Age differences in the body temperature response to restraint-cold stress.

Female Fischer 344 rats, 3, 11, and 24-months old were subjected to 3 hr of restraint-cold stress once each week for 4 weeks. Body (colon) temperature was recorded every 10 min during restraint and during postrestraint recovery until temperature returned to the prerestraint level. Thermoregulatory adaptation during consecutive restraint sessions was noted in 3- and 11-month-old rats but not in 24-month-old rats. Significant temperature recovery was accomplished after the second restraint session for 3- and 11-month-old rats, but this was not accomplished in the older 24-month rats until after four restraint sessions. The role of hypothermia in restraint-induced ulceration is questioned, especially as it pertains to elderly rats.