Neurotoxic and gliotoxic effects of glutamate were studied in isolated chick embryo retinas of various ages. Employing a short-term incubation system, we found that initial cellular changes in retinas from 15minus; and 21-day chick embryos were localized to glial Muuml;ller cells as previously shown in retinas from 12-day embryos. In the older retinas, however, an additional selective lesion was consistently found in the presumptive photoreceptor cells. Similar photoreceptor damage was not seen in 12-day retinas, even after treatment with relatively high glutamate doses. Autoradiographic uptake of tritiated glutamate in retinas at 12 and 14 days was localized to the glial Muuml;ller cells; in the 14-day retinas, however, there was also uptake of the labeled amino acid into the developing inner segments. Uptake of tritiated glutamate in retinas at younger (8-day) and older (21-day) ages did not show any obvious localization of the label.
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