This work was made possible thanks to financial support from the Fondation pour la Recherche M&eacute;dicale (FRM), the Milton Safenowitz PostDoctoral Fellowship for ALS Research (ALS Association), NIH NINDS Grants NS05462 and NS034382, and ANR Grant HyperMND.

1. Step One
Pre-anesthetic medication: 10-15 min before the induction of anesthesia, inject atropine (0.20 mg/kg) and methylprenidsolone (0.05 mg) sub-cutaneously to prevent salivation and oedema, respectively.
2. Step Two
Induction of anesthesia: inject pentobarbital sodium (70 mg/kg) or a mixture of ketamine/xylazine (100 mg/kg and 10 mg/kg, respectively) intra-peritoneally. Let the mouse go under until no toe pinch reflex can be obtained. ...

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The preparation described here is the first that allows, in the adult mouse, simultaneous intracellular recording of a lumbar motoneuron and the measurement of the force produced by the muscle fibers innervated by its axon.
Because of the small size of the animal, the surgical skills required for this preparation can be challenging to acquire. However, once those skills are mastered, the whole surgery can be performed in three hours, and the animals can survive for up to 7 more hours after th...

A correction was made to <a href="http://www.jove.com/video/4312">Simultaneous Intracellular Recording of a Lumbar Motoneuron and the Force Produced by its Motor Unit in the Adult Mouse In vivo</a>. There was an error in the name of one author, Marin Manuel. The author's name has been corrected to:
Marin Manuel 
 
instead of: 
 
Manuel Marin

A correction to author list has been made for article <a href="http://www.jove.com/video/4312">Simultaneous Intracellular Recording of a Lumbar Motoneuron and the Force Produced by its Motor Unit in the Adult Mouse In vivo</a>.

Erratum: Simultaneous Intracellular Recording of a Lumbar Motoneuron and the Force Produced by its Motor Unit in the Adult Mouse In Vivo

<table border="1">
 <tbody>
 <tr>
 <td>Name of the reagent</td>
 <td>Company</td>
 <td>Catalogue number</td>
 <td>Comments (optional)</td>
 </tr>
 <tr>
 <td>Atropine sulfate</td>
 <td>Aguettant</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Methylprenidsolone</td>
 <td>Pfizer</td>
 <td>Solu-Medrol</td>
 <td></td>
 </tr>
 <tr>
 <td>Sodium pentobarbitone</td>
 <td>Sanofi-Aventis</td>
 <td>Pentobarbital</td>
 <td></td>
 </tr>
 <tr>
 <td>Ketamine</td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Xylazine</td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Glucose</td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Plasma expander</td>
 <td>Roger Bellon</td>
 <td>Plasmagel</td>
 <td></td>
 </tr>
 <tr>
 <td>Blunt scissors</td>
 <td>FST</td>
 <td>14079-10</td>
 <td></td>
 </tr>
 <tr>
 <td>Blunt fine scissors</td>
 <td>FST</td>
 <td>15025-10</td>
 <td></td>
 </tr>
 <tr>
 <td>Vannas Spring Scissors</td>
 <td>FST</td>
 <td>15002-08</td>
 <td></td>
 </tr>
 <tr>
 <td>Fine forceps serrated</td>
 <td>FST</td>
 <td>11370-32</td>
 <td></td>
 </tr>
 <tr>
 <td>Fine forceps serrated</td>
 <td>FST</td>
 <td>11370-31</td>
 <td></td>
 </tr>
 <tr>
 <td>Cunningham Spinal Adaptor</td>
 <td>Stoelting Co.</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Kwik-Cast sealant</td>
 <td>WPI</td>
 <td>#KWIK-CAST </td>
 <td></td>
 </tr>
 <tr>
 <td>Ventilator</td>
 <td>CWE Inc</td>
 <td>SAR-830/AP</td>
 <td></td>
 </tr>
 <tr>
 <td>Capnograph</td>
 <td>CWE Inc</td>
 <td>&mu;capstar</td>
 <td></td>
 </tr>
 <tr>
 <td>Heating blanket</td>
 <td>Harvard Apparatus</td>
 <td>507221F</td>
 <td></td>
 </tr>
 <tr>
 <td>Intracellular amplifier</td>
 <td>Axon Instruments</td>
 <td>Axoclamp 2B</td>
 <td></td>
 </tr>
 <tr>
 <td>Pipette puller</td>
 <td>Sutter Instruments</td>
 <td>P-97</td>
 <td></td>
 </tr>
 <tr>
 <td>KCl</td>
 <td>Sigma-Aldrich</td>
 <td>P9333-500G</td>
 <td></td>
 </tr>
 </tbody>
</table>

simultaneous intracellular recording of a lumbar motoneuron and the force produced by its motor unit in the adult mouse in vivo

The spinal motoneuron has long been a good model system for studying neural function because it is a neuron of the central nervous system with the unique properties of (1) having readily identifiable targets (the muscle fibers) and therefore having a very well-known function (to control muscle contraction); (2) being the convergent target of many spinal and descending networks, hence the name of "final common pathway"; and (3) having a large soma which makes it possible to penetrate them with sharp intracellular electrodes. Furthermore, when studied in vivo, it is possible to record simultaneously the electrical activity of the motoneurons and the force developed by their muscle targets. Performing intracellular recordings of motoneurons in vivo therefore put the experimentalist in the unique position of being able to study, at the same time, all the compartments of the "motor unit" (the name given to the motoneuron, its axon, and the muscle fibers it innervates1): the inputs impinging on the motoneuron, the electrophysiological properties of the motoneuron, and the impact of these properties on the physiological function of the motoneurons, i.e. the force produced by its motor unit. However, this approach is very challenging because the preparation cannot be paralyzed and thus the mechanical stability for the intracellular recording is reduced. Thus, this kind of experiments has only been achieved in cats and in rats. However, the study of spinal motor systems could make a formidable leap if it was possible to perform similar experiments in normal and genetically modified mice.
For technical reasons, the study of the spinal networks in mice has mostly been limited to neonatal in vitro preparations, where the motoneurons and the spinal networks are immature, the motoneurons are separated from their targets, and when studied in slices, the motoneurons are separated from most of their inputs. Until recently, only a few groups had managed to perform intracellular recordings of motoneurons in vivo2-4 , including our team who published a new preparation which allowed us to obtain very stable recordings of motoneurons in vivo in adult mice5,6. However, these recordings were obtained in paralyzed animals, i.e. without the possibility to record the force output of these motoneurons. Here we present an extension of this original preparation in which we were able to obtain simultaneous recordings of the electrophysiological properties of the motoneurons and of the force developed by their motor unit. This is an important achievement, as it allows us to identify the different types of motoneurons based on their force profile, and thereby revealing their function. Coupled with genetic models disturbing spinal segmental circuitry7-9, or reproducting human disease10,11, we expect this technique to be an essential tool for the study of spinal motor system.

Figure 1 shows how to identify a motoneuron from the Triceps Surae group after penetration. At low stimulation intensity, only a monosynaptic EPSP can be observed (Figure 1A). At higher intensity, the EPSP might be large enough to trigger an "orthodromic" spike (Figure 1B). At even higher stimulation intensity, an all-or-none antidromic spike appears, with a shorter latency than the monosynaptic EPSP (Figure 1C). If enough current is injected through the...

Watch this Scientific Journal Video about Simultaneous Intracellular Recording of a Lumbar Motoneuron and the Force Produced by its Motor Unit in the Adult Mouse In vivo at JoVE.com

Simultaneous Intracellular Recording of a Lumbar Motoneuron and the Force Produced by its Motor Unit in the Adult Mouse In vivo

This new method permits the simultaneous intracellular recording of a single adult mouse motoneuron and the measurement of the force produced by its muscle fibers. The combined investigation of the electrical and mechanical properties of motor units in normal and genetically modified animals is a breakthrough for the study of the neuromuscular system.

Simultaneous Intracellular Recording of a Lumbar Motoneuron and the Force Produced by its Motor Unit in the Adult Mouse In vivo

The  spinal motoneuron has long been a good model system for studying neural  function because it is a neuron of the central nervous system with the ...

simultaneous-intracellular-recording-lumbar-motoneuron-force-produced

Research

JoVE Journal

Neuroscience

14.5K vistas.  Northwestern University Feinberg School of Medicine. Este nuevo método permite la grabación simultánea intracelular de una motoneuron adulto solo ratón y la medición de la fuerza producida por sus fibras musculares. La investigación combinada de las propiedades eléctricas y mecánicas de las unidades motoras en los animales normales y genéticamente modificadas es un gran avance para el estudio del sistema neuromuscular.