Localization of AhR and TH proteins in the rat brain. Immunohistochemical staining with anti-AhR and/or TH antibodies was performed on formalin fixed paraffin embedded coronal brain sections prepared from 10-week-old rats. Signals of AhR and TH proteins were developed using DAB/H2O2 (light brown) and ALP-RED (light red), respectively. Sections were counterstained with hematoxylin. (A) AhR protein was detected in the substantia nigra pars compacta (SNc) in the midbrain (black arrow), hippocampus, and dentate gyrus. Bar = 1 mm. (B) TH protein was detected in the SNc (black arrow) and hypothalamic area. Bar = 1 mm. (C) Double staining revealed colocalization of AhR and TH proteins in SNc (black arrow). Bar = 1 mm. Magnified (× 400) views of the SNc region were inset in each panel. Bar = 50 μm.