Forlano Paul M, Bass Andrew H
Department of Neurobiology and Behavior, Seeley Mudd Hall, Cornell University, Ithaca, New York 14853, USA.
J Neurobiol. 2005 Oct;65(1):50-8. doi: 10.1002/neu.20178.
Expression of the enzyme aromatase, which converts androgens to estrogens, is known to be regulated by gonadal steroids in brain areas linked to reproduction and related behaviors in several groups of vertebrates. Previously, we demonstrated in a vocal fish, the plainfin midshipman, that both males and females undergo seasonal changes in brain aromatase mRNA expression in the preoptic area (POA) and the dimorphic sonic/vocal motor nucleus (SMN) that parallel seasonal variation in circulating steroid levels and reproductive behavior. We tested the hypothesis that steroids are directly responsible for seasonal modulation of aromatase in females because they show the most dramatic fluctuations of testosterone (T) and 17beta-estradiol (E2) throughout the year. Adult female midshipmen were ovariectomized and administered T, E2, or blank (control) implants. We then quantified aromatase mRNA expression within the POA and SMN by in situ hybridization. Both T- and E2-treated females had elevated mRNA expression levels in both brain areas compared to controls. T affected aromatase expression in a level-dependent manner, whereas E2 showed a decreased effect at higher circulating levels. This study demonstrates that seasonal differences in brain aromatase expression in female midshipman fish may be explained, in part, by changes in levels of circulating steroids.
已知在几组脊椎动物中，将雄激素转化为雌激素的芳香化酶在与繁殖及相关行为有关的脑区受性腺类固醇调节。此前，我们在一种会发声的鱼类——光鳍鼓鱼中证明，雄性和雌性的视前区（POA）和两性异形的发声/声运动核（SMN）中的脑芳香化酶mRNA表达都会发生季节性变化，这与循环类固醇水平和繁殖行为的季节性变化平行。我们检验了这样一个假设，即类固醇直接导致雌性芳香化酶的季节性调节，因为它们在全年表现出最显著的睾酮（T）和17β-雌二醇（E2）波动。成年雌性光鳍鼓鱼接受卵巢切除手术，并植入T、E2或空白（对照）植入物。然后，我们通过原位杂交对POA和SMN内的芳香化酶mRNA表达进行定量。与对照组相比，接受T和E2处理的雌性在两个脑区的mRNA表达水平均有所升高。T以剂量依赖的方式影响芳香化酶表达，而E2在循环水平较高时作用减弱。这项研究表明，雌性光鳍鼓鱼脑芳香化酶表达的季节性差异可能部分由循环类固醇水平的变化来解释。
