Environment-specific tolerance to nicotine.

Research has shown that tolerance to the behavioral effects of numerous drugs is mediated by learning. The present study was designed to test whether animals develop tolerance to the antinociceptive effects of nicotine, and whether these effects are also learned. Rats were given dally injections of nicotine in the same environment. After each injection, the latency of tail withdrawal from a hot water bath was measured. This was continued until they were tolerant to the drug: i.e., their response latencies did not differ from animals repeatedly given saline. The role of learning in nicotine tolerance was assessed by changing the environment in which they received nicotine on the day after tolerance was achieved. When the drug environment was changed, the animals recovered the full dose effect of nicotine on tail-flick latencies. These results show that tolerance develops to nicotine's antinociceptive effects, and that this tolerance also may be influenced by learning.