Regulation of scent marking in the female Mongolian gerbil Meriones unguiculatus

The role of estrogens and progesterones in the control of scent marking in the female Mongolian gerbil (Meriones unguiculatus) has remained unclear. Two experiments were conducted which attempted to assess the ovarian contribution to the regulation of this behavioral pattern. In Experiment 1, ten groups of ovariectomized females were treated with one or a combination of steroid hormones which had been selected on the basis of being known secretory products of the ovaries of other rodent species. Only testosterone propionate or a combination of testosterone propionate and estrogen were effective in stimulating marking. Both androgens and estrogens supported gland growth whereas only estrogens supported uterus growth. In a second experiment, androstenedione, a primary precursor to testosterone and estrogen, was administered to intact and ovariectomized females for a period of four weeks. Each female received a weekly marking test following treatment. Intact females responded with a rapid and significant increase in marking frequency whereas ovariectomized and intact control females continued to mark at control levels. It was concluded that the conversion of androstenedione or related hormones into behaviorally active compounds during period of high marking (e.g., as during late gestation and lactation and lactation) is at least one means by which marking is regulated in the female gerbil.