There is abundant evidence that the
dopamine (DA) neurons that project to the nucleus accumbens play a central role in neurobiological mechanisms underpinning
drug dependence. This chapter considers the ways in which these projections facilitate the addiction to
nicotine and tobacco. It focuses on the complimentary roles of the two principal subdivisions of the nucleus accumbens, the accumbal core and shell, in the acquisition and maintenance of
nicotine-seeking behavior. The ways in which tonic and phasic firing of the neurons contributes to the ways in which the accumbens mediate the behavioral responses to
nicotine are also considered. Experimental studies suggest that
nicotine has relatively weak addictive properties which are insufficient to explain the powerful addictive properties of tobacco
smoke. This chapter discusses hypotheses that seek to explain this conundrum. They implicate both discrete sensory stimuli closely paired with the delivery of tobacco
smoke and contextual stimuli habitually associated with the delivery of the
drug. The mechanisms by which each type of stimulus influence
tobacco dependence are hypothesized to depend upon the increased DA release and overflow, respectively, in the two subdivisions of the accumbens. It is suggested that a majority of
pharmacotherapies for
tobacco dependence are not more successful because they fail to address this important aspect of the dependence.