Influence of estrogen in the acquisition of intravenously self-administered heroin in female rats.

Previous research indicates that female rats acquire cocaine and heroin self-administration at a faster rate than male rats, and female rats with endogenous estrogen, or ovariectomized (OVX) rats with estrogen replacement acquire cocaine self-administration more rapidly than female rats with estrogen either surgically or chemically blocked. The purpose of this investigation was to extend the above findings to the acquisition of heroin (0.0075 mg/kg) self-administration in female rats.