Maternal Behavior in the Rat: Facilitation through Gonadectomy

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Abstract
Virgin rats were ovariectomized and tested for induction of maternal behavior by being housed with neonatal young. A postoperative interval of 8 weeks yielded an average latency for the onset of maternal behavior significantly lower than that for intact controls or for virgin females ovariectomized 4 weeks before testing. Replacement of estrogen in the group ovariectomized for 8 weeks or injection of the estrogen antagonist ethamoxytriphetol (MER-25) in the group ovariectomized for 4 weeks changed the average latencies accordingly. Parallel results were obtained for males that were castrated 4 or 8 weeks before testing. It is concluded (i) that maternal behavior is under gonadal control and that this control is normally inhibitory; and (ii) that only after long-term removal of the gonads, resulting presumably in the complete clearance of estrogen and testosterone, is the maternal mediating system finally released from steroid suppression.