This work was supported by the National Institutes of Health (NIH/NHLBI) [Grant no. HL114869] and the support from UTHSC to SM.

Ethics statement: All animal procedures mentioned in this video-article were reviewed and approved by the Animal Care and Use Committee (IACUC)&#160;at the University of Tennessee Health Science Center.
Note: Use sterile microsurgery instruments throughout the surgical procedure. Surgical instruments may be sterilized utilizing an infrared sterilizer at an optimum sterilizing temperature of 1,500 &#176;F (815.6&#160;&#176;C). Telemeters can be reused, however, before inserting it in the animal make sure to sterilize the entire transmitter according to the manufacturer instructions and that the tip of the catheter has been refilled with a special gel provided by the manufacturer.
1. Experimental Animals
<ol>
	<li>Obtain an IACUC approval for all experiments that will be performed. Consultation with institutional IACUC is highly recommended regarding requirements for post-operative analgesic use after this procedure.</li>
	<li>Keep the animals in climate-controlled rooms having an ambient temperature of 21&#160;&#176;C, 60% relative humidity, and a 12-hr light-dark cycle with free access to food and water. 
	Note: Because the mouse body has to accommodate the telemetry probe (approximatively 1 cm diameter x&#160;2 cm long), it is preferable to use mice that weigh 20 g or more.</li>
</ol>
2. Anesthesia and Operative Preparation
<ol>
	<li>Weigh the mouse using a precision scale and&#160;record its&#160;weight. Make sure to handle the animal gently and quietly.</li>
	<li>Place the animal into the induction chamber and close it. Set oxygen flow rate at 0.5 L/min and set isoflurane concentration at 4 - 5% .</li>
	<li>When the mouse loses consciousness, place it on a body warming plate maintained at 36 - 37 &#176;C. Maintain the anesthesia via nosecone with isoflurane set at 2% (keep flow rate at&#160;0.5 L/min).</li>
	<li>Prepare the operation regions by removing the hair from the back of the neck and the ventral aspect of the neck by applying hair removal cream.</li>
	<li>Treat the incision site with 3 applications of surgical scrub (betadine solution) alternating with 70% isopropyl alcohol.</li>
</ol>
3. Surgery&#160;
<ol>
	<li>Place the mouse in a supine position. Check for reflexes by pinching the foot, and adjust anesthesia&#160;until&#160;there is no response. Make an approximately 1-cm midline incision below the neck of the mouse with a scalpel. In the left side of the cut create a subcutaneous space by carefully separating the skin from the underlying connective tissue.</li>
	<li>Flip the mouse, and use a scalpel to make a skin incision of approximately 1.5 cm in the dorsal left side behind the scapula. Create a subcutaneous pocket along the animal&#39;s flank large enough to accommodate the device. Insert the transmitter into the pocket.</li>
	<li>Insert a small hemostat clamp in the back incision and maneuver it subcutaneously towards the anterior neck opening. Using the inserted-hemostat clamp, gently grasp a non-toxic polyethylene tube (4 cm length x&#160;1 mm I.D.).
	<ol>
		<li>Pull the hemostat back through the tunnel out the lateral incision in the back until the tubing protrudes from both abdominal and dorsal incision, release the tube from the hemostat. From the back, insert the catheter sensor into the tube to tunnel the tip of the pressure sensing catheter through the neck. From the neck anterior, pull and remove the polyethylene tube and close the dorsal incision using metal clips.</li>
	</ol>
	</li>
	<li>Carefully separate the mandibular glands using sterile cotton tip applicators and&#160;retract the left mandibular gland using an elastic stay hook. Using fine-tipped curved forceps, locate the carotid artery along the left side of the trachea.&#160;Keep the surgical site sterile&#160; by placing and securing a sterile drape.
	<ol>
		<li>Carefully isolate the vessel from the surrounding tissue and gently separate the vagus nerve (whitish in color) that is along the carotid artery away from the artery. Be careful not to cut or damage the nerve or the artery.</li>
	</ol>
	</li>
	<li>Pass three pieces of non-absorbable 7-0 suture underneath the isolated carotid artery section. Tie the cranial suture to close off blood flow. Pull the suture that is closest to the sternum to temporarily occlude blood flow from the aorta.</li>
	<li>Make a loose knot using the middle suture.&#160;This will be used to secure the catheter in the vessel. Cut a small incision into the artery between the cranial and the sternal sutures using micro-scissors.</li>
	<li>Grab the catheter with special vessel cannulation forceps, being careful not to squeeze the catheter to prevent gel loss from the probe. Gently, grab the artery with a fine tip curved tweezers forceps, retrieve the catheter, and insert it in the vessel through the small incision.</li>
	<li>Tighten the middle suture node around the artery and gently advance the catheter. Gently release the suture that is proximal to the sternum and continue to advance the catheter towards the transverse aorta.
	<ol>
		<li>Observe the mark on the catheter that gives an approximate index of how far the catheter needs to be inserted. Once the point is reached, gently tighten both the lower and the upper suture around the catheter. The catheter is secured to the carotid artery by suture knots.</li>
	</ol>
	</li>
	<li>Close the skin incision with non-absorbable 5-0 suture. Once closed, seal the incision with tissue adhesive.</li>
</ol>
4. Surgical Recovery and BP Measurements
<ol>
	<li>Monitor animal closely for the return of normal postures and behaviors. During the 24 hr post-surgery period administer analgesia as directed by a staff veterinarian.</li>
	<li>Once the animals have recovered (5 - 7 days post-surgery), house them individually in a regular mouse cage placed on top of the telemetry receiver plate.</li>
	<li>Turn the implanted transmitters &#34;on&#34; and &#34;off&#34; by using a magnetic device briefly positioned close to the animal from the outside of the cage.</li>
</ol>

<ol>
	<li>Danaei, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+preventable+causes+of+death+in+the+United+States:+comparative+risk+assessment+of+dietary,+lifestyle,+and+metabolic+risk+factors.">The preventable causes of death in the United States: comparative risk assessment of dietary, lifestyle, and metabolic risk factors.</a> PLoS Med. 6 (4), e1000058 (2009).</li><li>Dornas, W. C., Silva, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+for+the+study+of+arterial+hypertension.">Animal models for the study of arterial hypertension.</a> J Biosci. 36 (4), 731-737 (2011).</li><li>Henze, 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=Persistent+alterations+in+heart+rate+variability,+baroreflex+sensitivity,+and+anxiety-like+behaviors+during+development+of+heart+failure+in+the+rat.">Persistent alterations in heart rate variability, baroreflex sensitivity, and anxiety-like behaviors during development of heart failure in the rat.</a> Am J Physiol Heart Circ Physiol. 295 (1), H29-H38 (2008).</li><li>Hoffmann, D. S., 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=Chronic+tempol+prevents+hypertension,+proteinuria,+and+poor+feto-placental+outcomes+in+BPH/5+mouse+model+of+preeclampsia.">Chronic tempol prevents hypertension, proteinuria, and poor feto-placental outcomes in BPH/5 mouse model of preeclampsia.</a> Hypertension. 51 (4), 1058-1065 (2008).</li><li>Lerman, L. O., Chade, A. R., Sica, V., Napoli, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+hypertension:+an+overview.">Animal models of hypertension: an overview.</a> J Lab Clin Med. 146 (3), 160-173 (2005).</li><li>Johns, C., Gavras, I., Handy, D. E., Salomao, A., Gavras, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Models+of+experimental+hypertension+in+mice.">Models of experimental hypertension in mice.</a> Hypertension. 28 (6), 1064-1069 (1996).</li><li>Vatner, S. F., Braunwald, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiovascular+control+mechanisms+in+the+conscious+state.">Cardiovascular control mechanisms in the conscious state.</a> N Engl J Med. 293 (19), 970-976 (1975).</li><li>Zhao, X., 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=Arterial+Pressure+Monitoring+in+Mice.">Arterial Pressure Monitoring in Mice.</a> Curr Protoc Mouse Biol. 1, 105-122 (2011).</li><li>Whitesall, S. E., Hoff, J. B., Vollmer, A. P., D'Alecy, L. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+simultaneous+measurement+of+mouse+systolic+arterial+blood+pressure+by+radiotelemetry+and+tail-cuff+methods.">Comparison of simultaneous measurement of mouse systolic arterial blood pressure by radiotelemetry and tail-cuff methods.</a> Am J Physiol Heart Circ Physiol. 286 (6), H2408-H2415 (2004).</li><li>Kurtz, T. W., 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=Recommendations+for+blood+pressure+measurement+in+humans+and+experimental+animals.+Part+2:+Blood+pressure+measurement+in+experimental+animals:+a+statement+for+professionals+from+the+subcommittee+of+professional+and+public+education+of+the+American+Heart+Association+council+on+high+blood+pressure+research.">Recommendations for blood pressure measurement in humans and experimental animals. Part 2: Blood pressure measurement in experimental animals: a statement for professionals from the subcommittee of professional and public education of the American Heart Association council on high blood pressure research.</a> Hypertension. 45 (2), 299-310 (2005).</li><li>Kurtz, T. W., 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=Recommendations+for+blood+pressure+measurement+in+animals:+summary+of+an+AHA+scientific+statement+from+the+Council+on+High+Blood+Pressure+Research,+Professional+and+Public+Education+Subcommittee.">Recommendations for blood pressure measurement in animals: summary of an AHA scientific statement from the Council on High Blood Pressure Research, Professional and Public Education Subcommittee.</a> Arterioscler Thromb Vasc Biol. 25 (3), 478-479 (2005).</li></ol>

The authors have nothing to disclose.

Implantable radio-telemetry has improved significantly over the last decade; smaller probe size makes the implant less traumatic for the animal, prolonged battery life helps to reduce the costs, and independent telemeter frequencies eliminate crosstalk between receivers. Telemetry is considered the state-of-the-art method for collecting a wide variety of physiological parameters from freely moving animals without the artifacts associated with the use of restraint, human interaction, or anesthesia that are required by other techniques8,9 .
However, some of the disadvantages of his technique are associated with the initial costs of the instrument and software. The transmitters are fragile and susceptible to damage, and the battery eventually does run out of power and&#160;need to be replaced. Although the company offers to refurbish those damaged probes at a lower cost, the cost can be still prohibitive for some laboratories. Furthermore, this procedure can be technically challenging and practice is required to achieve reliable BP measurement. Finally, there is some post-surgery associated mortality, which in our hands is about 5%.&#160;This can dramatically increase if a specific treatment has to be tested&#160;or if a genetic manipulation&#160;compromises the mouse health.
The following critical factors are essential for the successful execution of the procedure: maintain tissue hydration with sterile saline throughout the entire procedure. Always handle the transmitter with great care;&#160;avoid holding it by the pressure sensor as this may cause the gel to leak out or damage the transmitter. When inserting the catheter, tie the central suture with a double knot, as failure to do so will result in the catheter exiting the vessel. The required length of the catheter that has to be inserted in the carotid can change according to the mouse strain and weight used in that particular study. Therefore, it is highly recommended to run some preliminary experiment to determine how deep the catheter needs to be inserted to avoid occlusion of the aorta. Finally, monitor the animal daily and make sure that the skin above the transmitter is not stretched or necrotic. If extended necrosis or infection occurs, euthanize the animals according to institutional policy.

Hypertension is one of the major risk factors for cardiovascular diseases, arguably it is a major public health issue both in developed and developing countries1. Several animal models of experimental hypertension have been developed to mimic hypertensive responses like those observed in humans2. Among others, the ambulatory mouse represents an excellent model to study the genesis and the progression of hypertension allowing in&#160;vivo analysis of the consequences of chronic exposure to hypertension.
Blood pressure (BP) monitoring in mice has helped researchers to unravel several mechanisms involved in the physiology and pathophysiology of diseases such as hypertension and heart failure3,4. Indeed, manipulation of the mouse genome allowed generation of transgenic or gene-targeted models suitable for studying hypertension5,6. However, even gentle manipulation of conscious mice induces excitements that can potentially introduce artifacts during data acquisition, while use of sedation or tranquilizers profoundly affect blood pressure7. These aspects are particularly important and must be taken in consideration when attempting long-term BP monitoring.
There are several ways to record BP in mice, and a comparison between the most common techniques currently available has been discussed elsewhere8,9. However, the AHA recommendations for BP measurement concluded that intra-arterial measurement of BP are generally preferred because of their ability to directly measure BP over an extended period of time10. Radio-telemetry coupled with direct measurement of arterial pressure is the state-of-the-art method for monitoring physiological functions in awake and freely moving laboratory animals while minimizing stress and environmentally-associated artifacts9,11. Radio-telemetry offers the ability to automatically collect blood pressures, heart rate, body temperature and animal activity from multiple conscious animals.
Although this methodology is becoming very popular in many laboratories, radio-telemetry implantation in mice can be technically challenging. Here we show a step-by-step protocol that illustrates how to implant a pressure transducer in mice. The technique involves subcutaneous insertion of the probe in the mouse body, channel the catheter to the neck and forward near the aortic arch via the left carotid artery. Remotely captured data are shown live on the computer monitor.&#160;Data are also stored for &#34;off-line&#34; analysis.

<table><tbody><tr><td>Small animal anesthesia system</td><td>Kent Scientific Corp, Torrington, Connecticut, USA</td><td></td><td>low-flow small animal anesthesia system</td></tr><tr><td>Pad warmer and mouse termometer</td><td>Kent Scientific Corp, Torrington, Connecticut, USA</td><td></td><td>allows monitoring body temperature, and homeothermic control in small animals</td></tr><tr><td>Binocular Microscope</td><td>Kent Scientific Corp, Torrington, Connecticut, USA</td><td>KSCXTS-1121</td><td>binocular body with boom stand pole and top LED</td></tr><tr><td>Hemostat Forceps</td><td>Kent Scientific Corp, Torrington, Connecticut, USA</td><td>INS750451</td><td>used to clamp blood vessels or tag sutures</td></tr><tr><td>Small metal Clips, 7 mm, Stainless Steel</td><td>Kent Scientific Corp, Torrington, Connecticut, USA</td><td>INS750344</td><td>used for skin closure</td></tr><tr><td>Betadine solution</td><td>Purdue Products L.P., Stamford, CT, USA</td><td>NDC-67618-150-01</td><td>10% povidone iodine topical solution</td></tr><tr><td>Normal saline solution</td><td>Abott Laboratories</td><td>04930-04-10</td><td>needed for preventing tissue from drying.</td></tr><tr><td>Nair (Hair remover lotion)</td><td></td><td></td><td>needed for fur removal from the site of incision/surgery</td></tr><tr><td>Braide silk suture</td><td>Teleflex Medical OEM, Coventry, Connecticut, USA</td><td></td><td>Size 5.0, 6.0, 7.0</td></tr><tr><td>Ethanol</td><td></td><td>2716</td><td>70% ethanol for disinfection</td></tr><tr><td>Spring scissors&amp;nbsp;</td><td>Fine Science Tool</td><td>15000-10</td><td>for minor dissection</td></tr><tr><td>Scissors (angled to side)</td><td>Fine Science Tool</td><td>14063-011</td><td>No. 3 handle</td></tr><tr><td>Scalpel blade</td><td></td><td>2976-0</td><td>No. 10</td></tr><tr><td>Forceps (curved)</td><td>Fine Science Tool</td><td>11150-10</td><td>for holding tissue</td></tr><tr><td>Forceps (straight)</td><td>Fine Science Tool</td><td>11151-10</td><td>for holding tissue</td></tr><tr><td>Needle holder&amp;nbsp;</td><td>Fine Science Tool</td><td>12002-12</td><td>for suturing</td></tr><tr><td>Fine needle nose Forceps</td><td>Fine Science Tool</td><td></td><td></td></tr><tr><td>Isoflurane</td><td>Henry Schein&amp;nbsp;Animal Health, Melville, New York, USA</td><td></td><td>a general inhalation anesthetic agent</td></tr><tr><td>Sterilizer</td><td>Benchmark Scientific, 116 Corporate Blvd, South Plainfield, NJ, USA</td><td>B1000</td><td>sterilize surgical tools&amp;nbsp;in 5-10 seconds using infrared heating</td></tr><tr><td>Gauze Pads</td><td>Johnson &amp;amp; Johnson, New Brunswick, NJ, USA</td><td>JJ8513</td><td>to use for wound cleaning, prepping, scrubbing or dressing</td></tr><tr><td>Telemetry Device</td><td>Data Sciences International, St. Paul, MN, USA</td><td>DSI-PA-C10</td><td>to record blood pressure in freely moving mice</td></tr><tr><td>Telemetry receiver system&amp;nbsp; coumpled with a PC</td><td>Data Sciences International, St. Paul, MN, USA</td><td></td><td></td></tr><tr><td>Tubing</td><td>Instech Laboratories, Plymouth Meeting, PA USA</td><td>BTPE-90</td><td></td></tr><tr><td>Vessel Cannulation Forceps, 13 cm, 0.5 mm OD</td><td>World Precision Instruments</td><td>503374</td><td>special vessel cannulation forceps</td></tr><tr><td>Tissue adhesive</td><td>3M Animal Care Products, St. Paul, MN, USA</td><td>NAC No.:&amp;nbsp;11380041</td><td>use to close minor wounds, often eliminating the need for sutures and/or bandages</td></tr><tr><td>Weighing scale&amp;nbsp;</td><td></td><td>BB300</td><td>precision analytical laboratory balance</td></tr></tbody></table>

long-term blood pressure measurement in freely moving mice using telemetry

During the development of new vasoactive agents, arterial blood pressure monitoring is crucial for evaluating the efficacy of the new proposed drugs. Indeed, research focusing on the discovery of new potential therapeutic targets using genetically altered mice requires a reliable, long-term assessment of the systemic arterial pressure variation. Currently, the gold standard for obtaining long-term measurements of blood pressure in ambulatory mice uses implantable radio-transmitters, which require&#160;artery cannulation. This technique eliminates the need for tethering, restraining, or anesthetizing the animals which introduce stress and artifacts during data sampling. However, arterial blood pressure monitoring in mice via catheterization can be rather challenging due to the small size of the arteries. Here we present a step-by-step guide to illustrate the crucial key passages for a successful subcutaneous implantation of radio-transmitters and carotid artery cannulation in mice. We also include examples of long-term blood pressure activity taken from freely moving mice after a period of post-surgery recovery. Following this procedure will allow reliable direct blood pressure recordings from multiple animals simultaneously.

Data can be acquired remotely by a receiver; traces are visualized on a computer screen for quality control (Figure 1a). Details such as animal ID, diastolic blood pressure and&#160;systolic blood pressure&#160;are also shown (Figure 1b). Arterial BP can be recorded continuously (24/7), or for short programmed intervals (i.e., 60 sec&#160;acquisition every hour).&#160;Data can be automatically stored in a hard disk for later analysis. Averaged BP data from a 3-day continuous recording are shown (Figure 2),&#160;it is possible to appreciate the circadian rhythm variation between dark and light cycle. Average of pressure variation and heart rate were calculated and plotted against time.
<img alt="Figure 1" src="/files/ftp_upload/53991/53991fig1.jpg" /> 
Figure 1. Typical Blood Pressure Tracings of 4 Different Mice Implanted with Telemetric Device. (A) Tracings showing real-time arterial blood pressure changes (mmHg) over a 5 min&#160;interval. Data are acquired simultaneously from four different adult mice 5 days after implantation. (B) Tracing at higher temporal resolution extracted from A, it is possible to appreciate blood pressure diastolic and systolic values, BP cycle duration,&#160;and heart rate. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53991/53991fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/53991/53991fig2.jpg" /> 
Figure 2.&#160;Long-term Arterial Blood Pressure Shows Circadian Rhythm Variation. Averaged pressure data illustrating the values for (A) systolic pressure (SP), (B) diastolic pressure (DP), (C) mean arterial pressure (MAP), and (D) heart rate expressed in beats/min. Data were extracted from continuous recordings taken during the day (light cycle, L) or night (dark cycle, D). Recording started 7 days post-surgery. All data are expressed as mean &#177; SEM (n = 4 mice). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53991/53991fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Long-term Blood Pressure Measurement in Freely Moving Mice Using Telemetry at JoVE.com

Long-term Blood Pressure Measurement in Freely Moving Mice Using Telemetry

The goal of this protocol is to assess systemic blood pressure in conscious freely moving mice using implantable radio-telemetry devices.

During the development of new vasoactive agents, arterial blood pressure monitoring is crucial for evaluating the efficacy of the new proposed drugs. ...

long-term-blood-pressure-measurement-freely-moving-mice-using

Nanyang Technological University

Research

JoVE Journal

Medicine

18.4K Views.  University of Tennessee Health Sciences Center. The goal of this protocol is to assess systemic blood pressure in conscious freely moving mice using implantable radio-telemetry devices.

Video: Long-term Blood Pressure Measurement in Freely Moving Mice Using Telemetry

Implantation of Radiotelemetry Transmitters Yielding Data on ECG, Heart Rate, Core Body Temperature and Activity in Free-moving Laboratory Mice

The laboratory mouse is the animal species of choice for most biomedical research, in both the academic sphere and the pharmaceutical industry. Mice are a manageable size and relatively easy to house. These factors, together with the availability of a wealth of spontaneous and experimentally induced mutants, make laboratory mice ideally suited to a wide variety of research areas.
In cardiovascular, pharmacological and toxicological research, accurate measurement of parameters relating to the circulatory system of laboratory animals is often required. Determination of heart rate, heart rate variability, and duration of PQ and QT intervals are based on electrocardiogram (ECG) recordings. However, obtaining reliable ECG curves as well as physiological data such as core body temperature in mice can be difficult using conventional measurement techniques, which require connecting sensors and lead wires to a restrained, tethered, or even anaesthetized animal. Data obtained in this fashion must be interpreted with caution, as it is well known that restraining and anesthesia can have a major artifactual influence on physiological parameters1, 2.
Radiotelemetry enables data to be collected from conscious and untethered animals. Measurements can be conducted even in freely moving animals, and without requiring the investigator to be in the proximity of the animal. Thus, known sources of artifacts are avoided, and accurate and reliable measurements are assured. This methodology also reduces interanimal variability, thus reducing the number of animals used, rendering this technology the most humane method of monitoring physiological parameters in laboratory animals3, 4. Constant advancements in data acquisition technology and implant miniaturization mean that it is now possible to record physiological parameters and locomotor activity continuously and in realtime over longer periods such as hours, days or even weeks3, 5.
Here, we describe a surgical technique for implantation of a commercially available telemetry transmitter used for continuous measurements of core body temperature, locomotor activity and biopotential (i.e. onelead ECG), from which heart rate, heart rate variability, and PQ and QT intervals can be established in freeroaming, untethered mice. We also present pre-operative procedures and protocols for post-operative intensive care and pain treatment that improve recovery, well-being and survival rates in implanted mice5, 6.

A surgical technique for implantation of commercially available telemetry transmitters used for continuous measurement of biopotential (one-lead ECG), heart rate, core body temperature and locomotor activity in freely moving mice is shown. Recommendations and protocols for post-operative care and pain relief, improving recovery, well being and survival rate are also presented.

The laboratory mouse is the animal species of choice for most biomedical research, in both the academic sphere and the pharmaceutical industry. Mice are a ...

Measuring Blood Pressure in Mice using Volume Pressure Recording, a Tail-cuff Method

The CODA 8-Channel High Throughput Non-Invasive Blood Pressure system measures the blood pressure in up to 8 mice or rats simultaneously. The CODA tail-cuff system uses Volume Pressure Recording (VPR) to measure the blood pressure by determining the tail blood volume. A specially designed differential pressure transducer and an occlusion tail-cuff measure the total blood volume in the tail without the need to obtain the individual pulse signal. Special attention is afforded to the length of the occlusion cuff in order to derive the most accurate blood pressure readings. VPR can easily obtain readings on dark-skinned rodents, such as C57BL6 mice and is MRI compatible. The CODA system provides you with measurements of six (6) different blood pressure parameters; systolic and diastolic blood pressure, heart rate, mean blood pressure, tail blood flow, and tail blood volume. Measurements can be made on either awake or anesthetized mice or rats. The CODA system includes a controller, laptop computer, software, cuffs, animal holders, infrared warming pads, and an infrared thermometer. There are seven different holder sizes for mice as small as 8 grams to rats as large as 900 grams.

The CODA 8-Channel High Throughput Non-Invasive Blood Pressure system measures the blood pressure in up to 8 mice or rats simultaneously. This tail-cuff system uses Volume Pressure Recording (VPR) to measure the blood pressure by determining the tail blood volume.

The CODA 8-Channel High Throughput Non-Invasive Blood Pressure system measures the blood pressure in up to 8 mice or rats simultaneously. The CODA ...

Biology

Monitoring of Systemic and Hepatic Hemodynamic Parameters in Mice

The use of mouse models in experimental research is of enormous importance for the study of hepatic physiology and pathophysiological disturbances. However, due to the small size of the mouse, technical details of the intraoperative monitoring procedure suitable for the mouse were rarely described. Previously we have reported a monitoring procedure to obtain hemodynamic parameters for rats. Now, we adapted the procedure to acquire systemic and hepatic hemodynamic parameters in mice, a species ten-fold smaller than rats. This film demonstrates the instrumentation of the animals as well as the data acquisition process needed to assess systemic and hepatic hemodynamics in mice. Vital parameters, including body temperature, respiratory&#160;rate&#160;and heart&#160;rate were recorded throughout the whole procedure. Systemic hemodynamic parameters consist of carotid artery pressure (CAP) and central venous pressure (CVP). Hepatic perfusion parameters include portal vein pressure (PVP), portal flow rate as well as the flow rate of the common hepatic artery (table 1). Instrumentation and data acquisition to record the normal values was completed within 1.5 h. Systemic and hepatic hemodynamic parameters remained within normal ranges during this procedure.
This procedure is challenging but feasible. We have already applied this procedure to assess hepatic hemodynamics in normal mice as well as during 70% partial hepatectomy and in liver lobe clamping experiments. Mean PVP after resection (n= 20), was 11.41&#177;2.94 cmH2O which was significantly higher (P&#60;0.05) than before resection (6.87&#177;2.39 cmH2O). The results of liver lobe clamping experiment indicated that this monitoring procedure is sensitive and suitable for detecting small changes in portal pressure and portal flow rate. In conclusion, this procedure is reliable in the hands of an experienced micro-surgeon but should be limited to experiments where mice are absolutely needed.

This film demonstrates how to acquire systemic and hepatic hemodynamics in mice. The whole monitoring includes acquisition of vital parameters, systemic blood pressure, central venous pressure, common hepatic artery flow rate, and portal vein pressure as well as the portal flow rate in mice.

The use of mouse models in experimental research is of enormous importance for the study of hepatic physiology and pathophysiological disturbances. ...

Intrauterine Telemetry to Measure Mouse Contractile Pressure In Vivo

A complex integration of molecular and electrical signals is needed to transform a quiescent uterus into a contractile organ at the end of pregnancy. Despite the discovery of key regulators of uterine contractility, this process is still not fully understood. Transgenic mice provide an ideal model in which to study parturition. Previously, the only method to study uterine contractility in the mouse was ex vivo isometric tension recordings, which are suboptimal for several reasons. The uterus must be removed from its physiological environment, a limited time course of investigation is possible, and the mice must be sacrificed. The recent development of radiometric telemetry has allowed for longitudinal, real-time measurements of in vivo intrauterine pressure in mice. Here, the implantation of an intrauterine telemeter to measure pressure changes in the mouse uterus from mid-pregnancy until delivery is described. By comparing differences in pressures between wild type and transgenic mice, the physiological impact of a gene of interest can be elucidated. This technique should expedite the development of therapeutics used to treat myometrial disorders during pregnancy, including preterm labor.

Intrauterine Telemetry to Measure Mouse Contractile Pressure In Vivo

This manuscript provides a protocol for implanting telemeters in the mouse for the purpose of measuring intrauterine pressures during pregnancy.

A complex integration of molecular and electrical signals is needed to transform a quiescent uterus into a contractile organ at the end of pregnancy. ...

Novel Approach for Simultaneous Recording of Renal Sympathetic Nerve Activity and Blood Pressure with Intravenous Infusion in Conscious, Unrestrained Mice.

Renal sympathetic nerves contribute significantly to both physiological and pathophysiological phenomena. Evaluating renal sympathetic nerve activity (RSNA) is of great interest in many areas of research such as chronic kidney disease, hypertension, heart failure, diabetes and obesity. Unequivocal assessment of the role of the sympathetic nervous system is thus imperative for proper interpretation of experimental results and understanding of disease processes. RSNA has been traditionally measured in anesthetized rodents, including mice. However, mice usually exhibit very low systemic blood pressure and hemodynamic instability for several hours during anesthesia and surgery. Meaningful interpretation of RSNA is confounded by this non-physiological state, given the intimate relationship between sympathetic nervous tone and cardiovascular status. To address this limitation of traditional approaches, we developed a new method for measuring RSNA in conscious, freely-moving mice. Mice were chronically instrumented with radio-telemeters for continuous monitoring of blood pressure as well as a jugular venous infusion catheter and custom-designed bipolar electrode for direct recording of RSNA. Following a 48-72 hour recovery period, survival rate was 100% and all mice behaved normally. At this time-point, RSNA was successfully recorded in 80% of mice, with viable signals acquired up to 4 and 5 days post-surgery in 70% and 50% of mice, respectively. Physiological blood pressures were recorded in all mice (116&plusmn;2 mmHg; n=10). Recorded RSNA increased with eating and grooming, as well-established in the literature. Furthermore, RSNA was validated by ganglionic blockade and modulation of blood pressure with pharmacological agents. Herein, an effective and manageable method for clear recording of RSNA in conscious, freely-moving mice is described.

Anesthetized mice exhibit non-physiological systemic blood pressure, which precludes meaningful assessment of autonomic tone given the intimate relationship between blood pressure and the autonomic nervous system. Thus, a novel method to simultaneously record renal sympathetic nerve activity and blood pressure with intravenous infusion in conscious mice is outlined.

Renal sympathetic nerves contribute significantly to both physiological and pathophysiological phenomena. Evaluating renal sympathetic nerve activity ...

Simultaneous Electrocardiography Recording and Invasive Blood Pressure Measurement in Rats

For studies related to cardiovascular physiology or pathophysiology, blood pressure (BP) and electrocardiography are basic observational parameters. Research focusing on cardiovascular disease models, potential cardiovascular therapeutic targets or pharmaceutical agents requires assessment of systemic arterial pressure and heart rhythm changes. In situations where radio telemetry systems are not available or affordable, the technique of femoral artery cannulation is an alternative way to obtain intra-arterial pressure waveform recordings and systemic BP measurements. This technique is economical and can be performed with standard equipment in animal facilities. However, invasive arterial pressure recording requires cannulation of small arteries, which can be a challenging surgical skill. Here, we present step-by-step protocols for femoral artery cannulation procedures. Key procedures include the calibration of the data acquisition system, tissue dissection and femoral artery cannulation, and setup of the arterial cannulation system for pressure recording. Surface electrocardiography recording procedures are also included. We also present examples of BP recordings from normotensive and hypertensive rats. This protocol allows reliable direct recordings of systemic BP with simultaneous electrocardiography.

Here, we describe a setup for simultaneous recording of electrocardiography and intra-arterial blood pressure (BP) in experimental rats, which can be done with standard equipment in animal facilities and can be applied to physiological or pharmacological studies to investigate pathogenic or therapeutic mechanisms in cardiovascular medicine.

For studies related to cardiovascular physiology or pathophysiology, blood pressure (BP) and electrocardiography are basic observational parameters. ...

Implantation of Combined Telemetric ECG and Blood Pressure Transmitters to Determine Spontaneous Baroreflex Sensitivity in Conscious Mice

Blood pressure (BP) and heart rate (HR) are both controlled by the autonomic nervous system (ANS) and are closely intertwined due to reflex mechanisms. The baroreflex is a key homeostatic mechanism to counteract acute, short-term changes in arterial BP and to maintain BP in a relatively narrow physiological range. BP is sensed by baroreceptors located in the aortic arch and carotid sinus. When BP changes, signals are transmitted to the central nervous system and are then communicated to the parasympathetic and sympathetic branches of the autonomic nervous system to adjust HR. A rise in BP causes a reflex decrease in HR, a drop in BP causes a reflex increase in HR.
Baroreflex sensitivity (BRS) is the quantitative relationship between changes in arterial BP and corresponding changes in HR. Cardiovascular diseases are often associated with impaired baroreflex function. In various studies reduced BRS has been reported in e.g., heart failure, myocardial infarction, or coronary artery disease. 
Determination of BRS requires information from both BP and HR, which can be recorded simultaneously using telemetric devices. The surgical procedure is described beginning with the insertion of the pressure sensor into the left carotid artery and positioning of its tip in the aortic arch to monitor arterial pressure followed by the subcutaneous placement of the transmitter and ECG electrodes. We also describe postoperative intensive care and analgesic management. After a two-week period of post-surgery recovery long-term ECG and BP recordings are performed in conscious and unrestrained mice. Finally, we include examples of high-quality recordings and the analysis of spontaneous baroreceptor sensitivity using the sequence method.

The baroreflex is a heart-rate regulation mechanism by the autonomic nervous system in response to blood-pressure changes. We describe a surgical technique to implant telemetry transmitters for continuous and simultaneous measurement of electrocardiogram and blood pressure in mice. This can determine spontaneous baroreflex sensitivity, an important prognostic marker for cardiovascular disease.

Blood pressure (BP) and heart rate (HR) are both controlled by the autonomic nervous system (ANS) and are closely intertwined due to reflex mechanisms. ...

Long-Term Continuous Measurement of Renal Blood Flow in Conscious Rats

The kidneys play a crucial role in maintaining the homeostasis of body fluids. The regulation of renal blood flow (RBF) is essential to the vital functions of filtration and metabolism in kidney function. Many acute studies have been carried out in anesthetized animals to measure RBF under various conditions to determine mechanisms responsible for the regulation of kidney perfusion. However, for technical reasons, it has not been possible to measure RBF continuously (24 h/day) in unrestrained unanesthetized rats over prolonged periods. These methods allow the continuous determination of RBF over many weeks while also simultaneously recording blood pressure (BP) with implanted catheters (fluid-filled or by telemetry). RBF monitoring is carried out with rats placed in a circular servo-controlled rat cage that enables the unrestrained movement of the rat throughout the study. At the same time, the tangling of cables from the flow probe and arterial catheters is prevented. Rats are first instrumented with an ultrasonic flow probe placement on the left renal artery and an arterial catheter implanted in the right femoral artery. These are routed subcutaneously to the nape of the neck, and connected to the flowmeter and pressure transducer, respectively, to measure RBF and BP. Following surgical implantation, rats are immediately placed in the cage to recover for at least one week and stabilize the ultrasonic probe recordings. Urine collection is also feasible in this system. The surgical and post-surgical procedures for continuous monitoring are demonstrated in this protocol.

The present protocol describes a long-term continuous measurement of renal blood flow in conscious rats and simultaneously recording blood pressure with implanted catheters (fluid-filled or by telemetry).

The kidneys play a crucial role in maintaining the homeostasis of body fluids. The regulation of renal blood flow (RBF) is essential to the vital ...

Multiple Intravenous Bolus Dosing and Invasive Hemodynamic Assessment in a Hypoxia-Induced Mouse Pulmonary Artery Hypertension Model

Pulmonary arterial hypertension (PAH) is a progressive life-threatening disease, primarily affecting small pulmonary arterioles of the lung. Currently, there is no cure for PAH. It is important to discover new compounds that can be used to treat PAH. The mouse hypoxia-induced PAH model is a widely used model for PAH research. This model recapitulates human clinical manifestations of PAH Group 3 disease and is an important research tool to evaluate the effectiveness of new experimental therapies for PAH. Research using this model often requires the administration of compounds in mice. For a compound that needs to be given directly into the bloodstream, optimizing intravenous (IV) administration is a key part of the experimental procedures. Ideally, the IV injection system should permit multiple injections over a set time course. Although the mouse hypoxia-induced PAH model is very popular in many laboratories, it is technically challenging to perform multiple IV bolus dosing and invasive hemodynamic assessment in this model. In this protocol, we present step-by-step instructions on how to carry out multiple IV bolus dosing via mouse jugular vein and perform arterial and right ventricle catheterization for hemodynamic assessment in mouse hypoxia-induced PAH model.

This protocol provides a step-by-step procedure for executing multiple intravenous bolus dose administration and invasive hemodynamic monitoring in mice. Investigators can use this protocol for future therapeutic compound screening for pulmonary artery hypertension.

Pulmonary arterial hypertension (PAH) is a progressive life-threatening disease, primarily affecting small pulmonary arterioles of the lung. Currently, ...

Simple Continuous Glucose Monitoring in Freely Moving Mice

Mice are a common model organism used to study metabolic diseases such as diabetes mellitus. Glucose levels are typically measured by tail-bleeding, which requires handling the mice, causes stress, and does not provide data on freely behaving mice during the dark cycle. State-of-the-art continuous glucose measurement in mice requires inserting a probe into the aortic arch of the mouse, as well as a specialized telemetry system. This challenging and expensive method has not been adopted by most labs. Here, we present a simple protocol involving the utilization of commercially available continuous glucose monitors used by millions of patients to measure glucose continuously in mice as a part of basic research. The glucose-sensing probe is inserted into the subcutaneous space in the back of the mouse through a small incision to the skin and is held in place tightly using a couple of sutures. The device is sutured to the mouse skin to ensure it remains in place. The device can measure glucose levels for up to 2 weeks and sends the data to a nearby receiver without any need to handle the mice. Scripts for the basic data analysis of glucose levels recorded are provided. This method, from surgery to computational analysis, is cost-effective and potentially very useful in metabolic research.

Here, we describe a simple method to implant a commercial continuous glucose monitor designed for patients onto mice and provide the scripts to analyze the results.

Mice are a common model organism used to study metabolic diseases such as diabetes mellitus. Glucose levels are typically measured by tail-bleeding, which ...

Long-term Blood Pressure Measurement in Freely Moving Mice Using Telemetry

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Chapters in this video

Implantation of Radiotelemetry Transmitters Yielding Data on ECG, Heart Rate, Core Body Temperature and Activity in Free-moving Laboratory Mice

Measuring Blood Pressure in Mice using Volume Pressure Recording, a Tail-cuff Method

Monitoring of Systemic and Hepatic Hemodynamic Parameters in Mice

Intrauterine Telemetry to Measure Mouse Contractile Pressure In Vivo

Novel Approach for Simultaneous Recording of Renal Sympathetic Nerve Activity and Blood Pressure with Intravenous Infusion in Conscious, Unrestrained Mice.

Simultaneous Electrocardiography Recording and Invasive Blood Pressure Measurement in Rats

Implantation of Combined Telemetric ECG and Blood Pressure Transmitters to Determine Spontaneous Baroreflex Sensitivity in Conscious Mice

Long-Term Continuous Measurement of Renal Blood Flow in Conscious Rats

Multiple Intravenous Bolus Dosing and Invasive Hemodynamic Assessment in a Hypoxia-Induced Mouse Pulmonary Artery Hypertension Model

Simple Continuous Glucose Monitoring in Freely Moving Mice