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SEXUALLY DIMORPHIC LORDOSIS BEHAVIOR IS MORE SENSITIVE TO DISRUPTION BY DEVELOPMENTAL EXPOSURE TO ETHINYL ESTRADIOL THAN IS REPRODUCTIVE MORPHOLOGY IN THE LONG EVANS FEMALE RAT.
Citation:
RYAN, B. C., K. HOWDESHELL, AND L. E. GRAY. SEXUALLY DIMORPHIC LORDOSIS BEHAVIOR IS MORE SENSITIVE TO DISRUPTION BY DEVELOPMENTAL EXPOSURE TO ETHINYL ESTRADIOL THAN IS REPRODUCTIVE MORPHOLOGY IN THE LONG EVANS FEMALE RAT. Presented at Society for the Study of Reproduction, Omaha, NE, July 29 - August 01, 2006.
Description:
Anthropogenic estrogens are pervasive in the environment. Although the effects of these xenoestrogens are controversial in humans, some fish species are adversely affected in contaminated ecosystems. While studies investigating endocrine disruptors typically focus on reproductive physiology and fertility, exposure to estrogens during development can also alter sexual differentiation of the nervous system and behavior in rodents. As a result, the brain can be imprinted such that it does not respond normally to estrogens in adulthood. Despite this, few studies have rigorously investigated the effect of developmental exposure to environmental estrogens on adult sexually dimorphic behavior in rats. This study established a framework for using adult sexually dimorphic behaviors as biomarkers for endocrine disruption in rodents. Using this approach, we measured the effects of oral maternal administration (gestational day 7 through postnatal day 18) to ethinyl estradiol (EE) (from 0.5 µg/kg/day to 50 µg/kg/day ) and bisphenol A (BPA) (from 2 µg/kg/day to 200 µg/kg/day) on the female Long Evans rat offspring. In this study, lordosis response, saccharin preference and running wheel activity in female rats (all sexually dimorphic behaviors) were compared to reproductive tract morphology in female rats. Lordosis behavior in adults was disrupted by developmental exposure to EE at doses of 0.5 µg/kg/day and above. At 5 µg/kg/day and above, EE disrupted organization of saccharin preference and reproductive morphology. In contrast, BPA gave inconsistent results throughout the study. These findings show reproductive tract abnormalities after developmental exposure to EE at doses lower than previously published in the rat. In addition, permanent behavioral disruption was seen at developmental doses below those which had an effect on morphology. This project was funded by the EPA/UNC Cooperative Research Grant T829472 and does not necessarily reflect EPA policies.