Topography of cones and rods in the tree shrew retina

Authors

  • Brigitte Müller,

    Corresponding author
    1. Max-Planck-Institut für Hirnforschung, D-6000 Frankfurt/Main 71, Federal Republic of Germany
    • MPI für Hirnforschung, Neuroanatomische Abteilung, Deutschordenstraße 46, D-6000 Frankfurt/M. 71, Federal Republic of Germany
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  • Leo Peichl

    1. Max-Planck-Institut für Hirnforschung, D-6000 Frankfurt/Main 71, Federal Republic of Germany
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Abstract

The topographical distribution of cones and rods in the tree shrew retina was analysed quantitatively in whole-mounted retinae and horizontal semithin sections stained with cresyl violet or toluidine blue. The outer nuclear layer consists of a single layer of photoreceptor nuclei with the rod nuclei slightly displaced towards the outer plexiform layer. This facilitated quantification of the photoreceptor populations. The density of cones ranges from 12,000/mm2 in the peripheral retina to a maximum of 36,000/mm2 in the inferior retina. Unlike ganglion cell density, the density of cones does not peak in the temporal retina. Rod density, between 500/mm2 and 3,500/mm2, also peaks in the inferior retina, but not in the same region as cone density. Rods constitute from 1 to 14% of the photoreceptor population, depending on retinal location, and have a local minimum at the central area. Amongst the cones a regularly arrayed subpopulation of presumed blue-sensitive cones is distinguished by its special staining properties. These cones constitute between 4 and 10% of the cone population depending on retinal location. A second, irregularly spaced, subpopulation of possibly pathological cones is also described.

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