Xiao Jun, Levitt Jonathan B, Buffenstein Rochelle
Biology Department, The City College of New York, 138th Street and Convent Avenue, New York, NY 10031, USA.
Brain Res. 2006 Mar 10;1077(1):81-9. doi: 10.1016/j.brainres.2006.01.021. Epub 2006 Feb 14.
The lateral geniculate nucleus (LG) is an important subcortical nucleus in the visual system. It receives primary projections from the retina and relays these to central visual structures. Although there are studies on the retina and visual cortex of animals with regressed vision, little is known about the LG in such animals. The strictly subterranean naked mole-rat (Heterocephalus glaber) has markedly reduced visual acuity with concomitant pronounced changes in the visual cortex. We used a novel method to reveal myelinated neural fibers in a histological study assessing if the LG shows regressive changes commensurate with the level of reliance on vision by this rodent. Myelin detection here relies on significant differences in visible light reflection between neural fibers and the gray matter. Moreover, this simple method does not interfere with further staining for additional analyses. This method reveals that the contribution of the LG to brain volume in the naked mole-rat is less than a third of that of the rat. This shows that the retinogeniculocortical system in the naked mole-rat is considerably smaller than that of rodents that rely heavily on their visual system, but is nevertheless less regressed than that of the extensively studied blind mole-rat; this may facilitate limited responses to visual stimuli.
外侧膝状体（LG）是视觉系统中一个重要的皮层下核团。它接收来自视网膜的初级投射，并将这些投射中继至中枢视觉结构。尽管有关于视力退化动物的视网膜和视觉皮层的研究，但对于此类动物的外侧膝状体却知之甚少。严格营地下生活的裸鼹鼠（Heterocephalus glaber）视力显著下降，同时视觉皮层也有明显变化。我们采用一种新方法在组织学研究中揭示有髓神经纤维，以评估外侧膝状体是否呈现出与这种啮齿动物对视觉的依赖程度相称的退化变化。此处的髓磷脂检测依赖于神经纤维与灰质在可见光反射上的显著差异。此外，这种简单方法不会干扰用于其他分析的进一步染色。该方法表明，裸鼹鼠中外侧膝状体对脑容量的贡献不到大鼠的三分之一。这表明裸鼹鼠的视网膜 - 膝状体 - 皮层系统比严重依赖视觉系统的啮齿动物的相应系统小得多，但仍不如广泛研究的盲鼹鼠退化严重；这可能有助于对视觉刺激做出有限反应。
