Long-term telemetric recording of arterial pressure and heart rate in mice fed basal and high NaCl diets.

Research examining the control of arterial pressure in mice has primarily relied on tail-cuff plethysmography and, more recently, on tethered arterial catheters. In contrast, the radiotelemetry method has largely become the "gold standard" for long-term monitoring of arterial pressure and heart rate in rats. Whereas smaller telemetry probes have recently been developed, no published studies have used radiotelemetric monitoring of arterial pressure in mice, largely because of a relatively low success rate in small mice (ie, <30 g body weight). We report on the development of a protocol for the use of these probes to continuously monitor arterial pressure and heart rate in mice as small as 19 g body weight. To test the accuracy and reliability of this method, adult C57/BL6 mice were monitored for 3 weeks during exposure to a basal followed by a high NaCl diet. The results demonstrate that carotid and aortic placements of the telemetry probe provide equally accurate monitoring of arterial pressure and heart rate, but the carotid placement has a much greater rate of success. Exposure to a high NaCl diet increases both the amplitude of the arterial pressure rhythm (+ 6.0+/-0.6 mm Hg, approximately 32%) and the average mean arterial pressure (+ 8.6+/-1.1 mm Hg, approximately 8%), as would be predicted from previous studies in NaCl-resistant rats. Thus, the data demonstrate that telemetric recording of long-term arterial pressure and heart rate provides a powerful tool with which to define the mechanisms of cardiovascular control in mice.