The ability to monitor and record precise blood pressure fluctuations in research animals is vital to research for human hypertension. Direct measurement of blood pressure via implantable radio telemetry devices is the preferred method for automatic collection of chronic, continuous blood pressure data. Two surgical techniques are described for instrumenting the two most commonly used laboratory rodent species with radiotelemetry devices. The basic rat procedure involves advancing a blood pressure catheter into the abdominal aorta and placing a radio transmitting device in the peritoneal cavity. The mouse technique involves advancing a thin, flexible catheter from the left carotid artery into the aortic arch and placing the telemetry device under the skin along the animal's flank. Both procedures yield a chronically instrumented model to provide accurate blood pressure data from an unrestrained animal in its home cage.

Original ArticleCurrent options for obtaining glucose measurements in animal studies are limited in terms of the quality and quantity of data available. Glucometers and test strips are perhaps most commonly used. These require tail tip amputation or venipuncture, are stressful to the animal and handler, and often result in high measurement variability due to factors including measurement error, variability in the sampling process, and physiologic stress response. The use of arterial or venous cannulae can help facilitate sample collection and minimize subject and handler stress, but these require routine maintenance with blood loss and offer limited chronic patency. Options for continuous sampling for periods of a few days to 2 weeks include tethered automated blood sampling and some limited use of human continuous glucose monitors (CGMs), which have limited longevity and accuracy.Amperometric electrochemical sensors have been available for over 30 years and originated with the Clark electrode.2,3 The basic principle involves application of a reference voltage to an electrode (typically a noble metal such as platinum) to oxidize a target chemical and measure the current resulting from electron transfer to the electrode. The current is proportional to the availability of the target chemical.Many glucose sensors available today or under development are intended for use in humans with the sensor placed subcutaneously to measure glucose in interstitial fluid. These sensors are targeted at the management of diabetes where patient safety and minimal invasiveness are critical factors, thus precluding placement directly in the blood. These sensors are subject to notable biofouling due to foreign body immune response and are typically overgrown with a fibrous sheath in a matter of days. Background: Chronic continuous glucose monitoring options for animal research have been very limited due to various technical and biological challenges. We provide an evaluation of a novel telemetry device for continuous monitoring of temperature, activity, and plasma glucose levels in the arterial blood of rats for up to 2 months. Methods:In vivo testing in rats including oral glucose tolerance tests (OGTTs) and intraperitoneal glucose tolerance tests (IPGTTs) and ex vivo waterbath testing were performed to evaluate acute and chronic sensor performance. Animal studies were in accordance with the guidelines for the care and use of laboratory animals and approved by the corresponding animal care and use committees (Data Sciences International, Eli Lilly). Results:Results demonstrated the ability to record continuous measurements for 75 days or longer. Bench testing demonstrated a high degree of linearity over a range of 20-850 mg/dL with R 2 = .998 for linear fit and .999 for second order fit (n = 8 sensors). Evaluation of 6 rats over 28 days with 52 daily and OGTT test strip measurements each resulted in mean error of 3.8% and mean absolute relative difference of 16.6%. Conclusions:This device provides significant advantages in the qualit...

Euthanasia is a necessary component in research and must be conducted humanely. Currently, regulated CO2 exposure in conscious rats is acceptable, but data are divided on whether CO2 alone is more distressing than anesthesia prior to CO2. To evaluate distress in rats, we compared physiologic responses to CO2 euthanasia with and without isoflurane preanesthesia. Male Sprague–Dawley rats were implanted with telemetry devices to measure mean arterial pressure (MAP), heart rate (HR), and blood glucose. Animals recovered for 2 wk and were then exposed to either 5% isoflurane (n = 6) or 100% CO2(n = 7; calculated 30% chamber volume/min displacement) in their home cages to induce loss of consciousness. Euthanasia was then completed with CO2 in both groups. MAP and HR increased when the gas delivery lids were placed on the home cages of both groups. Both MAP and HR gradually decreased with isoflurane exposure. MAP increased and HR decreased with CO2 exposure. Glucose levels remained stable throughout the procedure, except for a small drop in conscious animals initially exposed to 100% CO2. These data suggest that both gases affect the measured parameters in a similar manner, andthat environmental factors, such as gas delivery lid placement, also change these measurements.

Radiotelemetry allows for real-time remote monitoring of biological parameters in freely moving laboratory animals. The HD-X11 transmitter is a novel telemetry device that enables simultaneous collection of body temperature, activity, blood pressure, electrocardiogram (ECG), and other biopotentials in small animal models. Previously, researchers could only collect either blood pressure or ECG parameters; prioritizing the signal of most interest or increasing the number of animals on study to capture both signals at one time. This new device eliminates the need for separate animal groups for assorted measurements and allows for a more complete cardiovascular assessment. Evaluation of the transmitter from both surgical and data collection perspectives indicates that the HD-X11 transmitter can be a useful tool to researchers in a wide range of scientific and medical fields.