AJP - Regulatory, Integrative and Comparative Physiology, Vol 243, Issue 5 537-R545, Copyright © 1982 by American Physiological Society
Role of central and peripheral chemoreceptors in diving responses of ducks
D. R. Jones, W. K. Milsom and G. R. Gabbott
Using techniques of vascular isolation and subsequent perfusion we have
investigated the effects of altering blood gas tensions, in the cerebral
and carotid body circulations, on some cardiovascular responses to diving
in unanesthetized ducks. After denervating the right carotid body,
perfusion of the innervated left carotid body with hyperoxic blood
significantly reduced diving bradycardia and reduced the increase in
hindlimb vascular resistance (HLVR) in 1-min dives compared with dives in
which the innervated carotid body was autoperfused. Denervation of systemic
arterial baroreceptors reduced the fall in heart rate (HR) and increased
the rise in HLVR in all dives. Cross-perfusion of the head, from a donor
with blood of normal blood gas tensions, did not significantly affect HR or
HLVR in 2-min dives compared with dives in which the head was autoperfused.
however, cross-perfusing the cerebral circulation with blood of elevated
PaCO2 caused significantly greater increases in HLVR than when high PaCO2
only affected the peripheral circulation. We conclude that peripheral
chemoreceptors cause virtually all the bradycardia in the later stages of a
dive but only about one-half the increase in HLVR, a significant
contribution comes from the stimulation of central chemoreceptors with
blood of high PaCO2.
