Estrogen-induced memory enhancements are blocked by acute bisphenol A in adult female rats: role of dendritic spines.

Acute effects of bisphenol (BPA), an environmental chemical, on estradiol (17α or β-E2)-dependent recognition memory and dendritic spines in the medial prefrontal cortex and hippocampus were investigated in adult female rats. Ovariectomized rats received BPA 30 min before or immediately after a sample trial (viewing objects), and retention trials were performed 4 h later. Retention trials tested discrimination between old and new objects (visual memory) or locations (place memory). When given immediately after the sample trial, BPA, 1-400 μg/kg, did not alter recognition memory, but 1 and 40 μg/kg BPA, respectively, blocked 17β-E2-dependent increases in place and visual memory. When ovariectomized rats were tested with 17α-E2, 1 μg/kg BPA blocked place memory, but up to 40 μg did not block visual memory. BPA, given to cycling rats at 40 μg/kg, blocked visual, but not place, memory during proestrus when 2 h intertrial delays were given. Spine density was assessed at times of memory consolidation (30 min) and retention (4 h) after 17β-E2 or BPA + 17β-E2. In prefrontal cortex, BPA did not alter E2-dependent increases. In the hippocampus, BPA blocked E2 increases in basal spines at 4 h and was additive with E2 at 30 min. Thus, these novel data show that doses of BPA, below the current Environmental Protection Agency safe limit of 50 μg/kg, rapidly alter neural functions dependent on E2 in adult female rats.