CUMS-induced Increase in ERα/ERβ Expression Is Associated...

1. Introduction Exposure to chronic stress acts as a risk factor as well as a precipitating agent for mood and anxiety disorders, and such stress in early life manifests itself in common mental disorders in adults [1, 2]. Majority of studies focus on the manifestation of stressful experiences in young, but there are less reports on the immediate consequences of early-life stress. Such stress activates neuroendocrine adaptive responses to cope with consequent crisis. However, due to prolonged or chronic stress, these neuroendocrine responses turn maladaptive and contribute to a phenomenon known as allostatic load [3]. These stressful events act as predisposing factors in the development of psychiatric disorders and anxiety- and depression-associated behavioural alterations in susceptible individuals [3, 4]. Initially developed as a model to screen antidepressant drugs, chronic unpredictable mild stress (CUMS) is increasingly used as a means to investigate behavioural, neurochemical and structural changes underlying anxiety and depression [5, 6]. CUMS acts as a suitable model with strong predictive validity as evidenced by decreased intake of sucrose, increase in anxiety- and depression-like behaviour, and reversal of these abnormalities by antidepressant drugs [7, 8]. Among the neuroendocrine changes accompanying chronic stress, interaction between gonadal hormones (estradiol, progesterone) and stress hormones (glucocorticoids) plays a pivotal role in influencing the