Light micrographs demonstrate the localization of KCC2 in nondopaminergic cells of the rat SN. A, B, Low (A)- and high (B)-magnification micrographs illustrate the segregation of TH-immunolabeled neurons (brown) and KCC2-immunopositive dendrites (blue-black) in both the SNc (SNC) and SNr (SNR). Both somata and dendrites of the dopaminergic neurons are labeled for TH (arrows). KCC-2 was found only in the dendritic compartment of nondopaminergic cells (arrowheads). C, D, Double-immunofluorescent staining shows a mutually exclusive distribution pattern for TH and KCC2. It demonstrates that none of the TH-positive (green) dendrites or somata are outlined by KCC2 immunoreactivity (red). Scale bars, 25 μm.