Early Stress Leads to Long-Term Changes in Mice

FRIDAY, Oct. 3 (HealthDay News) -- A mouse model of chronic early stress demonstrated acute and long-lasting neuroendocrine and cognitive changes, according to research published in the October issue of Endocrinology.

Courtney J. Rice, of the University of California-Irvine, and colleagues used primiparous pregnant mice and their pups in testing their early stress environment. The researchers reduced the amount of bedding and nesting material for experimental mice, which led to dams leaving the nest more often compared to control dams which, in turn, increased chronic stress in the pups.

After a week, experimental pups had increased basal plasma corticosterone levels, as well as dramatically reduced levels of corticotropin releasing hormone mRNA in the hypothalamic paraventricular nucleus, the investigators found. These characteristics endured into adulthood, at which time experimental mice demonstrated impaired hippocampus-dependent learning and memory functions, as assessed by the Morris water-maze test.

"Importantly, the early life stress generated in this model results in enduring derangements of the hypothalamic-pituitary-adrenal axis and in neuronal dysfunction in the hippocampus," the authors conclude. "We hope that this mouse model will prove a widely-usable and powerful tool for using genetic engineering methodologies to investigate the roles of specific genes in the mechanisms of chronic stress early in life, as well as the consequences of this stress on the structure and function of hypothalamic-pituitary-adrenal axis and cognitive function."

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