Influence of the cardiac nerves on coronary resistance

During constant pressure perfusion of the left coronary artery, stimulation of the peripheral cervical vagi produced a small but definite increase in coronary blood flow (CBF) in paced and nonpaced beating hearts and in fibrillating hearts. In the latter preparations flow increment was associated with an increase in coronary sinus blood pO 2 (CspO 2 ), changes similar to those elicited by intracoronary administration of acetylcholine. During constant pressure perfusion of the left coronary artery in paced and nonpaced beating hearts and in fibrillating hearts, stimulation of the stellate ganglia produced an initial decrease and subsequent increase in CBF. The increase in flow was associated in time with a reduction in CspO 2 in fibrillating hearts. The results obtained with stellate ganglion stimulation were reproduced by intracoronary administration of epinephrine. These observations indicate that the primary effect of vagus nerve stimulation on the coronary vasculature is vasodilation and that of stellate ganglion stimulation, constriction. The delayed increase in CBF seen with stellate ganglion stimulation is presumably secondary to the attending enhanced myocardial metabolic activity.