Retinal projections in the blind mole rat: a WGA-HRP tracing study of a natural degeneration

Gilles Bronchti, Rony Rado, Joseph Terkel, Zvi Wollberg*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The mole rat Spalax ehrenbergi is a fossorial rodent. Although its peripheral visual system - eye and optic nerve - is highly degenerated, it shows some sensitivity to light. However, in the usual sense, it is essentially blind. An auditory take-over of the visual lateral geniculate nucleus and at least part of the visual cortices was recently demonstrated. In order to visualize the retinal projections during ontogeny, we used an anterograde tracing technique, with monocular injection of wheat germ agglutinin-labeled horseradish peroxidase (WGA-HRP). In the newborn mole rat the retina projects to most of its normal targets as compared with seeing rodents, with bilateral projections to the suprachiasmatic nuclei, the dorsal and ventral lateral geniculate nuclei, the lateroposterior nuclei, the optic tract nuclei and the superior colliculi. During the course of ontogeny, the retinohypothalamic connection is stabilized but the main optic tract undergoes progressive degeneration. In adults, only a few retinal fibers enter the contralateral ventral lateral geniculate nucleus, the lateroposterior nucleus, the optic tract nucleus and the superior colliculus. No retinal fibers could be detected in the dorsal lateral geniculate nucleus. Thus, the retinofugal projections in the adult mole rat could explain its reduced sensitivity to light, whereas the complete degeneration of the retino-dorsal lateral geniculate nucleus projection could underlie the invasion of auditory input into this normally visual center.

Original languageEnglish
Pages (from-to)159-170
Number of pages12
JournalDevelopmental Brain Research
Issue number2
StatePublished - 22 Feb 1991


  • Circadian system
  • Mole rat
  • Neuronal plasticity
  • Retino-hypothalamic tract
  • Retino-thalamic projection


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