Allopregnanolone is an endogenous inhibitory pregnane neurosteroid that is synthesized from progesterone . It acts as a positive allosteric modulator of GABAA receptors at nM concentrations (exhibiting the greatest potentiation at isoforms containing δ subunits) and of GABAC receptors at μM concentrations. Allopregnanolone displays effects similar to other GABAA receptor potentiators such as benzodiazepines, including potent anticonvulsant, anxiolytic, and sedative activity.