Protective effects of estrogen against experimental stroke and neuronal ischemic insult are well documented, but it is not known whether estrogen is a potent mitogen in neuronal cell expressing estrogen receptors (ERs) to prevent ischemic injury.Estrogen actions on brain cells occur through at least two types of intracellular receptors as well as other mechanisms for which receptor sites are not yet clearly identified.Recent reports indicated that ER-c36, a novel subtype of ERα, was related with estrogen-dependent tumorigenes in ERnegative breast cancer cells and mediated membrane-estrogen mitogenic signaling at low level of 17β-estradiol (E2).PC 12 cell, a estrogen receptor (ER)-negative neuronal cell line, is a cell line derived from a pheochromocytoma of the rat adrenal medulla, and stopped dividing and terminally differentiate when treated with nerve growth factor,which makes it makes it useful as a model system for neuronal differentiation.Here, we investigated whether low concentration E2 protects PC12 cells against ischemic damage by ER-α36.To test this, an in vitro ischemic model,oxygen-glucose deprivation (OGD)/reperfusion, was applied to immortalized rat pheochromocytoma PC12 cell line (PC 12 cell).OGD/reperfusion-induced cell death was prevented by long-term (48 h), pretreatment with 1 nM of E2.Furthermore, Knockdown of ER-α36 abrogated the biphasic estrogen protection in these cells.Protective effects of E2 on PC12 cell viability were mimicked by a agonist specific selective for ER-c36, IC162 at 10 nM,not at 1 μM, also, activated ER-α36 promoter activity through low concentration E2 and IC162.In addition, E2significantly decreased mitochondrial superoxide and preserved mitochondrial membrane potential and mainly counteracts the effect of apoptosis.All of the E2 effects were blocked by the ER antagonist, ICI-182,780.These findings suggested that low level of estrogen could preserve PC12 protection against ischemic injury through ERα-36-mediated mechanisms.