Extranuclear estrogen receptor beta immunoreactivity is on doublecortin-containing cells in the adult and neonatal rat dentate gyrus

In adult female rats, estrogen receptor (ER) activation, particularly of ERβ, promotes hippocampal neurogenesis. We previously reported that extranuclear ERβ immunoreactivity (ir) in adult rats is on cellular profiles in or near the granule cell layer, which is the location of newly generated cells. During development, cells in or near the granule cell layer transiently express high levels of estrogen binding and nuclear ERs. Thus, we sought to determine if extranuclear ERβ is in newly generated cells in adult and neonatal rat dentate gyrus. Sections from the dentate gyrus of adult proestrus or postnatal day 7 and 14 female rats were dual-labeled for ERβ and the new-cell marker doublecortin (DCX) and examined by electron microscopy. DCX-containing neurons were found in the subgranular hilus in adult rats and were more widespread throughout the granule cell layer and hilus of neonatal rats. In both adults and neonatal rats, ERβ immunoreactivity was found in a subset of DCX-labeled neurons. Electron microscopic examination of the adult dentate gyrus revealed that most perikarya with DCX-ir had the morphological characteristics of granule cells, although a few resembled interneurons. Dendrites with DCX-ir also were observed. In both adults and neonates, DCX-labeled neuronal perikarya and dendrites contained ERβ-ir; ERβ-ir usually was aggregated near the plasma membrane, mitochondria or endoplasmic reticula. ERβ-ir was in glial profiles that apposed DCX-labeled perikarya and dendrites. These findings are consistent with data showing that estrogens can exert non-genomic effects directly and indirectly on newly generated cells in neonatal and adult rat dentate gyrus.