Another three subjects (one nonsmoker and two smokers) were found to carry synonymous rare variants in the exon 5 cytoplasmic loop region. Similar to what was observed for the nonsmoker with the nonsynonymous rare variant, the nonsmoker who carried two synonymous rare variants (p.Pro451Pro and p.Pro554Pro) also had higher α4β2 nAChR availability in the cortical areas (11.9%), striatum (21.4%), and cerebellum (20.8%), than a group of four age-matched control nonsmokers (Figure 3A, subject 2 (S2)); while no difference was observed between the two smokers who carried the synonymous rare variants p.Phe326Phe and p.Leu520Leu and their age-matched control smokers.
