ROLE OF CONTEXTUAL STIMULI IN TOLERANCE TO STRESS-INDUCED ANALGESIA

The present study was conducted to determine whether tolerance to stress-induced analgesia was mediated by contextual cues. Following baseline measurement of analgesia using a tail curl test, rats were exposed to nine sessions of 30 min of intermittent inescapable shock (tolerance development phase) in which one half of the rats began in context A and the other half in context B. A tail-curl test immediately followed each shock session. On the 10th day, 4 days after tail-curl latencies returned to baseline, the contexts were switched, and the rats were exposed to the same shock parameters as before. The results revealed a significant increase in tail-curl latency when the context was switched compared with the last day of the tolerance development phase. These data suggest that tolerance to stress-induced analgesia may at least in part be associatively mediated by the context.