Noirot Isabelle C, Adler Henry J, Cornil Charlotte A, Harada Nobuhiro, Dooling Robert J, Balthazart Jacques, Ball Gregory F
Department of Psychology, University of Maryland, College Park, MD 20742, USA.
Hear Res. 2009 Jun;252(1-2):49-55. doi: 10.1016/j.heares.2009.04.012. Epub 2009 May 3.
Sex differences in song behavior and in the neural system controlling song in songbirds are well documented but relatively little is known about sex differences in hearing. We recently demonstrated the existence of sex differences in auditory brainstem responses in a songbird species, the zebra finch (Taeniopygia guttata). Many sex differences are regulated by sex steroid hormone action either during ontogeny or in adulthood. As a first step to test the possible implication of sex steroids in the control of sex differences in the zebra finch auditory system, we evaluated via immunocytochemistry whether estrogens are produced and act in the zebra finch inner ear. Specifically we examined the distribution of aromatase, the enzyme converting testosterone into an estrogen, and of estrogen receptors of the alpha subtype (ERalpha) in adult zebra finch inner ears. The anatomy of the basilar papillae was visualized by fluorescein-phalloidin, which delineated the actin structure of hair cells and supporting cells at their apical surface. Whole mount preparations of basilar papillae stained by immunocytochemistry revealed in both males and females an abundant aromatase distribution in the cytoplasm of hair cells, while ERalpha was identified in the nuclei of hair cells and of underlying supporting cells. Double-labeled preparations confirmed the extensive co-localization of aromatase and ERalpha in the vast majority of the hair cells. These results are consistent with studies on non-avian species, suggesting a role for estrogens in auditory function. These findings are also consistent with the notion that estrogens may contribute to a sex difference in hearing. To our knowledge, this is the first demonstration of the presence of aromatase and of the co-localization of aromatase and ERalpha in the sensory epithelium of the inner ear in any animal model.
鸣禽在鸣叫行为以及控制鸣叫的神经系统方面存在性别差异，这已得到充分证明，但关于听觉方面的性别差异却知之甚少。我们最近在一种鸣禽——斑胸草雀（Taeniopygia guttata）中证实了听觉脑干反应存在性别差异。许多性别差异是由性类固醇激素在个体发育期间或成年期的作用所调节的。作为测试性类固醇在斑胸草雀听觉系统性别差异控制中可能作用的第一步，我们通过免疫细胞化学评估了雌激素是否在斑胸草雀内耳中产生并发挥作用。具体而言，我们检查了芳香化酶（将睾酮转化为雌激素的酶）以及α亚型雌激素受体（ERα）在成年斑胸草雀内耳中的分布。用荧光素 - 鬼笔环肽使基底乳头的解剖结构可视化，它描绘了毛细胞和支持细胞顶端表面的肌动蛋白结构。通过免疫细胞化学染色的基底乳头整装标本显示，在雄性和雌性中，毛细胞的细胞质中都有丰富的芳香化酶分布，而ERα则在毛细胞及其下方支持细胞的细胞核中被鉴定出来。双重标记标本证实了芳香化酶和ERα在绝大多数毛细胞中广泛共定位。这些结果与对非鸟类物种的研究一致，表明雌激素在听觉功能中发挥作用。这些发现也与雌激素可能导致听觉性别差异的观点一致。据我们所知，这是在任何动物模型中首次证明内耳感觉上皮中存在芳香化酶以及芳香化酶和ERα的共定位。
