The Sigma-1 Receptor, Allopregnanolone & Mast Cell Activation – A Thread Worth Following — section

Pregnancy is one of the most controlled natural experiments we have. Progesterone surges. Allopregnanolone follows. Then delivery – a cliff drop. Postpartum depression isn’t just “hormones changing.” It’s a collapse of Sig-1R ligand availability, GABA tone, and neurosteroid-mediated mast cell regulation – all at once.