TROPHIC FACTORS PRODUCED BY RETINAL CELLS INCREASE THE SURVIVAL OF RETINAL GANGLION-CELLS IN-VITRO

The naturally occurring neuron death of normal development has been sh own to depend on trophic factors produced and released by target cells . It has also been shown that the afferent supply and local interactio ns play a role in the control of this degenerative phenomenon. We stud ied the effect of trophic factors produced by intrinsic retinal cells on the survival of retinal ganglion cells in vitro. Retinae of newborn hooded rats were retrogradely labelled with horseradish peroxidase in jected into the superior colliculus to permit the identification of re tinal ganglion cells in culture. We tested the effect of conditioned m edia either from aggregates or from explants of retinal cells from neo natal rats on the survival of ganglion cells in vitro. Our results sho wed that both conditioned media increased the survival of these cells. The trophic activity was dose-dependent, was maintained after dialysi s against a 12 kDa membrane, was abolished by heating at 56-degrees-C for 30 min, and was not found in conditioned medium from cerebral cort ical explants. Conditioned medium obtained without fetal calf serum pr esented the same trophic effect. These results suggest that the local control of developmental neuron death by intrinsic retinal cells may b e mediated by neurotrophic factors.