The characteristics of nongenomic action are (1) rapid onset, (2) cellular signaling activations, and (3) membrane ER activation [27,28]. Reportedly, estrogen rapidly enhances Arc expression and synaptic plasticity via ER-,MAPK-, and PI-3K-dependent pathways indicating non-genomic action of estrogen [4]. In the present study, the extranuclear localization of ER_in SH-SY5Y cells, indicating a membrane-bound ER_, is in agreement with previous studies in hippocampal neurons [13].