Chronic Prenatal Stress Affects Development and Behavioral Depression in Rats

We have used the approach of Willner et al (1987), which consists of transitory and variable changes in the rat's living conditions, to investigate the influence of chronic prenatal stress on pup development and their susceptibility to behavioral depression at adult age, as assessed by the learned helplessness model. Pregnant female Wistar rats were divided into either stressed (S; N = 35) or non-stressed (NS; N = 35) groups during the last two weeks of pregnancy. The male and female pups of both groups were either handled to test for physical development up to weaning (H; N = 25 litters) or left undisturbed (NH; N = 10 litters) until adult age, at which time the males from all four experimental groups were divided into two subgroups (N = 10 each) and were submitted to the learned helplessness model of depression. Prenatal stress reduced the number of male pups per litter, decreased the anogenital distance, and produced earlier earflap and eye opening dates, as well as a faster righting. Behavioral depression was induced in all cases, except in the NS -H animals. The prenatally stressed, non -handled pups showed greater escape latency than the NS subgroups. We conclude that the stress schedule used in this study was stressful to dams and sufficient to affect the pups' development and to increase the intensity of induced behavioral depression at adult age.