AJP - Heart and Circulatory Physiology, Vol 253, Issue 3 591-H597, Copyright © 1987 by American Physiological Society
Tachycardia of carotid chemoreceptors originates in apneic asphyxia in dogs
P. D. Gupta and M. Singh
Using various anesthetics, we investigated the heart rate changes resulting
from apneic asphyxia in paralyzed artificially ventilated dogs with 1) low
control heart rate (LCHR) and 2) high control heart rate (HCHR). We
observed that apneic asphyxia produced by stopping the ventilation pump for
1 min evoked tachycardia in dogs with LCHR and bradycardia in dogs with
HCHR. In dogs breathing 100% O2 in the preapneic period, the tachycardia
response was almost wholly abolished, whereas the bradycardia response was
attenuated. Intracarotid injection of sodium cyanide induced a tachycardia
response in dogs with LCHR and a bradycardia response in dogs with HCHR.
The results suggest that 1) apneic asphyxia evokes tachycardia or
bradycardia response depending on whether the resting cardiac vagal tone is
high or low, respectively, and 2) both types of heart rate responses are in
part due to stimulation of carotid chemoreceptors.
