Striatal Dopamine D2/D3 Receptor Availability Varies Across Smoking Status.

To assess how tobacco smoking status affects baseline dopamine D2/D3 (D2R) receptor availability and methylphenidate-induced dopamine (DA) release, we retrospectively analyzed D2R availability measures of 8 current smokers, 10 ex-smokers, and 18 nonsmokers who were scanned with positron emission tomography and [11C]raclopride, after administration of an injection of placebo or 0.5 mg/kg i.v. methylphenidate. There was a significant effect of smoking status on baseline striatal D2R availability; with current smokers showing lower striatal D2R availability compared with nonsmokers (caudate, putamen, and ventral striatum) and with ex-smokers (caudate and putamen). Baseline striatal D2R did not differ between nonsmokers and ex-smokers. The effect of smoking status on methylphenidate-induced DA release tended to be lower in smokers but the difference was not significant (p=0.08). For behavioral measures, current smokers showed significantly higher aggression scores compared with both nonsmokers and ex-smokers. These results suggest that with abstinence ex-smokers may recover from low striatal D2R availability and from increased behavioral aggression seen in active smokers. However, longitudinal studies are needed to assess this within abstaining smokers.