Journal of Applied Physiology, Vol 67, Issue 1 128-133, Copyright © 1989 by American Physiological Society
Effect of cerebrospinal fluid hyperosmolality on sweating in the heat-stressed patas monkey
M. D. Owen, R. D. Matthes and C. V. Gisolfi
Department of Exercise Science, University of Iowa, Iowa City 52242.
Dehydration increases the osmolality of body fluids and decreases the rate
of sweating during thermal stress. By localizing osmotic stimuli to central
nervous system tissues, this study assessed the role of central stimulation
on sweating in a heat-stressed nonhuman primate. Lenperone-tranquilized
patas monkeys (Erythrocebus patas n = 5), exposed to 41 +/- 2 degrees C,
were monitored for calf sweat rate, rectal and mean skin temperatures,
oxygen consumption, and heart rate during infusions (255-413 microliters)
of hypertonic artificial cerebrospinal fluid (ACSF) into the third cerebral
ventricle. ACSF made hypertonic with NaCl to yield osmolalities of 800 and
1,000 mosmol/kgH2O significantly decreased sweat rate compared with control
ACSF (285 mosmol/kgH2O), achieving maximal reductions during infusion of 37
and 53%, respectively. Rectal temperature significantly increased during
the recovery period, reaching elevations of 0.69 and 0.72 degrees C,
respectively, at 20 min postinfusion. In contrast, ACSF made hypertonic
with sucrose (800 mosmol/kgH2O) failed to change sweat rate or rectal
temperature during infusion in three animals. Thus, intracerebroventricular
infusions of hypertonic ACSF mimicked dehydration-induced effects on
thermoregulation. The reduction in heat loss during infusion appeared to
depend on an elevation in cerebrospinal fluid [Na+] and not osmolality per
se.
