Long lasting sex-specific effects upon behavior and S100b levels after maternal separation and exposure to a model of post-traumatic stress disorder in rats.

Early separation modifies responses to later traumatic stress differently by sex

An adult response to severe stress may depend partly on earlier developmental experience. This study tested that idea in rats, combining neonatal maternal separation with a later stress procedure designed to model selected features associated with post-traumatic stress disorder.

Testing two periods of exposure. Rat pups experienced repeated prolonged separation from their mothers during the first ten days of life or standard rearing. In adulthood, animals of both sexes were exposed, or not exposed, to inescapable footshock followed by reminders of the situation. Researchers measured conditioned fear, exploration, anxiety-like behavior and stress hormones.

They also measured S100B, a protein associated with glial and other cells, in both blood and cerebrospinal fluid. Comparing these compartments matters because a blood concentration need not directly reflect a change inside the brain.

Early history and sex shaped the pattern. Footshock increased conditioned fear. Both early separation and the adult stress procedure were associated with greater anxiety-like behavior and less exploration, with more pronounced effects in males. Baseline corticosterone was reduced. Some consequences of adult stress were aggravated by the earlier experience, consistent with developmental influences on later vulnerability.

S100B findings differed by sex and sample type. Blood levels increased in males exposed to shock but not in females. Cerebrospinal-fluid levels increased in females exposed to neonatal separation. These contrasting patterns caution against treating S100B in blood as a simple marker of one brain process. The authors proposed that the blood increase could have a source outside the brain.

The experiment provides a controlled way to examine how early and later stress combine. It does not reproduce the full human experience of trauma or diagnose PTSD in rats. Its contribution is the demonstration that behavioral and biological outcomes depend on the sequence of exposures, sex and the compartment in which a candidate marker is measured.