| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1988: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1987: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
It is not known whether atrial natriuretic peptide (ANP) has effects on renal sympathetic nerve activity which regulates renal function This study examined the effects of synthetic alpha-rat atrial natriuretic peptide (alpha-rANP) on arterial pressure-(AP), heart rate (HR), and renal 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 and HR. In contrast, the increase in HR occurred during hypotension caused by nitroglycerin. In rats with intact arterial baroreceptors and vagi sectioned, renal SNA and HR did not change during hypotension with alpha-rANP. In rats with sinoaortic denervation, alpha-rANP decreased HR and renal SNA before vagotomy but did not change them after vagotomy. These results suggest, first, that alpha-rANP activates vagal afferents and thereby inhi
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bits renal SNA and HR and, second, that alpha-rANP my reset arterial baroreflex control of SNA and HR to a lower pressure range.
The above study has suggested that ANP alters arterial baroreflex control of sympathetic nerve activity. To explore the mechanisms, we examined the interrelationship amon arterial pressure, afferent aortic nerve activity and the 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 g/kg/ium) or sodimu nitroprussede (SNP: 1 - 5 g/kg/min). In rabbits with intact baroreceptors as well as 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 phenylephine 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, first, 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 dose 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. Less
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