Name: the preparation of oblique spinal cord slices for ventral root stimulation
Uploaded: 2016-10-13T13:00:00
Description: Watch this Scientific Journal Video about The Preparation of Oblique Spinal Cord Slices for Ventral Root Stimulation at JoVE.com

The authors thank Marin Manuel and Olivia Goldman-Szwajkajzer for their help in taking the photographs. The authors also thank Arjun Masukar and Tobias Bock for proofreading the manuscript. Financial supports were provided by the Agence Nationale pour la Recherche (HYPER-MND, ANR-2010-BLAN-1429-01), the NIH-NINDS (R01NS077863), the Thierry Latran Foundation (OHEX Project), the French association for myopathy (grant number 16026) and Target ALS are gratefully acknowledged. Felix Leroy was the recipient of a &#34;Contrat Doctoral&#34; from the Ecole Normale Sup&#233;rieure, Cachan.

&#160;The experiments were performed in accordance with European directives (86/609/CEE and 2010-63-UE) and French legislation, and&#160;were approved by the Paris Descartes University ethics committee.
1. Spinal Cord Slice Preparation
<ol>
	<li>Prepare the following solutions daily or one day in advance. If kept overnight, bubble with 95% O2 and 5% CO2 and keep refrigerated in tightly closed bottles.
	<ol>
		<li>Prepare Low Na + artificial cerebrospi...

<ol>
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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gower's+tract+and+spinal+border+cells.">Gower's tract and spinal border cells.</a> Brain. 63, 123-124 (1940).</li><li>Morin, F., Schwartz, H. G., O'Leary, J. 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Oblique slicing of the spinal cord is important since it allows for unilateral stimulation of motoneuron pools and Renshaw cells at a single vertebral segment in a reliable, comprehensive&#160;and specific way. Furthermore, it allows for a quick, elegant&#160;and non-ambiguous identification of recorded motoneurons. Next, we will highlight&#160;the advantages of this&#160;technique compared to other slice preparation methods, and then we will stress out&#160;the most common pitfalls to avoid while performing this procedu...

Historically, motoneuron recordings using sharp-electrode were conducted in vivo on large animals such as&#160;cats or rats1 or on an isolated whole spinal cord in&#160;mice2. The emergence of the patch-clamp recording technique during the 1980s, called for direct access to the motoneuron somas as sealing needed to be achieved under visual guidance. Thus, spinal cord slice preparation has been readily achieved since the early 1990s3. However, early slice preparation often did not allow for the stimulation of the ventral roots. To the best of our knowledge, only two studies have reported successful stimulation of the ventral roots in transverse slices, and none was obtained from mice4,5.
In this article we present a technique to achieve viable spinal cord slices of neonatal mice (P2 - P11) in which the motoneuron&#160;pool&#160;retains its&#160;ventral root departing&#160;axons. Ventral root stimulation triggers antidromic action potential back into the somas of the motoneuron&#160;pool&#160;exiting from the same ventral root. It also excites the motoneuron collateral targets,&#160;other motoneurons6-10 and the Renshaw cells11-13. Since only motoneurons&#160;send their axons down the ventral roots, we use the recording of antidromic action potentials as a simple and definitive way to physiologicaly identify motoneurons10.
In addition to using potentially non-inclusive or misleading electrophysiological and morphological&#160;criterions to confirm the motoneuron&#160;identity, recent studies on spinal cord motoneurons also relied on tedious and&#160;time-consuming post&#160;hoc stainings16. Such identification is usually performed only on a sample of the recorded cells. Other identification strategies rely&#160;on mouse lines in which the motoneurons express endogenous fluorescence17-19. However, using genetically encoded markers may be difficult at a young age when marker expression is still variable or if the study already requires using a transgenic mouse line. Alternatively, antidromic action potential recordings can be performed routinely on all mice from the onset of cell recording. Experimenters working on intact spinal cord preparations in the cat, rat and mouse, have reliably used such identification techniques since the 1950&#39;s1,2,20,21. In optimal conditions, we were able to elicit antidromic action potentials from virtually all of the recorded motoneurons.
Furthermore, ventral root stimulation can be used to reliably excite other motoneurons22,23&#160;or their targets. the&#160;Renshaw cells10,24,25. We present here applications of the ventral root stimulation in the form of antidromic action potential recordings from motoneuron somas, as well as excitation of Renshaw cells.

<table >
	<tbody>
		<tr >
			<td >Na-kynurenate</td>
			<td >ABCAM</td>
			<td >ab120256</td>
			<td >dissolves better then other brands</td>
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		<tr >
			<td >KCl</td>
			<td >Sigma</td>
			<td >P3911</td>
			<td></td>
		</tr>
		<tr >
			<td >NaH2PO4</td>
			<td >Sigma</td>
			<td >P5655</td>
			<td></td>
		</tr>
		<tr >
			<td >sucrose&#160;</td>
			<td >Sigma</td>
			<td >S9378</td>
			<td></td>
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		<tr >
			<td >NaHCO3&#160;</td>
			<td >Sigma</td>
			<td >S6014</td>
			<td></td>
		</tr>
		<tr >
			<td >CaCl2&#160;</td>
			<td >G Biosciences</td>
			<td >R040</td>
			<td></td>
		</tr>
		<tr >
			<td >MgCl2&#160;</td>
			<td >Quality Biological</td>
			<td >351-033-721</td>
			<td></td>
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		<tr >
			<td >glucose&#160;</td>
			<td >Sigma</td>
			<td >G5767</td>
			<td></td>
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			<td >ascorbic acid&#160;</td>
			<td >Sigma</td>
			<td >A5960</td>
			<td></td>
		</tr>
		<tr >
			<td >Na-pyruvate&#160;</td>
			<td >Sigma</td>
			<td >P2250</td>
			<td></td>
		</tr>
		<tr >
			<td >K-gluconate&#160;</td>
			<td >Sigma</td>
			<td >P1847</td>
			<td></td>
		</tr>
		<tr >
			<td >EGTA&#160;</td>
			<td >Sigma</td>
			<td >E3889</td>
			<td></td>
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			<td >HEPES&#160;</td>
			<td >Sigma</td>
			<td >H4034</td>
			<td></td>
		</tr>
		<tr >
			<td >NaCl</td>
			<td >Sigma</td>
			<td >S9888</td>
			<td></td>
		</tr>
		<tr >
			<td >Agar</td>
			<td>Sigma</td>
			<td>A9799</td>
			<td></td>
		</tr>
		<tr >
			<td >QX-314</td>
			<td >Alomone</td>
			<td>Q150</td>
			<td></td>
		</tr>
		<tr >
			<td >Mg-ATP</td>
			<td>Sigma</td>
			<td >A9187</td>
			<td></td>
		</tr>
		<tr >
			<td >CsOH</td>
			<td>Sigma</td>
			<td >232041</td>
			<td></td>
		</tr>
		<tr >
			<td >Na-GTP</td>
			<td>Sigma</td>
			<td >51120</td>
			<td></td>
		</tr>
		<tr >
			<td >gluconic acid</td>
			<td>Sigma</td>
			<td >G1951</td>
			<td></td>
		</tr>
		<tr >
			<td >Cesium hydroxide solution</td>
			<td>Sigma</td>
			<td >232041</td>
			<td></td>
		</tr>
		<tr >
			<td >KOH</td>
			<td>Sigma</td>
			<td >P5958</td>
			<td></td>
		</tr>
		<tr >
			<td >Vannas Spring Scissors - 2.5mm&#160;</td>
			<td >FST</td>
			<td>15000-08</td>
			<td>only use for cutting the dura, might get damaged if cutting bones</td>
		</tr>
		<tr >
			<td >Stimulator</td>
			<td>A-M Systems</td>
			<td colspan="2">Isolated Pulse Stimulator Model 2100</td>
		</tr>
		<tr >
			<td >Vibratome</td>
			<td >Campden</td>
			<td >Vibrating Microtome 7000 - Model 7000smz-2</td>
			<td></td>
		</tr>
	</tbody>
</table>

the preparation of oblique spinal cord slices for ventral root stimulation

Electrophysiological recordings from spinal cord slices have proven to be a valuable technique to investigate a wide range of questions, from cellular to network properties. We show how to prepare viable oblique slices of the spinal cord of young mice (P2 - P11). In this preparation, the motoneurons retain&#160;their axons coming out from the ventral roots of the&#160;spinal cord. Stimulation of these axons elicits back-propagating action potentials invading the motoneuron&#160;somas and exciting the motoneuron&#160;collaterals within the spinal cord. Recording of antidromic action potentials is an immediate, definitive and elegant way to characterize motoneuron identity, which surpasses&#160;other identification methods. Furthermore, stimulating the motoneuron collaterals is a simple and reliable way to excite the collateral targets of the motoneurons within the spinal cord, such as other motoneurons or Renshaw cells. In this protocol, we present antidromic recordings from the motoneuron somas as well as Renshaw cell excitation, resulting from ventral root stimulation.

Confirmation of Motoneuron Identity Using Antidromic Action Potentials
Cell targeting
Motoneurons are found in the ventral horn (visible in red in Figure 2C). Start from the bundle of axons forming the ventral root and go up until the bundle disperses fully and one starts seeing large cells (long soma axis, above&#160;20...

Watch this Scientific Journal Video about The Preparation of Oblique Spinal Cord Slices for Ventral Root Stimulation at JoVE.com

The Preparation of Oblique Spinal Cord Slices for Ventral Root Stimulation

We show how to prepare oblique slices of the spinal cord in young mice. This preparation allows for the stimulation of the ventral roots.

Electrophysiological recordings from spinal cord slices have proven to be a valuable technique to investigate a wide range of questions, from cellular to ...

The overall goal of this procedure is to prepare oblique slices of the spinal cord that allow for the stimulation of the ventral roots. The main advantage of this technique is that it allows motoneural identifications for ventral-root stimulation and to study the ventral cells enervated by motoneural axon collaterals. We first had the idea for this method when needing a reliable way to stimulate ventral cells.Individuals new to this method will struggle because of the difficulty to properly execute the different steps of the dissection. Begin by perfusing a P2 to P11 mouse with low-sodium ACSF. After decapitating the mouse and removing the skin on the back, make two cuts through the shoulders and down the rib cage.Then, cut the spinal cord as low as possible in the caudal section to isolate the vertebral column and ribs from the lower part of the animal. Flip the vertebral column and remove the viscera still attached to the ribs. Transfer the vertebral column to another smaller, silicon-filled Petri dish.Add cold ACSF and bubble with carbogen and use four insect pins to hold the tissue dorsal-side up. Then perform a laminectomy of the dorsal side by first inserting the tip of fine scissors between the bone and the spinal cord and cutting the bone from the rostral end, making sure to stay away from the white matter. Alternate the cuts on each side while using tweezers to hold the band of bone already cut away.Next, use small tweezers to lift the dura and small scissors to cut along the rostral caudal access on both sides. Removal of the dura is a critical step. It is well worth spending a few extra minutes to do this thoroughly.Once the dura is removed, use a blunt glass tip to gently push cord towards the left side of the groove formed by half-cut spinal column. Then cut the ventral and dorsal roots on the bright side as far as possible from where they enter the cord. Repeat the operation on the left side, always going from rostral to caudal.After dissection, slip the spinal cord out of the vertebral column. Then use a small insect pin to secure the cord for the dorsal surface-up. Delicately remove any pieces of attached membrane.Once cleaned, trim both ends of the cord and insert a bent insect pin into the anterior part of the cord to mark its orientation. Then transfer the spinal cord to ice-cold intracellular solution. Next, cool the previously prepared molten agar on a mixture of ice and water.Stir the agar while measuring the temperature. When the temperature of the agar reaches 38 degrees Celsius, hold the spinal cord by the insect pin and immerse it in the agar, rostral-side down. Make sure the spinal cord is as straight as possible, away from the walls, with the caudal part slightly upward.Leave the beaker in the mixture of ice and water to allow the agar to solidify around the cord as quickly as possible. After solidification, cut the agar block containing the spinal cord in such a way that the base of the block is at a 35-degree angle with the lumbar part of the cord. The dorsal surface should be facing away from the base.Glue the block into the chamber of the vibratome, using cyanoacrylate glue. It is critical to mount the block correctly to maintain the continuity of the motor pools with the ventral roots from which they exit. Immerse the block in potassium gluconate solution.Set the vibratome parameters. Next, cut 350 400 micron-thick slices of the lumbar region, which is identifiable by its curvature and larger diameter. Transfer the suitable slices to ACSF at 34 degrees Celsius.Typically, there are four to five suitable slices with ventral roots extending two millimeters or more. After approximately 30 minutes at 34 degrees Celsius, cool the slices to room temperature, then begin the recording session. Prepare a box of various pipettes with tip diameters ranging from 40 to 170 microns in advance.To prepare the section pipettes, select pipettes with a long tapure. Then, using a diamond knife, make cuts at different positions and under a dissecting microscope, break each pipette by hitting the tip with tweezers. Next, remove the chamber from the recording microscope and place it under a dissecting microscope.Select a slice that contains a ventral root of sufficient length to be mounted on a suction-stimulation electrode. Mount the slice, orienting it with the ventral roots upward, then delicately cut the agar around the ventral roots while leaving the rest of the agar around the slice and place the grid to hold the sample down. Mount the chamber back onto the microscope and continuously perfuse the recording chamber with ACSF at a rate of one to two milliliters per minute at room temperature.Using a glass pipette filled with ACSF and connected to a syringe, suck one of the ventral roots. In order to achieve good stimulation of the ventral root, the pipette tip needs to be tight around the ventral root. Achieve patch-clamp recording of the desired cell type and record the effect of the ventral root stimulation as described previously.This image shows the results from voltage-clamp recording. The recordings of the upper panels are taken from different motoneurons than the ones in the bottom panels. The upper panel shows the antidromic response of a motoneuron to a one-volt stimulation in red, and a five-volt stimulation in black.The lower trace shows the orthodromic action potential response to a 20-volt stimulation in red, and a 30-volt stimulation in black. Black dots indicate stimulus timing. The double arrow heads emphasize the difference in latencies between ortho-and antidromic spikes.Here, current clamp recordings are shown. The upper panel shows the antidromic response to 10-volt and 15-volt stimulations in red and black, respectively. The lower panel shows the orthodromic response to 25-and 40-volt stimulations in red and black, respectively.Again, the stimulus timing and differences in latencies are indicated. This image of the Renshaw cell pool was acquired using an oblique condenser and a 20x objective. Note the motoneuron axons merging into the ventral root as shown by the arrow.This image of the same region was taken using a 40x objective. Putative Renshaw cells are indicated with arrow heads. Shown here is a voltage-clamp recording of a Renshaw cell following stimulation of the ventral root, indicated by the black dot.QX-314 in the intracellular solution prevented the cell from firing and glycine and gaba responses were blocked by 3 micromolar gabazine and one micromolar strychnine, respectively. The red trace is the average of the gray ones. Once mastered, this technique can be performed in 20 or 30 minutes.While attempting this procedure, it's important to remember to keep the preparation in cold medium at all time. After watching this video, you should have a good understanding of how to prepare oblique slices of spinal cord suitable for ventral-root stimulation. Ventral-root stimulation can be used to easily confirm the motoneural identity, and more importantly, to reliably stimulate the ventral cells.

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