Controls for RNAscope probe specificity. A–D, Validation of the RNAscope Fluorescent Multiplex assay using positive and negative control probes, provided by the manufacturer. Coronal brain slices were hybridized with the RNAscope positive control probes (A, C) and negative control probes (B, D). Images were taken from the cortex (A, B) and the basal ganglia (C–E). E, In the basal ganglia, cells express exclusively either PV mRNA or p75 mRNA.