Fitch R H, Cowell P E, Schrott L M, Denenberg V H
Biobehavioral Sciences Graduate Degree Program, University of Connecticut, Storrs 06269.
Brain Res. 1991 Mar 1;542(2):313-7. doi: 10.1016/0006-8993(91)91584-n.
The rat's corpus callosum is sexually dimorphic with the male's being larger. This difference appears to depend in part on the neonatal presence of testosterone in the male and ovarian hormones in the female. To further investigate the possibility that ovarian hormones participate in the differentiation of the rat's callosum, females received one of the following treatments on postnatal day 8, 12 or 16: (1) ovariectomy (Ovx); (2) 1 mg of testosterone propionate (TP); or (3) sham surgery. All animals were handled daily from birth until weaning. They were sacrificed at 110 days and a mid-sagittal section of the callosum was obtained. From this section measures of callosal area, perimeter, length, and 99 widths were derived. Widths were averaged into 7 factors as defined by prior factor analysis. Ovariectomy, whether on day 8, 12 or 16, enlarged callosal area and 3 of the callosal width factors. TP had no effect on any callosal variable when administered on day 8, 12 or 16. A comparison of control males and females replicated our prior findings of sexual dimorphism. We conclude that ovarian hormones act to feminize the female callosum, and that their removal results in defeminization. Furthermore, the fact that ovariectomy was effective as late as day 16, while TP treatment on day 8 or later had no effect, suggests that masculinization and feminization of this structure constitute separate processes with distinct sensitive periods.
大鼠的胼胝体具有性别二态性，雄性的胼胝体更大。这种差异似乎部分取决于雄性新生儿期睾酮的存在以及雌性卵巢激素的存在。为了进一步研究卵巢激素参与大鼠胼胝体分化的可能性，在出生后第8、12或16天对雌性大鼠进行以下处理之一：（1）卵巢切除术（Ovx）；（2）1毫克丙酸睾酮（TP）；或（3）假手术。所有动物从出生到断奶每天都进行处理。在110天时将它们处死，并获取胼胝体的正中矢状切片。从该切片得出胼胝体面积、周长、长度和99个宽度的测量值。根据先前的因子分析，宽度被平均分为7个因子。无论在第8、12还是16天进行卵巢切除术，都会增大胼胝体面积和3个胼胝体宽度因子。在第8、12或16天给予TP对任何胼胝体变量均无影响。对照雄性和雌性的比较重复了我们先前关于性别二态性的发现。我们得出结论，卵巢激素使雌性胼胝体女性化，去除这些激素会导致去女性化。此外，卵巢切除术在第16天仍然有效，而在第8天或之后给予TP处理则没有效果，这表明该结构的雄性化和雌性化构成了具有不同敏感期的独立过程。
