Atrophy and degeneration of ganglion cells in central retina following loss of postsynaptic target neurons in the dorsal lateral geniculate nucleus of the adult cat.

Selective degeneration of neurons in the dorsal lateral geniculate nucleus (dLGN) of the adult cat was produced by in situ injection of kainic acid. This rapid degeneration mimics the loss of lateral geniculate neurons seen after neonatal visual cortex ablation. Following survivals of 2, 4, or 6 months, the geniculate was injected with horseradish peroxidase (HRP) and the retinas were examined for the presence of retrogradely labeled, as well as unlabeled, cells. Total ganglion cell density in central nasal retina was not different from that of controls at 2 or 4 months, but by 6 months had decreased to 68% of control values. The proportion of cells labeled with HRP did not change at 2 months, but decreased from 84% in controls to less than 1% by 4 months, and none were labeled at 6 months. Surviving ganglion cells in central retina showed atrophy of the cell body, a finding not apparent in data from the retinal periphery. Shrinkage occurred in the few cells labeled with HRP surviving at 4 months, as well as among the unlabeled cells surviving at 4 and 6 months. These results show that the survival of central retinal ganglion cells in the cat continues to depend on intact target neurons beyond the period of development. Mature ganglion cells in central retina respond to loss of appropriate targets first by axon terminal retraction and then by atrophy and cell death. However, when compared to the response of cells located in far peripheral retina following dLGN neuron loss, central ganglion cells take longer to undergo axonal retraction and a greater proportion of the central ganglion cells, although atrophied, survive after 6 months.