Cardiovascular reflexes controlling regional sympathetic outflow during coronary artery occlusion

In anesthetized rabbits, sympathetic activity was recorded in efferents to the skin of the ear (ESA), to the hindlimb muscles (MSA), splanchnic region (SSA), adrenals (ASA), and kidneys (KSA) in response to occlusion of the left circumflex coronary artery. Coronary occlusion caused an average decrease of mean arterial blood pressure by 18%. MSA and SSA increased, ESA decreased, and ASA, KSA, and heart rate either decreased or increased. In response to occlusion after cervical vagotomy, the fall in arterial mean pressure (11%) and the increases in MSA and SSA were less than those with intact vagal nerves. ASA and KSA increased, ESA decreased, and heart rate did not change significantly. In response to occlusion after selective sinoaortic denervation, arterial mean pressure dropped more than before denervation (32%); heart rate fell slightly. The increases in MSA and SSA were almost completely abolished, but in some rabbits irregular bursts were observed in KSA. The results suggest that a vagal depressor reflex dominated the arterial baroreflex in the control of the sympathetic outflow to the kidneys and adrenals without apparently influencing the outflow to the other investigated regions. There are some indications that excitation of cardiac receptors with sympathetic afferents contributed to the changes of ESA and KSA.