STIMULUS CONDITIONS INFLUENCING THE DEVELOPMENT OF TOLERANCE TO REPEATED COLD-EXPOSURE IN RATS

Tolerance to an environmental cold challenge in rats is eliminated whe n cold exposure occurs in a context different from the adaptation cont ext, indicating that learning mechanisms play a role in; thermoregulat ion (Riccio, MacArdy, and Kissinger, 1991). This finding, analogous to outcomes obtained with drug tolerance; was investigated in the presen t study. Experiment 1 demonstrated that a change in both proximal and distal contextual cues disrupts an established cold adaptation, an out come consistent with the view that associative processes contribute to the tolerance. In Experiment 2, although cold tolerance persisted ove r a 7-day retention interval, the disruption of tolerance by a shift i n context was attenuated with the delay of testing. This finding sugge sts that the precise stimulus attributes of the context were forgotten over the interval. Experiment 3 demonstrated that cold-tolerance disr uption is due to the actual change in context and not to novelty of th e test context. Experiment 4 showed that changing the context associat ed with each cold exposure impaired the development of tolerance. The results of these experiments provide additional evidence that cold tol erance is regulated at least partially by associative learning process es.