Estrogen and environmental estrogenic chemicals exert developmental effects on rat hypothalamic neurons and glias

We investigated effects of 17β-estradiol (E2) and endocrine disrupters, nonylphenol (NP) and bisphenol-A (BPA), focusing on the neuronal development in cultures of fetal rat hypothalamic cells. We applied different concentrations of E2, NP or BPA to the cultured hypothalamic cells and observed their effects on dendritic and synaptic development by immunocytochemistry using anti-microtubule associated protein-2 (MAP2) and anti-synapsin I antibodies, respectively. Administration of E2 for 7 days affected MAP2-positive area as well as synapsin I-positive area. NP and BPA also influenced neuronal developments. The significant increase both in MAP2- and synapsin I-positive areas was observed at 10 and/or 100 nM of them, while 1 μM of them reduced the positive areas. Synaptic densities calculated from synapsin I-positive area/MAP2-positive area were not constant among different doses of three chemicals, but increased at 10 and/or 100 nM and decreased at 1 μM. Furthermore, immunostaining of NP-treated cells with the antibody against glial fibrillary acidic protein (GFAP) revealed that glial development was similarly influenced by NP. Therefore, the present results demonstrated that not only E2 but also the environmental estrogenic chemicals, NP and BPA, affect development of fetal rat hypothalamic cells in vitro.