Arnold A P, Wade J, Grisham W, Jacobs E C, Campagnoni A T
Department of Physiological Science, University of California, Los Angeles 90095-1527, USA.
Dev Neurosci. 1996;18(1-2):124-36. doi: 10.1159/000111400.
The brain regions that control song in zebra finches are much larger in males, who sing, than in females, who do not. Two major theories have been proposed to explain sexual differentiation of the neural song circuit. The 'mammalian' theory suggests that sex steroid secretions of the tests cause masculine development in males. The 'avian' theory suggests that ovarian secretions induce feminine patterns of development in females. Although experimental evidence provides some support for the mammalian theory, neither theory comfortably predicts the outcomes of experiments that bear on the mechanisms of sexual differentiation. In particular, it has been relatively difficult to block sex steroid synthesis and action in genetic males in a way that prevents masculine neural differentiation. Moreover, genetic females that possess large amounts of testicular tissue can have a feminine neural song circuit, suggesting that testicular secretions are not solely responsible for the masculine patterns of differentiation. The results indicate that new theories are needed to explain sexual differentiation of the song system.
在斑胸草雀中，控制鸣叫的脑区在会鸣叫的雄性中比不会鸣叫的雌性要大得多。人们提出了两种主要理论来解释神经鸣叫回路的性别分化。“哺乳动物”理论认为，睾丸分泌的性类固醇会导致雄性的雄性化发育。“鸟类”理论认为，卵巢分泌会诱导雌性形成雌性发育模式。尽管实验证据为哺乳动物理论提供了一些支持，但这两种理论都无法轻松预测与性别分化机制相关的实验结果。特别是，以防止雄性神经分化的方式阻断遗传雄性中的性类固醇合成和作用相对困难。此外，拥有大量睾丸组织的遗传雌性可以拥有雌性神经鸣叫回路，这表明睾丸分泌并非是分化出雄性模式的唯一原因。结果表明，需要新的理论来解释鸣叫系统的性别分化。
