Summary

Imaging Fibre serotoninergici nel midollo spinale mouse Uso del CHIAREZZA / Tecnica CUBIC

Published: February 26, 2016
doi:

Summary

Supraspinal projections are important for pain perception and other behaviors, and serotonergic fibers are one of these fiber systems. The present study focused on the application of the combined CLARITY/CUBIC protocol to the mouse spinal cord in order to investigate the termination of these serotonergic fibers.

Abstract

fibre lunghe che scendono verso il midollo spinale sono essenziali per la locomozione, percezione del dolore, e altri comportamenti. Il modello terminazione in fibra nel midollo spinale della maggior parte di questi sistemi in fibra non sono state esaminate a fondo in qualsiasi specie. fibre serotoninergici, che proiettano al midollo spinale, sono stati studiati nei ratti e opossum su sezioni istologiche e il loro significato funzionale è stata dedotta in base al loro modello di terminazione in fibra nel midollo spinale. Con lo sviluppo della chiarezza e tecniche cubica, è possibile studiare questo sistema di fibre e la sua distribuzione nel midollo spinale, che rischia di rivelare caratteristiche precedentemente sconosciuti di percorsi supraspinal serotoninergici. Qui, forniamo un protocollo dettagliato per l'imaging delle fibre serotoninergici nel topo midollo spinale utilizzando la nitidezza, associato e le tecniche cubi. Il metodo prevede la perfusione di un mouse con una soluzione idrogel e chiarificazione del tessuto con una combinzione di compensazione reagenti. tessuto del midollo spinale è stato eliminato in poco meno di due settimane, e la conseguente colorazione immunofluorescenza contro la serotonina è stata completata in meno di dieci giorni. Con un microscopio a fluorescenza multi-fotone, il tessuto è stato digitalizzato e l'immagine 3D è stata ricostruita utilizzando il software OsiriX.

Introduction

Supraspinal projections are responsible for the modulation of diverse behaviors such as pain perception. One of the projections carrying nociceptive information contains serotoninergic fibers, which originate from the hindbrain raphe and adjacent reticular nuclei1,2. Physiological and pharmacological studies have demonstrated an increased release of serotonin in the dorsal horn of the spinal cord after electrical stimulation of the raphe nuclei in the hindbrain3-5. In the rat and opossum, serotonergic raphespinal fibers have dense terminals, not only in the dorsal horn6-8, but also in the intermediate zone7,9,10, the ventral horn7,11, and even lamina 1012,13. There are no similar studies in the mouse. The present study aimed to map the termination pattern of serotonergic fibers arising from the hindbrain raphe nuclei and their adjacent reticular nuclei in the mouse spinal cord using the recently published CLARITY14 method and its modification – CUBIC15.

Conventional fluorescence or peroxidase immunohistochemistry of the spinal cord clearly shows the distribution of serotonergic fibers in the gray matter of the spinal cord in 30-40 µm thick cross-sections. However, this approach does not show the continuity of the serotonergic fiber tracts in the white matter and their collaterals in the gray matter. Although the 3D reconstruction of histological sections has advanced our knowledge of fiber tracts, it remains a challenge for histologists and anatomists to follow a single tract due to small distortions in the tissue caused by cutting. To circumvent this obstacle a number of researchers have developed various protocols for making the whole tissue structure transparent, and collecting an image of unaltered tissue in a single video file17-21. So far, the clear, lipid-exchanged, acrylamide-hybridized rigid, imaging/ immunostaining compatible, tissue hydrogel (CLARITY) technique, developed by Deisseroth’s group14,15, as well as CUBIC, developed by Susaki et al16 are the most successful. Since the publication of the protocols, many researchers have started using these techniques to investigate various aspects of biological tissues, including, not only the brain22-25, but also the heart, kidneys, intestine, and the lungs26,27.

By fixing the mouse spinal cord with the hydrogel solution (CLARITY) and clearing with the CUBIC reagents (which is a much faster method than that described by the original CLARITY protocol14,15), a spinal cord tissue block of 2-3 mm long was cleared within two weeks and immunofluorescence staining for serotonin completed in eight days. With just a combination of chemical agents, conventional immunohistochemistry can be used to create an image of individual fiber tracts in a 3D video file in approximately one month.

Protocol

Etica Dichiarazione: Tutte le procedure che coinvolgono soggetti animali seguono le linee guida del Comitato Animal Care and Ethics (ACEC) presso l'Università del New South Wales (il numero ACEC approvato è di 14 / 94A). 1. Preparazione del cavo del mouse trasparente spinale Preparazione di Ice Cold Hydrogel Soluzione Preparazione della soluzione di paraformaldeide al 16% (PFA) Aggiungere 16 g di polvere di paraformaldeide in 70 ml-pre riscaldato acqua dist…

Representative Results

Questa sezione mostra i risultati di anticorpi serotonina colorazione nel topo trasparente midollo spinale utilizzando una combinazione di chiarezza e protocolli cubi. Abbiamo dimostrato che le fibre serotoninergici sono presenti in tutti lamine del midollo spinale con una predominanza nella porzione ventrale del corno ventrale (Figura 1, vedi anche Video 1). Il tessuto di controllo non ha avuto fibre positive (risultato non è stato mostrato). Nel corno…

Discussion

Il protocollo descritto mostra come le fibre immagine serotoninergici nel topo midollo spinale con la chiarezza combinato e tecniche di cubi. Si introduce un processo di compensazione più veloce rispetto al protocollo di compensazione passiva sviluppato da Cheung et al. 14 e Tomer et al. 15 e permette il tessuto del midollo spinale per essere ben supportato dal idrogel durante compensazione.

Un passo importante durante la fissazione del mouse midollo …

Disclosures

The authors have nothing to disclose.

Acknowledgements

This work was supported by the Australian Research Council Centre of Excellence for Integrative Brain Function (ARC Centre Grant CE140100007), an NHMRC project grant (#1086643). Prof. George Paxinos is supported by a Senior Principal Research Fellow NHMRC grant (#1043626).

Materials

Photoinitiator VA044 Wako va-044/225-02111 http://www.wako-chem.co.jp/specialty/waterazo/VA-044.htm
40% acrylamide solution Bio Rad 161-0140 http://www.bio-rad.com/en-au/sku/161-0140-40-acrylamide-solution
2% Bis Solution Bio Rad 161-0142 http://www.bio-rad.com/en-au/sku/161-0142-2-bis-solution?parentCategoryGUID=5e7a4f31-879c-4d63-ba0b-82556a0ccf1d
paraformaldehyde Sigma 158127 http://www.sigmaaldrich.com/catalog/product/sial/158127?lang=en&region=AU
urea Merck Millipore 66612 http://www.merckmillipore.com/AU/en/product/Urea—CAS-57-13-6—Calbiochem,EMD_BIO-66612
N,N,N’,N’-tetrakis (2-hydroxypropyl) ethylenediamine Merck Millipore 821940 http://www.merckmillipore.com/AU/en/product/Ethylenediamine-N,N,N',N'-tetra-2-propanol,MDA_CHEM-821940
Triton-X 100 Merck Millipore 648462 http://www.merckmillipore.com/AU/en/product/TRITON®-X-100-Detergent—CAS-9002-93-1—Calbiochem,EMD_BIO-648462
sucrose Sigma S0389 http://www.sigmaaldrich.com/catalog/product/sigma/s0389?lang=en&region=AU
2,2’,2’’- nitrilotriethanol Merck Millipore 137002 http://www.merckmillipore.com/AU/en/product/Triethanolamine-(Trolamine),MDA_CHEM-137022
serotonin antibody Merck Millipore AB938 http://www.merckmillipore.com/AU/en/product/Anti-Serotonin-Antibody,MM_NF-AB938
goat anti rabbit IgG (H+L) Secondary Antibody, Alexa Fluor® 594 conjugate Life Technologies  A-11012 https://www.lifetechnologies.com/order/genome-database/antibody/Rabbit-IgG-H-L-Secondary-Antibody-Polyclonal/A-11012
multi-photon microscope Leica Leica TCS SP5 MP STED http://www.leica-microsystems.com/products/confocal-microscopes/details/product/leica-tcs-sp5-mp/

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Cite This Article
Liang, H., Schofield, E., Paxinos, G. Imaging Serotonergic Fibers in the Mouse Spinal Cord Using the CLARITY/CUBIC Technique. J. Vis. Exp. (108), e53673, doi:10.3791/53673 (2016).

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