**1. Introduction**

182 Modern Telemetry

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Telemetry is a state-of-the-art method of monitoring physiological functions in awake and freely moving laboratory animals, while minimizing stress artefacts. Currently, telemetry systems are employed for measurements of blood pressure, heart rate, blood flow, electrocardiogram, respiratory rate, sympathetic nerve activity, body temperature and many other biological signals in a wide range of animal species including rats, mice, dogs, rabbits, gerbils, hamsters, monkeys, guinea pigs and pigs (Kramer et al., 2001; Butz & Davisson, 2001; Galvin et al., 2006; Moons et al., 2007; Hess et al., 2007; Shaw et al., 2007; Greene et al., 2008). Although telemetry technology has existed for at least 50 years, it has only been in the last decade or so that affordable, reliable, and user friendly commercial products have been available for monitoring physiological signals in the laboratory setting. In particular, the use of telemetry for measuring blood pressure in mice and rats has aided researchers in discovering fundamental mechanisms involved in the physiology and pathophysiology of cardiovascular diseases such as hypertension, heart failure and pre-eclampsia (Kramer & Kinter, 2003; Zimmerman et al., 2004; Hoffman et al., 2008, Burmeister et al., 2011). Moreover, drug discovery for treating hypertension has significantly benefited from telemetry since it allows for drug effects to be investigated chronically and longitudinally. In the first part of this chapter, we will discuss the significant contributions of telemetry towards advancing the field of cardiovascular physiology/pathophysiology, emphasizing chronic studies using several experimental models of hypertension. In the second part, we will discuss the benefits of using telemetry in regards to animal welfare and some strategies to refine the telemetry technique in order to reduce the cost and the number of animals used in experiments while improving animal welfare.
