Name: levator auris longus preparation for examination of mammalian neuromuscular transmission under voltage clamp conditions
Uploaded: 2018-05-05T14:00:00
Description: Watch this Scientific Journal Video about Levator Auris Longus Preparation for Examination of Mammalian Neuromuscular Transmission Under Voltage Clamp Conditions at JoVE.com

We thank Dr. Mark M. Rich and Daniel Miranda for editorial comments, Ahmad Khedraki for helping establish this technique, and Wright State University for financial support (startup fund to A.A.V.).

All animal procedures were performed in accordance with the Animal Care and Use Committee of Wright State University.
1. Mouse Euthanasia
<ol>
	<li>In a fume hood, place the mouse in an airtight glass anesthetizing chamber.</li>
	<li>Expose the mouse via inhalation to a lethal dose of isoflurane (saturating, or ~25%). Leave the mouse in the chamber until no breathing can be observed.</li>
	<li>Remove the mouse from the chamber and perform a cervical dislocation as a secondary method of eutha...

<ol>
	<li>Angaut-Petit, D., Molgo, J., Connold, A. L., Faille, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+levator+auris+longus+muscle+of+the+mouse:+a+convenient+preparation+for+studies+of+short-+and+long-term+presynaptic+effects+of+drugs+or+toxins.">The levator auris longus muscle of the mouse: a convenient preparation for studies of short- and long-term presynaptic effects of drugs or toxins.</a> Neurosci Lett. 82 (1), 83-88 (1987).</li><li>Erzen, I., Cvetko, E., Obreza, S., Angaut-Petit, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fiber+types+in+the+mouse+levator+auris+longus+muscle:+a+convenient+preparation+to+study+muscle+and+nerve+plasticity.">Fiber types in the mouse levator auris longus muscle: a convenient preparation to study muscle and nerve plasticity.</a> J Neurosci Res. 59 (5), 692-697 (2000).</li><li>Bertone, N. I., 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=Carbonic+anhydrase+inhibitor+acetazolamide+shifts+synaptic+vesicle+recycling+to+a+fast+mode+at+the+mouse+neuromuscular+junction.">Carbonic anhydrase inhibitor acetazolamide shifts synaptic vesicle recycling to a fast mode at the mouse neuromuscular junction.</a> Synapse. , (2017).</li><li>Garcia-Chacon, L. E., Nguyen, K. T., David, G., Barrett, E. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extrusion+of+Ca2++from+mouse+motor+terminal+mitochondria+via+a+Na+-Ca2++exchanger+increases+post-tetanic+evoked+release.">Extrusion of Ca2+ from mouse motor terminal mitochondria via a Na+-Ca2+ exchanger increases post-tetanic evoked release.</a> J Physiol. 574 (Pt 3), 663-675 (2006).</li><li>Murray, L. M., 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=Selective+vulnerability+of+motor+neurons+and+dissociation+of+pre-+and+post-synaptic+pathology+at+the+neuromuscular+junction+in+mouse+models+of+spinal+muscular+atrophy.">Selective vulnerability of motor neurons and dissociation of pre- and post-synaptic pathology at the neuromuscular junction in mouse models of spinal muscular atrophy.</a> Hum Mol Genet. 17 (7), 949-962 (2008).</li><li>Nadal, L., 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=Presynaptic+muscarinic+acetylcholine+autoreceptors+(M1,+M2+and+M4+subtypes),+adenosine+receptors+(A1+and+A2A)+and+tropomyosin-related+kinase+B+receptor+(TrkB)+modulate+the+developmental+synapse+elimination+process+at+the+neuromuscular+junction.">Presynaptic muscarinic acetylcholine autoreceptors (M1, M2 and M4 subtypes), adenosine receptors (A1 and A2A) and tropomyosin-related kinase B receptor (TrkB) modulate the developmental synapse elimination process at the neuromuscular junction.</a> Mol Brain. 9 (1), 67 (2016).</li><li>Rousse, I., St-Amour, A., Darabid, H., Robitaille, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synapse-glia+interactions+are+governed+by+synaptic+and+intrinsic+glial+properties.">Synapse-glia interactions are governed by synaptic and intrinsic glial properties.</a> Neuroscience. 167 (3), 621-632 (2010).</li><li>Rozas, J. L., Gomez-Sanchez, L., Tomas-Zapico, C., Lucas, J. J., Fernandez-Chacon, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+neurotransmitter+release+at+the+neuromuscular+junction+in+a+mouse+model+of+polyglutamine+disease.">Increased neurotransmitter release at the neuromuscular junction in a mouse model of polyglutamine disease.</a> J Neurosci. 31 (3), 1106-1113 (2011).</li><li>Takeuchi, A., Takeuchi, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Further+analysis+of+relationship+between+end-plate+potential+and+end-plate+current.">Further analysis of relationship between end-plate potential and end-plate current.</a> J Neurophysiol. 23, 397-402 (1960).</li><li>McLachlan, E. M., Martin, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non+linear+summation+of+end+plate+potentials+in+the+frog+and+mouse.">Non linear summation of end plate potentials in the frog and mouse.</a> The Journal of Physiology. 311 (1), 307-324 (1981).</li><li>Obis, 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=The+novel+protein+kinase+C+epsilon+isoform+modulates+acetylcholine+release+in+the+rat+neuromuscular+junction.">The novel protein kinase C epsilon isoform modulates acetylcholine release in the rat neuromuscular junction.</a> Mol Brain. 8 (1), 80 (2015).</li><li>Silveira, P. E., 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=Ryanodine+and+inositol+triphosphate+receptors+modulate+facilitation+and+tetanic+depression+at+the+frog+neuromuscular+junction.">Ryanodine and inositol triphosphate receptors modulate facilitation and tetanic depression at the frog neuromuscular junction.</a> Muscle Nerve. 52 (4), 623-630 (2015).</li><li>Wood, S. J., Slater, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safety+factor+at+the+neuromuscular+junction.">Safety factor at the neuromuscular junction.</a> Prog Neurobiol. 64 (4), 393-429 (2001).</li><li>Miranda, D. 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=Progressive+Cl-+channel+defects+reveal+disrupted+skeletal+muscle+maturation+in+R6/2+Huntington's+mice.">Progressive Cl- channel defects reveal disrupted skeletal muscle maturation in R6/2 Huntington's mice.</a> J Gen Physiol. 149 (1), 55-74 (2017).</li><li>Waters, C. W., Varuzhanyan, G., Talmadge, R. J., Voss, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Huntington+disease+skeletal+muscle+is+hyperexcitable+owing+to+chloride+and+potassium+channel+dysfunction.">Huntington disease skeletal muscle is hyperexcitable owing to chloride and potassium channel dysfunction.</a> Proceedings of the National Academy of Sciences of the United States of America. 110 (22), 9160-9165 (2013).</li><li>Khedraki, 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=Depressed+Synaptic+Transmission+and+Reduced+Vesicle+Release+Sites+in+Huntington's+Disease+Neuromuscular+Junctions.">Depressed Synaptic Transmission and Reduced Vesicle Release Sites in Huntington's Disease Neuromuscular Junctions.</a> Journal of Neuroscience. 37 (34), 8077-8091 (2017).</li><li>Greene, E. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The anatomy of the rat. , (1955).</li><li>Magrassi, L., Purves, D., Lichtman, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescent+probes+that+stain+living+nerve+terminals.">Fluorescent probes that stain living nerve terminals.</a> J Neurosci. 7 (4), 1207-1214 (1987).</li><li>Jack, J. J. B., Noble, D., Tsien, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Electric current flow in excitable cells. , (1983).</li><li>Voss, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extracellular+ATP+inhibits+chloride+channels+in+mature+mammalian+skeletal+muscle+by+activating+P2Y(1)+receptors.">Extracellular ATP inhibits chloride channels in mature mammalian skeletal muscle by activating P2Y(1) receptors.</a> Journal of Physiology-London. 587 (23), 5739-5752 (2009).</li><li>Albuquerque, E. X., McIsaac, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+and+slow+mammalian+muscles+after+denervation.">Fast and slow mammalian muscles after denervation.</a> Experimental Neurology. 26 (1), 183-202 (1970).</li><li>Santafe, M. M., Urbano, F. J., Lanuza, M. A., Uchitel, O. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+types+of+calcium+channels+mediate+transmitter+release+during+functional+recovery+of+botulinum+toxin+type+A-poisoned+mouse+motor+nerve+terminals.">Multiple types of calcium channels mediate transmitter release during functional recovery of botulinum toxin type A-poisoned mouse motor nerve terminals.</a> Neuroscience. 95 (1), 227-234 (2000).</li><li>Gaffield, M. A., Betz, W. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptic+vesicle+mobility+in+mouse+motor+nerve+terminals+with+and+without+synapsin.">Synaptic vesicle mobility in mouse motor nerve terminals with and without synapsin.</a> J Neurosci. 27 (50), 13691-13700 (2007).</li><li>Zhang, Z. S., Nguyen, K. T., Barrett, E. F., David, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vesicular+ATPase+Inserted+into+the+Plasma+Membrane+of+Motor+Terminals+by+Exocytosis+Alkalinizes+Cytosolic+pH+and+Facilitates+Endocytosis.">Vesicular ATPase Inserted into the Plasma Membrane of Motor Terminals by Exocytosis Alkalinizes Cytosolic pH and Facilitates Endocytosis.</a> Neuron. 68 (6), 1097-1108 (2010).</li></ol>

Described here is the preparation and use of the mouse LAL muscle for the measurement of neuromuscular transmission under current- or voltage-clamp conditions. There are several important points to consider for dissecting out the LAL. Cleaning excess connective tissue from the muscle aids in electrode impalement, as the electrodes can snag the connective tissue when positioning them for impalement. However, only remove connective tissue that can be taken away easily to limit the chances of damaging the muscle. The isolat...

Studying synaptic transmission at the neuromuscular junction provides insights into the dynamic relationship between the nervous and skeletal muscular systems and is an excellent model for examining synaptic physiology. The levator auris longus (LAL) is a thin muscle, allowing for the neuromuscular junctions to be easily visualized. Previous reports have described the convenience of using the LAL to examine synaptic drugs and toxins and have characterized the skeletal muscle fiber type characteristics of the LAL1,2. Numerous studies have used the LAL to examine neuromuscular physiology3,4,5,6,7,8. For electrophysiology, the ability to easily observe LAL neuromuscular junctions allows for the accurate placement of microelectrodes at the motor endplate and greatly reduces space clamp issues in recording synaptic transmission. Current-clamp recordings of the muscle membrane properties, such as the membrane time constant (&#964;m) and input resistance (Rin) are readily obtained. Furthermore, these properties can be measured from the same muscle fibers used to record neuromuscular transmission, allowing for a direct comparison of synaptic function to the muscle membrane properties. Analysis of these data can provide key insights into the physical mechanisms of many neuromuscular diseases and states of altered activity.
A key aspect of the technique described here is the use of voltage-clamp&#160;for synaptic recordings, which are not subject to the non-linearities encountered in current-clamp&#160;and are independent of the muscle membrane properties. Advantages of using voltage-clamp as opposed to current-clamp to examine neuromuscular transmission were established by pioneering efforts in the 1950s9. Under current-clamp, EPPs that exceed 10-15 mV in amplitude are not a linear product of the mEPP amplitude9. For example, if the average mEPP is 1 mV, an EPP of 5 mV can be assumed to be the product of 5 mEPPs (QC of 5); whereas, an EPP of 40 mV will be the product of more than 40 mEPPs. This non-linearity at larger EPPs occurs because the driving force for the EPP, which is the difference between the membrane potential and equilibrium potential for the acetylcholine receptor (~-10 mV), substantially decreases during large EPPs. This issue is avoided in voltage-clamp experiments because the muscle membrane potential does not change during voltage-clamp experiments. A drawback is that voltage-clamp experiments are technically more difficult to complete than current-clamp recording. With this in mind, McLachlan and Martin developed a straightforward mathematical correction that accounts for non-linearities in current-clamp recordings of EPPs10. The corrections work well11,12,13, but importantly, assume that the muscle membrane properties have not been disrupted.
The muscle membrane properties are especially important to consider if studying conditions or disease states that disrupt the muscle. For example, skeletal muscle from the R6/2 transgenic model of Huntington&#39;s disease is hyperexcitable due to a progressive reduction in the resting chloride and potassium currents14,15. As a consequence, mEPPs and EPPs are amplified in the R6/2 skeletal muscle. Certainly, additional factors can alter mEPPs and EPPs. Work with a different model of Huntington&#39;s disease mice (R6/1) found changes in EPPs that seemed to be related to SNARE-proteins8. To assess the mechanisms causing altered neuromuscular transmission, it would be beneficial to eliminate the effects of altered muscle membrane properties by using a voltage-clamp. In a recent study, the R6/2 neuromuscular transmission was studied under both current- and voltage-clamp conditions using the technique described herein. The entirety of the motor endplates were voltage-clamped with less than 1% error by placing two microelectrodes within the length constant of the endplate16. It was shown that voltage-clamp and corrected current-clamp records yielded contrasting measurements of neuromuscular transmission in R6/2 muscle. This highlights that it may be difficult to correct EPPs for non-linearities if the muscle membrane properties have been altered and shows the benefits of obtaining voltage-clamp records that are independent of the muscle membrane properties. The protocol presented herein is ideal for examining conditions or disease states that affect synaptic transmission and the postsynaptic membrane properties.

<table border="0" cellpadding="0" cellspacing="0" width="806">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Olympus Compound Microscope</td>
			<td style="width:183px;">Olympus</td>
			<td style="width:119px;">BX51WI</td>
			<td style="width:288px;"></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">10x Objective</td>
			<td style="width:183px;">Olympus</td>
			<td style="width:119px;">UMPLFLN10XW</td>
			<td style="width:288px;"></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">40x Objective</td>
			<td style="width:183px;">Olympus</td>
			<td style="width:119px;">LUMPLFLN40XW</td>
			<td style="width:288px;"></td>
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			<td height="24" style="height:25px;width:216px;">Borosilicate Glass</td>
			<td style="width:183px;">Sutter Instruments</td>
			<td style="width:119px;">BF150-86-7.5</td>
			<td style="width:288px;"></td>
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			<td height="40" style="height:40px;width:216px;">CCD Camera</td>
			<td style="width:183px;">Santa Barbara Instruments Group</td>
			<td style="width:119px;">ST-7XMEI</td>
			<td style="width:288px;"></td>
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			<td height="29" style="height:29px;width:216px;">Axoclamp 900A Amplifier</td>
			<td style="width:183px;">Molecular Devices</td>
			<td style="width:119px;">2500&#8208;0179&#160;&#160;</td>
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			<td height="21" style="height:21px;width:216px;">Mater-9 Pulse Generator</td>
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			<td height="21" style="height:21px;width:216px;">Iso-flex Stimulus Isolator</td>
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			<td height="42" style="height:42px;width:216px;">pCLAMP 10 Data Acquisition and Analysis Software</td>
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			<td style="width:119px;">1-2500-0180</td>
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			<td height="21" style="height:21px;width:216px;">Concentric Bipolar Electrode</td>
			<td style="width:183px;">FHC</td>
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			<td height="21" style="height:21px;width:216px;">Ball-joint Manipulator</td>
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			<td height="52" style="height:52px;width:216px;">Non-metalic Syringes 34 Gauge</td>
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			<td height="21" style="height:21px;width:216px;">Nikon Stereomicroscope</td>
			<td style="width:183px;">Nikon</td>
			<td style="width:119px;">SMZ800N</td>
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			<td height="21" style="height:21px;width:216px;">No. 5 Forceps</td>
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			<td style="width:119px;">15006-09</td>
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			<td height="21" style="height:21px;width:216px;">No. 2 Forceps</td>
			<td style="width:183px;">Roboz</td>
			<td style="width:119px;">RS-5Q41</td>
			<td style="width:288px;"></td>
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			<td height="21" style="height:21px;width:216px;">Microdissecting Scissors</td>
			<td style="width:183px;">Roboz</td>
			<td style="width:119px;">RS-5912SC</td>
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			<td height="42" style="height:42px;width:216px;">Sylgard 184 Silicone Elastomer Kit</td>
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			<td align="right" style="width:119px;">2404019862</td>
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			<td height="21" style="height:21px;width:216px;">Hair Removal Cream</td>
			<td style="width:183px;">Nair</td>
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			<td height="27" style="height:27px;width:216px;">Grass SD9 Stimulator</td>
			<td style="width:183px;">Grass Medical</td>
			<td style="width:119px;"></td>
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			<td height="46" style="height:46px;width:216px;">Model P-1000 Micropipette Puller</td>
			<td style="width:183px;">Sutter Instruments</td>
			<td style="width:119px;">P-1000</td>
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			<td height="37" style="height:37px;width:216px;">Axon Digidata 1550 Low-noise Data Acuisition System</td>
			<td style="width:183px;">Molecular Devices</td>
			<td style="width:119px;"></td>
			<td style="width:288px;"></td>
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			<td style="width:183px;">Warner Instrument Corp.</td>
			<td style="width:119px;">LPF-8</td>
			<td style="width:288px;"></td>
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			<td style="width:183px;">Siskiyou Corp.</td>
			<td style="width:119px;">MX1641/45DL</td>
			<td style="width:288px;"></td>
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			<td height="44" style="height:44px;width:216px;">Right-handed Micromanipulator</td>
			<td style="width:183px;">Siskiyou Corp.</td>
			<td style="width:119px;">MX1641/45DR</td>
			<td style="width:288px;"></td>
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			<td height="44" style="height:44px;width:216px;">Single Motion Controler</td>
			<td style="width:183px;">Siskiyou Corp.</td>
			<td style="width:119px;">MC100e</td>
			<td style="width:288px;"></td>
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			<td height="161" style="height:161px;width:216px;">Crossed Roller Micromanipulator</td>
			<td style="width:183px;">Siskiyou Corp.</td>
			<td style="width:119px;">MX1641R</td>
			<td style="width:288px;">This was added to the Z-axis of the Left and Right-handed micromanipulators to allow the z axis to be motorized. This custom set-up is cheaper and less bulky than buying a 4-axis motorized micromanipulator. It also allows us to control both micromanipulators with one controller</td>
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			<td colspan="3" height="21" style="height:21px;width:517px;">All chemicals were orded from Fisher except,</td>
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			<td height="42" style="height:42px;width:216px;">BTS</td>
			<td style="width:183px;">Toronto Research Chemicals</td>
			<td style="width:119px;">B315190</td>
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			<td height="21" style="height:21px;width:216px;">CTX</td>
			<td style="width:183px;">Alomone Labs</td>
			<td style="width:119px;">C-270</td>
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			<td height="42" style="height:42px;width:216px;">4-Di-2-Asp</td>
			<td style="width:183px;">Molecular Probes</td>
			<td style="width:119px;"></td>
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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.

Figure 8 shows an example of the current pulses (Figure 8A) and the voltage responses (Figure 8B) from one LAL fiber under current-clamp from a 12-week-old wild type R6/2 mouse. The presence of mEPPs indicates that these records were taken from the motor endplate. The records were obtained in normal physiological saline solution. These current-clamp records can be analyzed to determine the Rin</...

Watch this Scientific Journal Video about Levator Auris Longus Preparation for Examination of Mammalian Neuromuscular Transmission Under Voltage Clamp Conditions at JoVE.com

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.

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 ...

The overall goal of this procedure is to isolate the levator auris longus muscle and its nerve in order to record synaptic currents at the neural muscular junction. This method can help answer key questions in synaptic physiology such as the end plate current size, quantal content, probability of release and relationships between neurotransmission and muscle excitability. The main advantage of this technique is the detailed electrophysiological recordings from a single synapse can easily be combined with live cell optical experiments.Though this method can provide insight into synaptic function and feedback communication between nerve and muscle, it can also be applied to other systems ranging from drosophila to mammals. Generally, individuals new to this method will struggle because the mammalian nerve muscle prep is fragile, particularly the nerve. Carefully acquiring and interpreting the subsequent voltage clamp data can also be challenging.Once mastered, this technique can be done in one hour if it is performed properly. Demonstrating the procedure will be Steve Burke from my laboratory. To begin this procedure, under a stereo-dissecting microscope, make a small incision in the skin on the back of the mouse at the level of the scapulae.Use a pair of microdissection scissors. Cut the skin over the head and the back. Next, pull up the skin along the incision near the scapulae.Cut the muscles that are inferior to the LAL by starting at the right scapula. Then, gently lift the cut tissue immediately to the right of the midline. Make a cut toward the left ear with the blades of the scissors pressed against the cranium to remove several layers of muscle that are inferior to the left LAL.Avoid cutting the nerve that innervates the LAL which wraps around the ear canal and enter the muscles on the medial side of the ear. Continue cutting through the ear canal keeping as much of the nerve attached as possible. Then, cut the fatty tissue behind the ear canal along the ventrolateral portion of the ear.Cut along the left scapula similar to the procedures done on the right side to remove the muscle completely from the mouse. Next, cut off the pinna of the ear along the base leaving the cartilaginous part of the ear attached to the LAL. Flip the muscle so that the inferior side is facing up.To isolate LAL muscle, place the LAL and the surrounding tissue into a Petri dish with a silicon elastomer bottom and pin the dissected tissue to the bottom. Wash the tissue frequently in a physiological saline solution. Then, place an insect pin through the ear canal to hold the prep in place.Using smaller pins, pin the remaining tissue on the opposite side of the midline of the LAL. Use a pair of forceps. Gently pull the skin up on the lateral portion of the ear to stretch the muscle out and place a small pin through the skin.Repeat this step until the tissue is well-secured to the dish. Remove the muscles that are covering the LAL and those bound to the LAL via connective tissue and are especially tight near the midline. Subsequently, pull up the overlying muscle layer and cut the connective tissue with the blades oriented toward the muscle layer being pulled.Cut toward the midline until about 3/4 of the way to the midline and keep removing muscle layers until only the LAL remains. During the cleaning process, ensure that the nerves are not damaged. Following that, remove some of the remaining connective tissue that is covering the LAL to aid in impalement of the electrodes.Only remove tissue that can be done easily without risk of damaging the LAL in the process. To identify the nerve that innervates the LAL, using a nerve stimulator, touch the nerves with the nerve stimulator. When the muscle contracts, the correct nerve has been identified.Then, carefully grab the tissue near the nerve and use spring scissors to separate the nerve from the tissue surrounding the ear. To minimize damage, keep most of the nerve embedded in some surrounding tissue which will be used later to secure the nerve to the recording dish. At this point, the investigator can take an hour break as long as the LAL is bathed in 20 milliliters or more of a physiological saline solution.Next, unpin and transfer the muscle to a stage insert under the dissection microscope for electrophysiology experiments. Pin the muscle at the ends and along its edge. Position the nerve perpendicular to the muscle fibers and pin it to the bottom of the dish through some excess tissue that was left intact at the end of the nerve.Keep the tissue bathed in a physiological saline solution at all times. For electrophysiology experiment, secure the perfusion chamber with the LAL to the microscope stage. Place the reference electrode into a cup filled with three-molar potassium chloride which is connected to the recording chamber via an agar bridge.At this point, position the nerve-stimulating electrode on the nerve. Expose the LAL prep to 4-Di-2-Asp for 10 minutes to achieve adequate florescence for neuromuscular junction visualization. After 10 minutes, exchange the 4-Di-2-Asp solution with the normal calcium solution.In the meantime, fill the glass capillaries with the appropriate solutions for the voltage-sensing and current-passing electrodes. Gently tap the capillary to remove any air bubbles and secure the filled capillary into the electrode holder on the headstage. Using an upright microscope with standard bright field and florescence illumination, look for a bright band of fluorescent green neuromuscular junctions running perpendicular to the muscle fibers along the prep with a low-magnification water-emersion objective.Then, switch to a higher magnification water-emersion objective to identify a neuromuscular junction on the top layer of muscle in order to examine with electrophysiology. Using primarily bright field, position the electrode above the muscle membrane within 100 microns of the identified neuromuscular junction. This figure shows an example of the current pulses and the voltage responses from one LAL fiber under current clamp from a 12-week-old wild-type R62 mouse.The records were obtained in normal physiological saline solution and the presence of mEPPs indicates that these records were taken from the motor end plate. Here is a representative recording of an EPC and two mEPCs obtained under voltage clamp condition. This figure shows the superimposed EPCs and mEPCs from a representative fiber.Once mastered, this technique can be done in one hour if it is performed properly. Following this procedure, other methods like live-cell imaging with membrane dyes such as FM143 or histology can be performed in order to answer questions related to vesicle release uptake or morphological changes. After its development, this technique paved the way for researchers in the field of physiology to explore synaptic transmission and nerve-cell communication in organisms ranging from drosophila to mammals.After watching this video, you should have a good understanding of how to isolate the innervated levator auris longus muscle in order to record synaptic currents at the neuromuscular junction. While attempting this procedure, it's important to remember to take great care in removing the muscle tissue adjoined to the LAL and isolating the nerve.

levator-auris-longus-preparation-for-examination-mammalian

Research

JoVE Journal

Neuroscience

Subcutaneous Administration of Muscarinic Antagonists and Triple-Immunostaining of the Levator Auris Longus Muscle in Mice

Hind limb muscles of rodents, such as gastrocnemius and tibialis anterior, are frequently used for in vivo pharmacological studies of the signals essential for the formation and maintenance of mammalian NMJs. However, drug penetration into these muscles after subcutaneous or intramuscular administration is often incomplete or uneven and many NMJs can remain unaffected. Although systemic administration with devices such as mini-pumps can improve the spatiotemporal effects, the invasive nature of this approach can cause confounding inflammatory responses and/or direct muscle damage. Moreover, complete analysis of the NMJs in a hind limb muscle is challenging because it requires time-consuming serial sectioning and extensive immunostaining. 
The mouse LAL is a thin, flat sheet of muscle located superficially on the dorsum of the neck. It is a fast-twitch muscle that functions to move the pinna. It contains rostral and caudal portions that originate from the midline of the cranium and extend laterally to the cartilaginous portion of each pinna. The muscle is supplied by a branch of the facial nerve that projects caudally as it exits the stylomastoid foramen. We and others have found LAL to be a convenient preparation that offers advantages for the investigation of both short and long-term in vivo effects of drugs on NMJs and muscles. First, its superficial location facilitates multiple local applications of drugs under light anesthesia. Second, its thinness (2-3 layers of muscle fibers) permits visualization and analysis of almost all the NMJs within the muscle. Third, the ease of dissecting it with its nerve intact together with the pattern of its innervation permits supplementary electrophysiological analysis in vitro9,5. Last, and perhaps most importantly, a small applied volume (&tilde;50&mu;l) easily covers the entire muscle surface, provides a uniform and prolonged exposure of all its NMJs to the drug and eliminates the need for a systemic approach1,8.

We describe procedures for repeated administration of inhibitors of muscarinic signaling to the levator auris longus (LAL) muscle of young adult mice and for subsequent immunostaining of its neuromuscular junctions (NMJs) in wholemounts. The LAL muscle has unique advantages for revealing in vivo pharmacological effects on NMJs.

Hind limb muscles of rodents, such as gastrocnemius and tibialis anterior, are frequently used for in vivo  pharmacological studies of the signals ...

Single Cell Measurement of Dopamine Release with Simultaneous Voltage-clamp and Amperometry

After its release into the synaptic cleft, dopamine exerts its biological properties via its pre- and post-synaptic targets1. The dopamine signal is terminated by diffusion2-3, extracellular enzymes4, and membrane transporters5. The dopamine transporter, located in the peri-synaptic cleft of dopamine neurons clears the released amines through an inward dopamine flux (uptake). The dopamine transporter can also work in reverse direction to release amines from inside to outside in a process called outward transport or efflux of dopamine5. More than 20 years ago Sulzer et al. reported the dopamine transporter can operate in two modes of activity: forward (uptake) and reverse (efflux)5. The neurotransmitter released via efflux through the transporter can move a large amount of dopamine to the extracellular space, and has been shown to play a major regulatory role in extracellular dopamine homeostasis6. Here we describe how simultaneous patch clamp and amperometry recording can be used to measure released dopamine via the efflux mechanism with millisecond time resolution when the membrane potential is controlled. For this, whole-cell current and oxidative (amperometric) signals are measured simultaneously using an Axopatch 200B amplifier (Molecular Devices, with a low-pass Bessel filter set at 1,000 Hz for whole-cell current recording). For amperometry recording a carbon fiber electrode is connected to a second amplifier (Axopatch 200B) and is placed adjacent to the plasma membrane and held at +700 mV. The whole-cell and oxidative (amperometric) currents can be recorded and the current-voltage relationship can be generated using a voltage step protocol. Unlike the usual amperometric calibration, which requires conversion to concentration, the current is reported directly without considering the effective volume7. Thus, the resulting data represent a lower limit to dopamine efflux because some transmitter is lost to the bulk solution.

The amperometric technique measures dopamine release from a single cell by detecting the oxidative current produced by spontaneous dopamine oxidization. Simultaneous voltage clamp and amperometry methodology reveal the mechanistic relationship between the overall "activity" of dopamine transporter and the regulatory role of this activity on the reverse transport of dopamine.

After its release into the synaptic cleft, dopamine exerts its biological properties via its pre- and post-synaptic targets1. The dopamine signal is ...

F1FO ATPase Vesicle Preparation and Technique for Performing Patch Clamp Recordings of Submitochondrial Vesicle Membranes

Mitochondria are involved in many important cellular functions including metabolism, survival1, development and, calcium signaling2. Two of the most important mitochondrial functions are related to the efficient production of ATP, the energy currency of the cell, by oxidative phosphorylation, and the mediation of signals for programmed cell death3.
The enzyme primarily responsible for the production of ATP is the F1FO-ATP synthase, also called ATP synthase4-5. In recent years, the role of mitochondria in apoptotic and necrotic cell death has received considerable attention. In apoptotic cell death, BCL-2 family proteins such as Bax enter the mitochondrial outer membrane, oligomerize and permeabilize the outer membrane, releasing pro-apoptotic factors into the cytosol6. In classic necrotic cell death, such as that produced by ischemia or excitotoxicity in neurons, a large, poorly regulated increase in matrix calcium contributes to the opening of an inner membrane pore, the mitochondrial permeability transition pore or mPTP. This depolarizes the inner membrane and causes osmotic shifts, contributing to outer membrane rupture, release of pro-apoptotic factors, and metabolic dysfunction. Many proteins including Bcl-xL7 interact with F1FO ATP synthase, modulating its function. Bcl-xL interacts directly with the beta subunit of F1FO ATP synthase, and this interaction decreases a leak conductance within the F1FOATPasecomplex, increasing the net transport of H+ by F1FO during F1FO ATPase activity8 and thereby increasing mitochondrial efficiency. To study the activity and modulation of the ATP synthase, we isolated from rodent brain submitochondrial vesicles (SMVs) containing F1FO ATPase. The SMVs retain the structural and functional integrity of the F1FO ATPase as shown in Alavian et al. Here, we describe a method that we have used successfully for the isolation of SMVs from rat brain and we delineate the patch clamp technique to analyze channel activity (ion leak conductance) of the SMVs.

F1FO ATPase Vesicle Preparation and Technique for Performing Patch Clamp Recordings of Submitochondrial Vesicle Membranes

A method to isolate submitochondrial vesicles enriched in F1FO ATP synthase complexes from rat brain is described. These vesicles allow the study of the activity of F1FO ATPase complex and its modulation using the technique of patch clamp recording.

Mitochondria are involved in many important cellular  functions including metabolism, survival1, development and, calcium signaling2. Two of the most ...

Monitoring Astrocyte Reactivity and Proliferation in Vitro Under Ischemic-Like Conditions

Ischemic stroke is a complex brain injury caused by a thrombus or embolus obstructing blood flow to parts of the brain. This leads to deprivation of oxygen and glucose, which causes energy failure and neuronal death. After an ischemic stroke insult, astrocytes become reactive and proliferate around the injury site as it develops. Under this scenario, it is difficult to study the specific contribution of astrocytes to the brain region exposed to ischemia. Therefore, this article introduces a methodology to study primary astrocyte reactivity and proliferation under an in vitro model of an ischemia-like environment, called oxygen glucose deprivation (OGD). Astrocytes were isolated from 1-4 day-old neonatal rats and the number of non-specific astrocytic cells was assessed using astrocyte selective marker Glial Fibrillary Acidic Protein (GFAP) and nuclear staining. The period in which astrocytes are subjected to the OGD condition can be customized, as well as the percentage of oxygen they are exposed to. This flexibility allows scientists to characterize the duration of the ischemic-like condition in different groups of cells in vitro. This article discusses the timeframes of OGD that induce astrocyte reactivity, hypertrophic morphology, and proliferation as measured by immunofluorescence using Proliferating Cell Nuclear Antigen (PCNA). Besides proliferation, astrocytes undergo energy and oxidative stress, and respond to OGD by releasing soluble factors into the cell medium. This medium can be collected and used to analyze the effects of molecules released by astrocytes in primary neuronal cultures without cell-to-cell interaction. In summary, this primary cell culture model can be efficiently used to understand the role of isolated astrocytes upon injury.

Monitoring Astrocyte Reactivity and Proliferation in Vitro Under Ischemic-Like Conditions

Ischemic stroke is a complex event in which the specific contribution of astrocytes to the affected brain region exposed to oxygen glucose deprivation (OGD) is difficult to study. This article introduces a methodology to obtain isolated astrocytes and study their reactivity and proliferation under OGD conditions.

Ischemic stroke is a complex brain injury caused by a thrombus or embolus obstructing blood flow to parts of the brain. This leads to deprivation of ...

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 ...

Electrophysiological Method for Whole-cell Voltage Clamp Recordings from Drosophila Photoreceptors

Whole-cell voltage clamp recordings from Drosophila melanogaster photoreceptors have revolutionized the field of invertebrate visual transduction, enabling the use of D. melanogaster molecular genetics to study inositol-lipid signaling and Transient Receptor Potential (TRP) channels at the single-molecule level. A handful of labs have mastered this powerful technique, which enables the analysis of the physiological responses to light under highly controlled conditions. This technique allows control over the intracellular and extracellular media; the membrane voltage; and the fast application of pharmacological compounds, such as a variety of ionic or pH indicators, to the intra- and extracellular media. With an exceptionally high signal-to-noise ratio, this method enables the measurement of dark spontaneous and light-induced unitary currents (i.e.&#160;spontaneous and quantum bumps) and macroscopic Light-induced Currents (LIC) from single D. melanogaster photoreceptors. This protocol outlines, in great detail, all the key steps necessary to perform this technique, which includes both electrophysiological and optical recordings. The fly retina dissection procedure for the attainment of intact and viable ex vivo isolated ommatidia in the bath chamber is described. The equipment needed to perform whole-cell and fluorescence imaging measurements are also detailed. Finally, the pitfalls in using this delicate preparation during extended experiments are explained.

Electrophysiological Method for Whole-cell Voltage Clamp Recordings from Drosophila Photoreceptors

Whole-cell recordings from Drosophila melanogaster photoreceptors enable the measurement of spontaneous dark bumps, quantum bumps, macroscopic responses to light, and current-voltage relationships under various conditions. In combination with D. melanogaster genetic manipulation tools, this method enables the study of the ubiquitous inositol-lipid signaling pathway and its target, the TRP channel.

Whole-cell voltage clamp recordings from Drosophila melanogaster photoreceptors have revolutionized the field of invertebrate visual transduction, ...

Slice Patch Clamp Technique for Analyzing Learning-Induced Plasticity

The slice patch clamp technique is a powerful tool for investigating learning-induced neural plasticity in specific brain regions. To analyze motor-learning induced plasticity, we trained rats using an accelerated rotor rod task. Rats performed the task 10 times at 30-s intervals for 1 or 2 days. Performance was significantly improved on the training days compared to the first trial. We then prepared acute brain slices of the primary motor cortex (M1) in untrained and trained rats. Current-clamp analysis showed dynamic changes in resting membrane potential, spike threshold, afterhyperpolarization, and membrane resistance in layer II/III pyramidal neurons. Current injection induced many more spikes in 2-day trained rats than in untrained controls.
To analyze contextual-learning induced plasticity, we trained rats using an inhibitory avoidance (IA) task. After experiencing foot-shock in the dark side of a box, the rats learned to avoid it, staying in the lighted side. We prepared acute hippocampal slices from untrained, IA-trained, unpaired, and walk-through rats. Voltage-clamp analysis was used to sequentially record miniature excitatory and inhibitory postsynaptic currents (mEPSCs and mIPSCs) from the same CA1 neuron. We found different mean mEPSC and mIPSC amplitudes in each CA1 neuron, suggesting that each neuron had different postsynaptic strengths at its excitatory and inhibitory synapses. Moreover, compared with untrained controls, IA-trained rats had higher mEPSC and mIPSC amplitudes, with broad diversity. These results suggested that contextual learning creates postsynaptic diversity in both excitatory and inhibitory synapses at each CA1 neuron.
AMPA or GABAA receptors seemed to mediate the postsynaptic currents, since bath treatment with CNQX or bicuculline blocked the mEPSC or mIPSC events, respectively. This technique can be used to study different types of learning in other regions, such as the sensory cortex and amygdala.

The slice patch clamp technique is an effective method for analyzing learning-induced changes in the intrinsic properties and plasticity of excitatory or inhibitory synapses.

The slice patch clamp technique is a powerful tool for investigating learning-induced neural plasticity in specific brain regions. To analyze ...

Visualization of Cortical Modules in Flattened Mammalian Cortices

The cortex of mammalian brains is parcellated into distinct substructures or modules. Cortical modules typically lie parallel to the cortical sheet, and can be delineated by certain histochemical and immunohistochemical methods. In this study, we highlight a method to isolate the cortex from mammalian brains and flatten them to obtain sections parallel to the cortical sheet. We further highlight selected histochemical and immunohistochemical methods to process these flattened tangential sections to visualize cortical modules. In the somatosensory cortex of various mammals, we perform cytochrome oxidase histochemistry to reveal body maps or cortical modules representing different parts of the body of the animal. In the medial entorhinal cortex, an area where grid cells are generated, we utilize immunohistochemical methods to highlight modules of genetically determined neurons which are arranged in a grid-pattern in the cortical sheet across several species. Overall, we provide a framework to isolate and prepare layer-wise flattened cortical sections, and visualize cortical modules using histochemical and immunohistochemical methods in a wide variety of mammalian brains.

This article describes a detailed methodology to obtain flattened tangential sections from mammalian cortices and visualize cortical modules using histochemical and immunohistochemical methods.

The cortex of mammalian brains is parcellated into distinct substructures or modules. Cortical modules typically lie parallel to the cortical sheet, and ...

Preparation of Acute Spinal Cord Slices for Whole-cell Patch-clamp Recording in Substantia Gelatinosa Neurons

Recent whole-cell patch-clamp studies from substantia gelatinosa (SG) neurons have provided a large body of information about the spinal mechanisms underlying sensory transmission, nociceptive regulation, and chronic pain or itch development. Implementations of electrophysiological recordings together with morphological studies based on the utility of acute spinal cord slices have further improved our understanding of neuronal properties and the composition of local circuitry in SG. Here, we present a detailed and practical guide for the preparation of spinal cord slices and show representative whole-cell recording and morphological results. This protocol permits ideal neuronal preservation and can mimic in vivo conditions to a certain extent. In summary, the ability to obtain an in vitro preparation of spinal cord slices enables stable current- and voltage-clamp recordings and could thus facilitate detailed investigations into the intrinsic membrane properties, local circuitry and neuronal structure using diverse experimental approaches.

Here, we describe the essential steps for whole-cell patch-clamp recordings made from substantia gelatinosa (SG) neurons in the in vitro spinal cord slice. This method allows the intrinsic membrane properties, synaptic transmission and morphological characterization of SG neurons to be studied.

Recent whole-cell patch-clamp studies from substantia gelatinosa (SG) neurons have provided a large body of information about the spinal mechanisms ...

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.

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 ...