Excitation of Afferent Cardiac Sympathetic Nerves is Modulated by Nitroglycerin

Abstract

Abstract

We examined the effect of nitroglycerin on stimulation of sympathetic nerve fibers arising from receptor sites in the left ventricular wall during acute coronary artery occlusion. Sympathetic afferent nerve activity was recorded in single and multifiber nerve preparations dissected from slips of T₃ white rami communicantes. Acute left anterior descending or left circumflex coronary artery occlusion produced an increase in segmental myocardial length and excitation of afferent cardiac sympathetic nerve fibers in the region of the myocardium supplied by the occluded artery. Intravenous administration of nitroglycerin in doses up to 100 μg/kg and sodium nitroprusside (50 μg/min) reduced systolic bulge during coronary occlusions and suppressed excitation of these myelinated and unmyelinated afferent fibers. Local intracoronary injection of nitroglycerin (100 μg) produced neither a change in systemic blood pressure nor a change in excitation of the afferent nerve fibers during coronary occlusion. Systemic administration of nitroglycerin sufficient to lower blood pressure and reduce epicardial systolic lengthening in the ischemic zone is associated with inhibition of firing of cardiac afferent sympathetic nerves.