The aim of this study was to determine whether culture-
conditioned medium (CCM) can prevent neuronal damage caused by excitotoxicity or by "chemical
ischemia" in cultured chick retina cells. Excitotoxic conditions were obtained by incubating retina cells with
glutamate or
kainate and "chemical
ischemia" was induced by metabolic inhibition. In this case, cultures were briefly exposed to
sodium cyanide, to block oxidative phosphorylation and
iodoacetic acid, to block glycolysis. The assessment of neuronal injury was made spectrophotometrically by quantification of cellularly reduced MTT. Stimulation of retina cells with
glutamate or
kainate in serum deprived culture medium (BME-FCS), lead to a decrease in the MTT metabolism that was dependent on the time of exposure to the toxic agents. CCM prevented cell damage, either when present during the stimulation period or during the recovery period. This protection was more prominent in the case of
kainate-induced neuronal death. "Chemical
ischemia" also lead to a decrease of the MTT metabolism in a time-dependent manner and CCM protected retina cells from "
ischemia"-induced lesions when present during the stimulation period and during the recovery period. The protective effect of CCM was partially decreased by the
tyrosine kinase inhibitor,
genistein, when the cells were stimulated with
kainate, but not with
glutamate, or when the cells were subjected to "chemical
ischemia". CCM protected retina cells against both the acute and the delayed toxicity induced by either
glutamate or
kainate, or by "chemical
ischemia", when present during both the insult and the recovery period. The presence of survival factors in the media may effectively inhibit the cell death signals generated by
glutamate receptor activation or by "chemical
ischemia".