5β-Dihydroprogesterone

5β-Dihydroprogesterone (5β-DHP) is a progesterone receptor agonist and metabolite of progesterone .1,2It is formed from progesterone by 5β-reductase.25β-DHP inhibits spontaneous contractions in isolated rat uterus when used at a concentration of 10 μg/ml, an effect that can be blocked by the progesterone receptor antagonist RU486 but not the GABAAreceptor antagonist picrotoxin .1It is a negative modulator of homooligomeric Ρ1 subunit-containing GABAAreceptors, inhibiting GABA-induced currents inX. laevisoocytes expressing these receptors (IC50= 5.02 μM) .3Plasma levels of 5β-DHP decrease at the onset of spontaneous human labor.4