Diese Arbeit wird durch den CBS Bridging Grant finanziert, der ooM verliehen wird. OOM, PAA und AS entwarfen die Studie und führten die Experimente durch. AS und PAA analysierten die Ergebnisse. OOM und PAA bereiteten das Manuskript vor. Wir danken Dr. Karl Disseroth (Stanford University) für die Bereitstellung des AAV für unsere Nutzung.

<ol>
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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Cre-dependent,+anterograde+transsynaptic+viral+tracer+for+mapping+output+pathways+of+genetically+marked+neurons.">A Cre-dependent, anterograde transsynaptic viral tracer for mapping output pathways of genetically marked neurons.</a> Neuron. 72 (6), 938-950 (2011).</li><li>Li, J., Liu, T., Dong, Y., Kondoh, K., Lu, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trans-synaptic+Neural+Circuit-Tracing+with+Neurotropic+Viruses.">Trans-synaptic Neural Circuit-Tracing with Neurotropic Viruses.</a> Neuroscience bulletin. , 1-12 (2019).</li><li>Kuypers, H., Ugolini, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Viruses+as+transneuronal+tracers.">Viruses as transneuronal tracers.</a> Trends in neurosciences. 13 (2), 71-75 (1990).</li><li>Atasoy, D., Aponte, Y., Su, H. 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G., Tejero-Cantero, A., Trouche, S., Campo-Urriza, N., Dupret, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dopaminergic+neurons+promote+hippocampal+reactivation+and+spatial+memory+persistence.">Dopaminergic neurons promote hippocampal reactivation and spatial memory persistence.</a> Nature Neuroscience. 17 (12), 1658-1660 (2014).</li><li>Cardin, J. 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Die Autoren haben nichts preiszugeben.

In den letzten zehn Jahren hat sich das Design von AAV-Konstrukten erheblich weiterentwickelt. Daher wurden mehr neuronenspezifische Promotoren in eine Reihe von AAV-Serotypen integriert, um die Transfektionsspezifität zu verbessern14. Durch die Kombination von Genen für Fluoreszenzproteine, Transporter, Rezeptoren und Ionenkanäle existieren nun Bibliotheken von AAV für bildgebung, neuromodulation und synaptische Aktivitätserkennung. In kommerziell erhältlichen AAV-Konstrukten ermöglicht ei...

In den letzten zehn Jahren wurde eine Reihe genetischer Werkzeuge entwickelt, um die Spezifität der Modulation vom Neuronentyp und die Kartierung komplexer neuronaler Netze zu erhöhen1. Insbesondere neurotrope Viren mit einer inhärenten Fähigkeit, sich in neuronalen Zellen zu infizieren und zu replizieren, wurden eingesetzt, um bestimmte Proteine in Neuronensubtypen zu exprimieren oder abtränken. Bei der Unterung von Fluoreszenzproteinen oder genetisch kodierten synaptischen Aktivitätsindikatoren kennzeichnen und beschreiben transfizierte AAV-Vektoren neuronale Netzwerke über Gehirnregionen hinweg2,3. Die Wahl eines Promotors im AAV-Konstrukt steuert die Expression des Vektors in Neuronentypen mit einem gewissen Grad an Spezifität(promotorabhängige Expression). Durch die Cre-lox-Rekombination werden AAV-Konstrukte jedoch mit größerer Spezifität für die Neuronenmarkierung4,5,6,7eingesetzt. Bemerkenswert ist, dass photoaktivierte mikrobielle Opsine und Fluoreszenzproteine, die in AAV-Vektoren verpackt sind, in verschiedenen Neuronensubtypen8exprimiert werden können und ideal für die Bildgebung, die Verfolgung von Neuronenschaltungen und die Photomodulation9,10sind.
AAVs-Konstrukte, die stereotaktisch in eine Gehirnregion (oder einen Zellkern) injiziert werden, treiben die Expression des Reporterproteins in den Terminals soma, Dendriten und Axone an. Die neuronale Expression von AAV, die ein Reportergen (eYFP) beherbergt, erleichtert die Markierung von Neuronenzellkörpern und die anatomische Verfolgung von Projektionen zu und von anderen Gehirnregionen11,12,13,14. AAV-eYFP-Konstrukte, die lichtgesteuertes Opsin (z. B. hChR2) tragen, können als Werkzeug für die Bildgebungvon 6,15 und die stimulationsbasierte physiologische Verfolgung neuronaler Projektionen auf Hirnareale in vivo16eingesetzt werden. Abhängig vom AAV-Serotyp kann die Richtung der Neuronenmarkierung anterograde oder retrograd sein11,12. Frühere Studien haben ergeben, dass AAV5 anterograde in Neuronenreist 12. So erzeugt die Photostimulation von Zellkörpern, die hChR2 exprimieren, präsynaptische Effekte an anderer Stelle im Gehirn (Ziel)17.
Hier wurde AAV (Serotyp 5) mit einem CaMKIIα-Promotor verwendet, um eYFP (Reporter) und hChR2 (Opsin) in VTA-Glutamat-Neuronen und axonalen Projektionen zu exprimieren. Die Ergebnisse dieser Studie zeigen die schichtabhängige Verteilung von VTA-Glutamat-präsynaptischen Terminals in den Hippocampusregionen CA1, CA3 und DG. Auch die Photostimulation von VTA-Glutamat-Neuronen erhöhte die CA1-Feuerraten mit mehreren Einheiten und Einzeleinheiten in vivo im Vergleich zu den Ausgangswerten. Dieses Protokoll verwendet erschwingliche Tools und kommerziell erhältliche Software, die die Qualität der Daten aus neuronalen Schaltkreis-Tracing-Experimenten erhöhen können.

<table>
	<tbody>
		<tr>
			<td>3% Hydrogen peroxide</td>
			<td>Fisher chemical</td>
			<td>H312</td>
			<td></td>
		</tr>
		<tr>
			<td>AAV-CaMKII&#945;-ChR2-eGYP</td>
			<td>Addgene</td>
			<td>Plasmid #26969</td>
			<td></td>
		</tr>
		<tr>
			<td>BNC cable</td>
			<td>Amazon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>BNC Splitter</td>
			<td>Amazon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ceramic Split Mating Sleeve for &#216;1.25mm Ferrules.</td>
			<td>Thorlabs</td>
			<td>ADAL1-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Drill</td>
			<td>Dremel</td>
			<td>LR 39098</td>
			<td></td>
		</tr>
		<tr>
			<td>Gelatin coated slides</td>
			<td>Fisher scientific</td>
			<td>OBSLD01CS</td>
			<td></td>
		</tr>
		<tr>
			<td>Hamilton&#39;s syringe (Neuros)</td>
			<td>WPI Inc.</td>
			<td>06H</td>
			<td></td>
		</tr>
		<tr>
			<td>Head stage adapter</td>
			<td>Neuronexus</td>
			<td>Adpt-Q4-OM32</td>
			<td></td>
		</tr>
		<tr>
			<td>High impedance silicon probe</td>
			<td>Neuronexus</td>
			<td>Q1x1-tet-5mm-121-CQ4</td>
			<td></td>
		</tr>
		<tr>
			<td>INTAN 512ch Recording Controller</td>
			<td>INTAN</td>
			<td>RHD2000</td>
			<td></td>
		</tr>
		<tr>
			<td>Iodine solution</td>
			<td>Dynarex</td>
			<td>1425</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Piramal</td>
			<td>NDC 66794-017-25</td>
			<td></td>
		</tr>
		<tr>
			<td>Ketamine</td>
			<td>Spectrum</td>
			<td>K1068</td>
			<td></td>
		</tr>
		<tr>
			<td>LED Driver</td>
			<td>Thorlabs</td>
			<td>LEDD1B</td>
			<td></td>
		</tr>
		<tr>
			<td>LED light source (470 nm)-blue light</td>
			<td>Thorlabs</td>
			<td>M470F3</td>
			<td></td>
		</tr>
		<tr>
			<td>Micromanipulator</td>
			<td>Narishige</td>
			<td>M0-203</td>
			<td></td>
		</tr>
		<tr>
			<td>Optic fiber</td>
			<td>Thorlabs</td>
			<td>CFMLC14L05</td>
			<td></td>
		</tr>
		<tr>
			<td>Pan head philips screw (M0.6 X 2mm)</td>
			<td>Amazon</td>
			<td>M0.6 X 2mm</td>
			<td></td>
		</tr>
		<tr>
			<td>Pre-amplifier headstage (32 Channel)</td>
			<td>INTAN</td>
			<td>C3314</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereotaxic frame</td>
			<td>Kopf</td>
			<td>1530</td>
			<td></td>
		</tr>
		<tr>
			<td>TTL pulser</td>
			<td>Prizmatix</td>
			<td>4031</td>
			<td></td>
		</tr>
		<tr>
			<td>Urethane</td>
			<td>Sigma</td>
			<td>U2500</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylazine</td>
			<td>Alfa Aesar</td>
			<td>J61430</td>
			<td></td>
		</tr>
		<tr>
			<td>Software</td>
			<td>Company</td>
			<td>Version</td>
			<td></td>
		</tr>
		<tr>
			<td>Graphpad Prism</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Intan Recording Controller</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Neuroexplorer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Plexon Offline Spike Sorter</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ACSF Composition:</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>oxygenated ACSF with 95% Oxygen/5%CO2 constantly being bubbled through the ACSF (ACSF; in mM 125 NaCl, 25 NaHCO3, 3 KCl, 1.25 NaH2PO4, 1 MgCl2, 2 CaCl2 and 25 Glucose).</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

combined in vivo anatomical and functional tracing of ventral tegmental area glutamate terminals in the hippocampus

Die optogenetische Modulation von Neuronensubpopulationen im Gehirn hat es Forschern ermöglicht, neuronale Schaltkreise in vivo und ex vivo zu sezieren. Dies bietet eine Voraussetzung für die Bestimmung der Rolle von Neuronentypen innerhalb eines neuronalen Schaltkreises und ihrer Bedeutung für die Informationscodierung in Bezug auf das Lernen. Ebenso kann die Methode verwendet werden, um die physiologische Bedeutung von zwei oder mehr miteinander verbundenen Hirnregionen bei wachen und betäubten Tieren zu testen. Die aktuelle Studie zeigt, wie VTA-Glutamat-Neuronen die Feuerrate von mutmaßlichen Pyramidenneuronen im CA1 (Hippocampus) anästhesierter Mäuse modulieren. Dieses Protokoll verwendet adeno-assoziierte Virus (AAV)-abhängige Markierung von VTA-Glutamat-Neuronen für die Rückverfolgung von VTA-präsynaptischen Glutamat-Terminals in den Schichten des Hippocampus. Die Expression von lichtgesteuertem Opsin (Channelrhodopsin; hChR2) und Fluoreszenzprotein (eYFP), die durch den AAV-Vektor beherbergt werden, ermöglichte die anterograde Rückverfolgung von VTA-Glutamatterminals und die Photostimulation von VTA-Glutamat-Neuronenzellkörpern (im VTA). Hochimige akute Siliziumelektroden wurden im CA1 positioniert, um Reaktionen von mehreren einheiten und einzelnen Einheiten auf VTA-Photostimulation in vivo zu erkennen. Die Ergebnisse dieser Studie zeigen die schichtabhängige Verteilung von präsynaptischen VTA-Glutamatterminals im Hippocampus (CA1, CA3 und DG). Auch die Photostimulation von VTA-Glutamat-Neuronen erhöhte die Feuer- und Burst-Rate von mutmaßlichen CA1-Pyramideneinheiten in vivo.

Anterograde Rückverfolgung
Die AAV-Expression wurde durch Immunfluoreszenz-Bildgebung des Reporterproteins (eYFP) im VTA von C57BL/6-Mäusen 21 Tage nach der Injektion verifiziert(Abbildung 2). Die erfolgreiche anterograde Markierung von präsynaptischen VTA-Glutamatprojektionen im Hippocampus wurde auch durch eYFP-Nachweis in den Schichten von DG, CA3 und CA1 nachgewiesen(Abbildung 6a–d; Film 2 und 3</stro...

Watch this Scientific Journal Video about Combined In Vivo Anatomical and Functional Tracing of Ventral Tegmental Area Glutamate Terminals in the Hippocampus at JoVE.com

Combined In Vivo Anatomical and Functional Tracing of Ventral Tegmental Area Glutamate Terminals in the Hippocampus

Das aktuelle Protokoll demonstriert eine einfache Methode zur Rückverfolgung von ventralen Tegmentalflächen (VTA) Glutamatprojektionen auf den Hippocampus. Die Photostimulation von VTA-Glutamat-Neuronen wurde mit CA1-Aufnahmen kombiniert, um zu zeigen, wie VTA-Glutamat-Terminals die mutmaßliche pyramidale CA1-Feuerrate in vivo modulieren.

Kombinierte in vivo anatomische und funktionelle Spurensuche von ventralen Tegmentalflächen-Glutamat-Terminals im Hippocampus

Optogenetic modulation of neuron sub-populations in the brain has allowed researchers to dissect neural circuits in vivo and ex vivo. This provides a ...

combined-vivo-anatomical-functional-tracing-ventral-tegmental-area

Research

JoVE Journal

Neuroscience

3.8K Aufrufe.  Louisiana State University School of Veterinary Medicine. Das aktuelle Protokoll demonstriert eine einfache Methode zur Rückverfolgung von ventralen Tegmentalflächen (VTA) Glutamatprojektionen auf den Hippocampus. Die Photostimulation von VTA-Glutamat-Neuronen wurde mit CA1-Aufnahmen kombiniert, um zu zeigen, wie VTA-Glutamat-Terminals die mutmaßliche pyramidale CA1-Feuerrate in vivo modulieren.

Serie: Combined In Vivo Anatomical and Functional Tracing of Ventral Tegmental Area Glutamate Terminals in the Hippocampus

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.

Funktionelle Bildgebung mit Ultraschall-Blut-Hirnschranke Störung und Mangan-MRT

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

Forschung

Neurowissenschaften

Comprehensive Profiling of Dopamine Regulation in Substantia Nigra and Ventral Tegmental Area

Dopamine is a vigorously studied neurotransmitter in the CNS. Indeed, its involvement in locomotor activity and reward-related behaviour has fostered five decades of inquiry into the molecular deficiencies associated with dopamine regulation. The majority of these inquiries of dopamine regulation in the brain focus upon the molecular basis for its regulation in the terminal field regions of the nigrostriatal and mesoaccumbens pathways; striatum and nucleus accumbens. Furthermore, such studies have concentrated on analysis of dopamine tissue content with normalization to only wet tissue weight. Investigation of the proteins that regulate dopamine, such as tyrosine hydroxylase (TH) protein, TH phosphorylation, dopamine transporter (DAT), and vesicular monoamine transporter 2 (VMAT2) protein often do not include analysis of dopamine tissue content in the same sample. The ability to analyze both dopamine tissue content and its regulating proteins (including post-translational modifications) not only gives inherent power to interpreting the relationship of dopamine with the protein level and function of TH, DAT, or VMAT2, but also extends sample economy. This translates into less cost, and yet produces insights into the molecular regulation of dopamine in virtually any paradigm of the investigators' choice.
We focus the analyses in the midbrain. Although the SN and VTA are typically neglected in most studies of dopamine regulation, these nuclei are easily dissected with practice. A comprehensive readout of dopamine tissue content and TH, DAT, or VMAT2 can be conducted. There is burgeoning literature on the impact of dopamine function in the SN and VTA on behavior, and the impingements of exogenous substances or disease processes therein 1-5. Furthermore, compounds such as growth factors have a profound effect on dopamine and dopamine-regulating proteins, to a comparatively greater extent in the SN or VTA 6-8. Therefore, this methodology is presented for reference to laboratories that want to extend their inquiries on how specific treatments modulate behaviour and dopamine regulation. Here, a multi-step method is presented for the analyses of dopamine tissue content, the protein levels of TH, DAT, or VMAT2, and TH phosphorylation from the substantia nigra and VTA from rodent midbrain. The analysis of TH phosphorylation can yield significant insights into not only how TH activity is regulated, but also the signaling cascades affected in the somatodendritic nuclei in a given paradigm.
We will illustrate the dissection technique to segregate these two nuclei and the sample processing of dissected tissue that produces a profile revealing molecular mechanisms of dopamine regulation in vivo, specific for each nuclei (Figure 1).

Dopamine is distinctly regulated in the midbrain nuclei, which contain the cell bodies and dendrites of the dopamine neurons. Here we describe a dissection and sample-handling approach to maximize results, and thus conclusions and insights, on dopamine regulation in the midbrain nuclei of the substantia nigra (SN) and ventral tegmental area (VTA) in rodents.

Umfassende Profilierung der Verordnung Dopamin in der Substantia nigra und ventralen Tegmentum

Dopamine is a vigorously studied neurotransmitter in the CNS. Indeed, its involvement in locomotor activity and reward-related behaviour has fostered five ...

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.

Schnelle Micro-Iontophorese von Glutamat und GABA: Ein nützliches Tool, um Synaptic Integration Untersuchen

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

Ex Vivo Preparations of the Intact Vomeronasal Organ and Accessory Olfactory Bulb

The mouse accessory olfactory system (AOS) is a specialized sensory pathway for detecting nonvolatile social odors, pheromones, and kairomones. The first neural circuit in the AOS pathway, called the accessory olfactory bulb (AOB), plays an important role in establishing sex-typical behaviors such as territorial aggression and mating. This small (&#60;1 mm3) circuit possesses the capacity to distinguish unique behavioral states, such as sex, strain, and stress from chemosensory cues in the secretions and excretions of conspecifics. While the compact organization of this system presents unique opportunities for recording from large portions of the circuit simultaneously, investigation of sensory processing in the AOB remains challenging, largely due to its experimentally disadvantageous location in the brain. Here, we demonstrate a multi-stage dissection that removes the intact AOB inside a single hemisphere of the anterior mouse skull, leaving connections to both the peripheral vomeronasal sensory neurons (VSNs) and local neuronal circuitry intact. The procedure exposes the AOB surface to direct visual inspection, facilitating electrophysiological and optical recordings from AOB circuit elements in the absence of anesthetics. Upon inserting a thin cannula into the vomeronasal organ (VNO), which houses the VSNs, one can directly expose the periphery to social odors and pheromones while recording downstream activity in the AOB. This procedure enables controlled inquiries into AOS information processing, which can shed light on mechanisms linking pheromone exposure to changes in behavior.

Ex Vivo Preparations of the Intact Vomeronasal Organ and Accessory Olfactory Bulb

The mouse accessory olfactory bulb (AOB) has been difficult to study in the context of sensory coding. Here, we demonstrate a dissection that produces an ex vivo preparation in which AOB neurons remain functionally connected to their peripheral inputs, facilitating research into information processing of mouse pheromones and kairomones.

Ex vivo Zubereitungen der Intact Vomeronasalorgan und akzessorischen olfaktorischen Bulbus

The mouse accessory olfactory system (AOS) is a specialized sensory pathway for detecting nonvolatile social odors, pheromones, and kairomones. The first ...

Laser Capture Microdissection - A Demonstration of the Isolation of Individual Dopamine Neurons and the Entire Ventral Tegmental Area

Laser capture microdissection (LCM) is used to isolate a concentrated population of individual cells or precise anatomical regions of tissue from tissue sections on a microscope slide. When combined with immunohistochemistry, LCM can be used to isolate individual cells types based on a specific protein marker. Here, the LCM technique is described for collecting a specific population of dopamine neurons directly labeled with&#160;tyrosine hydroxylase immunohistochemistry and for isolation of the dopamine neuron containing region of the ventral tegmental area using indirect tyrosine hydroxylase immunohistochemistry on a section adjacent to those used for LCM. An infrared (IR) capture laser is used to both dissect individual neurons as well as the ventral tegmental area off glass slides and onto an LCM cap for analysis. Complete dehydration of the tissue with 100% ethanol and xylene is critical. The combination of the IR capture laser and the ultraviolet (UV) cutting laser is used to isolate individual dopamine neurons or the ventral tegmental area when using PEN membrane slides. A PEN membrane slide has significant advantages over a glass slide as it offers better consistency in capturing and collecting cells, is faster collecting large pieces of tissue, is less reliant on dehydration and results in complete removal of the tissue from the slide. Although removal of large areas of tissue from a glass slide is feasible, it is considerably more time consuming and frequently leaves some residual tissue behind. Data shown here demonstrate that RNA of sufficient quantity and quality can be obtained using these procedures for quantitative PCR measurements. Although RNA and DNA are the most commonly isolated molecules from tissue and cells collected with LCM, isolation and measurement of microRNA, protein and epigenetic changes in DNA can also benefit from the enhanced anatomical and cellular resolution obtained using LCM.

The isolation of individual dopamine neurons or the ventral tegmental area with direct or indirect immunohistochemistry is demonstrated using laser capture microdissection. Parameters for isolation of tissue from a glass slide using an infrared laser and from membrane slides using the combination of an infrared and ultraviolet laser are discussed.

Laser Mikrodissektion - Eine Demonstration der Isolation der einzelnen Dopamin-Neuronen und die gesamte ventrale Tegmentum

Laser capture microdissection (LCM) is used to isolate a concentrated population of individual cells or precise anatomical regions of tissue from tissue ...

Conditional Genetic Transsynaptic Tracing in the Embryonic Mouse Brain

Anatomical path tracing is of pivotal importance to decipher the relationship between brain and behavior. Unraveling the formation of neural circuits during embryonic maturation of the brain however is technically challenging because most transsynaptic tracing methods developed to date depend on stereotaxic tracer injection. To overcome this problem, we developed a binary genetic strategy for conditional genetic transsynaptic tracing in the mouse brain. Towards this end we generated two complementary knock-in mouse strains to selectively express the bidirectional transsynaptic tracer barley lectin (BL) and the retrograde transsynaptic tracer Tetanus Toxin fragment C from the ROSA26 locus after Cre-mediated recombination. Cell-specific tracer production in these mice is genetically encoded and does not depend on mechanical tracer injection. Therefore our experimental approach is suitable to study neural circuit formation in the embryonic murine brain. Furthermore, because tracer transfer across synapses depends on synaptic activity, these mouse strains can be used to analyze the communication between genetically defined neuronal populations during brain development at a single cell resolution. Here we provide a detailed protocol for transsynaptic tracing in mouse embryos using the novel recombinant ROSA26 alleles. We have utilized this experimental technique in order to delineate the neural circuitry underlying maturation of the reproductive axis in the developing female mouse brain.

Capitalizing on a binary genetic strategy we provide a detailed protocol for neural circuit tracing in mice that express complementary transsynaptic tracers after Cre-mediated recombination. Because cell-specific tracer production is genetically encoded, our experimental approach is suitable to study the formation and maturation of neural circuitry during murine embryonic brain development at a single cell resolution.

Bedingte Genetische transsynaptische Tracing in der embryonalen Maus-Gehirn

Anatomical path tracing is of pivotal importance to decipher the relationship between brain and behavior. Unraveling the formation of neural circuits ...

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise from extra-retinal sources. Ex vivo ERG provides an efficient method to dissect the function of retinal cells directly from an intact isolated retina of animals or donor eyes. In addition, ex vivo ERG can be used to test the efficacy and safety of potential therapeutic agents on retina tissue from animals or humans. We show here how commercially available in vivo ERG systems can be used to conduct ex vivo ERG recordings from isolated mouse retinas. We combine the light stimulation, electronic and heating units of a standard in vivo system with custom-designed specimen holder, gravity-controlled perfusion system and electromagnetic noise shielding to record low-noise ex vivo ERG signals simultaneously from two retinas with the acquisition software included in commercial in vivo systems. Further, we demonstrate how to use this method in combination with pharmacological treatments that remove specific ERG components in order to dissect the function of certain retinal cell types.

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

Ex vivo ERG can be used to record electrical activity of retinal cells directly from isolated intact retinas of animals or humans. We demonstrate here how common in vivo ERG systems can be adapted for ex vivo ERG recordings in order to dissect the electrical activity of retinal cells.

Gleichzeitig<em&gt; Ex vivo</em&gt; Funktionsprüfung von zwei Netzhäute von<em&gt; In vivo</em&gt; Elektroretinogramm-System

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise ...

In Vivo Functional Brain Imaging Approach Based on Bioluminescent Calcium Indicator GFP-aequorin

Functional in vivo imaging has become a powerful approach to study the function and physiology of brain cells and structures of interest. Recently a new method of Ca2+-imaging using the bioluminescent reporter GFP-aequorin (GA) has been developed. This new technique relies on the fusion of the GFP and aequorin genes, producing a molecule capable of binding calcium and&#160;&#8212; with the addition of its cofactor coelenterazine &#8212; emitting bright light that can be monitored through a photon collector. Transgenic lines carrying the GFP-aequorin gene have been generated for both mice and Drosophila. In Drosophila, the GFP-aequorin gene has been placed under the control of the GAL4/UAS binary expression system allowing for targeted expression and imaging within the brain. This method has subsequently been shown to be capable of detecting both inward Ca2+-transients and Ca2+-released from inner stores. Most importantly it allows for a greater duration in continuous recording, imaging at greater depths within the brain, and recording at high temporal resolutions (up to 8.3 msec). Here we present the basic method for using bioluminescent imaging to record and analyze Ca2+-activity within the mushroom bodies, a structure central to learning and memory in the fly brain.

In Vivo Functional Brain Imaging Approach Based on Bioluminescent Calcium Indicator GFP-aequorin

Here we present a novel Ca2+-imaging approach using a bioluminescent reporter. This approach uses a fused construct GFP-aequorin which binds to Ca2+ and emits light, eliminating the need for light excitation. Significantly this method permits long continuous imaging, access to deep brain structures and high temporal resolution.

In Vivo Functional Brain Imaging Ansatz, der auf Bioluminescent Calciumindikator GFP-Aequorin

Functional in vivo imaging has become a powerful approach to study the function and physiology of brain cells and structures of interest. Recently a new ...

Utilizing Combined Methodologies to Define the Role of Plasma Membrane Delivery During Axon Branching and Neuronal Morphogenesis

During neural development, growing axons extend to multiple synaptic partners by elaborating axonal branches. Axon branching is promoted by extracellular guidance cues like netrin-1 and results in dramatic increases to the surface area of the axonal plasma membrane. Netrin-1-dependent axon branching likely involves temporal and spatial control of plasma membrane expansion, the components of which are supplied through exocytic vesicle fusion. These fusion events are preceded by formation of SNARE complexes, comprising a v-SNARE, such as VAMP2 (vesicle-associated membrane protein 2), and plasma membrane t-SNAREs, syntaxin-1 and SNAP25 (synaptosomal-associated protein 25). Detailed herein isa multi-pronged approach used to examine the role of SNARE mediated exocytosis in axon branching. The strength of the combined approach is data acquisition at a range of spatial and temporal resolutions, spanning from the dynamics of single vesicle fusion events in individual neurons to SNARE complex formation and axon branching in populations of cultured neurons. This protocol takes advantage of established biochemical approaches to assay levels of endogenous SNARE complexes and Total Internal Reflection Fluorescence (TIRF) microscopy of cortical neurons expressing VAMP2 tagged with a pH-sensitive GFP (VAMP2-pHlourin) to identify netrin-1 dependent changes in exocytic activity in individual neurons. To elucidate the timing of netrin-1-dependent branching, time-lapse differential interference contrast (DIC) microscopy of single neurons over the order of hours is utilized. Fixed cell immunofluorescence paired with botulinum neurotoxins that cleave SNARE machinery and block exocytosis demonstrates that netrin-1 dependent axon branching requires SNARE-mediated exocytic activity.

Light microscopy techniques coupled with biochemical assays elucidate the involvement of SNARE-mediated exocytosis in netrin-dependent axon branching. This combination of techniques permits identification of molecular mechanisms controlling axon branching and cell shape change.

Kombinierte Methodiken Verwendung der Rolle der Plasmamembran Lieferung Während Axon Branching und Neuronale Morphogenese zu definieren

During neural development, growing axons extend to multiple synaptic partners by elaborating axonal branches. Axon branching is promoted by extracellular ...

Combined Optogenetic and Freeze-fracture Replica Immunolabeling to Examine Input-specific Arrangement of Glutamate Receptors in the Mouse Amygdala

Freeze-fracture electron microscopy has been a major technique in ultrastructural research for over 40 years. However, the lack of effective means to study the molecular composition of membranes produced a significant decline in its use. Recently, there has been a major revival in freeze-fracture electron microscopy thanks to the development of effective ways to reveal integral membrane proteins by immunogold labeling. One of these methods is known as detergent-solubilized Freeze-fracture Replica Immunolabeling (FRIL).
The combination of the FRIL technique with optogenetics allows a correlated analysis of the structural and functional properties of central synapses. Using this approach it is possible to identify and characterize both pre- and postsynaptic neurons by their respective expression of a tagged channelrhodopsin and specific molecular markers. The distinctive appearance of the postsynaptic membrane specialization of glutamatergic synapses further allows, upon labeling of ionotropic glutamate receptors, to quantify and analyze the intrasynaptic distribution of these receptors. Here, we give a step-by-step description of the procedures required to prepare paired replicas and how to immunolabel them. We will also discuss the caveats and limitations of the FRIL technique, in particular those associated with potential sampling biases. The high reproducibility and versatility of the FRIL technique, when combined with optogenetics, offers a very powerful approach for the characterization of different aspects of synaptic transmission at identified neuronal microcircuits in the brain.
Here, we provide an example how this approach was used to gain insights into structure-function relationships of excitatory synapses at neurons of the intercalated cell masses of the mouse amygdala. In particular, we have investigated the expression of ionotropic glutamate receptors at identified inputs originated from the thalamic posterior intralaminar and medial geniculate nuclei. These synapses were shown to relay sensory information relevant for fear learning and to undergo plastic changes upon fear conditioning.

This article illustrates how the expression of neurotransmitter receptors can be quantified and the pattern analyzed at synapses with identified pre and postsynaptic elements using a combination of viral transduction of optogenetic tools and the freeze-fracture replica immunolabeling technique.

Kombinierte optogenetische und Gefrierbruch Replica Immunmarkierung Eingang spezifische Anordnung der Glutamate Receptors in der Maus Amygdala zu untersuchen

Freeze-fracture electron microscopy has been a major technique in ultrastructural research for over 40 years. However, the lack of effective means to ...