Stress-Induced Changes in Corticoliberin and Vasopressin Expression in the Hypothalamus of Female Rats in a Model of Post-Traumatic Stress Disorder

We report here our studies of the neuroendocrine mechanisms underlying the development of an anxiety-like state in female rats at different phases of the estrous cycle (blood estradiol level) in a stress–restress post-traumatic stress disorder (PTSD) model. Quantitative immunocytochemical methods were used to demonstrate an increase in corticoliberin expression in the paraventricular nucleus (PVN) of the hypothalamus in female rats 10 days after restress in all experimental groups. On post-restress day 30, the level of corticoliberin expression in the PVN of the hypothalamus decreased to the level seen in the control group. A significant increase in vasopressin immunoreactivity during development of the anxiety-like state was seen only in the PVN of the hypothalamus in female rats in the estrus phase (low estradiol level) at the moment of severe combined stress in the stress–restress model. Thus, the most significant changes in the neuroendocrine system of the hypothalamus was seen in female rats subjected to stress in the estrus phase, this consisting of a sharp decrease in the endogenous plasma estradiol level. Hyperactivity of the hypothalamic component of the vasopressinergic system can evidently be regarded as one of the mechanisms forming the experimental anxious PTSD-like state in female rats in the stress–restress model.

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