Journal of Neuroscience, Vol 14, 6621-6637, Copyright © 1994 by Society for Neuroscience
Targeting and activity-related dendritic modification in mammalian retinal ganglion cells
RJ Wingate and ID Thompson
University Laboratory of Physiology, Oxford University, United Kingdom.
We have studied factors that influence the development of dendritic
morphology in hamster retinal ganglion cells. By combining fluorescent
retrograde tracing with in vitro Lucifer yellow injection into fixed
retina, cells with appropriate and inappropriate visuotopic projections
have been compared. In adult hamsters, cells with an aberrant ipsilateral
projection from the nasal retina display a uniformly sparse dendritic
morphology. However, following monocular enucleation at postnatal day 0
(P0), this population displays a significantly enhanced dendritic
complexity in the adult. By contrast, removal of one eye at P6 or at P12
produces progressively less effect. These results suggest that dendritic
complement of the adult aberrant projection can be regulated by altering
the early postnatal axonal environment. The development of aberrant
ganglion cells was investigated to determine the relative influences of
cell death and dendritic remodeling in shaping the composition of the adult
aberrant population. Aberrant cells were found to be indistinguishable from
other cells in nasal retina throughout early development. After ganglion
cell death (P1-P12) is over, aberrant cells still display a full range of
cell types. However, at eye opening (P16) they undergo a rapid loss of
dendritic complexity by remodeling. By P22, aberrant cells display a
uniformly sparse dendritic morphology. When hamsters were raised in the
dark between P12 (the end of ganglion cell death) and P22, this severe
remodeling was blocked. This block was maintained when hamsters were dark
reared to P42. Hence, both dark rearing and monocular enucleation at P0
produce similar effects on the development of visuotopically inappropriate
hamster retinal ganglion cells. We speculate that the patterns of dendritic
sculpting that we have observed reflect activity- mediated modulation of
dendritic form via retrograde signals from the terminal arbors. This has
implications for retinal ganglion cell morphological classification and,
more generally, for mechanisms that influence the dendritic development of
other neurons in the CNS.
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