AJP - Heart and Circulatory Physiology, Vol 234, Issue 3 293-H299, Copyright © 1978 by American Physiological Society
Cardiovascular-respiratory reflex interactions between carotid bodies and upper-airways receptors in the monkey
M. B. Daly, P. I. Korner, J. E. Angell-James and J. R. Oliver
The carotid bodies were stimulated in the anesthetized pig-tailed macaque
monkey (Macaca nemestrina) using i) brief injections of cyanide or
CO2-equilibrated bicarbonate solution into a common carotid artery, and ii)
longer perfusion with hypoxic hypercapnic blood in vascularly isolated
chemoreceptor preparations. In spontaneously breathing animals, brief
stimulations of the chemoreceptors consistently caused an increase in
pulmonary ventilation, bradycardia, and an increase in femoral vascular
resistance. When the same chemoreceptor stimulus was superimposed during
the apneic period, reflexly evoked by stimulating either the central ends
of the superior laryngeal nerves or the nasopharynx, the respiratory
stimulation was absent or minimal, but the bradycardia and vasconstriction
were greatly enhanced and exceeded the summed responses of separate
stimulation of the chemoreceptors and one or the other of the upper-airways
inputs. With sustained stimulation of the carotid bodies, hyperventilation,
tachycardia, and femoral vasodilatation occurred due to overriding
respiratory mechanisms. When superior laryngeal nerve stimulation was
superimposed on this response, apnea occurred and tachycardia was reversed
to bradycardia, and femoral vascular resistance increased above resting
level. The interaction of autonomic responses resulting from chemoreceptor
stimulation and from increases in the upper-airways inputs are
qualitatively similar in the monkey and in subprimate species. Those
involving specifically cardioinhibitory vagal responses are, in part at
least, dependent on mechanisms related to the concomitant changes in
respiration.
