Abstract
The survival factor Bcl‐2 is a cyclic AMP response element‐binding protein (CREB) gene product implicated in mediating some of estrogen's effects on neuroprotection. Previously, we showed an effect of estradiol benzoate (E) on numbers of neuron‐specific protein (NeuN)‐ and phosphorylated CREB (pCREB)‐positive cells in medial (MeA), but not central (CeA), amygdala of ovariectomized rats. To determine whether these effects are accompanied by an E‐induced increase in Bcl‐2, we examined the effects of E on levels of Bcl‐2 protein and mRNA in MeA and CeA of ovariectomized rats treated with E regimens resulting in moderate (2.5 μg E for 4 or 14 days) or high (10 μg E for 14 days) plasma estradiol levels. As a physiological control, we showed that all E treatments increased uterine wet weight relative to vehicle; 10 μg E for 14 days also increased uterine weight compared with that seen with lower E levels. Western blot analysis revealed that all E groups displayed an increase in uterine Bcl‐2 protein levels compared with vehicle. We found that 2.5 μg and 10 μg E for 14 days increased levels of Bcl‐2 gold immunolabeling compared with vehicle and 2.5 μg E for 4 days in MeA, but not CeA. We measured Bcl‐2 mRNA levels in vehicle and 2.5 μg E‐treated 14‐day groups. There was a significant increase in Bcl‐2 mRNA levels in MeA, but not CeA, of E‐treated ovariectomized rats compared with vehicle controls. The E‐induced increase in protein and mRNA levels of Bcl‐2 in MeA may be important for neuroprotection in this region. © 2008 Wiley‐Liss, Inc.