AJP - Heart and Circulatory Physiology, Vol 249, Issue 3 655-H662, Copyright © 1985 by American Physiological Society
Baroreceptor reflex cardiovascular control in mongrel dogs and racing greyhounds
R. H. Cox, R. J. Bagshaw and D. K. Detweiler
The open-loop carotid sinus baroreflex control of arterial pressure-flow
relations were compared in mongrel dogs and racing greyhounds (GH)
anesthetized with alpha-chloralose. The carotid sinuses were bilaterally
isolated and perfused under controlled pressure. Pulsatile pressure and
flow were simultaneously measured in the ascending aorta, the celiac,
superior mesenteric, left renal, and right iliac arteries. Open-loop set
point values of mean arterial pressure were higher in GH before and after
vagotomy. Reflex gains were similar before vagotomy but lower in GH after
vagotomy. The overall range of control of arterial pressure was the same
before vagotomy but smaller in GH after vagotomy. The variation of mean
arterial pressure with mean carotid sinus pressure in GH was shifted toward
higher pressure levels similar to resetting. The overall effects of
vagotomy on carotid sinus baroreceptor reflex responses were smaller in GH.
Operating point values of regional resistance were generally smaller in GH.
Operating point sensitivities of regional resistance were the same except
for the iliac bed, which was more sensitive in GH. These results document
significant regional differences in the baroreceptor control of regional
hemodynamics between mongrels and greyhounds that could contribute to
altered responses especially to "hypertensive" perturbations.
