The effect of prenatal ethanol exposure on scentmarking in the C57BL/6J and C3H/He mouse strains

Abstract

In utero exposure to ethanol has been shown to alter sexually dimorphic behaviors in rats. However, it is not clear whether this phenomenon is robust in other species, such as the mouse, which is sensitive to ethanol-induced birth defects. Further, it is not known whether significant differences exist across murine strains. If similar to the classic teratogenic effects of ethanol, it would be expected that strain differences in sensitivity should be evident, with some strains demonstrating an alteration in sexually dimorphic behavior and other strains demonstrating little or no effect. As a first attempt to address these issues, we have examined two mouse strains widely used in prenatal alcohol research, the inbred C3H/He and C57BL/6J strains. Scentmarking was selected as the behavior of interest. It is robustly sexually dimorphic in the rat and mouse, with males marking more than females and preliminary reports have demonstrated that in utero ethanol exposure reduces this behavior in the male rat. In the mouse strains selected for study, pregnant females were provided with either a liquid diet consisting of 25% ethanol-derived calories or pair-fed an isocaloric liquid diet from gestation days 6–18. An additional control group was included which was fed laboratory chow ad lib throughout gestation. Male and female offspring of each strain were tested for scentmarking at 65–75 days of age. As expected, results showed that the effect of prenatal ethanol exposure on scentmarking varied with both strain and sex. In the C3H/He strain, scentmarking was reduced significantly in male ethanol-exposed offspring (i.e., the males were feminized). In contrast, prenatally exposed C57BL/6J males did not differ significantly from their control. No changes in scentmarking due to prenatal treatment were detected in females of either strain. These findings suggest that the demasculinization of behavior noted in rats also can be found in mice but that not all murine strains are equally susceptible. Thus, mice may prove to be valuable murine complements to other rodent models in the investigation of the mechanism(s) underlying changes in sexually dimorphic behaviors due to prenatal ethanol exposure.