AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 1 82-R90, Copyright © 1986 by American Physiological Society
Changes in cardiac output and vascular resistance during behavioral stress in the rat
J. W. Hubbard, R. H. Cox, B. J. Sanders and J. E. Lawler
Normotensive Wistar-Kyoto (WKY) rats and borderline hypertensive rats (BHR)
were exposed to aversive classical conditioning procedures and chronically
instrumented with arterial catheters and electromagnetic flow probes around
the ascending aorta. After postoperative recovery, hemodynamic measurements
and blood samples were obtained from conscious animals at rest and during
aversive conditioning. The cardiovascular response to the behavioral stress
consisted of a significant increase in mean arterial blood pressure, total
peripheral resistance index, cardiac index, heart rate, and aortic dP/dt
for both strains. However, the elevated vascular resistance seen in the BHR
resulted in a significantly greater increase in mean arterial blood
pressure (21 mmHg) compared with the WKY rats (14 mmHg). In addition, the
BHR showed a significantly (P less than 0.05) greater plasma norepinephrine
concentration (760 +/- 99 pg/ml) in response to the stress than did the WKY
rats (559 +/- 53 pg/ml). These data suggest that an increase in cardiac
output, elevated vascular resistance, and increased sympathetic drive may
contribute to the development of stress-induced hypertension in this animal
model.
