A Novel Freely Moving Animal Based Blood Pressure, ECG, and Dual Body Temperature Telemetry System for Group Housed Mice in Social Context

Abstract

Traditional rodent blood pressure (BP) monitoring required single housing, a known stressor for rodents. We developed a microprocessor based long range wireless telemetry system based on the Stellar™ technology with internal memory that allows rodents to live in groups, interact, exercise and be housed in large enriched environments. BP or ECG is recorded with a solid‐state sensor along with core temperature and 3D activity. Heart rate was derived from BP and/or ECG in the Biopac AcqKnowledge 4.4.1 software.It is well established that rodent behavior is strongly influenced by social interaction. Moreover, spontaneous hierarchies develop in group housed animals and cardiovascular parameters such as heart rate and blood pressure reflect these conditions. Since animal experimentation most notably in neuroscience and behavior studies gravitate towards group housed colonies also for sake of animal welfare new technologies are needed to allow traditional measurements to be done in these new more refined research environments. Moreover, in the case of metabolic studies where animals tend to huddle in groups when they sleep, a similar adaptive behavior needs to be taken into account when calculating energy expenditure in nutritional and diabetes/obesity studies.In order to objectively validate this system we implanted 5 male mice of ca. 20 g. After 8 days of recovery the animals entered an exploratory study to compare fidelity and accuracy of the novel solid‐state microtipped pressure lead (450 micron) based wireless implant and BP was recorded for 10s every 15 min for 4 weeks sampled at 200Hz. The BP responses were compared to a control group of 5 animals implanted with a similar conventional implant from a competitor sampled for 5s every minute at 500Hz equiped with a fluid‐filled catheter. Mean dark phase arterial pressures (MAP) at 14 days in the Stellar group were 134 ± 31 mmHg at a Heart rate (HR) of 544 ± 67 BPM versus 127 ± 9 mmHg at a HR of 545 ± 24 in the control group. Further studies on core body temperature are progressing and will be presented.We conclude that there are no significant differences in quantitative blood pressure responses between the Stellar digital telemetry device versus a leading analog competing device while being able to record from up to 5 different animals without cross‐talk. We also conclude that the short scheduled recordings used for the Stellar device produced equivalent MAP values at better (less) data economy while significantly prolonging implant battery life, thus extending the possible study length as needed for behavioral monitoring in group housed animals to several months.