The hormone replacements administered to Sham and Ovx mice prior to a cocaine challenge. Shams received vehicle for the same time-frame as hormone-replaced Ovx mice. All injections were given in the morning. All mice received a final injection of vehicle or hormone before being placed into locomotor boxes for habituation. For the 30 min versus 2 day replacement study, mice instead received their final injection after the saline treatment during testing, 30 min prior to the COC injection. E2 = 17β-estradiol; PPT = 4,4′,4″-(4-Propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol; DPN = 2,3-bis(4-Hydroxyphenyl)-propionitrile; N/A = not applicable.