Fitch R H, Cowell P E, Schrott L M, Denenberg V H
Biobehavioral Sciences Graduate Degree Program, University of Connecticut, Storrs 06269-4154.
Int J Dev Neurosci. 1991;9(1):35-8. doi: 10.1016/0736-5748(91)90070-3.
The male rat's corpus callosum is significantly larger than the female's. This dimorphism depends in part on the early presence of testosterone, since postnatal administration of testosterone to female pups enlarges their callosa in adulthood to the size of males. However, castrating males on day 1 is ineffective in reducing (demasculinizing) the size of their callosa as adults. We then addressed the question as to whether testosterone acts prior to day 1 to enlarge the callosa of males. To investigate this hypothesis pregnant rats were administered a non-steroidal androgen blocker, flutamide, during the last 5 days of pregnancy, while controls received vehicle only. Male pups from flutamide litters were castrated on day 3 to prevent postnatal recovery following clearance of flutamide, while others received sham surgery. Callosal sex differences were found between males and females of control litters, but not between males and females from flutamide litters. The absence of sex effects among flutamide litters was a consequence of small callosal size in flutamide-castrated males as compared to control males. We concluded that the prenatal production of testosterone in the male rat pup contributes to sexual dimorphism in the callosa of adult rats.
雄性大鼠的胼胝体明显大于雌性。这种两性差异部分取决于睾酮的早期存在，因为在出生后给雌性幼崽注射睾酮会使其成年后的胼胝体增大到雄性的大小。然而，在出生第1天对雄性进行阉割并不能有效减小（去雄性化）其成年后胼胝体的大小。然后我们探讨了睾酮是否在出生第1天之前就发挥作用来增大雄性的胼胝体这一问题。为了研究这一假设，在妊娠的最后5天给怀孕大鼠注射一种非甾体雄激素阻滞剂氟他胺，而对照组只注射赋形剂。来自氟他胺处理窝的雄性幼崽在出生第3天被阉割，以防止氟他胺清除后出生后的恢复，而其他幼崽接受假手术。在对照组窝的雄性和雌性之间发现了胼胝体的性别差异，但在氟他胺处理窝的雄性和雌性之间未发现。与对照雄性相比，氟他胺阉割的雄性胼胝体较小，这导致了氟他胺处理窝中不存在性别效应。我们得出结论，雄性幼鼠产前产生的睾酮促成了成年大鼠胼胝体的两性差异。
