Allopregnanolone and Induction of Endogenous Opioid Inhibition of Oxytocin Responses to Immune Stress in Pregnant Rats

In this study, researchers investigated the role of allopregnanolone, a neuroactive metabolite of progesterone, in modulating oxytocin responses to immune stress in pregnant rats. They found that in late pregnancy, allopregnanolone induced opioid inhibition of oxytocin secretion in response to interleukin-1β (IL-1β), which mimics infection. This inhibition helps preserve oxytocin stores for childbirth and reduces the risk of preterm labor. The study showed that inhibiting allopregnanolone synthesis with finasteride increased oxytocin secretion and neuronal activation in pregnant rats, while allopregnanolone reduced these responses in virgin rats. The findings suggest that allopregnanolone and endogenous opioid mechanisms work together to regulate oxytocin responses during pregnancy.