Journal of Applied Physiology, Vol 49, Issue 4 663-668, Copyright © 1980 by American Physiological Society
Effects of gravitational profiles on the rat's thermoregulatory response to cold
E. R. Schertel, J. M. Horowitz and B. A. Horwitz
Unrestrained rats were subjected to a 1-h period of cold exposure during
centrifugation to characterize their ability to regulate core temperature
(Tc) and to determine if this regulation was dependent on the amplitude of
the hypergravic field before the cold exposure. Tc was measured in
unrestrained rats by the use of a thermistor implanted adjacent to the
carotid artery. One hour of cold exposure applied over the last hour of
either a 1-, 4-, 7-, 13-, 19-. 25-, or 37-h period at 3 G evoked a decrease
in Tc of about 3 degrees C. This fall in Tc was significantly greater than
changes in Tc in cold-exposed rats at 1 G. No significant differences were
found between the measured decreases in Tc observed for the 1-h cold
exposures during the first 37 h at 3 G. However, when rats were subjected
concurrently to cold and acceleration after 8 days at 3 G, they exhibited a
smaller fall in Tc, suggesting a partial recovery of the
acceleration-induced impairment of temperature regulation. In another
series of experiments, the gravitational field profile was changed in
amplitude in three different ways during the 3-h period preceding the 1-h
cold exposure at 3 G. Despite the different gravitation field profiles
before cold, the magnitude of the fall in Tc over the 1-h period of cold
exposure was the same of all cases. These results suggest that the
thermoregulatory impairment has a rapid onset, it a manifestation of an
ongoing effect of hypergravity, and is not dependent on the prior G
profile. The inability of rats to maintain Tc when cold exposed may be
transient as indicated by the partial recovery of regulation by the 8th
day.
