Questo lavoro è stato sostenuto dalla compagnia di assicurazione sulla vita &quot;AG2R-La Mondiale&quot;, Ecole des Neurosciences de Paris (PEV), l&#39;Agence Nationale de la Recherche &quot;ANR-09-Neur-004&quot;, nella cornice di &quot;ERA-NET NEURON &quot;del 7 ° PQ dalla Commissione Europea e la Fondazione Pasteur. Sebastien Wagner è stato sostenuto dalla Fondazione Letten.

1. Ottiche di calibrazione: misura LED di alimentazione <ol><li> Allegare una serie di LED di un dissipatore attivo raffreddato da una ventola e di apporre questa macchinetta LED / dissipatore di calore per una lente di collimazione. </li><li> Sostituire la lampada utilizzata in campo chiaro con illuminazione a LED / dissipatore / ventola / la lente. Questo apparecchio deve essere accuratamente posizionato in modo che il fascio collimato viaggia lungo un percorso lineare ottico verso la lente condensatore. Assicurarsi che il dissipatore di calore / ventola messa a terra di un terreno comune del sistema. </li><li> Guidare l&#39;array LED con un alimentatore in grado di dare impulsi ad alta risoluzione e la piazza di corrente. Questo alimentatore può essere controllato da un impulso TTL 5V proveniente da un generatore di impulsi. </li><li> Centrare il fascio collimato lungo il percorso della luce definita tra il diaframma di campo e la lente condensatore. Idealmente, il raggio LED leggermente riempire troppo il diaframma di campo completamente aperto. Di solito, un fascio collimato più strettamente LED riempire questa apertura di meno, e produrrà morpotenza e alle spese di uniformità. Nella nostra configurazione abbiamo aumentato l&#39;uniformità della luce, scegliendo una lente di collimazione che ha proiettato un&#39;immagine leggermente ampliato dell&#39;array LED suo piano coniugato al diaframma consenser. </li><li> Ottenere illuminazione Kohler, concentrandosi il condensatore in modo che l&#39;immagine del diaframma di campo (la membrana più vicino alla sorgente luminosa) è focalizzata sulla camera di slice (fig. 1). Un tessuto di carta sottile lente può fungere da schermo di proiezione per visualizzare l&#39;immagine focalizzata del diaframma di campo a profondità di altri. </li><li> Praticare una serie di fori di diametro noto in un materiale opaco. Posto uno di questi piccoli fori sopra il sensore ottico di un power-metro. Posizionare il misuratore di potenza sul palcoscenico del campione e al centro il misuratore di potenza sopra l&#39;immagine mirata del diaframma di campo semplicemente spostando il misuratore di potenza fino a quando non dà una lettura massima. Apporre il misuratore di potenza in questa posizione. </li><li> Aprire completamente tutte le aperture (diaframma e aperaturediaframma di campo). Sistematicamente spostare l&#39;allegato fetta camera / misuratore di potenza rispetto al percorso della luce ottica e calcolare l&#39;uniformità della potenza ottica all&#39;interno dell&#39;area illuminata. Costruire la trama uniformità per il sistema. Se il microscopio è correttamente configurato con illuminazione Kohler centrata a fuoco l&#39;obiettivo, la potenza massima dovrebbe essere direttamente sotto l&#39;obiettivo, e le regioni al di fuori di questo è opportuno concentrarsi ora ricevere una quantità nota di potenza secondo la trama uniformità. </li><li> Per ogni dimensione del foro stenopeico, costruire una curva standard di potenza ottica vs superficie foro stenopeico. Regolando la corrente di ingresso alla matrice di LED, producono questa curva a diversi livelli di potenza e di ogni curva di calcolare la potenza per mm2. Se l&#39;array LED deve essere utilizzato per l&#39;ottica patch, assicurarsi di introdurre elementi ottici necessari per l&#39;applicazione di patch (condensatori, punte di spillo e filtri) per sapere quanta luce viene trasmessa sotto illuminazione patch. </li><li> Sfogliando il misuratore di potenzafaccia l&#39;obiettivo, calcolare l&#39;intensità di illuminazione a 470nm quando la lampada al mercurio è accesa. </li><li> Aggiungere una fetta vivere alla camera, e ricostruire le curve standard per determinare la potenza della luce trasmessa attraverso il tessuto cerebrale di scattering. </li></ol> 2. Procedura di affettare e Elettrofisiologia Parte A: Preparazione Slice <ol><li> Anestetizzare (60 mg / kg di ketamina e 2mg/kg xilazina) e decapitare il mouse. Sezionare il cervello artificiale liquido cerebro-spinale (ACSF, in mm: 124 NaCl, 3 KCl, 1,3 MgSO 4, 26 NaHCO 3, 1,25 NaHPO 4, 20 di glucosio, 2 CaCl 2; ~ 310mOsm, pH 7,4, quando bolle con un misto di 95% O2 e 5% di CO2 5,1), facendo attenzione a non danneggiare i bulbi olfattivi. Separare i due emisferi e il luogo su agar con la superficie ventrale anche con un bordo (per le sezioni orizzontali). </li><li> Agar e la colla superficie dorsale di ogni emisfero corticale alla vibrAtome mandrino, e lentamente riempire la vasca con ghiaccio freddo ACSF. Fetta dalla superficie ventrale in 300 sezioni micron, il trasferimento di ogni sezione per riscaldato (34-36 ° C) e ossigenato ACSF, permettendo loro di recuperare per 30-45 minuti. </li></ol> Parte B: Misura Patch sciolti della soglia di Spike <ol start="3"><li> Dopo aver portato le fette a temperatura ambiente per 30 minuti, delicatamente una fetta nella camera di registrazione della Camera microscopio sotto perfusione costante di ACSF ossigenato. A rischio di stimolare eccessivamente ChR2 neuroni infetti, la presenza di EYFP-ChR2 può essere confermata in epifluorescenza (fig. 2a) </li><li> Tirare elettrodi di vetro su un estrattore pipetta (Sutter P-97). Riempi questo elettrodo con ACSF. Quando nel bagno ACSF la resistenza punta dovrebbe essere tra 7-10 MOhm. </li><li> Sotto illuminazione fluorescente, individuare nella fetta un sano ChR2-EYFP con morfologia dei neuroni maturi. Anche individuare soma questo neurone in ottica di patch. </li><li> Con la luce a pressione positiva passa attraverso l&#39;elettrodo, abbassare l&#39;elettrodo di patch verso il neurone identificato fluorescente. Quando il contatto membrana è realizzata, in modo rapido rilascio pressione positiva e applicare una piccola quantità e breve di aspirazione attraverso la punta. Un giga ohm sigillo dovrebbe essere fatta tra la membrana plasmatica e le pareti dell&#39;elettrodo patch. </li><li> Anche se un giga-sigillo non si forma, se l&#39;elettrodo è sufficientemente vicino ad una attività neuronale fluorescente spiking dovrebbe produrre un potenziale misurabile campo locale. Attivare ChR2 in questo neurone facendo lampeggiare diverse dosi di luce. Perché la luce-dose è una funzione sia di LED di potenza e durata, calcolare quanta luce è necessaria per evocare un potenziale d&#39;azione a poteri diversi e durate (Fig. 2b). Anche osservare quanto si verifica in spiking illuminazione lampada al mercurio. </li></ol> 3. Rappresentante dei risultati: Sul nostro microscopio (Olympus BX51WI), i nostri LED èn linea con 2 aperture e una lente condensatore, mantenendo così il percorso della luce originale del preinstallato lampada ad arco. Con la chiusura sia il diaframma di campo e il diaframma aperature, possiamo ottenere contrasto brightfield sufficiente per la registrazione patch clamp (fig. 1b). Con tutti i diaframmi completamente aperti esponiamo la fetta di potenza luminosa massima per channelrhodopsin attivazione (fig. 1a). Sul nostro microscopio, questa configurazione patch produce luce densità che è circa tre ordini di grandezza inferiore alla densità massima a pieno campo (4,1 μW / mm 2 rispetto a 6,88 mW / mm 2). Vediamo etichettatura robusto di adulti nati granuli bulbo olfattivo e neuroni periglomerular settimane dopo l&#39;infezione lentivirali di migrazione neuroblasti nel flusso migratorio rostrale (fig. 2a) A-patch allentato la registrazione da un unico adulto-nato ChR2-EYFP esprimere cellule dei granuli indica che a 5 ms stimolazione massimaum di potenza (6,88 mW / mm 2) è sufficiente a evocare spiking (Fig. 2b). Dal livello di espressione varia tra le cellule, la quantità di luce che passa la soglia di picco potrà variare e dovrebbe essere descritti statisticamente per ciascun tipo di cellula di interesse. <img src="/files/ftp_upload/3379/3379fig1.jpg" alt="Figura 1" /> Figura 1. LED di configurazione degli array di pieno campo fotostimolazione e patch-clamp elettrofisiologia fetta. Per attivare channelrhodopsin (ChR2) si proiettano un fascio collimato attraverso aperture di nuovo aperto e ottica condensatore (a). Questa configurazione può essere modificata in alto contrasto ottica patch attraverso la piena chiudendo il diaframma di campo e modulando la larghezza del diaframma di campo (b). Abbreviazioni: a. ventola, dissipatore b., c. serie di LED, d. collimazione obiettivo, e. specchio, diaframma di campo f., g. diaframma, lente condensatrice h., i. sample stadio, j. obiettivo. <img src="/files/ftp_upload/3379/3379fig2.jpg" alt="Figura 2" /> Figura 2. Immagine di una fetta 300μm orizzontale di bulbo olfattivo di patch clamp e con tutto il campo fotostimolazione (a). Lentivirally infetti adulti nati cellule granulari esprimono ChR2-EYFP si può vedere si irradiano dal centro del bulbo olfattivo. La luce-dose necessaria per evocare spiking si possono trovare aumentando la durata del flash LED (b). La soglia per questa cella dei granuli è stato 5ms alla massima intensità LED (2.43mW/mm 2). Scala in (a) = 500μm, scala in (b) = 50 ms.

<ol>
	<li>Nissant, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adult+neurogenesis+promotes+synaptic+plasticity+in+the+olfactory+bulb.">Adult neurogenesis promotes synaptic plasticity in the olfactory bulb.</a> Nature Neuroscience. 12, 728-730 (2009).</li><li>Apicella, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pyramidal+Cells+in+Piriform+Cortex+Receive+Convergent+Input+from+Distinct+Olfactory+Bulb+Glomeruli.">Pyramidal Cells in Piriform Cortex Receive Convergent Input from Distinct Olfactory Bulb Glomeruli.</a> Journal of Neuroscience. 30, 14255-14260 (2010).</li><li>Boyden, E. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=genetically+targeted+optical+control+of+neural+activity.">genetically targeted optical control of neural activity.</a> Nature. 8, 1263-1263 (2005).</li><li>Bardy, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=where+new+inhibitory+neurons+release+neurotransmitters+in+the+adult+olfactory+bulb.">where new inhibitory neurons release neurotransmitters in the adult olfactory bulb.</a> The Journal of Neuroscience. 30, 17023-17034 (2010).</li><li>Grubb, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+maturation+of+the+first+synapse+in+olfaction:+development+and+adult+neurogenesis.">Functional maturation of the first synapse in olfaction: development and adult neurogenesis.</a> The Journal of neuroscience. 28, 2919-2932 (2008).</li><li>Zhang, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Circuit-breakers:+optical+technologies+for+probing+neural+signals+and+systems.">Circuit-breakers: optical technologies for probing neural signals and systems.</a> Nature reviews. Neuroscience. 8, 577-581 (2007).</li><li>Grossman, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multi-site+optical+excitation+using+ChR2+and+micro-LED+array.">Multi-site optical excitation using ChR2 and micro-LED array.</a> Journal of neural engineering. 7, 16004-16004 (2010).</li><li>Dhawale, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-redundant+odor+coding+by+sister+mitral+cells+revealed+by+light+addressable+glomeruli+in+the+mouse.">Non-redundant odor coding by sister mitral cells revealed by light addressable glomeruli in the mouse.</a> Nature neuroscience. 13, 1404-1412 (2010).</li><li>Weick, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+control+of+transplantable+human+ESC-derived+neurons+via+optogenetic+targeting.">Functional control of transplantable human ESC-derived neurons via optogenetic targeting.</a> Stem cells. 28, 2008-2016 (2010).</li><li>Toni, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurons+born+in+the+adult+dentate+gyrus+form+functional+synapses+with+target+cells.">Neurons born in the adult dentate gyrus form functional synapses with target cells.</a> Nature Neuroscience. 11, 901-907 (2008).</li><li>Grubb, M. S., Burrone, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Channelrhodopsin-2+Localised+to+the+Axon+Initial+Segment.">Channelrhodopsin-2 Localised to the Axon Initial Segment.</a> PLoS ONE. 5, e13761-e13761 .</li><li>Tye, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amygdala+circuitry+mediating+reversible+and+bidirectional+control+of+anxiety.">Amygdala circuitry mediating reversible and bidirectional control of anxiety.</a> Nature. 471, 358-362 (2011).</li></ol>

Nessun conflitto di interessi dichiarati.

Ultimi anni hanno visto un&#39;esplosione della popolarità di strumenti per la ricerca neuroscientifica optogenetic 6. Di conseguenza, è sempre più importante per abbassare la barriera di ingresso per i laboratori che vogliono iniziare a utilizzare questi nuovi strumenti. Qui descriviamo come condurre un riadattamento semplice ed economica e la calibrazione di un convenzionale impianto di patch-clamp in modo che possa farlo a pieno campo stimolazione ottica di channelrhodopsin che esprimono i neuroni. In p...

<table border="1">
	<tbody>
		<tr>
			<td>Material</td>
			<td>Type</td>
			<td>Company</td>
			<td>Catalogue No.</td>
		</tr>
		<tr>
			<td>Ketamine</td>
			<td>100 mg/ml</td>
			<td>Imalg&egrave;ne 1000</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Xylazine</td>
			<td>2%</td>
			<td>Rompun</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>&nbps;</td>
			<td>Sigma </td>
			<td>S5886</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>&nbsp;</td>
			<td>Sigma </td>
			<td>P5405</td>
		</tr>
		<tr>
			<td>MgSO4</td>
			<td>&nbsp;</td>
			<td>Sigma </td>
			<td>M1880</td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>&nbsp;</td>
			<td>Sigma </td>
			<td>S5761</td>
		</tr>
		<tr>
			<td>NaHPO4</td>
			<td>&nbsp;</td>
			<td>Sigma </td>
			<td>S5011</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>&nbsp;</td>
			<td>Sigma </td>
			<td>G7021</td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>&nbsp;</td>
			<td>Sigma </td>
			<td>C7902</td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>&nbsp;</td>
			<td>Sigma </td>
			<td>A9539</td>
		</tr>
		<tr>
			<td>Pipette Puller</td>
			<td>P-97</td>
			<td>Sutter</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Glass Capillaries</td>
			<td>1.5 mm O.D./1.17 mm I.D.</td>
			<td>Harvard Apparatus</td>
			<td>GC150T-10</td>
		</tr>
		<tr>
			<td>LED array</td>
			<td>&nbsp;</td>
			<td>Bridgelux</td>
			<td>BXRA-C2000</td>
		</tr>
		<tr>
			<td>Collimating lens</td>
			<td>40 mm beam diameter</td>
			<td>Thor Labs</td>
			<td>LEDC1</td>
		</tr>
		<tr>
			<td>Power supply</td>
			<td>2.8 amp</td>
			<td>A1W Electronik</td>
			<td>HKO2800</td>
		</tr>
		<tr>
			<td>Optical power meter</td>
			<td>&nbsp;</td>
			<td>Thor Labs</td>
			<td>PM 100</td>
		</tr>
		<tr>
			<td>Heatsink </td>
			<td>Silent Boost K8</td>
			<td>Thermaltake</td>
			<td>A1838</td>
		</tr>
		<tr>
			<td>Fan</td>
			<td>Silent Boost K8</td>
			<td>Thermaltake</td>
			<td>A1838</td>
		</tr>
		<tr>
			<td>Vibratome</td>
			<td>&nbsp;</td>
			<td>Leica</td>
			<td>VT1200S</td>
		</tr>
	</tbody>
</table>

using affordable led arrays for photo-stimulation of neurons

Elettrofisiologia fetta standard ha permesso ai ricercatori di sondare i singoli componenti dei circuiti neurali registrando le risposte elettriche di singole cellule in risposta a elettrica o farmacologica 1,2 manipolazioni. Con l&#39;invenzione di metodi per controllare visivamente i neuroni geneticamente mirata (optogenetics), i ricercatori hanno ora un livello senza precedenti di controllo su gruppi specifici di neuroni nella preparazione fetta standard. In particolare, fotosensibile channelrhodopsin-2 (ChR2) permette ai ricercatori di attivare i neuroni con la luce 3,4. Grazie alla combinazione di calibrazione accurata basata su LED di fotostimolazione ChR2 con elettrofisiologia fetta standard, siamo in grado di riconoscere con maggior dettaglio il ruolo di adulto-nato interneuroni nel bulbo olfattivo, il primo relè centrale del sistema olfattivo. Utilizzando l&#39;espressione virale di ChR2-YFP specificamente in neuroni adulti nati, siamo in grado di controllare selettivamente i giovani adulti nati i neuroni in un ambiente di un vecchiod neuroni maturi. Il nostro controllo ottico utilizza un sistema semplice e poco costoso a LED, e si mostra come questo sistema può essere calibrato per capire quanta luce è necessaria per evocare spiking attività in singoli neuroni. Quindi, brevi lampi di luce blu può controllare a distanza il modello lancio di ChR2-trasdotte neonato.

Watch this Scientific Journal Video about Using Affordable LED Arrays for Photo-Stimulation of Neurons at JoVE.com

Using Affordable LED Arrays for Photo-Stimulation of Neurons

Adulti-nato neuroni che esprimono ChR2 può essere manipolata in preparati fetta elettrofisiologici al fine di esaminare il loro contributo verso la funzione olfattiva di circuiti neurali.

Utilizzando conveniente array LED per la foto-stimolazione dei neuroni

Standard slice electrophysiology has allowed researchers to probe individual components of neural circuitry by recording electrical responses of single ...

using-affordable-led-arrays-for-photo-stimulation-of-neurons

Research

JoVE Journal

Neuroscience

18.5K Views.  Institut Pasteur and Centre National de la Recherche Scientifique (CNRS). Adulti-nato neuroni che esprimono ChR2 può essere manipolata in preparati fetta elettrofisiologici al fine di esaminare il loro contributo verso la funzione olfattiva di circuiti neurali.

Video: Using Affordable LED Arrays for Photo-Stimulation of Neurons

Scalable Fluidic Injector Arrays for Viral Targeting of Intact 3-D Brain Circuits

Our understanding of neural circuits--how they mediate the computations that subserve sensation, thought, emotion, and action, and how they are corrupted in neurological and psychiatric disorders--would be greatly facilitated by a technology for rapidly targeting genes to complex 3-dimensional neural circuits, enabling fast creation of "circuit-level transgenics." We have recently developed methods in which viruses encoding for light-sensitive proteins can sensitize specific cell types to millisecond-timescale activation and silencing in the intact brain. We here present the design and implementation of an injector array capable of delivering viruses (or other fluids) to dozens of defined points within the 3-dimensional structure of the brain (Figure. 1A, 1B). The injector array comprises one or more displacement pumps that each drive a set of syringes, each of which feeds into a polyimide/fused-silica capillary via a high-pressure-tolerant connector. The capillaries are sized, and then inserted into, desired locations specified by custom-milling a stereotactic positioning board, thus allowing viruses or other reagents to be delivered to the desired set of brain regions. To use the device, the surgeon first fills the fluidic subsystem entirely with oil, backfills the capillaries with the virus, inserts the device into the brain, and infuses reagents slowly (&lt;0.1 microliters/min). The parallel nature of the injector array facilitates rapid, accurate, and robust labeling of entire neural circuits with viral payloads such as optical sensitizers to enable light-activation and silencing of defined brain circuits. Along with other technologies, such as optical fiber arrays for light delivery to desired sets of brain regions, we hope to create a toolbox that enables the systematic probing of causal neural functions in the intact brain. This technology may not only open up such systematic approaches to circuit-focused neuroscience in mammals, and facilitate labeling of brain regions in large animals such as non-human primates, but may also open up a clinical translational path for cell-specific optical control prosthetics, whose precision may enable improved treatment of intractable brain disorders. Finally, such devices as described here may facilitate precisely-timed fluidic delivery of other payloads, such as stem cells and pharmacological agents, to 3-dimensional structures, in an easily user-customizable fashion.

Controlling and analyzing neural circuits in vivo would be facilitated by a technology for delivery of viruses and other reagents to desired 3-dimensional sets of brain regions. We demonstrate customized fluidic injector array fabrication, and delivery of virally-encoded optical sensitizers, enabling optical manipulation of complex brain circuits.

Gli array scalabile fluidico Iniettore per Viral targeting di intatto 3-D circuiti cerebrali

Our understanding of neural circuits--how they mediate the computations that subserve sensation, thought, emotion, and action, and how they are corrupted ...

Ricerca

Neuroscienze

Quantitative Analysis of Synaptic Vesicle Pool Replenishment in Cultured Cerebellar Granule Neurons using FM Dyes

After neurotransmitter release in central nerve terminals, SVs are rapidly retrieved by endocytosis. Retrieved SVs are then refilled with neurotransmitter and rejoin the recycling pool, defined as SVs that are available for exocytosis1,2. The recycling pool can generally be subdivided into two distinct pools - the readily releasable pool (RRP) and the reserve pool (RP). As their names imply, the RRP consists of SVs that are immediately available for fusion while RP SVs are released only during intense stimulation1,2. It is important to have a reliable assay that reports the differential replenishment of these SV pools in order to understand 1) how SVs traffic after different modes of endocytosis (such as clathrin-dependent endocytosis and activity-dependent bulk endocytosis) and 2) the mechanisms controlling the mobilisation of both the RRP and RP in response to different stimuli.
FM dyes are routinely employed to quantitatively report SV turnover in central nerve terminals3-8. They have a hydrophobic hydrocarbon tail that allows reversible partitioning in the lipid bilayer, and a hydrophilic head group that blocks passage across membranes. The dyes have little fluorescence in aqueous solution, but their quantum yield increases dramatically when partitioned in membrane9. Thus FM dyes are ideal fluorescent probes for tracking actively recycling SVs. The standard protocol for use of FM dye is as follows. First they are applied to neurons and are taken up during endocytosis (Figure 1). After non-internalised dye is washed away from the plasma membrane, recycled SVs redistribute within the recycling pool. These SVs are then depleted using unloading stimuli (Figure 1). Since FM dye labelling of SVs is quantal10, the resulting fluorescence drop is proportional to the amount of vesicles released. Thus, the recycling and fusion of SVs generated from the previous round of endocytosis can be reliably quantified.
Here, we present a protocol that has been modified to obtain two additional elements of information. Firstly, sequential unloading stimuli are used to differentially unload the RRP and the RP, to allow quantification of the replenishment of specific SV pools. Secondly, each nerve terminal undergoes the protocol twice. Thus, the response of the same nerve terminal at S1 can be compared against the presence of a test substance at phase S2 (Figure 2), providing an internal control. This is important, since the extent of SV recycling across different nerve terminals is highly variable11.
Any adherent primary neuronal cultures may be used for this protocol, however the plating density, solutions and stimulation conditions are optimised for cerebellar granule neurons (CGNs)12,13.

A live fluorescence imaging technique to quantify the replenishment and mobilisation of specific synaptic vesicle (SV) pools in central nerve terminals is described. Two rounds of SV recycling are monitored in the same nerve terminals providing an internal control.

Analisi quantitativa di Replenishment pool delle vescicole sinaptiche in colture di neuroni granuli cerebellari utilizzando coloranti FM

After neurotransmitter release in central nerve terminals, SVs are rapidly retrieved by endocytosis.  Retrieved SVs are then refilled with ...

Lateral Diffusion and Exocytosis of Membrane Proteins in Cultured Neurons Assessed using Fluorescence Recovery and Fluorescence-loss Photobleaching

Membrane proteins such as receptors and ion channels undergo active trafficking in neurons, which are highly polarised and morphologically complex. This directed trafficking is of fundamental importance to deliver, maintain or remove synaptic proteins.
Super-ecliptic pHluorin (SEP) is a pH-sensitive derivative of eGFP that has been extensively used for live cell imaging of plasma membrane proteins1-2. At low pH, protonation of SEP decreases photon absorption and eliminates fluorescence emission. As most intracellular trafficking events occur in compartments with low pH, where SEP fluorescence is eclipsed, the fluorescence signal from SEP-tagged proteins is predominantly from the plasma membrane where the SEP is exposed to a neutral pH extracellular environment. When illuminated at high intensity SEP, like every fluorescent dye, is irreversibly photodamaged (photobleached)3-5. Importantly, because low pH quenches photon absorption, only surface expressed SEP can be photobleached whereas intracellular SEP is unaffected by the high intensity illumination6-10. 
FRAP (fluorescence recovery after photobleaching) of SEP-tagged proteins is a convenient and powerful technique for assessing protein dynamics at the plasma membrane. When fluorescently tagged proteins are photobleached in a region of interest (ROI) the recovery in fluorescence occurs due to the movement of unbleached SEP-tagged proteins into the bleached region. This can occur via lateral diffusion and/or from exocytosis of non-photobleached receptors supplied either by de novo synthesis or recycling (see Fig. 1). The fraction of immobile and mobile protein can be determined and the mobility and kinetics of the diffusible fraction can be interrogated under basal and stimulated conditions such as agonist application or neuronal activation stimuli such as NMDA or KCl application8,10. 
We describe photobleaching techniques designed to selectively visualize the recovery of fluorescence attributable to exocytosis. Briefly, an ROI is photobleached once as with standard FRAP protocols, followed, after a brief recovery, by repetitive bleaching of the flanking regions. This 'FRAP-FLIP' protocol, developed in our lab, has been used to characterize AMPA receptor trafficking at dendritic spines10, and is applicable to a wide range of trafficking studies to evaluate the intracellular trafficking and exocytosis.

This report describes the use of live cell imaging and photobleach techniques to determine the surface expression, transport pathways and trafficking kinetics of exogenously expressed, pH-sensitive GFP-tagged proteins at the plasma membrane of neurons.

Diffusione laterale e esocitosi delle proteine ​​di membrana in neuroni in coltura valutata utilizzando Recovery fluorescenza e fluorescenza-loss photobleaching

Membrane proteins such as receptors and ion channels undergo active trafficking in neurons, which are highly polarised and morphologically complex. This ...

Imaging Dendritic Spines of Rat Primary Hippocampal Neurons using Structured Illumination Microscopy

Dendritic spines are protrusions emerging from the dendrite of a neuron and represent the primary postsynaptic targets of excitatory inputs in the brain. Technological advances have identified these structures as key elements in neuron connectivity and synaptic plasticity. The quantitative analysis of spine morphology using light microscopy remains an essential problem due to technical limitations associated with light's intrinsic refraction limit. Dendritic spines can be readily identified by confocal laser-scanning fluorescence microscopy. However, measuring subtle changes in the shape and size of spines is difficult because spine dimensions other than length are usually smaller than conventional optical resolution fixed by light microscopy's theoretical resolution limit of 200 nm.
Several recently developed super resolution techniques have been used to image cellular structures smaller than the 200 nm, including dendritic spines. These techniques are based on classical far-field operations and therefore allow the use of existing sample preparation methods and to image beyond the surface of a specimen. Described here is a working protocol to apply super resolution structured illumination microscopy (SIM) to the imaging of dendritic spines in primary hippocampal neuron cultures. Possible applications of SIM overlap with those of confocal microscopy. However, the two techniques present different applicability. SIM offers higher effective lateral resolution, while confocal microscopy, due to the usage of a physical pinhole, achieves resolution improvement at the expense of removal of out of focus light. In this protocol, primary neurons are cultured on glass coverslips using a standard protocol, transfected with DNA plasmids encoding fluorescent proteins and imaged using SIM. The whole protocol described herein takes approximately 2 weeks, because dendritic spines are imaged after 16-17 days in vitro, when dendritic development is optimal. After completion of the protocol, dendritic spines can be reconstructed in 3D from series of SIM image stacks using specialized software.

This article describes a working protocol to image dendritic spines from hippocampal neurons in vitro using Structured Illumination Microscopy (SIM). Super-resolution microscopy using SIM provides image resolution significantly beyond the light diffraction limit in all three spatial dimensions, allowing the imaging of individual dendritic spines with improved detail.

Imaging spine dendritiche di Rat Primaria neuroni dell&#39;ippocampo utilizzando Structured Illumination Microscopy

Dendritic spines are protrusions emerging from the dendrite of a neuron and represent the primary postsynaptic targets of excitatory inputs in the brain. ...

Production and Isolation of Axons from Sensory Neurons for Biochemical Analysis Using Porous Filters

Neuronal axons use specific mechanisms to mediate extension, maintain integrity, and induce degeneration. An appropriate balance of these events is required to shape functional neuronal circuits. The protocol described here explains how to use cell culture inserts bearing a porous membrane (filter) to obtain large amounts of pure axonal preparations suitable for examination by conventional biochemical or immunocytochemical techniques. The functionality of these filter inserts will be demonstrated with models of developmental pruning and Wallerian degeneration, using explants of embryonic dorsal root ganglion. Axonal integrity and function is compromised in a wide variety of neurodegenerative pathologies. Indeed, it is now clear that axonal dysfunction appears much earlier in the course of the disease than neuronal soma loss in several neurodegenerative diseases, indicating that axonal-specific processes are primarily targeted in these disorders. By obtaining pure axonal samples for analysis by molecular and biochemical techniques, this technique has the potential to shed new light into mechanisms regulating the physiology and pathophysiology of axons. This in turn will have an impact in our understanding of the processes that drive degenerative diseases of the nervous system.

This article describes a neuronal culture system that can be used to obtain large quantities of pure axonal samples for biochemical and immunocytochemical analyses. This technique will allow an improved understanding of normal axonal physiology and signaling pathways leading to neurodegeneration.

Produzione e isolamento degli assoni dai neuroni sensoriali per l&#39;analisi biochimica Uso dei filtri porosi

Neuronal axons use specific mechanisms to mediate extension, maintain integrity, and induce degeneration. An appropriate balance of these events is ...

External Excitation of Neurons Using Electric and Magnetic Fields in One- and Two-dimensional Cultures

A neuron will fire an action potential when its membrane potential exceeds a certain threshold. In typical activity of the brain, this occurs as a result of chemical inputs to its synapses. However, neurons can also be excited by an imposed electric field. In particular, recent clinical applications activate neurons by creating an electric field externally. It is therefore of interest to investigate how the neuron responds to the external field and what causes the action potential. Fortunately, precise and controlled application of an external electric field is possible for embryonic neuronal cells that are excised, dissociated and grown in cultures. This allows the investigation of these questions in a highly reproducible system.
In this paper some of the techniques used for controlled application of external electric field on neuronal cultures are reviewed. The networks can be either one dimensional, i.e. patterned in linear forms or allowed to grow on the whole plane of the substrate, and thus two dimensional. Furthermore, the excitation can be created by the direct application of electric field via electrodes immersed in the fluid (bath electrodes) or by inducing the electric field using the remote creation of magnetic pulses.

Neuronal cultures are a good model for studying emerging brain stimulation techniques via their effect on single neurons or a population of neurons. Presented here are different methods for stimulation of patterned neuronal cultures by an electric field produced directly by bath electrodes or induced by a time-varying magnetic field.

Eccitazione esterna dei neuroni Usando campi elettrici e magnetici in mono e culture bidimensionali

A neuron will fire an action potential when its membrane potential exceeds a certain threshold. In typical activity of the brain, this occurs as a result ...

Live Images of GLUT4 Protein Trafficking in Mouse Primary Hypothalamic Neurons Using Deconvolution Microscopy

Type 2 diabetes mellitus (T2DM) is a global health crisis which is characterized by insulin signaling impairment and chronic inflammation in peripheral tissues. The hypothalamus in the central nervous system (CNS) is the control center for energy and insulin signal response regulation. Chronic inflammation in peripheral tissues and imbalances of certain chemokines (such as CCL5, TNF&#945;, and IL-6) contribute to diabetes and obesity. However, the functional mechanism(s) connecting chemokines and hypothalamic insulin signal regulation still remain unclear.
In vitro primary neuron culture models are convenient and simple models which can be used to investigate insulin signal regulation in hypothalamic neurons. In this study, we introduced exogeneous GLUT4 protein conjugated with GFP (GFP-GLUT4) into primary hypothalamic neurons to track GLUT4 membrane translocation upon insulin stimulation. Time-lapse images of GFP-GLUT4 protein trafficking were recorded by deconvolution microscopy, which allowed users to generate high-speed, high-resolution images without damaging the neurons significantly while conducting the experiment. The contribution of CCR5 in insulin regulated GLUT4 translocation was observed in CCR5 deficient hypothalamic neurons, which were isolated and cultured from CCR5 knockout mice. Our results demonstrated that the GLUT4 membrane translocation efficiency was reduced in CCR5 deficient hypothalamic neurons after insulin stimulation.

This protocol describes a technique for observation of real-time Green Fluorescence Protein (GFP) tagged Glucose Transporter 4 (GLUT4) protein trafficking upon insulin stimulation and characterization of the biological role of CCR5 in the insulin&#8211;GLUT4 signaling pathway with Deconvolution Microscopy.

Immagini in diretta della proteina GLUT4 tratta di neuroni ipotalamici primario del Mouse usando la microscopia di Deconvolution

Type 2 diabetes mellitus (T2DM) is a global health crisis which is characterized by insulin signaling impairment and chronic inflammation in peripheral ...

An In Vitro Model for Studying Tau Aggregation Using Lentiviral-mediated Transduction of Human Neurons

Aberrant aggregation of the protein tau is pathogenically involved in a number of neurodegenerative diseases, including Alzheimer&#8217;s disease (AD). Although mouse models of tauopathy have provided a valuable resource for investigating the neurotoxic mechanisms of aggregated tau, it is becoming increasingly apparent that, due to interspecies differences in neurophysiology, the mouse brain is unsuitable for modeling the human condition. Advances in cell culture methods have made human neuronal cultures accessible for experimental use in vitro and have aided in the development of neurotherapeutics. However, despite the adaptation of human neuronal cell cultures, in vitro models of human tauopathy are not yet widely available. This protocol describes a cellular model of tau aggregation in which human neurons are transduced with lentiviral-derived vectors that code for pathogenically mutated tau fused to a yellow fluorescent protein (YFP) reporter. Transduced cultures produce tau aggregates that stain positively for thioflavin and display markers of neurotoxicity, such as decreased axonal length and increased lysosomal volume. This procedure may be a useful and cost-effective model for studying human tauopathies.

This protocol details a procedure in which human neuronal cultures are transduced with lentiviral constructs coding for mutant human tau. Transduced cultures display tau aggregates and associated pathologies.

Un modello in vitro per lo studio dell'aggregazione Tau utilizzando la trasduzione dei neuroni umani mediata da lentivirali

Aberrant aggregation of the protein tau is pathogenically involved in a number of neurodegenerative diseases, including Alzheimer&#8217;s disease (AD). ...

Chronic Implantation of Multiple Flexible Polymer Electrode Arrays

Simultaneous recordings from large populations of individual neurons across distributed brain regions over months to years will enable new avenues of scientific and clinical development. The use of flexible polymer electrode arrays can support long-lasting recording, but the same mechanical properties that allow for longevity of recording make multiple insertions and integration into a chronic implant a challenge. Here is a methodology by which multiple polymer electrode arrays can be targeted to a relatively spatially unconstrained set of brain areas.
The method utilizes thin-film polymer devices, selected for their biocompatibility and capability to achieve long-term and stable&#160;electrophysiologic recording interfaces. The resultant implant allows accurate and flexible targeting of anatomically distant regions, physical stability for months, and robustness to electrical noise. The methodology supports up to sixteen serially inserted devices across eight different anatomic targets. As previously demonstrated, the methodology is capable of recording from 1024 channels. Of these, the 512 channels in this demonstration used for single neuron recording yielded 375 single units distributed across six recording sites. Importantly, this method also can record single units for at least 160 days.
This implantation strategy, including temporarily bracing each device with a retractable silicon insertion shuttle, involves tethering of devices at their target depths to a skull-adhered plastic base piece that is custom-designed for each set of recording targets, and stabilization/protection of the devices within a silicone-filled, custom-designed plastic case. Also covered is the preparation of devices for implantation, and design principles that should guide adaptation to different combinations of brain areas or array designs.

Described below is a method for implantation of multiple polymer electrode arrays across anatomically distant brain regions for chronic electrophysiological recording in freely moving rats. Preparation and surgical implantation are described in detail, with emphasis on design principles to guide adaptation of these methods for use in other species.

Impianto cronico di più array di elettrodi polimerici flessibili

Simultaneous recordings from large populations of individual neurons across distributed brain regions over months to years will enable new avenues of ...

Stereotaxic Surgery for Implantation of Microelectrode Arrays in the Common Marmoset (Callithrix jacchus)

Marmosets (Callithrix jacchus) are small non-human primates that are gaining popularity in biomedical and preclinical research, including the neurosciences. Phylogenetically, these animals are much closer to humans than rodents. They also display complex behaviors, including a wide range of vocalizations and social interactions. Here, an effective stereotaxic neurosurgical procedure for implantation of recording electrode arrays in the common marmoset is described. This protocol also details the pre- and postoperative steps of animal care that are required to successfully perform such a surgery. Finally, this protocol shows an example of local field potential and spike activity recordings in a freely behaving marmoset 1 week after the surgical procedure. Overall, this method provides an opportunity to study the brain function in awake and freely behaving marmosets. The same protocol can be readily used by researchers working with other small primates. In addition, it can be easily modified to allow other studies requiring implants, such as stimulating electrodes, microinjections, implantation of optrodes or guide cannulas, or ablation of discrete tissue regions.

Stereotaxic Surgery for Implantation of Microelectrode Arrays in the Common Marmoset Callithrix jacchus

This work presents a protocol to perform a stereotaxic, neurosurgical implantation of&#160;microelectrode arrays in the common marmoset. This method specifically enables electrophysiological recordings in freely behaving animals but can be easily adapted to any other similar neurosurgical intervention in this species (e.g., cannula for drug administration or electrodes for brain stimulation).