Organization of the inner retina following early elimination of the retinal ganglion cell population: Effects on cell numbers and stratification patterns

The present study has examined the effects of early ganglion cell eliminati on upon the organization of the inner retina in the fel ret. The population of retinal ganglion cells was removed by optic nerve transection on the se cond postnatal day, and retinas were subsequently studied in adulthood. Num bers of amacrine and bipolar cells were compared in the nerve-transected an d nerve-intact retinas of operated ferrets, while stratification patterns w ithin the inner plexiform layer were compared in these and in normal ferret retinas. Early ganglion cell elimination was found to produce a 25% reduct ion in the population of glycine transporter-immunoreactive amacrine cells, and LX and 15% reductions in the populations of parvalbumin and calbindin- immunoreactive amacrine cells, respectively. GABAergic amacrine cells were also reduced by 34%. The number of calbindin-immunoreactive displaced amacr ine cells, by contrast, had increased in the ganglion cell-depleted retina, bring three times their normal number. Other amacrine and bipolar cell typ es were unaffected. Despite these changes, the stratification patterns asso ciated with these cell types remained largely intact within the inner plexi form layer. The present results demonstrate a class-specific dependency of inner retinal neurons upon the ganglion cell population in early postnatal life, but the ganglion cells do not appear to provide any critical signals for stratification within the inner plexiform layer, at least not after bir th. Since they themselves do not produce stratified dendritic arbors until well after birth, the signals for stratification of the bipolar and amacrin e cell processes should arise from other sources.