A total of 139 subjects (92 smokers and 47 non-smokers) participated in [123I]5-IA SPECT scans. Subjects had no history of psychiatric, neurological, or medical disease and no history of drug or alcohol dependence except for ND. Smokers were required to abstain from smoking for 7-9 days prior to their SPECT scans and were instructed that they could not use any forms of nicotine replacement therapy or medication throughout the study. Abstinence from smoking was confirmed by urine cotinine and breath carbon monoxide levels monitored daily for the first 8 days of smoking cessation and a minimum of twice weekly thereafter. Subjects were administered equivalent doses of [123I]5-IA as a bolus to constant infusion at a ratio of 7.0 for 8 hours, and were imaged at equilibrium, between 6 and 8 hours. Detailed methods for the imaging study were described previously (25). Written informed consent was obtained from all participants.
