treated rats in cognitive tests differed depending on the level of stress the rats were exposed to during test sessions. In particular, with the increasing severity of stress exposure, the performance of animals worsened. Our results demonstrate that enhancement of NMDAR function may result in unspecific behavioral responses. Positive NMDAR modulation can influence other neurobiological processes besides memory formation, such as anxiety and response to stress.


Assuntos
Maleato de Dizocilpina/farmacologia , Receptores de N-Metil-D-Aspartato/metabolismo , Esquizofrenia/tratamento farmacológico , Esteroides/farmacologia , Animais , Antipsicóticos/farmacologia , Comportamento Animal/efeitos dos fármacos , Compostos Bicíclicos Heterocíclicos com Pontes/metabolismo , Modelos Animais de Doenças , Teste de Labirinto em Cruz Elevado , Células HEK293 , Humanos , Masculino , Pregnenolona/metabolismo , Pregnenolona/farmacologia , Ratos Long-Evans , Ratos Wistar , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Reflexo de Sobressalto/efeitos dos fármacos , Esquizofrenia/metabolismo
18.
Nat Commun ; 12(1): 4709, 2021 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-34354080

RESUMO

Allostery represents a fundamental mechanism of biological regulation that involves long-range communication between distant protein sites. It also provides a powerful framework for novel therapeutics. NMDA receptors (NMDARs), glutamate-gated ionotropic receptors that play central roles in synapse maturation and plasticity, are prototypical allosteric machines harboring large extracellular N-terminal domains (NTDs) that provide allosteric control of key receptor properties with impact on cognition and behavior. It is commonly thought that GluN2A and GluN2B receptors, the two predominant NMDAR subtypes in the adult brain, share similar allosteric transitions. Here, combining functional and structural interrogation, we reveal that GluN2A and GluN2B receptors utilize different long-distance allosteric mechanisms involving distinct subunit-subunit interfaces and molecular rearrangements. NMDARs have thus evolved multiple levels of subunit-specific allosteric control over their transmembrane ion channel pore. Our results uncover an unsuspected diversity in NMDAR molecular mechanisms with important implications for receptor physiology and precision drug development.


Assuntos
Receptores de N-Metil-D-Aspartato/metabolismo , Regulação Alostérica , Animais , Feminino , Células HEK293 , Humanos , Técnicas In Vitro , Camundongos , Modelos Moleculares , Mutagênese Sítio-Dirigida , Oócitos/metabolismo , Fotoquímica , Conformação Proteica , Domínios e Motivos de Interação entre Proteínas , Multimerização Proteica , Subunidades Proteicas , Ratos , Receptores de N-Metil-D-Aspartato/química , Receptores de N-Metil-D-Aspartato/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Xenopus laevis
19.
Int J Mol Sci ; 22(16)2021 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-34445376

RESUMO

Synaptic plasticity is the key to synaptic health, and aberrant synaptic plasticity, which in turn impairs the functioning of large-scale brain networks, has been associated with neurodegenerative and psychiatric disorders. The best known and most studied form of activity-dependent synaptic plasticity remains long-term potentiation (LTP), which is controlled by glutamatergic N-methyl-d-aspartate) receptors (NMDAR) and considered to be a mechanism crucial for cellular learning and memory. Over the past two decades, discrepancies have arisen in the literature regarding the contribution of NMDAR subunit assemblies in the direction of NMDAR-dependent synaptic plasticity. Here, the nonspecific NMDAR antagonist ketamine (5 and 10 mg/kg), and the selective NR2B antagonists CP-101606 and Ro 25-6981 (6 and 10 mg/kg), were administered intraperitoneally in Sprague Dawley rats to disentangle the contribution of NR2B subunit in the LTP induced at the Schaffer Collateral-CA1 synapse using the theta burst stimulation protocol (TBS). Ketamine reduced, while CP-101606 and Ro 25-6981 did not alter the LTP response. The administration of CP-101606 before TBS did not influence the effects of ketamine when administered half an hour after tetanization, suggesting a limited contribution of the NR2B subunit in the action of ketamine. This work confirms the role of NMDAR in the LTP form of synaptic plasticity, whereas specific blockade of the NR2B subunit was not sufficient to modify hippocampal LTP. Pharmacokinetics at the doses used may have contributed to the lack of effects with specific antagonists. The findings refute the role of the NR2B subunit in the plasticity mechanism of ketamine in the model.


Assuntos
Ketamina/administração & dosagem , Fenóis/administração & dosagem , Piperidinas/administração & dosagem , Receptores de N-Metil-D-Aspartato/metabolismo , Sinapses/metabolismo , Animais , Injeções Intraperitoneais , Ketamina/farmacologia , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Plasticidade Neuronal/efeitos dos fármacos , Fenóis/farmacologia , Piperidinas/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores
20.
Neuroscience ; 473: 142-158, 2021 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-34298123

RESUMO

Exposure to intense or repeated stressors can lead to depression or post-traumatic stress disorder (PTSD). Neurological changes induced by stress include impaired neurotrophin signaling, which is known to influence synaptic integrity and plasticity. The present study used an ex vivo approach to examine the impact of acute or repeated stress on BDNF-stimulated TrkB signaling in hippocampus (HIPPO) and prefrontal cortex (PFC). Rats in an acute multiple stressor group experienced five stressors in one day whereas rats in a repeated unpredictable stressor group experienced 20 stressors across 10 days. After stress exposure, slices were incubated with vehicle or BDNF, followed by immunoprecipitation and immunoblot assays to assess protein levels, activation states and protein-protein linkage associated with BDNF-TrkB signaling. Three key findings are (1) exposure to stressors significantly diminished BDNF-stimulated TrkB signaling in HIPPO and PFC such that reductions in TrkB activation, diminished recruitment of adaptor proteins to TrkB, reduced activation of downstream signaling molecules, disruption of TrkB-NMDAr linkage, and changes in basal and BDNF-stimulated Arc expression were observed. (2) After stress, BDNF stimulation enhanced TrkB-NMDAr linkage in PFC, suggestive of compensatory mechanisms in this region. (3) We discovered an uncoupling between TrkB signaling, TrkB-NMDAr linkage and Arc expression in PFC and HIPPO. In addition, a robust surge in pro-inflammatory cytokines was observed in both regions after repeated exposure to stressors. Collectively, these data provide therapeutic targets for future studies that investigate how to reverse stress-induced downregulation of BDNF-TrkB signaling and underscore the need for functional studies that examine stress-related TrkB-NMDAr activities in PFC.


Assuntos
Fator Neurotrófico Derivado do Encéfalo , Receptores de N-Metil-D-Aspartato , Animais , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Hipocampo/metabolismo , Neurônios/metabolismo , Ratos , Receptor trkB/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Transdução de Sinais
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