Os autores gostaria de agradecer o Post Bacharelado Scholars Program Office e Novartis institutos para investigação biomédica como um todo para o financiamento deste estudo.

1. preparação das células
Nota: Este protocolo, incluindo a geração de dados, usa HEK293 células transfectadas com um baculovirus codificação NR1 e NR2A células.
<ol><li>O número adequado de células HEK293 de sementes e adicionar o vírus NR1 e/ou NR2A nas concentrações finais apropriadas (1,00 µ l cada). Para uma placa de 384, use 10.000 células/poço em um volume final de 30 µ l.</li>
	<li>Alternativamente, as sementes células HEK293-NR1-NR2A o número de célula apropriada e volume (por um prato de 384-bem, uso 10.000 células/poço em um volume final de 30 µ l). Adicionar tetraciclina na concentração de 2 µ g/mL para induzir a expressão NR2A e adicionar a proteção composta (100 µM MDL105, 519 ou 5 µM CGP07066724).</li>
	<li>Nota: O baculovirus codificação NR1 e NR2 devem ter um título aproximado entre 5 x 109 - 10 x 109 unidade infecciosa por mililitro24.</li>
</ol>2. medida da atividade do receptor NMDA
<ol><li>Prepare uma placa de 384 com células HEK293 transfectadas com células NR1/NR2 ou HEK293-NR1-NR2A na presença de compostos de qualquer proteção. Use um fundo transparente, moldura preta, placa revestida de poli-D-lisina. Nota: Proteção com 100 µM MDL105, 519 é usado para conferir a sensibilidade a glicina, enquanto 5 µM CGP070667 é usado para conferir a sensibilidade ao glutamato.</li>
	<li>Incube a placa a 37 ° C e 5% de CO2 por 16 horas (durante a noite).</li>
	<li>Retirar a placa da incubadora e suavemente, descartar a mídia celular por abrandar capotar um recipiente de resíduos biológicos compatível com a placa. Bata levemente a placa sobre uma toalha de papel para limpar a mídia fora as bordas da placa e todos os restantes meios de drenagem.</li>
	<li>Prepare o corante calcium6 por solubilizing, um frasco de tintura de calcium6 (1 tamanho da placa) em 10 mL de tampão de incubação (HBSS pH 7,5, 20 mM HEPES, 1 mM MgCl2, probenecida 1 mM). Incube a placa por 2 horas a 37 ° C e 5% de CO2.</li>
	<li>Retirar a placa da incubadora e deixar que as células ajustar a temperatura ambiente por 10 minutos.</li>
	<li>Despeje delicadamente o corante calcium6, conforme descrito na etapa 2.3 e adicione 30 µ l de tampão do ensaio (HBSS pH 7,5, 20 mM HEPES, 1.8 mM CaCl2, probenecida 1 mM).</li>
	<li>Repita a etapa 2.6 duas vezes para um total de 3 lavagens. Deixe 30 µ l de buffer de ensaio sobre as células após a última lavagem.</li>
	<li>Deixe que as células descansar por 5 minutos à temperatura ambiente.</li>
	<li>Prepare a placa de ligante, fazendo um 4-fold estoque de 400 µM de glicina e o glutamato 400 µM (concentração final de 100 µM; concentração ideal de ligantes para ser determinada conforme descrito abaixo). Transferi um mínimo de 25 µ l de estoque de ligante para uma placa de 384 V-fundo.</li>
	<li>Carrega o ligante e chapa de célula para o FDSS (sistema de rastreio de drogas funcional).</li>
	<li>Medir a fluorescência de base (Fó) da placa de celular por 30 segundos. Transferi 10 µ l do estoque de ligante para a placa de células usando a função aplicadora FDSS e medida do fluxo de cálcio por fluorescência calcium6-corante para 5 minutos de gravação.</li>
	<li>Calcule a relação de fluorescência máxima dividindo a fluorescência máxima obtida por fluorescência de base (F/f demáximoó).</li>
</ol>3. otimização de níveis de expressão de NMDAR
<ol><li>Para determinar a quantidade ideal de baculovirus para utilizar, execute uma titulação do vírus tanto NR1 e NR2A. Preparar uma placa de 384 com células HEK293 (recomendação de 10.000 células/poço, 30 µ l de mídia) e incluem os compostos de proteção conforme descrito no passo 2.1.</li>
	<li>Adicionar diferentes quantidades do vírus NR1 em linhas diferentes da placa (por exemplo: Adicionar µ l 0, 2 µ l, 1 µ l, 0,5 µ l, 0,25 µ l em linhas A-E, respectivamente). Adicione duplicatas para a precisão dos dados.</li>
	<li>Adicionar diferentes quantidades do vírus NR2A em diferentes colunas da placa (por exemplo: Adicionar µ l 0, 2 µ l, 1 µ l, 0,5 µ l, 0,25 µ l em linhas A-E, respectivamente). Adicione duplicatas para a precisão dos dados.</li>
	<li>Incube a placa a 37 ° C e 5% de CO2 por 16 horas (durante a noite).</li>
	<li>Determine a melhor relação qualidade e quantidade dos vírus NR1 e NR2A realizando uma medição de fluxo de cálcio sobre o FDSS (veja acima).</li>
</ol>4. ligante titulação
<ol><li>Prepare as células conforme descrito na etapa 2.3.</li>
	<li>Prepare diluições de cada ligante na presença de concentrações (100 µM) para impregnação do outro ligante como 4-fold solução estoque. Por exemplo: para uma concentração de 10 µM teste final de glicina, prepare uma solução stock de 40 µM de glicina, incluindo 400 µM glutamato.</li>
	<li>Prosseguir com a medição de FDSS conforme descrito na etapa 2.11.</li>
</ol>5. compostos de teste
<ol><li>Prepare as células conforme descrito na etapa 1.</li>
	<li>Prepare a placa de ligante com um 5-fold estoque de concentração final de ligante no buffer de ensaio.</li>
	<li>Prepare a placa de compostos com o 4-fold estoque de concentração final desejada de compostos no buffer de ensaio. Para uma concentração final de composto de 10 µM no buffer de ensaio, prepare uma solução stock de 40 µM.<ol>
<li>Manter a concentração do dimetilsulfóxido (DMSO) constante em todas as amostras através da elaboração de uma pré-diluição do composto em DMSO antes mais diluição para o buffer de ensaio.</li>
		<li>Para uma resposta de dose do composto no ensaio final variando entre 3 e 30 µM, prepare uma diluição prévia do composto em DMSO, variando de 1 a 10 mM. Dilua os no buffer de ensaio para a concentração das ações 4-fold. A concentração final do DMSO não deve exceder 0,5%. Nota: É recomendável testar cada amostra em triplica.</li>
	</ol>
</li>
	<li>Carrega o ligante, composto e placa de células no FDSS.</li>
	<li>Medir a fluorescência de base por 30 segundos.</li>
	<li>Adicionar 10 µ l de estoque composto e medir a fluorescência por 5 minutos.</li>
	<li>Adicionar 10 µ l de estoque de ligante e medir a fluorescência por 5 minutos.</li>
	<li>Determine a integral da relação de fluorescência, calculando a área sob a curva dos rácios fluorescentes durante os últimos 5 minutos da medição. Nota: Como alternativa, a proporção máxima de fluorescência após adição de ligante pode ser usada para análise.</li>
</ol>

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Os autores têm sem conflitos de interesses e nada de divulgar.

O sucesso deste teste depende em grande parte a saúde das células HEK usado. Células em fase de crescimento exponencial e com número baixo de passagem deve ser usado. Este ensaio envolve muitas transferências e adições de soluções, usando então cuidado irão garantir maior precisão em seus resultados. Concentrações de compostos e todos os outros reagentes devem ser também cruzados para minimizar erros. Quando substituir a mídia celular com o buffer de ensaio para o ensaio de fluxo de cálcio, a placa deve ...

Com os atuais avanços na medicina, a expectativa de vida aumentou significativamente; no entanto, então tem a prevalência de doenças relacionadas com a idade. Doenças do sistema nervoso central (CNS) tais como esquizofrenia, esclerose lateral amiotrófica (ela), doença de Alzheimer e doença de Parkinson, entre outros, não são excepção e tem sido projetadas para aumentar ao longo da próxima década1, 2 , 3. o mau funcionamento dos receptores de glutamato de geleificação conhecido como receptores N-metil-D-aspartato (NMDAR) tem sido associado a doença de Alzheimer, esquizofrenia, traumatismo crânio-encefálico, acidente vascular cerebral, diabetes e glaucoma, entre outros, que garante a precisa estudar sua biologia para o desenvolvimento de terapias eficazes, doença-modificando4,5,6,7.
Os NMDARs são compostos de quatro monômeros ou subunidades4,8,9. A composição estrutural do NMDAR mostra variabilidade regional e de desenvolvimento dentro do cérebro7,10. Os NMDARs estão envolvidos na plasticidade sináptica, cognição e a geração de ritmos para respiração e locomoção11,12,13. Como um canal de voltagem-dependente, é em grande parte não-condutor no potencial de membrana de repouso (-70 mV) e é bloqueado por magnésio para prevenir mais permeação de íons. O canal é activado pela ligação de dois ligantes, glutamato e a glicina/D-serina, e uma despolarização simultânea na membrana sináptica mediada por receptores de GABA, outra subclasse de receptores de glutamato de geleificação. A despolarização remove o bloqueio de magnésio de NMDAR, permitindo o influxo de cátions, particularmente cálcio14,15,16. Mesmo que a ativação do NMDAR é essencial para a sobrevivência da pilha, ativação excessiva pode levar à morte17,18,19 através da excitotoxicidade da pilha. Isso, além da natureza complexa do receptor, torna desafiador para realizar estudos necessários para o desenvolvimento de terapias eficazes.
Diferentes métodos têm sido desenvolvidos para estudar o NMDAR. No entanto, cada um tem que acompanha ressalvas. Por exemplo, uma técnica amplamente utilizada é um ensaio baseado em fluorescência que mede mudanças NMDAR-mediada em cálcio intracelular em uma linha de celular estável sob o controle de um promotor inducible-tetraciclina (Tet-On)20. No entanto, neste sistema, as concentrações de supramaximal de ligantes que são necessários e a exigência de que os inibidores NMDAR estão presentes durante a medição torna quase impossível de detectar atividade da antagonista competitivo. Em outros sistemas similares, a expressão do receptor funcional provoca toxicidade, exigir que os bloqueadores de canais como a cetamina21,22 para preservar as culturas de células. Estes bloqueadores dos canais de sentar-se no núcleo do receptor e são difíceis de lavar, especialmente em um formato baseado em placa, para que eles interfiram com estudos funcionais do receptor. Finalmente, em medidas eletrofisiológicas tais como remendo aperto, há produção limitada, e estudos em grande escala são muito caro23. Não obstante, os sistemas acima são insensíveis à estimulação de glicina; Portanto, estudando a atividade de glicina-dependente do NMDAR torna-se um desafio.
Aqui, descrevemos uma nova abordagem para o estudo NMDAR que supera as limitações discutidas. Nossa técnica capitaliza sobre o sistema de expressão de baculovirus para expressar o receptor em níveis funcionais, com uma óptima relação das subunidades em menos de 16 horas. Além disso, o uso de baculovirus permite uma abordagem simples e combinatória, que fornece uma ampla caracterização dos subtipos distintos de NMDAR recombinantes. Ao contrário de outros ensaios, este protocolo não requer bloqueadores de canal por causa do uso de antagonistas fracos. Mais forte vantagem do método é aquele fracassado depois do antagonista fraco, o receptor é sensível a modulação dos sites individual glicina e o glutamato vinculação - além de modulação dual de glicina/D-serina e glutamato ligand-ligação sites. O ensaio recapitula a farmacologia conhecida do receptor NMDAR e os efeitos de seus conhecidos moduladores positivos e negativos. Finalmente, a geração deste ensaio celular em vitro supera a toxicidade celular causada pelo influxo excessivo de cálcio e permite estudos funcionais do receptor em uma moda de alta produtividade, que pode acelerar as descobertas de moduladores NMDAR Estados de doença.

<table><tbody><tr><td>HEK-293</td><td>ATCC</td><td>CRL-1573</td><td></td></tr><tr><td>Human NMDA (NR1/NR2A) Receptor Cell Line</td><td>ChanTest Corporation</td><td>CT6120</td><td></td></tr><tr><td>pFastBac Dual Expression Vector</td><td>ThermoFisher Scientific</td><td>10712-024</td><td></td></tr><tr><td>Corning 384-well Clear Flat Bottom Microplate</td><td>Corning Life Sciences</td><td>3844</td><td></td></tr><tr><td>FLIPR Calcium 6-QF Assay Kit</td><td>Molecular Devices</td><td>R8192</td><td></td></tr><tr><td>Glycine</td><td>Sigma-Aldrich</td><td>G7126</td><td></td></tr><tr><td>Glutamate</td><td>Sigma-Aldrich</td><td>49621</td><td></td></tr><tr><td>D-serine</td><td>Sigma-Aldrich</td><td>S4250</td><td></td></tr><tr><td>L701,324</td><td>Tocris</td><td>907</td><td></td></tr><tr><td>HEPES Buffer</td><td>Boston Bio Product</td><td>BB-103</td><td></td></tr><tr><td>Magnesium Chloride Solution</td><td>Sigma-Aldrich</td><td>63069</td><td></td></tr><tr><td>Calcium Chloride</td><td>VWR</td><td>E506</td><td></td></tr><tr><td>HBSS</td><td>ThermoFisher Scientific</td><td>14025-092</td><td></td></tr><tr><td>Probenecid</td><td>ThermoFisher Scientific</td><td>P36400</td><td></td></tr><tr><td>DMEM/F-12, GlutaMAX media</td><td>ThermoFisher Scientific</td><td>10565018</td><td></td></tr><tr><td>MDL105,519</td><td>NIBR</td><td>Synthesized in house</td><td></td></tr><tr><td>NVP-AAM077</td><td>NIBR</td><td>Synthesized in house</td><td></td></tr><tr><td>CGP070667</td><td>NIBR</td><td>Synthesized in house</td><td></td></tr></tbody></table>

a high-throughput calcium-flux assay to study nmda-receptors with sensitivity to glycine/d-serine and glutamate

Receptores de N-metil-D-aspartato (NMDA) (NMDAR) são classificados como receptores de glutamato de geleificação e têm papel crítico na aprendizagem e memória. Mau funcionamento do NMDAR, expressado como qualquer over - ou under - activity causada por mutações, expressão alterada, tráfico ou localização, pode contribuir para inúmeras doenças, especialmente no sistema nervoso central. Portanto, compreender a biologia do receptor, bem como facilitar a descoberta de compostos e moléculas pequenas é crucial nos esforços em curso para combater doenças neurológicas. As abordagens atuais para estudar o receptor têm limitações, incluindo a incapacidade para estudar suas habilidades funcionais devido a necessária presença de bloqueadores de canais para evitar excitotoxicidade mediada por NMDAR, alto custo e baixa taxa de transferência. Além disso, os sistemas existentes de ensaio são sensíveis à estimulação por glutamato apenas e faltam de sensibilidade à estimulação por glicina, o outro ligante co do NMDAR. Aqui, apresentamos o primeiro ensaio baseado em placa de poder elevado-throughput para estudar um receptor NMDA com sensibilidade para ambos os ligantes co, glutamato e D-serina/glicina. Esta abordagem permite o estudo de diferentes composições de subunidade NMDAR e permite estudos funcionais do receptor em modos de glicina e / ou sensíveis ao glutamato. Além disso, o método não requer a presença de inibidores durante as medições. Os efeitos de moduladores alostéricos positivos e negativos podem ser detectados com este ensaio e a farmacologia conhecida de NMDAR foi replicada em nosso sistema. Esta técnica supera as limitações dos métodos existentes e é rentável. Acreditamos que esta nova técnica irá acelerar a descoberta de terapias para patologias NMDAR-mediada.

Antes de testar os efeitos de pequenas moléculas, deve-se determinar os níveis de expressão ideal dos NMDARs, bem como as concentrações de ligante óptima. Conforme descrito, HEK293 células foram semeadas em 10.000 células por poço em uma placa de 384, na presença de 5 µM, CGP060667, então transfectadas com quantidades variadas de NR1 e NR2A vírus. Depois de cálcio durante a noite, induzida pelo ligante de incubação foi medido o fluxo (Figura 1...

Watch this Scientific Journal Video about A High-throughput Calcium-flux Assay to Study NMDA-receptors with Sensitivity to Glycine/D-serine and Glutamate at JoVE.com

A High-throughput Calcium-flux Assay to Study NMDA-receptors with Sensitivity to Glycine/D-serine and Glutamate

Um ensaio de cálcio de alta produtividade-flux para estudar os receptores NMDA com sensibilidade de glicina/D-serina e glutamato

O objetivo do presente protocolo é facilitar o estudo dos receptores de NMDA (NMDAR) em uma escala maior e permitir a análise dos efeitos moduladora de pequenas moléculas e suas aplicações terapêuticas.

N-methyl-D-aspartate (NMDA) receptors (NMDAR) are classified as ionotropic glutamate receptors and have critical roles in learning and memory. NMDAR ...

a-high-throughput-calcium-flux-assay-to-study-nmda-receptors-with

Universidad de Cartagena UDEC

Research

JoVE Journal

Neuroscience

9.2K visualizações.  Novartis Institutes for BioMedical Research. O objetivo do presente protocolo é facilitar o estudo dos receptores de NMDA (NMDAR) em uma escala maior e permitir a análise dos efeitos moduladora de pequenas moléculas e suas aplicações terapêuticas.

Vídeo: A High-throughput Calcium-flux Assay to Study NMDA-receptors with Sensitivity to Glycine/D-serine and Glutamate

Deriving the Time Course of Glutamate Clearance with a Deconvolution Analysis of Astrocytic Transporter Currents

The highest density of glutamate transporters in the brain is found in astrocytes. Glutamate transporters couple the movement of glutamate across the membrane with the co-transport of 3 Na+ and 1 H+ and the counter-transport of 1 K+. The stoichiometric current generated by the transport process can be monitored with whole-cell patch-clamp recordings from astrocytes. The time course of the recorded current is shaped by the time course of the glutamate concentration profile to which astrocytes are exposed, the kinetics of glutamate transporters, and the passive electrotonic properties of astrocytic membranes. Here we describe the experimental and analytical methods that can be used to record glutamate transporter currents in astrocytes and isolate the time course of glutamate clearance from all other factors that shape the waveform of astrocytic transporter currents. The methods described here can be used to estimate the lifetime of flash-uncaged and synaptically-released glutamate at astrocytic membranes in any region of the central nervous system during health and disease.

We describe an analytical method to estimate the lifetime of glutamate at astrocytic membranes from electrophysiological recordings of glutamate transporter currents in astrocytes.

Derivando o Curso momento do desembaraço glutamato com uma Análise de Deconvolução das correntes Transporter astrocitárias

The highest density of glutamate transporters in the brain is found in astrocytes. Glutamate transporters couple the movement of glutamate across the ...

Neurociência

Multi-photon Intracellular Sodium Imaging Combined with UV-mediated Focal Uncaging of Glutamate in CA1 Pyramidal Neurons

Multi-photon fluorescence microscopy has enabled the analysis of morphological and physiological parameters of brain cells in the intact tissue with high spatial and temporal resolution. Combined with electrophysiology, it is widely used to study activity-related calcium signals in small subcellular compartments such as dendrites and dendritic spines. In addition to calcium transients, synaptic activity also induces postsynaptic sodium signals, the properties of which are only marginally understood. Here, we describe a method for combined whole-cell patch-clamp and multi-photon sodium imaging in cellular micro domains of central neurons. Furthermore, we introduce a modified procedure for ultra-violet (UV)-light-induced uncaging of glutamate, which allows reliable and focal activation of glutamate receptors in the tissue. To this end, whole-cell recordings were performed on Cornu Ammonis subdivision 1 (CA1) pyramidal neurons in acute tissue slices of the mouse hippocampus. Neurons were filled with the sodium-sensitive fluorescent dye SBFI through the patch-pipette, and multi-photon excitation of SBFI enabled the visualization of dendrites and adjacent spines. To establish UV-induced focal uncaging, several parameters including light intensity, volume affected by the UV uncaging beam, positioning of the beam as well as concentration of the caged compound were tested and optimized. Our results show that local perfusion with caged glutamate (MNI-Glutamate) and its focal UV-uncaging result in inward currents and sodium transients in dendrites and spines. Time course and amplitude of both inward currents and sodium signals correlate with the duration of the uncaging pulse. Furthermore, our results show that intracellular sodium signals are blocked in the presence of blockers for ionotropic glutamate receptors, demonstrating that they are mediated by sodium influx though this pathway. In summary, our method provides a reliable tool for the investigation of intracellular sodium signals induced by focal receptor activation in intact brain tissue.

We describe the combination of focal UV-induced photo-activation of neuro-active compounds with whole-cell patch-clamp and multi-photon imaging of intracellular sodium transients in dendrites and spines of hippocampal neurons in acute tissue slices of the mouse brain.

Multi-photon intracelular de sódio Imagem Combinado com mediada por UV uncaging focal de glutamato em neurônios piramidais CA1

Multi-photon fluorescence microscopy has enabled the analysis of morphological and physiological parameters of brain cells in the intact tissue with high ...

A "Dual-Addition" Calcium Fluorescence Assay for the High-Throughput Screening of Recombinant G Protein-Coupled Receptors

G protein-coupled receptors (GPCRs) represent the largest superfamily of receptors and are the targets of numerous human drugs. High-throughput screening (HTS) of random small molecule libraries against GPCRs is used by the pharmaceutical industry for target-specific drug discovery. In this study, an HTS was employed to identify novel small-molecule ligands of invertebrate-specific neuropeptide GPCRs as probes for physiological studies of vectors of deadly human and veterinary pathogens.
The invertebrate-specific kinin receptor was chosen as a target because it regulates many important physiological processes in invertebrates, including diuresis, feeding, and digestion. Furthermore, the pharmacology of many invertebrate GPCRs is poorly characterized or not characterized at all; therefore, the differential pharmacology of these groups of receptors with respect to the related GPCRs in other metazoans, especially humans, adds knowledge to the structure-activity relationships of GPCRs as a superfamily. An HTS assay was developed for cells in 384-well plates for the discovery of ligands of the kinin receptor from the cattle fever tick, or southern cattle tick, Rhipicephalus microplus. The tick kinin receptor was stably expressed in CHO-K1 cells.
The kinin receptor, when activated by endogenous kinin neuropeptides or other small molecule agonists, triggers Ca2+ release from calcium stores into the cytoplasm. This calcium fluorescence assay combined with a &#34;dual-addition&#34; approach can detect functional agonist and antagonist &#34;hit&#34; molecules in the same assay plate. Each assay was conducted using drug plates carrying an array of 320 random small molecules. A reliable Z&#39; factor of 0.7 was obtained, and three agonist and two antagonist hit molecules were identified when the HTS was at a 2 &#181;M final concentration. The calcium fluorescence assay reported here can be adapted to screen other GPCRs that activate the Ca2+ signaling cascade.

In this work, a high-throughput, intracellular calcium fluorescence assay for 384-well plates to screen small molecule libraries on recombinant G protein-coupled receptors (GPCRs) is described. The target, the kinin receptor from the cattle fever tick, Rhipicephalus microplus, is expressed in CHO-K1 cells. This assay identifies agonists and antagonists using the same cells in one "dual-addition" assay.

Um ensaio de fluorescência de cálcio de "dupla adição" para a triagem de alto rendimento de receptores acoplados à proteína G recombinante

G protein-coupled receptors (GPCRs) represent the largest superfamily of receptors and are the targets of numerous human drugs. High-throughput screening ...

Bioquímica

Using Enzyme-based Biosensors to Measure Tonic and Phasic Glutamate in Alzheimer's Mouse Models

Neurotransmitter disruption is often a key component of diseases of the central nervous system (CNS), playing a role in the pathology underlying Alzheimer's disease, Parkinson's disease, depression, and anxiety. Traditionally, microdialysis has been the most common (lauded) technique to examine neurotransmitter changes that occur in these disorders. But because microdialysis has the ability to measure slow 1-20 minute changes across large areas of tissue, it has the disadvantage of invasiveness, potentially destroying intrinsic connections within the brain and a slow sampling capability. A relatively newer technique, the microelectrode array (MEA), has numerous advantages for measuring specific neurotransmitter changes within discrete brain regions as they occur, making for a spatially and temporally precise approach. In addition, using MEAs is minimally invasive, allowing for measurement of neurotransmitter alterations in vivo. In our laboratory, we have been specifically interested in changes in the neurotransmitter, glutamate, related to Alzheimer's disease pathology. As such, the method described here has been used to assess potential hippocampal disruptions in glutamate in a transgenic mouse model of Alzheimer's disease. Briefly, the method used involves coating a multi-site microelectrode with an enzyme very selective for the neurotransmitter of interest and using self-referencing sites to subtract out background noise and interferents. After plating and calibration, the MEA can be constructed with a micropipette and lowered into the brain region of interest using a stereotaxic device. Here, the method described involves anesthetizing rTg(TauP301L)4510 mice and using a stereotaxic device to precisely target sub-regions (DG, CA1, and CA3) of the hippocampus.

Here, we describe the setup, software navigation, and data analysis for a spatially and temporally precise method of measuring tonic and phasic extracellular glutamate changes in vivo using enzyme-linked microelectrode arrays (MEA).

Utilizando biossensores baseados em Enzyme medir Tonic e Phasic glutamato na doença de Alzheimer rato Models

Neurotransmitter disruption is often a key component of diseases of the central nervous system (CNS), playing a role in the pathology underlying ...

A High-content Assay for Monitoring AMPA Receptor Trafficking

Postsynaptic trafficking of receptors to and from the cell surface is an important mechanism by which neurons modulate their responsiveness to different stimuli. The &#945;-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, which are responsible for fast excitatory synaptic transmission in neurons, are trafficked to and from the postsynaptic surface to dynamically alter neuronal excitability. AMPA receptor trafficking is essential for synaptic plasticity and can be disrupted in neurological disease. However, prevalent approaches for quantifying receptor trafficking ignore entire receptor pools, are overly time- and labor-intensive, or potentially disrupt normal trafficking mechanisms and therefore complicate the interpretation of resulting data. We present a high-content assay for the quantification of both surface and internal AMPA receptor populations in cultured primary hippocampal neurons using dual fluorescent immunolabeling and a near-infrared fluorescent 96-well microplate scanner. This approach facilitates the rapid screening of bulk internalized and surface receptor densities while minimizing sample material. However, our method has limitations in obtaining single-cell resolution or conducting live cell imaging. Finally, this protocol may be amenable to other receptors and different cell types, provided proper adjustments and optimization.

Neuronal excitability can be modulated through a dynamic process of endo- and exocytosis of excitatory ionotropic glutamate receptors. Described here is an accessible, high-content assay for quantifying surface and internal receptor population pools.

Um ensaio de alto teor para monitoramento Leandro tráfico de Receptor

Postsynaptic trafficking of receptors to and from the cell surface is an important mechanism by which neurons modulate their responsiveness to different ...

An Antibody Feeding Approach to Study Glutamate Receptor Trafficking in Dissociated Primary Hippocampal Cultures

Cellular responses to external stimuli heavily rely on the set of receptors expressed at the cell surface at a given moment. Accordingly, the population of surface-expressed receptors is constantly adapting and subject to strict mechanisms of regulation. The paradigmatic example and one of the most studied trafficking events in biology is the regulated control of the synaptic expression of glutamate receptors (GluRs). GluRs mediate the vast majority of excitatory neurotransmission in the central nervous system and control physiological activity-dependent functional and structural changes at the synaptic and neuronal levels (e.g., synaptic plasticity). Modifications in the number, location, and subunit composition of surface expressed GluRs deeply affect neuronal function and, in fact, alterations in these factors are associated with different neuropathies. Presented here is a method to study GluR trafficking in dissociated hippocampal primary neurons. An &#34;antibody-feeding&#34; approach is used to differentially visualize GluR populations expressed at the surface and internal membranes. By labeling surface receptors on live cells and fixing them at different times to allow for receptors endocytosis and/or recycling, these trafficking processes can be evaluated and selectively studied. This is a versatile protocol that can be used in combination with pharmacological approaches or overexpression of altered receptors to gain valuable information about stimuli and molecular mechanisms affecting GluR trafficking. Similarly, it can be easily adapted to study other receptors or surface expressed proteins.

This article presents a method to study glutamate receptor (GluR) trafficking in dissociated primary hippocampal cultures. Using an antibody-feeding approach to label endogenous or overexpressed receptors in combination with pharmacological approaches, this method allows for the identification of molecular mechanisms regulating GluR surface expression by modulating internalization or recycling processes.

Uma abordagem de alimentação de anticorpos para estudar o tráfico de receptores de glutamato em culturas hipocampais primárias dissociadas

Cellular responses to external stimuli heavily rely on the set of receptors expressed at the cell surface at a given moment. Accordingly, the population ...

Single Synapse Indicators of Glutamate Release and Uptake in Acute Brain Slices from Normal and Huntington Mice

Synapses are highly compartmentalized functional units that operate independently on each other. In Huntington&#39;s disease (HD) and other neurodegenerative disorders, this independence might be compromised due to insufficient glutamate clearance and the resulting spill-in and spill-out effects. Altered astrocytic coverage of the presynaptic terminals and/or dendritic spines as well as a reduced size of glutamate transporter clusters at glutamate release sites have been implicated in the pathogenesis of diseases resulting in symptoms of dys-/hyperkinesia. However, the mechanisms leading to the dysfunction of glutamatergic synapses in HD are not well understood. Improving and applying synapse imaging we have obtained data shedding new light on the mechanisms impeding the initiation of movements. Here, we describe the principle elements of a relatively inexpensive approach to achieve single synapse resolution by using the new genetically encoded ultrafast glutamate sensor iGluu, wide-field optics, a scientific CMOS (sCMOS) camera, a 473 nm laser and a laser positioning system to evaluate the state of corticostriatal synapses in acute slices from age appropriate healthy or diseased mice. Glutamate transients were constructed from single or multiple pixels to obtain estimates of i) glutamate release based on the maximal elevation of the glutamate concentration [Glu] next to the active zone and ii) glutamate uptake as reflected in the time constant of decay (TauD) of the perisynaptic [Glu]. Differences in the resting bouton size and contrasting patterns of short-term plasticity served as criteria for the identification of corticostriatal terminals as belonging to the intratelencephalic (IT) or the pyramidal tract (PT) pathway. Using these methods, we discovered that in symptomatic HD mice ~40% of PT-type corticostriatal synapses exhibited insufficient glutamate clearance, suggesting that these synapses might be at risk to excitotoxic damage. The results underline the usefulness of TauD as a biomarker of dysfunctional synapses in Huntington mice with a hypokinetic phenotype.

We present a protocol to evaluate the balance between glutamate release and clearance at single corticostriatal glutamatergic synapses in acute slices from adult mice. This protocol uses the fluorescent sensor iGluu for glutamate detection, a sCMOS camera for signal acquisition and a device for focal laser illumination.

Indicadores únicos de sinapse de liberação de glutamato e absorção em fatias cerebrais agudas de ratos normais e huntington

Synapses are highly compartmentalized functional units that operate independently on each other. In Huntington&#39;s disease (HD) and other ...

Quantifying Spontaneous Ca2+ Fluxes and their Downstream Effects in Primary Mouse Midbrain Neurons

Parkinson&#8217;s disease (PD) is a devastating neurodegenerative disorder caused by the degeneration of dopaminergic (DA) neurons. Excessive Ca2+ influx due to the abnormal activation of glutamate receptors results in DA excitotoxicity and has been identified as an important mechanism for DA neuron loss. In this study, we isolate, dissociate, and culture midbrain neurons from the mouse ventral mesencephalon (VM) of ED14 mouse embryos. We then infect the long-term primary mouse midbrain cultures with an adeno-associated virus (AAV) expressing a genetically encoded calcium indicator, GCaMP6f under control of the human neuron-specific synapsin promoter, hSyn. Using live confocal imaging, we show that cultured mouse midbrain neurons display spontaneous Ca2+ fluxes detected by AAV-hSyn-GCaMP6f. Bath application of glutamate to midbrain cultures causes abnormal elevations in intracellular Ca2+ within neurons and this is accompanied by caspase-3 activation in DA neurons, as demonstrated by immunostaining. The techniques to identify glutamate-mediated apoptosis in primary mouse DA neurons have important applications for the high content screening of drugs that preserve DA neuron health.

Quantifying Spontaneous Ca2+ Fluxes and their Downstream Effects in Primary Mouse Midbrain Neurons

Here we present a protocol to measure in vitro Ca2+ fluxes in midbrain neurons and their downstream effects on caspase-3 using primary mouse midbrain cultures. This model can be employed to study pathophysiologic changes related to abnormal Ca2+ activity in midbrain neurons, and to screen novel therapeutics for anti-apoptotic properties.

Quantificando fluxos espontâneos ca2+ e seus efeitos a jusante em neurônios midcérebros do rato primário

Parkinson&#8217;s disease (PD) is a devastating neurodegenerative disorder caused by the degeneration of dopaminergic (DA) neurons. Excessive Ca2+ influx ...

One-channel Cell-attached Patch-clamp Recording

Ion channel proteins are universal devices for fast communication across biological membranes. The temporal signature of the ionic flux they generate depends on properties intrinsic to each channel protein as well as the mechanism by which it is generated and controlled and represents an important area of current research. Information about the operational dynamics of ion channel proteins can be obtained by observing long stretches of current produced by a single molecule. Described here is a protocol for obtaining one-channel cell-attached patch-clamp current recordings for a ligand gated ion channel, the NMDA receptor, expressed heterologously in HEK293 cells or natively in cortical neurons. Also provided are instructions on how to adapt the method to other ion channels of interest by presenting the example of the mechano-sensitive channel PIEZO1. This method can provide data regarding the channel&#8217;s conductance properties and the temporal sequence of open-closed conformations that make up the channel&#8217;s activation mechanism, thus helping to understand their functions in health and disease.

Described here is a procedure for obtaining long stretches of current recording from one ion channel with the cell-attached patch-clamp technique. This method allows for observing, in real time, the pattern of open-close channel conformations that underlie the biological signal. These data inform about channel properties in undisturbed biological membranes.

Um canal de gravação de patch-clamp anexado-Cell

Ion channel proteins are universal devices for fast communication across biological membranes. The temporal signature of the ionic flux they generate ...

Biologia

Real-Time Fluorescent Measurement of Synaptic Functions in Models of Amyotrophic Lateral Sclerosis

Before neuronal degeneration, the cause of motor and cognitive deficits in patients with amyotrophic lateral sclerosis (ALS) and/or frontotemporal lobe dementia (FTLD) is dysfunction of communication between neurons and motor neurons and muscle. The underlying process of synaptic transmission involves membrane depolarization-dependent synaptic vesicle fusion and the release of neurotransmitters into the synapse. This process occurs through localized calcium influx into the presynaptic terminals where synaptic vesicles reside. Here, the protocol describes fluorescence-based live-imaging methodologies that reliably report depolarization-mediated synaptic vesicle exocytosis and presynaptic terminal calcium influx dynamics in cultured neurons.
Using a styryl dye that is incorporated into synaptic vesicle membranes, the synaptic vesicle release is elucidated. On the other hand, to study calcium entry, Gcamp6m is used, a genetically encoded fluorescent reporter. We employ high potassium chloride-mediated depolarization to mimic neuronal activity. To quantify synaptic vesicle exocytosis unambiguously, we measure the loss of normalized styryl dye fluorescence as a function of time. Under similar stimulation conditions, in the case of calcium influx, Gcamp6m fluorescence increases. Normalization and quantification of this fluorescence change are performed in a similar manner to the styryl dye protocol. These methods can be multiplexed with transfection-based overexpression of fluorescently tagged mutant proteins. These protocols have been extensively used to study synaptic dysfunction in models of FUS-ALS and C9ORF72-ALS, utilizing primary rodent cortical and motor neurons. These protocols easily allow for rapid screening of compounds that may improve neuronal communication. As such, these methods are valuable not only for the study of ALS but for all areas of neurodegenerative and developmental neuroscience research.

Two related methods are described to visualize subcellular events required for synaptic transmission. These protocols enable the real-time monitoring of the dynamics of presynaptic calcium influx and synaptic vesicle membrane fusion using live-cell imaging of in vitro cultured neurons.

Medição fluorescente em tempo real de funções sinápticas em modelos de esclerose lateral amiotrófica

Before neuronal degeneration, the cause of motor and cognitive deficits in patients with amyotrophic lateral sclerosis (ALS) and/or frontotemporal lobe ...