Journal of Neuroscience, Vol 5, 3403-3408, Copyright © 1985 by Society for Neuroscience
Density of somatic innervation on mammalian autonomic ganglion cells is inversely related to dendritic complexity and preganglionic convergence
CJ Forehand
I have studied superior cervical ganglion cells in mouse, hamster, rat,
guinea pig, and rabbit by electron microscopy to determine how the
distribution of synapses on these neurons is affected by the systematic
differences in dendritic morphology and preganglionic convergence that are
evident in the superior cervical ganglia of these species (Purves, D., and
J. W. Lichtman (1985) Science 228: 298-302). The density of dendritic
innervation is approximately the same in these animals regardless of target
cell geometry (and always greater than the density of synapses on the cell
soma); however, more complex ganglion cells, which are innervated by
commensurately more axons, receive progressively fewer cell body synapses
than geometrically simpler ganglion cells. Evidently the somatic membrane
becomes a less favorable site for synapse formation as dendritic complexity
and the number of inputs increase. This paradoxical decrease in the density
of somatic innervation as preganglionic convergence increases may reflect
competitive interactions between the axons innervating individual ganglion
cells.