抄録
Our recent study showed that chronic estrogen replacement in ovariectomized rats has the beneficial effect of suppressing stress-induced cardiovascular responses. However, the mechanisms involved are unknown. We used mild psychological stress evoked by cage-switch, and addressed the hypothesis that estrogen alters the stress-induced expression of c-Fos, a marker for neuronal activation in response to stress, in the brain of ovariectomized rats. Adult female rats were randomly assigned placebo-treated (P), estrogen-treated (E) and normal female (C) groups. The P and E groups were ovariectomized and implanted with pellets containing either placebo or 17 b-estradiol (1.5 mg/60-day release). Each group rat underwent cage-switch or immobilization stress for 30 min and was sacrificed at 60 min after the cessation of the stress. The rats were perfused, and the brains were extracted and immediately frozen. Stress-induced c-Fos expression was analyzed quantitatively by immunohistochemistry. C-Fos expressions were detected in the hypothalamic paraventricular nucleus (PVN), amygdala and arcuate nucleus in the rat forebrain subjected to cage-switch stress. In PVN and amygdala, c-Fos expression changed depending on the type of the stresses. Moreover, c-Fos expression in these regions tended to decrease in the E group compared with P group. These findings suggest that estrogen affects c-Fos expression induced by the mild psychological stress in rat forebrain. [Jpn J Physiol 54 Suppl:S244 (2004)]
