Transgenerational modulation of the response to chronic stress in adolescent rats

Recent studies point out that parental life experiences, even those occurred in pre-reproductive phase, can affect neural and behavioral development of future offspring. The aim of this study is to investigate differences in response to chronic stress in the adolescent offspring of mothers pre-reproductively reared in standard or enriched conditions, by using the Forced Swim Test (FST). Female Wistar rats were reared from weaning to breeding age in enriched or standard environment. Subsequently, all females were mated and housed in standard conditions until offspring weaning. The offspring born to enriched and standard dams was further divided in two groups: a control group, reared in standard condition (CTR), and a group chronically stressed by social isolation (ISO). To evaluate transgenerational effects of maternal rearing conditions on coping skills to chronic stress, ISO and CTR groups were subjected or not to a single session of FST. Plastic changes and neuronal activation were identified by immunohistochemistry for glucocorticoid receptors and c-Fos and assessed using a stereological analysis software. The biochemical correlates were measured in the hippocampus and amygdala, structures closely involved in hypothalamo-pituitary-adrenocortical axis regulation. The results show significant behavioral and biochemical effects of chronic stress. Interestingly, ISO and CTR offspring of enriched dams shows fewer amygdaloid c-Fos immunopositive cells in response to FST compared to offspring of standard dams. These findings evidence the transgenerational influence of maternal life experiences in regulating the offspring response to chronic stress.