SLC6A4 and Parkinson disease: Significant reductions of serotonin transporter (SERT) binding, a measure of serotoninergic terminals, are reported in several brain areas of PD participants with positron emission tomography (PET) using the selective SERT ligand [11C]-3-amino-4-(2-dimethylaminomethyl-phenylsulfanyl)-benzonitrile ([11C]DASB) [27], [28].