PRENATAL STRESS MODIFIES SPATIAL COGNITION IN MICE: EFFECTS OF AGE AND SEX.

Abstract

Prenatal stress is linked with neuropathology of the cortical-hippocampal circuit, due to abnormal brain development that leads to long term neurological deficits in offspring, in both rodents and in humans with psychiatric disorders. Conflicting reports exist of the effects of prenatal stress in C57BL/6J mice, which is an inbred strain that is the most frequently used for neurobehavioral research. We now present comprehensive analyses of the effects of prenatal stress on spatial cognition and related behaviors in this inbred strain, in males and females at young adult and aged adult stages. The prenatal stress exposure was conducted by exposing pregnant mice to restraint stress three times daily from day 7 to day 18 of gestation. We tested the effects of prenatal stress on cognitive behavior using a battery of behavioral assays including the open-field test, the light-dark box, Morris water maze spatial acquisition and spatial reversal testing, in addition to assays of social interaction and social memory. We compared the behavioral phenotype of male and female offspring in young adult (10-20 weeks) and older adult ages (60- 70 weeks). Data reveal that male but not female mice had reduced body weight throughout the lifespan after exposure to prenatal stress. Young prenatally stressed adult females showed greater organization of tracking behavior in spatial acquisition tests than other groups. Prenatal stress improved reversal learning in aged females relative to non-stressed aged females. We detected decreased extinction of the spatial acquisition memory in prenatally stressed young adult mice of both sexes. Overall results indicate that prenatal stress may protect females from detrimental effects of age on function of the hippocampus. Our data support the finding that C57BL/6J are a relatively resilient strain of mouse that may be useful for investigating the differences between resilience and susceptibility to stress. Genomic differences between the C57BL/6J strain relative to Swiss Webster strain, which is more susceptible to prenatal stress are discussed. Future studies of prenatal stress in the C57BL/6J mouse strain should focus on the identification of molecular pathways that underlie resilience to prenatal stress, to identify novel targets for drug development.