Radio-telemetry provides an alternative means of obtaining physiological measurements from conscious, freely moving laboratory animals, without introducing stress artefacts. For researchers, especially in the fields of pharmacology and toxicology, the technique may provide a valuable tool for predicting the effectiveness and safety of new compounds in humans.

Traditionally, a variety of techniques has been employed to obtain physiological measurements in the laboratory. With the exception of studies on anaesthetics and certain other types of experiments, it is generally assumed that the quality of such measurements are superior when collected from conscious animals, since they best represent the normal state of the animal and are most predictive of the results that would be achieved in humans. When monitoring conscious animals, it is possible to use invasive methods (e.g sensors, electrodes) or non-invasive methods (e.g. surface electrodes for monitoring an electrocardiogram (ECG) and tail cuffs for monitoring blood pressure). Indwelling sensors for monitoring flow and pressure are usually more accurate and more reliable than non-invasive methods. When using indwelling catheters, sensors or electrodes, there are several options for accessing the information from the sensor and forwarding it to a recording system. The advantages and disadvantages of each of these will be summarized.

Although wireless radio-telemetry technology for monitoring laboratory animals has existed for some time, it has only been in the last ten years that affordable, reliable and easy-to-use commercial products have been readily available for monitoring a variety of signals. This has resulted in a significant increase in the use of implantable radio-telemetry in biomedical research. The advantages of implantable wireless telemetry transmitters include: (1) providing a humane method for monitoring conscious, freely moving laboratory animals; (2) eliminating stress related to the use of restraints, which can alleviate a potential source of experimental artefact and inter-animal variability; (3) reducing animal use by 70% in single studies, and by more than 90% in multiple studies; and (4) allowing 24-hour data collection via computer, for days, weeks or months, without any special animal care.

However, the weight and volume of the implanted intra-abdominal transmitter may cause discomfort, and it was recently found that the wellbeing of mice is compromised during the first week following an intraperitoneal transmitter implantation. Despite this, when body weight has been normalized after fourteen days, the mice seem to have recovered completely and cope very well with the weight of the implanted transmitter. Long-term measurements of physiological parameters (e.g. electrocardiogram, heart rate, body temperature, blood pressure) in freely moving laboratory animals with radio-telemetry techniques are nowadays a valuable tool in our university, and are used in a range of pharmacological, toxicological, physiological and behavioral studies. The application possibilities and benefits of long-term measurements of physiological parameters in small laboratory animals will be presented, based on recent results.

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