engleski

Chronic stress influences level of ObR and ER-beta in the brain of adult female Sprague-Dawley rats

Chronic stress causes various molecular changes for the sake of homeostasis maintenance. It can ultimately lead to life threatening disorders such as cardiovascular and metabolic disease characterized by high blood pressure, obesity and hormonal dysfunction. In order to understand the impact of chronic stress on the level of leptin receptor (ObR) and steroid hormone receptors in the brain, female Sprague- Dawley rats were exposed to different stressors within 3 stress sessions followed by 2-week pause inbetween.Overall 48 4-months-old rats were divided in non-ovariectomized (NON-OVX) and ovariectomized (OVX) group. These groups were subdivided in chronic (S) and control group (C). Controls were exposed to the same conditions as stress groups, but without stressor. The brains were collected after the last stress session and free-floating immunohistochemical staining was performed using ObR, progesterone (PR) and estrogen-β receptor (ER-β) antibodies. The level of receptors expression was analyzed in hippocampus (Hipp), hypothalamic regions (HTH) and in cortical areas (Ctx). After exposure to stress ObR expression in NON-OVX-S decreased in all brain regions except in Hipp, but in OVX-S increased. Still these changes did not reach significance. There were no significant changes in PR expression. Upon stress, level of ER-β significantly decreased in OVX-S in HTH (S vs. C, P=0, 05) but we also observed significantly lower levels of ER-β in Hipp (NON-OVX-S vs. OVX-S, P=0, 017).Upon exposure to chronic stress NON-OVX-S decreased ObR expression in HTH involved in appetite control and increased in Hipp. Therefore, in case of chronic stress these animals will be less susceptible to leptin and may gain weight. They will also have estrogen neuroprotection particularly important for Hipp. In case of ovary removal, upon exposure to stress OVX animals increase ObR level in HTH and Hipp but fail to increase ER-β like NON-OVX-S. Thus OVX become more susceptible to leptin and at the same time lose estrogen neuroprotection what endangers overall stress resistance.

Brain; Chronic Stress; Leptin Receptor; Estrogen-beta Receptor

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