Selective activation of estrogen receptor alpha in Japanese quail embryos affects reproductive organ differentiation but not the male sexual behavior or the parvocellular vasotocin system

Estradiol is crucial for normal female differentiation in birds. Developmental effects of estrogen are believed to be mediated by slow genomic actions through the nuclear estrogen receptors alpha (ERa) and/or beta (ERb). Consequently, exogenous compounds that interfere with the ERs may disrupt sexual differentiation of the reproductive organs and of the brain areas controlling sexual behaviors. The present study was conducted to elucidate the role of ERa in xenoestrogen-induced disruption of sexual differentiation in the Japanese quail (Coturnix japonica). Embryonic treatment with the synthetic estrogen, ethinylestradiol (EE2), and with the ERa-selective agonist, propyl pyrazole triol (PPT), induced oviductal malformations in females and retention of oviducts in males. Both EE2 and PPT caused weight asymmetry between left and right testes and reduced the cloacal gland area in males. EE2 significantly reduced the copulatory behavior in males whereas PPT had no effect on this behavior. The sexually dimorphic parvocellular vasotocin-immunoreactive (VT-ir) system in the medial preoptic nucleus (POM), the lateral septum (SL) and the medial part of the nucleus of the stria terminalis (BSTm), was not affected by EE2 or PPT. Our results suggest that xenoestrogen-induced effects on reproductive organ differentiation are mediated by ERa, whereas demasculinization of male copulatory behavior and the VT-ir system appears not to be induced by activation of ERa alone.