Abstract: Bisphenol-A (BPA), one of the well-known environmental endocrine disrupters with estrogen activity is a widely used industrial compound. With its expanded uses, BPA can be seen everywhere around us, and even has become an integral part of our daily life. As a result it makes more and more adult exposure to BPA in daily life. In recent years, many studies have focused on its toxicity to the reproductive system and development, but few studies on the adult brain and behaviors. It is reported that estrogen not only affects the development of the brain, but also participates in the adult brain plasticity and cognitive functions, so it is important to study the effects of adult exposure to BPA on brain. The purpose of the present study is to investigate whether adulthood exposure to BPA affects behaviors in mice.
After acclimatization for one week, adult male and female ICR mice were orally exposed to BPA dissolved in peanut oil (40, 400 μg/kg/day) or only peanut oil as a vehicle control from 5 weeks of age throughout 14 and a half weeks of age. At 13 weeks of age, open field, elevated plus-maze, Morris water maze, and step-down were respectively used to test spontaneous activity and exploratory behavior, anxiety, spatial learning and memory, and passive avoidance memory in mice.
The results showed that adulthood exposure to BPA for 8 weeks significantly inhibited the growth of body weight of male and female mice (p<0.05). Sexual difference of the frequencies of rearing and buttress standing in open field was abolished by adulthood exposure to BPA. The frequency of open arms entrance, the staying time in the open arms, and unprotected head dips in the central area of elevated plus-maze were significantly decreased in male (p<0.05 or p<0.01) but were increased in female (p<0.05 or p<0.01), resulting in abolishment or reverse of sex difference in exploration and anxiety behavior in adult mice. The results of Morris water maze test showed that adulthood exposure to BPA (40 µg/kg/d) significantly extended the average escape pathlength of the male (p<0.05), while no marked effect was found in the female, and BPA thus eliminated sex difference of spatial memory in adult mice. In step down test, adulthood exposure to BPA markedly shortened the latency to step down 24 h after footshock in male mice (p<0.05) but not in female, and the sex difference in passive avoidance memory was thus induced by exposure to BPA at 40 µg/kg/d (p<0.01).
These results suggest that adulthood exposure to BPA affected multiple behaviors and disturbed the sexual difference of these behaviors in mice.

Key words: bisphenol-A, behaviors, sex difference