Assessing cardiovascular and autonomic function in the mouse
Assessing cardiovascular and autonomic function in the mouse
Assessing cardiovascular and autonomic function in the mouse
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<strong>Assess<strong>in</strong>g</strong> <strong>cardiovascular</strong> <strong>and</strong><br />
<strong>autonomic</strong> <strong>function</strong> <strong>in</strong> <strong>the</strong> <strong>mouse</strong><br />
Presenter: Col<strong>in</strong> N. Young, Ph.D.<br />
Dept. of Biomedical Sciences, College of Veter<strong>in</strong>ary Medic<strong>in</strong>e,<br />
Cornell University, Ithaca, NY<br />
Discussant: Rob<strong>in</strong> L. Davisson, Ph.D.<br />
Dept. of Biomedical Sciences, College of Veter<strong>in</strong>ary Medic<strong>in</strong>e,<br />
Cornell University, Ithaca, NY<br />
Dept. of Cell <strong>and</strong> Developmental Biology, Weill Cornell Medical<br />
College, New York, NY
Autonomic control of arterial blood pressure<br />
Blood Pressure<br />
The unique susceptibility of mice to<br />
genetic manipulation makes this<br />
species an attractive model to def<strong>in</strong>e<br />
<strong>the</strong> molecular <strong>and</strong> cellular<br />
mechanisms essential to<br />
neuro<strong>cardiovascular</strong> regulation<br />
Paraphrased from Ma et al, Cl<strong>in</strong> Exp Pharm Physiol 2003
How do we measure blood<br />
pressure <strong>in</strong> a <strong>mouse</strong>?
Indirect Method: Tail Cuff Plethysmography<br />
Sample Manufacturers:<br />
Restra<strong>in</strong>er Occlusion Cuff Sensor<br />
• Images from Kent Scientific Corp. (www.kentscientific.com)<br />
• Columbus Instruments (www.col<strong>in</strong>st.com)<br />
• Stoelt<strong>in</strong>g (www.stoelt<strong>in</strong>gco.com)<br />
• volume pressure<br />
• photoplethysmography<br />
• piezoplethysmography
Indirect Method: Tail Cuff Plethysmography<br />
Occlusion Cuff<br />
Pressure (mmHg)<br />
Tail Pulse (mV)<br />
PROS:<br />
• Fairly <strong>in</strong>expensive (
Direct Methods: Implanted arterial ca<strong>the</strong>ters & radiotelemetry<br />
Implanted arterial ca<strong>the</strong>ters<br />
• Fluid-filled ca<strong>the</strong>ter placed <strong>in</strong> a major artery (i.e. femoral)<br />
• Ca<strong>the</strong>ter exteriorized, connected to a pressure transducer,<br />
amplifier <strong>and</strong> record<strong>in</strong>g system<br />
PROS:<br />
• Can obta<strong>in</strong> long-term record<strong>in</strong>gs of BP<br />
• Fairly affordable<br />
CONS:<br />
• Requires surgical expertise<br />
• Ma<strong>in</strong>ta<strong>in</strong><strong>in</strong>g a patent arterial ca<strong>the</strong>ter for an extended period of<br />
time can be difficult<br />
Radiotelemetry
www.datasci.com<br />
Direct Methods: Radiotelemetry<br />
• Weight: 1.2 grams<br />
• Volume: 1.1 cc<br />
Magnetic<br />
Switch<br />
Pressure<br />
Transducer<br />
Fluid-filled ca<strong>the</strong>ter<br />
Electronics<br />
Antenna<br />
Sens<strong>in</strong>g region<br />
Battery<br />
(life: 1.5 months)
Thoracic aorta implantation of radiotelemeter<br />
Butz & Davisson, Physiol Gen. 2001<br />
Carotid Artery<br />
Thoracic Aorta<br />
Butz & Davisson,<br />
Physiol Gen. 2001
Direct Methods: Radiotelemetry data collection equipment<br />
Receiver
120<br />
Arterial<br />
Blood Pressure<br />
(mmHg)<br />
80<br />
Blood Pressure (mmHg)<br />
1 sec<br />
140<br />
120<br />
100<br />
80<br />
Direct Methods: Radiotelemetry<br />
Diurnal Record<strong>in</strong>gs<br />
<br />
140<br />
Time<br />
Recovery time is essential<br />
* p
Implant Radiotelemeters<br />
Radiotelemetry for chronic record<strong>in</strong>gs of BP<br />
7 days 3 days<br />
Recovery<br />
Osmotic pumps with Angiotens<strong>in</strong> II<br />
Basel<strong>in</strong>e Record<strong>in</strong>gs Chronic Record<strong>in</strong>g
Radiotelemetry for evaluat<strong>in</strong>g transgenic <strong>mouse</strong> models<br />
Transgenic mice carry<strong>in</strong>g both <strong>the</strong> HREN (R + ) <strong>and</strong> HAGT (A + )<br />
(Merrill et al, JCI 1996; Sigmund et al, Circ Res 1992; Yang et al, J Biol Chem 1994)<br />
Mean Arterial<br />
Blood Pressure (mmHg)<br />
160<br />
140<br />
120<br />
100<br />
<br />
Time<br />
R + A +<br />
Control
Radiotelemetry<br />
PROS<br />
• Long-term cont<strong>in</strong>uous record<strong>in</strong>gs of BP<br />
• Wireless<br />
• Can simultaneously obta<strong>in</strong> measures of:<br />
activity, biotentials (i.e. ECG) <strong>and</strong> body<br />
temperature<br />
Fluid-filled ca<strong>the</strong>ters<br />
Tail Cuff<br />
• Long-term cont<strong>in</strong>uous record<strong>in</strong>gs of BP<br />
• Fairly affordable<br />
• Useful for screen<strong>in</strong>g large numbers of<br />
animals<br />
• Cheap / easy<br />
CONS<br />
• Cost<br />
• Initial system to measure<br />
simultaneously <strong>in</strong> 32 mice<br />
~$100,000<br />
• Telemeter refurbishment<br />
~$400<br />
• Requires surgical expertise<br />
• Ma<strong>in</strong>ta<strong>in</strong><strong>in</strong>g patent l<strong>in</strong>e can be<br />
difficult<br />
• Requires surgical expertise<br />
• Very stressful on <strong>the</strong> <strong>mouse</strong><br />
• Only measures BP dur<strong>in</strong>g a few<br />
discrete cardiac cycles
Autonomic control<br />
Sympa<strong>the</strong>tic Parasympa<strong>the</strong>tic<br />
Heart Rate<br />
Blood Pressure
Indirect Methods to assess <strong>autonomic</strong> <strong>function</strong><br />
Plasma / ur<strong>in</strong>e estimates<br />
• Norep<strong>in</strong>ephr<strong>in</strong>e, ep<strong>in</strong>ephr<strong>in</strong>e or o<strong>the</strong>r metabolite measurements<br />
• Provides a “global” measure of sympa<strong>the</strong>tic nervous system activity<br />
Pharmacological<br />
• Measure hemodynamic responses to pharmacological blockade of<br />
parasympa<strong>the</strong>tic <strong>and</strong> sympa<strong>the</strong>tic tone (systemic or <strong>in</strong>traperitoneal)<br />
(+)<br />
Δ Heart Rate<br />
(-)<br />
Parasympa<strong>the</strong>tic<br />
Muscar<strong>in</strong>ic blocker<br />
(i.e. atrop<strong>in</strong>e)<br />
β-blocker<br />
(i.e. propranolol)<br />
Sympa<strong>the</strong>tic
Indirect Methods to assess <strong>autonomic</strong> <strong>function</strong><br />
Pharmacological (cont.)<br />
• Sympa<strong>the</strong>tic restra<strong>in</strong>t of <strong>the</strong> vasculature:<br />
• α-adrenergic blockade (i.e. prazos<strong>in</strong>)<br />
• Ganglionic blockade (i.e. hexamethonium)<br />
Mouse model of myocardial <strong>in</strong>farction<br />
• Ligation of left anterior descend<strong>in</strong>g artery<br />
or sham surgery<br />
• BP measured us<strong>in</strong>g radiotelemetry<br />
• Hexamethonium 5 mg/kg i.p.<br />
Sham MI<br />
Adapted from Infanger et al, Circ Res. 2010
Spontaneous fluctuations <strong>in</strong> <strong>cardiovascular</strong> parameters are<br />
related to <strong>autonomic</strong> <strong>function</strong><br />
Arterial Blood<br />
Pressure (mmHg)<br />
Very Low Frequency (VLF)<br />
Low Frequency (LF)<br />
High Frequency (HF)<br />
Cl<strong>in</strong>ical Significance<br />
• Increased blood pressure variability is l<strong>in</strong>ked to<br />
target organ damage<br />
• Decreased heart rate variability is related to<br />
<strong>cardiovascular</strong> mortality<br />
Rationale: Parasympa<strong>the</strong>tic <strong>and</strong> sympa<strong>the</strong>tic components contribute to<br />
variability <strong>in</strong> HR <strong>and</strong> BP at different frequencies
Indirect Methods to assess <strong>autonomic</strong> <strong>function</strong><br />
Power Spectral Analysis<br />
• Ma<strong>the</strong>matical <strong>in</strong>vestigation of <strong>the</strong> <strong>in</strong>dividual frequency ranges of blood<br />
pressure <strong>and</strong> heart rate (pulse <strong>in</strong>terval)<br />
• Custom written software: (Hemolab, www.haraldstauss.com)<br />
Which frequency b<strong>and</strong>s do <strong>the</strong><br />
sympa<strong>the</strong>tic & parasympa<strong>the</strong>tic<br />
nervous systems <strong>in</strong>fluence?
Power Spectral Analysis<br />
Heart Rate Variability<br />
Blood Pressure Variability – Sympa<strong>the</strong>tic Influence<br />
Sympa<strong>the</strong>tic Influence Parasympa<strong>the</strong>tic Influence<br />
Very Low Frequency (VLF)<br />
Low Frequency (LF)<br />
High Frequency (HF)
Catecholam<strong>in</strong>e<br />
measurements<br />
Heart Rate<br />
Circulat<strong>in</strong>g / Hormonal<br />
Factors<br />
Pharmacological / Ganglionic<br />
Blockade<br />
Blood Pressure<br />
Direct Record<strong>in</strong>gs of Nerve<br />
Activity<br />
Circulat<strong>in</strong>g catecholam<strong>in</strong>e levels are determ<strong>in</strong>ed by<br />
release, reuptake <strong>and</strong> degradation<br />
Local Vascular<br />
Influences<br />
Power Spectral Analysis
Direct record<strong>in</strong>gs of efferent nerve activity<br />
Sympa<strong>the</strong>tic record<strong>in</strong>gs<br />
• Detailed methodology by Dr. Sean Stocker <strong>in</strong> this workshop<br />
• Anes<strong>the</strong>tized record<strong>in</strong>gs of cardiac, lumbar, renal, brown fat <strong>and</strong> white<br />
fat sympa<strong>the</strong>tic nerve activity have been obta<strong>in</strong>ed <strong>in</strong> <strong>the</strong> <strong>mouse</strong>.<br />
mV<br />
K. Rahmouni, U. Iowa<br />
Basel<strong>in</strong>e renal sympa<strong>the</strong>tic<br />
nerve activity<br />
4 s<br />
Renal sympa<strong>the</strong>tic nerve activity follow<strong>in</strong>g<br />
<strong>in</strong>tracerebroventricular lept<strong>in</strong> (60ug)
• Easy to obta<strong>in</strong><br />
• Inexpensive<br />
PROS<br />
Plasma/Ur<strong>in</strong>e Measurements<br />
Pharmacological<br />
• Can be done <strong>in</strong> a conscious <strong>mouse</strong><br />
toge<strong>the</strong>r with <strong>the</strong> use of radiotelemetry<br />
• Fairly easy to perform<br />
Spectral Analysis<br />
• Can be done <strong>in</strong> a conscious <strong>mouse</strong><br />
toge<strong>the</strong>r with <strong>the</strong> use of radiotelemetry<br />
• Easy to perform with <strong>the</strong> appropriate<br />
software<br />
Sympa<strong>the</strong>tic Nerve Record<strong>in</strong>gs<br />
• Direct record<strong>in</strong>g of efferent sympa<strong>the</strong>tic<br />
nerve activity<br />
CONS / CAVEATS<br />
• “Global” measurement<br />
• “Global” measurement<br />
• Hemodynamic responses are also<br />
<strong>in</strong>fluenced by hormonal <strong>and</strong> local<br />
organ responsiveness<br />
• Hemodynamic responses are also<br />
<strong>in</strong>fluenced by hormonal <strong>and</strong> local<br />
organ responsiveness<br />
• Although commonly used, <strong>the</strong>re are<br />
limited studies <strong>in</strong> <strong>the</strong> <strong>mouse</strong><br />
validat<strong>in</strong>g this technique<br />
• Does not reflect <strong>the</strong> end organ<br />
responsiveness<br />
• To date, limited to anes<strong>the</strong>tized<br />
preparations <strong>in</strong> <strong>the</strong> <strong>mouse</strong>
<strong>Assess<strong>in</strong>g</strong> <strong>cardiovascular</strong> <strong>and</strong> <strong>autonomic</strong> <strong>function</strong> <strong>in</strong><br />
<strong>the</strong> <strong>mouse</strong><br />
Arterial Blood Pressure<br />
Indirect<br />
• Tail Cuff<br />
Direct<br />
• Fluid-filled ca<strong>the</strong>ters<br />
• Radiotelemetry<br />
Autonomic Nervous System<br />
Indirect<br />
• Plasma / ur<strong>in</strong>e measurements<br />
• Pharmacological / ganglionic blockade<br />
• Power spectral analysis<br />
Direct<br />
• Sympa<strong>the</strong>tic nerve activity
Acknowledgments<br />
Cornell University<br />
Rob<strong>in</strong> L. Davisson, Ph.D.<br />
Scott Butler<br />
University of Iowa<br />
Allyn L. Mark, M.D.<br />
Kamal Rahmouni, Ph.D.<br />
Donald Morgan, Ph.D.<br />
University of Missouri<br />
Cathar<strong>in</strong>e G. Clark
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