Instrumental Acquisition in Rats After Twelve Exposures to Deep Hypothermia. ∗

Summary

Hypothermic rats acquire a simple technique for obtaining external heat more quickly at a body temperature of 29-30°C than at other decreased body temperatures. When the body temperature is decreased below 25°C the latency period for acquisition of the new behavior is much extended and the performance is rarely observed during a period of 180 minutes. However, when rats are exposed to hypothermia several times prior to the response acquisition experiment they are able to respond steadily not only at a body temperature of 25°C but even at temperatures between 22° and 25°C. While all hypothermia-adapted animals thus responded at these body temperatures (22.2-24.7°C), 5 out of 7 non-adapted animals failed to do so. The performance latency time of the 2 non-adapted rats which eventually performed was longer than that of any hypothermia-adapted rat. It is concluded that previous exposure to hypothermia (“adaptation to hypothermia”) enhances the response acquisition ability of rats at low body temperatures.