Atrial natriuretic factor attenuates carotid baroreflex-mediated cardioacceleration in humans

We tested the hypothesis that infusions of atrial natriuretic factor (ANF) attenuate carotid baroreflex-mediated tachycardia in humans. The afferent profile from carotid baroreceptors was altered by repeated, intermittent random applications of neck suction (40 mmHg) and neck pressure (20 mmHg) to healthy volunteers during supine control and during infusions of 15 (n = 6) or 25 ng.kg-1.min-1 (n = 9) of alpha-human ANF or during placebo (n = 9). ANF infusions resulted in five- and eightfold increases of plasma ANF, which did not alter base-line cardiac interval, blood pressure, respiratory sinus arrhythmia, plasma renin activity, vasopressin, or norepinephrine but did reduce central venous pressure. Reflex bradycardic responses were unaltered during these infusions. Reflex tachycardic responses to carotid compression were significantly blunted (up to 40%) during infusions of ANF and were unchanged during placebo. These responses may be due to a sensitization of cardiac receptors and augmentation of cardiac-vagal afferent traffic by ANF, which diminishes reflex cardiac-sympathetic outflow during carotid baroreceptor unloading.