Article

Blood and brain temperatures of free-ranging black wildebeest in their natural environment.

Physiologisches Institut, Justus-Liebig-Universität, Giessen, Germany.
The American journal of physiology 01/1995; 267(6 Pt 2):R1528-36. pp.R1528-36
Source: PubMed

ABSTRACT Using miniature data loggers, we measured the temperatures of carotid blood and brain in four wildebeest (Connochaetes gnou) every 2 min for 3 wk and every 5 min, in two of the animals, for a further 6 wk. The animals ranged freely in their natural habitat, in which there was no shelter. They were subject to intense radiant heat (maximum approximately 1,000 W/m2) during the day. Arterial blood temperature showed a circadian rhythm with low amplitude (< 1 degree C) and peaked in early evening. Brain temperature was usually within 0.2 degrees C of arterial blood temperature. Above a threshold between 38.8 and 39.2 degrees C, brain temperature tended to plateau so that the animals exhibited selective brain cooling. However, selective brain cooling sometimes was absent even when blood temperature was high and present when it was low. During helicopter chases, selective brain cooling was absent, even though brain temperature was near 42 degrees C. We believe that selective brain cooling is controlled by brain temperature but is modulated by sympathetic nervous system status. In particular, selective brain cooling may be abolished by high sympathetic activity even at high brain temperatures.

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Keywords

2 min
 
42 degrees C
 
5 min
 
animals exhibited selective brain cooling
 
arterial blood temperature
 
blood temperature
 
Brain temperature
 
brain temperatures
 
carotid blood
 
circadian rhythm
 
Connochaetes gnou
 
helicopter chases
 
intense radiant heat
 
miniature data loggers
 
modulated
 
plateau
 
selective brain cooling
 
sympathetic activity
 
sympathetic nervous system status
 
wildebeest