In summary, our data extend the findings of previous studies8, 18 which showed that the upregulation of the β2*-nAChR in recently abstinent tobacco smokers was temporary and could be measured with [123I]5-IA SPECT imaging. Specifically, we demonstrate that the normalization of upregulated β2*-nAChRs in tobacco smokers during smoking cessation is prolonged. This is consistent with the clinical course of tobacco smoking in which craving, withdrawal symptoms, and risk for relapse are prolonged. The variation between individuals in the magnitude of upregulation and rates of normalization may ultimately be used to delineate subgroups based on genetics, sex, and comorbid mental illness and thus to target treatment medications.
