Learned anticipatory rise in body temperature due to handling

Hyperthermia produced by handling becomes evident at the initial daily measurement if temperature is measured at a consistent time. This hyperthermia may be a learned effect occurring in anticipation of handling. In Experiment One male Wistar rats were either unhandled or had their temperatures measured daily in the dark or the light part of the day. All animals had their temperatures measured on Day 29, in the dark. Rats usually tested in the dark were hyperthermic, 38.8 degrees C, relative to rats previously handled only in the light, 38.1 degrees C, and to naive rats, 37.9 degrees C. In Experiment Two rats were handled three times daily in either the light or the dark. On Day 9 each group was divided in two, and temperatures were measured at either the usual time or at the other time. Rats tested at their usual time were hyperthermic, relative to rats normally handled in the other part of the cycle. This suggests a conditioned hyperthermia occurs in response to stimuli predictive of handling.