Sympathetic afferent nerve activity of right heart origin

Six mongrel dogs anesthetized with sodium pentobarbital and paralyzed with gallamine triethiodide were studied on total cardiopulmonary bypass. This study verified the existence of right heart mechanoreceptors whose afferent nerves traverse the upper thoracic white rami communicantes. these mechanoreceptors were studied by observing changes in average maximum, and total nerve spike frequency when right atrial and right ventricular systolic and diastolic pressures were altered by means of intracardiac balloons. Receptors that responded to volume and pressure changes were found in both the right atrium and right ventricle. Nerve activity in these afferents increased with increasing right atrial and right ventricular pressures. These mechanoreceptors were more responsive in the upper physiological ranges of right heart pressures. In most nerve fibers studied, maximum activity occurred during both right atrial and right ventricular diastole.