Retinal ganglion cell survival requirements: a major but transient dependence on Müller glia during development

Neonatal rat retinal ganglion cells (RGC), identified by a retrograde horseradish peroxidase labelling technique, survived over a 16-h culture period when cultured on monolayers of rat Müller glia or in conditioned media derived from these cells. Maximal survival of neonatal RGC was obtained at 1:4 dilution of conditioned media. However, extensive neurite outgrowth from RGC was seen only when they were cultured on glial monolayers. Homogeneous cultures of RGC, obtained using cell sorting techniques, also survived in Müller-conditioned media. This indicates that other intrinsic cells of the retina do not mediate the effect of Müller-conditioned media on RGC. Conditioned media from Müller glia do not significantly enhance the survival of RGC from 6 day retinae. However, these older RGC are supported in culture by extracts derived from their target tissue. These results suggest that as development proceeds RGC survival is dependent on factors produced by target rather than those produced by Müller glia.