BODY-TEMPERATURE AND WHEEL RUNNING PREDICT SURVIVAL TIMES IN RATS EXPOSED TO ACTIVITY-STRESS

The relationship between restricted feeding, core body temperature (T- b), wheel running, survival, and gastric erosion formation was examine d in female rats exposed to activity-stress. Core body temperature and gross motor activity were telemetrically monitored in four groups of rats that had free access to running wheels and in one group that was not allowed to run on the wheels. Twenty-four hours prior to the onset of hypothermia and predicted mortality, different groups were left un disturbed, warmed with a heal lamp, denied access to running wheels, o r euthanized. Length of survival in wheel-running rats varied from 2 t o 12 days. During the first day of food deprivation, premorbid changes in the variability of T-b during the diurnal period and the mean numb er of wheel revolutions during the nocturnal period were strongly pred ictive of length of survival. Warming rats with a heat lamp or prevent ing rats from ever running on the wheel increased the length of surviv al and attenuated gastric erosion formation. only rats that were warme d had a greater likelihood of survival. Gastric pathology was also red uced in rats that were euthanized prior to becoming moribund. Rats tha t were left undisturbed or locked from the running wheel over the last 24 h of testing became moribund and had extensive gastric mucosal dam age. These results indicate that thermoregulatory disturbances induced by restricted feeding and not wheel running alone are critical in det ermining survival and the degree of gastric mucosal injury in rats exp osed to activity-stress. Results further suggest that predisposing fac tors may put some rats at risk for the development of activity-stress- induced mortality. (C) 1997 Elsevier Science Inc.