Name: measuring neuromuscular junction functionality
Uploaded: 2017-08-06T13:00:00
Description: Watch this Scientific Journal Video about Measuring Neuromuscular Junction Functionality at JoVE.com

Work in the authors' laboratory was supported by Fondazione Roma and Telethon (grant no. GGP14066).

All the animal experiments were approved by the ethics committee of Sapienza University of Rome-Unit of Histology and Medical Embryology and were performed in accordance with the current version of the Italian Law on the Protection of Animals.
1. Experimental set-up
<ol>
	<li>Set-up the experimental system composed of 1 actuator/transducer, 2 stimulators, 1 in-vitro muscle apparatus, 1 preparatory tissue bath, 1 suction electrode, 1 digital oscilloscope, 1 stereomicroscope, 1 cold l...

<ol>
	<li>Dadon-Nachum, M., Melamed, E., Offen, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+&amp;#34;dying-back&amp;#34;+phenomenon+of+motor+neurons+in+ALS.">The &amp;#34;dying-back&amp;#34; phenomenon of motor neurons in ALS.</a> J Mol Neurosci. 43 (3), 470-477 (2011).</li><li>Dobrowolny, G., 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=Skeletal+Muscle+Is+a+Primary+Target+of+SOD1G93A-Mediated+Toxicity.">Skeletal Muscle Is a Primary Target of SOD1G93A-Mediated Toxicity.</a> Cell Metab. 8 (5), 425-436 (2008).</li><li>Mantilla, C. B., Zhan, W. Z., Sieck, G. 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E., Sawyer, R. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Variability+and+failure+of+neurotransmission+in+the+diaphragm+of+mdx+mice.">Variability and failure of neurotransmission in the diaphragm of mdx mice.</a> Neuromuscular Disord. 16 (3), 168-177 (2006).</li><li>R&#246;der, I. V., Petersen, Y., Choi, K. R., Witzemann, V., Hammer, J. 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H., Shadmehr, R., Sieck, G. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relative+contribution+of+neurotransmission+failure+to+diaphragm+fatigue.">Relative contribution of neurotransmission failure to diaphragm fatigue.</a> J Appl Physiol (Bethesda, Md: 1985). 68 (1), 174-180 (1990).</li><li>Del Prete, Z., Musar&#242;, A., Rizzuto, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+mechanical+properties,+including+isotonic+fatigue,+of+fast+and+slow+MLC/mIgf-1+transgenic+skeletal+muscle.">Measuring mechanical properties, including isotonic fatigue, of fast and slow MLC/mIgf-1 transgenic skeletal muscle.</a> Ann Biomed Eng. 36 (7), 1281-1290 (2008).</li><li>Lynch, G. S., Hinkle, R. T., Chamberlain, J. S., Brooks, S. V., Faulkner, J. 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The experimental protocol described above provides an ideal way of measuring and discriminating any functional alterations that have occurred directly in the muscle or indirectly at the neuromuscular junction level. Since this technique is based on an indirect measurement of NMJ functionality, it cannot be used to establish if any defect is related to morphological changes or to biochemical changes. By contrast, it does provide an effective way of determining whether any morphological or biochemical alterations have redu...

The neuromuscular junction (NMJ) is a chemical synapse formed by the connection between the motor endplate of the muscle fiber and the motor neuron axon terminal. The NMJ has been shown to play a crucial role when communication between muscle and nerve is impaired, as occurs in aging or amyotrophic lateral sclerosis (ALS). As muscle and nerve communicate in a bidirectional way1,2, being able to measure NMJ defects separately from muscle defects may provide new insights into their physiopathological interplay. Indeed, this functional evaluation may help to assess whether morphological or biochemical alterations reduce neurotransmission signaling functionality.
The comparison of muscle contractile response elicited by nerve stimulation and the response of the same muscle evoked by direct stimulation of its membrane has been proposed as an indirect measurement of NMJ functionality. Indeed, since membrane stimulation by-passes neurotransmission signaling, any differences in the two contractile responses may be ascribed to changes in the NMJ. This approach has been extensively proposed for rats3,4,5,6,7, and also used to gather information on mouse models8,9,10,11,12.
Here, we describe in detail a procedure to excise and test two muscle-nerve preparations, i. e. the soleus-sciatic and diaphragm-phrenic preparations. Using a custom-made software, we designed a continuous testing protocol that combines the measurement of several parameters that characterize both NMJ and muscle functionality, thereby yielding a comprehensive evaluation of NMJ damage separately from that of muscle. In particular, the protocol measures the twitch force, the muscle kinetics, the force-frequency curve for direct and nerve stimulations, the neurotransmission failure13 for both a firing and the tetanic frequencies, and the intratetanic fatigue7.

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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).

The protocol we described provides information on functional denervation in several neuromuscular diseases or aging-sarcopenia. This protocol can be used to determine whether (and, if so, at which level) muscle alterations are due to selective changes that occur in the muscle itself or in neuromuscular transmission. The data shown below are the results of a previous work by our group18, conducted on the SOD1G93A transgenic mouse model of amyotrophic late...

Watch this Scientific Journal Video about Measuring Neuromuscular Junction Functionality at JoVE.com

Measuring Neuromuscular Junction Functionality

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 ...

The overall goal of this procedure is to study neuromuscular junction functionality by means of an ex vivo experimental approach. This is accomplished by stimulating the muscle nerve preparation in two ways, directly on the muscle membrane and through the nerve. Since membrane stimulation bypasses neuro transmission signaling, any differences between the two contractile responses can be considered as an indirect measurement of neuromuscular junction functionality.Here we present this procedure in soleus sciatic nerve preparation. The muscle is dissected together with its nerve and placed into a perfused tissue bath. It is fixed to a force and length controller and a platinum pair of electrodes are placed parallel to the muscle.A glass suction electrode is then moved close to the cut end of the nerve. A comprehensive testing protocol is then applied to thoroughly evaluate both neuromuscular junction and muscle functionality. The functional connection between muscle and nerve is conclusion for both part and two surviving faction.In the first region of the level of each of the two tissue communicate that these neuromuscular junction, which normally displays a pressure like morphology. Nevertheless in several pathological conditions the functionality interplayed between muscle and nerve is severely compromised and neuromuscular junction lose the complex morphologic organization. The overall goal of our procedure is to study neuromuscular junction functionality by using and ex vivo experimental approach.This is accomplished by stimulating the muscle nerve preparation in two ways. One by directly stimulating the muscle membrane and the other by stimulating the nerve and analyze the muscle properties. Turn on the circulation water bath and adjust the temperature to 30 degrees celsius.Fill the bath with the Krebs-Ringer solution. Allow O point four bar of gas mixture to flow through the oxitube and into the bath. Turn on the actuator transducer and the two pulse stimulators.Set the current values to 300 million pair for the membrane stimulation and to five million pair for the nerve stimulation. After sacrificing the mouse by cervical dislocation, remove the skin from the legs. Now cut the achilles tendon and while tightly clamping the tendon, pull the gastrocnemius muscle and the soleus together upwards.Once the proximal tendon of the soleus is exposed cut the entire calf above it and quickly place the sample in the preparatory tissue bath located under the stereo microscope. Using a pair of forceps, tightly clamp the proximal tendon of the soleus and gently pull it to expose the sciatic innervation. Once the innervation is exposed remove the surrounding tissues to reveal about five millimeters of the nerve.Then use a fine pair of scissors to carefully cut the nerve. Complete the muscle, nerve excision by cutting the achilles tendon to separate the soleus from the gastrocnemius. Now the muscle, nerve preparation is ready to be mounted onto the testing apparatus.Create a slip knot at the end of the nylon thread and tighten it around the achilles tendon. Clamp the proximal tendon within the fixed clamp and tie the nylon wire around the lever arm of the force transducer. Allow the muscle to equilibrate in the solution.To determine the initial optimal length, stimulate the muscle with a series of single pulses while gently changing the creep load value. The optimal length is obtained when the twitch force is maximum. Place the suction electrodes near the muscle and pull the nerve in.Then, while gently altering the pulse current value, stimulate the muscle with a series of single pulses. The twitch force generated by the muscle when stimulated through the nerve should be equal to the values measured when stimulating it on the membrane. Once the optimal current value is determined, push the nerve out of the electrode and deliver a few current pulses.If the amount of previously selected current is excessive, the current pulses delivered through the suction electrode elicit the muscle contraction by conducting current through the bath. Using a home-made software we devised an automated testing protocol for the study of soleus neuromuscular junction functionality. The protocol lasts about 65 minutes and is made up of four different parts.In the first part, the muscle is stimulated with four single pulses. Two delivered directly and two through the nerve. Time to peak, half relaxation time, maximum value of force derivative and twitch force are then measured from the twitch responses.In the second part, the muscle is stimulated with a series of pulse trains ranging from 20 hertz to 80 hertz, which is the tetanic frequency. To compute the force, frequency curves for both nerve and direct stimulations. In the third and fourth parts of the protocol the muscle is subjected to two fatigue paradigms to measure neuro transmission failure and intra tetanic fatigue.During these fatigue paradigms, the muscle is continuously stimulated with one pulse train delivered on the membrane followed by 14 pulse trains delivered through the nerve. The entire sequence is repeated 20 times. The first paradigm is delivered at a firing frequency of 35 hertz.The second at the tetanic frequency of 80 hertz. Neuro transmission failure is believed to play an important role in the development of fatigue as it is related to the external block of action potential propagation, decreased transmitter release and decreased and plate excitability of junction fatigue ability. Another aspect of neuromuscular junction fatigue ability is clearly expressed by intratetanic fatigue which is an estimate of the muscle's ability to maintain force during a single tetanic contraction and reflects high frequency fatigue.At the end of the protocol, net muscle length and weight are measured using an analog caliper and a precision scale to compute the muscle cross sectional area. Studies on the SOD1 transgenic mouse model of amyotrophic lateral sclerosis have highlighted the potential of this methodology. In fact, the transgenic soleus muscles yield a reduced contractile response for both the force derivative and tetanic force when directly stimulated and an even greater reduction when stimulated through the nerve.As regards to tetanic force for example, these experiments have shown that muscle contractility accounts for 25%of the damage while a further 45%is related to defects in neuro transmission. Another interesting point is the absence of any difference in control muscles when stimulated directly or indirectly. This finding proves that the methodology does not induce any technical artifacts since the neuromuscular junction is expected to be fully functional in control animals.As regards intratetanic fatigue, the results have shown significantly lower values in transgenic soleus muscles than in their control counterparts. Interestingly, transgenic soleus muscle is significantly damaged by repetitive stimulation, which means that neuromuscular junction functionality can be evaluated for a maximum stimulation time of eight minutes. After eight minutes, the transgenic muscle returns to an almost null value of force when stimulated.After watching the video you should have got understanding how to measure neuromuscular junction functionality and soleus muscle of mouse. Given that this technique based on indirect measurement of neuromuscular junction functionality, it does not allow to be made where reported defects are related to morphologic or biochemical changes. On the other hand, this approach represents an essential way to assess whether these aggressions affect at user functionality of the neuro transmission signal.Finally, the protocol proposal can be easily adopted to measure neuromuscular junction functionality of the diaphragm, another muscle often involved in pathological diseases.

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Dissection and Imaging of Active Zones in the Drosophila Neuromuscular Junction

The Drosophila larvae neuromuscular junction (NMJ) is an excellent model for the study of synaptic structure and function. Drosophila is well known for the ease of powerful genetic manipulations and the larval nervous system has proven particularly useful in studying not only normal function but also perturbations that accompany some neurological disease (Lloyd and Taylor, 2010). Many key synaptic molecules found in Drosophila are also found in mammals and like most CNS excitatory synapses in mammals, the Drosophila NMJ is glutamatergic and demonstrates activity-dependent remodeling (Kohet al. , 2000). Additionally, Drosophila neurons can be individually identified because their innervation patterns are stereotyped and repetitive making it possible to study identified synaptic terminals, such as those between motor neurons and the body-wall muscle fibers that they innervate (Keshishian and Kim, 2004). The existence of evolutionarily conserved synapse components along with the ease of genetic and physical manipulation make the Drosophila model ideal for investigating the mechanisms underlying synaptic function (Budnik, 1996).
The active zones at synaptic terminals are of particular interest because these are the sites of neurotransmitter release. NC82 is a monoclonal antibody that recognizes the Drosophila protein Bruchpilot (Brp), a CAST1/ERC family member that is an important component of the active zone (Waghet al. , 2006). Brp was shown to directly shape the active zone T-bar and is responsible for effectively clustering Ca2+ channels beneath the T-bar density (Fouquetet al. , 2009). Mutants of Brp have reduced Ca2+ channel density, depressed evoked vesicle release, and altered short-term plasticity (Kittelet al. , 2006). Alterations to active zones have been observed in Drosophila disease models. For example, immunofluorescence using the NC82 antibody showed that the active zone density was decreased in models of amyotrophic lateral sclerosis and Pitt-Hopkins syndrome (Ratnaparkhiet al. , 2008; Zweieret al. , 2009). Thus, evaluation of active zones, or other synaptic proteins, in Drosophila larvae models of disease may provide a valuable initial clue to the presence of a synaptic defect.
Preparing whole-mount dissected Drosophila larvae for immunofluorescence analysis of the NMJ requires some skill, but can be accomplished by most scientists with a little practice. Presented is a method that provides for multiple larvae to be dissected and immunostained in the same dissection dish, limiting environmental differences between each genotype and providing sufficient animals for confidence in reproducibility and statistical analysis.

Dissection and Imaging of Active Zones in the Drosophila Neuromuscular Junction

The neuromuscular junction (NMJ) of Drosophila melanogaster is an important model system for studying normal synaptic function as well as perturbations to synaptic function found in certain neurological diseases. We present a protocol for dissection of the Drosophila larval motor system and immunostaining for active zone proteins within the NMJ.

The Drosophila  larvae neuromuscular junction (NMJ) is an excellent model for the study of synaptic structure and function. Drosophila  is well known for ...

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 ...

Detection of In Situ Protein-protein Complexes at the Drosophila Larval Neuromuscular Junction Using Proximity Ligation Assay

Discs large (Dlg) is a conserved member of the membrane-associated guanylate kinase family, and serves as a major scaffolding protein at the larval neuromuscular junction (NMJ) in Drosophila. Previous studies have shown that the postsynaptic distribution of Dlg at the larval NMJ overlaps with that of Hu-li tai shao (Hts), a homologue to the mammalian adducins. In addition, Dlg and Hts are observed to form a complex with each other based on co-immunoprecipitation experiments involving whole adult fly lysates. Due to the nature of these experiments, however, it was unknown whether this complex exists specifically at the NMJ during larval development.
Proximity Ligation Assay (PLA) is a recently developed technique used mostly in cell and tissue culture that can detect protein-protein interactions in situ. In this assay, samples are incubated with primary antibodies against the two proteins of interest using standard immunohistochemical procedures. The primary antibodies are then detected with a specially designed pair of oligonucleotide-conjugated secondary antibodies, termed PLA probes, which can be used to generate a signal only when the two probes have bound in close proximity to each other. Thus, proteins that are in a complex can be visualized. Here, it is demonstrated how PLA can be used to detect in situ protein-protein interactions at the Drosophila larval NMJ. The technique is performed on larval body wall muscle preparations to show that a complex between Dlg and Hts does indeed exist at the postsynaptic region of NMJs.

Detection of In Situ Protein-protein Complexes at the Drosophila Larval Neuromuscular Junction Using Proximity Ligation Assay

This protocol demonstrates how Proximity Ligation Assay can be used to detect in situ protein-protein interactions at the Drosophila larval neuromuscular junction. With this technique, Discs large and Hu-li tai shao are shown to form a complex at the postsynaptic region, an association previously identified through co-immunoprecipitation.

Discs large (Dlg) is a conserved member of the membrane-associated guanylate kinase family, and serves as a major scaffolding protein at the larval ...

The Neuromuscular Junction: Measuring Synapse Size, Fragmentation and Changes in Synaptic Protein Density Using Confocal Fluorescence Microscopy

The neuromuscular junction (NMJ) is the large, cholinergic relay synapse through which mammalian motor neurons control voluntary muscle contraction. Structural changes at the NMJ can result in neurotransmission failure, resulting in weakness, atrophy and even death of the muscle fiber. Many studies have investigated how genetic modifications or disease can alter the structure of the mouse NMJ. Unfortunately, it can be difficult to directly compare findings from these studies because they often employed different parameters and analytical methods. Three protocols are described here. The first uses maximum intensity projection confocal images to measure the area of acetylcholine receptor (AChR)-rich postsynaptic membrane domains at the endplate and the area of synaptic vesicle staining in the overlying presynaptic nerve terminal. The second protocol compares the relative intensities of immunostaining for synaptic proteins in the postsynaptic membrane. The third protocol uses Fluorescence Resonance Energy Transfer (FRET) to detect changes in the packing of postsynaptic AChRs at the endplate. The protocols have been developed and refined over a series of studies. Factors that influence the quality and consistency of results are discussed and normative data are provided for NMJs in healthy young adult mice.

The neuromuscular junction (NMJ) is altered in a variety of conditions that can sometimes culminate in synaptic failure. This report describes fluorescence microscope-based methods to quantify such structural changes.

The neuromuscular junction (NMJ) is the large, cholinergic relay synapse through which mammalian motor neurons control voluntary muscle contraction. ...

Assessment of Neuromuscular Function Using Percutaneous Electrical Nerve Stimulation

Percutaneous electrical nerve stimulation is a non-invasive method commonly used to evaluate neuromuscular function from brain to muscle (supra-spinal, spinal and peripheral levels). The present protocol describes how this method can be used to stimulate the posterior tibial nerve that activates plantar flexor muscles. Percutaneous electrical nerve stimulation consists of inducing an electrical stimulus to a motor nerve to evoke a muscular response. Direct (M-wave) and/or indirect (H-reflex) electrophysiological responses can be recorded at rest using surface electromyography. Mechanical (twitch torque) responses can be quantified with a force/torque ergometer. M-wave and twitch torque reflect neuromuscular transmission and excitation-contraction coupling, whereas H-reflex provides an index of spinal excitability. EMG activity and mechanical (superimposed twitch) responses can also be recorded during maximal voluntary contractions to evaluate voluntary activation level. Percutaneous nerve stimulation provides an assessment of neuromuscular function in humans, and is highly beneficial especially for studies evaluating neuromuscular plasticity following acute (fatigue) or chronic (training/detraining) exercise.

We present a protocol to assess changes in neuromuscular function. Percutaneous electrical nerve stimulation is a non-invasive method that evokes muscular responses. Electrophysiological and mechanical properties of these responses permit the evaluation of neuromuscular function from brain to muscle (supra-spinal, spinal and peripheral levels).

Percutaneous electrical nerve stimulation is a non-invasive method commonly used to evaluate neuromuscular function from brain to muscle (supra-spinal, ...

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 ...

Loading a Calcium Dye into Frog Nerve Endings Through the Nerve Stump: Calcium Transient Registration in the Frog Neuromuscular Junction

One of the most feasible methods of measuring presynaptic calcium levels in presynaptic nerve terminals is optical recording. It is based on using calcium-sensitive fluorescent dyes that change their emission intensity or wavelength depending on the concentration of free calcium in the cell. There are several methods used to stain cells with calcium dyes. Most common are the processes of loading the dyes through a micropipette or pre-incubating with the acetoxymethyl ester forms of the dyes. However, these methods are not quite applicable to neuromuscular junctions (NMJs) due to methodological issues that arise. In this article, we present a method for loading a calcium-sensitive dye through the frog nerve stump of the frog nerve into the nerve endings. Since entry of external calcium into nerve terminals and the subsequent binding to the calcium dye occur within the millisecond time-scale, it is necessary to use a fast imaging system to record these interactions. Here, we describe a protocol for recording the calcium transient with a fast CCD camera.

Here, we describe a method for loading a calcium-sensitive dye through the frog nerve stump into the nerve endings. We also present a protocol for the recording and analysis of fast calcium transients in the peripheral nerve endings.

One of the most feasible methods of measuring presynaptic calcium levels in presynaptic nerve terminals is optical recording. It is based on using ...

Two Algorithms for High-throughput and Multi-parametric Quantification of Drosophila Neuromuscular Junction Morphology

Synaptic morphology is tightly related to synaptic efficacy, and in many cases morphological synapse defects ultimately lead to synaptic malfunction. The Drosophila larval neuromuscular junction (NMJ), a well-established model for glutamatergic synapses, has been extensively studied for decades. Identification of mutations causing NMJ morphological defects revealed a repertoire of genes that regulate synapse development and function. Many of these were identified in large-scale studies that focused on qualitative approaches to detect morphological abnormalities of the Drosophila NMJ. A drawback of qualitative analyses is that many subtle players contributing to NMJ morphology likely remain unnoticed. Whereas quantitative analyses are required to detect the subtler morphological differences, such analyses are not yet commonly performed because they are laborious. This protocol describes in detail two image analysis algorithms "Drosophila NMJ Morphometrics" and "Drosophila NMJ Bouton Morphometrics", available as Fiji-compatible macros, for quantitative, accurate and objective morphometric analysis of the Drosophila NMJ. This methodology is developed to analyze NMJ terminals immunolabeled with the commonly used markers Dlg-1 and Brp. Additionally, its wider application to other markers such as Hrp, Csp and Syt is presented in this protocol. The macros are able to assess nine morphological NMJ features: NMJ area, NMJ perimeter, number of boutons, NMJ length, NMJ longest branch length, number of islands, number of branches, number of branching points and number of active zones in the NMJ terminal.

Two Algorithms for High-throughput and Multi-parametric Quantification of Drosophila Neuromuscular Junction Morphology

Two image analysis algorithms, "Drosophila NMJ Morphometrics" and "Drosophila NMJ Bouton Morphometrics" were created, to automatically quantify nine morphological features of the Drosophila neuromuscular junction (NMJ).

Synaptic morphology is tightly related to synaptic efficacy, and in many cases morphological synapse defects ultimately lead to synaptic malfunction. The ...

Focal Macropatch Recordings of Synaptic Currents from the Drosophila Larval Neuromuscular Junction

Drosophila neuromuscular junction (NMJ) is an excellent model system to study glutamatergic synaptic transmission. We describe the technique of focal macropatch recordings of synaptic currents from visualized boutons at the Drosophila larval NMJ. This technique requires customized fabrication of recording micropipettes, as well as a compound microscope equipped with a high magnification, long-distance water immersion objective, differential interference contrast (DIC) optics, and a fluorescent attachment. The recording electrode is positioned on the top of a selected synaptic bouton visualized with DIC optics, epi-fluorescence, or both. The advantage of this technique is that it allows monitoring the synaptic activity of a limited number of sites of release. The recording electrode has&#160;a diameter of several microns, and the release sites positioned outside of the electrode rim do&#160;not significantly affect the recorded currents. The recorded synaptic currents have fast kinetics and can be readily resolved. These advantages are especially important for the studies of mutant fly lines with enhanced spontaneous or asynchronous synaptic activity.

Focal Macropatch Recordings of Synaptic Currents from the Drosophila Larval Neuromuscular Junction

Synaptic currents can be recorded focally from visualized synaptic boutons at the Drosophila third instar larvae neuromuscular junction. This technique enables monitoring the activity of a single synaptic bouton.

Drosophila neuromuscular junction (NMJ) is an excellent model system to study glutamatergic synaptic transmission. We describe the technique of focal ...