Transsynaptic Degeneration of Retinal Ganglion Cells Following Lesions to Primary Visual Cortex in Marmosets

PURPOSE. A lesion to primary visual cortex (V1) in primates can produce retrograde transneuronal degeneration in the dorsal lateral geniculate nucleus (LGN) and retina. We investigated the effect of age at time of lesion on LGN volume and retinal ganglion cell (RGC) density in marmoset monkeys. METHODS. Retinas and LGNs were obtained about 2 years after a unilateral left-sided V1 lesion as infants (n = 7) or young adult (n = 1). Antibodies against RBPMS were used to label all RGCs, and antibodies against CaMKII or GABA_A receptors were used to label nonmidget RGCs. Cell densities were compared in the left and right hemiretina of each eye. The LGNs were stained with the nuclear marker NeuN or for Nissl substance. RESULTS. In three animals lesioned within the first 2 postnatal weeks, the proportion of RGCs lost within 5 mm of the fovea was ∼twofold higher than after lesions at 4 or 6 weeks. There was negligible loss in the animal lesioned at 2 years of age. A positive correlation between RGC loss and LGN volume reduction was evident. No loss of CaMKII-positive or GABA_A receptor-positive RGCs was apparent within 2 mm of the fovea in any of the retinas investigated. CONCLUSIONS. Susceptibility of marmoset RGCs to transneuronal degeneration is high at birth and declines over the first 6 postnatal weeks. High survival rates of CaMKII and GABA_A receptor-positive RGCs implies that widefield and parasol cells are less affected by neonatal cortical lesions than are midget-pathway cells.