Journal of Applied Physiology, Vol 50, Issue 6 1277-1281, Copyright © 1981 by American Physiological Society
Brain temperatures in running quail
D. L. Kilgore Jr, G. F. Birchard and D. F. Boggs
Hypothalamic (Tb) and colonic (Tc) temperatures of adult bobwhite (colinus
virginianus) were measured simultaneously while the birds were resting and
running on a motor-driven treadmill at fixed belt speeds ranging from 0.42
to 0.75 m.s-1 at two air temperatures, room and 30 degrees C. For
comparison, Tb and Tc were also recorded simultaneously in resting bobwhite
exposed to air temperatures of 30 to 45 degrees C. Hypothalamic
temperatures of both environmentally heat-stressed and running bobwhite
were consistently below colonic temperatures. The mean magnitude of this
body-to-brain temperature difference in birds running at the highest speeds
(i.e., with the greatest exercise heat loads) and at a high air temperature
(30 degrees C) was similar to that of extremely heat-stressed resting birds
[ambient temperature (Ta) = 45 degrees C]. Furthermore, the body-to-brain
temperature difference in quail running at 30 degrees C increases with
running speed. That these birds running at maximum speeds can maintain
their Tb nearly constant while Tc increases suggests enhanced heat transfer
in the rete mirabile ophthalmicum, an extracranial site of arteriovenous
heat exchange.
