Cold tolerance: behavioral differences following single or multiple cold exposures

Previous research has demonstrated that repeated exposure to cold water results in cold tolerance. The present set of experiments examined whether spontaneous behavioral activity and the rate of rewarming differed between cold tolerant and nontolerant rats. Animals receiving six cold exposures (one per day) were compared to subjects receiving a single cold exposure but cooled to match the final day temperature of the six-exposure group. Immediately following the final or only cold exposure, activity was measured by an activity monitor (Exp. 1) or was videotaped and scored by an independent observer (Exp. 2). Furthermore, rats' temperatures were monitored for 90 min (Exp. 2) and 60 min (Exp. 3) following the activity measurement. The results indicated that cold-tolerant rats exhibited activity similar to normal, noncooled subjects, whereas the activity in the single exposure group was impeded. Moreover, rats in the multiple exposure groups rewarmed more quickly than subjects in the single exposure condition. The third experiment also examined if the procedures of Experiments 1 and 2 resulted in associative cold tolerance. Experiment 3 replicated earlier findings, which have shown that exposure to the same cold stimulus in an altered context resulted in a loss of tolerance. These findings suggest that the processing of contextual stimuli is necessary for the acquisition of cold tolerance and that behavioral activity and rewarming rates can be used as alternative measures of cold tolerance.