AJP - Regulatory, Integrative and Comparative Physiology, Vol 255, Issue 5 693-R698, Copyright © 1988 by American Physiological Society
Neurogenic and humoral factors maintaining arterial pressure in conscious dogs
E. M. Hasser and V. S. Bishop
Department of Pharmacology, University of Texas Health Science Center, San Antonio 78284-7764.
This study examined the contribution of each primary pressor system to
resting arterial pressure and the ability of each to maintain pressure in
the absence of the other systems in conscious dogs. In dogs with intact
carotid sinus baroreflexes, ganglionic blockade (GB) reduced blood pressure
by 13 +/- 3 mmHg, whereas blockade of the renin-angiotensin (RAS) and
arginine vasopressin (AVP) systems did not significantly alter arterial
pressure. After removal of the other two systems, the depressor response to
blockade of the sympathetic nervous system (SNS) with hexamethonium and
atropine was significantly augmented (-33 +/- 3 mmHg), whereas captopril
(CAP) blockade of the RAS reduced pressure 14 +/- 4 mmHg, and AVP blockade
decreased pressure 12 +/- 2 mmHg. In sinoaortic-denervated (SAD) dogs, the
SNS exhibited a greater contribution (28 +/- 4 mmHg) to resting pressure
compared with intact, and the role of the RAS (10 +/- 2 mmHg) was also
augmented, whereas the effects of AVP blockade were unaltered. Effects of
GB and CAP were unaltered after blockade of the other systems in SAD
animals, whereas the depressor response to AVP antagonist (-13 +/- 2 mmHg)
was significantly augmented. Results indicate the SNS is the primary
pressor system in resting intact or SAD conscious dogs, whereas the RAS
also contributes to resting blood pressure in SAD animals. The ability of
the SNS alone to maintain arterial pressure after acute removal of the
other systems is also significantly greater than that of AVP or the RAS.
