these results. First, at 1 day of abstinence there is still residual nicotine, or a pharmacologically active metabolite of nicotine, such as cotinine or nornicotine present in the brain that interferes with radiotracer binding, thus leading to the appearance of lower β2*-nAChR availability. Second, the normalization of the β2*-nAChR is prolonged, requiring up to 6-12 weeks of abstinence to fully return to nonsmoker levels.
