Measurements of core temperature in spontaneously hypertensive rats by radiotelemetry

Spontaneously hypertensive (SH) rats have been shown to have elevated colonic temperatures when compared with normotensive Wistar-Kyoto (WKY) rats. In the present study, core temperatures of SH and WKY rats were compared using radiotelemetry temperature sensors implanted in the abdominal cavity. At an ambient temperature (Ta) of 25 degrees C, SH and WKY rats showed no significant difference in core temperature over a 24-h period. After 1 h exposures to Ta values of 5, 15, 25, or 35 degrees C, there were no significant differences between core temperatures of SH and WKY rats, but at 40 degrees C the SH rats had a significantly higher core temperature than the WKY rats. Handling and moderate restraint also led to significantly higher core temperatures in the SH rats. Core temperature was also significantly increased in the SH rats compared with the WKY rats when a temperature probe was either inserted intermittently or inserted and left in place. The results of this study indicate that nonstressed SH rats do not have an elevated core temperature but that stress such as heat exposure, handling, restraint, or even the presence of a colonic temperature probe can cause significant increases in core temperature in these rats.