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Fever and behavioral thermoregulation in young and old rats
M Florez-Duquet1, E Peloso, E Satinoff
1Department of Psychology and Program in Neuroscience, University of Delaware, Newark, Delaware 19716-2590, USA.
Summary
Old rats develop fever using behavioral thermoregulation by selecting warmer environments after lipopolysaccharide (LPS) injection, unlike young rats. This suggests age-related differences in fever response mechanisms.
Area of Science:
- Neuroscience
- Gerontology
- Physiology
Background:
- Lipopolysaccharide (LPS) reliably induces fever in young rats at standard temperatures.
- Older rats exhibit blunted fever, no fever, or hypothermia following LPS administration.
- Age-related deficits in fever response suggest potential compensatory mechanisms.
Purpose of the Study:
- To investigate if aged rats utilize behavioral thermoregulation to facilitate fever development after LPS exposure.
- To compare fever responses and thermal preferences between young and old rats injected with LPS.
Main Methods:
- Young and old rats were surgically implanted with temperature transmitters.
- Animals were exposed to a thermal gradient (10-40°C) post-implantation.
- Rats received intraperitoneal injections of LPS or saline at 23°C, followed by return to the gradient.
Main Results:
- Young rats consistently developed fever at 23°C, while old rats did not.
- Old rats significantly selected warmer ambient temperatures (T(a)) in the gradient compared to young rats.
- Only after selecting warmer T(a) in the gradient did old rats exhibit febrile responses.
Conclusions:
- Aged rats employ behavioral thermoregulation, actively seeking warmer environments to achieve fever.
- LPS administration appears to elevate the thermal set point in old rats, but febrile response is contingent on selected ambient temperature.
- These findings highlight age-dependent alterations in fever pathophysiology and the role of behavioral adaptation.