Prenatal maternal programming determines testosterone response during social challenge

The present study investigated in domestic guinea pigs whether the effects of prenatal social stress are pathological consequences of adverse social conditions; or whether mothers adjust their offspring to the environment they experience during pregnancy. 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 (UE-sons) during pregnancy. Eight experimental groups were established, consisting of one SE-son, one UE-son and five females, respectively. All experimental groups remained in a stable group composition for the whole investigation time. We hypothesized that if mothers prenatally adapt their offspring, in a stable social environment SE-sons will be dominant, display agonistic and courtship behavior more frequently, have higher body weights, be less stressed and have higher testosterone concentrations than UE-sons. Our results show no significant differences between SE- and UE-sons concerning behavior, body weight or plasma–cortisol concentrations. Hence no evidence exists that an unstable social environment during pregnancy has pathological consequences for the male offsprings' phenotype. However, SE-sons had significantly higher plasma testosterone concentrations than UE-sons in phases when females were receptive. A higher reactivity of the hypothalamic–pituitary–gonadal axis might enable SE-males to adjust testosterone levels to the present social situation: they are significantly elevated in decisive phases of female receptivity, but remain on a lower level before and after reproductive challenge. Thus, mothers who experienced social stability during pregnancy provide their sons prenatally with a promising reproductive strategy in competitive situations later in life.