Gender differences in short- vs. long-term impact of maternal depression following pre-gestational chronic mild stress

Major Depressive Disorder (MDD) with Peripartum Onset was classified in 2013 by the Diagnostic and Statistical Manual, Fifth Edition (DMS-5) and approved in 2019 by the World Health Organization (WHO). These diagnostic revisions call for the development of new animal models of maternal depression, emphasizing the pregnancy period. We have recently described a novel rat model of maternal MDD with a Peripartum Onset. Exposure to pre-gestational chronic mild stress (CMS) with repeated restrain resulted in maternal depressive-like behavior and impacted offspring's neurodevelopment. The present study examined gender differences in short- vs. long-term neurodevelopmental impact of pre-gestational maternal stress. Stress response was assessed in Sprague Dawley CMS-exposed dams (n=7) by metabolic, hormonal, and behavioral changes and compared to controls dams (n=7). Short-term impact of maternal stress on offspring was examined in terms of metabolic, neurodevelopmental, and behavioral tests in male (n=40) and female (n=35) adolescent offspring on a postnatal day (PD) 48; the long-term impact was assessed in adult male (n=13) and female (n=12) offspring on PD 225. Brain tissue was collected from adolescent and adult offspring for biochemical analysis. Maternal stress was associated with decreased body weight and increased urinary corticosterone during the pre-pregnancy period, but depressive-like behavior was delayed until later in pregnancy. No significant neurodevelopmental changes in suckling male or female offspring derived from the stress-exposed dams were observed. However, adolescent male and female offspring of stress-exposed dams displayed an increased depressive-like behavior and gender-dependent increase in anxiety-like behavior in female offspring. These changes were associated with a brain-region-specific increase in brain-derived neurotrophic factor (BDNF) protein and BDNF receptor (TrkB) mRNA in males. Behavioral changes observed in the adolescents receded in adult male and female offspring. However, plasma BDNF was elevated in stress-exposed adult female offspring. These results suggest that pre-gestational maternal stress is associated with gender-dependent short- vs. long-term neurodevelopmental impact in the offspring. Presented data are of significant public health relevance, and there is an urgent need for further research to confirm these findings and probe the underlying mechanisms.