Journal of Applied Physiology, Vol 63, Issue 4 1671-1680, Copyright © 1987 by American Physiological Society
Respiratory influence of peripheral chemoreceptor stimulation in maturing rabbits
C. M. Schramm and M. M. Grunstein
Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado.
To evaluate whether the influence of peripheral chemoreceptor (PCR)
stimulation is centrally modulated by hypoxia, the respiratory effects of
sodium cyanide (NaCN) infusion were compared during room air and 10% O2
inhalation in 18 lightly anesthetized, tracheotomized rabbits of varying
postnatal age (1-33 days). During normoxia, noncumulative infusions of NaCN
(5-400 micrograms/kg body wt) produced dose-dependent ventilatory (VE)
stimulation. Maximal VE stimulation (VEmax) and ventilatory sensitivity to
NaCN [i.e., log dose producing 50% of VEmax (log ED50)] did not
significantly vary with age, with the average VEmax and log ED50 values
amounting to 238% above base line and 1.564 micrograms/kg, respectively.
During hypoxia, after initial stimulation (average: 152%), VE progressively
decreased and stabilized to 67% above the normoxic base-line level. In
contrast to normoxia, subsequent NaCN administration during steady-state
hypoxia produced dose-dependent VE depression, occasionally manifested by
abrupt apnea. The NaCN effect during hypoxia was significantly related to
age (P less than 0.05), as well as to the estimated change in CO2
production during hypoxia (P less than 0.01). Both the respiratory
depressant effects of hypoxia alone and in combination with NaCN were
abolished after denervation of the peripheral chemoreceptors. These
findings demonstrate that while PCR stimulation during normoxia produces
ventilatory stimulation, the influence of enhanced PCR input during hypoxia
is centrally modulated to produce ventilatory depression.
