Brain thermal inertia,but no evidence for selective brain cooling,in free-ranging western grey kangaroos (<Emphasis Type="Italic">Macropus fuliginosus</Emphasis>) |
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Authors: | Shane K Maloney Andrea Fuller Leith C R Meyer Peter R Kamerman Graham Mitchell Duncan Mitchell |
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Institution: | (1) Physiology M311, School of Biomedical, Biomolecular and Chemical Science, University of Western Australia, Crawley, 6009, Australia;(2) Brain Function Research Group, School of Physiology, University of the Witwatersrand, 7 York Road, Parktown, 2193, South Africa;(3) Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA |
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Abstract: | Marsupials reportedly can implement selective brain cooling despite lacking a carotid rete. We measured brain (hypothalamic)
and carotid arterial blood temperatures every 5 min for 5, 17, and 63 days in spring in three free-living western grey kangaroos.
Body temperature was highest during the night, and decreased rapidly early in the morning, reaching a nadir at 10:00. The
highest body temperatures recorded occurred sporadically in the afternoon, presumably associated with exercise. Hypothalamic
temperature consistently exceeded arterial blood temperature, by an average 0.3°C, except during these afternoon events when
hypothalamic temperature lagged behind, and was occasionally lower than, the simultaneous arterial blood temperature. The
reversal in temperatures resulted from the thermal inertia of the brain; changes in the brain to arterial blood temperature
difference were related to the rate of change of arterial blood temperature on both heating and cooling (P < 0.001 for all three kangaroos). We conclude that these data are not evidence for active selective brain cooling in kangaroos.
The effect of thermal inertia on brain temperature is larger than might be expected in the grey kangaroo, a discrepancy that
we speculate derives from the unique vascular anatomy of the marsupial brain. |
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Keywords: | Thermoregulation Marsupial Brain temperature |
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