Differential Expression of Estrogen Receptors in Two Hippocampal Regions During the Estrous Cycle of the Rat

Abstract

In the hippocampus, estrogens increase dendritic arborization, longterm potentiation, neuroprotection, and participate in many functions related with learning, memory, and affective behaviors. The presence of both estrogen receptors alpha (ERa) and beta (ERb) isoforms has been described in the hippocampus where they play different physiological roles. The aim of this study was to investigate, by using both techniques immunohistochemistry and Western Blot, the expression pattern of ERa and ERb in the hippocampus of the rat along the estrous cycle. Western blot analysis was used to confirm the specificity of the antibodies used against ERa and ERb and its relative content in the hippocampus. Results from immunohistochemical studies indicate that ERb expression increased more than the ERa in CA1 and CA3 regions during all phases of the estrous cycle. ERb immunoreactivity was mainly located in the nucleus and predominantly expressed in CA1 during estrous and metestrus, and in CA3 during diestrus. ERa was more abundant during estrous in comparison to other phases of the cycle in CA1 region, while it was more abundant during metestrus in CA3. Interestingly, the immunolocalization of ERa subtype was both cytoplasmic and nuclear. The overall results indicate that there is a differential expression, cellular localization, and distribution of both ER subtypes in CA1 and CA3 regions, suggesting different roles for these two receptors in the hippocampus along the estrous cycle. Anat Rec, 294:1913Rec, 294: -1919Rec, 294: , 2011. V V C 2011 Wiley-Liss, Inc.

Mechanisms of estradiol in fear circuitry: implications for sex differences in psychopathology

“…51,55 Regarding the vmPFC, both ERα and ERβ have been detected in the rat IL and prelimbic cortex. 56, 57, 58 A summary of relative receptor distribution within the fear extinction network is illustrated in Figure 3.…”

“…E2 receptors exhibit sensitivity to estradiol fluctuations, with expression and cellular localization varying across the phases of the rat estrous cycle in the hippocampus 57 and hypothalamus. 60 In the cornu ammonis 1 (CA1) subregion of the hippocampus, for instance, ERα expression correlates with serum estradiol levels and shows greatest expression during estrus, whereas ERβ is upregulated during both estrus and metestrus phases.…”

“…60 In the cornu ammonis 1 (CA1) subregion of the hippocampus, for instance, ERα expression correlates with serum estradiol levels and shows greatest expression during estrus, whereas ERβ is upregulated during both estrus and metestrus phases. 57 In addition, ERα localizes in the CA1 cytoplasm and translocates to the nucleus during diestrus, whereas ERβ localizes in the nucleus throughout the estrous cycle. 57 Halting E2 production through ovariectomy causes both ER downregulation and desensitization, 61 suggesting that circulating E2 preserves ER density.…”

Activation of the G protein-coupled estrogen receptor, but not estrogen receptor α or β, rapidly enhances social learning

“…Specific ER expression in brain regions important for the STFP therefore likely dictate whether 17␤-E2 enhances social learning or not. As ER expression changes over the estrous cycle (Mendoza-Garcés et al, 2011), this may explain when and how strongly 17␤-E2 affects social learning in females and why social learning is affected by the phase of the estrous cycle . Further research is necessary to explore possible additive effects of ER activation on the STFP.…”

Fetal growth restriction alters hippocampal 17-beta estradiol and estrogen receptor alpha levels in the newborn male rat

“…Of note, we have previously demonstrated that FGR affects the newborn rat hippocampus in a region-specific manner, FGR decreased neuronal numbers and subregional volumes in the CA1 and DG volumes in FGR males but not in the CA3 region [Fung et al 2012]. Region-specific changes in ERα expression in the hippocampus are not only limited to FGR, but also occur in kainate-induced hippocampal injury [Vanoye-Carlo et al 2009] and varies throughout the estrous cycle [Mendoza-Garces et al 2011]. Interestingly, the observed region-specific reduction in apparent ERα staining levels using immunohistochemistry was observed in the absence of measurable changes in whole hippocampal ERα levels by Western blotting.…”