Erythropoietin immunoreactivity in cortex and hippocampus following intermittent and sustained hypoxic exposures in mice. (A). Composite reconstructions of immunohistochemically processed brain sections double labeled for EPO (red fluorescence) and NeuN (green flurorescence) immunoreactivity after IH (left) and SH (right). (B). Illustrative examples of EPO and NeuN labeling of hippocampus and frontal cortex after IH or SH exposures.