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To assess the influence of brain immaturity on the effects of oxygen deprivation and the participation of excitotoxicity, the consequences of a 6‐h exposure to either hypoxia (95% N2/5% CO2) or 100 µM glutamate were studied in cultured fetal rat forebrain neurons taken at two maturational stages, i.e., 6 and 13 days in vitro. Cells were examined for their morphology, viability, energy metabolism reflected by 2‐d‐[3H]deoxyglucose uptake, and protein synthesis assessed by [3H]leucine incorporation. Apoptosis and necrosis were scored using the fluorescent dye 4,6‐diamidino‐2‐phenylindole. Whereas 6‐day‐old neurons responded to a 6‐h hypoxia by transient hypermetabolism, biphasic increase in protein synthesis, and cycloheximide‐sensitive apoptotic death within 72 h postexposure, glutamate did not affect cell characteristics by the same time. In 13‐day‐old neurons, hypoxia induced both apoptosis (8.2%) and necrosis (22.3%). At this age, glutamate definitely reduced energy metabolism (26%) and protein synthesis (17%) by the end of exposure. The percentage of necrotic neurons reached 40.7%, but the rate of apoptosis was unchanged compared with controls. Therefore, excitotoxicity cannot account for hypoxia‐induced injury in immature neurons, but its participation is suggested in older cells by the suppression of the necrotic component of hypoxia by glutamate receptor antagonists at 13 days.

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