Agradecemos a la Sra. Tess J. Lameyer, la Sra. Ruth Frank y el Dr. Michael A. Muniak por sus ediciones y comentarios, y al Dr. Ryohei Yasuda en Max Planck Florida por el software de adquisición 2pFLIM. Este trabajo fue apoyado por dos premios de la Iniciativa BRAIN U01NS094247 (H.Z. y T.M.) y R01NS104944 (H.Z. y T.M.), una concesión R01NS081071 (T.M.) y una concesión R21R2197856 (H.Z.). Todos los premios son del Instituto Nacional de Trastornos Neurológicos y Accidentes Cerebrovasculares, Estados Unidos.

<ol>
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E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liberated+PKA+Catalytic+Subunits+Associate+with+the+Membrane+via+Myristoylation+to+Preferentially+Phosphorylate+Membrane+Substrates.">Liberated PKA Catalytic Subunits Associate with the Membrane via Myristoylation to Preferentially Phosphorylate Membrane Substrates.</a> Cell Reports. 19 (3), 617-629 (2017).</li><li>Yasuda, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+spatiotemporal+dynamics+of+neuronal+signaling+using+fluorescence+resonance+energy+transfer+and+fluorescence+lifetime+imaging+microscopy.">Imaging spatiotemporal dynamics of neuronal signaling using fluorescence resonance energy transfer and fluorescence lifetime imaging microscopy.</a> Current Opinion in Neurobiology. 16 (5), 551-561 (2006).</li><li>Theurkauf, W. 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Los autores no tienen nada que revelar.

Este protocolo demuestra el uso del sensor FRET-FLIM tAKAR para visualizar la actividad PKA activada por neuromodulación en ratones que se comportan en la cabeza fija. Esta aplicación se basa en extensas pruebas y caracterizaciones de tAKAR in vitro e in vivo para demostrar que la señal FLIM obtenida es relevante para eventos neuromoduladores fisiológicos17. Aquí, una aplicación in vivo, la actividad de PKA inducida por la locomoción en la corteza motora, se utiliza para describir los proce...

La neuromodulación, también conocida como transmisión sináptica lenta, impone un fuerte control sobre la función cerebral durante diferentes estados conductuales, como el estrés, la excitación, la atención y la locomoción1,2,3, 4. A pesar de su importancia, el estudio de cuándo y dónde tienen lugar los eventos neuromoduladores todavía está en su infancia. Neuromoduladores, incluyendo acetilcolina, dopamina, noradrenalina, serotonina, y muchos neuropéptidos, activar los receptores acoplados a la proteína G (GPCRs), que a su vez desencadenan las segundas vías mensajeras intracelulares con una amplia ventana de escalas de tiempo que van de segundos a horas. Mientras que cada neuromodulador desencadena un conjunto distinto de eventos de señalización, la vía de la quinasa de campo/proteína A (PKA) es una vía descendente común para muchos neuromoduladores1,5. La vía del campo/PKA regula la excitabilidad neuronal, latransmisión sináptica y la plasticidad 6,7,8,9y, por lo tanto, ajusta la dinámica de la red neuronal. Debido a que diferentes neuronas o tipos neuronales expresan diferentes tipos o niveles de receptores neuromoduladores10, los efectos intracelulares del mismo neuromodulador extracelular pueden ser heterogéneos a través de diferentes neuronas, y por lo tanto, tienen que ser estudiado con resolución celular. Hasta la fecha, sigue siendo difícil monitorear eventos neuromoduladores en neuronas individuales in vivo durante el comportamiento.
Para estudiar la dinámica espaciotemporal de la neuromodulación, se requiere una modalidad de grabación adecuada. La microdiálisis y la voltammetría cíclica de exploración rápida se utilizan con frecuencia para estudiar la liberación de neuromoduladores, pero carecen de la resolución espacial para monitorear los eventos celulares11,12. Análoga a la dinámica de calcio que se utiliza como un proxy para la actividad eléctrica neuronal en la población por imágenes13, la imagen PKA se puede utilizar para leer eventos neuromoduladores a través de una población neuronal a resolución celular. El presente protocolo describe el uso de un reportero mejorado de actividad A-quinasa (AKAR) para monitorear las actividades de PKA in vivo durante el comportamiento animal. El método descrito aquí permite la toma simultánea de imágenes de poblaciones neuronales a resolución subcelular con una resolución temporal que realiza un seguimiento de los eventos neuromoduladores fisiológicos.
Los AKARs están compuestos por un donante y un aceptador de proteínas fluorescentes vinculadas por un péptido de sustrato de fosforilación PKA y un dominio asociado a la cabeza de horquilla (FHA) que se une a la serina fosforilada o trionina del sustrato14,15. Tras la activación de la vía PKA, el péptido de sustrato de AKAR se fosforila. Como resultado, el dominio FHA se une al péptido de sustrato fosforilado, lo que acerca a los dos fluoróforos, denominado salente el estado cerrado de AKAR. El estado cerrado de un AKAR fosforilado da lugar a un aumento de la transferencia de energía por resonancia de Farster (FRET) entre el donante y los fluoróforos del donante y del aceptador. Dado que la proporción de AKARs fosforilados está relacionada con el nivel de actividad de PKA16, la cantidad de FRET en una muestra biológica se puede utilizar para cuantificar el nivel de actividad de PKA16,17,18, 19,20.
Las primeras versiones de los AKARs se diseñaron principalmente para imágenes de dos colores ratiométricas14. Al obtener imágenes más profundas en el tejido cerebral, el método ratiométrico sufre de distorsión de la señal debido a la dispersión de luz dependiente de la longitud de onda17,18,21. Como se explica a continuación, la microscopía por imágenes de por vida de fluorescencia (FLIM) elimina este problema porque FLIM solo mide los fotones emitidos por el fluoróforo18,21. Como resultado, la cuantificación FLIM de FRET no se ve afectada por la profundidad tisular17. Además, se puede utilizar una variante "oscura" (es decir, bajo rendimiento cuántico [QY]) del fluoróforo del aceptador. Esto libera un canal de color para facilitar la medición multiplexada de propiedades neuronales ortogonales a través de imágenes simultáneas de un segundo sensor o un marcador morfológico17,19,20.
Las imágenes FLIM cuantifican el tiempo que un fluoróforo pasa en el estado excitado, es decir, la vida útil de la fluorescencia18. El regreso de un fluoróforo al estado de tierra, por lo tanto el final del estado excitado, a menudo conconcomita con la emisión de un fotón. Aunque la emisión de un fotón para una molécula excitada individual es estocástica, en una población la vida media de fluorescencia es una característica de ese fluoróforo en particular. Cuando una población pura de fluoróforos se excita simultáneamente, la fluorescencia resultante seguirá una sola decadencia exponencial. La constante de tiempo de esta decaimiento exponencial corresponde a la vida útil media de la fluorescencia, que normalmente oscila entre uno y cuatro nanosegundos para las proteínas fluorescentes. El regreso de un fluoróforo de donante excitado al estado de tierra también puede ocurrir por FRET. En presencia de FRET, se reduce la vida útil de fluorescencia del fluoróforo del donante. Los AKARs sin fosforilar exhiben una vida útil de fluorescencia de donante relativamente más larga. Tras la fosforilación por PKA, el sensor exhibe una vida útil más corta porque los fluoróforos del donante y del aceptador se acercan entre sí y se incrementa el FRET. Por lo tanto, la cuantificación de la vida útil de la fluorescencia en una población de AKARs representa el nivel de actividad de PKA.
Las primeras versiones de los AKARs no se han utilizado con éxito para imágenes in vivo con resolución de una sola célula. Esto se debe principalmente a la baja amplitud de la señal de los sensores AKAR a las activaciones fisiológicas17. Recientemente, al comparar sistemáticamente los sensores AKAR disponibles para la microscopía de imágenes de por vida de fluorescencia de dos fotones (2pFLIM), se descubrió que un sensor llamado FLIM-AKAR supera a los sensores alternativos. Además, se desarrollaron una serie de variantes FLIM-AKAR llamadas AKARs (tAKARs) específicas para visualizar la actividad de PKA en ubicaciones subcelulares específicas: microtúbulos (tAKAR), citosol (tAKAR), actina (tAKAR), actina filamentosa (tAKAR), membrana (tAKAR), y la densidad postsináptica (tAKAR). Entre los tAKAR, el tAKAR aumentó la amplitud de la señal provocada por la noradrenalina en 2,7 veces. Esto es consistente con el conocimiento de que la mayoría de PKA en las neuronas están ancladas a microtúbulos en el estado de reposo22,23. tAKAR fue el mejor intérprete entre los AKAR existentes para 2pFLIM. Además, el tAKAR detectó actividad de PKA fisiológicamente relevante provocada por múltiples neuromoduladores, y la expresión de tAKAR no alteró las funciones neuronales17.
Recientemente, tAKAR se utilizó con éxito para visualizar las actividades de PKA en ratones de afeitar fijos17. Se demostró que la locomoción forzada desencadenó la actividad de PKA en el soma de las neuronas de capa superficial (capa 1 a 3, hasta una profundidad de 300 m de pia) en el motor, barril y cortices visuales. La actividad de PKA desencadenada por la locomoción dependía en parte de la señalización a través de receptores adrenérgicos y receptores de dopamina D1, pero no fue afectada por un antagonista del receptor de dopamina D2. Este trabajo ilustra la capacidad de los tAKARs para rastrear eventos de neuromodulación in vivo usando 2pFLIM.
En el protocolo actual, todo el método para la creación de imágenes de actividad PKA en ratones despiertos fijos durante un paradigma de locomoción forzado se describe en seis pasos. En primer lugar, la adición de capacidades 2pFLIM a un microscopio convencional de dos fotones (Figura1). En segundo lugar, la construcción de una cinta de correr motorizada (Figura2). En tercer lugar, la expresión del sensor tAKAR en la corteza del ratón por la electroporación utero (IUE) de los plásmidos de ADN, o la inyección estereotaxcócica del virus asociado al adeno (AAV). Se han publicado previamente excelentes protocolos para cirugías para IUE24,25 e inyección estereotaxia de partículas virales26. Los parámetros clave que utilizamos se describen a continuación. En adelante, la instalación de una ventana craneal. Excelentes protocolos han sido publicados previamente para la cirugía de ventana craneal27,28. Se describen varios pasos que se han modificado desde los protocolos estándar. Quinto, actuando in vivo 2pFLIM. En sexto lugar, los análisis de imágenes 2pFLIM (Figura3 y Figura 4). Este enfoque debe ser fácilmente aplicable a muchos otros paradigmas de comportamiento fijos en la cabeza y áreas cerebrales.

<table>
	<tbody>
		<tr>
			<td>0.2 &#956;m cellulose acetate syringe filter</td>
			<td>Nalgene</td>
			<td>190-2520</td>
			<td>Step 3.2.2.</td>
		</tr>
		<tr>
			<td>16x 0.8 NA water-immersion objective</td>
			<td>Nikon</td>
			<td>MRP07220</td>
			<td>Step 5.5.</td>
		</tr>
		<tr>
			<td>3-pin cable</td>
			<td>US digital</td>
			<td>CA-MIC3-SH-NC</td>
			<td>Step 2.5. To connect rotation sensor to the DAQ input of the microscope</td>
		</tr>
		<tr>
			<td>Aluminum bread board</td>
			<td>Thorlabs</td>
			<td>MB1012</td>
			<td>Step 2.5.</td>
		</tr>
		<tr>
			<td>AnimalTracker MATLAB software</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Step 2.5 and sections 5 - 6. Will be provided upon request to the lead author</td>
		</tr>
		<tr>
			<td>Band-pass barrier filter</td>
			<td>Chroma</td>
			<td>ET500-40m</td>
			<td>Step 1.4.</td>
		</tr>
		<tr>
			<td>Cage plate</td>
			<td>Thorlabs</td>
			<td>CP01</td>
			<td>Step 2.4. Used as mount for rotation sensor</td>
		</tr>
		<tr>
			<td>Carbon steel burrs for micro drill, 0.5 mm tip diameter</td>
			<td>FST</td>
			<td>19007-05</td>
			<td>Steps 3.2.3. and 4.4.</td>
		</tr>
		<tr>
			<td>Circular coverslip (5mm diameter)</td>
			<td>VWR</td>
			<td>101413-528</td>
			<td>Step 4.5.</td>
		</tr>
		<tr>
			<td>Custom-made injection needle holder</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Step 3.2.4. Technical details provided upon request to the lead author</td>
		</tr>
		<tr>
			<td>Dental acrylic</td>
			<td>Yates Motloid</td>
			<td>44114</td>
			<td>Steps 4.3. and 4.5.</td>
		</tr>
		<tr>
			<td>Dental drill; Microtorque ii</td>
			<td>Ram products</td>
			<td>66699</td>
			<td>Steps 3.2.3. and 4.4.</td>
		</tr>
		<tr>
			<td>Dowsil transparent polymer</td>
			<td>The Dow Chemical Company</td>
			<td>3-4680</td>
			<td>Step 4.5. Artificial dura</td>
		</tr>
		<tr>
			<td>Electroporation electrode</td>
			<td>Bex</td>
			<td>LF650P5</td>
			<td>Step 3.1.4.</td>
		</tr>
		<tr>
			<td>Electroporator</td>
			<td>Bex</td>
			<td>CUY21</td>
			<td>Step 3.1.4.</td>
		</tr>
		<tr>
			<td>Fast green FCF</td>
			<td>Sigma-aldrich</td>
			<td>F7258-25G</td>
			<td>Step 3.1.1.</td>
		</tr>
		<tr>
			<td>FLIMimage MATLAB software</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Section 5. Kindly provided by Dr. Ryohei Yasuda, Max Planck Florida</td>
		</tr>
		<tr>
			<td>FLIMview MATLAB software</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Sections 5. and 6. Will be provided upon request to the lead author</td>
		</tr>
		<tr>
			<td>Foam-compatible glue (Gorilla White Glue)</td>
			<td>Gorilla</td>
			<td>5201204</td>
			<td>Step 2.3.</td>
		</tr>
		<tr>
			<td>Headplate</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Step 4.3. Technical details provided upon request to the lead author</td>
		</tr>
		<tr>
			<td>Headplate holder</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Step 2.6. Technical details provided upon request lead author, used in combination with mounting post bracket and right-angled bracket</td>
		</tr>
		<tr>
			<td>Hydraulic micromanipulator</td>
			<td>Narishige</td>
			<td>MO-10</td>
			<td>Step 3.2.4.</td>
		</tr>
		<tr>
			<td>Krazy glue</td>
			<td>Krazy glue</td>
			<td>KG82648R</td>
			<td>Step 4.3. Cyanoacrylate-based glue</td>
		</tr>
		<tr>
			<td>Low-noise fast photomultiplier tube</td>
			<td>Hamamatsu</td>
			<td>H7422PA-40 or H10769PA-40</td>
			<td>Step 1.3.</td>
		</tr>
		<tr>
			<td>MATLAB 2012b</td>
			<td>Mathworks</td>
			<td>N/A</td>
			<td>Steps 2.6, and sections 5, and 6. Used to run microscope acquisition and data analysis software</td>
		</tr>
		<tr>
			<td>Motor</td>
			<td>Zhengke</td>
			<td>ZGA37RG</td>
			<td>Step 2.4.</td>
		</tr>
		<tr>
			<td>Motor speed controller</td>
			<td>Elenker</td>
			<td>EK-G00015A1-1</td>
			<td>Step 2.5.</td>
		</tr>
		<tr>
			<td>Motorized micromanipulator</td>
			<td>Sutter</td>
			<td>MP-285</td>
			<td>Step 3.2.4.</td>
		</tr>
		<tr>
			<td>Mounting base</td>
			<td>Thorlabs</td>
			<td>BA1S</td>
			<td>Step 2.5. Used for posts for motor and sensor in combination with PH4 and TR2</td>
		</tr>
		<tr>
			<td>Mounting post</td>
			<td>Thorlabs</td>
			<td>P14</td>
			<td>Step 2.6. Used for headplate holder post in combination with PB2</td>
		</tr>
		<tr>
			<td>Mounting post base</td>
			<td>Thorlabs</td>
			<td>PB2</td>
			<td>Step 2.6. Used for headplate holder post in combination with P14</td>
		</tr>
		<tr>
			<td>Mounting post bracket</td>
			<td>Thorlabs</td>
			<td>C1515</td>
			<td>Step 2.6. Used in combination with right-angle bracket and headplate holder</td>
		</tr>
		<tr>
			<td>Optical post</td>
			<td>Thorlabs</td>
			<td>TR2</td>
			<td>Step 2.5. Used for posts for motor and sensor in combination with BA1S and PH4</td>
		</tr>
		<tr>
			<td>Phosphate-buffered saline</td>
			<td>&#925;/&#913;</td>
			<td>&#925;/&#913;</td>
			<td>Step 3.2.2. Protocol: Cold Spring Harbor Protocols 2006, doi: 10.1101/pbd.rec8247</td>
		</tr>
		<tr>
			<td>Photodiode</td>
			<td>Thorlabs</td>
			<td>FDS010</td>
			<td>Step 1.2.</td>
		</tr>
		<tr>
			<td>Photon timing counting module</td>
			<td>Becker and Hickl</td>
			<td>SPC-150</td>
			<td>Step 1.1.</td>
		</tr>
		<tr>
			<td>Plasmid: tAKAR&#945; (CAG-tAKAR&#945;-WPRE)</td>
			<td>Addgene</td>
			<td>119913</td>
			<td>Step 3.1.3.</td>
		</tr>
		<tr>
			<td>Post holder</td>
			<td>Thorlabs</td>
			<td>PH4</td>
			<td>Step 2.5. Used for posts for motor and sensor in combination with BA1S and TR2</td>
		</tr>
		<tr>
			<td>Right-angle bracket</td>
			<td>Thorlabs</td>
			<td>AB90</td>
			<td>Step 2.6 Used in combination with mounting post bracket and headplate holder</td>
		</tr>
		<tr>
			<td>Rotation sensor</td>
			<td>US digital</td>
			<td>MA3-A10-250-N</td>
			<td>Step 2.4.</td>
		</tr>
		<tr>
			<td>Rubber mat</td>
			<td>Rubber-Cal</td>
			<td>B01DCR5LUG</td>
			<td>Step 2.1.</td>
		</tr>
		<tr>
			<td>Shaft coupling (1/4 inch x 1/4 inch)</td>
			<td>McMaster</td>
			<td>6208K433</td>
			<td>Steps 2.3. and 2.4.</td>
		</tr>
		<tr>
			<td>ScanImage 3.6</td>
			<td>Svoboda Lab/Vidrio Technology</td>
			<td>N/A</td>
			<td>Steps 5.9. and 6.1.</td>
		</tr>
		<tr>
			<td>Signal splitter</td>
			<td>Becker and Hickl</td>
			<td>HPM-CON-02</td>
			<td>Step 1.3.1.</td>
		</tr>
		<tr>
			<td>Stainless steel axle (diameter 1/4 inch, L = 12 inch)</td>
			<td>McMaster</td>
			<td>1327K66</td>
			<td>Step 2.3.</td>
		</tr>
		<tr>
			<td>Stereotaxic alignment systsem</td>
			<td>David kopf</td>
			<td>1900</td>
			<td>Steps 3.2. and 4.1. modified; Sutter micromanipulator, custom-made injection needle holder, hydraulic micromanipulator</td>
		</tr>
		<tr>
			<td>Two-photon microscope</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Section 5. Built based on Modular in vivo multiphoton microscopy system (MIMMS) from HHMI Janelia Research Campus (https://www.janelia.org/open-science/mimms)</td>
		</tr>
		<tr>
			<td>Vetbond tissue adhesive</td>
			<td>3M</td>
			<td>14006</td>
			<td>Step 3.2.6.</td>
		</tr>
		<tr>
			<td>Virus: tAKAR&#945; (AAV2/1 hSyn-tAKAR&#945;-WPRE)</td>
			<td>Addgene</td>
			<td>119921</td>
			<td>Step 3.2.2.</td>
		</tr>
		<tr>
			<td>White PE foam roller (8 x 12 inch)</td>
			<td>Fabrication enterprises INC.</td>
			<td>30-2261</td>
			<td>Step 2.1.1.</td>
		</tr>
		<tr>
			<td>White polystyrene fom ball halves</td>
			<td>GrahamSweet</td>
			<td>200mm diameter 2 hollow halves</td>
			<td>Step 2.1.1.</td>
		</tr>
		<tr>
			<td>Zipkicker</td>
			<td>PACER</td>
			<td>PT29</td>
			<td>Step 4.3. Hardening accelerator</td>
		</tr>
	</tbody>
</table>

visualizing protein kinase a activity in head-fixed behaving mice using in vivo two-photon fluorescence lifetime imaging microscopy

La neuromodulación ejerce un poderoso control sobre la función cerebral. La disfunción de los sistemas neuromoduladores da lugar a trastornos neurológicos y psiquiátricos. A pesar de su importancia, las tecnologías para rastrear eventos neuromoduladores con resolución celular están empezando a surgir. Los neuromoduladores, como la dopamina, la noradrenalina, la acetilcolina y la serotonina, desencadenan eventos de señalización intracelular a través de sus respectivos receptores acoplados a proteínas G para modular la excitabilidad neuronal, las comunicaciones sinápticas y otras regulando así el procesamiento de la información en la red neuronal. Los neuromoduladores mencionados anteriormente convergen en la vía adentro/proteína quinasa A (PKA). Por lo tanto, la imagen de PKA in vivo con resolución de una sola célula se desarrolló como una lectura para eventos neuromoduladores de una manera análoga a las imágenes de calcio para actividades eléctricas neuronales. En este documento, se presenta un método para visualizar la actividad de PKA a nivel de neuronas individuales en la corteza de ratones que se comportan por la cabeza fija. Para ello, se utiliza un reportero mejorado de actividad De la A-quinasa (AKAR), llamado tAKAR, que se basa en la transferencia de energía por resonancia de Farster (FRET). Este sensor PKA genéticamente codificado se introduce en la corteza motora a través de la electroporación utero (IUE) de plásmidos de ADN, o inyección estereotaxcócica de virus asociado a adeno (AAV). Los cambios de FRET se utilizan mediante la microscopía de imágenes de por vida de fluorescencia de dos fotones (2pFLIM), que ofrece ventajas sobre las mediciones ratiométricas de FRET para cuantificar la señal FRET en el tejido cerebral de dispersión de luz. Para estudiar las actividades de PKA durante la locomoción forzada, el tAKAR se imagea a través de una ventana craneal crónica por encima de la corteza de ratones despiertos fijos en la cabeza, que corren o descansan en una cinta de correr motorizada con control de velocidad. Este enfoque de diagnóstico por imágenes será aplicable a muchas otras regiones cerebrales para estudiar las actividades de PKA inducidas por el comportamiento correspondientes y a otros sensores basados en FLIM para imágenes in vivo.

Los sensores FRET-FLIM permiten la visualización de muchas vías de señalización diferentes, incluida la vía de campo/PKA implicada en la neuromodulación. El protocolo actual utiliza el sensor tAKAR recientemente desarrollado en combinación con 2pFLIM para visualizar las actividades de PKA en ratones que se comportan con cabeza fija. La mayoría de los microscopios de dos fotones existentes se pueden actualizar con capacidades 2pFLIM añadiendo tres a cuatro componentes, como se ilu...

Watch this Scientific Journal Video about Visualizing Protein Kinase A Activity In Head-fixed Behaving Mice Using In Vivo Two-photon Fluorescence Lifetime Imaging Microscopy at JoVE.com

Visualizing Protein Kinase A Activity In Head-fixed Behaving Mice Using In Vivo Two-photon Fluorescence Lifetime Imaging Microscopy

Se presenta un procedimiento para visualizar las actividades de proteína quinasa A en ratones que se fijan en la cabeza y se comportan. Un reportero mejorado de actividad de A-quinasa, tAKAR, se expresa en las neuronas corticales y se hace accesible para la toma de imágenes a través de una ventana craneal. La microscopía por imágenes de por vida de fluorescencia de dos fotones se utiliza para visualizar las actividades de PKA in vivo durante la locomoción forzada.

Visualización de la proteína quinasa Una actividad en ratones de trabajo fijos en la cabeza utilizando la microscopía de imágenes de por vida con fluorescencia de dos fotones in Vivo

Neuromodulation exerts powerful control over brain function. Dysfunction of neuromodulatory systems results in neurological and psychiatric disorders. ...

Nuestro método utiliza un novedoso sensor de proteína quinasa A llamado target A kinase activity reporter alpha, o tAKAR

visualizing-protein-kinase-activity-head-fixed-behaving-mice-using

Research

JoVE Journal

Neuroscience

8.3K vistas.  Oregon Health & Science University. Nuestro método utiliza un novedoso sensor de proteína quinasa A llamado target A kinase activity reporter alpha, o tAKAR

Video: Visualizing Protein Kinase A Activity In Head-fixed Behaving Mice Using In Vivo Two-photon Fluorescence Lifetime Imaging Microscopy

In vivo Imaging of the Mouse Spinal Cord Using Two-photon Microscopy

In vivo imaging using two-photon microscopy 1 in mice that have been genetically engineered to express fluorescent proteins in specific cell types 2-3 has significantly broadened our knowledge of physiological and pathological processes in numerous tissues in vivo 4-7. In studies of the central nervous system (CNS), there has been a broad application of in vivo imaging in the brain, which has produced a plethora of novel and often unexpected findings about the behavior of cells such as neurons, astrocytes, microglia, under physiological or pathological conditions 8-17. However, mostly technical complications have limited the implementation of in vivo imaging in studies of the living mouse spinal cord. In particular, the anatomical proximity of the spinal cord to the lungs and heart generates significant movement artifact that makes imaging the living spinal cord a challenging task.
We developed a novel method that overcomes the inherent limitations of spinal cord imaging by stabilizing the spinal column, reducing respiratory-induced movements and thereby facilitating the use of two-photon microscopy to image the mouse spinal cord in vivo. This is achieved by combining a customized spinal stabilization device with a method of deep anesthesia, resulting in a significant reduction of respiratory-induced movements. This video protocol shows how to expose a small area of the living spinal cord that can be maintained under stable physiological conditions over extended periods of time by keeping tissue injury and bleeding to a minimum. Representative raw images acquired in vivo detail in high resolution the close relationship between microglia and the vasculature. A timelapse sequence shows the dynamic behavior of microglial processes in the living mouse spinal cord. Moreover, a continuous scan of the same z-frame demonstrates the outstanding stability that this method can achieve to generate stacks of images and/or timelapse movies that do not require image alignment post-acquisition. Finally, we show how this method can be used to revisit and reimage the same area of the spinal cord at later timepoints, allowing for longitudinal studies of ongoing physiological or pathological processes in vivo.

In vivo Imaging of the Mouse Spinal Cord Using Two-photon Microscopy

A minimally invasive protocol to stabilize the mouse spinal column and perform repetitive in vivo spinal cord imaging using two-photon microscopy is described. This method combines a spinal stabilization device and an anesthetic regimen to minimize respiratory-induced movements and produce raw imaging data that require no alignment or other post-processing.

Imágenes in vivo de la médula espinal de ratón Utilizando microscopía de dos fotones

In vivo imaging using two-photon microscopy 1 in mice that have been genetically engineered to express fluorescent proteins in specific cell types 2-3 has ...

Investigación

Neurociencias

Functional Neuroimaging Using Ultrasonic Blood-brain Barrier Disruption and Manganese-enhanced MRI

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains technically challenging. One approach, Activation-Induced Manganese-enhanced MRI (AIM MRI), has been used successfully to map neuronal activity in rodents 1-5. In AIM MRI, Mn2+ acts a calcium analog and accumulates in depolarized neurons 6,7. Because Mn2+ shortens the T1 tissue property, regions of elevated neuronal activity will enhance in MRI. Furthermore, Mn2+ clears slowly from the activated regions; therefore, stimulation can be performed outside the magnet prior to imaging, enabling greater experimental flexibility. However, because Mn2+ does not readily cross the blood-brain barrier (BBB), the need to open the BBB has limited the use of AIM MRI, especially in mice.
One tool for opening the BBB is ultrasound. Though potentially damaging, if ultrasound is administered in combination with gas-filled microbubbles (i.e., ultrasound contrast agents), the acoustic pressure required for BBB opening is considerably lower. This combination of ultrasound and microbubbles can be used to reliably open the BBB without causing tissue damage 8-11.
Here, a method is presented for performing AIM MRI by using microbubbles and ultrasound to open the BBB. After an intravenous injection of perflutren microbubbles, an unfocused pulsed ultrasound beam is applied to the shaved mouse head for 3 minutes. For simplicity, we refer to this technique of BBB Opening with Microbubbles and UltraSound as BOMUS 12. Using BOMUS to open the BBB throughout both cerebral hemispheres, manganese is administered to the whole mouse brain. After experimental stimulation of the lightly sedated mice, AIM MRI is used to map the neuronal response.
To demonstrate this approach, herein BOMUS and AIM MRI are used to map unilateral mechanical stimulation of the vibrissae in lightly sedated mice 13. Because BOMUS can open the BBB throughout both hemispheres, the unstimulated side of the brain is used to control for nonspecific background stimulation. The resultant 3D activation map agrees well with published representations of the vibrissae regions of the barrel field cortex 14. The ultrasonic opening of the BBB is fast, noninvasive, and reversible; and thus this approach is suitable for high-throughput and/or longitudinal studies in awake mice.

A technique is described for broadly opening the blood-brain barrier in the mouse using microbubbles and ultrasound. Using this technique, manganese can be administered to the mouse brain. Because manganese is an MRI contrast agent that accumulates in depolarized neurons, this approach enables imaging of neuronal activity.

Neuroimagen Funcional Utilizando ultrasonidos hematoencefálica perturbación de la barrera y la RM-manganeso mayor

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains ...

In Vivo Two-Photon Microscopy of Single Nerve Endings in Skin

Nerve endings in skin are involved in physiological processes such as sensing1 as well as in pathological processes such as neuropathic pain2. Their close-to-surface positioning facilitates microscopic imaging of skin nerve endings in living intact animal. Using multiphoton microscopy, it is possible to obtain fine images overcoming the problem of strong light scattering of the skin tissue. Reporter transgenic mice that express EYFP under the control of Thy-1 promoter in neurons (including periphery sensory neurons) are well suited for the longitudinal studies of individual nerve endings over extended periods of time up to several months or even life-long. Furthermore, using the same femtosecond laser as for the imaging, it is possible to produce highly selective lesions of nerve fibers for the studies of the nerve fiber restructuring. Here, we present a simple and reliable protocol for longitudinal multiphoton in vivo imaging and laser-based microsurgery on mouse skin nerve endings.

In Vivo Two-Photon Microscopy of Single Nerve Endings in Skin

The protocol for dynamic longitudinal imaging and selective laser lesion of nerve endings in reporter transgenic mice is presented.&#160;

En Vivo De dos fotones microscopía de terminaciones nerviosas individuales en la piel

Nerve endings in skin are involved in physiological processes such as sensing1 as well as in pathological processes such as neuropathic pain2. Their ...

Two-Photon in vivo Imaging of Dendritic Spines in the Mouse Cortex Using a Thinned-skull Preparation

In the mammalian cortex, neurons form extremely complicated networks and exchange information at synapses. Changes in synaptic strength, as well as addition/removal of synapses, occur in an experience-dependent manner, providing the structural foundation of neuronal plasticity. As postsynaptic components of the most excitatory synapses in the cortex, dendritic spines are considered to be a good proxy of synapses. Taking advantages of mouse genetics and fluorescent labeling techniques, individual neurons and their synaptic structures can be labeled in the intact brain. Here we introduce a transcranial imaging protocol using two-photon laser scanning microscopy to follow fluorescently labeled postsynaptic dendritic spines over time in vivo. This protocol utilizes a thinned-skull preparation, which keeps the skull intact and avoids inflammatory effects caused by exposure of the meninges and the cortex. Therefore, images can be acquired immediately after surgery is performed. The experimental procedure can be performed repetitively over various time intervals ranging from hours to years. The application of this preparation can also be expanded to investigate different cortical regions and layers, as well as other cell types, under physiological and pathological conditions.

Two-Photon in vivo Imaging of Dendritic Spines in the Mouse Cortex Using a Thinned-skull Preparation

Time-lapse imaging in the living animal provides valuable information on structural reorganization in the intact brain. Here, we introduce a thinned-skull preparation that allows transcranial imaging of fluorescently labeled synaptic structures in the living mouse cortex by two-photon microscopy.

De dos fotones<em&gt; In vivo</em&gt; Imágenes de las espinas dendríticas en la corteza del ratón Usando un Diluido-cráneo Preparación

In the mammalian cortex, neurons form extremely complicated networks and exchange information at synapses. Changes in synaptic strength, as well as ...

In Vivo Two-photon Imaging of Cortical Neurons in Neonatal Mice

Two-photon imaging is a powerful tool for the in vivo analysis of neuronal circuits in the mammalian brain. However, a limited number of in vivo imaging methods exist for examining the brain tissue of live newborn mammals. Herein we summarize a protocol for imaging individual cortical neurons in living neonatal mice. This protocol includes the following two methodologies: (1) the Supernova system for sparse and bright labeling of cortical neurons in the developing brain, and (2) a surgical procedure for the fragile neonatal skull. This protocol allows the observation of temporal changes of individual cortical neurites during neonatal stages with a high signal-to-noise ratio. Labeled cell-specific gene silencing and knockout can also be achieved by combining the Supernova with RNA interference and CRISPR/Cas9 gene editing systems. This protocol can, thus, be used for analyzing the developmental dynamics of cortical neurons, molecular mechanisms that control the neuronal dynamics, and changes in neuronal dynamics in disease models.

In Vivo Two-photon Imaging of Cortical Neurons in Neonatal Mice

We present an in vivo two-photon imaging protocol for imaging the cerebral cortex of neonatal mice. This method is suitable for analyzing the developmental dynamics of cortical neurons, the molecular mechanisms that control the neuronal dynamics, and the changes in neuronal dynamics in disease models.

En Vivo Proyección de imagen de dos fotones de neuronas corticales en ratones neonatales

Two-photon imaging is a powerful tool for the in vivo analysis of neuronal circuits in the mammalian brain. However, a limited number of in vivo imaging ...

Transpupillary Two-Photon In Vivo Imaging of the Mouse Retina

The retina transforms light signals from the environment into electrical signals that are propagated to the brain. Diseases of the retina are prevalent and cause visual impairment and blindness. Understanding how such diseases progress is critical to formulating new treatments. In vivo&#160;microscopy in animal models of disease is a powerful tool for understanding neurodegeneration and has led to important progress towards treatments of conditions ranging from Alzheimer&#39;s disease to stroke. Given that the retina is the only central nervous system structure inherently accessible by optical approaches, it naturally lends itself towards in vivo imaging. However, the native optics of the lens and cornea present some challenges for effective imaging access.
This protocol outlines methods for in vivo two-photon imaging of cellular cohorts and structures in the mouse retina at cellular resolution, applicable for both acute- and chronic-duration imaging experiments. It presents examples of retinal ganglion cell (RGC), amacrine cell, microglial, and vascular imaging using a suite of labeling techniques including adeno-associated virus (AAV) vectors, transgenic mice, and inorganic dyes. Importantly, these techniques extend to all cell types of the retina, and suggested methods for accessing other cellular populations of interest are described. Also detailed are example strategies for manual image postprocessing for display and quantification. These techniques are directly applicable to studies of retinal function in health and disease.

In vivo imaging is a powerful tool for the study of biology in health and disease. This protocol describes transpupillary imaging of the mouse retina with a standard two-photon microscope. It also demonstrates different in vivoimaging methods to fluorescently label multiple cellular cohorts of the retina.

Imágenes transpupilares de dos fotones in vivo de la retina del ratón

The retina transforms light signals from the environment into electrical signals that are propagated to the brain. Diseases of the retina are prevalent ...

Evaluation and Manipulation of Neural Activity Using Two-Photon Holographic Microscopy

Recent advances in optical bioimaging and optogenetics have enabled the visualization and manipulation of biological phenomena, including cellular activities, in living animals. In the field of neuroscience, detailed neural activity related to brain functions, such as learning and memory, has now been revealed, and it has become feasible to artificially manipulate this activity to express brain functions. However, the conventional evaluation of neural activity by two-photon Ca2+ imaging has the problem of low temporal resolution. In addition, manipulation of neural activity by conventional optogenetics through the optic fiber can only simultaneously regulate the activity of neurons with the same genetic background, making it difficult to control the activity of individual neurons. To solve this issue, we recently developed a microscope with a high spatiotemporal resolution for biological applications by combining optogenetics with digital holographic technology that can modify femtosecond infrared laser beams. Here, we describe protocols for the visualization, evaluation, and manipulation of neural activity, including the preparation of samples and operation of a two-photon holographic microscope (Figure 1). These protocols provide accurate spatiotemporal information on neural activity, which may be useful for elucidating the pathogenesis of neuropsychiatric disorders that lead to abnormalities in neural activity.

We developed a two-photon holographic microscope that can visualize, assess, and manipulate neural activity using high spatiotemporal resolution, with the aim of elucidating the pathogenesis of neuropsychiatric disorders that are associated with abnormal neural activity.

Evaluación y manipulación de la actividad neuronal mediante microscopía holográfica de dos fotones

Recent advances in optical bioimaging and optogenetics have enabled the visualization and manipulation of biological phenomena, including cellular ...

In Vivo Wide-Field and Two-Photon Calcium Imaging from a Mouse Using a Large Cranial Window

Wide-field calcium imaging from the mouse&#39;s neocortex allows one to observe cortex-wide neural activity related to various brain functions. On the other hand, two-photon imaging can resolve the activity of local neural circuits at the single-cell level. It is critical to make a large cranial window to perform multiple-scale analysis using both imaging techniques in the same mouse. To achieve this, one must remove a large section of the skull and cover the exposed cortical surface with transparent materials. Previously, glass skulls and polymer-based cranial windows have been developed for this purpose, but these materials are not easily fabricated. The present protocol describes a simple method for making a large cranial window consisting of commercially available polyvinylidene chloride (PVDC) wrapping film, a transparent silicone plug, and a cover glass. For imaging the dorsal surface of an entire hemisphere, the window size was approximately 6 x 3 mm2. Severe brain vibrations were not observed regardless of such a large window. Importantly, the condition of the brain surface did not deteriorate for more than one month. Wide-field imaging of a mouse expressing a genetically-encoded calcium indicator (GECI), GCaMP6f, specifically in astrocytes, revealed synchronized responses in a few millimeters. Two-photon imaging of the same mouse showed prominent calcium responses in individual astrocytes over several seconds. Furthermore, a thin layer of an adeno-associated virus was applied to the PVDC film and successfully expressed GECI in cortical neurons over the cranial window. This technique is reliable and cost-effective for making a large cranial window and facilitates the investigation of the neural and glial dynamics and their interactions during behavior at the macroscopic and microscopic levels.

In Vivo Wide-Field and Two-Photon Calcium Imaging from a Mouse Using a Large Cranial Window

The present protocol describes making a large (6 x 3 mm2) cranial window using food wrap, transparent silicone, and cover glass. This cranial window allows in vivo wide-field and two-photon calcium imaging experiments in the same mouse.

In vivo Imágenes de calcio de campo amplio y dos fotones de un ratón usando una ventana craneal grande

Wide-field calcium imaging from the mouse&#39;s neocortex allows one to observe cortex-wide neural activity related to various brain functions. On the ...

Seguimiento del comportamiento y patrón de actividad neuronal en el prosencéfalo del pez cebra

Two-Photon Calcium Imaging of Forebrain Activity in Behaving Adult Zebrafish

Adult zebrafish (Danio rerio) exhibit a rich repertoire of behaviors for studying cognitive functions. They also have a miniature brain that can be used for measuring activities across brain regions through optical imaging methods. However, reports on the recording of brain activity in behaving adult zebrafish have been scarce. The present study describes procedures to perform two-photon calcium imaging in the dorsal forebrain of adult zebrafish. We focus on steps to restrain adult zebrafish from moving their heads, which provides stability that enables laser scanning imaging of the brain activity. The head-restrained animals can freely move their body parts and breathe without aids. The procedure aims to shorten the time of head restraint surgery, minimize brain motion, and maximize the number of neurons recorded. A setup for presenting an immersive visual environment during calcium imaging is also described here, which can be used to study neural correlates underlying visually triggered behaviors.

Autor destacado: Avances en la investigación del cerebro del pez cebra adulto 

Here, we present a protocol to perform two-photon calcium imaging in the dorsal forebrain of adult zebrafish.

Imágenes de calcio de dos fotones de la actividad del prosencéfalo en peces cebra adultos que se comportan

Adult zebrafish (Danio rerio) exhibit a rich repertoire of behaviors for studying cognitive functions. They also have a miniature brain that can be used ...