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This study examined the number of conditioning trials necessary to produce associative nicotine tolerance and the changes in corticosterone levels during the procedures . Six independent groups of rats (N = 355 ) were run through tolerance acquisition procedures for 1 , 5 , or 10 conditioning sessions . Treatment groups were comprised of animals that received nicotine -environment pairings , animals that received nicotine explicitly unpaired with the drug administration environment , and control groups that received either saline throughout or no treatment . Three of the groups were tested for nicotine -induced analgesia using the tail -flick and hot -plate assays , and three groups were blood sampled after either nicotine or saline injection . Pairing of environment with nicotine produced greater tolerance for rats after 5 conditioning sessions in the tail flick and after 10 conditioning sessions in the hot -plate . Corticosterone levels were elevated in all rats given nicotine . Rats that received the nicotine -environment pairing showed a conditioned release of corticosterone in response the environment after both 5 and 10 conditioning sessions . |
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