This study is also consistent with a previous study18 demonstrating that higher β2*-nAChR availability in recently abstinent tobacco smokers compared to nonsmokers is temporary. In the previous study in men, β2*-nAChR availability decreased to nonsmoker levels in some subjects by 21 days of abstinence. Specifically, compared to nonsmokers, smokers had significantly lower β2*-nAChR availability at 4 hr of abstinence, significantly higher β2*-nAChR availability at 10 days of abstinence, and similar β2*-nAChR availability at 21 days of abstinence. Additionally, they reported significantly lower β2*-nAChR availability at 21 days of abstinence compared to 10 days of abstinence. One difference is that the previous study18 had significantly lower β2*-nAChR availability in all regions at 4 hr of abstinence compared to the nonsmokers, while the current study reports lower thalamic but similar β2*-nAChR availability in the striatum, cerebellum and throughout the cortex compared to the nonsmoker group at 1 day of abstinence. This is interesting and likely due to high levels of residual nicotine or metabolites present in the brain at 4 hr of abstinence (versus ∼24 hours in the current study) resulting in
