Cardiac output and peripheral resistance of swim-trained rats under urethan anesthesia.

Several circulatory variables were determined in control and swim-trained white rats under urethan anesthesia. Trained animals exhibited significantly lower heart rate and cardiac index and significantly higher peripheral resistance than control animals. Blood pressure, systolic index and left ventricular work output were not statistically different in the two groups. These results suggest an alteration of resting cardiovascular regulation in trained animals. Beta adrenergic mechanisms are suppressed by increased parasympathetic tone, and the resting circulatory balance is maintained mainly by increased alfa adrenergic mechanisms.