Journal of Applied Physiology, Vol 52, Issue 5 1138-1146, Copyright © 1982 by American Physiological Society
Thermoregulatory influences on common carotid blood flow in the dog
M. A. Baker, M. J. Hawkins and R. D. Rader
Common carotid blood flow (CCBF) and respiratory water loss (RWL) were
measured in dogs resting at ambient temperatures between 25 and 50 degrees
C, during hypothalamic heating, and during light and heavy exercise at
ambient temperatures of 25 and 35 degrees C. In resting dogs, CCBF varied
with the level of RWL. Elevations in CCBF and RWL occurred within seconds
of each other during bursts of panting. Mean unilateral CCBF increased from
6.2 ml . min-1 . kg-1 at 25 degrees C to 16.8 ml . min-1 . kg-1 at 45
degrees C, in parallel with increasing RWL. Hypothalamic heating elicited
simultaneous elevations in CCBF and RWL, and the level of CCBF was strongly
correlated with the hypothalamic temperature. Both CCBF and RWL increased
rapidly at the onset of exercise and continued to rise during a 15-min run.
Highest rates of blood flow and evaporation occurred during heavy exercise
at 35 degrees C. It is concluded that the rate of blood flow through the
common carotid arteries in the dog is related to the thermoregulatory needs
of the animal, and most of the increased flow occurring during heat stress
is destined for evaporative surfaces of the nose, mouth, and tongue.
