CALB1 and Parkinson disease: Using semiquantitative immunohistofluorescence, we found that AT1 protein expression in dopamine neurons of the human substantia nigra is reduced with the disease progression from AMC → prePD → PD in the calbindin-rich matrix and in the calbindin-poor nigrosome 1, where we observed greater loss of TH-immunopositive dopamine neurons.