Perlman William R, Arnold Arthur P
Department of Physiological Science, Interdepartmental Program for Neuroscience and Laboratory of Neuroendocrinology of the Brain Research Institute, University of California, Los Angeles, California 90095, USA.
J Neurobiol. 2003 May;55(2):204-19. doi: 10.1002/neu.10190.
Male zebra finches sing and females normally do not. This sexually dimorphic behavior is mediated by a sexually dimorphic series of interconnected nuclei that are larger and more developed in males. Estradiol administered to females as early as the day of hatching (P1) causes profound masculinization of this song system. The exact timing of estrogen action is unknown, and there is little information concerning the times and sites of expression of estrogen receptors and aromatase before P5. We measured the expression of mRNAs encoding these proteins in brain during late embryogenesis and on P1 to determine if estrogen synthesis or receptor-mediated actions on the song system, as part of the program of sexual differentiation, might be possible during this period. Using highly sensitive and specific in situ hybridization procedures for mRNAs encoding ERalpha, ERbeta, and aromatase, we detected mRNA for ERs in archistriatal regions as early as embryonic stage 34, and in diencephalic regions as early as embryonic stage 30. ERalpha mRNA was also detected in the dorsal mesencephalon at P1. Aromatase mRNA expression was present as early as embryonic stage 30 in diencephalic and mesencephalic regions. No obvious sex differences in the spatio-temporal pattern of mRNA expression were detected. Our results suggest that estrogen can influence cell growth and differentiation in zebra finch brain well before hatching and into posthatching life. The results fail to provide support for the hypothesis that sexual differentiation of the song system is mediated by sex differences in the expression of these mRNAs at these ages.
雄性斑胸草雀会唱歌，而雌性通常不会。这种性别二态性行为是由一系列相互连接的性别二态性核团介导的，这些核团在雄性中更大且发育更完善。早在孵化日（P1）给雌性注射雌二醇会导致这种鸣叫系统发生深刻的雄性化。雌激素作用的确切时间尚不清楚，而且关于孵化前5天（P5）之前雌激素受体和芳香化酶的表达时间和部位的信息很少。我们测量了胚胎发育后期和P1时大脑中编码这些蛋白质的mRNA的表达，以确定作为性别分化程序的一部分，在此期间雌激素合成或受体介导的对鸣叫系统的作用是否可能。使用针对编码雌激素受体α（ERα）、雌激素受体β（ERβ）和芳香化酶的mRNA的高度敏感和特异的原位杂交程序，我们早在胚胎第34阶段就在古纹状体区域检测到了雌激素受体的mRNA，早在胚胎第30阶段就在间脑区域检测到了。在P1时，在中脑背侧也检测到了ERα mRNA。早在胚胎第30阶段，间脑和中脑区域就出现了芳香化酶mRNA的表达。未检测到mRNA表达的时空模式存在明显的性别差异。我们的结果表明，雌激素在孵化前以及孵化后的生命过程中都能很好地影响斑胸草雀大脑中的细胞生长和分化。这些结果未能为鸣叫系统的性别分化是由这些年龄段这些mRNA表达的性别差异介导的这一假设提供支持。
