Fitch R H, Denenberg V H
Biobehavioral Sciences Graduate Degree Program, University of Connecticut, Storrs 06269-4154, USA.
Behav Brain Sci. 1998 Jun;21(3):311-27; discussion 327-52. doi: 10.1017/s0140525x98001216.
Historically, studies of the role of endogenous hormones in developmental differentiation of the sexes have suggested that mammalian sexual differentiation is mediated primarily by testicular androgens, and that exposure to androgens in early life leads to a male brain as defined by neuroanatomy and behavior. The female brain has been assumed to develop via a hormonal default mechanism, in the absence of androgen or other hormones. Ovarian hormones have significant effects on the development of a sexually dimorphic cortical structure, the corpus callosum, which is larger in male than in female rats. In the females, removal of the ovaries as late as Day 16 increases the cross-sectional area of the adult corpus callosum. Treatment with low-dose estradiol starting on Day 25 inhibits this effect. Female callosa are also enlarged by a combination of daily postnatal handling and exogenous testosterone administered prior to Day 8. The effects of androgen treatment are expressed early in development, with males and testosterone-treated females having larger callosa than control females as early as Day 30. The effects of ovariectomy do not appear until after Day 55. These findings are more consistent with other evidence of a later sensitive period for ovarian feminization as compared to androgenic masculinization.
从历史上看，关于内源性激素在性别发育分化中作用的研究表明，哺乳动物的性别分化主要由睾丸雄激素介导，并且在生命早期接触雄激素会导致形成具有特定神经解剖结构和行为特征的雄性大脑。在没有雄激素或其他激素的情况下，雌性大脑被认为是通过激素默认机制发育的。卵巢激素对两性异形的皮质结构胼胝体的发育有显著影响，雄性大鼠的胼胝体比雌性大鼠的大。在雌性大鼠中，直到第16天切除卵巢都会增加成年胼胝体的横截面积。从第25天开始用低剂量雌二醇治疗可抑制这种效应。在出生后每天进行处理并在第8天之前给予外源性睾酮的联合作用也会使雌性胼胝体增大。雄激素治疗的效果在发育早期就会显现，早在第30天，雄性和接受睾酮治疗的雌性大鼠的胼胝体就比对照雌性大鼠的大。卵巢切除的效果直到第55天之后才会出现。与雄激素性男性化相比，这些发现与卵巢女性化较晚敏感期的其他证据更为一致。
