Differential sympathetic regulation of automatic, conductile, and contractile tissue in dog heart.

Sympathetic pathways mediating chronotropic, dromotropic, and inotropic responses during ansae subclavia stimulation were determined by sequential dissection around major cardiac vessels. Right sympathetic (RS) projections influencing ventricular contractile force converge at the common pulmonary artery and within the pulmonary artery nerves (PAN). RS projections influencing left atrial contractile force course within the PANs. RS pathways to pacemaker and right atrial contractile tissue were localized between the superior vena cava and ascending aorta. RS projections influencing conductile tissue converge between the common pulmonary artery and proximal right pulmonary artery. Left sympathetic (LS) projections to ventricular contractile tissue were localized at the common pulmonary artery, within the PANs, and in the ventral lateral cardiac nerve (VLCN). LS pathways influencing heart rate and conductile tissue were localized at the left pulmonary artery and coursing between the right pulmonary artery and left superior pulmonary vein. LS projections to atrial contractile tissue were localized within the PANs and coursing between the right pulmonary artery and left superior pulmonary vein. We conclude that there are parallel, yet distinct, projections of sympathetic efferents to automatic, conductile, and contractile tissue of the canine heart.