Rapid brain cooling in diving ducks.
Caputa, Micha, Lars Folkow, and Arnoldus Schytte Blix.
Department of Arctic Biology and Institute of Medical Biology,
University of Tromso, N-9037 Tromso, Norway, Department of Animal
Physiology, N Copernicus University, 87-100 Toru[tilde]n, Poland
APStracts 5:0158R, 1998.
Hypothermia may limit asphyxic damages to the brain and many small
homeotherms have been shown to use anapyrexic strategies when exposed
to asphyxic conditions. Larger homeotherms do not seem to use the
same strategy, but could save oxygen and prevent hypoxic brain damage
by employing selective brain cooling (SBC) in connection with
asphyxia. To test the hypothesis that selective brain cooling may
take place in connection with asphyxia we have recorded brain
(hypothalamic - THyp) and body (colonic - TC) temperatures and heart
rates in four Pekin ducks during 5-min simulated (head submersion)
diving in cold water (10(C). Diving resulted in a drop in THyp
(3.1_(_1.4oC) which continued into the recovery period (p<0.001).
Restricting heat loss from the buccal cavity and eyes during diving
compromised brain cooling in an additive manner. TC was not
influenced by diving. Control cooling of the head with crushed ice
during a 5-min period of undisturbed breathing had no effect on THyp.
Warm water (35(C) markedly reduced brain cooling, and dive capacity
was reduced by about 14% (p<0.05) compared with diving in water at
10oC. The data suggest that SBC is used in ducks during diving and we
propose that this mechanism may enable the bird to save oxygen for
prolonged aerobic submergence, and to protect the brain from asphyxic
damages.
Received 9 December 1997; accepted in final form 13 April 1998.
APS Manuscript Number R777-7.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 24 April 1998