Effect of arterial compliance on carotid sinus baroreceptor reflex
control of the circulation.
Potts, Jeffrey T., Tetsuo Hatanaka, and Artin A. Shoukas.
Department of Biomedical Engineering, The Johns Hopkins University
School of Medicine, 720 Rutland Ave., Baltimore, Maryland 21205
APStracts 2:0390H, 1995.
Capacitive properties of the arterial and venous segments of the
peripheral circulation are important in the regulation of cardiac
output and arterial blood pressure. We examined if an acute increase
in arterial compliance (Ca) would alter carotid sinus baroreflex
control of the circulation. Eight mongrel dogs were anaesthetized
with sodium pentobarbital and the carotid sinus regions were isolated
and perfused with non-pulsatile pressures. Open-loop baroreflex
response curves for systemic arterial pressure (SAP), heart rate
(HR), aortic blood flow (ABF), peripheral vascular resistance (PVR),
and left ventricular (LV) contractility were obtained when carotid
sinus pressure (CSP) was changed in 25 mmHg steps between 50-200 mmHg
under a control condition and when Ca was increased by including two
hydraulic compliant chambers to the arterial circulation (CS: 1.72 ml
x mmHg-1 and CL: 5.05 ml x mmHg-1). The compliant chambers
significantly increased Ca and altered the ratio of arterial-to
-venous compliance (Ca/Cv ratio). Changes in Ca/Cv ratio significantly
decreased the open-loop baroreflex gain (Gmax) for SAP (-2.3+/-0.5,
-1.6+/-0.3, -1.1+/-0.2 mmHg x mmHg-1, control vs CS vs CL,
P<0.05). Maximal baroreflex gain for ABF was decreased by CS (
-0.9+/-0.2 vs -0.3+/-0.1 ml x kg-1 x min-1, control vs CS,
P<0.05) and CL reversed the reflex changes in ABF (Gmax: +0.6+/
-0.3 ml x kg-1 x min-1). Maximal baroreflex gain for HR, PVR and LV
contractility was not altered when Ca was increased (P>0.05).
These findings indicate that an increase in Ca changes the Ca/Cv
ratio and alters carotid baroreflex control of SAP by modifying the
ABF response. We conclude that a change in Ca/Cv ratio affects the
reflex control of the circulation by altering the distribution of
blood volume between the arterial and venous circulations.
Received 21 August 1995; accepted in final form 3 November 1994.
APS Manuscript Number H978-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.