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. 2008 Jan;209(1):284-7.
doi: 10.1016/j.expneurol.2007.09.013. Epub 2007 Oct 25.

Pubertal ovarian hormone exposure reduces the number of myelinated axons in the splenium of the rat corpus callosum

M A Yates  1 , J M Juraska
Affiliations

Pubertal ovarian hormone exposure reduces the number of myelinated axons in the splenium of the rat corpus callosum

M A Yates et al. Exp Neurol. 2008 Jan.

Abstract

The size of the female rat corpus callosum decreases in response to pubertal ovarian hormone exposure, but the underlying changes in axonal composition have not been examined. In the current study, animals underwent ovariectomy or sham surgery at day 20, and the number of myelinated and unmyelinated axons were examined in young adulthood (2 months) using electron microscopy. Ovariectomized animals had a greater number of myelinated axons compared to intact animals, while total axon number was not affected. Ovarian hormone exposure seems to limit the number of axons that become myelinated in the splenium, while not affecting the number of axons crossing through the region.

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Figures

Figure 1
Figure 1
Electron micrograph from the splenium of the rat corpus callosum showing myelinated and unmyelinated axons. * indicates myelinated axons, while ^ points to unmyelinated axons and + indicates glial processes. Scale bar= 1 micron.
Figure 2
Figure 2
The number of myelinated axons (a) was significantly affected by ovarian hormone exposure (p=.012), while unmyelinated axons (b), and total axons (c) in the splenium of the rat corpus callosum were not different in young adult animals that were ovariectomized or underwent sham surgery at 20 days of age.
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