Document Detail

Topographic disorganization of the optic tracts following long-term optic nerve regeneration: a quantitative image analysis study.
MedLine Citation:
PMID:  2229475     Owner:  NLM     Status:  MEDLINE    
Experiments were designed to find the degree to which regenerated optic axons occupied their previous locations in the optic tracts. Following optic nerve crush and regeneration, either the dorsal, ventral, peripheral, temporal, or nasal part of the retina was ablated. The axons of the remaining retinal ganglion cells (RGCs) were labeled with cobalt. Density of the regenerated dorsal and ventral axons in the dorsal vs. ventral optic tracts was determined digitally. In addition, we determined the density of temporal and nasal axons in the temporal vs. nasal compartments of each optic tract and the density of central axons in the central vs. peripheral compartments of both optic tracts. Regenerated axons were not distributed randomly in the optic tracts. Instead, they were slightly but, significantly biased toward growing through the tract or compartment that they had occupied previously. Still, the pathway specificity exhibited by the regenerated axons was closer to random than it was to the pathway specificity seen in normal animals. Dorsal, ventral, and central RGC axons were significantly better localized to their correct tract or compartment than were temporal or nasal RGC axons. Also, over time, dorsal and ventral axons tended to disappear from incorrectly chosen optic tracts. The slight bias toward choosing the appropriate optic tract or optic tract compartment may be enough to account for the topographic specificity of the regenerated retinotectal projection. Near-randomness of the axonal positions in the tracts argues against the presence of any specific guidance cues in the optic tracts of adult animals. Axonal density was highest in the correct compartment and diminished progressively with increasing distance into the incorrect compartment. Such a gradient of axonal density suggests that regenerating axons "drift" away from their previous positions in the optic pathways.
A D Springer; K D Morel; B R Wilson
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of comparative neurology     Volume:  298     ISSN:  0021-9967     ISO Abbreviation:  J. Comp. Neurol.     Publication Date:  1990 Aug 
Date Detail:
Created Date:  1990-12-04     Completed Date:  1990-12-04     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0406041     Medline TA:  J Comp Neurol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  458-71     Citation Subset:  IM    
Department of Cell Biology and Anatomy, New York Medical College, Valhalla 10595.
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MeSH Terms
Axons / ultrastructure
Goldfish / anatomy & histology*
Nerve Crush
Nerve Regeneration
Neural Pathways / cytology
Optic Nerve / cytology*,  physiology
Retinal Ganglion Cells / cytology,  physiology
Grant Support

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