Critical temperature for instrumental response acquisition in hypothermic rats

Abstract

Fifty-one previously untrained adult white rats were cooled to colonic temperature of 18.5 C and were rewarmed to various body temperatures between 23 and 31 C. After their body temperature stabilized at a chosen level, rats were placed in a chamber with the possibility of using a lever-activated heat reinforcement apparatus. The temperature of the chamber was 2 C. Each experiment lasted 180 min. During this time the rats either started to press the lever steadily for external heat or at the end of this experiment they became even more hypothermic. In a group of 41 rats kept at a body temperature of 25 C or above, 38 animals used the simple heat reinforcement apparatus and responded effectively, thus rewarming themselves to euthermia. Animals at a higher body temperature acquired the response earlier than animals whose body temperature was lower. When the body temperature was 25 C or below, the rats failed to acquire the response. Thus it appears that body temperature of 25 C is a critical body temperature for this simple response acquisition. behavioral temperature regulation; body temperature; heat reinforcement; hypothermia; learning; performance Submitted on April 1, 1965