Chronic L-name and blood pressure in conscious mice

In the present experiments we developed a technique which enables the daily measurement of arterial pressure and continuous intravenous infusion of fluids to conscious mice for periods up to 3 weeks. Swiss-Webster mice (32-41g) were anesthetized and the femoral artery and vein were catheterized. The catheters were tunneled subcutaneously and exteriorized in a lightweight spring attached to an infusion swivel at the top of the cage. Following a 5-7 day recovery period from surgery, mean arterial pressure (MAP) and heart rate (HR) averaged 117±4 mmHg and 602±29 beats/min in unrestrained mice on a 1.0% NaCl diet (n=6). MAP was not different in a separate group of restrained mice (119±4 mmHg, n=5), though HR was significantly elevated (709±22 beats/min). Chronic L-NAME infusion (8.6 mg/kg/day, iv) to the unrestrained mice significantly increased MAP to 131±4 mmHg without altering HR after 5 days. MAP returned to control levels by the first post-control day. Pulse pressure was unaltered from control (17±2 mmHg) throughout the protocol, demonstrating catheter patency. These experiments illustrate the sensitivity of MAP in mice to chronic nitric oxide inhibition and the feasibility of long-term infusion and blood pressure measurements in conscious mice.