Journal of Applied Physiology, Vol 53, Issue 6 1405-1410, Copyright © 1982 by American Physiological Society
Control of heart rate by carotid body chemoreceptors during diving in tufted ducks
P. J. Butler and A. J. Woakes
Previous work has shown that during forcible submersion of domestic ducks
there is a gradual reduction in heart rate to 10-20% of its predive value
after 45-60 s. Bilateral denervation of the carotid body chemoreceptors
abolishes most of this bradycardia. By use of implanted radio transmitters
it has been shown that in free-swimming tufted ducks, Aythya fuligula,
there is an immediate reduction in heart rate, on spontaneous diving, from
an elevated predive level. It then increases for a few seconds before it
stabilizes at a level similar to that recorded when the duck is swimming
fairly vigorously. The present study has shown that, following bilateral
denervation of the carotid bodies, there is a significant increase in mean
dive duration but no effect on the immediate reduction in heart rate on
submersion. Heart rate is, however, significantly higher toward the end of
spontaneous dives after carotid body denervation. Unlike the situation in
mallards and their domesticated varieties, carotid body denervation has no
effect on heart rate in tufted ducks during the first 40 s of forced dives.
The carotid bodies therefore do not play the dominant role in cardiac
control during submersion of diving ducks that has been suggested by work
involving the forcible submersion of the mallard duck and its domesticated
varieties.
