Journal of Neuroscience, Vol 11, 910-917, Copyright © 1991 by Society for Neuroscience
Dendritic arbors of large-field ganglion cells show scaled growth during expansion of the goldfish retina: a study of morphometric and electrotonic properties
SA Bloomfield and PF Hitchcock
Department of Ophthalmology, New York University Medical Center, New York 10016.
The retina of the goldfish grows by a balloon-like expansion and by the
addition of new neurons at the margin. It has been proposed that as a
consequence of this expansion the dendritic arbors of ganglion cells in
central retina grow in a uniform manner without the addition of new
branches. In the present study, we have examined this proposal by comparing
the geometries of individual dendritic arbors of large-field ganglion cells
from the retinas of small/young and large/old fish. These comparisons were
based on measurements of several parameters of dendritic morphology,
including number of segments and branches, branch angles, changes in
diameter at branch points, and proximal versus distal distribution of arbor
length. In addition, we used passive, steady-state cable modeling as an
independent method of estimating the functional architectures of small and
large dendritic arbors. Our morphometric data indicate that, though they
are very different in absolute size, dendritic arbors of small and large
ganglion cells have remarkably similar architectures. Analysis with
steady-state cable equations indicates that the arbors from small and large
cells have equivalent electrotonic lengths and show comparable propagation
of synaptic currents. These data are consistent with the hypothesis that
dendritic arbors of small and large ganglion cells are scaled versions of
one another. We conclude that the growth of these cells during the
expansion of the retina is the result of the addition of dendritic mass to
an arbor whose basic geometry remains unchanged.