ANP, BNP, and CNP enhance bradycardic responses to cardiopulmonary chemoreceptor activation in conscious sheep.
We demonstrated previously that atrial natriuretic peptide (ANP) enhances reflex bradycardia to intravenous serotonin [5-hydroxytryptamine (5-HT)] (von Bezold-Jarisch reflex) in rats. To determine whether 1) ANP affects this cardiopulmonary vagal reflex in another species and 2) B-type (BNP) and C-type (CNP) natriuretic peptides share with ANP the ability to modulate this reflex, we used intravenous phenylbiguanide (PBG), a 5-HT(3) agonist, as the stimulus to evoke a von Bezold-Jarisch reflex (dose-related, reproducible bradycardia) in conscious adult sheep (n = 5). Three doses of PBG (13 +/- 3, 20 +/- 3, and 31 +/- 4 microg/kg) injected into the jugular vein caused reflex cardiac slowing of -7 +/- 1, -15 +/- 2, and -36 +/- 3 beats/min, respectively, under control conditions. These doses of PBG were repeated during infusions of ANP, BNP, or CNP (10 pmol. kg(-1). min(-1) iv), or vehicle (normal saline). Each of the natriuretic peptides significantly (P < 0.05) enhanced the sensitivity of bradycardic responses to PBG by 94 +/- 8% (ANP), 142 +/- 55% (BNP), and 61 +/- 16% (CNP). Thus not only did ANP sensitize cardiopulmonary chemoreceptor activation in a species with resting heart rate close to that in humans, but BNP and CNP also enhanced von Bezold-Jarisch reflex activity in conscious sheep.
Thomas
C J
CJ
Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Victoria 3010, Australia.
May
C N
CN
Sharma
A D
AD
Woods
R L
RL
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D017704:Baroreflex / Q000187:drug effects* / Q000502:physiology*; D001645:Biguanides / Q000494:pharmacology; D001794:Blood Pressure / Q000502:physiology; D001919:Bradycardia / Q000139:chemically induced / Q000503:physiopathology*; D002628:Chemoreceptor Cells / Q000502:physiology*; D003243:Consciousness; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000502:physiology; D020097:Natriuretic Peptide, Brain / Q000494:pharmacology; D020098:Natriuretic Peptide, C-Type / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D012756:Sheep; D014630:Vagus Nerve / Q000502:physiology
D001645:Biguanides; D017366:Serotonin Receptor Agonists; D020097:Natriuretic Peptide, Brain; D020098:Natriuretic Peptide, C-Type; D009320:Atrial Natriuretic Factor; C008846:phenyl biguanide