Abstract
<title>Abstract</title> <p>Oligodendrocytes are metabolically active glial cells that support axonal function and maintain myelin integrity, processes associated with high iron demand. However, it remains unclear whether intracellular iron organization varies across oligodendrocyte subtypes and brain regions. Here, we examined subtype-specific and region-dependent patterns of intracellular iron compartmentalization in the adult rat brain. Using histochemistry, transmission electron microscopy, and electron spectroscopic imaging, we analyzed oligodendrocytes in the dorsal striatum and cerebellar white matter. Iron distribution differed across both subcellular compartments and oligodendrocyte subtypes. Dark oligodendrocytes exhibited the highest iron signal, predominantly localized to mitochondria and endomembrane systems, whereas medium-density and light oligodendrocytes showed lower levels. Regional differences were also evident, with higher iron content in cerebellar white matter corresponding to an increased proportion of dark oligodendrocytes. These findings indicate that intracellular iron compartmentalization is linked to oligodendrocyte subtype identity and regional context. Our results identify iron microarchitecture as a structural correlate consistent with metabolic specialization and provide a framework for understanding regional brain iron distribution.</p>