Retinal ganglion cell degeneration following loss of postsynaptic target neurons in the dorsal lateral geniculate nucleus of the adult cat

Abstract

Kainic acid was used to produce selective degeneration of neurons in the dorsal lateral geniculate nucleus of the adult cat. This degeneration mimics the rapid loss of geniculate neurons seen after visual cortex ablation in the neonate. Following survivals of 2, 4, or 6 months, the geniculate was injected with horseradish peroxidase and the retinae were examined for the presence of retrogradely labeled cells. Analysis of ganglion cell density in peripheral nasal retina revealed a 58% loss of cells overall at 6 months. The proportion of cells labeled with horseradish peroxidase decreased more rapidly, until none were labeled at 6 months. Separate analysis of small, medium, and large ganglion cell populations revealed that only medium-sized cells were lost at 2 months whereas both medium and large cells were lost at 4 and 6 months. By 6 months, 92% of medium cells and 65% of large cells had degenerated. These results show that mature retinal ganglion cells in the cat maintain a dependence on target integrity for their continued survival. When the appropriate target is lost, the ganglion cells respond first by axon terminal retraction and then by cell death.