AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 6 679-R685, Copyright © 1985 by American Physiological Society
Central control of expired air temperature and other thermoregulatory effectors in reindeer
J. B. Mercer, H. K. Johnsen, A. S. Blix and R. Hotvedt
Norwegian reindeer (Rangifer tarandus tarandus) were provided with
chronically implanted hypothalamic perfusion thermodes to determine to what
extent expired air temperature (Tex) is centrally controlled. The effects
that alterations of hypothalamic temperature (Thy) had on metabolic heat
production, respiratory frequency, respiratory evaporative heat loss, and
rectal and leg-skin temperature were simultaneously recorded. Experiments
were conducted in conscious animals exposed to ambient temperatures (Ta) of
-20, 0, and 20 degrees C in summer, when fur insulation was minimal, and in
winter, when it was prime. Altering Thy induced changes in Tex, the degree
and direction of which depended on the prevailing Ta, season, and intensity
of hypothalamic thermal stimulation. These results indicate that Tex, and
hence nasal heat exchange, is under central control. The Thy-induced
changes in the other measured parameters confirm that hypothalamic
thermosensitivity in these animals is similar to that previously found in
other mammalian species.
