Imaging Tobacco Smoking with PET and SPECT --  Behavioral Mechanisms Underlying Nicotine Reinforcement -- The Role of Mesoaccumbens Dopamine in Nicotine Dependence -- Nicotine Withdrawal -- Neurobiologal bases of cue- and nicotine-induced reinstatement of nicotine seeking -- Psychiatric disorders as vulnerability factors for nicotine addiction: What have we learned from animal models?.