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Am J Physiol Regul Integr Comp Physiol 253: R848-R853, 1987;
0363-6119/87 $5.00
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AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 6 848-R853, Copyright © 1987 by American Physiological Society

ARTICLES

Selective cooling of the brain in reindeer

H. K. Johnsen, A. S. Blix, J. B. Mercer and K. D. Bolz
Department of Arctic Biology, University of Tromso, Norway.

Cineangiographic examination of reindeer exposed to local (hypothalamic) or general heating and cooling revealed that the angular oculi veins are constricted during cold stress but dilated during heat stress. Moreover, during heat stress a segment of the facial vein appeared to be occluded, causing the cold venous return from the nasal mucosa to be routed directly to the cavernous sinus for selective cooling of the brain. Histological examination of the vasoactive segment of the facial vein showed unusually thick longitudinal and circular layers of smooth muscle cells. Obstruction of angular oculi blood flow by clamping of the veins in the heat-stressed animal resulted in an immediate rise in brain temperature. When reindeer under heat stress shift from closed- to open-mouth panting, only the expiratory phase of the respiratory cycle takes place through the mouth, whereas inspiration through the nose is continued. In this way, cooling of the nasal mucosa and, hence, cooling of the brain, is maintained.


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O. Aas-Hansen, L. P. Folkow, and A. S. Blix
Panting in reindeer (Rangifer tarandus)
Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2000; 279(4): R1190 - R1195.
[Abstract] [Full Text] [PDF]


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