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

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 ...

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 ...

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

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 ...

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

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 ...

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. ...

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, ...

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

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 ...

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 ...

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

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 ...

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

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 ...