This work was supported in part by grants from the Intramural support research program (IRSP) from UMMC, AHA Scientist Development Grant (13SDG14000006) awarded to Mallikarjuna R. Pabbidi.

The male rats were housed in the Animal Care Facility at UMMC, which is approved by the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC). Animals had free access to food and water throughout the study. Animals were maintained in a controlled environment with temperature at 24 &#177; 2 &#176;C, humidity levels of 60&#8211;80% and 12 h light/dark cycles. All protocols were approved by the Animal Care and Use Committee of UMMC.
1. Preparation of Equipment
<ol>
	<li>Place a dual channel differential electrometer amplifier (see the Table of Materials) close to the vessel chamber and at the desired location.</li>
	<li>Connect the output of the amplifier channel A or B to the channel input of the digitizer with a BNC-BNC cable.</li>
	<li>Mount the probe in the micromanipulator and place it near the microscope and the myograph. The recording setup must be installed on a vibration-free table.</li>
	<li>Place the knobs and switches on the front of the amplifier in positions that configure it for this experiment as described in the manual.</li>
	<li>Connect the bath ground to the circuit ground of the amplifier via with an appropriate electrode. Similarly, ensure that the cage is grounded to the chassis of the amplifier.</li>
</ol>
2. Preparation of Microelectrodes and Assembly
<ol>
	<li>Use borosilicate glass microelectrodes (see the Table of Materials) and pull the glass tip to have a 8&#8211;10 mm taper, diameter of &#60;1 &#181;m and resistance of 80&#8211;120 M&#8486; when filled with 3 M KCl.
	<ol>
		<li>Use a standard puller to achieve a short gradual taper using the following settings: heat = 650; velocity = 20; pull = 25; time = 250 and loop twice for higher resistances and smaller tips. See the Table of Materials as the settings are instrument-specific. 
		NOTE: Tip diameters &#60;1 &#181;m will cause minimal damage to the cell when impaled.</li>
	</ol>
	</li>
	<li>Fill the microelectrode with 3 M KCl using a microfiber syringe (see the Table of Materials).
	<ol>
		<li>Slowly pull the plunger of the microfiber syringe up while injecting the 3 M KCl into the microelectrode to allow space for the fluid to fill and to prevent the formation of air bubbles inside the microelectrode.</li>
		<li>Fill the microelectrode until full and ensure that there are no air bubbles before placing it in the microelectrode holder. If bubbles are present, gently tap the microelectrode with a finger to remove the bubbles.</li>
	</ol>
	</li>
	<li>Exercising care, firmly push the electrode shank into the holder through the bored hole. If excess fluid is present, remove it with a tissue.</li>
	<li>Connect the electrode holder assembly to the amplifier probe. Conduct an electrode test, adjust the input offset, verify zero setting and check the probe input leakage as per the amplifier manual.</li>
	<li>Measure electrode resistance using an electrode test as shown in Table 1.</li>
	<li>Note that a working electrode displays a positive DC voltage shift of 1 mV/M&#937; at the channel output. On the other hand, if a large voltage appears at the channel output and on the meter, this indicates a blocked or broken electrode.</li>
	<li>Open the recording software, assign a name to the file and save it for future analysis in a storing software.</li>
</ol>
3. Isolation and Cannulation of the Middle Cerebral Artery
<ol>
	<li>Preparation the reagents.
	<ol>
		<li>Prepare normal and low calcium physiological salt solution (PSS) as described in Table 2.</li>
	</ol>
	</li>
	<li>Prepare the myograph.
	<ol>
		<li>Rinse the myograph chamber (see the Table of Materials) with distilled water multiple times to keep it free of debris. Load the chamber with 5 mL of normal PSS.</li>
		<li>Fill both glass cannulas with filtered normal PSS using a 5&#8211;10 mL syringe. Carefully fill the entire cannula and the attached tubing without introducing any air bubbles.</li>
		<li>Prepare two monofilament nylon sutures (10-0, 0.02 mm) with a half-knot each using blunt forceps.</li>
		<li>Place the partially closed suture knots on both cannulas slightly away from the tip using dissection forceps under a dissection microscope. Later these knots will be slid off and tied carefully onto the cannulated arterial ends to secure the vessel.</li>
	</ol>
	</li>
	<li>Isolate and cannulate the middle cerebral artery.
	<ol>
		<li>Induce deep anesthesia in a Sprague Dawley rat by using 2&#8211;4% inhaled isoflurane.</li>
		<li>Decapitate the rat using guillotine under deep anesthesia.</li>
		<li>Carefully remove the skull using a bone cutter and a scissor.</li>
		<li>Remove the brain from the skull and place it in 5 mL of low calcium PSS on ice.</li>
		<li>Identify and dissect out an unbranched segment of rat middle cerebral artery (MCA) with an inner diameter of 100&#8211;200 &#956;m from the brain using spring scissors and forceps.</li>
		<li>Mount the MCA onto the glass cannulas using fine forceps and secure by tightening the sutures in the myograph containing normal PSS.</li>
		<li>Close off the distal cannula so that there will be no flow within the MCAs.</li>
		<li>Connect the inflow pipette to a reservoir holding PSS to allow for control of intraluminal pressure which will be monitored with an in-line pressure transducer.</li>
		<li>Visualize the cannulated MCAs using a charge-coupled device camera (see the Table of Materials) mounted on an inverted microscope and an imaging software.</li>
		<li>Set the axial length of the MCA to an approximate length where it should appear neither rigid nor flaccid.</li>
		<li>Equilibrate the bath solution with O2 (95%) and CO2 (5%) at 37 &#176;C to provide adequate oxygenation, temperature and to maintain pH at 7.4.</li>
	</ol>
	</li>
	<li>Impale (penetrate the cell plasma membrane) the vascular smooth muscle cells.
	<ol>
		<li>Connect the ground electrode and keep it immersed in the PSS of the myograph.</li>
		<li>Illuminate the vessel chamber and look through the microscope to visualize the tip of the microelectrode in the bath solution. 
		NOTE: Alternatively, one can visualize the MCA and microelectrode on a computer having an imaging software.</li>
		<li>Use the controls of the micromanipulator to move the tip of the microelectrode close to the outer wall of the blood vessel. The micromanipulator and the tip of the microelectrode must be in a stable position in relation to the tissue. 
		NOTE: Before beginning experiments, confirm that the membrane voltage has stabilized. If the measured voltage is unstable, the connection between the electrode and the cell is not sealed, indicating a leak.</li>
		<li>Begin the recording.</li>
		<li>Slowly move the tip of the microelectrode towards the vessel, aiming for the center of the vessel using course or fine control of the micromanipulator. 
		NOTE: Occasionally, a small deflection in the recording may be observed when the microelectrode tip contacts a muscle fiber membrane.</li>
		<li>When the tip comes in close proximity to the vessel, advance the electrode forward in one rapid motion using the micromanipulator to impale the membrane of the muscle.</li>
		<li>At this point, one can begin observing the changes in Vm being recorded. Do not touch the micromanipulator when the microelectrode impales the membrane of the cell. 
		NOTE: The difference in voltage between the recording and reference electrode decreases from 0 mV to between -40 mV and -75 mV depending on the level of intravascular pressure or other excitatory or inhibitory stimuli. These readings characterize the transmembrane potential difference of the current cell.</li>
		<li>Perform multiple impalements on a single vessel in different areas of the vessel without damaging VSMCs in order to get accurate measurements.</li>
		<li>After recording, use the manipulator to remove the microelectrode in one rapid movement.</li>
		<li>Stop the recording and save data files for further analysis.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Nelson, M. T., Quayle, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiological+roles+and+properties+of+potassium+channels+in+arterial+smooth+muscle.">Physiological roles and properties of potassium channels in arterial smooth muscle.</a> American Journal of Physiology. 268, C799-C822 (1995).</li><li>Hughes, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+channels+in+vascular+smooth+muscle+cells.">Calcium channels in vascular smooth muscle cells.</a> Journal of Vascular Research. 32 (6), 353-370 (1995).</li><li>Large, W. A., Wang, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+and+physiological+role+of+the+Ca(2+)-activated+Cl-+conductance+in+smooth+muscle.">Characteristics and physiological role of the Ca(2+)-activated Cl- conductance in smooth muscle.</a> American Journal of Physiology. 271 (2 Pt 1), C435-C454 (1996).</li><li>Nelson, M. T., Conway, M. A., Knot, H. J., Brayden, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chloride+channel+blockers+inhibit+myogenic+tone+in+rat+cerebral+arteries.">Chloride channel blockers inhibit myogenic tone in rat cerebral arteries.</a> Journal of Physiology. 502 (Pt 2), 259-264 (1997).</li><li>Yamazaki, J., 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=Functional+and+molecular+expression+of+volume-regulated+chloride+channels+in+canine+vascular+smooth+muscle+cells.">Functional and molecular expression of volume-regulated chloride channels in canine vascular smooth muscle cells.</a> Journal of Physiology. 507 (Pt 3), 729-736 (1998).</li><li>Gibson, A., McFadzean, I., Wallace, P., Wayman, C. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Capacitative+Ca2++entry+and+the+regulation+of+smooth+muscle+tone.">Capacitative Ca2+ entry and the regulation of smooth muscle tone.</a> Trends in Pharmacol Sciences. 19 (7), 266-269 (1998).</li><li>Davis, M. J., Donovitz, J. A., Hood, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stretch-activated+single-channel+and+whole+cell+currents+in+vascular+smooth+muscle+cells.">Stretch-activated single-channel and whole cell currents in vascular smooth muscle cells.</a> American Journal of Physiology. 262 (4 Pt 1), C1083-C1088 (1992).</li><li>Setoguchi, M., Ohya, Y., Abe, I., Fujishima, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stretch-activated+whole-cell+currents+in+smooth+muscle+cells+from+mesenteric+resistance+artery+of+guinea-pig.">Stretch-activated whole-cell currents in smooth muscle cells from mesenteric resistance artery of guinea-pig.</a> Journal of Physiology. 501 (Pt 2), 343-353 (1997).</li><li>Shelly, D. 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=Na(+)+pump+alpha+2-isoform+specifically+couples+to+contractility+in+vascular+smooth+muscle:+evidence+from+gene-targeted+neonatal+mice.">Na(+) pump alpha 2-isoform specifically couples to contractility in vascular smooth muscle: evidence from gene-targeted neonatal mice.</a> American Journal of Physiology-Cell Physiology. 286 (4), C813-C820 (2004).</li><li>Coca, A., Garay, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Ionic Transport in Hypertension New Perspectives. , (1993).</li><li>Harder, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pressure-dependent+membrane+depolarization+in+cat+middle+cerebral+artery.">Pressure-dependent membrane depolarization in cat middle cerebral artery.</a> Circulation Research. 55 (2), 197-202 (1984).</li><li>Knot, H. J., Nelson, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+arterial+diameter+and+wall+[Ca2+]+in+cerebral+arteries+of+rat+by+membrane+potential+and+intravascular+pressure.">Regulation of arterial diameter and wall [Ca2+] in cerebral arteries of rat by membrane potential and intravascular pressure.</a> Journal of Physiology. 508 (Pt 1), 199-209 (1998).</li><li>Nelson, M. T., Patlak, J. B., Worley, J. F., Standen, N. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+channels,+potassium+channels,+and+voltage+dependence+of+arterial+smooth+muscle+tone.">Calcium channels, potassium channels, and voltage dependence of arterial smooth muscle tone.</a> American Journal of Physiology. 259, C3-C18 (1990).</li><li>Harder, D. R., Sperelakis, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Action+potentials+induced+in+guinea+pig+arterial+smooth+muscle+by+tetraethylammonium.">Action potentials induced in guinea pig arterial smooth muscle by tetraethylammonium.</a> American Journal of Physiology. 237 (1), C75-C80 (1979).</li><li>Nystoriak, M. 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=Fundamental+increase+in+pressure-dependent+constriction+of+brain+parenchymal+arterioles+from+subarachnoid+hemorrhage+model+rats+due+to+membrane+depolarization.">Fundamental increase in pressure-dependent constriction of brain parenchymal arterioles from subarachnoid hemorrhage model rats due to membrane depolarization.</a> American Journal of Physiology-Heart and Circulatory Physiology. 300 (3), H803-H812 (2011).</li><li>Yvonder Weid, P., Lee, S., Imtiaz, M. S., Zawieja, D. C., Davis, M. 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The authors have nothing to disclose.

This article provides the necessary steps on how to use a sharp microelectrode impalement method to record Vm from a cannulated vessel preparation. This method is widely used, and offers high-quality, consistent recordings of Vm that answer a wide range of experimental questions.
Some critical considerations and troubleshooting steps are described here to ensure success of the method. The quality of the microelectrode (its sharpness and resistance) and the cellular proces...

The membrane potential (Vm) of a cell refers to the relative difference of ionic charge across the plasma membrane and the relative permeability of the membrane to these ions. The Vm is generated by the differential distribution of ions and is maintained by ion channels and pumps. Ion channels such as K+, Na+, and Cl&#8722; contribute substantially to the resting Vm. Vascular smooth muscle cells (VSMCs) express more than four different types of K+ channels1, two types of voltage-gated Ca2+ channels (VGCC)2, more than two types of Cl&#8722; channels3,4,5, store-operated Ca2+ channels6, stretch-activated cation channels7,8, and electrogenic sodium-potassium ATPase pumps9 in their plasma membranes, all of which may be involved in the regulation of Vm.
The Vm of VSMCs depends on lumen pressure. In non-pressurized vessels, Vm varies from -50 to -65 mV, however, in pressurized arterial segments, Vm ranges from -37 to -47 mV10. Elevation of intravascular pressure causes VSMCs to depolarize11, decreases the threshold for VGCC opening, and increases calcium influx contributing to the development of myogenic tone12. On the contrary, in passive or non-pressurized vessels, membrane hyperpolarization, due to high K+ channel activity, will prevent VGCC from opening, resulting in limited calcium entry and a decrease in intracellular calcium, contributing to less vascular tone13. Thus, Vm due to changes in lumen pressure appears to play an essential role in vascular tone development, and both VGCC and K+ channels play a crucial role in the regulation of Vm.
Vm varies between vessel type and species. Vm is -54 &#177; 1.3 mV in guinea pig superior mesenteric arterial strips14, -45 &#177; 1 mV in the rat middle cerebral arteries at 60 mmHg lumen pressure12, and -35 &#177; 1 mV in rat parenchymal arteries at 40 mmHg lumen pressure15. The resting Vm recorded in unstretched rat lymphatic muscle is -48 &#177; 2 mV16. Vm of cerebral VSMCs is more negative than in peripheral arteries. In comparison, feline middle cerebral arteries were reported to have a Vm of approximately -70 mV, while mesenteric and coronary arteries were reported to have -49 and -58 mV, respectively17,18. Differences in the Vm across vascular beds may reflect the differences in the expression and function of ion channels and electrogenic sodium-potassium pumps.
Increases and decreases in Vm are referred to as membrane depolarization and hyperpolarization, respectively. These alterations in Vm play a central role in many physiological processes, including ion-channel gating, cell signaling, muscle contraction, and action potential propagation. At a fixed pressure, many endogenous and synthetic vasodilator compounds that activate K+ channels cause membrane hyperpolarization, resulting in vasodilation1,13. Conversely, sustained membrane depolarization is vital in agonist-induced or receptor-mediated vasoconstriction19. Vm is a critical variable that not only regulates Ca2+ influx through VGCC13 but also influences the release of Ca2+ from internal stores20,21 and Ca2+-sensitivity of the contractile apparatus22.
While there are several methods to record Vm from different cell types, data collected from the microelectrode impalement method of cannulated vessels appears to be more physiological than data obtained from isolated VSMCs. When recorded from isolated VSMC using current clamp methods, Vm is seen as spontaneous transient hyperpolarizations in VSMCs24. Isolated VSMCs are not in the syncytium, and the changes in the series resistance may contribute to the oscillatory behavior of Vm. On the other hand, oscillatory behavior is not observed when Vm is recorded from intact vessels, probably due to cell-cell contact between VSMCs that are in syncytium in the artery and are summated throughout the vessel leading to a stable Vm24. Thus, measurement of Vm from pressurized vessels using standard microelectrode impalement technique is relatively close to the physiological conditions.
Recording Vm from cannulated vessels could provide vital information, since Vm of VSMCs that are in syncytium is one of the major determinants of vascular tone and blood flow, and modulation of the Vm could provide a way to dilate or constrict blood vessels. Thus, it is essential to understand the methodology involved in recording Vm. This article describes intracellular recording of Vm from cannulated middle cerebral arteries (MCAs) using a microelectrode impalement method. This protocol will describe how to prepare MCAs, microelectrodes, set up the electrometer and perform the impalement method to record Vm. Also, representative data, common issues that were encountered when using this method and potential issues are discussed.

<table>
	<tbody>
		<tr>
			<td>Dissection instruments</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Aneshetic Vaporiser</td>
			<td>Parkland scientific</td>
			<td>V3000PK</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissection microscope</td>
			<td>Nikon Instruments Inc., NY</td>
			<td>Eclipse Ti-S</td>
			<td></td>
		</tr>
		<tr>
			<td>Kleine Guillotine Type 7575</td>
			<td>Harvard Apparatus, MA</td>
			<td>73-198</td>
			<td></td>
		</tr>
		<tr>
			<td>Littauer Bone Cutter</td>
			<td>Fine science tools</td>
			<td>16152-15</td>
			<td></td>
		</tr>
		<tr>
			<td>Moria MC40 Ultra Fine Forceps</td>
			<td>Fine science tools</td>
			<td>11370-40</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical scissors Sharp-Blunt</td>
			<td>Fine science tools</td>
			<td>14008-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Suture</td>
			<td>Harvard Apparatus</td>
			<td>72-3287</td>
			<td></td>
		</tr>
		<tr>
			<td>Vannas Spring Scissors</td>
			<td>Fine science tools</td>
			<td>15018-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Electrophysiology Instruments</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Charge-coupled device camera</td>
			<td>Qimaging, , BC</td>
			<td>Retiga 2000R</td>
			<td></td>
		</tr>
		<tr>
			<td>Differential electrometer amplifier</td>
			<td>WPI</td>
			<td>FD223A</td>
			<td></td>
		</tr>
		<tr>
			<td>In-line pressure transducer</td>
			<td>Harvard Apparatus, MA</td>
			<td>MA1 72-4496</td>
			<td></td>
		</tr>
		<tr>
			<td>Micromanipulator</td>
			<td>Thor labs</td>
			<td>PCS-5400</td>
			<td></td>
		</tr>
		<tr>
			<td>Microelectrodes</td>
			<td>Warner Instruments LLC, CT</td>
			<td>G200-6,</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro Fil (Microfiber syringe)</td>
			<td>WPI</td>
			<td>MF28G67-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Microelectrode holder</td>
			<td>WPI</td>
			<td>MEH1SF</td>
			<td></td>
		</tr>
		<tr>
			<td>Myograph</td>
			<td>Living Systems Instrumentation, VT</td>
			<td>CH-1-SH</td>
			<td></td>
		</tr>
		<tr>
			<td>Puller</td>
			<td>Sutter Instrument, San Rafael, CA</td>
			<td>P-97</td>
			<td></td>
		</tr>
		<tr>
			<td>Vibration-free table</td>
			<td>TMC</td>
			<td>3435-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Softwares</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Clampex 10</td>
			<td>Molecular devices</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>p Clamp 10</td>
			<td>Molecular devices</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Imaging software</td>
			<td>Nikon, NY</td>
			<td>NIS-elements</td>
			<td></td>
		</tr>
		<tr>
			<td>Chemicals</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma</td>
			<td>S7653</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma</td>
			<td>P4504</td>
			<td></td>
		</tr>
		<tr>
			<td>MgSO4</td>
			<td>Sigma</td>
			<td>M7506</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2 </td>
			<td>Sigma</td>
			<td>C3881</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma</td>
			<td>H7006</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma</td>
			<td>G7021</td>
			<td></td>
		</tr>
		<tr>
			<td>NaH2PO4</td>
			<td>Sigma</td>
			<td>S0751</td>
			<td></td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>Sigma</td>
			<td>S5761</td>
			<td></td>
		</tr>
	</tbody>
</table>

microelectrode impalement method to record membrane potential from a cannulated middle cerebral artery

Membrane potential (Vm) of vascular smooth muscle cells determines vessel tone and thus blood flow to an organ. Changes in the expression and function of ion channels and electrogenic pumps that regulate Vm in disease conditions could potentially alter Vm, vascular tone, and blood flow. Thus, a basic understanding of electrophysiology and the methods necessary to accurately record Vm in healthy and diseased states are essential. This method will allow modulating Vm using different pharmacological agents to restore Vm. Although there are several methods, each with its advantages and disadvantages, this article provides protocols to record Vm from cannulated resistance vessels such as the middle cerebral artery using the microelectrode impalement method. Middle cerebral arteries are allowed to gain myogenic tone in a myograph chamber, and the vessel wall is impaled using high resistance microelectrodes. The Vm signal is collected through an electrometer, digitized, and analyzed. This method provides an accurate reading of the Vm of a vessel wall without damaging the cells and without changing the membrane resistance.

The presented method can be reliably used to record Vm in cannulated vessels. A brief procedure describing how to isolate MCA from the brain is presented in Figure 1A. After separating the brain from the skull, the MCA was dissected out and placed in a Petri dish containing low calcium PSS. Part of the connective tissue that was attached was also dissected along with MCA using spring scissors and forceps to prevent damage to MCA during the isolatio...

Watch this Scientific Journal Video about Microelectrode Impalement Method to Record Membrane Potential from a Cannulated Middle Cerebral Artery at JoVE.com

Microelectrode Impalement Method to Record Membrane Potential from a Cannulated Middle Cerebral Artery

The primary goal of this article is to provide details of how to record membrane potential (Vm) from the middle cerebral artery using the microelectrode impalement method. The cannulated middle cerebral artery is equilibrated to gain myogenic tone, and the vessel wall is impaled using high resistance microelectrodes.

Membrane potential (Vm) of vascular smooth muscle cells determines vessel tone and thus blood flow to an organ. Changes in the expression and function of ...

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JoVE Journal

Medicine

6.7K Views.  University of Mississippi Medical Center. The primary goal of this article is to provide details of how to record membrane potential (Vm) from the middle cerebral artery using the microelectrode impalement method. The cannulated middle cerebral artery is equilibrated to gain myogenic tone, and the vessel wall is impaled using high resistance microelectrodes.

Video: Microelectrode Impalement Method to Record Membrane Potential from a Cannulated Middle Cerebral Artery

Modeling Stroke in Mice - Middle Cerebral Artery Occlusion with the Filament Model

Stroke is among the most frequent causes of death and adult disability, especially in highly developed countries. However, treatment options to date are very limited. To meet the need for novel therapeutic approaches, experimental stroke research frequently employs rodent models of focal cerebral ischaemia. Most researchers use permanent or transient occlusion of the middle cerebral artery (MCA) in mice or rats.
Proximal occlusion of the middle cerebral artery (MCA) via the intraluminal suture technique (so called filament or suture model) is probably the most frequently used model in experimental stroke research. The intraluminal MCAO model offers the advantage of inducing reproducible transient or permanent ischaemia of the MCA territory in a relatively non-invasive manner. Intraluminal approaches interrupt the blood flow of the entire territory of this artery. Filament occlusion thus arrests flow proximal to the lenticulo-striate arteries, which supply the basal ganglia. Filament occlusion of the MCA results in reproducible lesions in the cortex and striatum and can be either permanent or transient. In contrast, models inducing distal (to the branching of the lenticulo-striate arteries) MCA occlusion typically spare the striatum and primarily involve the neocortex. In addition these models do require craniectomy. In the model demonstrated in this article, a silicon coated filament is introduced into the common carotid artery and advanced along the internal carotid artery into the Circle of Willis, where it blocks the origin of the middle cerebral artery. In patients, occlusions of the middle cerebral artery are among the most common causes of ischaemic stroke. Since varying ischemic intervals can be chosen freely in this model depending on the time point of reperfusion, ischaemic lesions with varying degrees of severity can be produced. Reperfusion by removal of the occluding filament at least partially models the restoration of blood flow after spontaneous or therapeutic (tPA) lysis of a thromboembolic clot in humans.
In this video we will present the basic technique as well as the major pitfalls and confounders which may limit the predictive value of this model.

Filamentous occlusion of the Middle cerebral artery is a common model for studying ischemic stroke in mice.

Stroke is among the most frequent causes of death and adult disability, especially in highly developed countries. However, treatment options to date are ...

Mouse Model of Middle Cerebral Artery Occlusion

Stroke is the most common fatal neurological disease in the United States 1. The majority of strokes (88%) result from blockage of blood vessels in the brain (ischemic stroke) 2. Since most ischemic strokes (~80%) occur in the territory of middle cerebral artery (MCA) 3, many animal stroke models that have been developed have focused on this artery. The intraluminal monofilament model of middle cerebral artery occlusion (MCAO) involves the insertion of a surgical filament into the external carotid artery and threading it forward into the internal carotid artery (ICA) until the tip occludes the origin of the MCA, resulting in a cessation of blood flow and subsequent brain infarction in the MCA territory 4. The technique can be used to model permanent or transient occlusion 5. If the suture is removed after a certain interval (30 min, 1 h, or 2 h), reperfusion is achieved (transient MCAO); if the filament is left in place (24 h) the procedure is suitable as a model of permanent MCAO. This technique does not require craniectomy, a neurosurgical procedure to remove a portion of skull, which may affect intracranial pressure and temperature 6. It has become the most frequently used method to mimic permanent and transient focal cerebral ischemia in rats and mice 7,8. To evaluate the extent of cerebral infarction, we stain brain slices with 2,3,5-triphenyltetrazolium chloride (TTC) to identify ischemic brain tissue 9. In this video, we demonstrate the MCAO method and the determination of infarct size by TTC staining.

We demonstrate in the video a method for producing a middle cerebral artery occlusion in adult mice using an intraluminal monofilament. We also show how to evaluate the extent of cerebral infarction by 2,3,5-triphenyltetrazolium chloride (TTC) staining.

Stroke is the most common fatal neurological disease in the United States 1. The majority of strokes (88%) result from blockage of blood vessels in the ...

Intraluminal Middle Cerebral Artery Occlusion (MCAO) Model for Ischemic Stroke with Laser Doppler Flowmetry Guidance in Mice

Stroke is the third leading cause of death and the leading cause of disability in the world, with an estimated cost of near $70 billion 
in the United States in 20091,2. The intraluminal middle cerebral artery occlusion (MCAO) model was developed by Koizumi4 in 1986 to simulate this 
impactful human pathology in the rat. A modification of the MCAO method was later presented by Longa3. Both techniques have been widely used to identify 
molecular mechanisms of brain injury resulting from ischemic stroke and potential therapeutic modalities5. This relatively noninvasive method in rats has been 
extended to use in mice to take advantage of transgenic and knockout strains6,7. To model focal cerebral ischemia, an intraluminal suture is advanced via 
the internal carotid artery to occlude the base of the MCA. Retracting the suture after a specified period of time mimics spontaneous reperfusion, but the 
suture can also be permanently retained. This video will be demonstrating the two major approaches for performing intraluminal MCAO procedure in mice in a 
stepwise fashion, as well as providing insights for potential drawbacks and pitfalls. The ischemic brain tissue will subsequently be stained by 
2,3,5-triphenyltetrazolium chloride (TTC) to evaluate the extent of cerebral infarction8.

Intraluminal Middle Cerebral Artery Occlusion MCAO Model for Ischemic Stroke with Laser Doppler Flowmetry Guidance in Mice

The intraluminal middle cerebral artery occlusion (MCAO) model is the most frequent used model among experimental ischemic stroke models. Here we will demonstrate the entire model in detail with the guide of Laser Doppler flowmetry, and its representative results.

Stroke is the third leading cause of death and the leading cause of disability in the world, with an estimated cost of near $70 billion 
in the United ...

The Application Of Permanent Middle Cerebral Artery Ligation in the Mouse

Focal cerebral ischemia is among the most common type of stroke seen in patients. Due to the clinical significance there has been a prolonged effort to develop suitable animal models to study the events that unfold during ischemic insult. These techniques include transient or permanent, focal or global ischemia models using many different animal models, with the most common being rodents.
The permanent MCA ligation method which is also referred as pMCAo in the literature is used extensively as a focal ischemia model in rodents 1-6. This method was originally described for rats by Tamura et al. in 1981 7. In this protocol a craniotomy was used to access the MCA and the proximal regions were occluded by electrocoagulation. The infarcts involve mostly cortical and sometimes striatal regions depending on the location of the occlusion. This technique is now well established and used in many laboratories 8-13. Early use of this technique led to the definition and description of &#x201C;infarct core&#x201D; and &#x201C;penumbra&#x201D; 14-16, and it is often used to evaluate potential neuroprotective compounds 10, 12, 13, 17. Although the initial studies were performed in rats, permanent MCA ligation has been used successfully in mice with slight modifications 18-20 .
This model yields reproducible infarcts and increased post-survival rates. Approximately 80% of the ischemic strokes in humans happen in the MCA area 21 and thus this is a very relevant model for stroke studies. Currently, there is a paucity of effective treatments available to stroke patients, and thus there is a need for good models to test potential pharmacological compounds and evaluate physiological outcomes. This method can also be used for studying intracellular hypoxia response mechanisms in vivo. 
Here, we present the MCA ligation surgery in a C57/BL6 mouse. We describe the pre-surgical preparation, MCA ligation surgery and 2,3,5 Triphenyltetrazolium chloride (TTC) staining for quantification of infarct volumes.

Middle cerebral artery (MCA) ligation is a technique to study focal cerebral ischemia in animal models. In this method, the middle cerebral artery is exposed by craniotomy and ligated by cauterization. This method gives highly reproducible infarct volumes and increased post-operative survival rates compared to other methods available.

Focal cerebral ischemia is among the most common type of stroke seen in patients. Due to the clinical significance there has been a prolonged effort to ...

Utilizing a Cranial Window to Visualize the Middle Cerebral Artery During Endothelin-1 Induced Middle Cerebral Artery Occlusion

Creation of a cranial window is a method that allows direct visualization of structures on the cortical surface of the brain1-3. This technique can be performed in many locations overlying the rat cerebrum, but is most easily carried out by creating a craniectomy over the readily accessible frontal or parietal bones. Most frequently, we have used this technique in combination with the endothelin-1 middle cerebral artery occlusion model of ischemic stroke to quantify the changes in middle cerebral artery vessel diameter that occur with injection of endothelin-1 into the brain parenchyma adjacent to the proximal MCA4, 5. In order to visualize the proximal portion of the MCA during endothelin -1 induced MCAO, we use a technique to create a cranial window through the temporal bone on the lateral aspect of the rat skull (Figure 1). Cerebral arteries can be visualized either with the dura intact or with the dura incised and retracted. Most commonly, we leave the dura intact during visualization since endothelin-1 induced MCAO involves delivery of the vasoconstricting peptide into the brain parenchyma. This bypasses the need to incise the dura directly over the visualized vessels for drug delivery. This protocol will describe how to create a cranial window to visualize cerebral arteries in a step-wise fashion, as well as how to avoid many of the potential pitfalls pertaining to this method.

This article describes a method for visualizing rat cerebral arteries through a cranial window using temporal craniectomy in order to view proximal portions of the middle cerebral artery (Figure 1). This versatile method can be combined with various techniques of drug delivery to measure cerebral artery reactivity in vivo.

Creation of a cranial window is a method that allows direct visualization of structures on the cortical surface of the brain1-3. This technique can be ...

Optimized System for Cerebral Perfusion Monitoring in the Rat Stroke Model of Intraluminal Middle Cerebral Artery Occlusion

The translational potential of pre-clinical stroke research depends on the accuracy of experimental modeling. Cerebral perfusion monitoring in animal models of acute ischemic stroke allows to confirm successful arterial occlusion and exclude subarachnoid hemorrhage. Cerebral perfusion monitoring can also be used to study intracranial collateral circulation, which is emerging as a powerful determinant of stroke outcome and a possible therapeutic target. Despite a recognized role of Laser Doppler perfusion monitoring as part of the current guidelines for experimental cerebral ischemia, a number of technical difficulties exist that limit its widespread use. One of the major issues is obtaining a secure and prolonged attachment of a deep-penetration Laser Doppler probe to the animal skull. In this video, we show our optimized system for cerebral perfusion monitoring during transient middle cerebral artery occlusion by intraluminal filament in the rat. We developed in-house a simple method to obtain a custom made holder for twin-fibre (deep-penetration) Laser Doppler probes, which allow multi-site monitoring if needed. A continuous and prolonged monitoring of cerebral perfusion could easily be obtained over the intact skull.

Cerebral perfusion monitoring has been demonstrated to improve accuracy in ischemic stroke models. Technical difficulties often limit the use of this essential tool for cerebrovascular research. In this video, an optimized system is shown to obtain a single or multi-site hemodynamic monitoring during intraluminal middle cerebral artery occlusion in rats.

The translational potential of pre-clinical stroke research depends on the accuracy of experimental modeling. Cerebral perfusion monitoring in animal ...

Modeling Stroke in Mice: Permanent Coagulation of the Distal Middle Cerebral Artery

Stroke is the third most common cause of death and a main cause of acquired adult disability in developed countries. Only very limited therapeutical options are available for a small proportion of stroke patients in the acute phase. Current research is intensively searching for novel therapeutic strategies and is increasingly focusing on the sub-acute and chronic phase after stroke because more patients might be eligible for therapeutic interventions in a prolonged time window. These delayed mechanisms include important pathophysiological pathways such as post-stroke inflammation, angiogenesis, neuronal plasticity and regeneration. In order to analyze these mechanisms and to subsequently evaluate novel drug targets, experimental stroke models with clinical relevance, low mortality and high reproducibility are sought after. Moreover, mice are the smallest mammals in which a focal stroke lesion can be induced and for which a broad spectrum of transgenic models are available. Therefore, we describe here the mouse model of transcranial, permanent coagulation of the middle cerebral artery via electrocoagulation distal of the lenticulostriatal arteries, the so-called &#8220;coagulation model&#8221;. The resulting infarct in this model is located mainly in the cortex; the relative infarct volume in relation to brain size corresponds to the majority of human strokes. Moreover, the model fulfills the above-mentioned criteria of reproducibility and low mortality. In this video we demonstrate the surgical methods of stroke induction in the &#8220;coagulation model&#8221; and report histological and functional analysis tools.

Various murine models of middle cerebral artery occlusion (MCAO) are widely used in experimental brain research. Here, we demonstrate the model of transcranial permanent distal MCAO which produces consistent cortical infarction of a size corresponding to damage imposed by the majority of human ischemic strokes.

Stroke is the third most common cause of death and a main cause of acquired adult disability in developed countries. Only very limited therapeutical ...

Embolic Middle Cerebral Artery Occlusion (MCAO) for Ischemic Stroke with Homologous Blood Clots in Rats

Clinically, thrombolytic therapy with use of recombinant tissue plasminogen activator (tPA) remains the most effective treatment for acute ischemic stroke. However, the use of tPA is limited by its narrow therapeutic window and by increased risk of hemorrhagic transformation. There is an urgent need to develop suitable stroke models to study new thrombolytic agents and strategies for treatment of ischemic stroke. At present, two major types of ischemic stroke models have been developed in rats and mice: intraluminal suture MCAO and embolic MCAO. Although MCAO models via the intraluminal suture technique have been widely used in mechanism-driven stroke research, these suture models do not mimic the clinical situation and are not suitable for thrombolytic studies. Among these models, the embolic MCAO model closely mimics human ischemic stroke and is suitable for preclinical investigation of thrombolytic therapy. This embolic model was first developed in rats by Overgaard et al.1 in 1992 and further characterized by Zhang et al. in 19972. Although embolic MCAO has gained increasing attention, there are technical problems faced by many laboratories. To meet increasing needs for thrombolytic research, we present a highly reproducible model of embolic MCAO in the rat, which can develop a predictable infarct volume within the MCA territory. In brief, a modified PE-50 tube is gently advanced from the external carotid artery (ECA) into the lumen of the internal carotid artery (ICA) until the tip of the catheter reaches the origin of the MCA. Through the catheter, a single homologous blood clot is placed at the origin of the MCA. To identify the success of MCA occlusion, regional cerebral blood flow was monitored, neurological deficits and infarct volumes were measured. The techniques presented in this paper should help investigators to overcome technical problems for establishing this model for stroke research.

Embolic Middle Cerebral Artery Occlusion MCAO for Ischemic Stroke with Homologous Blood Clots in Rats

In this paper, we demonstrate a standard method for producing an embolic middle cerebral artery occlusion with homologous blood clots (fibrin-rich) in adult rat. This model closely mimics human ischemic stroke and is suitable for preclinical study of thrombolytic therapy for ischemic stroke.

Clinically, thrombolytic therapy with use of recombinant tissue plasminogen activator (tPA) remains the most effective treatment for acute ischemic ...

Performing Permanent Distal Middle Cerebral with Common Carotid Artery Occlusion in Aged Rats to Study Cortical Ischemia with Sustained Disability

Stroke typically occurs in elderly people with a range of comorbidities including carotid (or other arterial) atherosclerosis, high blood pressure, obesity and diabetes. Accordingly, when evaluating therapies for stroke in animals, it is important to select a model with excellent face validity. Ischemic stroke accounts for 80% of all strokes, and the majority of these occur in the territory of the middle cerebral artery (MCA), often inducing infarcts that affect the sensorimotor cortex, causing persistent plegia or paresis on the contralateral side of the body. We demonstrate in this video a method for producing ischemic stroke in elderly rats, which causes sustained sensorimotor disability and substantial cortical infarcts. Specifically, we induce permanent distal middle cerebral artery occlusion (MCAO) in elderly female rats by using diathermy forceps to occlude a short segment of this artery. The carotid artery on the ipsilateral side to the lesion was then permanently occluded and the contralateral carotid artery was transiently occluded for 60 min. We measure the infarct size using structural T2-weighted magnetic resonance imaging (MRI) at 24 hr and 8 weeks after stroke. In this study, the mean infarct volume was 4.5% &#177; 2.0% (standard deviation) of the ipsilateral hemisphere at 24 hr (corrected for brain swelling using Gerriet&#8217;s equation, n = 5). This model is feasible and clinically relevant as it permits the induction of sustained sensorimotor deficits, which is important for the elucidation of pathophysiological mechanisms and novel treatments.

Here we present a protocol to produce permanent distal middle cerebral artery occlusion in elderly female rats with simultaneous occlusion of the carotid arteries to generate large cortical infarcts and sustained deficits. We show confirmation of the lesion size using structural MRI at 24 hr and 8 weeks after stroke.

Stroke typically occurs in elderly people with a range of comorbidities including carotid (or other arterial) atherosclerosis, high blood pressure, ...

Surgical Approach for Middle Cerebral Artery Occlusion and Reperfusion Induced Stroke in Mice

Stroke is a leading cause of death worldwide and continues to be one of the major causes of long-term adult disabilities. About 87% of strokes are ischemic in origin and occur in the territory of the middle cerebral artery (MCA). Currently the only Food and Drug Administration (FDA) approved drug for the treatment of this devastating disease is tissue plasminogen activator (tPA). However, tPA has a small therapeutic window for administration (3 - 6 hr), and is only effective in 4% of the patients who actually receive it. Current research focuses on understanding the pathophysiology of stroke in order to find potential therapeutic targets. Thus, reliable models are crucial, and the MCA occlusion (MCAo) model (also termed the intraluminal filament or suture model) is deemed to be the most clinically relevant surgical model of ischemic stroke, and is fairly non-invasive and easily reproducible. Typically the MCAo model is used with rodents, especially with mice due to all the genetic variations available for this species. Here we describe (and present in the video) how to successfully perform the MCAo model (with reperfusion) in mice to generate reliable and reproducible data.

In order to understand the pathophysiology of stroke, it is important to use reliable models. This paper will describe one of the most frequently used stroke models in mice, termed the middle cerebral artery occlusion (MCAo) model (also termed the intraluminal filament or suture model) with reperfusion.