Region-specific expression of human α-Synuclein in different subpopulations of neurons. Triple immunofluorescent labeling reveals expression of transgenic hα-Syn (green channel) in different types of neurons. (A) hα-Syn immunoreactivity is evident in a subset (arrowheads) of dopaminergic neurons (TH, blue channel) in the glomerular layer (sgl), and occasionally (arrows) in GABAergic interneurons (GAD67, red channel) throughout the olfactory bulb. (B) A subset of neocortical hα-Syn-positive neurons (arrows) are immunoreactive for the interneuron marker GAD67 (red channel); however, this did not occur in the hippocampus (arrowheads) probably due to known low expression levels of GAD67 in some types of interneurons (C). Using ErbB4 immunoreactivity as an alternative marker for GABAergic neurons, we found hα-Syn expression in a subset of interneurons (arrows), but not in Iba1-immunoreactive microglia (arrowheads), in hippocampal area CA3 (D) and in the dentate gyrus (E). Abbreviations: dentate gyrus (DG), glutamic acid decarboxylase 67 kD (GAD67), tyrosine hydroxylase (TH), stratum plexiforme externum (spe), stratum oriens (so), stratum pyramidale (sp), stratum radiatum (sr), stratum moleculare (sm), stratum granulosum (sg), hilus (hi) cortical layer V and VI (V and VI), cornu ammonis area 1/3 (CA1/3). Scale bar = 50 μm.