A low cost tail-cuff method for the estimation of mean arterial pressure in conscious rats

Methods utilized in the determination of systolic tail-cuff pressure (TCP) in awake rats are aimed at detecting the earliest possible tail pulsations as the cuff is deflated. In the method described in this study, a small, inexpensive electret microphone is used as a sensor, connected to the tail by a piece of rubber tubing. This design provides selective attenuation of tail pulsations appearing as the cuff is deflated between systolic and mean arterial pressures. In this manner, tail pulsations are detected only when the cuff pressure is lowered below the mean arterial pressure, thus providing an estimation of the latter. The method was validated in prewarmed awake normotensive and hypertensive rats by simultaneous comparison with directly measured systolic and mean pressures or with a conventional tail-cuff method. Validation studies were also carried out in anesthetized rats undergoing wide variations of arterial pressure by parenteral injections of norepinephrine or nitroprusside. Close agreement was observed between TCP determined with this method and directly obtained mean, but not systolic, pressure. Thus, the method described in this study constitutes an inexpensive alternative to conventional tail-cuff methods. Mean, rather than systolic pressure, appears to be evaluated in the conscious rat by employing this method.