AJP - Heart and Circulatory Physiology, Vol 253, Issue 6 1409-H1417, Copyright © 1987 by American Physiological Society
Control of arterial pressure in conscious, sinoaortic-denervated sheep in normoxia and hypoxia
M. Miki, K. Miki, G. Hajduczok, D. Curran-Everett and J. A. Krasney
Department of Physiology, State University of New York School of Medicine, Buffalo 14214.
The contribution of the sinoaortic reflexes to the control of both the mean
level and variability of arterial pressure (Pa) and heart rate (HR) was
studied in five adult ewes after chronic section of the carotid sinus and
aortic depressor nerves (SAD). SAD group responses were compared with a
sham-operated group (n = 6). Pa was 15% lower in the SAD group due to a
reduction of total peripheral resistance. The standard deviations and
coefficients of variation for both Pa and HR obtained by continuous 16-h
monitoring (10-s intervals) in the SAD sheep were not significantly
different from those of the sham group. Arterial hypoxia (arterial PO2 = 40
mmHg for 96 h) had no significant influence on the mean values or
variability for Pa and HR for either group, although both groups spent more
time lying down. Ventilation was unchanged in the SAD group. Thus mean Pa
is lower after removal of baroreceptor and chemoreceptor inputs, but the
variabilities of both HR and Pa are unaltered during both normoxia and
hypoxia in this sedentary species.
