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.).

<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. 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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. 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The authors have nothing to disclose.

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>
		</tr>
		<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>
		</tr>
		<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>
		</tr>
		<tr height="24">
			<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>
		</tr>
		<tr height="40">
			<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>
		</tr>
		<tr height="29">
			<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>
			<td style="width:288px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Mater-9 Pulse Generator</td>
			<td style="width:183px;">AMPI</td>
			<td style="width:119px;"></td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Iso-flex Stimulus Isolator</td>
			<td style="width:183px;">AMPI</td>
			<td style="width:119px;"></td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">pCLAMP 10 Data Acquisition and Analysis Software</td>
			<td style="width:183px;">Molecular Devices</td>
			<td style="width:119px;">1-2500-0180</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Concentric Bipolar Electrode</td>
			<td style="width:183px;">FHC</td>
			<td style="width:119px;">CBDSH75</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ball-joint Manipulator</td>
			<td style="width:183px;">Narishige&#160;</td>
			<td style="width:119px;"></td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="52">
			<td height="52" style="height:52px;width:216px;">Non-metalic Syringes 34 Gauge</td>
			<td style="width:183px;">World Precision Instruments</td>
			<td style="width:119px;">MF34G-5</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Nikon Stereomicroscope</td>
			<td style="width:183px;">Nikon</td>
			<td style="width:119px;">SMZ800N</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">No. 5 Forceps</td>
			<td style="width:183px;">Fine Science Tools</td>
			<td style="width:119px;"></td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:216px;">Spring Scissors</td>
			<td style="width:183px;">Fine Science Tools</td>
			<td style="width:119px;">15006-09</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="21">
			<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>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Microdissecting Scissors</td>
			<td style="width:183px;">Roboz</td>
			<td style="width:119px;">RS-5912SC</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sylgard 184 Silicone Elastomer Kit</td>
			<td style="width:183px;">Dow Corning</td>
			<td align="right" style="width:119px;">2404019862</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Hair Removal Cream</td>
			<td style="width:183px;">Nair</td>
			<td style="width:119px;"></td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:216px;">Grass SD9 Stimulator</td>
			<td style="width:183px;">Grass Medical</td>
			<td style="width:119px;"></td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="46">
			<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>
			<td style="width:288px;"></td>
		</tr>
		<tr height="37">
			<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>
		</tr>
		<tr height="44">
			<td height="44" style="height:44px;width:216px;">Low Pass Bessell Filter</td>
			<td style="width:183px;">Warner Instrument Corp.</td>
			<td style="width:119px;">LPF-8</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="44">
			<td height="44" style="height:44px;width:216px;">Left-handed Micromanipulator</td>
			<td style="width:183px;">Siskiyou Corp.</td>
			<td style="width:119px;">MX1641/45DL</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="44">
			<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>
		</tr>
		<tr height="44">
			<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>
		</tr>
		<tr height="161">
			<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>
		</tr>
		<tr height="21">
			<td colspan="3" height="21" style="height:21px;width:517px;">All chemicals were orded from Fisher except,</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">BTS</td>
			<td style="width:183px;">Toronto Research Chemicals</td>
			<td style="width:119px;">B315190</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">CTX</td>
			<td style="width:183px;">Alomone Labs</td>
			<td style="width:119px;">C-270</td>
			<td style="width:288px;"></td>
		</tr>
		<tr height="42">
			<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>
			<td style="width:288px;">Molecular probes is no longer a company. Now ordered through Fisher</td>
		</tr>
	</tbody>
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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</...

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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 ...

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9.3K Views.  Wright State University. 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.

Video: Levator Auris Longus Preparation for Examination of Mammalian Neuromuscular Transmission Under Voltage Clamp Conditions

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, ...

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 ...

Millisecond Hydrogen/Deuterium-Exchange Mass Spectrometry for the Study of Alpha-Synuclein Structural Dynamics Under Physiological Conditions

Alpha-synuclein (aSyn) is an intrinsically disordered protein whose fibrillar aggregates are abundant in Lewy bodies and neurites, which are the hallmarks of Parkinson's disease. Yet, much of its biological activity, as well as its aggregation, centrally involves the soluble monomer form of the protein. Elucidation of the molecular mechanisms of aSyn biology and pathophysiology requires structurally highly resolved methods and is sensitive to biological conditions. Its natively unfolded, meta-stable structures make monomeric aSyn intractable to many structural biology techniques. Here, the application of one such approach is described: hydrogen/deuterium-exchange mass spectrometry (HDX-MS) on the millisecond timescale for the study of proteins with low thermodynamic stability and weak protection factors, such as aSyn. At the millisecond timescale, HDX-MS data contain information on the solvent accessibility and hydrogen-bonded structure of aSyn, which are lost at longer labeling times, ultimately yielding structural resolution up to the amino acid level. Therefore, HDX-MS can provide information at high structural and temporal resolutions on conformational dynamics and thermodynamics, intra- and inter-molecular interactions, and the structural impact of mutations or alterations to environmental conditions. While broadly applicable, it is demonstrated how to acquire, analyze, and interpret millisecond HDX-MS measurements in monomeric aSyn.

The structural ensemble of monomeric alpha-synuclein affects its physiological function and physicochemical properties. The present protocol describes how to perform millisecond hydrogen/deuterium-exchange mass spectrometry and subsequent data analyses to determine conformational information on the monomer of this intrinsically disordered protein under physiological conditions.

Alpha-synuclein (aSyn) is an intrinsically disordered protein whose fibrillar aggregates are abundant in Lewy bodies and neurites, which are the hallmarks ...