Activation of Bradykinin‐Sensitive Pericardial Afferents Increases Systemic Venous Tone and Cardiac Output

Abstract

The venous system plays a critical role in blood pressure regulation by controlling venous return, cardiac filling, and cardiac output. Sympathetic drive is a major controller of venous function. However, outside of the arterial baroreflex, the mechanisms that regulate sympathetic drive to veins remain poorly defined in both physiological and disease conditions. The heart itself has an important sensory function via a variety of cardiac receptors that modulate cardiovascular function by neural and humoral reflexes. Bradykinin‐sensitive sympathetic afferent nerves from the heart can trigger marked increases in efferent sympathetic nerve activity to some cardiovascular target organs such as the kidney. This work tested the hypothesis that the activation of bradykinin‐sensitive cardiac afferents increases venous tone and cardiac output.Sprague Dawley rats were anesthetized with a cocktail of alpha chloralose (80 mg/kg) and urethane (800 mg/kg). Catheters were placed in the femoral artery and vein to record arterial and venous blood pressures. A PE 10 catheter was placed in the pericardial space for the injection of bradykinin (BK), an agent known to stimulate cardiac sympathetic afferents. In some rats, a balloon tipped catheter was placed in the right atrium to allow transient arrest of cardiac pumping for the estimation of mean circulatory filling pressure (MCFP), an estimate of systemic venous tone. In other rats, an electromagnetic flow probe was placed on the aortic arch for the direct measurement of cardiac output.In rats instrumented for the measurement of venous tone, pericardial injections of BK (0.4–20 μg/kg) were associated with dose‐related increases in mean arterial pressure (9±6 to 27±6 mm Hg) and MCFP (0.6±0.2 to 1.6±0.4 mm Hg). These responses were largely attenuated after ganglionic blockade. In rats instrumented for the measurement of cardiac output, pericardial injection of BK (10 μg/kg) increased mean arterial pressure (23±3 mm Hg) and cardiac output (16±2 ml/min).We interpret these data to indicate that activation of bradykinin‐sensitive pericardial afferents increases venous tone sufficiently to increase cardiac filling and cardiac output.Support or Funding InformationSupported by NIH R01 HL136741‐01 and the Basic Biomedical Sciences program of the Sanford School of Medicine, University of South Dakota.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.