Nous remercions James Perna pour l&#39;illustration graphique. Ce travail a été financé par des subventions de l&#39;Institut national de la santé mentale à YZ

Approbation doit être obtenue à partir d&#39;institutions d&#39;origine avant le début de la chirurgie et de l&#39;étude d&#39;imagerie. Les expériences décrites dans ce manuscrit ont été réalisées en conformité avec les directives et règlements de l&#39;Université de Californie, Santa Cruz institutionnel de protection des animaux et l&#39;utilisation Comité. Chirurgie 1. <ol><li> Autoclave tous les instruments chirurgicaux et stériliser l&#39;espace de travail avec 70% d&#39;alcool bien avant la chirurgie. </li><li> Anesthésier la souris par voie intrapéritonéale (IP) l&#39;injection d&#39;une solution d&#39;anesthésique KX (200 mg / kg de kétamine et 20 mg / kg de xylazine) en fonction du poids corporel de la souris. Remarque: dosage KX peut être ajustée en fonction de la souche, l&#39;âge et l&#39;état de santé des souris. Consultation vétérinaire pour déterminer la dose optimale est également recommandé. </li><li> Effectuer un test de pincement pincée périodiquement en appuyant sur les orteils de la souris et de contrôle pour une réponse réflexe à surveiller l&#39;état de l&#39;anesthésie.Assurez-vous que la souris est totalement anesthésié avant de commencer l&#39;opération. Remarque: Pendant les sessions d&#39;imagerie prolongées, vérifier l&#39;état de l&#39;anesthésie de la souris périodiquement, administrer supplémentaire KX si nécessaire. </li><li> Placer la souris sur un coussin chauffant pour maintenir la température du corps pendant l&#39;intervention chirurgicale. </li><li> Raser la tête de la souris en utilisant une lame de rasoir pour exposer le cuir chevelu. </li><li> Stériliser la zone rasée en essuyant la peau avec une alternance de tampons d&#39;alcool et de la bétadine. Retirez toutes les coupures de cheveux résiduels. </li><li> Appliquez doucement la pommade oculaire à lubrifier les deux yeux, empêchant ainsi des dommages permanents causés par la déshydratation pendant l&#39;expérience. </li><li> Faire une incision droite le long de la ligne médiane du cuir chevelu, et la peau se déplacer latéralement vers les bords du crâne. </li><li> Retirer le tissu conjonctif attaché au crâne. </li></ol> 2. Diluée-crâne Préparation <ol><li> Identifier la région d&#39;imagerie basée sur ster. coordonnées eotaxic Note: Essayez d&#39;éviter les gros vaisseaux sanguins, ce qui pénétration de la lumière de bloc et le flou des structures de représentation. Vasculaire est mieux observée lorsque le crâne est humide avec une solution saline stérile. </li><li> Utilisez le micro forage à grande vitesse à une mince zone circulaire de crâne (diamètre 0,5-1,0 mm). Déplacez le forage parallèle à la surface du crâne, plutôt que de tenir contre le crâne et en appuyant sur. Forage jusqu&#39;à ce que à la fois la couche d&#39;os compact externe et la couche de l&#39;os spongieux milieu sont supprimés. Remarque: Pour éviter les dommages causés par la surchauffe, éviter le contact prolongé entre la foret et le crâne. </li><li> Poursuivre l&#39;amincissement de la couche interne de l&#39;os compact avec une lame de microchirurgie dans le centre de la région amincie de forage. Maintenir la lame de microchirurgie à un angle d&#39;environ 45 ° pour gratter le crâne, sans appuyer contre la boîte crânienne jusqu&#39;à ce qu&#39;une petite région amincie de façon égale (200 à 300 um de diamètre) avec une épaisseur d&#39;environly 20 à 30 pm est obtenu. En raison de l&#39;auto-fluorescence du crâne, l&#39;épaisseur peut être mesurée par le balayage de la distance entre les surfaces supérieure et inférieure de la boîte crânienne dans le cadre du deux photons microscope. Remarque: bien que l&#39;épaisseur du crâne de moins de 20 um assure une bonne qualité de formation d&#39;image, il n&#39;est pas recommandé, car il rend le processus d&#39;amincissement en séances de renouvellement d&#39;imagerie suivants difficile. Pour éviter de l&#39;amincissement, l&#39;épaisseur du crâne doit être vérifiée périodiquement au cours de la chirurgie (voir Discussion). </li></ol> 3. Immobilisation <ol><li> Retirez soigneusement les débris osseux. </li><li> Placer une petite goutte de colle cyanoacrylate sur chaque bord de l&#39;ouverture centrale de la plaque de tête stérile, qui a été stérilisé à l&#39;autoclave (voir figure 1). Maintenez la plaque de tête fermement contre le crâne avec la région amincie situé dans le centre de l&#39;ouverture. Remarque: Si la colle contamine le r amincieégion par accident, retirez-le soigneusement avec la lame de microchirurgie. </li><li> Tirer doucement la peau contre les parois latérales du crâne vers les bords de l&#39;ouverture centrale de la plaque de tête. </li><li> Attendez environ 10 min jusqu&#39;à ce que la plaque de tête est bien fixé sur le crâne. </li><li> Placer la plaque de tête sur deux blocs latéraux de la plaque de maintien, puis serrer les vis sur les bords de la plaque de tête pour immobiliser la souris sur la plaque de maintien (voir la figure 1). Remarque: Assurez-vous qu&#39;il n&#39;y a pas la peau ou les moustaches entre la plaque de tête et les blocs avant de serrer les vis. Une bonne préparation immobilisée doit montrer aucun mouvement observable du crâne sous le microscope de dissection lorsque le dos de l&#39;animal est légèrement tapoté. </li><li> . Rincer le crâne exposé avec une solution saline pour enlever la colle non polymérisée Remarque: Il est important d&#39;enlever tout résidu de colle, de la colle non polymérisée brouille les images et les dommages de microscope objectifs &lt;./ Li&gt; </ol> 4. Imaging <ol><li> Prenez une photo de la vascularisation du crâne exposé avec la région amincie carte 1, qui est utilisé pour déplacer la région imagée dans les séances d&#39;imagerie suivants (voir Figure 2). </li><li> Placer la souris sous le microscope d&#39;imagerie. Localisez la zone amincie sous un objectif d&#39;air 10X en utilisant épifluorescence et déplacer la zone la plus mince au centre de la vue. </li><li> Ajouter une goutte de solution saline sur le sommet du crâne et de passer à l&#39;objectif 60X, qui a été rincé avec de l&#39;eau stérile. Sélectionnez une région où les épines dendritiques individuelles sont clairement visibles le long des dendrites. Identifier et étiqueter la région correspondante sur la carte 1 en comparant vasculaire entre la vue à fluorescence et la photo de la vascularisation. </li><li> Accordez la longueur d&#39;onde de laser à deux photons selon les fluorophores. Par exemple, 920 nm pour la YFP; 890 nm pour la GFP; 1000 nm pour DsRed et tdTomato 24. </li><li> Acquérir des piles d&#39;images avec 2um étapes le long de l&#39;axe z en utilisant l&#39;objectif 60X. Cette pile d&#39;image couvre une zone de 200 x um environ 200 um (512 x 512 pixels) et est utilisée comme carte 2 pour une réinstallation pendant les séances d&#39;imagerie suivants (voir Figure 2). </li><li> Acquérir neuf piles d&#39;images au sein de la carte 2 en utilisant un zoom numérique 3x. Chaque pile d&#39;images couvre une superficie approximative de 70 um x 70 um (512 x 512 pixels), avec 0,7 um étapes le long de la z-axe. Remarque: L&#39;intensité du laser doit être inférieure à 40 mW lorsqu&#39;il est mesuré à des échantillons afin de minimiser la phototoxicité. </li></ol> 5. Recovery <ol><li> Après l&#39;imagerie, détachez la plaque de tête du crâne. </li><li> Nettoyer soigneusement le crâne et la peau pour enlever tous les résidus de colle. Remarque: Tous les résidus de colle sur la peau provoque des irritations et ralentir la cicatrisation de la peau tandis que la colle restante sur le crâne provoque l&#39;érosion du crâne et unengiogenesis dans la couche d&#39;os nouvellement développé, ce qui rend la réinstallation subséquente et la nouvelle image difficile. </li><li> Rincer le crâne et la peau avec une solution saline à plusieurs reprises. </li><li> Suturer le cuir chevelu avec suture chirurgicale stérile. </li><li> Gardez l&#39;animal sur un coussin chauffant dans une cage séparée. Administrer la buprénorphine analgésique (0,1 mg / kg) par voie sous cutanée à atténuer la douleur post-opératoire. Retour à l&#39;animal de la cage d&#39;accueil après guérison complète. Surveillance de l&#39;animal de près (vérifier au moins une fois par jour) jusqu&#39;à ce que l&#39;incision est guéri et les sutures sont enlevés. Administrer des injections ultérieures de la buprénorphine analgésique si nécessaire. </li></ol> 6. Recréation d&#39;image <ol><li> Répétez les étapes 1.1 à 1.8. </li><li> Répétez les étapes 3.1 à 3.6 </li><li> Localiser région précédemment imagée en comparant le modèle du système vasculaire à la carte 1 et le motif de branche dendritique à la carte 2. </li><li> Si réimagerie est réalisée dans 1 semaine, répétez l&#39;étape 2.3 pour enlever la fine couche d&#39;os nouvellement augmenté au-dessus de la re amincierégion en utilisant la lame de microchirurgie. Si réimagerie est effectué après plus de 1 semaine, répétez les étapes deux 2.2 et 2.3. Remarque: La couche d&#39;os nouvellement développé se compose d&#39;une structure moins condensée par rapport à la couche d&#39;os compact original, entraînant une réduction de la qualité de l&#39;image. Par conséquent, pour acquérir la même qualité, il est nécessaire de diluer le crâne un peu plus de la session de formation d&#39;image précédente. </li><li> Ajustez la position et l&#39;orientation d&#39;obtenir des piles d&#39;images qui correspondent déjà pris des piles d&#39;images au microscope à deux photons. </li><li> Acquérir les images comme dans l&#39;étape 4.6. </li><li> Répétez les étapes 5.1 à 5.5 après l&#39;imagerie. </li></ol>

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Les auteurs déclarent qu&#39;ils n&#39;ont aucun intérêt financier concurrents.

Pour obtenir une préparation-de crâne amincie succès, plusieurs étapes de ce protocole sont cruciales. 1) L&#39;épaisseur de la boîte crânienne. L&#39;os crânien a une structure en sandwich, avec deux couches de haute densité osseuse compacte et une couche intermédiaire de faible densité de l&#39;os spongieux. Bien que le micro-foret à haute vitesse est adapté pour enlever les couches externes de l&#39;os compact et l&#39;os spongieux, la lame de microchirurgie est idéal pour l&#39;amincissement de la couc...

Le cortex des mammifères participe à de nombreuses fonctions du cerveau, de la perception sensorielle et contrôle des déplacements à l&#39;abstrait traitement de l&#39;information et de la cognition. Diverses fonctions corticales s&#39;appuient sur différents circuits neuronaux, qui sont constitués de différents types de neurones qui communiquent et échangent des informations au niveau des synapses individuelles. La structure et la fonction des synapses sont constamment modifiés en réponse à des expériences et des pathologies. Dans le cerveau mature, la plasticité synaptique prend la forme de deux changements de résistance et ajout / suppression de synapses, jouant un rôle important dans la formation et l&#39;entretien d&#39;un circuit neuronal fonctionnel. Épines dendritiques sont les composantes post-synaptiques de la plupart des synapses excitatrices dans le cerveau des mammifères. Le chiffre d&#39;affaires constant et les changements morphologiques des épines sont censées servir comme un bon indicateur de modifications dans les connexions synaptiques 1-7. Biphotonique à balayage laser microscopie offre pénétration profonde à travers épaisses, préparations opaques et faible phototoxicité, qui le rend approprié pour l&#39;imagerie en direct dans le cerveau intact 8. En combinaison avec un marquage fluorescent, l&#39;imagerie à deux photons fournit un outil puissant pour jeter un regard dans le cerveau vivant et suivez réorganisation structurelle au niveau des synapses individuelles à haute résolution spatiale et temporelle. Divers procédés ont été utilisés pour préparer des souris pour l&#39;imagerie en temps réel 9-13. Ici, nous décrivons une préparation-crâne amincie de l&#39;imagerie in vivo à deux photons pour étudier la plasticité structurale des épines dendritiques post-synaptiques dans le cortex de la souris. En utilisant cette approche, nos études récentes ont représenté une image dynamique de l&#39;évolution de la colonne vertébrale dendritiques en réponse à moteur compétence apprentissage Avec la disponibilité croissante des animaux transgéniques avec des sous-ensembles de neurones marqués par fluorescence et le développement rapide des techniques in vivo dans l&#39;étiquetage, les procédures similaires à ceux décrits ici peuvent également être appliqués à enquêted&#39;autres types de cellules et de te régions corticales, combinés à d&#39;autres manipulations, ainsi que utilisé dans les modèles de la maladie 16-23.

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		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Ketamine</td>
			<td style="width:181px;">Bioniche Pharma</td>
			<td style="width:108px;">67457-034-10</td>
			<td style="width:775px;">Mixed with xylazine for anesthesia</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Xylazine</td>
			<td style="width:181px;">Lloyd laboratories</td>
			<td style="width:108px;">139-236</td>
			<td>Mixed with ketamine for anesthesia</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Saline</td>
			<td style="width:181px;">Hospira</td>
			<td style="width:108px;">0409-7983-09</td>
			<td>0.9% NaCl for injection and imaging</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:189px;">Razor blades</td>
			<td style="width:181px;">Electron microscopy sciences</td>
			<td style="width:108px;">72000</td>
			<td>Double-edge stainless steel razor blades</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Alcohol pads</td>
			<td style="width:181px;">Fisher Scientific</td>
			<td style="width:108px;">06-669-62</td>
			<td>Sterile alcohol prep pads</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Eye ointment</td>
			<td style="width:181px;">Henry Schein</td>
			<td style="width:108px;">102-9470</td>
			<td>Petrolatum ophthalmic ointment sterile ocular lubricant</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:189px;">High-speed micro drill</td>
			<td style="width:181px;">Fine Science Tools</td>
			<td style="width:108px;">18000-17</td>
			<td>The high-speed micro drill is suitable for thinning the outer layer of compact bone and targeting a small area</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Micro drill steel burrs</td>
			<td style="width:181px;">Fine Science Tools</td>
			<td style="width:108px;">19007-14</td>
			<td>1.4 mm diameter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Microsurgical blade</td>
			<td style="width:181px;">Surgistar</td>
			<td style="width:108px;">6961</td>
			<td>The microsurgical blade is suitable for thinning the inner layer of compact bone and middler layer of spongy bone</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Cyanoacrylate glue</td>
			<td style="width:181px;">Fisher Scientific</td>
			<td style="width:108px;">NC9062131</td>
			<td>Fix the head plate onto the skull</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Suture</td>
			<td style="width:181px;">Havard Apparatus</td>
			<td style="width:108px;">510461</td>
			<td>Non-absorbale, sterile silk suture, 6-0 monofilament</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Dissecting microscope</td>
			<td>Olympus</td>
			<td style="width:108px;"></td>
			<td>SZ61</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">CCD camera</td>
			<td>Infinity</td>
			<td style="width:108px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Two-photon microscope</td>
			<td style="width:181px;">Prairie Technologies</td>
			<td style="width:108px;"></td>
			<td style="width:775px;">Ultima IV</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">10X objective</td>
			<td style="width:181px;">Olympus</td>
			<td style="width:108px;"></td>
			<td>NA 0.30, air</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">60X objective</td>
			<td style="width:181px;">Olympus</td>
			<td style="width:108px;"></td>
			<td>NA 1.1, IR permeable, water immersion</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:189px;">Ti-sapphire laser</td>
			<td style="width:181px;">Spectra-Physics</td>
			<td style="width:108px;"></td>
			<td>Mai Tai HP</td>
		</tr>
	</tbody>
</table>

two-photon in vivo imaging of dendritic spines in the mouse cortex using a thinned-skull preparation

Dans le cortex des mammifères, les neurones forment des réseaux très complexes et l&#39;échange d&#39;informations au niveau des synapses. Changements dans la force synaptique, ainsi que l&#39;ajout / suppression de synapses, se produisent d&#39;une manière dépendant de l&#39;expérience, fournissant la base structurelle de la plasticité neuronale. Comme composants post-synaptiques des synapses excitateurs plus dans le cortex, épines dendritiques sont considérées comme un bon indicateur de synapses. Prendre avantages de la génétique de la souris et des techniques de marquage par fluorescence, des neurones et de leurs structures synaptiques peuvent être marqués dans le cerveau intact. Ici, nous introduisons un protocole d&#39;imagerie transcrânienne utilisant deux photons microscopie à balayage laser à suivre épines dendritiques post-synaptiques marquées par fluorescence dans le temps in vivo. Ce protocole utilise une préparation-crâne amincie, ce qui maintient intact le crâne et évite les effets inflammatoires causées par l&#39;exposition des méninges et le cortex. Par conséquent, les images peuvent être acquises immédiatement après surgery est effectuée. La procédure expérimentale peut être effectuée de manière répétitive au cours de différents intervalles de temps allant de quelques heures à plusieurs années. L&#39;application de cette préparation peut également être étendu pour étudier différentes régions et couches corticales, ainsi que d&#39;autres types de cellules, dans des conditions physiologiques et pathologiques.

Dans YFP-H ligne 25 souris, la protéine fluorescente jaune exprime dans un sous-ensemble de neurones pyramidaux couche V, qui font saillie de leurs dendrites apicales pour les couches superficielles du cortex. Grâce à la préparation-crâne amincie, les segments dendritiques marquées par fluorescence peuvent être répétitive imagées sous microscope à deux photons sur différents intervalles d&#39;imagerie, allant de quelques heures à plusieurs mois. Ici, nous montrons un exemple de formation d&#39;im...

Watch this Scientific Journal Video about Two-Photon in vivo Imaging of Dendritic Spines in the Mouse Cortex Using a Thinned-skull Preparation at JoVE.com

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.

Deux-Photon<em&gt; In vivo</em&gt; Imagerie des épines dendritiques dans le cortex de souris utilisant un crâne-Diluée Préparation

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

two-photon-vivo-imaging-dendritic-spines-mouse-cortex-using-thinned

Research

JoVE Journal

Neuroscience

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

17.8K vues.  University of California, Santa Cruz. 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.

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

Chronic Imaging of Mouse Visual Cortex Using a Thinned-skull Preparation

In vivo imaging using two-photon laser scanning microscopy (2PLSM) allows the study of living cells and neuronal processes in the intact brain. The technique presented here allows the imaging of the same area of the brain at several time points (chronic imaging) with microscopic resolution allowing the tracking of dendritic spines which are the small structures that represent the majority of postsynaptic excitatory sites in the CNS. The ability to clearly resolve fine cortical structures over several time points has many advantages, specifically in the study of brain plasticity in which morphological changes at synapses and circuit remodeling may help explain underlying mechanisms. In this video and supplementary material, we show a protocol for chronic in vivo imaging of the intact brain using a thinned-skull preparation. The thinned-skull preparation is a minimally invasive approach, which avoids potential damage to the dura and/or cortex, thus reducing the onset of an inflammatory response. When this protocol is performed correctly, it is possible to clearly monitor changes in dendritic spine characteristics in the intact brain over a prolonged period of time.

In this video and supplemental material, we show a protocol for chronic in vivo imaging of the intact brain using a thinned-skull preparation.

Imagerie chronique des souris cortex visuel en utilisant une préparation Diluée-crâne

In vivo imaging using two-photon laser scanning microscopy (2PLSM) allows the study of living cells and neuronal processes in the intact brain. The ...

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Neurosciences

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.

Dans l&#39;imagerie in vivo de la moelle épinière de souris utilisant microscopie à deux photons

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 ...

Detection of Microregional Hypoxia in Mouse Cerebral Cortex by Two-photon Imaging of Endogenous NADH Fluorescence

The brain's ability to function at high levels of metabolic demand depends on continuous oxygen supply through blood flow and tissue oxygen diffusion. Here we present a visualized experimental and methodological protocol to directly visualize microregional tissue hypoxia and to infer perivascular oxygen gradients in the mouse cortex. It is based on the non-linear relationship between nicotinamide adenine dinucleotide (NADH) endogenous fluorescence intensity and oxygen partial pressure in the tissue, where observed tissue NADH fluorescence abruptly increases at tissue oxygen levels below 10 mmHg1. We use two-photon excitation at 740 nm which allows for concurrent excitation of intrinsic NADH tissue fluorescence and blood plasma contrasted with Texas-Red dextran. The advantages of this method over existing approaches include the following: it takes advantage of an intrinsic tissue signal and can be performed using standard two-photon in vivo imaging equipment; it permits continuous monitoring in the whole field of view with a depth resolution of ~50 &mu;m. We demonstrate that brain tissue areas furthest from cerebral blood vessels correspond to vulnerable watershed areas which are the first to become functionally hypoxic following a decline in vascular oxygen supply. This method allows one to image microregional cortical oxygenation and is therefore useful for examining the role of inadequate or restricted tissue oxygen supply in neurovascular diseases and stroke.

Here we describe a method to directly visualize microregional tissue hypoxia in the mouse cortex in vivo. It is based on concurrent two-photon imaging of nicotinamide adenine dinucleotide (NADH) and the cortical microcirculation. This method is useful for high resolution analysis of tissue oxygen supply.

La détection de l&#39;hypoxie dans le cortex de souris microrégionale cérébrale par imagerie à deux photons de fluorescence endogène NADH

The brain's ability to function at high levels of metabolic demand depends on continuous oxygen supply through blood flow and tissue oxygen diffusion. ...

A Polished and Reinforced Thinned-skull Window for Long-term Imaging of the Mouse Brain

In vivo imaging of cortical function requires optical access to the brain without disruption of the intracranial environment. We present a method to form a polished and reinforced thinned skull (PoRTS) window in the mouse skull that spans several millimeters in diameter and is stable for months. The skull is thinned to 10 to 15 &mu;m in thickness with a hand held drill to achieve optical clarity, and is then overlaid with cyanoacrylate glue and a cover glass to: 1) provide rigidity, 2) inhibit bone regrowth and 3) reduce light scattering from irregularities on the bone surface. Since the skull is not breached, any inflammation that could affect the process being studied is greatly reduced. Imaging depths of up to 250 &mu;m below the cortical surface can be achieved using two-photon laser scanning microscopy. This window is well suited to study cerebral blood flow and cellular function in both anesthetized and awake preparations. It further offers the opportunity to manipulate cell activity using optogenetics or to disrupt blood flow in targeted vessels by irradiation of circulating photosensitizers.

We present a method to form an imaging window in the mouse skull that spans millimeters and is stable for months without inflammation of the brain. This method is well suited for longitudinal studies of blood flow, cellular dynamics, and cell/vascular structure using two-photon microscopy.

Une poli et renforcé Diluée-crâne fenêtre for Long-term imagerie du cerveau de souris

In vivo imaging of cortical function requires optical access to the brain without disruption of the intracranial environment. We present a method to form ...

Visualization and Genetic Manipulation of Dendrites and Spines in the Mouse Cerebral Cortex and Hippocampus using In utero Electroporation

In utero electroporation (IUE) has become a powerful technique to study the development of different regions of the embryonic nervous system 1-5. To date this tool has been widely used to study the regulation of cellular proliferation, differentiation and neuronal migration especially in the developing cerebral cortex 6-8. Here we detail our protocol to electroporate in utero the cerebral cortex and the hippocampus and provide evidence that this approach can be used to study dendrites and spines in these two cerebral regions.
Visualization and manipulation of neurons in primary cultures have contributed to a better understanding of the processes involved in dendrite, spine and synapse development. However neurons growing in vitro are not exposed to all the physiological cues that can affect dendrite and/or spine formation and maintenance during normal development. Our knowledge of dendrite and spine structures in vivo in wild-type or mutant mice comes mostly from observations using the Golgi-Cox method 9. However, Golgi staining is considered to be unpredictable. Indeed, groups of nerve cells and fiber tracts are labeled randomly, with particular areas often appearing completely stained while adjacent areas are devoid of staining. Recent studies have shown that IUE of fluorescent constructs represents an attractive alternative method to study dendrites, spines as well as synapses in mutant / wild-type mice 10-11 (Figure 1A). Moreover in comparison to the generation of mouse knockouts, IUE represents a rapid approach to perform gain and loss of function studies in specific population of cells during a specific time window. In addition, IUE has been successfully used with inducible gene expression or inducible RNAi approaches to refine the temporal control over the expression of a gene or shRNA 12. These advantages of IUE have thus opened new dimensions to study the effect of gene expression/suppression on dendrites and spines not only in specific cerebral structures (Figure 1B) but also at a specific time point of development (Figure 1C).
Finally, IUE provides a useful tool to identify functional interactions between genes involved in dendrite, spine and/or synapse development. Indeed, in contrast to other gene transfer methods such as virus, it is straightforward to combine multiple RNAi or transgenes in the same population of cells. 
In summary, IUE is a powerful method that has already contributed to the characterization of molecular mechanisms underlying brain function and disease and it should also be useful in the study of dendrites and spines.

Visualization and Genetic Manipulation of Dendrites and Spines in the Mouse Cerebral Cortex and Hippocampus using In utero Electroporation

This article describes in detail a protocol to electroporate in utero the cerebral cortex and the hippocampus at E14.5 in mice. We also show that this is a valuable method to study dendrites and spines in these two cerebral regions.

Visualisation et la manipulation génétique des dendrites et des épines dans le cortex cérébral et l&#39;hippocampe de souris à l&#39;aide<em&gt; In utero</em&gt; Électroporation

In utero electroporation (IUE) has become a powerful technique to study the development of different regions of the embryonic nervous system 1-5. To date ...

Thinned-skull Cortical Window Technique for In Vivo Optical Coherence Tomography Imaging

Optical coherence tomography (OCT) is a biomedical imaging technique with high spatial-temporal resolution. With its minimally invasive approach OCT has been used extensively in ophthalmology, dermatology, and gastroenterology1-3. Using a thinned-skull cortical window (TSCW), we employ spectral-domain OCT (SD-OCT) modality as a tool to image the cortex in vivo. Commonly, an opened-skull has been used for neuro-imaging as it provides more versatility, however, a TSCW approach is less invasive and is an effective mean for long term imaging in neuropathology studies. Here, we present a method of creating a TSCW in a mouse model for in vivo OCT imaging of the cerebral cortex.

Thinned-skull Cortical Window Technique for In Vivo Optical Coherence Tomography Imaging

We present a method of creating a thinned-skull cortical window (TSCW) in a mouse model for in vivo OCT imaging of the cerebral cortex.

Diluée-skull Technique fenêtre corticale pour<em&gt; In Vivo</em&gt; Tomographie par cohérence optique d&#39;imagerie

Optical coherence tomography (OCT) is a biomedical imaging technique  with high spatial-temporal resolution. With its minimally invasive approach OCT  has ...

In Vivo Two-photon Imaging Of Experience-dependent Molecular Changes In Cortical Neurons

The brain's ability to change in response to experience is essential for healthy brain function, and abnormalities in this process contribute to a variety of brain disorders1,2. To better understand the mechanisms by which brain circuits react to an animal's experience requires the ability to monitor the experience-dependent molecular changes in a given set of neurons, over a prolonged period of time, in the live animal. While experience and associated neural activity is known to trigger gene expression changes in neurons1,2, most of the methods to detect such changes do not allow repeated observation of the same neurons over multiple days or do not have sufficient resolution to observe individual neurons3,4. Here, we describe a method that combines in vivo two-photon microscopy with a genetically encoded fluorescent reporter to track experience-dependent gene expression changes in individual cortical neurons over the course of day-to-day experience. 
One of the well-established experience-dependent genes is Activity-regulated cytoskeletal associated protein (Arc)5,6. The transcription of Arc is rapidly and highly induced by intensified neuronal activity3, and its protein product regulates the endocytosis of glutamate receptors and long-term synaptic plasticity7. The expression of Arc has been widely used as a molecular marker to map neuronal circuits involved in specific behaviors3. In most of those studies, Arc expression was detected by in situ hybridization or immunohistochemistry in fixed brain sections. Although those methods revealed that the expression of Arc was localized to a subset of excitatory neurons after behavioral experience, how the cellular patterns of Arc expression might change with multiple episodes of repeated or distinctive experiences over days was not investigated. 
In vivo two-photon microscopy offers a powerful way to examine experience-dependent cellular changes in the living brain8,9. To enable the examination of Arc expression in live neurons by two-photon microscopy, we previously generated a knock-in mouse line in which a GFP reporter is placed under the control of the endogenous Arc promoter10. This protocol describes the surgical preparations and imaging procedures for tracking experience-dependent Arc-GFP expression patterns in neuronal ensembles in the live animal. In this method, chronic cranial windows were first implanted in Arc-GFP mice over the cortical regions of interest. Those animals were then repeatedly imaged by two-photon microscopy after desired behavioral paradigms over the course of several days. This method may be generally applicable to animals carrying other fluorescent reporters of experience-dependent molecular changes4.

In Vivo Two-photon Imaging Of Experience-dependent Molecular Changes In Cortical Neurons

Experience-dependent molecular changes in neurons are essential for the brain's ability to adapt in response to behavioral challenges. An in vivo two-photon imaging method is described here that allows the tracking of such molecular changes in individual cortical neurons through genetically encoded reporters.

In Vivo Imagerie biphotonique d&#39;expérience qui dépendent des changements moléculaires dans les neurones corticaux

The brain's ability to change in response to experience is essential for healthy brain function, and abnormalities in this process contribute to a variety ...

Fast Micro-iontophoresis of Glutamate and GABA: A Useful Tool to Investigate Synaptic Integration

One of the fundamental interests in neuroscience is to understand the integration of excitatory and inhibitory inputs along the very complex structure of the dendritic tree, which eventually leads to neuronal output of action potentials at the axon. The influence of diverse spatial and temporal parameters of specific synaptic input on neuronal output is currently under investigation, e.g. the distance-dependent attenuation of dendritic inputs, the location-dependent interaction of spatially segregated inputs, the influence of GABAergig inhibition on excitatory integration, linear and non-linear integration modes, and many more.
With fast micro-iontophoresis of glutamate and GABA it is possible to precisely investigate the spatial and temporal integration of glutamatergic excitation and GABAergic inhibition. Critical technical requirements are either a triggered fluorescent lamp, light-emitting diode (LED), or a two-photon scanning microscope to visualize dendritic branches without introducing significant photo-damage of the tissue. Furthermore, it is very important to have a micro-iontophoresis amplifier that allows for fast capacitance compensation of high resistance pipettes. Another crucial point is that no transmitter is involuntarily released by the pipette during the experiment.
Once established, this technique will give reliable and reproducible signals with a high neurotransmitter and location specificity. Compared to glutamate and GABA uncaging, fast iontophoresis allows using both transmitters at the same time but at very distant locations without limitation to the field of view. There are also advantages compared to focal electrical stimulation of axons: with micro-iontophoresis the location of the input site is definitely known and it is sure that only the neurotransmitter of interest is released. However it has to be considered that with micro-iontophoresis only the postsynapse is activated and presynaptic aspects of neurotransmitter release are not resolved. In this article we demonstrate how to set up micro-iontophoresis in brain slice experiments.

In this article we introduce fast micro-iontophoresis of neurotransmitters as a technique to investigate integration of postsynaptic signals with high spatial and temporal precision.

Rapide Micro-iontophorèse de glutamate et le GABA: un outil utile d&#39;étudier l&#39;intégration synaptique

One of the fundamental interests in neuroscience is to understand the integration of excitatory and inhibitory inputs along the very complex structure of ...

Two-photon Imaging of Cellular Dynamics in the Mouse Spinal Cord

Two-photon (2P) microscopy is utilized to reveal cellular dynamics and interactions deep within living, intact tissues. Here, we present a method for live-cell imaging in the murine spinal cord. This technique is uniquely suited to analyze neural precursor cell (NPC) dynamics following transplantation into spinal cords undergoing neuroinflammatory demyelinating disorders. NPCs migrate to sites of axonal damage, proliferate, differentiate into oligodendrocytes, and participate in direct remyelination. NPCs are thereby a promising therapeutic treatment to ameliorate chronic demyelinating diseases. Because transplanted NPCs migrate to the damaged areas on the ventral side of the spinal cord, traditional intravital 2P imaging is impossible, and only information on static interactions was previously available using histochemical staining approaches. Although this method was generated to image transplanted NPCs in the ventral spinal cord, it can be applied to numerous studies of transplanted and endogenous cells throughout the entire spinal cord. In this article, we demonstrate the preparation and imaging of a spinal cord with enhanced yellow fluorescent protein-expressing axons and enhanced green fluorescent protein-expressing transplanted NPCs.

A new ex vivo preparation for imaging the mouse spinal cord. This protocol allows for two-photon imaging of live cellular interactions throughout the spinal cord.

Deux photons Imaging of Cellular Dynamics dans la moelle épinière de souris

Two-photon (2P) microscopy is utilized to reveal cellular dynamics and interactions deep within living, intact tissues. Here, we present a method for ...

Simultaneous Two-photon In Vivo Imaging of Synaptic Inputs and Postsynaptic Targets in the Mouse Retrosplenial Cortex

This video shows the craniotomy procedure that allows chronic imaging of neurons in the mouse retrosplenial cortex (RSC) using in vivo two-photon microscopy in Thy1-GFP transgenic mouse line. This approach creates a possibility to investigate the correlation of behavioural manipulations with changes in neuronal morphology in vivo.
The cranial window implantation procedure was considered to be limited only to the easily accessible cortex regions such as the barrel field. Our approach allows visualization of neurons in the highly vascularized RSC. RSC is an important element of the brain circuit responsible for spatial memory, previously deemed to be problematic for in vivo two-photon imaging.
The cranial window implantation over the RSC is combined with an injection of mCherry-expressing recombinant adeno-associated virus (rAAVmCherry) into the dorsal hippocampus. The expressed mCherry spreads out to axonal projections from the hippocampus to RSC, enabling the visualization of changes in both presynaptic axonal boutons and postsynaptic dendritic spines in the cortex. 
This technique allows long-term monitoring of experience-dependent structural plasticity in RSC.

Simultaneous Two-photon In Vivo Imaging of Synaptic Inputs and Postsynaptic Targets in the Mouse Retrosplenial Cortex

This video shows the craniotomy procedure that allows chronic imaging of neurons in mouse retrosplenial cortex using in vivo two photon microscopy in Thy1-GFP transgenic line. This approach is combined with injection of mCherry-expressing adeno-associated virus into dorsal hippocampus. These techniques allow long-term monitoring of experience-dependent structural plasticity in RSC.