Nonuniform enhancement of baroreflex sensitivity by atrial natriuretic peptide in conscious rats and dogs.
The influence of atrial natriuretic peptide (ANP) on the blood pressure (BP)-heart rate (HR) baroreflex was studied in conscious chronically instrumented dogs and rats. In both species, sigmoid steady-state baroreflex curves were constructed from the baroreflex changes in HR to alternating slow injections of vasopressor and vasodepressor drugs. When this method was used in dogs, ANP caused a small but significant (P < 0.05) enhancement of the sensitivity (22 +/- 10%) and curvature (26 +/- 10%) of the baroreflex, which was without a change in HR range. In rats, ANP had no significant effect on any baroreflex parameter derived from steady-state curves. By contrast, in the same rats, fast reflex HR responses to rapid increases in BP (ramp) exposed a substantial (81 +/- 21%) ANP-induced enhancement of baroreflex sensitivity. Contribution from arterial vs. nonarterial afferents to the baroreflex is not uniform between these two techniques (steady state reflects largely arterial baroreceptor input, ramp evokes a greater proportion of cardiopulmonary afferent activation). The present study demonstrated that baroreceptor HR reflex responses to ANP depend on the baroreflex techniques employed and probably exposed a selectivity by ANP for nonarterial baroreflex pathways.
Woods
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RL
Baker Medical Research Institute, Prahran, Victoria, Australia.
Courneya
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CA
Head
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GA
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D017704:Baroreflex / Q000187:drug effects* / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D006339:Heart Rate / Q000187:drug effects; D006706:Homeostasis; D008297:Male; D010275:Parasympathetic Nervous System / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D013564:Sympathetic Nervous System / Q000502:physiology
D009320:Atrial Natriuretic Factor