Saldanha C J, Tuerk M J, Kim Y H, Fernandes A O, Arnold A P, Schlinger B A
Department Physiological Science, University of California Los Angeles, Los Angeles, California 90095, USA.
J Comp Neurol. 2000 Aug 7;423(4):619-30. doi: 10.1002/1096-9861(20000807)423:4<619::aid-cne7>3.0.co;2-u.
In songbirds, aromatase (estrogen synthase) activity and mRNA are readily detectable in the brain. This neural aromatization presumably provides estrogen to steroid-sensitive targets via autocrine, paracrine, and synaptic mechanisms. The location of immunoreactive protein, however, has been difficult to describe completely, particularly in distal dendrites, axons, and terminals of the forebrain. Here we describe the neuroanatomical distribution of aromatase in the zebra finch by using a novel antibody raised specifically against zebra finch aromatase. The distribution of aromatase-positive somata in the zebra finch brain is in excellent agreement with previous reports. Additionally, this antibody reveals elaborate, spinous dendritic arbors, fine-beaded axons, and punctate terminals of telencephalic neurons that may synthesize estrogen. Some of these axon-like fibers extend into the high vocal center (HVC) and the robust nucleus of the archistriatum (RA) in males and females, suggesting a role for presynaptic aromatization in cellular processes within these loci. Adult males have more aromatase-positive fibers in the caudomedial neostriatum (NCM) and the preoptic area (POA) compared to females, despite the lack of detectable sex differences in the number of immunoreactive somata at these loci. Thus, the compartmentalization of aromatase in dendrites and axons may serve a sexually dimorphic function in the songbird. Finally, in adult males, aromatase expression is down-regulated by circulating estradiol in the hippocampus, but not in the NCM or POA. The distribution of aromatase suggests a role for aromatization in the regulation of pre- and postsynaptic function in steroid sensitive areas of the songbird forebrain.
在鸣禽中，大脑中易于检测到芳香化酶（雌激素合酶）的活性和信使核糖核酸。这种神经芳香化作用大概是通过自分泌、旁分泌和突触机制为类固醇敏感靶点提供雌激素。然而，免疫反应性蛋白的定位一直难以完全描述清楚，尤其是在前脑的远端树突、轴突和终末中。在此，我们通过使用一种专门针对斑胸草雀芳香化酶产生的新型抗体，描述了斑胸草雀中芳香化酶的神经解剖分布。斑胸草雀大脑中芳香化酶阳性胞体的分布与先前的报道高度一致。此外，这种抗体揭示了端脑神经元精细的、有棘的树突分支、细珠状轴突和点状终末，这些神经元可能合成雌激素。其中一些轴突样纤维延伸到雄性和雌性的高发声中枢（HVC）和古纹状体粗核（RA），这表明突触前芳香化作用在这些位点的细胞过程中发挥作用。与雌性相比，成年雄性在尾内侧新纹状体（NCM）和视前区（POA）中有更多芳香化酶阳性纤维，尽管在这些位点免疫反应性胞体的数量没有可检测到的性别差异。因此，芳香化酶在树突和轴突中的分隔可能在鸣禽中发挥性别二态性功能。最后，在成年雄性中，海马体中的芳香化酶表达受循环雌二醇下调，但在NCM或POA中则不然。芳香化酶的分布表明芳香化作用在鸣禽前脑类固醇敏感区域的突触前和突触后功能调节中发挥作用。
