AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 3 625-R631, Copyright © 1989 by American Physiological Society
Effects of fentanyl on carotid sinus baroreflex control of circulation in rabbits
H. Ohsumi, M. Sakamoto, T. Yamazaki and F. Okumura
Department of Anesthesiology, National Cardiovascular Center, Osaka, Japan.
The effects of intravenous administration of fentanyl on carotid sinus
baroreflex control of hemodynamics were investigated in chronically
instrumented rabbits. Carotid sinus baroreflex was assessed by bilateral
carotid occlusion (BCO), and the responses of mean arterial pressure (MAP),
heart rate (HR), mean ascending aortic flow (MAF), and total peripheral
resistance (TPR) were obtained. Hemodynamic responses to BCO were examined
with cumulative doses of 5, 10, and 15 micrograms/kg of fentanyl. Fentanyl
did not affect MAP and TPR but reduced HR and MAF dose dependently.
Fentanyl did not attenuate the MAP response to BCO significantly. In
contrast, fentanyl significantly attenuated the TPR response from 0.126 +/-
0.003 to 0.104 +/- 0.005 mmHg.min-1.ml-1 and augmented the HR response from
31 +/- 2 to 47 +/- 3 beats/min in the conscious state and at 15
micrograms/kg of fentanyl, respectively. The administration of atropine
after the fentanyl attenuated MAP and HR responses to 79.9 and 27.7% of
those of 10 micrograms/kg of fentanyl, respectively. We suggest that these
dissociated hemodynamic responses reflect the vagotonic and sympatholytic
effects of fentanyl on the baroreflex pathways.
