Pregnanolone
Pregnanolone (3α-hydroxy-5β-pregnan-20-one or 3α,5β-tetrahydroprogesterone; sometimes abbreviated as 3α,5β-THP), also known as eltanolone (INN), is an endogenous neurosteroid that is biosynthesized from progesterone. It is a positive allosteric modulator of the GABAA receptor, as well as a negative allosteric modulator of the glycine receptor, and is known to have sedative, anxiolytic, anesthetic, and anticonvulsant effects. It was investigated for clinical use as a general anesthetic, but produced unwanted side effects such as convulsions on occasion, and for that reason was never marketed.