Lecture Seven: Telemetry

Question 1

What is a pivotal in the measurement of blood pressure in the laboratory?

Answer 1

Telemetry

A unit that is surgically implanted into the belly of the rat that is linked to wires that connect to the major arteries to record blood pressure. The inductive baseplate then can maintain charge and record the blood pressure through wireless transmission.

Question 2

What are some short facts on hypertension;

Answer 2

• 1 in 5 people have hypertension.
• The higher the blood pressure, the greater the cardiovascular risk.
• The longer the duration of hypertension, the greater the cardiovascular risk.

Question 3

Consequences of hypertension;

Answer 3

• Heart Attack
• Stroke
• Renal Failure
• Heart Failure

Question 4

What is the relationship between risk of cardiovascular death and hypertension?

Answer 4

Somewhat linear

120mmHg ~1X
160mmHg ~2X
180mmHg ~3-4X

Question 5

How does the sympathetic nerve activity relate to disease?

Answer 5

Increases down this list

• Control
• Hypertension
• Obesity
• Congestive Heart Failure
• CHF + O
• CHFOH

Chronic sympathetic hyperactivity = bad
Acute is fine i.e flight or fight

Question 6

What is noted about SNA?

Answer 6

Its burst activity

Question 7

What is an old way to measure SNA?

Answer 7

Microneurography

• Impale peroneal nerve with tungsten carbide electrode
• Permits direct recording of nerve activity

Question 8

Why dont we measure in human patients all the time then?

Answer 8

• Only short term measurements possible (minutes to an hour or two)
• Difficult to compare between subjects, or even within one subject over time (variability)
• Can be hard to recruit patients –procedure invasive and slightly painful
• High technical difficulty

Question 9

What is the best model and why?

Answer 9

•Variety of cardiovascular disease modele.g. SHR, SHR-SP, Dahl-SS etc
.•Easy for surgical manipulation compared to mice
•Economical
•Easily bred, short gestation period

Question 10

What was the problem with tethered rats?

Answer 10

•Definitive data can only come from conscious, unrestrained animals

.•Long term measurement of signals is required for a full understanding of chronic disease mechanisms disease.

Question 11

What were the tethered methods of measuring blood pressure in rats?

Answer 11

1. Tail-cuff methodTo Pressure Transducer
2. Catheter implantation & tethering
3. Radio-telemetry

Question 12

What is the problem with the tail cut off measurement?

Answer 12

White coat hypertension

Question 13

How does the ratiotelemetry measure blood pressure;

Answer 13

Ring electrodes around the renal nerve

Question 14

What is a practical consideration for rat mdoels?

Answer 14

You have to wait around three weeks for blood pressure to return to normal post surgery

Question 15

What can be done to normalise RSNA?

Answer 15

• Nasopharyngeal activation (nicotene) 100%
• Home cage ~8%
• Ganglionic Blockade (0%)

Question 16

Whats role does chemoreceptors in SNA?

Answer 16

Peripheral Chemoreceptor Afferent Drive is Pro-Sympatho-Excitatory in SH Rats

Ablation of carotid bodies drops SNA (56%)!!!!!!!!!!

Question 17

What is the function of ablating the SNA

Answer 17

could be a potential treatment in disease states with heightened SNA (as this causes further disease)

Question 18

What are the conclusions of radio telemetry?

Answer 18

• Radio-telemetry provides a non-invasive way of recording arterial pressure remotely from conscious rats (and mice) without stress
• Radio-telemetry is an ideal technique for long term (e.g. months) recording of arterial pressure.
• A thorough analysis of cardiovascular sympathetic and parasympathetic activities can be evaluated by performing power spectral analysis of frequencies from the pulsatile arterial pressure signal.