An electron microscopic analysis of the optic nerve of the eastern chipmunk (Tamias sibiricus asiaticus): Total fiber count and retinotopic organisation

Kazuo Wakakuwa, Masami Watanabe, Tomosada Sugimoto, Asao Washida, Yutaka Fukuda

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

On the basis of light and electron microscopic observations of the cross-section, the total count of optic nerve fibers in the eastern chipmunk (Tamias Sibiricus asiaticus) was estimated to be 5.65 × 105. Almost all the fibers were myelinated and only 0.9% were unmyelinated. Axon diameters of myelinated fibers showed a skewed unimodal distribution ranging from 0.2 to 3.6 μm (mean, 0.83) with the peak at 0.6-0.7 μm. Myelin sheath thickness positively correlated with the axon diameter. In the cross-section fiber density was highest in the naso-dorsal to the central part and lowest in the temporo-ventral part. Large axons are concentrated in the temporo-ventral part of the optic nerve, corresponding to the localisation of large ganglion cells in temporal crescent of the retina. A gross retinotopic organisation was verified among the optic nerve fibers in the cross-section after localised lesions by laser beam in the nasal and temporal periphery. However, when the retinal lesion was made in or around the central high density area, a non-retinotopic arrangement of the optic nerve fibers was suggested.

Original languageEnglish
Pages (from-to)1891-1901
Number of pages11
JournalVision Research
Volume27
Issue number11
DOIs
Publication statusPublished - 1987

Keywords

  • (Tamias sibiricus asiaticus)
  • Axon diameter
  • Eastern chipmunk
  • Optic nerve
  • Retinotopy
  • Total fiber count

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems

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