Effects of adolescent Bisphenol-A exposure on memory and spine density in for ovariectomized female rats: Adolescence vs adulthood

The endocrine disruptor, Bisphenol-A (BPA), alters many behavioral and neural parameters in rodents. BPA administration to gonadally intact adolescent rats increases anxiety, impairs spatial memory, and decreases dendritic spine density when measured in adulthood. Since BPA's action seems to be mediated through gonadal steroid receptors, the current experiments were done in ovariectomized (OVX) female rats to examine the effects on behavior and spine density of adolescent BPA exposure under controlled hormone conditions. OVX (postnatal day, PND, 21) female Sprague-Dawley ran (n = 66) received subcutaneous injections of BPA (40 g/kg/body-weight), 17 beta-Estradiol (E2, 50 g/kg/bodyweight), or saline during adolescence (PND 38-49). Following the last injection brains were processed for Golgi impregnation (Expl), behavioral and spine density in adolescence (Exp2), or in adulthood (Exp3). In Expl, E2 increased spine density in CAl pyramidal cells and BPA decreased spine density in granule cells of the dentate gyrus (DG). In Exp2, BPA impaired spatial memory on the object placement (OP) task, E2 increased spine density in CAl, BPA decreased spine density in the DG and the medial prefrontal cortex (mPFC). When measured in adulthood (Exp3), BPA impaired OP and object recognition (OR) performance, E2 increased spine density in CAl, and BPA decreased spine density in CAl, the mPFC and the DG. Results provide novel data on the effects of adolescent BPA in an OVX model and are compared to data in intact animals and within the context of understanding the importance of the profound neuronal alterations occurring during adolescent development.