Probiotic L. reuteri treatment in stressed rats improves maternal care and corrects corticosterone-BDNF-oxytocin balance offering insights for maternal postpartum distress treatment.

Mothers experiencing depressive symptoms or gestational stress are at risk of developing maternal distress, which, in its most severe form, can progress to postpartum depression, profoundly affecting maternal well-being and infant care. Using a late-gestation restraint stress model, we investigated whether postpartum treatment of lactating dams with probiotic Limosilactobacillus reuteri (L. reuteri) could reverse stress-induced disruptions in maternal behavior and neurobiology. L. reuteri effectively improved maternal care, and restored reactivity to pup separation in stressed dams. Postpartum L. reuteri also corrected corticosterone-oxytocin imbalances in plasma, normalized hypothalamic oxytocin levels, the unglycosylated and glycosylated oxytocin receptor isoforms and it regulated the ratio of precursor to mature brain-derived neurotrophic factor (BDNF). Additionally, L. reuteri restored gut microbiota balance, increasing Lactobacillus spp. while reducing pathogenic strains in fecal pellets of stressed dams during lactation and post-weaning, correlating with both maternal oxytocin and corticosterone plasma levels. This study is the first to demonstrate the therapeutic efficacy of a probiotic and its molecular support in counteracting the adverse effects of gestational stress on maternal care through brain-gut axis mechanisms. These findings support probiotic-based interventions as safe, complementary preventive strategy for improving maternal health in conditions involving impaired maternal care and microbiota dysbiosis.