Journal of Neuroscience, Vol 14, 590-598, Copyright © 1994 by Society for Neuroscience
Long-term growth and remodeling of regenerated retino-collicular connections in adult hamsters
DA Carter, GM Bray and AJ Aguayo
Centre for Research in Neuroscience, Montreal General Hospital Research Institute and McGill University, Quebec, Canada.
The capacity of regenerating axons for long-term growth and synaptic
plasticity was investigated in the visual system of adult hamsters. Four to
six and 8-10 months after the eye and the superior colliculus (SC) were
linked by a peripheral nerve (PN) graft, the retinal ganglion cell (RGC)
axons that had regrown into the SC were examined ultrastructurally.
Together with the data from hamsters with similar PN grafts for 2 months
(Carter et al., 1989), this study spans most of the life of these animals.
The overall findings indicate that (1) the RGC axons extended twice as far
into the SC and the number of RGC terminals increased 30-fold between 2 and
4-6 months. These parameters did not change thereafter. The highest density
of regenerated RGC terminals observed in the SC was 11.5% of controls. (2)
The new RGC terminals acquired most of their normal ultrastructural
characteristics by 2 months. (3) The mean size of the terminals was larger
than in controls but decreased gradually, and there was a small increase in
the size of the regenerated synapses. (4) At all times, the RGC terminals
remained confined to the layers of the SC that normally receive retinal
inputs, and their synapses were formed in normal proportions with the
dendritic shafts and spines of SC neurons. Thus, there is a protracted
long-term growth and remodeling of the RGC axons that have regenerated into
the SC of these adult mammals.(ABSTRACT TRUNCATED AT 250 WORDS)
Previous Article | Next Article
