The use of a novel and simple method of revealing neural fibers to show the regression of the lateral geniculate nucleus in the naked mole-rat ( Heterocephalus glaber)

• Published in: Brain research 2006-03, Vol.1077 (1), p.81-89
• Main Authors: Xiao, Jun, Levitt, Jonathan B., Buffenstein, Rochelle
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Eye and associated structures. Visual pathways and centers. Vision; Fundamental and applied biological sciences. Psychology; Geniculate Bodies - anatomy & histology; Heterocephalus glaber; Histological Techniques - methods; Histology; Light; Mole Rats - anatomy & histology; Myelin staining; Nerve Fibers, Myelinated - radiation effects; Neuroanatomy; Organ Size; Rats; Rats, Sprague-Dawley; Thalamus; Vertebrates: nervous system and sense organs; Visual system
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2006.01.021

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.