Further studies on estrogen-induced maternal behavior in hysterectomized-ovariectomized virgin rats

A dose-reponse relationship between estradiol benzoate (EB) and the latency to the onset of maternal behavior was determined in hysterectomized-ovariectomized (HO) virgin rats. Females were treated with either oil or EB in doses (μg/kg) of 25, 50, 50 in two daily injections, 100, or 200 at the time of surgery and presented with test pups 48 hr later. Only the EB-100 and 200 groups displayed short-latency maternal behavior. These two doses were used in the second study that examined the interval between EB administration and the onset of testing in HO rats. When pups were initially introduced at 72 hr, only the EB-200 group had short latencies while at 96 hr, neither EB dose was effective. In the third experiment, EB-100 and 200 HO groups were treated concurrently with either 2 mg of an anti-estrogen, CI-628, or the ethanol vehicle and tested 48 hr later. The two EB only groups had shorter latencies to the onset of maternal behavior than the EB plus CI-628 groups and the oil plus CI-628 or vehicle controls.