Behavioural and Neurobiological Effects of Early Postnatal Stress in Mouse Dams and Their Pups

Abstract

Background: Early life and postpartum represent periods of increased risk for the development of mental health disorders. Previous studies suggest that stress during these vulnerable periods can contribute to behavioural and neurobiological disruptions, yet the concurrent effects of stressors on the mother and offspring remain poorly understood. This study examined stress-induced disruptions in behaviour and physiological measures using postnatal maternal separation (MS) in both the dam and offspring.

Methods: Eighteen female C57BL/6N mice were randomly assigned to a control or an MS condition, which consisted of daily 3-hour separations from postnatal day 2 (P2) to P14. Maternal care behaviour was assessed on P3 and P7. Depressive- and anxiety-like behaviour was examined on P22-23 in dams and on P42-43 in the offspring, with food reward-seeking also being evaluated in the latter. Tissue collection was conducted 24 hours after the last behavioural test, during which the medial prefrontal cortex and colon were collected from dams to assess pro-inflammatory cytokine expression, and the nucleus accumbens (NAc) from pups to examine mesolimbic-related markers.

Results: MS disrupted components of maternal responsivity but had no effect on depressive- or anxiety-like behaviour or on cytokine expression in dams. In pups, MS promoted food reward seeking in both sexes but increased dopamine receptor 2 and neurotrophic receptor tyrosine kinase 2 expression in the NAc of males only, while not changing anxiety- or depressive-like behaviour.

Conclusion: MS induced disruptions in select behavioural and physiological measures in both pups and dams, providing insight into the effects of stress during sensitive life periods.