Overall open-loop gain of rapidly acting arterial pressure control system in rabbits.

We estimated the overall open-loop gain of the rapidly acting arterial pressure control system without surgically or pharmacologically opening the reflex loop in rabbits. Animals anesthetized by intravenous injection of Nembutal (27.5 mg X kg-1 body weight) and heparinized were bled by 2 ml X kg-1 body weight within 1-2 s through a catheter inserted into the aortic arch. Arterial pressure change after the quick mild hemorrhage was monitored via a catheter placed in the right subclavian artery for more than 2 min. The overall open-loop gain of the lumped arterial pressure control system determined from the mean arterial pressure response to the hemorrhage was 7.3. It was almost constant over the range between 12.9 and 22.2 kPa systemic pressure.