Effects of brain natriuretic peptide on renal nerve activity in conscious rabbits

Abstract

Responses of renal nerve activity (RNA) to intravenous infusion of brain natriuretic peptide (BNP) were examined in chronically instrumented conscious rabbits with all baroreflexes intact, sinoaortic baroreceptor denervation (SAD), and SAD plus vagotomy. In intact rabbits, an infusion of BNP at a rate of 0.3 microgram.kg-1.min-1 for 30 min decreased mean arterial pressure (MAP) by 8 +/- 1 mmHg and increased RNA by 48 +/- 4% but did not alter heart rate (HR). The decrease in MAP in SAD rabbits (20 +/- 3 mmHg) was greater than in intact rabbits, whereas RNA increased less (21 +/- 7%). After SAD plus vagotomy, BNP lowered MAP by 25 +/- 4 mmHg, whereas RNA was not altered significantly. To further examine the effects of BNP on baroreflex control of HR and RNA, the baroreceptors were stimulated or unloaded by raising or lowering MAP by injections of phenylephrine or glyceryl trinitrate, respectively. The maximum change in each HR or RNA response to phenylephrine or glyceryl trinitrate was plotted against the maximum change in each MAP response and a logistic function curve was fitted to the MAP-HR and MAP-RNA relationship. BNP did not alter the slope of either curve but shifted both curves to the left. These results indicate that 1) in intact rabbits, BNP increases RNA due to sinoaortic and cardiopulmonary baroreflexes and 2) BNP resets the baroreflex control of HR and RNA to a lower arterial pressure.

Do natriuretic peptides modify arterial baroreflexes in sheep?

“…For CNP, the results are the first of their kind. Those with BNP support findings from the one previous report in rabbits (Morita et al 1989). The ANP results are similar to previous findings in rats (Woods et al 1994; Thomas et al 1997, 2002; Thomas & Woods, 2003) and humans (Ebert & Cowley, 1988).…”

“…There is only one study of the effects of this peptide directly on arterial baroreflexes. Morita et al (1989), using drug‐induced changes in blood pressure, demonstrated that BNP did not alter sigmoid curves describing the mean arterial pressure–heart rate (MAP–HR) or MAP–renal sympathetic nerve activity relationships in conscious rabbits. To our knowledge there are no reports of the action CNP on arterial baroreflexes.…”

Nesiritide in infants and children with congestive heart failure*

“…In the VMAC trial, there was a net output of Ͼ1 L during a 24-hr period. Although one recent study failed to show a beneficial effect on diuresis with nesiritide in patients with CHF (12), previous pilot studies suggested the renal excretory effects of nesiritide are related to changes in both glomerular hemodynamics and tubular function (13,14). Importantly, administration of nesiritide did not result in a significant increase in serum creatinine in this pediatric population.…”

Profound vagal reactions to brain natriuretic peptide

“…BNP also interacts with the autonomic nervous system and in experimental animals has been shown to decrease sympathetic outflow [5] although the role of BNP in central control of blood pressure is less clear. This potential interaction has not been studied in man although it is worth noting that ANP and BNP have similar haemodynamic effects in man [3,6] and are equipotent as agonists of the type A natriuretic peptide receptor [7].…”