Finanzierung: Diese Arbeit wurde durch eine Stiftung Bertarelli Zuschuss (DJL), einem MED-EL Zuschuss (DJL) und ein National Institutes of Health Grants DC01089 (MCB) unterstützt.

HINWEIS: Alle experimentellen Verfahren sind in Übereinstimmung mit dem Animal Care und Verwenden Ausschuss der Massachusetts Eye and Ear Infirmary und der Harvard Medical School, die nationalen Tierpflege Richtlinien befolgen, einschließlich Public Health Service Politik über humane Pflege und Verwendung von Labortieren, die durchgeführt ILAR Guide, und das Tierschutzgesetz. Experimentelle Verfahren nachstehend im Detail Exposition der linken DCN aufgeführt. Verwenden Sie sterile Instrumente während der Durchführung Überleben Chirurgie. 1. Primär Kraniotomie und Rücken Cochlear Nucleus Belichtungs <ol><li> Anästhesie <ol><li> Anesthetize einer Maus im Alter von 8-12 Wochen mit einem Gewicht von 18-24 g, Xylazin 20 mg / kg Ketamin 100 mg / kg über eine intraperitoneale Verabreichung. Überprüfen Sie die Anästhesie durch die Überwachung der Herzfrequenz, Atemfrequenz, sowie toe Prise Rückzug Reflex. Platz Tierarzt Salbe auf die Augen bis zur Trockenheit während der Narkose zu verhindern. Sobald ausreichend unter Narkose, Rasur Haarüberlagert ter Kopfhaut, um ungehinderten Zugang zu der Operationsstelle zu schaffen. </li></ol></li><li> Chirurgische Positionierung <ol><li> Platzieren Sie die Maus sicher in einer Kleintierstereotaktischen Halterung, an Ort und Stelle durch eine Schnauze Klammer gehalten. </li><li> Stellen Sie sicher, dass die Schnauze Klemme locker genug, um für eine ausreichende Atmung aber fest genug, lassen den Kopf der Maus vollständig zu immobilisieren. Wenn die Maus den Kopf locker ist, ist das Tier wahrscheinlich während der Kraniotomie Teil der Verfahren des Kopfhalters fallen. </li><li> Zeigen auditorischen Hirnstamm-Implantat Elektroden in üblicher Weise, die für die Überwachung der Herzfrequenz ermöglicht. Die Atemfrequenz sollte durch Visualisierung überwacht werden. Beachten Sie, dass die normale Herzfrequenz und die Atemfrequenz wird in Abhängigkeit vom Alter des Maus variieren. </li><li> Ein Thermometer ist auf einer homeothermic Heizdecke platziert und über die Platzierung euthermia gewährleistet ist. </li></ol></li><li> Hautschnitt und Exposition der interparietal und occipital Knochen des Schädels <ol><li> Unter einem Microscopa, stellen ein vertikaler Schnitt durch die Haut ausgehend von der Mittellinie, direkt zwischen der Ohrmuschel und sich bis zum Schwanzteil des Hinterhauptbein. Nach der Mittellinie Hautschnitt, verdrängen die Haut seitlich. Visualisieren Sie die Muskeln für den verließ den hinteren Teil des Schädels. </li><li> Entfernen Muskel über dem linken Scheitel, interparietal und occipital Knochen des Schädels durch Exartikulation der Muskelansätze an ihre jeweiligen Knochen mit einem Skalpell oder Iris Schere. Beachten Sie ein kleines Maß an Blutungen entlang der Schnittmuskel Kanten. Minimieren Sie dies durch sanften Druck mit einem Wattestäbchen für 10-15 Sek. </li></ol></li><li> Kraniotomie darüberliegenden Cochlear Nucleus <ol><li> Identifizieren Sie relevanten Nahtlinien, einschließlich sagittalen und Lambdanähte Linien (Abbildung 1, links). </li><li> Mit Rongeure, machen Sie eine Kraniotomie über die Inkabein, links von der Mittellinie, ~ 2 mm kaudal der Lambda-Naht. Diese Region liegt über dem DCN. </li><li> Following Kraniotomie, beachten Sie eine dünne Schicht der Dura, die das Kleinhirn überlagert. Mit einem Skalpell, entfernen Sie die Dura. (Bild 1, Mitte). HINWEIS: Das Entfernen der Dura kann ein kleines Maß an Blutungen. Dieses Verfahren der Verwendung der Skalpellklinge, um die Dura zu entfernen, ist beabsichtigt, um die Menge des Blutverlustes während der Cerebellum Aspiration, die auf der Hirnoberfläche und undurchsichtig Identifizierung des DCN Pool wird reduzieren. Gesamtblutvolumen von Maus ist ~ 1,5 ml nicht überschreiten soll&gt; als 15%. Wenn die Blutung diesen Betrag übersteigt, sollte die Maus mit mit Flüssigkeit Ergänzung zur Verfügung gestellt werden. </li><li> Entfernen geronnenem Blut überlagert das Kleinhirn mit dem Wattestäbchen. Optional sanft tropfen Kochsalzlösung mit einem Zahnpunkt auf das Kleinhirn, um Blut zu Blut entfernt. </li></ol></li><li> Kleinhirn-Aspiration <ol><li> Verwendung eines 5 Französisch Saug absaugen seitlichen äußersten Abschnitt der linken Cerebellum über der DCN bis der DCN visBuchs (Abbildung 1, rechts). Entfernen etwa 1/4 bis 1/3 des linken Kleinhirn. Das Wahrzeichen neben dem DCN ist die Ampulle des oberen Bogenganges. HINWEIS: Aspiration des Kleinhirns ist der entscheidende Schritt des Protokolls. Gerichtete Streben des Cerebellum meisten erfolgreich durchgeführt, wenn es in einem einzigen Versuch auftritt und nicht mit Mehrfachdurchgänge des Saug da dies zu Blutungen führen. In Ansaugen zu unterstützen, setzen die Brennebene des Mikroskops an der erwarteten Tiefe des CN, die geringfügig distal der Oberfläche der Kleinhirn wird. Einstellen der Brennebene mit dem CN wird Visualisierung verbessern und ein scharfes Bild. </li><li> Nach Aspiration, weitere Blutungen, Liquor (CSF) Aufbau und Kleinhirn Verschiebung auf der DCN erwartet. Vermitteln 0,5 cc steriler Kochsalzlösung schnell in die Kraniotomie Blutgerinnung verhindern. Eine Kombination aus sanften Abtupfen mit einem Zahnpunkt und Absaugung kann dannverwendet, um abzuräumen einen Weg für die direkte Visualisierung des DCN. Nicht direkt an die Oberfläche des DCN. </li></ol></li></ol> 2. Druckmikroinjektion für Virus-vermittelte Gentransfer und chirurgische Wiederherstellung <ol><li> Nachdem der DCN ist frei von überlagernden Blut und CSF und ist deutlich sichtbar, machen Druck Mikroinjektionen in das DCN mit einem 10 &amp; mgr; l Hamilton-Spritze über einen Zeitraum 2 min. </li><li> Einführung der Nadel mit einem Mikromanipulator, bis die Spitze nicht mehr unter der Oberfläche des DCN sichtbar. </li><li> Für eine optimale Leistung verwenden Sie eine 33 oder 34 Gauge-Nadel (verwenden Sie eine gasdichte Spritze mit der 34-Gauge-Nadel) mit einem flachen Kegel, wie 45 °, um stumpfes Trauma zu minimieren und zu lokalisieren, das Injektionsvolumen im DCN, der ein dünner ist und seichten Hirnstruktur (&lt;300 &amp; mgr; m dick). Hinweis: andere Mikroinjektionsinstrumente genutzt basieren. Idealerweise sollte die Injektions Instrument flexibel sein, um für einige geringfügige ben ermöglichend, wenn nötig, direkt gezielt die DCN. Ferner ist, wie die Maus bewegt sich geringfügig, während des gesamten Verfahrens durch die Atmung, sollte das Gerät robust genug sein, um geringe Mengen an Bewegung zu widerstehen. </li></ol> 3. Chirurgische Wieder <ol><li> Unmittelbar nach der Injektion wieder anzunähern, die Haut und lassen Sie die Maus, um per Standard Recovery-Verfahren zu erholen. Verbleibende Cerebellum und Narbengewebe in den Hohlraum durch Absaugen des Kleinhirns verursacht füllen. Ständig Tiere zu überwachen, bis genügend Bewusstsein wiedererlangt, um Brustlage zu halten. Überwachen Sie Herzfrequenz, Atemfrequenz, sowie die Fähigkeit zu ernähren. HINWEIS: Kein Tier, das einer Operation unterzogen wurde, wird in einen Käfig mit anderen Tieren zurückgegeben, bis vollständig erholt. </li><li> Wenn eine Maus fängt an, im Kreis nach der Operation zu gehen (&lt;5% der Fälle), in der Regel 2-4 Stunden nach der Schließung der Hautschnitt, sofort opfern Sie die Maus, wie es würde wahrscheinlich eine schwierige Zeit Fütterung. Tseine Nebeneffekt ist durch Aspiration des Kleinhirns wahrscheinlich. Das Tier sollte bei Schmerzen nach der Operation überwacht und entsprechende Betäubungsmittel sollte der besseren Tier Komfort auf Grund institutioneller Normen werden. Antibiotika kann notwendig sein, wenn Anzeichen einer Infektion. </li></ol> 4. Sekundäre Kraniotomie und Cochlear Nucleus Belichtungs <ol><li> Nach 2-4 Wochen der Heilung und virusvermittelten Gentransfer Inkubation erneut anästhesiert eine vorher injizierten Maus und Schritt 1,1-1,5 optimale Inkubationszeit hängt von der Art des Gens überführt. </li><li> Entfernen Narbengewebe über die Kraniotomiestelle durch eine Kombination von Pinzette, Skalpell und Knochenzangen. </li><li> Nach der Visualisierung der Kraniotomie, identifizieren eine Kombination aus Rest über der DCN Kleinhirn und Narbengewebe. Verwenden Sie einen 5 Französisch Ansaugen darüber liegenden Kleinhirn / Narbengewebe (ähnlich wie das vorherige Kleinhirn Aspiration) anzusaugen. </li><li> Nach Aspiration, erwarten weitere Blutungen, CSF build-up, und die verbleibenden Bits des Kleinhirns. Schnell einzuführen Salzlösung in die Kraniotomie, um die Blutgerinnung zu verhindern. Verwenden Sie eine Kombination aus sanften Zahnpunkt Abtupfen und Absaugung, um den Weg für die direkte Visualisierung des DCN löschen. </li><li> Beachten Sie die Oberfläche des DCN. Führen Optogenetik basierte Physiologie Experimente wie DCN ist jetzt zugänglich. Einführung eines Lichtreizes, zum Beispiel mit einer optischen Faser (2), um eine Optogenetik basierenden Experiment fahren. </li></ol> 5. Histologie <ol><li> Nach Abschluss der Experimente, einschläfern die Maus mit einer Überdosis von Ketamin. Perfundieren der Maus mit normaler Salzlösung, gefolgt von 4% Paraformaldehyd. </li><li> Entpacken Sie die Hirnstamm aus dem Schädel und Post-fix für 2 Stunden. Cryoprotect den Hirnstamm in 30% Saccharose für 24-48 Std. Abschnitt der Hirnstamm mit einem Standard-Kryostaten mit 60 um-Schnitte. </li></ol>

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Die Autoren haben nichts zu offenbaren.

Dieses Papier beschreibt die Technik der direkten Visualisierung des DCN im Mausmodell für die Manipulation des zentralen auditorischen Systems. Das skizzierte Ansatz der direkten Visualisierung bietet erhebliche Vorteile gegenüber dem Haupt Alternative, die stereotaktische Ansätze sind. In erster Linie die direkte Visualisierung des DCN ermöglicht sofortige Bestätigung der Website des Hirnstamms, während stereo Ansätze nicht direkte Visualisierung leisten. In Experimenten, die längere Inkubationszeiten erforder...

Virus-mediated gene transfer to reverse hearing loss has largely been focused on the peripheral auditory system.1 Targeting the cochlea, investigators have examined a host of delivery routes, including osmotic minipump infusion2, vector-transgene complex-soaked Gelfoam&#174;2 or gelatin sponge3, direct microinjection4; numerous gene transfer vectors, including adeno-associated viral vectors5,6, lentiviral vectors7, and cationic liposomes2; and the dissemination of gene transfer vectors beyond the target tissue2. Most recently, adeno-associated virus (AAV)-1 has been introduced in the cochlea in order to treat deafness in mice due to loss of vesicular glutamate transporter-3.8 Further, the application of optogenetics in peripheral auditory system has recently been described.9
Few studies, however, have examined gene transfer to the central auditory system. The dorsal cochlear nucleus (DCN) of the brainstem contain second order neurons of the auditory pathway. While gene transfer techniques in the cochlear nucleus (CN) may be utilized for a host of investigations, gene transfer of opsins, light-sensitive proteins, to the DCN may also be utilized to enable optogenetics-based experimental techniques. Following virus-mediated gene transfer delivery of an opsin, such as channelrhodopsin-2 (ChR2), the neurons of the DCN becomes sensitive to light stimuli. Optogenetic gene transfer has been previously attempted in several brainstem regions, including the rat retrotrapezoid nucleus, mouse locus coeruleus, monkey superior colliculus, and mouse ventral tegmental area.10-14
Recently, investigators have examined the use of optogenetics in the DCN.15,16 The DCN is the location of placement of auditory brainstem implants in humans, making it an attractive part of the auditory system to study for translational studies on auditory neuroprostheses. However, given the location of the DCN, surgical exposure is challenging. The technique described herein provides a protocol for maximal exposure of the DCN via posterior fossa approach to enable viral vector gene transfer and optogenetics-based experiments in a murine model. Previous studies used stereotactic microinjection into the DCN with channelrhodopsin-2.16 Stereotaxic injections, however, are potentially less accurate than injections made by direct visualization, especially in a nucleus as small and deep along the brainstem as the DCN. Transgenic mice expressing tissue specific proteins in the CN are also an attractive option and would obviate the need for gene transfer. Our protocol for exposure of the DCN would also work in transgenic mice as the DCN would need to be directly exposed for optical stimulation. This technique for surgical exposure of the DCN is adapted from previous protocols involving recordings from the auditory nerve and cochlear nucleus in mice and rat models.15,17-20
The overall goal of the protocol is to provide direct exposure to the CN to allow for gene transfer techniques. More specifically, the approach is compatible with both acute and survival surgery and the preparation can be repeated in the same animal for subsequent neurophysiological testing. The direct exposure of the DCN protocol has implications for optogenetics- and virus-mediated gene transfer-based experimentation in other nuclei of the brainstem.

<table><tbody><tr><td>Stereotaxic holder</td><td>Stoelting</td><td>51500</td><td></td></tr><tr><td>Homeothermic blanket</td><td>Harvard</td><td>507214</td><td></td></tr><tr><td>Scalpel blade #11</td><td>Fine Surgical Tools</td><td>10011-00</td><td></td></tr><tr><td>Iris scissor</td><td>Fine Surgical Tools</td><td>14084-08</td><td></td></tr><tr><td>5 French suction</td><td>Symmetry Surgical</td><td>2777914</td><td></td></tr><tr><td>Dental Points</td><td>Henry Schein</td><td>100-8170</td><td></td></tr><tr><td>Bone rongeur</td><td>Fine Surgical Tools</td><td>16020-14</td><td></td></tr><tr><td>10 &amp;micro;l Hamilton syringe</td><td>Hamilton&amp;nbsp;</td><td>7633-01</td><td></td></tr><tr><td>34 gauge, needle</td><td>Hamilton&amp;nbsp;</td><td>207434</td><td></td></tr><tr><td>Rongeurs</td><td>Fine Surgical Tools</td><td>16021-14</td><td></td></tr></tbody></table>

direct visualization of the murine dorsal cochlear nucleus for optogenetic stimulation of the auditory pathway

Untersuchung über die Verwendung von virusvermittelten Gentransfer zu verhaften oder rückwärts Hörverlust hat sich weitgehend auf die Umfangs Hörsystem verbannt worden. Nur wenige Studien haben den Gentransfer mit dem zentralen auditorischen Systems untersucht. Dorsalen cochlearen Nukleus (DCN) des Hirnstamms, die Neuronen zweiter Ordnung der Hörbahn enthält, ist eine potentielle Stelle für einen Gentransfer. In diesem Protokoll wird ein Verfahren zur direkten und maximale Exposition des murinen DCN über einen posterioren Fossa Ansatz demonstriert. Dieser Ansatz ermöglicht entweder akut oder das Überleben der Operation. Nach direkten Visualisierung des DCN, eine Vielzahl von Experimenten sind möglich, einschließlich Injektion in die Opsinen Cochleariskern und nachfolgende Stimulation durch eine optische Faser zu einer Blaulicht-Laser gekoppelt ist. Andere Neuro Experimenten wie elektrische Stimulation und neuronalen Injektor Kurven sind denkbar. Die Höhe der Visualisierungstion und die Dauer der Stimulation erreichbar machen diesen Ansatz für eine Vielzahl von Experimenten.

Teilweise Cerebellar Aspiration den Zugang zu der Cochlear Nucleus Nachdem die Haut und Muskeln, die über dem Schädel sind, Schädeloberfläche Sehenswürdigkeiten wie den koronaren und lamda Nahtlinien entfernt, zeigen die ungefähre Lokalisierung der Kraniotomie. Nach Kraniotomie mit Rongeure wird das Kleinhirn visualisiert. Sorgfältige Absaugung der kleinen Teil des Kleinhirns zeigt Visualisierung des CN, die dann injiziert werden kann (Abbildung 1). <p cl...

Watch this Scientific Journal Video about Direct Visualization of the Murine Dorsal Cochlear Nucleus for Optogenetic Stimulation of the Auditory Pathway at JoVE.com

Direct Visualization of the Murine Dorsal Cochlear Nucleus for Optogenetic Stimulation of the Auditory Pathway

The goal of this protocol is to outline a surgical approach to provide direct access to the dorsal cochlear nucleus in a murine model.

Direkte Visualisierung der Murine Rücken Cochlear Nucleus für optogenetische Stimulation der Hörbahn

Investigation into the use of virus-mediated gene transfer to arrest or reverse hearing loss has largely been relegated to the peripheral auditory system. ...

direct-visualization-murine-dorsal-cochlear-nucleus-for-optogenetic

Research

JoVE Journal

Neuroscience

9.2K Aufrufe.  Harvard Medical School. The goal of this protocol is to outline a surgical approach to provide direct access to the dorsal cochlear nucleus in a murine model. 

Serie: Direct Visualization of the Murine Dorsal Cochlear Nucleus for Optogenetic Stimulation of the Auditory Pathway

Canalostomy As a Surgical Approach to Local Drug Delivery into the Inner Ears of Adult and Neonatal Mice

Local delivery of therapeutic drugs into the inner ear is a promising therapy for inner ear diseases. Injection through semicircular canals (canalostomy) has been shown to be a useful approach to local drug delivery into the inner ear. The goal of this article is to describe, in detail, the surgical techniques involved in canalostomy in both adult and neonatal mice. As indicated by fast-green dye and adeno-associated virus serotype 8 with the green fluorescent protein gene, the canalostomy facilitated broad distribution of injected reagents in the cochlea and vestibular end-organs with minimal damage to hearing and vestibular function. The surgery was successfully implemented in both adult and neonatal mice; indeed, multiple surgeries could be performed if required. In conclusion, canalostomy is an effective and safe approach to drug delivery into the inner ears of adult and neonatal mice and may be used to treat human inner ear diseases in the future.

Here we describe canalostomy procedure which allows local drug delivery into the inner ears of adult and neonatal mice through the semicircular canal with minimum damage to hearing and vestibular function. This method can be used to inoculate viral vectors, pharmaceuticals, and small molecules into the mouse inner ear.

Canalostomy als ein chirurgisches Vorgehen zu Local Drug Delivery in das innere Ohr von Erwachsenen und Neugeborenen Mäusen

Local delivery of therapeutic drugs into the inner ear is a promising therapy for inner ear diseases. Injection through semicircular canals (canalostomy) ...

Forschung

Genetik

Laser-scanning Photostimulation of Optogenetically Targeted Forebrain Circuits

The sensory forebrain is composed of intricately connected cell types, of which functional properties have yet to be fully elucidated. Understanding the interactions of these forebrain circuits has been aided recently by the development of optogenetic methods for light-mediated modulation of neuronal activity. Here, we describe a protocol for examining the functional organization of forebrain circuits&#160;in vitro using laser-scanning photostimulation of channelrhodopsin, expressed optogenetically via viral-mediated transfection. This approach also exploits the utility of cre-lox recombination in transgenic mice to target expression in specific neuronal cell types. Following transfection, neurons are physiologically recorded in slice preparations using whole-cell patch clamp to measure their evoked responses to laser-scanning photostimulation of channelrhodopsin expressing fibers. This approach enables an assessment of functional topography and synaptic properties. Morphological correlates can be obtained by imaging the neuroanatomical expression of channelrhodopsin expressing fibers using confocal microscopy of the live slice or post-fixed tissue. These methods enable functional investigations of forebrain circuits that expand upon more conventional approaches.

We describe a method for characterizing the functional topography and synaptic properties of forebrain circuits using an optogenetic approach to photostimulate neuronal populations&#160;in vitro.

The sensory forebrain is composed of intricately connected cell types, of which functional properties have yet to be fully elucidated. Understanding the ...

Neurowissenschaften

Primary Culture and Plasmid Electroporation of the Murine Organ of Corti. 

In all mammals, the sensory epithelium for audition is located along the spiraling organ of Corti that resides within the conch shaped cochlea of the inner ear (fig 1). Hair cells in the developing cochlea, which are the mechanosensory cells of the auditory system, are aligned in one row of inner hair cells and three (in the base and mid-turns) to four (in the apical turn) rows of outer hair cells that span the length of the organ of Corti. Hair cells transduce sound-induced mechanical vibrations of the basilar membrane into neural impulses that the brain can interpret. Most cases of sensorineural hearing loss are caused by death or dysfunction of cochlear hair cells.
An increasingly essential tool in auditory research is the isolation and in vitro culture of the organ explant 1,2,9. Once isolated, the explants may be utilized in several ways to provide information regarding normative, anomalous, or therapeutic physiology. Gene expression, stereocilia motility, cell and molecular biology, as well as biological approaches for hair cell regeneration are examples of experimental applications of organ of Corti explants.
This protocol describes a method for the isolation and culture of the organ of Corti from neonatal mice. The accompanying video includes stepwise directions for the isolation of the temporal bone from mouse pups, and subsequent isolation of the cochlea, spiral ligament, and organ of Corti. Once isolated, the sensory epithelium can be plated and cultured in vitro in its entirety, or as a further dissected micro-isolate that lacks the spiral limbus and spiral ganglion neurons. Using this method, primary explants can be maintained for 7-10 days. As an example of the utility of this procedure, organ of Corti explants will be electroporated with an exogenous DsRed reporter gene. This method provides an improvement over other published methods because it provides reproducible, unambiguous, and stepwise directions for the isolation, microdissection, and primary culture of the organ of Corti.

Primary Culture and Plasmid Electroporation of the Murine Organ of Corti.

This procedure describes a method for the isolation and culture of the murine organ of Corti with or without the spiral limbus and spiral ganglion neurons. We also demonstrate a method for the expression of an exogenous reporter gene in the organ of Corti explant by electroporation.

Primäre Kultur und Plasmid Elektroporation der Murine Corti-Organ.

In all mammals, the sensory epithelium for audition is located along the spiraling organ of Corti that resides within the conch shaped cochlea of the ...

Biologie

In vivo Optogenetic Stimulation of the Rodent Central Nervous System

The ability to probe defined neural circuits in awake, freely-moving animals with cell-type specificity, spatial precision, and high temporal resolution has been a long sought tool for neuroscientists in the systems-level search for the neural circuitry governing complex behavioral states. Optogenetics is a cutting-edge tool that is revolutionizing the field of neuroscience and represents one of the first systematic approaches to enable causal testing regarding the relation between neural signaling events and behavior. By combining optical and genetic approaches, neural signaling can be bi-directionally controlled through expression of light-sensitive ion channels (opsins) in mammalian cells. The current protocol describes delivery of specific wavelengths of light to opsin-expressing cells in deep brain structures of awake, freely-moving rodents for neural circuit modulation. Theoretical principles of light transmission as an experimental consideration are discussed in the context of performing in vivo optogenetic stimulation. The protocol details the design and construction of both simple and complex laser configurations and describes tethering strategies to permit simultaneous stimulation of multiple animals for high-throughput behavioral testing.

In vivo Optogenetic Stimulation of the Rodent Central Nervous System

Optogenetics has become a powerful tool for use in behavioral neuroscience experiments. This protocol offers a step-by-step guide to the design and set-up of laser systems, and provides a full protocol for carrying out multiple and simultaneous in vivo optogenetic stimulations compatible with most rodent behavioral testing paradigms.

In vivo optogenetische Stimulation des Nager Central Nervous System

The ability to probe defined neural circuits in awake, freely-moving animals with cell-type specificity, spatial precision, and high temporal resolution ...

A Guide to In vivo Single-unit Recording from Optogenetically Identified Cortical Inhibitory Interneurons

A major challenge in neurophysiology has been to characterize the response properties and function of the numerous inhibitory cell types in the cerebral cortex. We here share our strategy for obtaining stable, well-isolated single-unit recordings from identified inhibitory interneurons in the anesthetized mouse cortex using a method developed by Lima and colleagues1. Recordings are performed in mice expressing Channelrhodopsin-2 (ChR2) in specific neuronal subpopulations. Members of the population are identified by their response to a brief flash of blue light. This technique &#8211; termed &#8220;PINP&#8221;, or Photostimulation-assisted Identification of Neuronal Populations &#8211; can be implemented with standard extracellular recording equipment. It can serve as an inexpensive and accessible alternative to calcium imaging or visually-guided patching, for the purpose of targeting extracellular recordings to genetically-identified cells. Here we provide a set of guidelines for optimizing the method in everyday practice. We refined our strategy specifically for targeting parvalbumin-positive (PV+) cells, but have found that it works for other interneuron types as well, such as somatostatin-expressing (SOM+) and calretinin-expressing (CR+) interneurons.

A Guide to In vivo Single-unit Recording from Optogenetically Identified Cortical Inhibitory Interneurons

Here we describe our strategy for obtaining stable, well-isolated single-unit recordings from identified inhibitory interneurons in the anesthetized mouse cortex. Neurons expressing ChR2 are identified by their response to blue light. The method uses standard extracellular recording equipment, and serves as an inexpensive alternative to calcium imaging or visually-guided patching.

Ein Leitfaden zur<em&gt; In vivo</em&gt; Single-Unit-Aufnahme von Optogenetically Identifizierte kortikalen inhibitorischen Inter

A major challenge in neurophysiology has been to characterize the response properties and function of the numerous inhibitory cell types in the cerebral ...

Optogenetic Stimulation of the Auditory Nerve

Direct electrical stimulation of spiral ganglion neurons (SGNs) by cochlear implants (CIs) enables open speech comprehension in the majority of implanted deaf subjects1-6. Nonetheless, sound coding with current CIs has poor frequency and intensity resolution due to broad current spread from each electrode contact activating a large number of SGNs along the tonotopic axis of the cochlea7-9. Optical stimulation is proposed as an alternative to electrical stimulation that promises spatially more confined activation of SGNs and, hence, higher frequency resolution of coding. In recent years, direct infrared illumination of&#160;the cochlea has been used to evoke responses in the auditory nerve10. Nevertheless it requires higher energies than electrical stimulation10,11 and uncertainty remains as to the underlying mechanism12. Here we describe a method based on optogenetics to stimulate SGNs with low intensity blue light, using transgenic mice with neuronal expression of channelrhodopsin 2 (ChR2)13 or virus-mediated expression of the ChR2-variant CatCh14. We used micro-light emitting diodes (&#181;LEDs) and fiber-coupled lasers to stimulate ChR2-expressing SGNs through a small artificial opening (cochleostomy) or the round window. We assayed the responses by scalp recordings of light-evoked potentials (optogenetic auditory brainstem response: oABR) or by microelectrode recordings from the auditory pathway and compared them with acoustic and electrical stimulation.

Cochlear implants (CIs) enable hearing by direct electrical stimulation of the auditory nerve. However, poor frequency and intensity resolution limits the quality of hearing with CIs. Here we describe optogenetic stimulation of the auditory nerve in mice as an alternative strategy for auditory research and developing future CIs.

Optogenetische Stimulation des Hörnervs

Direct electrical stimulation of spiral ganglion neurons (SGNs) by cochlear implants (CIs) enables open speech comprehension in the majority of implanted ...

Neonatal Murine Cochlear Explant Technique as an In Vitro Screening Tool in Hearing Research

While there have been remarkable advances in hearing research over the past few decades, there is still no cure for Sensorineural Hearing Loss (SNHL), a condition that typically involves damage to or loss of the delicate mechanosensory structures of the inner ear. Sophisticated in vitro and ex vivo assays have emerged in recent years, enabling the screening of an increasing number of potentially therapeutic compounds while minimizing resources and accelerating efforts to develop cures for SNHL. Though homogenous cultures of certain cell types continue to play an important role in current research, many scientists now rely on more complex organotypic cultures of murine inner ears, also known as cochlear explants. The preservation of organized cellular structures within the inner ear facilitates the in situ evaluation of various components of the cochlear infrastructure, including inner and outer hair cells, spiral ganglion neurons, neurites, and supporting cells. Here we present the preparation, culture, treatment, and immunostaining of neonatal murine cochlear explants. The careful preparation of these explants facilitates the identification of mechanisms that contribute to SNHL and constitutes a valuable tool for the hearing research community.

Neonatal Murine Cochlear Explant Technique as an In Vitro Screening Tool in Hearing Research

The goal of this protocol is to demonstrate the preparation, culture, treatment, and immunostaining of neonatal murine cochlear explants. The technique can be utilized as an in vitro screening tool in hearing research.

Neonatal Murine Cochlear Explant Technik als<em&gt; In vitro</em&gt; Screening-Tool in der Hörforschung

While there have been remarkable advances in hearing research over the past few decades, there is still no cure for Sensorineural Hearing Loss (SNHL), a ...

Medizin

In Vitro Wedge Slice Preparation for Mimicking In Vivo Neuronal Circuit Connectivity

In vitro slice electrophysiology techniques measure single-cell activity with precise electrical and temporal resolution. Brain slices must be relatively thin to properly visualize and access neurons for patch-clamping or imaging, and in vitro examination of brain circuitry is limited to only what is physically present in the acute slice. To maintain the benefits of in vitro slice experimentation while preserving a larger portion of presynaptic nuclei, we developed a novel slice preparation. This &#8220;wedge slice&#8221; was designed for patch-clamp electrophysiology recordings to characterize the diverse monaural, sound-driven inputs to medial olivocochlear (MOC) neurons in the brainstem. These neurons receive their primary afferent excitatory and inhibitory inputs from neurons activated by stimuli in the contralateral ear and corresponding cochlear nucleus (CN). An asymmetrical brain slice was designed which is thickest in the rostro-caudal domain at the lateral edge of one hemisphere and then thins towards the lateral edge of the opposite hemisphere. This slice contains, on the thick side, the auditory nerve root conveying information about auditory stimuli to the brain, the intrinsic CN circuitry, and both the disynaptic excitatory and trisynaptic inhibitory afferent pathways that converge on contralateral MOC neurons. Recording is performed from MOC neurons on the thin side of the slice, where they are visualized using DIC optics for typical patch-clamp experiments. Direct stimulation of the auditory nerve is performed as it enters the auditory brainstem, allowing for intrinsic CN circuit activity and synaptic plasticity to occur at synapses upstream of MOC neurons. With this technique, one can mimic in vivo circuit activation as closely as possible within the slice. This wedge slice preparation is applicable to other brain circuits where circuit analyses would benefit from preservation of upstream connectivity and long-range inputs, in combination with the technical advantages of in vitro slice physiology.

Integration of diverse synaptic inputs to neurons is best measured in a preparation that preserves all pre-synaptic nuclei for natural timing and circuit plasticity, but brain slices typically sever many connections. We developed a modified brain slice to mimic in vivo circuit activity while maintaining in vitro experimentation capability.

In Vitro Wedge Slice Vorbereitung für Diemimitieren In Vivo Neuronal Circuit Connectivity

In vitro slice electrophysiology techniques measure single-cell activity with precise electrical and temporal resolution. Brain slices must be relatively ...

Optrode Array for Simultaneous Optogenetic Modulation and Electrical Neural Recording

During the last decade, optogenetics has become an essential tool for the investigation of neural signaling due to its unique capability of selective neural modulation or monitoring. As specific types of neuronal cells can be genetically modified to express opsin proteins, optogenetics enables optical stimulation or inhibition of the selected neurons. There have been several technological advances in the optical system for optogenetics. Recently, it was proposed to combine the optical waveguide for light delivery with electrophysiological recording to simultaneously monitor the neural responses to optogenetic stimulation or inhibition. In this study, an implantable optrode array (2x2 optical fibers) was developed with embedded multichannel electrodes. 
A light-emitting diode (LED) was employed as a light source, and a microfabricated microlens array was integrated to provide sufficient light power at the tip of the optical fibers. The optrode array system comprises the disposable part and the reusable part. The disposable part has optical fibers and electrodes, while the reusable part has the LED and electronic circuitry for light control and neural signal processing. The novel design of the implantable optrode array system is introduced in the accompanying video in addition to the procedure of the optrode implantation surgery, optogenetic light stimulation, and the electrophysiological neural recording. The results of in vivo experiments successfully showed time-locked neural spikes evoked by the light stimuli from hippocampal excitatory neurons of mice.

Here, we present the fabrication method of an optrode system with optical fibers for light delivery and an electrode array for neural recording. In vivo experiments with transgenic mice expressing channelrhodopsin-2 show the feasibility of the system for simultaneous optogenetic stimulation and electrophysiological recording.

Optroden-Array zur simultanen optogenetischen Modulation und elektrischen neuronalen Aufzeichnung

During the last decade, optogenetics has become an essential tool for the investigation of neural signaling due to its unique capability of selective ...

Preparing Wedge Brain Slices to Visualize Auditory Neurons

Source: Fischl, M. J. et al., <a href="https://app.jove.com/v/61664">In Vitro Wedge Slice Preparation for Mimicking In Vivo Neuronal Circuit Connectivity.</a>&#160;J. Vis. Exp.&#160;(2020)
This video demonstrates the process of preparing wedge-shaped brain slices in a laboratory setting. Using a vibratome, a wedge-shaped slice from a mouse&#39;s brain is crafted with varying thickness. This slice contains the auditory nerve root positioned on the thicker end, while the hearing-related neurons are located on the thinner end.

Vorbereiten von Keilhirnschnitten zur Visualisierung auditiver Neuronen

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
1. Brain ...

Direkte Visualisierung der Murine Rücken Cochlear Nucleus für optogenetische Stimulation der Hörbahn

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