Effects of alpha-human atrial natriuretic peptide on the interrelationship of arterial pressure, aortic nerve activity, and aortic diameter.

A previous study has suggested that atrial natriuretic peptide (ANP) alters arterial baroreflex control of lumbar and renal sympathetic nerve activity. To explore these mechanisms, we examined the interrelationship of arterial pressure, afferent aortic nerve activity, and aortic diameter in rabbits anesthetized with alpha-chloralose before and after sinoaortic denervation and bilateral vagotomy. Arterial pressure was decreased in stepwise fashion by intravenous infusion of alpha-human ANP (alpha-hANP, 0.1-1.0 microgram/kg/min) or sodium nitroprusside (SNP, 1-5 micrograms/kg/min). Both in rabbits with intact baroreceptors and in those with baroreceptors denervated, aortic nerve activity and the aortic diameter decreased during hypotension caused by the infusion of SNP but remained unchanged during hypotension caused by the infusion of alpha-hANP. In addition, we examined the effects of alpha-hANP and SNP on the responses of the aortic diameter and aortic nerve activity to rapid changes in arterial pressure caused by intravenous phenylephrine or nitroglycerin. Changes in aortic nerve activity and the aortic diameter in response to rapid changes in arterial pressure caused by phenylephrine or nitroglycerin were not different between the infusion of alpha-hANP and SNP. These results suggest that aortic nerve activity remains unchanged despite hypotension during the infusion of alpha-hANP, because alpha-hANP dilates the aorta. Since the aortic diameter increases, strain of aortic baroreceptors does not decrease. A second suggestion is that alpha-hANP does not alter aortic baroreceptor responses to changes in arterial pressure caused by phenylephrine or nitroglycerin.