AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 4 827-R835, Copyright © 1989 by American Physiological Society
Blood pressure responses to cyclic blood volume changes in awake and anesthetized dogs
D. R. Brown, A. W. Cowley Jr and D. B. Young
Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson 39216-4505.
A dynamic analysis of blood pressure regulation was performed in conscious
and anesthetized dogs. The mean arterial pressure (MAP) responses to 5 and
10% sinusoidal changes in total blood volume with cycle lengths of 1, 4,
and 8 min were measured in anesthetized 1) control dogs, 2) carotid and
vagal baroreflex (CVB)-denervated animals, and 3) spinal-ablated dogs; in
addition, the MAP responses to 10% sinusoidal blood volume changes with
cycle lengths ranging from 0.25 to 8 min were measured in conscious control
and CVB-denervated dogs. The presence of the baroreflexes in both the
conscious and anesthetized control dogs essentially eliminated MAP
excursions during the cyclic volume changes. The MAP changes in both the
conscious and anesthetized denervated dogs were large. However, the
responses in the anesthetized denervated dogs were linear, stationary, and
cycle-length insensitive with respect to the sinusoidal forcing function,
whereas the responses in the conscious CVB-denervated dogs were nonlinear,
nonstationary, and cycle-length dependent. These results indicate that the
cardiovascular system in the anesthetized CVB-denervated and spinal-ablated
dogs is passive or "hydraulic" in nature; conversely, factors other than
the carotid and vagal baroreflexes appear to exist that alter the arterial
pressure responses to cyclic blood volume perturbations in the conscious
CVB-denervated dogs.
