AJP - Heart and Circulatory Physiology, Vol 257, Issue 2 511-H524, Copyright © 1989 by American Physiological Society
A dynamic analysis of cardiovascular regulation using sinusoidal acceleration in dogs
D. C. Randall, J. A. Marquis, J. M. Evans and C. F. Knapp
Department of Physiology and Biophysics, University of Kentucky, Lexington 40536.
Control of cardiovascular function during time-dependent pooling of blood
in the upper and lower body was studied in intact dogs (n = 5) and in dogs
in which hearts had been surgically denervated (n = 5). The animal was
positioned horizontally on a platform mounted on the arm of a centrifuge;
rotation of the platform at one of nine rates with a period ranging from
3.3 min to 4 s exposed the subject to a sinusoidally varying force (+/- 2
g) that periodically translocated blood from the chest to the lower
quarters and back again. The resulting oscillatory changes in arterial
blood pressure (BP), cardiac output, stroke volume, heart rate (HR), and
peripheral resistance (PR) were analyzed using a fast Fourier transform.
Normal dogs were superior to cardiac-denervated dogs in minimizing arterial
BP fluctuations, especially in the midfrequency range (i.e., approximately
0.032 Hz); after pharmacological alpha-, beta-, and muscarinic-receptor
blockade, the BP oscillations were similar in the two groups. The unblocked
denervated dogs regulated BP poorly primarily because of their inability to
1) make appropriately timed changes in HR and 2) minimize inappropriate
oscillations in SV. Both groups of dogs in the unblocked state showed large
appropriately timed PR fluctuations at the lower frequencies, which
minimized BP oscillations; these became less optimally timed as
acceleration frequency increased, thereby potentiating the natural
disposition for BP to oscillate at the acceleration frequency. Afferent
information from cardiac receptors did not appear to be essential for
controlling this aspect of vascular function.
