Distribution of Corticosteroid Receptors in Mature Oligodendrocytes and Oligodendrocyte Progenitors of the Adult Mouse Brain

The expression of glucocorticoid receptors (GRs) was investigated immunohistochemically in two different lineages of oligodendrocytes, using carbonic anhydrase (CA) II and neuron glial antigen (NG) 2 as markers of mature oligodendrocytes and oligodendrocyte progenitors, respectively. We focused on the gray matter regions, including CA1, CA3 and the dentate gyrus of the hippocampus, the primary somatosensory cortex barrel field and the basolateral amygdala, and the white matter regions, including the corpus callosum, external capsule and fimbria of the hippocampus. More than 80% of CAII-immunoreactive (IR) cells and more than 95% of NG2-IR cells expressed GRs in various regions of the brain. In contrast, neither CAII-IR cells nor NG2-IR cells expressed mineralocorticoid receptors (MRs) in the same regions. The intensity of GR expression was drastically reduced in CA II-IR cells and NG2-IR cells in the same regions in adrenalectomized mice. Finally, steroid receptor co-activator (SRC)-1 and p300, both of which are cofactors for GR, were expressed in the gray and white matter regions in NG2-IR cells, but not in CAII-IR cells. These results suggest that the expression of GRs in oligodendrocytes and their progenitor cells mediates several functions in vivo, including differentiation and myelination, as a major target of glucocorticoids and their cofactors.