In order to verify the hypothesis that possible interactions with the autonomic nervous system may contribute to the cardiovascular effects of atrial natriuretic factor (ANF), 9 rabbits were anesthetized to study the effect of the infusion of synthetic human ANP (2 mcg/kg in bolus followed by 0.2 mcg/kg/min for 20 min iv) on the reflex responses induced by intra-arterially injected BK (250 ng) and hypertonic NaCl (10%) or glucose (40%). The infusion of ANP provoked a decrease in systolic (SBP, 14%) and diastolic (DBP, 8%) pressure without any significant changes in heart rate (HR). The injection of BK and hypertonic NaCl into femoral arteries carried out during ANP infusion produced cardiorespiratory response patterns similar to those observed in control conditions. After injecting BK, a fall in SBP (25%), DBP (50%) and HR (16%), and an increase in breathing frequency were observed. After injecting NaCl, an increase occurred in SBP (20%), DBP (25%), HR (10%) and in depth of breathing. In the present experimental conditions, ANP has not been found to be capable of significantly interfering with the reflex pattern of cardiorespiratory responses either from the inhibition or activation of the sympathetic nervous system induced by chemical stimulation of muscle receptors.