Stress induces equivalent remodeling of hippocampal spine synapses in a simulated postpartum environment and in a female rat model of major depression

•Postpartum stress causes a loss of hippocampal spine synapses.•Pregnancy levels of ovarian hormones prevent the synaptolytic effect of stress.•This preventive effect of ovarian hormones is mediated by reduced stress responsiveness.•These data provide further support for the “synaptogenic hypothesis” of depression.