Hemodynamic effects of carvedilol infusion and the contribution of the sympathetic nervous system in rats with heart failure

We investigated the contribution of the sympathetic nervous system ( SNS) in maintaining the blood pressure and in regulating the cardiac function during and after carvedilol administration in rats with heart failure ( group F). Left ventricular end- diastolic pressure, percent functional shortening, and rates of intraventricular pressure rise were significantly changed by carvedilol infusion as compared with the basal values in group N ( normal rats), but not in group F. The left ventricular end- diastolic pressure was elevated, corresponding to the enhancement of the plasma norepinephrine ( NE) concentration caused by carvedilol infusion, in group N. The enhancement of the plasma NE concentration induced by carvedilol administration in group F was higher than that in group N. The value for the maximal hypertensive effect of NE intravenous infusion ( E (max)) was decreased, and the plasma NE concentration at half- maximal effect ( EC50) was increased in group F as compared with the values in group N. These results indicate that the SNS ( presynaptic) activity is increased and that the SNS receptor sensitivity in the cardiovascular regulation system is decreased in heart failure. Copyright (C) 2004 S. Karger AG, Basel.