In vitro activity: Allopregnanolone, also known as 5α-pregnan-3α-ol-20-one or 3α,5α-tetrahydroprogesterone (3α,5α-THP), or SAGE-547, Brexanolone, and Allotetrahydroprogesterone, is a progesterone metabolite that serves as an allosteric modulator of the GABA (γ-aminobutyric acid) receptor. It has the potential for the treatment of epilepsy and depression. Allopregnanolone is an endogenous inhibitory pregnane neurosteroid that is synthesized from progesterone. Allopregnanolone has effects similar to those of other positive allosteric modulators of the GABA action at GABAA receptor such as the benzodiazepines, including anxiolytic, sedative, and anticonvulsant activity. Endogenously produced allopregnanolone exerts a pivotal neurophysiological role by fine-tuning of GABAA receptor and modulating the action of several positive allosteric modulators and agonists at GABAA receptor. Allopregnanolone induces a significant increase in proliferation of neuroprogenitor cells derived from the rat hippocampus and human neural stem cells derived from the cerebral cortex in a dose-dependent manner. Allopregnanolone increases the expression of genes that promote mitosis and inhibits the expression of genes that repress cell proliferation. Its biosynthesis begins with progesterone, which is converted to dihydroprogesterone by the enzyme 5α-DHP and after that, the enzyme 3α-HSOR catalyses the reduction of dihydroprogesterone toward allopregnanolone.

Cell Assay: Allopregnanolone induces a significant increase in proliferation of neuroprogenitor cells derived from the rat hippocampus and human neural stem cells derived from the cerebral cortex in a dose-dependent manner. Allopregnanolone increases the expression of genes that promote mitosis and inhibits the expression of genes that repress cell proliferation. Its biosynthesis begins with progesterone, which is converted to dihydroprogesterone by the enzyme 5α-DHP and after that, the enzyme 3α-HSOR catalyses the reduction of dihydroprogesterone toward allopregnanolone.