Peripheral Resistance after Cardiac Output Reduction the Barodenervated Cat

Studies on the nervous or humoral control of total peripheral resistance are often complicated by concomitant changes in cardiac output. We studied the influence of output on peripheral resistance in the absence of modulating reflexes. In barodenervated and vagotomized cats, cardiac output was varie...

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Bibliographic Details
Published in:Circulation research 1983-01, Vol.52 (1), p.7-15
Main Author: Borgdorff, Piet
Format: Article
Language:English
Subjects:
Animals
Cardiac Output
Cats
Denervation
Feedback
Ganglia, Sympathetic - drug effects
Pressoreceptors - physiology
Reflex - physiology
Renin-Angiotensin System
Vagotomy
Vascular Resistance
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Summary:Studies on the nervous or humoral control of total peripheral resistance are often complicated by concomitant changes in cardiac output. We studied the influence of output on peripheral resistance in the absence of modulating reflexes. In barodenervated and vagotomized cats, cardiac output was varied by graded inferior caval vein occlusion or by arterial bleeding. Total peripheral resistance was obtained with an analogue device which continuously divided the pressure difference between aorta and caval vein by cardiac output (electromagnetic flowmeter). Cardiac output reduction caused a decrease of peripheral resistance, followed within 2 minutes by a slow increase. Resistance stabilized at preocclusion levels within 5.8 (range 4−9) minutes. The relative changes in resistance and cardiac output were linearly related, when cardiac output was reduced by less than 40%. With larger reductions, the relation became nonlinear, and with a drop of more than 65%, no further change was noticed. These changes in resistance could not be explained by variations in blood viscosity as measured by Hct. They were nonnervous in naturewhen all reflexes were abolished by ganglionic blockade, a similar pattern was found. Humoral mechanisms like the vasopressin or the renin-angiotensin system, known to be activated by hypotension, probably played no role, since arterial osmolality remained stable and captopril did not influence the resistance response. The involvement of metabolic autoregulation could not be excluded, but was unlikely because O2 consumption and serum lactate did not change.
ISSN:0009-7330
1524-4571
DOI:10.1161/01.RES.52.1.7