Abstract

Previous studies demonstrated that throughout the preweaning period prenatally stressed rats have an overactive hypothalamic-pituitary-adrenal (HPA) system. This increased HPA activity was accompanied by an increase in defensive behavior. This study examined whether these alterations in HPA activity and defensive behavior continued into adulthood. Brain catecholamines in the cerebral cortex and locus coeruleus were also measured in prenatally stressed and control rats. Shock-induced levels of defensive freezing were significantly higher in prenatally stressed rats than in controls. However, plasma ACTH and corticosterone concentrations did not differ between groups either in the basal state or after exposure to foot shock. Concentrations of norepinephrine (NE) in the cerebral cortex and locus coeruleus region were significantly reduced in prenatally stressed rats. In addition, concentrations of NE metabolites were significantly elevated in prenatally stressed rats, suggesting an increased turnover of brain NE. Prenatally stressed rats also had, in the locus coeruleus region, significantly reduced dopamine (DA) levels but elevated concentration of DA metabolites. Results indicate that prenatal stress produces an increased behavioral responsiveness to stress that is evident in early life and continues into adulthood. The early hyperactivity of the HPA system in prenatally stressed rats, however, appears to normalize in adulthood. The increased turnover in brain catecholamines measure in the cerebral cortex and locus coeruleus region of prenatally stressed rats may be associated with the heightened expression of stress-induced behavior.