Normobaric hypoxia and anemia stimulate EPO synthesis in brain pericytes. Shown are the results of multiplex RNA FISH studies for Epo and Pdgfrb transcripts using formalin-fixed, paraffin-embedded brain tissue sections from wild-type mice exposed to normobaric hypoxia (8% O₂ for 24 hours) or after phlebotomy (average Hct: 20.7%). (A) (Left) Representative image of a striatal section (ST) containing pericytes (white arrows) that coexpress Epo (green signal) and Pdgfrb transcripts (red signal) and nonpericytic Epo⁺ cells (white arrowhead). Nuclei are stained with DAPI (blue fluorescence). (Right) Representative image of a hippocampal section (HP) containing pericytes (white arrows) that coexpress Epo (green signal) and Pdgfrb transcripts (red signal) and Pdgfrb⁻Epo⁺ cells (white arrowhead). Nuclei are stained with DAPI (blue signal). (B) (Upper) Percentages of Pdgfrb⁺ cells that coexpress Epo (white bar) or Epo⁺ cells that coexpress Pdgfrb transcripts (black bar) in striatum (ST), hypothalamus (HYT), corpus callosum (CC), cortex (CTX), and hippocampus (HP) from wild-type mice exposed to normobaric hypoxia (8% O₂ for 24 hours) (n = 3). (Lower) Percentages of Pdgfrb⁺ cells that coexpress Epo (white bar) or Epo⁺ cells that coexpress Pdgfrb transcripts (black bar) in striatum (ST), hypothalamus (HYT), corpus callosum (CC), cortex (CTX), and hippocampus (HP) from phlebotomized wild-type mice (n = 3).