Basic and clinical psychopharmacology of nicotine.

Nicotine acts on nearly every physiological system of the human body. While the actions of nicotine on the autonomic nervous system may be of interest in understanding possible deleterious long-term effects of smoking on the cardiovascular system, the actions of nicotine on the central nervous system are of the most interest in understanding why people smoke. Many studies of the effects of nicotine on human cognitive function have been performed. Improvement in attention, learning, reaction time, and problem solving have been reported. However, most of the results are inconclusive owing to methodologic problems. Whether the enhanced performance observed after smoking is attributable to relief of symptoms of abstinence or to a primary effect of nicotine on the brain is not clear. The pharmacodynamic effects of nicotine must be considered in the design of studies of the effects of nicotine on human performance. It is not known if the effects of nicotine on performance are subject to tolerance. The facilitation of performance, perceived as a reinforcement, may tend to lessen throughout the day, as do other effects of nicotine. Studies of chronic tolerance to the behavioral effects of nicotine are needed; comparisons between regular smokers and occasional smokers may be helpful. At present, the facilitatory actions of nicotine on human performance have been explained in terms of arousal. However, nicotine actions cannot be explained in terms of this single concept. Different processes, including attention, stimulus evaluation, and response selection, appear to be involved in the effect of nicotine on human information processing. Finally, one must consider that the predominant effects of nicotine may differ among individuals, as different people smoke for different reasons, and the motives for (rewards of) smoking may vary in different situations.