Recently, Kordower et al. (2013) described in detail the integrity of nigrostriatal dopaminergic connectivity using tyrosine hydroxylase (TH) and dopamine transporter (DAT) as markers for dopaminergic function: In PD, dopaminergic fiber density in the dorsal putamen was rapidly and severely decreased leading to a virtually complete neuritic loss at 4 years after the clinical diagnosis compared to controls. Here, SLC6A3 is linked to Parkinson disease.