Name: isometric contractility measurement of the mouse mesenteric artery using wire myography
Uploaded: 2018-08-20T12:30:00
Description: Watch this Scientific Journal Video about Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography at JoVE.com

We thank Dr. Wei Qi He (Soochow University, Suzhou, China) and Dr. Yan Ning Qiao (Shaanxi Normal University, Xi&#39;an, China) for the technical assistance. This work was supported by the National Natural Science Foundation of China (Grant 31272311, 81373295 and 81473420) and the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (Grant No. ysxk-2016).

Animal manipulations were approved by the Institutional Animal Care and Use Committee (IACUC) of the Model Animal Research Center of Nanjing University.
1. Solution Preparation
<ol>
	<li>Prepare HEPES-Tyrode solution (H-T) using 137.0 mM NaCl, 2.7 mM KCl, 1.8 mM CaCl2, 1 mM MgCl2&#8729;6H2O, 5.6 mM D-glucose, and 10 mM HEPES, pH 7.3-7.4.</li>
	<li>Prepare HEPES-Tyrode solution without calcium (Ca2+-free H-T) using 140.6 mM NaCl, 2.7 mM KCl, 1 mM Mg...

<ol>
	<li>Bevan, J. A., Osher, J. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+direct+method+for+recording+tension+changes+in+the+wall+of+small+blood+vessels+in+vitro.">A direct method for recording tension changes in the wall of small blood vessels in vitro.</a> Agents and Actions. 2 (5), 257-260 (1972).</li><li>Mulvany, M. J., Halpern, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+properties+of+vascular+smooth+muscle+cells+in+situ.">Mechanical properties of vascular smooth muscle cells in situ.</a> Nature. 260 (5552), 617-619 (1976).</li><li>Mulvany, M. J., Halpern, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contractile+Properties+of+Small+Arterial+Resistance+Vessels+in+Spontaneously+Hypertensive+and+Normotensive+Rats.">Contractile Properties of Small Arterial Resistance Vessels in Spontaneously Hypertensive and Normotensive Rats.</a> Circulation Research. 41 (1), 19-26 (1977).</li><li>Mulvany, M. J., Nyborg, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+increased+calcium+sensitivity+of+mesenteric+resistance+vessels+in+young+and+adult+spontaneously+hypertensive+rats.">An increased calcium sensitivity of mesenteric resistance vessels in young and adult spontaneously hypertensive rats.</a> British Journal of Pharmacology. 71 (2), 585-596 (1980).</li><li>Mulvany, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Procedures for investigation of small vessels using small vessel myograph. , (2004).</li><li>Halpern, W., Mulvany, M. J., Warshaw, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+properties+of+smooth+muscle+cells+in+the+walls+of+arterial+resistance+vessels.">Mechanical properties of smooth muscle cells in the walls of arterial resistance vessels.</a> The Journal of Physiology. 275, 88-101 (1978).</li><li>Michael, S. K., 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=High+blood+pressure+arising+from+a+defect+in+vascular+function.">High blood pressure arising from a defect in vascular function.</a> Proceedings of the National Academy of Sciences of the United States of America. 105 (18), 6702-6707 (2008).</li><li>Bridges, L. E., Williams, C. L., Pointer, M. A., Awumey, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesenteric+artery+contraction+and+relaxation+studies+using+automated+wire+myography.">Mesenteric artery contraction and relaxation studies using automated wire myography.</a> Journal of Visualized Experiments. 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D., 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=Distinct+roles+for+the+kidney+and+systemic+tissues+in+blood+pressure+regulation+by+the+renin-angiotensin+system.">Distinct roles for the kidney and systemic tissues in blood pressure regulation by the renin-angiotensin system.</a> The Journal of Clinical Investigation. 115 (4), 1092-1099 (2005).</li><li>Qiao, Y. N., 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=Myosin+phosphatase+target+subunit+1+(MYPT1)+regulates+the+contraction+and+relaxation+of+vascular+smooth+muscle+and+maintains+blood+pressure.">Myosin phosphatase target subunit 1 (MYPT1) regulates the contraction and relaxation of vascular smooth muscle and maintains blood pressure.</a> The Journal of Biological Chemistry. 289 (32), 22512-22523 (2014).</li><li>He, W. Q., 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=Role+of+myosin+light+chain+kinase+in+regulation+of+basal+blood+pressure+and+maintenance+of+salt-induced+hypertension.">Role of myosin light chain kinase in regulation of basal blood pressure and maintenance of salt-induced hypertension.</a> American Journal of Physiology-Heart and Circulatory Physiology. 301 (2), H584-H591 (2011).</li><li>Yang, G. 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=Isolation+and+identification+of+a+tribenzylisoquinoline+alkaloid+from+Nelumbo+nucifera+Gaertn,+a+novel+potential+smooth+muscle+relaxant.">Isolation and identification of a tribenzylisoquinoline alkaloid from Nelumbo nucifera Gaertn, a novel potential smooth muscle relaxant.</a> Fitoterapia. 124, 58-65 (2018).</li><li>Slez&#225;k, P., Waczul&#237;kov&#225;, I., Bali&#353;, P., P&#250;zserov&#225;, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accurate+Normalization+Factor+for+Wire+Myography+of+Rat+Femoral+Artery.">Accurate Normalization Factor for Wire Myography of Rat Femoral Artery.</a> Physiological Research. 59 (6), 1033-1036 (2010).</li><li>Kearney, P. 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Hypertension is a widespread public health challenge due to its severe complications, including cardiovascular and kidney diseases16. Understanding the pathogenesis of hypertension and exploring more anti-hypertensive drugs has become an urgent task in this field. Blood pressure is generated and maintained by peripheral resistance of the circulation. According to Poiseuille&#39;s Law, the relatively small arteries generate a large proportion of circulatory resistance and serve as the dominant prod...

The small vessel myograph system used here was for measuring the isometric contraction of small resistance vessels with internal diameters ranging from 100 to 400 &#181;m. Isolated small vessels (about 2 mm long) were inserted by two 40-&#181;m diameter wires and were then mounted on the micrometer-side and transducer-side jaws sequentially. This myograph technique was first suggested in 19721 and then developed primarily by Mulvany and his colleagues2,3,4,5,6. It is now a mature technique with stable equipment, easy performance and a standard normalization procedure7,8,9. We utilized this method with some modifications for measurements in the mouse mesenteric artery.
Vascular smooth muscle lines the walls of almost all blood vessels. Their fundamental function is to generate forces through contraction in response to various stimuli. The normal contractility of vascular smooth muscle is essential for blood pressure regulation and nutrition supplement10. Abnormal regulation of blood pressure results in a variety of diseases, including hypertension, heart failure and ischaemia. Several studies have suggested that abnormal blood pressure is always associated with dysfunctional vascular smooth muscle contractility7,11,12,13. The myograph method allows investigation of isometric contractility of mouse vessels induced by various stimuli including vasoconstrictors, inhibitors and drugs. Successful measurements of contraction will help us understand the mechanisms of blood pressure maintenance and the pathogenesis of vascular smooth muscle-associated diseases and to explore novel therapeutic approaches.
Many Chinese herbs have been widely used for clinical treatment of vascular diseases; however, their effective ingredients usually remain unknown. Thus, isolation and identification of the effective components is very important for the development of novel drugs. Multi-wire myograph technology offers a simple approach for screening active components in herbs. We have reported several studies using the small vessel myograph system to investigate mouse mesenteric artery contraction and identified natural compounds with anti-hypertension activity12,13,14. Here, we describe the detailed protocol for the myograph method and assess the relaxant effect of neoliensinine isolated from embryos of lotus seed (Nelumbo nucifera Gaertn.)14.

<table>
	<tbody>
		<tr>
			<td>Multi wire myograph system</td>
			<td>DMT</td>
			<td>610-M</td>
			<td></td>
		</tr>
		<tr>
			<td>Stainless steel wire</td>
			<td>DMT</td>
			<td>400447</td>
			<td></td>
		</tr>
		<tr>
			<td>Geuder dissection scissor</td>
			<td>DMT</td>
			<td>400431</td>
			<td></td>
		</tr>
		<tr>
			<td>Dumont forceps</td>
			<td>DMT</td>
			<td>300413</td>
			<td></td>
		</tr>
		<tr>
			<td>PowerLab/8SP</td>
			<td>ADInstruments</td>
			<td>ML785</td>
			<td></td>
		</tr>
		<tr>
			<td>Software</td>
			<td>ADInstruments</td>
			<td>LabChart 5</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>SigmaAldrich</td>
			<td>S5886</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>SigmaAldrich</td>
			<td>P5405</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>SigmaAldrich</td>
			<td>C4901</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2&#183;6H2O</td>
			<td>SigmaAldrich</td>
			<td>M2393</td>
			<td></td>
		</tr>
		<tr>
			<td>D-Glucose</td>
			<td>SigmaAldrich</td>
			<td>G6152</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sangon Biotech</td>
			<td>A100511-0250</td>
			<td></td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td>SigmaAldrich</td>
			<td>S8045</td>
			<td></td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>SigmaAldrich</td>
			<td>D2650</td>
			<td></td>
		</tr>
	</tbody>
</table>

isometric contractility measurement of the mouse mesenteric artery using wire myography

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and drugs. It is widely used in many studies on the physiological functions of vascular smooth muscle, the pathogenesis of vascular diseases such as hypertension, and the development of smooth muscle relaxant drugs. The mouse is a widely used model animal with a large pool of disease models and genetically modified strains. We introduced this method to measure the isometric contraction of mouse mesenteric artery in detail. A 1.4-mm segment of mouse mesenteric resistance artery was isolated and mounted on a myograph chamber by passing two steel wires through its lumen. After equilibration and normalization steps, the vessel segment was potentiated by a high-K+ solution twice prior to the contraction assay. As an example of the application of this method in drug development, we measured the relaxant effect of a novel natural substance, neoliensinine, isolated from a Chinese herb, embryos of the lotus seed (Nelumbo nucifera Gaertn.) on mouse mesenteric arteries. The vessel segments mounted on the myograph chamber were stimulated with a high-K+ solution. When the force tension reached a stable sustained phase, cumulative doses of neoliensinine were added to the chamber. We found that neoliensinine had a dose-dependent relaxant effect on smooth muscle contraction, thus suggesting that it bears potential activity against hypertension. In addition, as the vessel segment can survive at least 4 hours after mounting and maintain contractility induced by the high-K+ solution for many times, we suggest that the wire myograph system may be used for the time-consuming process of drug screening.

We measured the isometric contractility of mouse mesenteric artery using a multi-wire myograph system and assessed the relaxant effect of neoliensinine purified from embryos of lotus seed (Nelumbo nucifera Gaertn.)14. The mouse mesenteric resistance artery was isolated, cleaned of connective tissues and cut into 1.4-mm segments. The artery segment was inserted by two steel wires in Ca2+-free H-T solution in a Petri dish, and then the segment was...

Watch this Scientific Journal Video about Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography at JoVE.com

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

The wire myograph technique is used to investigate vascular smooth muscle functions and screen new drugs. We report a detailed protocol for measuring the isometric contractility of the mouse mesenteric artery and for screening new relaxants of vascular smooth muscle.

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and ...

Our lab has been using the wire myograph method to measure vascular smooth muscle contractility for many years. We use this technique to study the mechanism of smooth muscle contraction. We use this method to explore novel drugs for hypertension therapy.The main advantage of this technique is that the vessel segment survives at least four hours after mounting and keeps the contractility induced by high potassium for many times. The multi-channel system gives the opportunity for high therapy screening of new drugs. Pin the body of the euthanized mouse with its abdomen facing up and moisten the abdomen with 70%ethanol.Then, after using scissors to cut the skin along the ventral midline from the groin, make incisions down each leg from the start of the first incision. Pull the skin back on both sides, then make similar incisions to open the peritoneum. Next, use scissors to cut the esophagus, colon and other connective tissues to completely isolate the gastrointestinal tract with feeding vasculature from the body.After rinsing the blood from the GI tract with HEPES-Tyrode, or H-T solution, transfer the isolated segment into a coated Petri dish for mesenteric artery dissection at room temperature. Smooth out the stomach, jejunum, ileum and cecum in a clockwise direction and pin the stomach and cecum on the left-and right-hand side respectively. Turn on the transmission light source of a stereoscopic microscope and fix the intestine with pins to expose the dissected mesenteric arteries.Then clamp the adipose tissues around the arteries with forceps and carefully isolate the arteries by cutting off all the connective tissues with dissection scissors. Grasp an excess artery with forceps and transfer and immerse the mesenteric artery tree into cold calcium ion-free H-T solution. Cut off a 1.4 millimeter portion of the artery proximal to the intestinal wall of a mesenteric arcade and use two forceps to open both sides of this artery segment carefully.Prepare two segments of stainless steel wire of 2.5 centimeters in length and place them into the same dish. Use forceps to gently clamp one end of the artery. Then use another forceps to carefully insert two wires into the lumen of the artery one by one.Insure that the wires are kept straight and do not touch the endothelium. Using two forceps, clamp both wires outside of the threaded vessel simultaneously and carefully transfer the vessel from the Petri dish to a myograph chamber filled with H-T solution. Screw the jaws of the chamber apart to make space for mounting, then grasp both sides of one of the two inserted wires using two forceps and place the vessel in the jaw gap.Wrap both sides of the clamped wire around the screws of the jaw connected to the micrometer. Fix the left-side screw by twisting clockwise. Then use forceps to straighten the wire.Next, fix the right-side screw by twisting clockwise. Make sure that the vessel is always inside the jaw gap but do not touch the jaw to avoid damage. Close the two jaws using the micrometer.Make sure the two jaws are close enough but that they do not touch each other, and that the unfixed wire is on top of the fixed wire. Using the right-hand forceps, carefully fold the unscrewed wire at the corner of the jaw connected to force transducer and wrap it clockwise around the right-side screw. Then, fix the screw.Repeat the unfolding and wrapping of the left side of the wire and fix the left-side screw. Next, move the jaws slightly apart without stretching the vessel by carefully rotating the micrometer so that the gap between the two jaws can just accommodate the two wires. Then use forceps to move the wire at the micrometer side to the horizontal plane of the wire at the transducer side.After mounting arteries in the other chambers, connect all the chambers to the equipment and cover the chambers. Attach the 100%oxygen supply and a temperature probe and start heating to 37 degrees Celsius. Open the charting software.Press the Start'button to start recording. Select the channel of interest from the DMT menu to open the DMT normalization window for the corresponding channel. Enter the following constant values into the window:Tissue end points a1, 0.1;Tissue end points a2, 4;Wire diameter, 40.The window then displays the calculated vessel length as 1.40 millimeters. Read the micrometer of the appropriate tissue chamber. Enter the value into the micrometer reading box and click Add Point'button.This value is the initial value of X.After a 60 second delay, the window displays the force and the effective pressure corresponding to this micrometer value. Simultaneously, the micrometer reading box becomes active. Stretch the vessel being normalized by turning the micrometer in a counter-clockwise direction.Enter the micrometer value into the micrometer reading box and click the Add Point'button. Wait for a delay time of 60 seconds again. Continue to stretch the vessel and add micrometer values until the window displays the value of micrometer X-one, which is the calculated micrometer setting required to stretch the vessel to its IC-one.Set the micrometer to the X-one value. After normalization, equilibrate the vessel in the chamber for 15 to 20 minutes. Once equilibrated, challenge the vessel with high potassium solution by replacing the H-T solution with 5 milliliters of high potassium solution to induce contraction for 10 minutes.After repeating the 10 minute incubation in fresh high-potassium solution, wash with five milliliters of H-T solution three to four times. Again, challenge the vessel with five milliliters of high potassium solution to induce contraction. After five minutes, add 0.5 microliters of the Neoliensinine stock solution into the chamber to relax the vessel at a final concentration of one micromolar Neoliensinine.When the force is stable after several minutes, add another 0.5 microliters of Neoliensinine stock solution to increase the concentration to two micromolar. Add one microliter of the stock solution each time to increase the concentration to four, six, eight and 10 micromolar to generate the dose response curve. During the normalization procedure, the vessel was stretched several times until reaching the value of IC-100 and each stretched cycle included a robust contraction, rapid relaxation and a force maintenance in 60 seconds.The contraction of the vascular smooth muscle induced by high potassium solution usually showed two phases, a robust phase and a sustained phase. We described a method to measure isometric contractility of mouse mesenteric artery using a multi-wire myograph system. This method can be used to assess the functions of vascular smooth muscle and to screen relaxants of smooth muscle.The main difference between this method and others is in the mounting steps. This step used here is easy to perform and does not damage the tissue or the device. Following this procedure, other stimulators such as EP and Angiotensin II can also be used to stimulate smooth muscle contraction in order to find some novel drugs that are sensitive to this agonist.

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Research

JoVE Journal

Medicine

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 ...

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 ...

Mesenteric Artery Contraction and Relaxation Studies Using Automated Wire Myography

Proximal resistance vessels, such as the mesenteric arteries, contribute substantially to the peripheral resistance. These small vessels of between 100-400 &mu;m in diameter function primarily in directing blood flow to various organs according to the overall requirements of the body. The rat mesenteric artery has a diameter greater than 100 &mu;m. The myography technique, first described by Mulvay and Halpern1, was based on the method proposed by Bevan and Osher2. The technique provides information about small vessels under isometric conditions, where substantial shortening of the muscle preparation is prevented. Since force production and sensitivity of vessels to different agonists is dependent on the extent of stretch, according to active tension-length relation, it is essential to conduct contraction studies under isometric conditions to prevent compliance of the mounting wires. Stainless steel wires are preferred to tungsten wires because of oxidation of the latter, which affects recorded responses3.The technique allows for the comparison of agonist-induced contractions of mounted vessels to obtain evidence for normal function of vascular smooth muscle cell receptors.
We have shown in several studies that isolated mesenteric arteries that are contracted with phenylyephrine relax upon addition of cumulative concentrations of extracellular calcium (Ca2+e). The findings led us to conclude that perivascular sensory nerves, which express the G protein-coupled Ca2+-sensing receptor (CaR), mediate this vasorelaxation response. Using an automated wire myography method, we show here that mesenteric arteries from Wistar, Dahl salt-sensitive(DS) and Dahl salt-resistant (DR) rats respond differently to Ca2+e. Tissues from Wistar rats showed higher Ca2+-sensitivity compared to those from DR and DS. Reduced CaR expression in mesenteric arteries from DS rats correlates with reduced Ca2+e-induced relaxation of isolated, pre-contracted arteries. The data suggest that the CaR is required for relaxation of mesenteric arteries under increased adrenergic tone, as occurs in hypertension, and indicate an inherent defect in the CaR signaling pathway in Dahl animals, which is much more severe in DS.
The method is useful in determining vascular reactivity ex vivo in mesenteric resistance arteries and similar small blood vessels and comparisons between different agonists and/or antagonists can be easily and consistently assessed side-by-side6,7,8.

An automated myography method for force measurements in isolated mesenteric arteries is described. It employs a Mulvany-Halpern Auto Dual Wire Myograph 510A to determine responses to phenylephrine and extracellular calcium. The method allows consistent determination of isometric responses to agonists in small vessels of diameters of 60 - 300 &mu;m, independently.

Proximal resistance vessels, such as the mesenteric arteries, contribute substantially to the peripheral resistance. These small vessels of between ...

Epidural Intracranial Pressure Measurement in Rats Using a Fiber-optic Pressure Transducer

Elevated intracranial pressure (ICP) is a significant problem in several forms of ischemic brain injury including stroke, traumatic brain injury and cardiac arrest. This elevation may result in further neurological injury, in the form of transtentorial herniation1,2,3,4, midbrain compression, neurological deficit or increased cerebral infarct2,4. Current therapies are often inadequate to control elevated ICP in the clinical setting5,6,7 . Thus there is a need for accurate methods of ICP measurement in animal models to further our understanding of the basic mechanisms and to develop new treatments for elevated ICP.
In both the clinical and experimental setting ICP cannot be estimated without direct measurement. Several methods of ICP catheter insertion currently exist. Of these the intraventricular catheter has become the clinical 'gold standard' of ICP measurement in humans8. This method involves the partial removal of skull and the instrumentation of the catheter through brain tissue. Consequently, intraventricular catheters have an infection rate of 6-11%9. For this reason, subdural and epidural cannulations have become the preferred methods in animal models of ischemic injury. 
Various ICP measurement techniques have been adapted for animal models, and of these, fluid-filled telemetry catheters10 and solid state catheters are the most frequently used11,12,13,14,15. The fluid-filled systems are prone to developing air bubbles in the line, resulting in false ICP readings. Solid state probes avoid this problem (Figure 1). An additional problem is fitting catheters under the skull or into the ventricles without causing any brain injury that might alter the experimental outcomes. Therefore, we have developed a method that places an ICP catheter contiguous with the epidural space, but avoids the need to insert it between skull and brain. 
An optic fibre pressure catheter (420LP, SAMBA Sensors, Sweden) was used to measure ICP at the epidural location because the location of the pressure sensor (at the very tip of the catheter) was found to produce a high fidelity ICP signal in this model. There are other manufacturers of similar optic fibre technologies13 that may be used with our methodology. Alternative solid state catheters, which have the pressure sensor located at the side of the catheter tip, would not be appropriate for this model as the signal would be dampened by the presence of the monitoring screw. 
Here, we present a relatively simple and accurate method to measure ICP. This method can be used across a wide range of ICP related animal models.

A novel technique to record the pressures within the skull is described. The minimally invasive method uses a fibre-optic pressure sensing system to accurately measure intracranial pressure (ICP) in anaesthetized rats without causing significant brain trauma. The technique may be used in a wide range of experimental models.

Elevated intracranial pressure (ICP) is a significant problem in several forms of ischemic brain injury including stroke, traumatic brain injury and ...

In vivo Measurement of the Mouse Pulmonary Endothelial Surface Layer

The endothelial glycocalyx is a layer of proteoglycans and associated glycosaminoglycans lining the vascular lumen. In vivo, the glycocalyx is highly hydrated, forming a substantial endothelial surface layer (ESL) that contributes to the maintenance of endothelial function. As the endothelial glycocalyx is often aberrant in vitro and is lost during standard tissue fixation techniques, study of the ESL requires use of intravital microscopy. To best approximate the complex physiology of the alveolar microvasculature, pulmonary intravital imaging is ideally performed on a freely-moving lung. These preparations, however, typically suffer from extensive motion artifact. We demonstrate how closed-chest intravital microscopy of a freely-moving mouse lung can be used to measure glycocalyx integrity via ESL exclusion of fluorescently-labeled high molecular weight dextrans from the endothelial surface. This non-recovery surgical technique, which requires simultaneous brightfield and fluorescent imaging of the mouse lung, allows for longitudinal observation of the subpleural microvasculature without evidence of inducing confounding lung injury.

In vivo Measurement of the Mouse Pulmonary Endothelial Surface Layer

The endothelial glycocalyx/endothelial surface layer is ideally studied using intravital microscopy. Intravital microscopy is technically challenging in a moving organ such as the lung. We demonstrate how simultaneous brightfield and fluorescent microscopy may be used to estimate endothelial surface layer thickness in a freely-moving in vivo mouse lung.

The endothelial glycocalyx is a layer of proteoglycans and associated glycosaminoglycans lining the vascular lumen. In vivo, the glycocalyx is highly ...

Assessing Myogenic Response and Vasoactivity In Resistance Mesenteric Arteries Using Pressure Myography

Small resistance arteries constrict and dilate respectively in response to increased or decreased intraluminal pressure; this phenomenon known as myogenic response is a key regulator of local blood flow. In isobaric conditions small resistance arteries develop sustained constriction known as myogenic tone (MT), which is a major determinant of systemic vascular resistance (SVR). Hence, ex vivo&#160;pressurized preparations of small resistance arteries are major tools to study microvascular function in near-physiological states. To achieve this, a freshly isolated intact segment of a small resistance artery (diameter ~260 &#956;m) is mounted onto two small glass cannulas and pressurized. These arterial preparations retain most in vivo characteristics and permit assessment of vascular tone in real-time. Here we provide a detailed protocol for assessing vasoactivity in pressurized small resistance mesenteric arteries from rats; these arteries develop sustained vasoconstriction - approximately 25% of maximal diameter - when pressurized at 70 mmHg. These arterial preparations may be used to study the effect of investigational compounds on relationship between intra-arterial pressure and vasoactivity and determine changes in microvascular function in animal models of various diseases.

Pressure myography is used to assess vasoactivity of small arteries that develop sustained constriction when pressurized. This manuscript provides a detailed protocol to assess in isolated segments of small mesenteric arteries from rats, vasoactivity and the effect of intraluminal pressure on vascular diameter.

Small resistance arteries constrict and dilate respectively in response to increased or decreased intraluminal pressure; this phenomenon known as myogenic ...

Isolating and Using Sections of Bovine Mesenteric Artery and Vein as a Bioassay to Test for Vasoactivity in the Small Intestine

Mammalian gastrointestinal systems are constantly exposed to compounds (desirable and undesirable) that can have an effect on blood flow to and from that system. Changes in blood flow to the small intestine can result in effects on the absorptive functions of the organ. Particular interest in toxins liberated from feedstuffs through fermentative and digestive processes has developed in ruminants as an area where productive efficiencies could be improved. The video associated with this article describes an in vitro bioassay developed to screen compounds for vasoactivity in isolated cross-sections of bovine mesenteric artery and vein using a multimyograph. Once the blood vessels are mounted and equilibrated in the myograph, the bioassay itself can be used: as a screening tool to evaluate the contractile response or vasoactivity of compounds of interest; determine the presence of receptor types by pharmacologically targeting receptors with specific agonists; determine the role of a receptor with the presence of one or more antagonists; or determine potential interactions of compounds of interest with antagonists. Through all of this, data are collected real-time, tissue collected from a single animal can be exposed to a large number of different experimental treatments (an in vitro advantage), and represents vasculature on either side of the capillary bed to provide an accurate picture of what could be happening in the afferent and efferent blood supply supporting the small intestine.

The small intestine is frequently exposed to toxins that can influence blood flow and negatively impact nutrient absorption. Using a multimyograph and mesenteric artery and vein isolates, compounds or toxins of interest can be screened for vasoactivity.

Mammalian gastrointestinal systems are constantly exposed to compounds (desirable and undesirable) that can have an effect on blood flow to and from that ...

Measurement of the Pressure-volume Curve in Mouse Lungs

In recent decades the mouse has become the primary animal model of a variety of lung diseases. In models of emphysema or fibrosis, the essential phenotypic changes are best assessed by measurement of the changes in lung elasticity. To best understand specific mechanisms underlying such pathologies in mice, it is essential to make functional measurements that can reflect the developing pathology. Although there are many ways to measure elasticity, the classical method is that of the total lung pressure-volume (PV) curve done over the whole range of lung volumes. This measurement has been made on adult lungs from nearly all mammalian species dating back almost 100 years, and such PV curves also played a major role in the discovery and understanding of the function of pulmonary surfactant in fetal lung development. Unfortunately, such total PV curves have not been widely reported in the mouse, despite the fact that they can provide useful information on the macroscopic effects of structural changes in the lung. Although partial PV curves measuring just the changes in lung volume are sometimes reported, without a measure of absolute volume, the nonlinear nature of the total PV curve makes these partial ones very difficult to interpret. In the present study, we describe a standardized way to measure the total PV curve. We have then tested the ability of these curves to detect changes in mouse lung structure in two common lung pathologies, emphysema and fibrosis. Results showed significant changes in several variables consistent with expected structural changes with these pathologies. This measurement of the lung PV curve in mice thus provides a straightforward means to monitor the progression of the pathophysiologic changes over time and the potential effect of therapeutic procedures.

Here we present a protocol to simply and reliably measure the lung pressure-volume curve in mice, showing that it is sufficiently sensitive to detect phenotypic parenchymal changes in two common lung pathologies, pulmonary fibrosis and emphysema. This metric provides a means to quantify the lung&#8217;s structural changes with developing pathology.

In recent decades the mouse has become the primary animal model of a variety of lung diseases. In models of emphysema or fibrosis, the essential ...

Murine Model of Femoral Artery Wire Injury with Implantation of a Perivascular Drug Delivery Patch

Percutaneous interventions including balloon angioplasty and stenting have been used to restore blood flow in vessels with occlusive vascular disease. While these therapies lead to the rapid restoration of blood flow, these technologies remain limited by restenosis in the case of bare metal stents and angioplasty, or reduced healing and possibly enhanced risk of thrombosis in the case of drug eluting stents. A key pathophysiological mechanism in the formation of restenosis is intimal hyperplasia caused by the activation of vascular smooth muscle cells and inflammation due to arterial stretch and injury. Surgeries that induce arterial injury in genetically modified mice are useful for the mechanistic study of the vascular response to injury but are often technically challenging to perform in mouse models due to the their small size and lack of appropriate sized devices. We describe two approaches for a surgical technique that induces endothelial denudation and arterial stretch in the femoral artery of mice to produce robust neointimal hyperplasia. The first approach creates an arteriotomy in the muscular branch of the femoral artery to obtain vascular access. Following wire injury this arterial branch is ligated to close the arteriotomy. A second approach creates an arteriotomy in the main femoral artery that is later closed through localized cautery. This method allows for vascular access through a larger vessel and, consequently, provides a less technically demanding procedure that can be used in smaller mice. Following either method of arterial injury, a degradable drug delivery patch can be placed over or around the injured artery to deliver therapeutic agents.

We describe a surgical technique that produces wire injury in the femoral artery of mice to induce neointimal hyperplasia to serve as a model testing system for the perivascular delivery of therapeutic compounds for the inhibition of restenosis.

Percutaneous interventions including balloon angioplasty and stenting have been used to restore blood flow in vessels with occlusive vascular disease. ...

A Murine Model of Arterial Restenosis: Technical Aspects of Femoral Wire Injury

Cardiovascular disease caused by atherosclerosis is the leading cause of death in the developed world. Narrowing of the vessel lumen, due to atherosclerotic plaque development or the rupturing of established plaques, interrupts normal blood flow leading to various morbidities such as myocardial infarction and stroke. In the clinic endovascular procedures such as angioplasty are commonly performed to reopen the lumen. However, these treatments inevitably damage the vessel wall as well as the vascular endothelium, triggering an excessive healing response and the development of a neointimal plaque that extends into the lumen causing vessel restenosis (re-narrowing). Restenosis remains a major cause of failure of endovascular treatments for atherosclerosis. Thus, preclinical animal models of restenosis are vitally important for investigating the pathophysiological mechanisms as well as translational approaches to vascular interventions. Among several murine experimental models, femoral artery wire injury is widely accepted as the most suitable for studies of post-angioplasty restenosis because it closely resembles the angioplasty procedure that injures both endothelium and vessel wall. However, many researchers have difficulty utilizing this model due to its high degree of technical difficulty. This is primarily because a metal wire needs to be inserted into the femoral artery, which is approximately three times thinner than the wire, to generate sufficient injury to induce prominent neointima. Here, we describe the essential surgical details to effectively overcome the major technical difficulties of this model. By following the presented procedures, performing the mouse femoral artery wire injury becomes easier. Once familiarized, the whole procedure can be completed within 20 min.

The mouse femoral artery wire injury model of restenosis is technically challenging. In this protocol we show the key technical details essential for successfully performing wire injury to induce consistent&#160;neointima for studies of restenosis.