AJP - Regulatory, Integrative and Comparative Physiology, Vol 244, Issue 6 778-R784, Copyright © 1983 by American Physiological Society
Influence of heating rate on control of heat loss from the tail in mice
C. J. Gordon
Although heating rate is important for stimulating thermoregulatory
reflexes, it is not known if the control system differentiates between
total heat gain and rate of heat gain. Exposing animals to microwaves
inside a waveguide permits continuous monitoring of whole-body heat
absorption. Tail skin temperature of restrained mice was recorded during
whole-body exposure to 2,450-MHz microwave radiation at specific absorption
rates (SAR) of either 11.5, 21.7, or 43.5 W . kg-1 and whole-body heat
loads of 0.3-14 J . g-1. The integration of tail skin temperature with
time, defined as the skin temperature index (STI), was measured as a
function of absorbed heat load. At ambient temperatures of 20 and 25
degrees C the STI, averaged with respect to heat load, increased
significantly with SAR. Depending on SAR, the sensitivity of heat loss from
the tail to microwave exposure increased 32-71% per 1 degree C elevation in
ambient temperature. The data indicate that heat loss from the tail
increases with the whole-body heat load accrued from microwave exposure.
When heat loss is averaged with respect to heat load, the rate of heat
absorption and ambient temperature increase the sensitivity of
thermoregulatory centers that control peripheral heat loss from the tail of
mice.
