AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 3 705-R711, Copyright © 1991 by American Physiological Society
Dynamics of behavioral thermoregulation in the rat
C. J. Gordon, K. L. Lee, T. L. Chen, P. Killough and J. S. Ali
Neurotoxicology Division, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
Past studies have found that the laboratory rat placed in a temperature
gradient prefers temperatures that are markedly below its lower critical
ambient temperature (LCT), whereas other rodents (e.g., mouse, hamster, and
guinea pig) generally select thermal environments associated with minimal
metabolic expenditure. To further study the rat's thermoregulatory
behavior, a temperature gradient was designed to monitor the selected
ambient temperature (STa) and motor activity (MA) of food-deprived rats of
the Long-Evans (LE), Fischer 344 (F344), and Sprague-Dawley (SD) strains
over a 22-h period. All three rat strains selected relatively cool STas of
21-26 degrees C during the first 1-3 h in the temperature gradient. This
was followed by a gradual increase in the STa that peaked at 4 (F344) to 6
h (SD and LE) after being placed in the gradient. The LE strain had a
significantly lower STa during the initial period in the gradient. There
were slight decreases in the STa during the nocturnal phase in the F344 and
SD strains concomitant with marked increases in MA. These results indicate
that the rat requires a relatively long adjustment period in a temperature
gradient before it exhibits STas that are associated with minimal metabolic
expenditure. Given adequate time for accommodation, behavioral
thermoregulatory responses of the rat appear to be similar to those of
other rodents.
