Control of behavior by intravenous nicotine injections in human subjects.

Results are summarized from a series of studies in which procedures used to assess the reinforcing and aversive properties of drugs in animals, were extended to a human paradigm. Human volunteers were tested using drug self-administration and avoidance procedures, whereby pressing a lever under a fixed-ratio schedule resulted either in the IV injection of nicotine or in the avoidance of programmed IV injections of nicotine, respectively. Nicotine was found to maintain responding that produced its injection under certain conditions, and to maintain responding that avoided its injection under other conditions. Nicotine produced the same constellation of stimulus properties whether functioning as a positively or negatively reinforcing event. These functional properties of nicotine may be determined by schedule of access to nicotine, dose of nicotine, and past history of the subject.