Expression of estrogen receptor-β in the postischemic monkey hippocampus

The molecular basis of estrogen-mediated neuroprotection against brain ischemia remains obscure. Here, we studied by immunohistochemistry the expression of estrogen receptor (ER) α and β in the hippocampal CA1 sector of postischemic adult macaque monkeys. ERβ was present in control CA1 pyramidal neurons, decreasing on day 4 after ischemia. In contrast, ERβ immunoreactivity increased remarkably in the radiate and molecular layers of CA1, where it was present in astrocytes and microglia. ERα was negligible in both control and postischemic monkeys. These results indicate that ERβ is the major receptor responsible for the direct estrogen actions on the monkey hippocampus, regulating glial response after ischemia.