Prenatal stress does not impair coping with challenge later in life

Abstract

This study investigated whether the effects of prenatal social stress are pathological consequences of an adverse environment; or whether mothers adjust their offspring to prevalent social conditions. As a prenatal stressor social instability was used: we studied male guinea pig offspring whose mothers lived in a stable social environment (SE-sons) or in an unstable social environment during pregnancy (UE-sons). Eight experimental groups were established, consisting of one SE-son, one UE-son and five females, respectively. In all groups females were regularly exchanged to create a situation of social instability. We hypothesised that if mothers prenatally adapt their offspring to an unstable social environment, UE-sons will be dominant, display agonistic and courtship behaviour more frequently, have higher body weights, be less reactive to moderate stressors and have higher testosterone concentrations than SE-sons. Our results revealed no significant differences between SE- and UE-sons concerning behaviour, dominance status, body weights, cortisol or testosterone. However, we found differences between dominant and subdominant males. Subdominant males had significantly higher cortisol levels than dominant males, pointing to a higher degree of stress. Regarding testosterone, dominant males had higher testosterone levels directly after the establishment of dominance hierarchies. Thus, these results do not provide evidence that mothers adjust their offspring prenatally to prevailing social conditions. They also do not support the hypothesis that instability of the mother's environment during pregnancy inevitably results in behavioural disorders or pathological endocrine profiles. Rather do the sons' behavioural and endocrine responses later in life reflect typical reactions to socially challenging situations.