Sex differences in learning deficits induced by prenatal stress in juvenile rats

Stress during pregnancy results in neurochemical and behavioral alterations observed throughout adulthood and aging. We here examined the impact of prenatal stress (PS) on cognitive functions in juvenile-4-week-old-rats, focusing on putative sex differences. Dams received an unpredictable 90-min duration contention stress between gestational day E 17 and E20. Locomotion and learning ability were examined in offsprings between day P24 and P29 using actimetry, spontaneous alternation in the Y-maze, delayed alternation in the T-maze, and passive avoidance. Both male and female PS rats showed increased activity. In the Y-maze, diminished spontaneous alternation (males: -20%; females: -29%) were seen for PS rats compared to non-PS rats. The number of arm entries was unchanged among groups. In the T-maze, PS rats failed to perform delayed alternation, as shown by equal time spent and number of entries in both the novel and previously explored arms. In the passive avoidance test, PS resulted in significant impairments for female offspring only of both step-through latency and percentage of animals to criterion. PS thus induced severe learning impairments affecting both short-term and long-term memories that could be observed early in lifetime, in 4-week-old, juvenile rats. In addition, marked sex differences were evidenced, particularly in the passive avoidance response that may reflect differential developmental neuroadaptations in precise brain structures. (C) 2003 Elsevier B.V. All rights reserved.