Development of an analysis system for 24-hour blood pressure and heart rate variability in the rat

We have developed a system to evaluate 24-h changes of heart rate (HR) and blood pressure variability (BPV) in free moving rat. As a sensor to monitor electrocardiogram, we used the telemetry system. Analog data were sent to an analog to digital converter directly. The data were digitized at a sampling frequency of 1250 Hz and digitally stored on a computer. RR-intervals (difference of successive RR in electrocardiogram) were calculated using custom designed programs. Circadian change of the blood pressure and heart rate variability were calculated. We suggest that the system is a powerful tool in the evaluation of circadian changes of hemodynamics and autonomic nervous function in free moving rats.