Offspring-exposure reduces depressive-like behaviour in the parturient female rat

In women, breastfeeding generally results in reductions in anxiety and increased positive mood. However, approximately 10-15% of women experience depressed mood and increased anxiety during the first year postpartum. Recent research has demonstrated that offspring-exposure is important for the reduction in behaviours related to depression and anxiety in the mother. It remains to be determined whether these effects are due to factors related to pregnancy and/or pup-exposure, are associated with the degree of maternal behaviour by the mother towards offspring, or persist after weaning. To address these questions the present study used four groups of female rats; primiparous, nulliparous, primip-no-pups (primiparous females with pups permanently removed), and sensitized females. Depressive- and anxiety-like behaviours were assessed 1 week after weaning/pup-exposure (4 weeks after birth for primip-no-pups animals) using the forced swim test for measures of depressive-like behaviour, and the open field test and elevated plus maze for measure of anxiety-like behaviour. Results demonstrate that primiparous females without pup-exposure have increased depressive-like, but not anxiety-like, behaviour compared to primiparous and sensitized females. In addition, kyphotic nursing by primiparous mothers was negatively related to behavioural measures of depression and anxiety. From this work it is clear that pup-exposure is important for reductions in depressive-like behaviour in parturient females. Further research is needed to determine the extent of these changes and the neural and hormonal correlates of these events.