Reciprocal embryo transfer and newborns cross-fostering between mouse lines selected for high or low swim stress-induced analgesia.

Pain tolerance varies significantly among humans, with disparities attributable to genetic factors and environmental influences. The developmental origins of health and disease approach postulates that pre- and early postnatal maternal environment affects individuals' health and well-being. In the present study, we aimed to determine the influence of prenatal and early postnatal maternal environment and care on the offspring's physiology and pain response. To this end, we analysed the influence of bidirectional embryo transfer and cross-fostering between two mouse lines divergently selected for high and low swim stress-induced analgesia on offspring phenotype, swim stress-induced analgesia-related traits and opioid component of swim stress-induced analgesia. Our findings reveal that both the fetal development and early maternal care significantly influence the level of swim stress-induced analgesia in mice. High analgesia mice born after embryo transfer to low analgesia surrogate mothers showed reduced swim stress-induced analgesia levels alongside a diminished effect of the opioid antagonist naloxone, suggesting a decreased opioid component in swim stress-induced analgesia regulation. This effect was preserved in the 2nd filial generation of individuals originating from embryo transfer, but not cross-fostering. Additionally, both embryo transfer and cross-fostering resulted in changes in body weight and body temperature toward an average value of the surrogate or foster maternal line; however, these changes were not preserved in the 2nd filial generation. Together, our findings indicate that maternal influence during fetal development and the early postnatal period may influence physiological parameters, as well as traits associated with stress response. Maternal influence is more pronounced in progeny subject to embryo transfer, indicating a stronger influence of the prenatal period. Summary SentenceEmbryo transfer and cross-fostering between high- and- low analgesia mouse lines affects offspring physiology and stress response in a foster mother-related manner.