Name: preparation of the rat vocal fold for neuromuscular analyses
Uploaded: 2020-05-15T14:45:00
Description: Watch this Scientific Journal Video about Preparation of the Rat Vocal Fold for Neuromuscular Analyses at JoVE.com

This research was supported by grants F31DC017053-01A1 (Lenell, PI) and K23DC014517 (Johnson, PI) from the National Institute on Deafness and other Communication Disorders of the National Institutes of Health.

This study was performed in compliance with the Institutional Animal Care and Use Committee of New York University School of Medicine.
1. Dissect rat larynx
<ol>
	<li>Euthanize rat according to the institutionally approved protocol. Shave the ventral neck from the mandible to manubrium and swab with alcohol to prevent fur contamination in the tissue specimens.</li>
	<li>Under a dissecting scope with 10x magnification excise the entire larynx by creating a midline neck incision with a scalpel...

<ol>
	<li>Connor, N. P., Suzuki, T., Lee, K., Sewall, G. K., Heisey, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuromuscular+junction+changes+in+aged+rat+thyroarytenoid+muscle.">Neuromuscular junction changes in aged rat thyroarytenoid muscle.</a> Annals of Otology, Rhinology and Laryngology. 111 (7), 579-586 (2002).</li><li>Suzuki, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Age-Related+Alterations+in+Myosin+Heavy+Chaing+Isoforms+in+Rat+Intrinsic+Laryngeal+Muscles.">Age-Related Alterations in Myosin Heavy Chaing Isoforms in Rat Intrinsic Laryngeal Muscles.</a> Annals of Otology, Rhinology and Laryngology. 111 (11), 962 (2002).</li><li>Johnson, A. M., Grant, L. M., Schallert, T., Ciucci, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+Rat+50-kHz+Ultrasonic+Vocalizations+During+Dopamine+Denervation+and+Aging:+Relevance+to+Neurodegeneration.">Changes in Rat 50-kHz Ultrasonic Vocalizations During Dopamine Denervation and Aging: Relevance to Neurodegeneration.</a> Current Neuropharmacology. 13 (2), 211-219 (2015).</li><li>Wright, J. M., Gourdon, J. C., Clarke, P. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+multiple+call+categories+within+the+rich+repertoire+of+adult+rat+50-kHz+ultrasonic+vocalizations:+effects+of+amphetamine+and+social+context.">Identification of multiple call categories within the rich repertoire of adult rat 50-kHz ultrasonic vocalizations: effects of amphetamine and social context.</a> Psychopharmacology. 211 (1), 1-13 (2010).</li><li>Bowers, J. M., Perez-Pouchoulen, M., Edwards, N. S., McCarthy, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Foxp2+mediates+sex+differences+in+ultrasonic+vocalization+by+rat+pups+and+directs+order+of+maternal+retrieval.">Foxp2 mediates sex differences in ultrasonic vocalization by rat pups and directs order of maternal retrieval.</a> Journal of Neuroscience. 33 (8), 3276-3283 (2013).</li><li>Basken, J. N., Connor, N. P., Ciucci, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+aging+on+ultrasonic+vocalizations+and+laryngeal+sensorimotor+neurons+in+rats.">Effect of aging on ultrasonic vocalizations and laryngeal sensorimotor neurons in rats.</a> Experimental Brain Research. 219 (3), 351-361 (2012).</li><li>Ciucci, M. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduction+of+dopamine+synaptic+activity:+degradation+of+50-kHz+ultrasonic+vocalization+in+rats.">Reduction of dopamine synaptic activity: degradation of 50-kHz ultrasonic vocalization in rats.</a> Behavioral Neuroscience. 123 (2), 328-336 (2009).</li><li>Ciucci, M. R., Vinney, L., Wahoske, E. J., Connor, N. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+translational+approach+to+vocalization+deficits+and+neural+recovery+after+behavioral+treatment+in+Parkinson+disease.">A translational approach to vocalization deficits and neural recovery after behavioral treatment in Parkinson disease.</a> Journal of Communication Disorders. 43 (4), 319-326 (2010).</li><li>Nagai, H., Ota, F., Konopacki, R., Connor, N. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Discoordination+of+laryngeal+and+respiratory+movements+in+aged+rats.">Discoordination of laryngeal and respiratory movements in aged rats.</a> American Journal of Otolaryngology. 26 (6), 377-382 (2005).</li><li>Ma, S. T., Maier, E. Y., Ahrens, A. M., Schallert, T., Duvauchelle, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Repeated+intravenous+cocaine+experience:+development+and+escalation+of+pre-drug+anticipatory+50-kHz+ultrasonic+vocalizations+in+rats.">Repeated intravenous cocaine experience: development and escalation of pre-drug anticipatory 50-kHz ultrasonic vocalizations in rats.</a> Behavioural Brain Research. 212 (1), 109-114 (2010).</li><li>Inagi, K., Schultz, E., Ford, C. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+anatomic+study+of+the+rat+larynx:+establishing+the+rat+model+for+neuromuscular+function.">An anatomic study of the rat larynx: establishing the rat model for neuromuscular function.</a> Otolaryngology and Head and Neck Surgery. 118 (1), 74-81 (1998).</li><li>Lenell, C., Newkirk, B., Johnson, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laryngeal+Neuromuscular+Response+to+Short-+and+Long-Term+Vocalization+Training+in+Young+Male+Rats.">Laryngeal Neuromuscular Response to Short- and Long-Term Vocalization Training in Young Male Rats.</a> Journal of Speech, Language, and Hearing Research. 62 (2), 247-256 (2019).</li><li>Kumar, A., Accorsi, A., Rhee, Y., Girgenrath, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Do's+and+don'ts+in+the+preparation+of+muscle+cryosections+for+histological+analysis.">Do's and don'ts in the preparation of muscle cryosections for histological analysis.</a> Journal of Visualized Experiments. (99), e52793 (2015).</li><li>McMullen, C. A., Andrade, F. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+and+morphological+evidence+of+age-related+denervation+in+rat+laryngeal+muscles.">Functional and morphological evidence of age-related denervation in rat laryngeal muscles.</a> Journals of Gerontology. Series A: Biological Sciences and Medical Sciences. 64 (4), 435-442 (2009).</li><li>McMullen, C. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+stimulation-induced+changes+in+the+rodent+thyroarytenoid+muscle.">Chronic stimulation-induced changes in the rodent thyroarytenoid muscle.</a> Journal of Speech, Language, and Hearing Research. 54 (3), 845-853 (2011).</li><li>Lenell, C., Johnson, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sexual+dimorphism+in+laryngeal+muscle+fibers+and+ultrasonic+vocalizations+in+the+adult+rat.">Sexual dimorphism in laryngeal muscle fibers and ultrasonic vocalizations in the adult rat.</a> Laryngoscope. 127 (8), 270-276 (2017).</li><li>Johnson, A. M., Ciucci, M. R., Connor, N. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vocal+training+mitigates+age-related+changes+within+the+vocal+mechanism+in+old+rats.">Vocal training mitigates age-related changes within the vocal mechanism in old rats.</a> Journals of Gerontology. Series A: Biological Sciences and Medical Sciences. 68 (12), 1458-1468 (2013).</li><li>Feng, X., Zhang, T., Ralston, E., Ludlow, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differences+in+neuromuscular+junctions+of+laryngeal+and+limb+muscles+in+rats.">Differences in neuromuscular junctions of laryngeal and limb muscles in rats.</a> Laryngoscope. 122 (5), 1093-1098 (2012).</li></ol>

Preparing rat vocal folds for neuromuscular analysis can present with various challenges. Not only are laryngeal muscles small and surrounded by cartilage, thereby making it difficult to directly extract target muscle, high variability was also found between animals in the depth of laryngeal anatomical landmarks. For muscle the cross-section plane protocol, complete vocal fold sections appeared between 21&#8722;85 sections (10 &#181;m per section) after the initial appearance of the ventral thyroid cartilage, which is qu...

The rat larynx is a well-established model to investigate structural and functional neuromuscular laryngeal adaptations to development, aging, disease, and pharmacological agents1,2,3,4,5. Consistency of histological methods is critical to this line of work, as there are multiple intricacies involved in muscle preparation and analysis as well as challenges associated with laryngeal size, shape, and topography of the muscles encapsulated within the laryngeal cartilages1,6,7,8,9,10,11. Due to the small size of the rat intrinsic laryngeal muscles, systematic embedding, freezing, and cryosectioning are critical to achieve consistent and accurate results. For example, when sectioning the rat vocal fold in the coronal plane, the neuromuscular junctions (NMJs) of four of the intrinsic laryngeal muscles are located within less than 1.8 mm of tissue depth11. Therefore, precise monitoring of laryngeal muscle anatomy during cryosectioning is imperative to accurately identify the section(s) of interest and prevent oversectioning of tissue. Oversectioning of the target muscle can result in inaccurate identification of number and topography of NMJs11 or can result in overall reductions in sample size if the target muscle is discarded due to landmark orientation confusion12. As novel models for the study of laryngeal muscle and their respective adaptations are developed, standard operating procedures are essential to ensure results are precise, reliable, and reproducible across studies.
The objective of this article is to detail preparation of the rat vocal fold for optimal longitudinal and cross-sectional analysis. Detailed methods used regularly in our laboratory are described to identify target muscle landmarks during cryosectioning. Although similar methods are used in several laboratories, greater detail is provided here than in the literature to ensure reliable and accurate replication when implemented by novice investigators. The goal of this tutorial is to provide a standard methodology for immunohistochemical (IHC) evaluation of the rat vocal fold to improve consistency across laboratories and investigations.

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			<td>CM3050</td>
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			<td>C.L. Sturkey D554X50</td>
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			<td>Paraformaldehyde, 16% w/v aq. soln., methanol free</td>
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			<td>Assi</td>
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			<td colspan="4">NOTE: For all supplies, these are examples of equipment to purchase. The exact model is not necessary to complete our methods.</td>
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</table>

preparation of the rat vocal fold for neuromuscular analyses

The purpose of this tutorial is to describe the preparation of the rat vocal fold for histochemical neuromuscular study. This protocol outlines procedures for rat laryngeal dissection, flash-freezing, and cryosectioning of the vocal folds. This study describes how to cryosection vocal folds in both longitudinal and cross-sectional planes. A novelty of this protocol is the laryngeal tracking during cryosectioning that ensures accurate identification of the intrinsic laryngeal muscles and reduces the chance of tissue loss. Figures demonstrate the progressive cryosectioning in both planes. Twenty-nine rat hemi-larynges were cryosectioned and tracked from the emergence of the thyroid cartilage to the appearance of the first section that included the full vocal fold. The full vocal fold was visualized for all animals in both planes. There was high variability in the distance from the appearance of the thyroid cartilage to the appearance of the full vocal fold in both planes. Weight was not correlated to depth of laryngeal landmarks, suggesting individual variability and other factors related to tissue preparation may be responsible for the high variability in the appearance of landmarks during sectioning. This study details a methodology and presents morphological data for preparing the rat vocal fold for histochemical neuromuscular investigation. Due to high individual variability, laryngeal landmarks should be closely tracked during cryosectioning to prevent oversectioning tissue and tissue loss. The use of a consistent methodology, including adequate tissue preparation and awareness of landmarks within the rat larynx, will assist with consistent results across studies and aid new researchers interested in using the rat vocal fold as a model to investigate laryngeal neuromuscular mechanisms.

The representative results were part of an ongoing investigation of the effects of vocal exercise on the laryngeal neuromuscular system. Twenty-nine male Fischer 344/brown Norway rats (12 9-month-old, 17 24-month-old) were weighed and euthanized with CO2 inhalation followed by a bilateral thoracotomy.
The procedures followed the outlined protocol to label NMJs and fiber size of the lateral and medial TA muscles. The distance between laryngeal landmarks was tracked in both longitudin...

Watch this Scientific Journal Video about Preparation of the Rat Vocal Fold for Neuromuscular Analyses at JoVE.com

Preparation of the Rat Vocal Fold for Neuromuscular Analyses

This protocol describes methods used to prepare rat vocal folds for histochemical neuromuscular study.

The purpose of this tutorial is to describe the preparation of the rat vocal fold for histochemical neuromuscular study. This protocol outlines procedures ...

This protocol facilitates the preparation of the rat and vocal fold for optimal longitudinal and cross-sectional analysis. The protocol utilizes laryngeal tracking during cryosectioning to ensure an accurate identification of the intrinsic laryngeal muscles and to reduce the chance of tissue loss. The rant larynx is a well-established model for investigating structural and functional neuromuscular laryngeal adaptations in response to development, aging, disease, and pharmacological agents.Although this demonstration focuses on the thyroarytenoid muscle of the vocal fold, the methodology is also applicable to other intrinsic laryngeal muscles. For dissection of the rat larynx, shave the ventral neck from the mandible to the manubrium and swab the exposed area with alcohol to prevent fur contamination of the tissue specimens. Place the rat under a dissecting microscope with a 10 times magnification and use a scalpel to make a midline neck incision until the trachea is exposed.Use forceps and a sharp instrument to separate the ventral extrinsic laryngeal muscles at the midline and sever the trachea caudal to the third tracheal ring. To excise the larynx, use dissecting scissors to make an incision caudal to the third tracheal ring and rostral to the hyoid bone. Use tweezers, pins, and microscissors to remove the esophagus, thyroid gland, and extrinsic laryngeal muscles from the larynx.Using the midline between the posterior cricoarytenoid muscles as a landmark, use the microscissors to bisect the larynx dorsally between the arytenoids. Pin the lateral walls of the larynx to expose the vocal folds and use the microscissors to bisect the tissue ventrally through the midline of the thyroid cartilage between the anterior commissure of the vocal folds. Then rinse each hemilarynx in PBS for 10 seconds before delicately drying the tissue with a task wiper to reduce ice crystal formation during freezing.To fix the hemilarynx tissues, place the samples in a centrifuge tube containing 4%formaldehyde and PBS for one hour at room temperature on an orbital shaker at 70 revolutions per minute. At the end of the incubation, transfer the tissues into a new centrifuge tube and rinse the samples three times for 20 minutes in fresh PBS per wash. After the last wash, transfer the tissues into a new centrifuge tube containing a 20%sucrose 5%glycerol solution at four degrees Celsius for up to 18 hours.When the tissue has sunk to the bottom of the tube, place the hemilarynges into a cryomold filled with optimal cutting temperature medium with the medial surface of the vocal fold facing the bottom of the cryomold in the longitudinal aspect of the vocal fold parallel to the lower edge of the cryomold opening. Flash freeze the submerged tissues in isopentane chilled in a steel beaker surrounded by liquid nitrogen and wrap each mold in pre-labeled foil for minus 80 degrees Celsius storage. To acquire cross-sectional plane sections of the frozen hemilarynx tissue samples, set the cryostat chamber to minus 20 degrees Celsius and set the section thickness to 10 microns.Transfer the tissue samples to the cryostat chamber and use additional optimal temperature cutting medium to attach one embedded tissue sample to the cryostat specimen disk with the ventral thyroid cartilage facing the cryostat blade and the arytenoid cartilage facing the specimen disk. To trim the cutting medium from the frozen tissue block, advance the specimen head by 100 microns until the ventral portion of the thyroid cartilage appears. Then trim and track 30 micrometer sections from the onset of the thyroid cartilage until the lamina propria, medial thyroid arytenoid muscles, and lateral thyroarytenoid muscle can be observed by light microscopy.An accurate identification of the transparent tissues during cryosectioning is the most difficult and critical component of this protocol. Once the target muscle has been reached, collect 10 micron sections of the tissue on positively charged slides and store the sections at four degrees Celsius in PBS until they are ready to be stained. To obtain longitudinal vocal fold sections for neuromuscular junction analysis of the thyroarytenoid muscle, affix the specimens to the disks so that the epiglottitis is oriented toward the cryostat blade and the tracheal lumen faces down toward the specimen disk and trim the cutting medium as just demonstrated.Trim and track 30 micrometer sections from the onset of the thyroid until the lamina propria, and medial and lateral divisions of the thyroarytenoid muscle can be observed by light microscopy. Once the target muscle has been reached, collect 30 micrometer sections onto positively charged slides and store the sections at four degrees Celsius in PBS until they are ready to be stained. In this analysis, the distance between laryngeal landmarks was tracked in both longitudinal and cross-sectional planes using laryngeal muscles in the surrounding cartilages to determine their progression during cryosectioning.Here, the appearance of laryngeal landmarks during cross-sectional cryosectioning in temporal order with the thyroid can be observed, appearing prior to the medial thyroarytenoid muscle and the lamina propria. Here, the appearance of laryngeal landmarks during longitudinal cryosectioning in temporal order with the alar muscle appearing prior to the medial thyroarytenoid muscle and the lamina propria. Weight and laryngeal landmark appearances had weak to moderate correlations for young rats and weak correlations for aged rats.The distances among landmarks within each plane were moderately to strongly correlated for both age groups, but weakly correlated between the two dissection planes. The most important thing to remember is that small variations in the tissue embedding and mounting will result in large variations during cryosectioning. These detailed procedures allow reliable neuromuscular histological investigations of the rat vocal fold.

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Neuroscience

Morphometric Analyses of Retinal Sections

Morphometric analyses of retinal sections have been used in examining retinal diseases. For examples, neuronal cells were significantly lost in the retinal ganglion cell layer (RGCL) in rat models with N-methyl-D-aspartate (NMDA)&#x2013;induced excitotoxicity1, retinal ischemia-reperfusion injury2 and glaucoma3. Reduction of INL and inner plexiform layer (IPL) thicknesses were reversed with citicoline treatment in rats' eyes subjected to kainic acid-mediated glutamate excitotoxicity4. Alteration of RGC density and soma sizes were observed with different drug treatments in eyes with elevated intraocular pressure3,5,6. Therefore, having objective methods of analyzing the retinal morphometries may be of great significance in evaluating retinal pathologies and the effectiveness of therapeutic strategies.
The retinal structure is multi-layers and several different kinds of neurons exist in the retina. The morphometric parameters of retina such as cell number, cell size and thickness of different layers are more complex than the cell culture system. Early on, these parameters can be detected using other commercial imaging software. The values are normally of relative value, and changing to the precise value may need further accurate calculation. Also, the tracing of the cell size and morphology may not be accurate and sensitive enough for statistic analysis, especially in the chronic glaucoma model. The measurements used in this protocol provided a more precise and easy way. And the absolute length of the line and size of the cell can be reported directly and easy to be copied to other files. For example, we traced the margin of the inner and outer most nuclei in the INL and formed a line then using the software to draw a 90 degree angle to measure the thickness. While without the help of the software, the line maybe oblique and the changing of retinal thickness may not be repeatable among individual observers. In addition, the number and density of RGCs can also be quantified. This protocol successfully decreases the variability in quantitating features of the retina, increases the sensitivity in detecting minimal changes.
 	This video will demonstrate three types of morphometric analyses of the retinal sections. They include measuring the INL thickness, quantifying the number of RGCs and measuring the sizes of RGCs in absolute value. These three analyses are carried out with Stereo Investigator (MBF Bioscience &mdash; MicroBrightField, Inc.). The technique can offer a simple but scientific platform for morphometric analyses.

This video demonstrates three types of morphometric analyses of the retina, which include measuring the inner nuclear layer thickness, quantifying the number of retinal ganglion cells (RGCs) and measuring the sizes of RGCs. The technique can offer a simple but scientific platform for morphometric analyses.

Morphometric analyses of retinal sections have been used in examining retinal diseases. For examples, neuronal cells were significantly lost in the ...

Sequential Photo-bleaching to Delineate Single Schwann Cells at the Neuromuscular Junction

Sequential photo-bleaching provides a non-invasive way to label individual SCs at the NMJ. The NMJ is the largest synapse of the mammalian nervous system and has served as guiding model to study synaptic structure and function. In mouse NMJs motor axon terminals form pretzel-like contact sites with muscle fibers. The motor axon and its terminal are sheathed by SCs. Over the past decades, several transgenic mice have been generated to visualize motor neurons and SCs, for example Thy1-XFP1 and Plp-GFP mice2, respectively.
Along motor axons, myelinating axonal SCs are arranged in non-overlapping internodes, separated by nodes of Ranvier, to enable saltatory action potential propagation. In contrast, terminal SCs at the synapse are specialized glial cells, which monitor and promote neurotransmission, digest debris and guide regenerating axons. NMJs are tightly covered by up to half a dozen non-myelinating terminal SCs - these, however, cannot be individually resolved by light microscopy, as they are in direct membrane contact3.
Several approaches exist to individually visualize terminal SCs. None of these are flawless, though. For instance, dye filling, where single cells are impaled with a dye-filled microelectrode, requires destroying a labelled cell before filling a second one. This is not compatible with subsequent time-lapse recordings3. Multi-spectral "Brainbow" labeling of SCs has been achieved by using combinatorial expression of fluorescent proteins4. However, this technique requires combining several transgenes and is limited by the expression pattern of the promoters used. In the future, expression of "photo-switchable" proteins in SCs might be yet another alternative5. Here we present sequential photo-bleaching, where single cells are bleached, and their image obtained by subtraction. We believe that this approach - due to its ease and versatility - represents a lasting addition to the neuroscientist's technology palette, especially as it can be used in vivo and transferred to others cell types, anatomical sites or species6.
In the following protocol, we detail the application of sequential bleaching and subsequent confocal time-lapse microscopy to terminal SCs in triangularis sterni muscle explants. This thin, superficial and easily dissected nerve-muscle preparation7,8 has proven useful for studies of NMJ development, physiology and pathology9. Finally, we explain how the triangularis sterni muscle is prepared after fixation to perform correlated high-resolution confocal imaging, immunohistochemistry or ultrastructural examinations.

Visualizing individual cells in densely packed tissues, such as terminal Schwann cells (SCs) at neuromuscular junctions (NMJs), is challenging. "Sequential photo-bleaching" allows delineating single terminal SCs, for instance in the triangularis sterni muscle explant, a convenient nerve-muscle preparation, where sequential bleaching can be combined with time-lapse imaging and post-hoc immunostainings.

Sequential photo-bleaching provides a non-invasive way to label individual SCs at the NMJ. The NMJ is the largest synapse of the mammalian nervous system ...

Dissection of the Transversus Abdominis Muscle for Whole-mount Neuromuscular Junction Analysis

Analysis of neuromuscular junction morphology can give important insight into the physiological status of a given motor neuron. Analysis of thin flat muscles can offer significant advantage over traditionally used thicker muscles, such as those from the hind limb (e.g. gastrocnemius). Thin muscles allow for comprehensive overview of the entire innervation pattern for a given muscle, which in turn permits identification of selectively vulnerable pools of motor neurons. These muscles also allow analysis of parameters such as motor unit size, axonal branching, and terminal/nodal sprouting. A common obstacle in using such muscles is gaining the technical expertise to dissect them. In this video, we detail the protocol for dissecting the transversus abdominis (TVA) muscle from young mice and performing immunofluorescence to visualize axons and neuromuscular junctions (NMJs). We demonstrate that this technique gives a complete overview of the innervation pattern of the TVA muscle&#160;and can be used to investigate NMJ pathology in a mouse model of the childhood motor neuron disease, spinal muscular atrophy.

Dissection of the Transversus Abdominis Muscle for Whole-mount Neuromuscular Junction Analysis

In this video we demonstrate a protocol for dissection of the transversus abdominis muscle of the mouse and use immunofluorescence and microscopy to visualize neuromuscular junctions.

Analysis of neuromuscular junction morphology can give important insight into the physiological status of a given motor neuron. Analysis of thin flat ...

Why Quantification Matters: Characterization of Phenotypes at the Drosophila Larval Neuromuscular Junction

Most studies on morphogenesis rely on qualitative descriptions of how anatomical traits are affected by the disruption of specific genes and genetic pathways. Quantitative descriptions are rarely performed, although genetic manipulations produce a range of phenotypic effects and variations are observed even among individuals within control groups.&#160;Emerging evidence shows that morphology, size and location of organelles play a previously underappreciated, yet fundamental role in cell function and survival. Here we provide step-by-step instructions for performing quantitative analyses of phenotypes at the Drosophila larval neuromuscular junction (NMJ). We use several reliable immuno-histochemical markers combined with bio-imaging techniques and morphometric analyses to examine the effects of genetic mutations on specific cellular processes. In particular, we focus on the quantitative analysis of phenotypes affecting morphology, size and position of nuclei within the striated muscles of Drosophila larvae. The Drosophila larval NMJ is a valuable experimental model to investigate the molecular mechanisms underlying the structure and the function of the neuromuscular system, both in health and disease. However, the methodologies we describe here can be extended to other systems as well.

Why Quantification Matters: Characterization of Phenotypes at the Drosophila Larval Neuromuscular Junction

Morphology, size and location of intracellular organelles are evolutionarily conserved and appear to directly affect their function. Understanding the molecular mechanisms underlying these processes has become an important goal of modern biology. Here we show how these studies can be facilitated by the application of quantitative techniques.

Most studies on morphogenesis rely on qualitative descriptions of how anatomical traits are affected by the disruption of specific genes and genetic ...

Measuring Neuromuscular Junction Functionality

Neuromuscular junction (NMJ) functionality plays a pivotal role when studying diseases in which the communication between motor neuron and muscle is impaired, such as aging and amyotrophic lateral sclerosis (ALS). Here we describe an experimental protocol that can be used to measure NMJ functionality by combining two types of electrical stimulation: direct muscle membrane stimulation and the stimulation through the nerve. The comparison of the muscle response to these two different stimulations can help to define, at the functional level, potential alterations in the NMJ that lead to functional decline in muscle.
Ex vivo preparations are suited to well-controlled studies. Here we describe an intensive protocol to measure several parameters of muscle and NMJ functionality for the soleus-sciatic nerve preparation and for the diaphragm-phrenic nerve preparation. The protocol lasts approximately 60 min and is conducted uninterruptedly by means of a custom-made software that measures the twitch kinetics properties, the force-frequency relationship for both muscle and nerve stimulations, and two parameters specific to NMJ functionality, i.e. neurotransmission failure and intratetanic fatigue. This methodology was used to detect damages in soleus and diaphragm muscle-nerve preparations by using SOD1G93A transgenic mouse, an experimental model of ALS that ubiquitously overexpresses the mutant antioxidant enzyme superoxide dismutase 1 (SOD1).

A functional assessment of the neuromuscular junction (NMJ) can provide essential information on the communication between muscle and nerve. Here we describe a protocol to comprehensively evaluate both the NMJ and muscle functionality using two different muscle-nerve preparations, i.e. soleus-sciatic and diaphragm-phrenic.

Neuromuscular junction (NMJ) functionality plays a pivotal role when studying diseases in which the communication between motor neuron and muscle is ...

Microstate and Omega Complexity Analyses of the Resting-state Electroencephalography

Microstate and omega complexity are two reference-free electroencephalography (EEG) measures that can represent the temporal and spatial complexities of EEG data and have been widely used to investigate the neural mechanisms in some brain disorders. The goal of this article is to describe the protocol underlying EEG microstate and omega complexity analyses step by step. The main advantage of these two measures is that they could eliminate the reference-dependent problem inherent to traditional spectrum analysis. In addition, microstate analysis makes good use of high time resolution of resting-state EEG, and the four obtained microstate classes could match the corresponding resting-state networks respectively. The omega complexity characterizes the spatial complexity of the whole brain or specific brain regions, which has obvious advantage compared with traditional complexity measures focusing on the signal complexity in a single channel. These two EEG measures could complement each other to investigate the brain complexity from the temporal and spatial domain respectively.

This article describes the protocol underlying electroencephalography (EEG) microstate analysis and omega complexity analysis, which are two reference-free EEG measures and highly valuable to explore the neural mechanisms of brain disorders.

Microstate and omega complexity are two reference-free electroencephalography (EEG) measures that can represent the temporal and spatial complexities of ...

Levator Auris Longus Preparation for Examination of Mammalian Neuromuscular Transmission Under Voltage Clamp Conditions

This protocol describes a technique to record synaptic transmission from the neuromuscular junction under current-clamp and voltage-clamp conditions. An ex vivo preparation of the levator auris longus (LAL) is used because it is a thin muscle that provides easy visualization of the neuromuscular junction for microelectrode impalement at the motor endplate. This method allows for the recording of spontaneous miniature endplate potentials and currents (mEPPs and mEPCs), nerve-evoked endplate potentials and currents (EPPs and EPCs), as well as the membrane properties of the motor endplate. Results obtained from this method include the quantal content (QC), number of vesicle release sites (n), probability of vesicle release (prel), synaptic facilitation and depression, as well as the muscle membrane time constant (&#964;m) and input resistance. Application of this technique to mouse models of human disease can highlight key pathologies in disease states and help identify novel treatment strategies. By fully voltage-clamping a single synapse, this method provides one of the most detailed analyses of synaptic transmission currently available.

Levator Auris Longus Preparation for Examination of Mammalian Neuromuscular Transmission Under Voltage Clamp Conditions

The protocol described in this paper uses the mouse levator auris longus (LAL) muscle to record spontaneous and nerve-evoked postsynaptic potentials (current-clamp) and currents (voltage-clamp) at the neuromuscular junction. Use of this technique can provide key insights into mechanisms of synaptic transmission under normal and disease conditions.

This protocol describes a technique to record synaptic transmission from the neuromuscular junction under current-clamp and voltage-clamp conditions. An ...

Collection of Frozen Rodent Brain Regions for Downstream Analyses

As our understanding of neurobiology has progressed, molecular analyses are often performed on small brain areas such as the medial prefrontal cortex (mPFC) or nucleus accumbens. The challenge in this work is to dissect the correct area while preserving the microenvironment to be examined. In this paper, we describe a simple, low-cost method using resources readily available in most labs. This method preserves nucleic acid and proteins by keeping the tissue frozen throughout the process. Brains are cut into 0.5&#8211;1.0 mm sections using a brain matrix and arranged on a frozen glass plate. Landmarks within each section are compared to a reference, such as the Allen Mouse Brain Atlas, and regions are dissected using a cold scalpel or biopsy punch. Tissue is then stored at -80 &#176;C until use. Through this process rat and mouse mPFC, nucleus accumbens, dorsal and ventral hippocampus and other regions have been successfully analyzed using qRT-PCR and Western assays. This method is limited to brain regions that can be identified by clear landmarks.

This procedure describes the collection of discrete frozen brain regions to obtain high-quality protein and RNA using inexpensive and commonly available tools.

As our understanding of neurobiology has progressed, molecular analyses are often performed on small brain areas such as the medial prefrontal cortex ...

Dissection of Single Skeletal Muscle Fibers for Immunofluorescent and Morphometric Analyses of Whole-Mount Neuromuscular Junctions

The neuromuscular junction (NMJ) is a specialized point of contact between the motor nerve and the skeletal muscle. This peripheral synapse exhibits high morphological and functional plasticity. In numerous nervous system disorders, NMJ is an early pathological target resulting in neurotransmission failure, weakness, atrophy, and even in muscle fiber death. Due to its relevance, the possibility to quantitatively assess certain aspects of the relationship between NMJ components can help to understand the processes associated with its assembly/disassembly. The first obstacle when working with muscles is to gain the technical expertise to quickly identify and dissect without damaging their fibers. The second challenge is to utilize high-quality detection methods to obtain NMJ images that can be used to perform quantitative analysis. This article presents a step-by-step protocol for dissecting extensor digitorum longus and soleus muscles from rats. It also explains the use of immunofluorescence to visualize pre and postsynaptic elements of whole-mount NMJs. Results obtained demonstrate that this technique can be used to establish the microscopic anatomy of the synapsis and identify subtle changes in the status of some of its components under physiological or pathological conditions.

The ability to accurately detect neuromuscular junction components is crucial in evaluating modifications in its architecture because of pathological or developmental processes. Here we present a complete description of a straightforward method to obtain high-quality images of whole-mount neuromuscular junctions that can be used to perform quantitative measurements.

The neuromuscular junction (NMJ) is a specialized point of contact between the motor nerve and the skeletal muscle. This peripheral synapse exhibits high ...

Expanding the Toolkit for In Vivo Imaging of Axonal Transport

Axonal transport maintains neuronal homeostasis by enabling the bidirectional trafficking of diverse organelles and cargoes. Disruptions in axonal transport have devastating consequences for individual neurons and their networks, and contribute to a plethora of neurological disorders. As many of these conditions involve both cell autonomous and non-autonomous mechanisms, and often display a spectrum of pathology across neuronal subtypes, methods to accurately identify and analyze neuronal subsets are imperative.
This paper details protocols to assess in vivo axonal transport of signaling endosomes and mitochondria in sciatic nerves of anesthetized mice. Stepwise instructions are provided to 1) distinguish motor from sensory neurons in vivo, in situ, and ex vivo by using mice that selectively express fluorescent proteins within cholinergic motor neurons; and 2) separately or concurrently assess in vivo axonal transport of signaling endosomes and mitochondria. These complementary intravital approaches facilitate the simultaneous imaging of different cargoes in distinct peripheral nerve axons to quantitatively monitor axonal transport in health and disease.

Expanding the Toolkit for In Vivo Imaging of Axonal Transport

Using transgenic fluorescent mice, detailed protocols are described to assess in vivo axonal transport of signaling endosomes and mitochondria within motor and sensory axons of the intact sciatic nerve in live animals.