Gestational stress leads to depressive-like behavioural and immunological changes in the rat.

Stress during pregnancy, gestational stress, can increase the chance of developing postpartum depression, which is estimated to occur in 10% of women. Since major depression is accompanied by an activation of the inflammatory response system, the aim of this study was to investigate if stress during pregnancy induces postpartum depressive-like behaviour, and if so, is it accompanied by activation of the inflammatory response system in female Fisher rats. We investigated the effect of gestational stress on the production of depressive-like behaviour in the rats. The pregnant dams underwent daily restraint stress (for 1 week, 3 times/day) or were left undisturbed (control). On postpartum day 22, the rats were introduced to the forced swim test (pre-test). On postpartum days 23 and 24 (test days), the immobility time was measured. Gestational stress significantly elevated immobility scores by 35-40% above the control values on both test days, which suggests that the stressed group displayed postpartum depressive-like behaviour. The concentrations of the pro-inflammatory cytokines interleukin-1beta, tumour necrosis factor-alpha and the anti-inflammatory cytokine interleukin-10 in stimulated whole-blood culture were also analysed. The stressed group showed higher levels of all three cytokines. No significant differences in the cytokine concentrations were detected in the hypothalamus, hippocampus or pre-frontal cortex.