Do natriuretic peptides modify arterial baroreflexes in sheep?

While atrial and B-type natriuretic peptides (ANP and BNP) have been shown to enhance reflex responses attributed to cardiac vagal afferents, their effects on arterial baroreceptor reflex function remain controversial. The actions of C-type natriuretic peptide (CNP) in this regard are unknown. To clarify their actions on arterial baroreflexes, we tested whether i.v. infusions of ANP, BNP or CNP at 10 pmol kg(-1) min(-1) modified the steady-state mean arterial blood pressure-heart rate (MAP-HR) relationship in conscious sheep. At this dose, all three natriuretic peptides are known to enhance the cardiac chemoreflex response to phenylbiguanide (Bezold-Jarisch reflex). Sigmoid MAP-HR relationships were constructed from the steady-state responses to alternating injections of vasopressor (phenylephrine, 1-15 microg kg(-1)) and vasodepressor agents (nitroprusside, 1-15 microg kg(-1)) in the absence and presence of infused ANP, BNP or CNP (tested in random order at least 1 week apart). No parameter of the steady-state baroreflex relationship was significantly altered by infusion of any of the three natriuretic peptides. We conclude that in conscious sheep, normal arterial baroreceptor-HR reflex function prevails in the presence of moderate doses of ANP, BNP or CNP.