AR and ERα immunoreactivity in dopamine neurons of the adolescent male rat substantia nigra. Midbrain tissue sections (approximately bregma −5.52) were probed with antibodies raised against tyrosine hydroxylase (TH) and either androgen receptor (left column) or estrogen receptor α (right column). Blue staining indicates DAPI labeled nuclei (top row). Arrowheads indicate TH positive neurons (green) that are also immuno-positive for sex steroid receptors (red). Neurons with co-localized sex steroid receptors and TH immunostaining appear yellow in the merged images (bottom row, arrowheads). Stars indicate TH negative, sex steroid receptor positive (red) neurons, solid arrow indicates a TH positive, ERα negative neuron. Scale bar=20 μm.