Abstract
Estrogen receptors (ERs) are widely expressed in the brain, where estrogen modulates central nervous functions. In the present study, we examined whether estrogen alters the stress-induced c-Fos expression through ER α in the brain of ovariectomized (OVX) rats. Female rats aged 9wk were divided randomly into three groups: sham-operated (S), OVX plus placebo-treated (P) and OVX plus estrogen-treated (E) groups. The rats in the P or E group were implanted with pellets containing either placebo or 17 b-estradiol. After 4wk, each group of rats underwent cage-switch for 30 min and was sacrificed at 60 min after the cessation of the stress. The rats were perfused, and the brains were immunohistochemically processed for c-Fos and ER α. The cage-switch stress significantly increased the number of c-Fos positive cells in the paraventricular hypothalamic nucleus (PVN), arcuate hypothalamic nucleus, medial amygdaloid nucleus, dorsomedial hypothalamic nucleus (DMD), locus coeruleus (LC) in the P and E groups, but not in the S group. However, the numbers of c-Fos positive cells in LC, PVN and DMD were lower in the E group than the P group. Moreover, ER α positive cells were observed in PVN and LC in the both groups, though the number of these cells were higher in the P group. These findings suggest that estrogen would affect stress-induced neuronal activation at least partly through ER α. [J Physiol Sci. 2007;57 Suppl:S193]
