HEAT-INDUCED ACUTE HYPERTHERMIA RESULTS IN A REVERSIBLE DEPRESSION OFCOLD DEFENSE IN THE RAT (RATTUS-NORVEGICUS)

1. Adult female Wistar rats were made hyperthermic (colonic temperatur e, T-c, of 41 to 42 degrees C for 60 min) by external heating and then tested for their autonomic cold defence (cold exposure of 15 degrees C for 45 min) either immediately after hyperthermia or 2 h later. 2. C ompared with cold defence of normothermic controls, hyperthermic rats showed a decreased cold-induced thermogenesis and a fall in the body t emperature threshold for its elicitation, both resulting in a greater reduction in T-c. 3. Two to three days after hyperthermia all measured parameters of cold defence returned to the normal values observed bef ore hyperthermia. 4. The reversible depression of cold defence demonst rated by the present study can be interpreted as a sign of adaptive mo dification in thermoregulation, probably helping recovery from hyperth ermia. Copyright (C) 1996.