Juraska J M, Kopcik J R
Department of Psychology, University of Illinois, Champaign 61820.
Brain Res. 1988 May 31;450(1-2):1-8. doi: 10.1016/0006-8993(88)91538-7.
A contested report of sex differences in the size of the splenium of the corpus callosum in humans prompted the present examination of the corpus callosum in the rat. We have previously found that sex differences can vary with the rearing environment. Consequently, male and female rats were raised from weaning to 55 days of age in either a complex or an isolated environment. There were no sex differences in the size of the corpus callosum in sagittal cross section in these rats; however, rats of both sexes had a larger posterior third of the corpus callosum if they were raised in the complex environment. Because the corpus callosum continues to grow in size past 55 days of age, we examined socially housed rats at 113 days and again found no sex differences. The splenium was examined with electron microscopy in complex and isolation reared rats at 55 days of age. The ultrastructural analysis revealed differences that were not apparent from gross size measures. Females had more unmyelinated axons regardless of environment, and females from the complex environment had more myelinated axons than comparably housed males. In contrast, males in the complex environment had larger myelinated axons than females. Rats of both sexes from the complex environment had larger and more unmyelinated axons than isolated rats. In addition in myelinated axons, plasticity in the females occurred through changes in axon number and in males, through axon size. Thus sex differences exist in axonal number and size and the environment influences these differences.
一份关于人类胼胝体压部大小性别差异的有争议报告促使我们对大鼠的胼胝体进行了本次研究。我们之前发现，性别差异可能会因饲养环境而有所不同。因此，将雄性和雌性大鼠从断奶饲养至55日龄，饲养环境分为复杂环境或隔离环境。这些大鼠矢状面胼胝体大小不存在性别差异；然而，如果在复杂环境中饲养，两性大鼠胼胝体的后三分之一会更大。由于胼胝体在55日龄后仍会继续生长，我们在113日龄时对群居大鼠进行了检查，再次发现不存在性别差异。在55日龄时，对复杂环境饲养和隔离饲养的大鼠的压部进行了电子显微镜检查。超微结构分析揭示了一些从总体大小测量中不明显的差异。无论环境如何，雌性大鼠的无髓轴突更多，并且来自复杂环境的雌性大鼠比同等饲养条件下的雄性大鼠有更多的有髓轴突。相比之下，复杂环境中的雄性大鼠有髓轴突比雌性大鼠的更大。来自复杂环境的两性大鼠比隔离饲养的大鼠有无髓轴突更大且更多。此外，在有髓轴突方面，雌性大鼠的可塑性通过轴突数量的变化发生，而雄性大鼠则通过轴突大小发生。因此，轴突数量和大小存在性别差异，并且环境会影响这些差异。
