Total cellular AT1 in SN dopamine neurons. (A-F) Immunodetected AT1 in the SN matrix (calbindin-rich area) from neurologically intact patients (AMC), from prePD patients, and from PD patients. (G and H) show an example of AT1 expression in nigrosome 1 (calbindin-poor area). Scale bar in (A-F) is 20 μm and in (G and H) is 10 μm. (I) Quantification of AT1 immunofluorescence in TH-immunopositive dopamine neurons in the SN matrix and in nigrosome 1 as well as images (A-F) clearly illustrate dramatic reduction in the AT1 expression in nigral dopamine neurons (most profound in the matrix) as disease progresses. In panel (I), a single asterisk identifies this AT1 immunofluorescence intensity measure as significantly different from the intensity measures in the other two matrix groups. The double asterisk indicates a significant difference between nigrosome 1 of AMC and PD.