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EFFECT OF PHYSICAL RESTRAINT ON THE LIMITS OF THERMOREGULATION IN TELEMETERED RATS
Aydin, C., C. Grace, AND C. J. GORDON. EFFECT OF PHYSICAL RESTRAINT ON THE LIMITS OF THERMOREGULATION IN TELEMETERED RATS. Experimental Physiology Journal. Wiley-Blackwell, Hoboken, NJ, 96(11):1218-27, (2011).
Physical restraint of rodents is often needed for nose-only exposure to airborne toxicants and is also used as a means of psychological stress. It is generally assumed that thermoregulation is impaired during restraint, leading to hyperthermia. A hyperthermic response should be related with the prevailing ambient conditions. To understand how ambient temperature (Ta) affects the response to restraint, core temperature (Tc) and heart rate (HR) were monitored by telemetry in rats subjected to physical restraint for one hour while Ta was held constant at 14 to 30°C at 2°C increments. Tc, was elevated at all Ta's with exception to 14°C where the rats became mildly hypothermic. There was an inverse relationship between Ta and HR; HR was significantly elevated in restrained rats at all Ta's except 22 and 24°C. Heat loss from the tail, estimated from Tc and tail skin temperature, was markedly reduced at all but the highest Ta's in restrained rats compared to unrestrained. The data suggest that the Ta limits of normothermia is narrowed in the restrained rat. That is, between 16 and 20°C, the rat maintains a relatively stable Tc that is slightly elevated above that of the unrestrained rat, but at Ta's above or below this range, the rat shows signs of hyperthermia and hypothermia, respectively. The ideal ambient temperature for restrained rats appears to be 20 and no higher than 22°C for the thermoregulatory system to maintain a regulated Tc in rats well adapted to physical restraint
Prolonged restraint of rats and mice is often used to evaluate the toxicity of air pollutants. The stress from prolonged restraint affects most physiological processes including temperature regulation. However, little is known on how the thermoregulatory system is affected by restraint. This paper assesses the limits and sensitivity of the thermoregulatory system of the restrained rat. The results will be extremely useful in the future use of inhalation toxicology studies.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LAB
TOXICOLOGY ASSESSMENT DIVISION