To our knowledge, this is the first study describing increased dopamine innervation outside the basal ganglia circuit in the MPTP model.29 The net increase in length and density of DAT‐ir axons in R may be because of sprouting, a phenomenon that has been described in the striatum of MPTP models and patients with PD.22, 30, 31, 32 However, we did not observe morphological traits suggesting the presence of new branches on DAT‐ir axons of the R nucleus in our MPTP‐treated macaques. Here, SLC6A3 is linked to Parkinson disease.