alpha-ANP alters reflex control of lumbar and renal sympathetic nerve activity and heart rate.

This study examined the effects of synthetic alpha-rat atrial natriuretic peptide (alpha-rANP) on arterial pressure (AP), heart rate (HR), and renal and lumbar sympathetic nerve activity (SNA) in rats with intact arterial baroreceptors before and after bilateral vagotomy and in those with sinoaortic denervation before and after vagotomy. In intact rats, alpha-rANP decreased AP, which was accompanied by the decrease in renal SNA ad HR and no change in lumbar SNA. In contrast, the increase in lumbar SNA and HR occurred during hypotension caused by nitroglycerin. In rats with intact arterial baroreceptors and vagi sectioned, renal and lumbar SNA and HR did not change during hypotension with alpha-rANP. In addition, alpha-rANP did not alter the gain of arterial baroreflex control of lumbar SNA in these rats. In rats with sinoaortic denervation, alpha-rANP decreased HR and renal and lumbar SNA before vagotomy but did not change them after vagotomy. These results suggest, first, that alpha-rANP activates vagal afferents and thereby inhibits renal and lumbar SNA and HR and, second, that alpha-rANP may reset arterial baroreflex control of SNA and HR to a lower pressure range.